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Effect of plasma remelting on microstructure and properties of a CoCrCuNiAl0.5 high-entropy alloy prepared by spark plasma sintering |
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Mingliang Wang, Guojia Zhang, Hongzhi Cui, Yiping Lu, Yong Zhao, Na Wei & Tingju Li |
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China |
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2021 |
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https://doi.org/10.1007/s10853-020-05570-x
Journal of Materials Science volume 56, pages 5878–5898(2021) |
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A CoCrCuNiAl0.5 high-entropy alloy (HEA) was prepared by spark plasma sintering (SPS). The effect of plasma transferred arc (PTA) remelting on the microstructures and properties of the SPS-ed HEA was studied. The results showed that, after PTA remelting, the microstructures transformed from randomly-oriented equiaxed grains to dendrites with a directional solidified morphology. The coarse plate-like precipitates (~ 130 nm in diameter and ~ 20 nm in thickness) containing ordered L12 and disordered FCC structures inside the matrix grains were replaced by the disordered FCC spherical Cu-rich precipitates with several nanometers within the dendritic matrix. In the intergranular region, the size of the L12 cubic precipitates was decreased from ~ 55 nm to ~ 2 nm, and dislocations and lattice distortions were also observed. In addition, the brittle B2 phase was disappeared, and the extent of Cu segregation was decreased in the interdendritic region. The SPS-ed sample has a compressive yield strength of 913.8 MPa and a fracture strain of 21.7%. However, the PTA remelted sample exhibits a much higher fracture strain (> 70%, without fracture) and an appreciable yield strength of 739.4 MPa, which indicates an excellent balance between strength and ductility was achieved after PTA remelting. Furthermore, the corrosion resistance of the PTA remelted sample was higher than that of the SPS-ed sample, which was mainly due to the decreased elemental segregation, and the reduced sizes and types of the precipitates. |
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Cu2O/CuO heterojunction catalysts through atmospheric pressure plasma induced defect passivation |
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Avishek Dey, Gauthaman Chandrabose, Lois A.O. Damptey, E.S. Erakulan, Ranjit Thapa, Siarhei Zhuk, Goutam Kumar Dalapati, Seeram Ramakrishna, Nicholas St. J. Braithwaite, Amir Shirzadi, Satheesh Krishnamurthy |
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UK, India, Singapoore |
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https://doi.org/10.1016/j.apsusc.2020.148571
Applied Surface Science Volume 541, 1 March 2021, 148571 |
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• Fast and environment friendly route for CuO/Cu2O heterojunction synthesis.
• Epitaxial growth using atmospheric pressure plasma jet. • The heterojunction electrodes can operate without transparent current collector. • High currents and stability towards electrocatalysis and photocatalysis. |
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A novel route to fabricate Cu2O/CuO heterojunction electrodes using an atmospheric pressure plasma jet (APPJ) is demonstrated. This process promotes favourable band alignment and produces nanoscale CuO surface features from Cu2O with low density of interfacial defects. This electrode can operate without any transparent current collector, showing remarkable currents and stability towards oxygen evolution reaction (OER) (6 mA cm−2 for 2 h at pH14) as well as photocatalytic hydrogen evolution reaction (HER) activity (−1.9 mA cm−2 for 800 s at pH7). When the electrocatalytic oxygen evolution (OER) activity was measured for Cu2O/CuO electrode deposited on FTO substrate the currents increased to ~40 mA cm−2 at 0.8 V vs SCE in 1 M KOH without compensating for the electrode electrolyte surface resistance (iR correction). The composite films also exhibited a high rate towards photo degradation of Methylene Blue (MB) and phenol in the visible spectra, indicating efficient charge separation. We modelled the electronic structure of this epitaxially grown Cu2O/CuO heterojunction using density functional theory. The calculations revealed the distinctive shifts towards Fermi level of the p-band centre of O atom in Cu2O and d-band centre of Cu atom in CuO at the interface contribute towards the increased catalytic activity of the heterostructure. Another factor influencing the activity stems from the high density of excited species in the plasma introducing polar radicals at the electrode surface increasing the electrolyte coverage. This work presents the potential of APPJ functionalization to tune the surface electronic properties of copper oxide based catalysts for enhanced efficiency in OER and HER water splitting. |
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Corrosion properties of β-Ta alloyed Ti6Al4V by double-glow plasma surface alloying technique |
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Ying Liu, Bing Zhou, Hongkong Wang, Jie Gao, Yong Ma, Hongjun Hei, Yanxia Wu, Shengwang Yu |
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China |
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https://doi.org/10.1007/s10853-020-05626-y
J Mater Sci 56, 6487–6498 (2021) |
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To improve the corrosion resistance of biomedical titanium alloys, Ta-modified layer was prepared on Ti6Al4V substrate by double-glow plasma surface alloying technique (DGPSAT) at 750 °C. The effects of alloying time of Ta coating on the microstructure, film cohesion strength, as well as the electrochemical corrosion property had been investigated. Results showed that there were mainly β-Ta phase formed at 750 °C, the crystal grew bigger without phase transition and the layer thickness increases with the prolongation of alloying time. However, the cohesion strength and corrosion resistance of the film increase first and then decrease with the prolonging alloying time. In particular, the sample with alloying time of 30 min maintains the best cohesion strength and corrosion resistance. These are attributed to the following factors: a denser and more homogeneous coating with high cohesion strength formed on the substrate, higher positive Ecorr and lower Icorr in phosphate buffered saline (PBS) solution. Both of these accelerate the formation of tantalum oxides protective layers on metal surface and thus maintain the excellent properties. |
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Effect of plasma oxidation on tin-oxide active layer for thin-film transistor applications |
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Zong-Wei Shang, Qian Xu, Guan-You He, Zhi-Wei Zheng, Chun-Hu Cheng |
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China, Taiwan |
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https://doi.org/10.1007/s10853-020-05708-x
J Mater Sci 56, 6286–6291 (2021) |
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In this study, the plasma oxidation effect in tin-oxide (SnOx) thin film was investigated. And on this basis, we fabricated n-type thin-film transistors (TFTs) using the SnOx thin film with the plasma oxidation by experiments. By adjusting the processing time of the oxygen plasma treatment (OPT), the optimized SnOx TFT device exhibited an extremely high field-effect mobility of 87.6 cm2 V−1 s−1, a desirable on-to-off current ratio of 1.9 × 104 and a threshold voltage of − 0.9 V. Furthermore, we investigated the origin of the performance enhancements in the n-type SnOx TFTs with the optimized OPT by introducing the density of states (DOS) modeling in TCAD simulation. The numerical simulation indicated that the attributes of donor-like Gaussian defect states (oxygen vacancies) were modified in overall DOS due to the plasma oxidation effect. These present results show that the SnOx TFT treated by oxygen plasma has great promise in the future high-performance flat panel display industries. |
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Direct coating of copper nanoparticles on flexible substrates from copper precursors using underwater plasma and their EMI performance |
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Kangil Kim, Jin Young Huh, Yong Cheol Hong |
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Republic of Korea |
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https://doi.org/10.1016/j.mseb.2020.114995
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• Underwater plasma system for the direct coating of metal nanoparticles.
• One-pot process for synthesis and coating of nanoparticles using an underwater plasma. • Rapid and cost-effective process to fabricate EMI shielding textile. |
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The metal coated textiles and polymer films have become increasingly important in view of electromagnetic interference (EMI) shielding. In this study, we propose a simple underwater plasma system for direct coating of copper nanoparticles on textiles and polymer films to intercept electromagnetic wave. The proposed system can synthesize copper nanoparticles and coat it on substrate at once. We analyzed the characteristics of coating layer in order to optimize coating fabrication. When the copper nanoparticles were coated using optimized condition, the thickness of coating layer is about 1 μm and sheet resistance is about 95.44 mΩ/sq. The improved conductivity of polyimide film and nonwoven fabric significantly contributed to effective shielding of electromagnetic interference measured at 38.83 and 82.31 dB in frequency from 1 to 10 GHz. |
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Environmental reliability and moisture barrier properties of silicon nitride and silicon oxide films using roll-to-roll plasma enhanced chemical vapor deposition |
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Won Jae Lee, Tae-Yeon Cho, Sung-Hoon Cho, Seong-Keun Cho |
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Korea |
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https://doi.org/10.1016/j.tsf.2021.138524
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• Environmental reliability of single-layer SiNx and SiOx established.
• Flexible SiNx and SiOx investigated for durability and reliability. • SiNx performs better than SiOx as a flexible thin barrier film. • Effect of moisture and temperature on SiNx and SiOx degradation elucidated. |
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The moisture barrier properties and long-term reliability of flexible thin barrier films under harsh environmental conditions are crucial parameters to consider for the real-world applications of flexible electronics. In this study, we fabricated flexible barrier films of single-layer silicon nitride (SiNx) and silicon oxide (SiOx) on a polyethylene terephthalate substrate using plasma enhanced chemical vapor deposition. We investigated the stability and degradation mechanism of SiNx and SiOx barrier films at high temperature and under high humidity using water vapor transmission rate (WVTR) measurements and cyclic bending tests. The changes in chemical composition, film density, surface roughness, and WVTR were analyzed after environmental reliability tests. It was found that high temperature and high humidity induced oxidation of the SiNx and SiOx films, resulting in an increase in the surface roughness and decrease in the film density. The SiOx film was oxidized faster than the SiNx film and formed large hillocks on the surface. The WVTR values of both films increased as the reliability test time increased, especially under environmental conditions of 85 °C/85% relative humidity, with the barrier performance of the SiOx film degrading more than the SiNx film. The SiNx film displayed stable barrier performance during 10,000 cycles bending test at a fixed bending radius of 10 mm, even after harsh environmental reliability tests. |
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Ceramic coating on Ti-6Al-4V by plasma electrolytic oxidation in molten salt: Development and characterization |
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Alexander Sobolev, Michael Zinigrad, Konstantin Borodianskiy |
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Israel |
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https://doi.org/10.1016/j.surfcoat.2021.126847
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• TiO2 coating was developed by plasma electrolytic oxidation in nitrate salt.
• Effect of PEO current frequency on structure and performance was examined. • The highest PEO coating properties were obtained using current frequency of 150 Hz. • The highest contact angle was obtained on the most compact titanium oxide coating. • The highest corrosion resistance was obtained on the most uniform coating. |
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The plasma electrolytic oxidation (PEO) method is one of the most promising methods for the formation of oxide coatings on metallic substrates. This process is usually conducted in an aqueous solution electrolyte; however, it has several disadvantages, such as heating-up of the system and the formation of the undesired chemical components. This study addresses these disadvantages by conducting the process in a molten salt electrolyte. The surface morphology, phase composition, hydrophobicity, and the effects of process current frequency were examined. Thin titanium oxide, rutile and anatase, coating of 2–2.5 μm was formed on the treated Ti-6Al-4V alloys. The potentiodynamic polarization test evaluated the highest polarization polarization resistance for the alloy obtained using current frequency of 150 Hz which was 364×104 Ω·cm2 in comparison with the pristine alloy which was 6.93×104 Ω·cm2. Electrochemical impedance spectroscopy revealed the same behavior. Morphology evaluation revealed that the structure of this coating contained uniform sub-micron porosity and its surface exhibited the highest hydrophobicity. |
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Comparing the properties of commercially treated and air plasma treated carbon fibers |
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Racim Radjef, Karyn L. Jarvis, Bronwyn L .Fox, Sally L. McArthur |
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Australia |
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https://doi.org/10.1016/j.surfcoat.2020.126751
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• Air plasma investigated as alternative to electrolytic oxidation of carbon fibers
• Lower oxygen concentrations for air plasma treated fibers • Comparable interfacial shear strength for both treatment methods • Chemistry may have less influence on fiber-matrix adhesion than previously reported. • Results indicate current wet processing could be replaced by dry plasma treatment. |
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Carbon fibers undergo aqueous electrolytic oxidation during manufacturing to remove surface graphitic layers. Significant cost reduction and lower environmental impact could however be achieved by replacing electrolytic oxidation with a dry process, such as plasma treatment. This study demonstrates how air plasma treatment can be used as a dry surface modification process for carbon fibers, thus aiding in the understanding of the influence of surface treatment on surface chemistry, mechanical properties and fiber-matrix interactions. Greater oxygen incorporation resulted from electrolytic oxidation than air plasma treatment but had similar interfacial shear strengths, indicating that chemistry may have less of an effect on fiber-matrix adhesion than previously suggested. The removal of weakly bound surface graphitic layers and increases in surface roughness, which were achieved by both methods, appear to be the most important factors influencing fiber-matrix adhesion, thereby suggesting that dry plasma treatment could replace the current wet processing. |
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Fast and facile synthesis of carbonate-modified NiFe layered double hydroxide nanosheets by dielectric barrier discharge microplasma: mechanism and application in enhanced water oxidation |
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Zhipeng Wang, Jiahui Zhang, Qiang Wang, Xue Jiang, Ke Huang, Xiaoli Xiong |
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China |
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https://doi.org/10.1007/s10853-021-05798-1 |
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A fast and facile approach was designed to fabricate carbonate (Ci)-modified NiFe layered double hydroxide (LDH) nanosheets array on carbon cloth (CC) by dielectric barrier discharge (DBD) microplasma. The whole synthetic process can be completed within 1 h at ambient temperature and pressure. The prepared NiFe LDH-Ci/CC emerges a superior catalytic activity for oxygen evolving reaction in alkaline media, which only demands an overpotential of 240 mV at 20 mA cm−2 with a high stability for at least 90 h, and shows an excellent turnover frequency value of 0.323 mol O2 s−1 at 350 mV. Time-resolved measurements of direct emission spectra for nitrogen second positive system N2(C-B) were measured in the DBD microplasma discharge. And a high vibrational temperature (Tvib, 3100 K) and rotational temperature (Trot, 340 K) were obtained, indicating a great chemical reactivity. In addition, the intermediate products of hydroxyl radicals (·OH) were identified and the possible synthesis mechanism was tentatively proposed. |
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Characterization of surface physico-chemistry and morphology of plasma-sized carbon fiber |
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D. Gravis, S. Moisan, F. Poncin-Epaillard |
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France |
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https://doi.org/10.1016/j.tsf.2021.138555
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• Sizing of carbon fiber thanks to plasma technology
• Plasma-polymerization of apolar, polar precursors for tuning carbon fiber surface properties • Evidence of interfacial bond between coating and fiber thanks to FTIR spectroscopy |
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Carbon fiber (CF) surfaces were prepared in order to enhance their cohesion in polymer matrixes for composite applications. Among innovative methods allowing the modification of CF surface, plasma technologies, and more specifically on plasma polymerization is known as an eco-process that allows to size, i.e. to coat the CF strands with organic polymer materials. Depending on plasma parameters and chosen organic precursors, the thin film surface physico-chemistry can be tuned to enhance the plasma-processed CF surface properties. The chemical composition, as well as the effect of thin film thickness, were linked to wettability and surface free energy of the coated CFs. Among the different plasma polymers, plasma-poly(acetylene) is characterized with higher deposition rate and was the most efficient for improving the wettability of CF surface. Surface chemistry and thickness appear to be the key parameter of controlling the CF surface wettability. |
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Tribological performance assessment of Al2O3-YSZ composite coatings deposited by hybrid powder-suspension plasma spraying |
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Ashish Ganvir, Sneha Goel, Sivakumar Govindarajan, Adwait Rajeev Jahagirdar, Stefan Björklund, Uta Klement, Shrikant Joshia |
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Sweden, India |
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https://doi.org/10.1016/j.surfcoat.2021.126907
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• Hybrid powder-suspension Al2O3-YSZ CMC coatings were sprayed by axial plasma spray.
• The ball-on-plate specific wear rate of CMC coatings was decreased by 36%. • The erosion wear rate of the CMC coating was decreased up to 50%. • A mixed ductile-brittle fracture wear was noted in monolithic and CMC coatings. • However, the extent of brittle facture was dominant in the monolithic coating. |
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The advent of high-throughput plasma spray systems that allow axial feeding encourages the study of using liquid feedstock for various next-generation functional applications. The current study explores the benefit of such a plasma spray system to deposit hybrid powder-suspension Al2O3-YSZ ceramic matrix composite (CMC) coatings for tribological applications. The tribological performance of the hybrid processed CMC coatings was assessed using scratch, ball-on-plate wear and erosion tests and compared with that of monolithic powder-derived Al2O3 coatings. As-deposited and tribo-tested coatings were characterized using Scanning Electron Microscopy, X-ray Diffraction and Energy Dispersive Spectroscopy to analyse their microstructure and phase constitution. The results showed that the tribological performance of the hybrid powder-suspension Al2O3-YSZ CMC coating was significantly improved by enhancing the wear resistance under scratch, dry sliding ball-on-plate and erosion tests as compared to the conventional APS deposited monolithic Al2O3 coating. About 36% decrease in the dry sliding ball-on-plate specific wear rate and up to 50% decrease in the erosion wear rate was noted in the hybrid powder-suspension Al2O3-YSZ CMC coating as compared to the conventional APS deposited monolithic Al2O3 coating. The study concludes that the hybrid powder-suspension route can create CMC coatings with unique multi-length scale microstructures which can be attractive for combining different tribological attributes in the same coating system. |
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Inhibitory effects of hematite nanoparticles on corrosion protection function of TiO2 coating prepared by plasma electrolytic oxidation |
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Amin Hoseini, Benyamin Yarmand, Alireza Kolahi |
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Iran |
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https://doi.org/10.1016/j.surfcoat.2021.126938
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• The addition of HNPs promoted the growth rate and anatase-rutile transformation.
• The inherent defects and surface roughness reduced by HNPs incorporation. • The corrosion protection performance improved upon participating 3 g·L−1 HNPs. • The surface reactivity of coatings with aggressive ions diminished interestingly. |
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Protective oxide coatings were prepared on titanium substrates using the plasma electrolytic oxidation process, and the inhibitory role of hematite nanoparticles (HNPs) in their corrosion performance was evaluated by studying the formation and growth behavior. The results confirmed that the addition of HNPs up to a maximum amount of 3 g·L−1 to the phosphate-based electrolyte softened and stabilized the electrochemical events during titanium oxidation, resulting in an oxide layer with a more uniform microstructure, as well as less porosity and surface roughness. The participation of HNPs in the coating preparation accelerated the growth rate, promoted the anatase-rutile transformation, and reduced the inherent defects. Thus, the thermodynamic stability of the coatings in the corrosive medium improved and the dissolution kinetics of the substrate diminished. Modeling the data obtained from electrochemical impedance spectroscopy revealed that the incorporation of HNPs up to the maximum amount into the coatings increased the corrosion resistance of outer and inner parts of their bilayer microstructure by 5.18 and 9.88 times, respectively. Furthermore, Mott-Schottky analysis demonstrated that the surface reactivity of the coatings with aggressive anions diminished due to the reduction of donor concentration and more negative flat band potential, which proved the inhibiting effects of HNPs. |
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Influence of ZnO on thermal control property and corrosion resistance of plasma electrolytic oxidation coatings on Mg alloy |
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Xinyan Wang, Xiaopeng Lu, Pengfei Ju, Yan Chen, Tao Zhang, Fuhui Wang |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.126905
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• The inertly incorporated ZnO particles decrease the absorptance of the coatings.
• Coating emissivity is increased in the presence of ZnO particles. • Addition of ZnO decreases the porosity and enhances corrosion resistance of the layer. |
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Thermal control and corrosion resistant coatings have been fabricated by means of plasma electrolytic oxidation on AZ91 Mg alloy in the present study. The coatings were achieved mainly by in-situ incorporation of nano-sized ZnO particles into the porous layer and optimization of the composition of the base electrolyte. It was found that addition of ZnO nanoparticles influences the absorptance and emissivity of the coatings. The absorptance of the coating is greatly decreased by the inertly incorporated ZnO nanoparticles. This is probably due to the high band gap energy of ZnO, which can reduce the coating absorptance accordingly. The coating emissivity has been increased in the presence of particles since ZnO has high infrared emissivity value. Moreover, the corrosion resistance of PEO coatings has been improved in the presence of ZnO particles, owing to the accumulation of ZnO in the open pores and decrease of the coating porosity. |
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Dual-strengthening of steel surface and bulk via synergistic effect of plasma nitriding: A case study of M50 steel |
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Jiawei Yao, Fuyao Yan, Baofeng Chen, Ying Yang, Yueming Xu, Mufu Yan, Yanxiang Zhang |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.126910
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• Simultaneous plasma nitriding and tempering of M50 achieve high surface hardness along with secondary hardened core.
• The nitrided layer thickness is promoted by more than 60% and high hardness (>1100HV) surface layer spans a half. • The high hardness sub-surface layer is caused by the supersaturation of nitrogen induced by spinodal decomposition. • Nano-structured nitrided layer with breakdown of martensite laths is observed associated with spinodal decomposition. |
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Duplex-hardened M50 steel is used widely for jet engine shaft bearings. To reduce time and cost in duplex hardening, simultaneous plasma nitriding and tempering is performed upon as-solutioned M50 steel in this work. This heat-treating step can achieve high surface hardness and through-hardened core at the same time. Compared with the conventional “tempering + nitriding” method, the one-step heat treating method in this work can significantly increase the nitrided layer thickness by more than 61% and form a high hardness (>1000 HV0.1) layer spanning half of the total nitrided layer, which leads to reduced friction coefficient and improved wear resistance. A comprehensive study of the nitrided layer was carried out by slicing the surface along the diffusing direction. The phase distribution characters along the diffusing direction were investigated by XRD and SEM. A nitrided layer with gradient nano-structure was observed by the TEM, which experimentally explained the observed supersaturation of nitrogen in the sub-surface layer as a result of spinodal decomposition. |
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Effects of Co addition on microstructure and cavitation erosion resistance of plasma sprayed TiNi based coating |
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Xinlong Wie, Wuyan Zhu, Aolin Ban, Dejia Zhu, Chao Zhang, Hongbiao Dong |
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China, UK |
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https://doi.org/10.1016/j.surfcoat.2021.126838
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• Effects of Co addition on cavitation resistance of TiNi based coating are revealed.
• The lamellar microstructures with defects are presented in all TiNi based coatings. • Appropriate addition of Co is beneficial to reduce the porosity of all coatings. • Cavitation resistance of TiNi based coating can be significantly improved by Co addition. |
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TiNi shape memory alloy exhibits an excellent cavitation erosion resistance. Therefore, it's an effective method for preventing cavitation erosion by applying this material as a coating. In this paper, the effect of Co element addition on cavitation erosion resistance of TiNi based coating deposited by atmospheric plasma spraying (APS) was investigated. The microstructure and microhardness were characterized. The results show that the lamellar microstructures with defects, such as porosities, microcracks and unmelted particles are presented in all TiNi based coatings. The appropriate addition of Co element is beneficial to reduce the porosity of the TiNi based coating and obtain a denser microstructure. The matrix phase of the TiNi based coatings is TiNi phase. After adding Co element, TiNiCo phase is formed in the coating. Microhardness of TiNi based coatings is slightly increased after adding Co element due to the formed TiNiCo phase and the decreased porosity. All TiNi based coatings do not show the incubation period in the initial stage of cavitation. The cavitation erosion resistance of TiNi based coating can be improved by the appropriate addition of Co element due to the formed dense microstructure with low porosity. |
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Thermal shock behavior of Ba(Mg1/3Ta2/3)O3-YSZ double-ceramic-layer thermal barrier coatings prepared by atmospheric plasma spraying |
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Yupeng Cao, Xianjin Ning, Quansheng Wang |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.126842
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• BMT-YSZ (DCL) and BMT/20 wt.% YSZ-YSZ (MIXD) composite double-ceramic-layer thermal barrier coatings were prepared.
• Thermal shock behavior and failure mechanisms of DCL and MIXD coatings were analyzed. • The BMT ceramic top layer was toughened by the addition of YSZ. • Significant improvement in thermal shock performance of the MIXD coatings was achieved. |
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The Ba(Mg1/3Ta2/3)O3 (BMT) ceramic is considered a potential candidate material for thermal barrier coating (TBC) applications, due to its excellent thermophysical properties. However, the low fracture toughness and poor chemical compatibility with thermally grown oxides result in an inferior thermal shock performance of single-layer BMT coatings and greatly limit its application. In this study, BMT-yttria partially stabilized zirconia (BMT-YSZ) and BMT/20 wt% YSZ-YSZ composite double-ceramic-layer coatings were prepared by atmospheric plasma spraying, and their thermal shock behaviors were investigated in detail. The results indicate that the thermal shock performance of the BMT-YSZ coatings was significantly superior to that of single-layer BMT coatings. The spallation of the BMT-YSZ coatings was due to the stress generated by the Ba3Ta5O15 phase formed on the coating surface and the low fracture toughness of BMT. By employing the BMT/20 wt% YSZ-YSZ composite double-ceramic-layer structure, the thermal shock performance of the coatings could be further improved, because the addition of YSZ in the BMT layer effectively increased the fracture toughness of the coatings. |
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Microstructure and properties of in-situ ZrB2-ZrC composite coatings by plasma spraying |
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Yu-hang Cui, Qi Zhang, Yu-xuan Shao, Yong Yang, Yu-duo Ma, Wen-wie Sun, Yan-wie Wang, Xing-yu Wang, Yan-chun Dong |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.126846
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• Zr-B4C powder was used to prepare ZrB2-ZrC composite coating by plasma spraying.
• The formation mechanism of in-situ ZrB2-ZrC coating was solid reaction-melting-liquid reaction-deposition. • The coating by Zr-B4C powder displayed dense microstructure and fine grains. • The coating by Zr-B4C powder has better properties than that by ZrB2-ZrC powder. |
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The ZrB2-ZrC composite coating fabricated by ZrB2-ZrC powder shows low density and poor properties. To improve the quality of ZrB2-ZrC composite coating, Zr-B4C powder was used as precursor and the ZrB2-ZrC composite coating was successfully synthesized in situ on the surface of titanium alloy. The microstructure evolution and reaction mechanism of the Zr-B4C composite powder in plasma spraying process were investigated. The microstructure and properties of the ZrB2-ZrC composite coatings fabricated by ZrB2-ZrC and Zr-B4C composite powders were investigated comparatively. The results indicate that a dense and fine grain microstructure was formed in the in situ synthesized ZrB2-ZrC composite coating, and the quality and properties of the coating were improved, which is attributed to the reaction between Zr and B4C and then the improved melting degree of the powder during the plasma spraying process. |
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Wear and corrosion resistant coatings prepared on LY12 aluminum alloy by plasma electrolytic oxidation |
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Chao Yang, Jiayu Zhu, Suihan Cui, Pinghu Chen, Zhongcan Wu, Zhengyong Maa,Ricky K.Y.Fu, Xiubo Tian, Paul K.Chu, Zhongzhen Wu |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.126885
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• A new multivariate electrolyte without agglomeration or precipitation is designed.
• The coatings with high-crystallinity alumina shows excellent wear resistance. • Enough zinc phosphate of coating keeps the excellent corrosion resistance. |
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Although aluminum alloys are widely used in the aerospace industry, their relatively poor wear and corrosion resistance have hampered some applications and reduce the lifetime of the components. In this work, by using a zinc-containing phosphate electrolyte, the corrosion resistance, surface hardness, and wear resistance of the coatings produced by plasma electrolytic oxidation (PEO) are simultaneously improved. The micro-arc discharge is optimized by changing the phosphate concentration instead of introducing hard phase cations to improve the crystallinity of the zinc-doped alumina coating. Our results reveal that by using a concentration of (NaPO3)6 of 50 g/L, the hard phase of crystralline alumina and corrosive-resistant phase of Zn3(PO4)2 are produced in concert. In the salt spraying test, the lifetime of the PEO coating is over 5000 h and the electrochemical corrosion current density is reduced by about 2 orders of magnitude confirming the improved corrosion resistance and durability. Moreover, the surface hardness increases from 400 HV for the coating prepared using the conventional phosphate electrolyte to 711.8 HV and the wear rate also drops from 8.5 × 10−4 mm3·(N·m)−1 to 2.0 × 10−5 mm3·(N·m)−1. This strategy can guarantee the aluminum alloy PEO coating with simultaneous excellent wear and corrosion resistance to cope with the complex service environment. |
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Atmosphärendruckplasma dekontaminiert Hölzer |
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Sven Gerullis, Martin Fischer |
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Germany |
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Galvanotechnik 2/2021 Eugen G. Leuze Verlag S. 210 ff |
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Der Vorteil der Dekontamination von mit chlororganischen Bioziden
belasteten Holzoberfl ächen mittels Plasma liegt in der Vermeidung des Einsatzes von Lösungsmitteln, einem vollkommen trockenen Prozess und der Vermeidung mechanischer Beschädigungen. |
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Influence of double bonds and cyclic structure on the AP‐PECVD of low‐k organosilicon insulating layers |
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Dominique Abessolo Ondo, François Loyer, Nicolas D. Boscher |
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Luxembourg |
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https://doi.org/10.1002/ppap.202000222 |
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The influence of the monomer's structure on the growth mechanisms and performances of low dielectric constant insulating thin films elaborated from the atmospheric‐pressure plasma‐enhanced chemical vapour deposition reaction of
three different tetrasiloxane compounds is elucidated. The presence of vinyl bonds enables free‐radical polymerisation and surface reaction pathways, which is strongly favoured from the combination of ultrashort plasma pulses (ca. 100 ns), as polymerisation initiator, with long plasma off‐times (10ms) to yield the formation of atomically smooth thin films with excellent insulating properties (in the range of 10−7 A·cm−2). |
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Investigation of in vitro behavior of plasma sprayed Ti, TiO2 and HA coatings on PEEK |
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Fatih Sargin, Garip Erdogan, Kursat Kanbur, Ahmet Turk |
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Turkey |
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https://doi.org/10.1016/j.surfcoat.2021.126965
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• PEEK biomaterials were coated with Ti, TiO2, Ti + HA, TiO2 + HA and HA combinations by atmospheric plasma spray.
• SEM images revealed change in the surface morphology and roughness • EDX and XRD results proved the formation of various phase structures for coatings. • In vitro analysis showed that Ti + HA, TiO2 + HA and HA coatings have bioactive property. |
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Orthopedic implants are one of the most reliable and widely used equipments to increase the quality of human life by enhancing or replacing damaged body parts and ensuring the problematic parts of the body to become operative after a short time period. Polyether ether ketone (PEEK) is a semi-crystal high-performance thermoplastic polymeric implant material which emerged as an alternative for metallic implants that used in orthopedic surgery. Although PEEK has some superior properties such as high melting point, superb wear resistance, excellent fatigue behavior, non-toxicity for bone tissue and elasticity modulus similar to human bone, PEEK has some disadvantages such as biologically inert behavior and low bioactivity. In this context, coating the implant surface to improve its osteointegration behavior is widely accepted. Coating PEEK polymers with bioactive materials such as Hydroxyapatite (HA) is among one of the solutions for this problem. In this study, in order to increase surface bioactivity of PEEK biomaterials, Titanium (Ti), Titanium dioxide (TiO2) and Hydroxyapatite (HA) powder combinations was coated on PEEK samples by using Atmospheric Plasma Spray (APS) method. Morphological and chemical characterization showed produced coatings are suitable for implantation process. Also in vitro tests performed in Simulated Body Fluid (SBF) revealed that HA, Ti + HA and TiO2 + HA coatings have bioactive property. |
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Optimization of the microstructure of TiO2 photocatalytic surfaces created by Plasma Electrolytic Oxidation of titanium substrates |
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M. Coto, S.C. Troughton, P. Knight, R. Joshi, R. Francis, R.V. Kumar, T.W. Clyne |
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UK, India, Singapoore |
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https://doi.org/10.1016/j.surfcoat.2021.127000 |
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• Correlation between PEO conditions and microstructure/topology of resultant TiO2 coatings
• Demonstrated that rougher coatings lead to more effective photo-catalytic performance • Fluid dynamics modelling relates this to contact between pollutants and photoactive surfaces. |
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UV treatments are commonly employed for removal of pollutants from water in industrial environments. Introduction of a suitable photocatalyst can be beneficial in improving the energy efficiency. This commonly involves creating powerful reactive oxygen species that are able to degrade pollutants. However, the photocatalyst is required to have both high surface area (accessible to irradiation from the light source) and to be mechanically robust. TiO2 is a well-known photocatalyst, suitable for use under UV illumination. This paper concerns production of photocatalytic TiO2 via Plasma Electrolytic Oxidation (PEO) of titanium substrates. PEO of Ti commonly results in highly porous TiO2 coatings that adhere strongly to a robust metallic substrate. Characteristics of the electrical discharges, which are central to the PEO process, have been studied using high-speed photography. These results are correlated with the microstructure of the resultant coating. The photocatalytic performance has been evaluated under UV-C illumination, using urea as a model pollutant, and modelling of liquid flow over the PEO surfaces has been performed using COMSOL. Photocatalytic activity is enhanced on samples with high surface roughness and high surface area, which tend to be produced after intermediate processing times (8 min). This is explained in terms of how fluid flow is disrupted over rough surfaces, reducing the thickness of the hydrodynamic boundary layer and increasing the interaction between pollutant and catalytic surface. |
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Thermal conductivity and oxidation behavior of porous Inconel 625 coating interface prepared by dual-injection plasma spraying |
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S. Yugeswaran, P. Amarnath, P.V. Ananthapadmanabhan, L. Pershin, J. Mostaghimi, S. Chandra, T.W. Coyle |
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India, Canada |
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https://doi.org/10.1016/j.surfcoat.2021.126990
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• Reliable porous coating by dual-injection plasma spraying
• Controlled porosity in coating microstructure • Low thermally conductive porous Inconel 625 coating • Potential interface for gas transpiration film-cooling |
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Plasma sprayed Inconel 625 coating with desired microstructures and porosity can be a potential gas transpiration interface between the hot and cold fluid medium in gas turbines while cooling the components through transpiration film-cooling technique. In scope of this work, we produced porous Inconel 625 coatings by using dual injection plasma spraying. Polyester powder was used as the pore former which was separately injected during the spraying of Inconel 625 powders at optimum spraying conditions. The sprayed coatings were subjected to heat treatment to remove the polyester and to create porosity in the coatings. Feeding conditions of external pore former were optimized to obtain the coatings with desired porosity levels (4 ± 2% to 48 ± 9%). Thermal conductivity of the Inconel 625 coatings with different porosity levels (4 ± 2%; 23 ± 3% and 34 ± 5%) were measured by laser flash method and were subjected to isothermal oxidation at 950 °C for 200 h to estimate their oxidation rates. Obtained results showed that the thermal conductivity of the coatings decreased and oxidation rate increased with respect to increase in the porosity level in the coating microstructures. |
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Characterization of AlW oxide coatings on aluminum formed by pulsed direct current plasma electrolytic oxidation at ultra-low duty cycles |
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Kristina Mojsilović, Nenad Tadić, Uroš Lačnjevac, Stevan Stojadinović, Rastko Vasilić |
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Serbia |
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https://doi.org/10.1016/j.surfcoat.2021.126982
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• Oxide coatings are formed using ultra-low duty cycle pulsed direct current.
• OES revealed the presence of two types of micro-discharges. • Obtained thin oxide coatings possess rather low porosity and roughness. • WO3, W3O8 and γ-Al2O3 phases are identified in the coatings. |
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The growth of thin oxide coatings on the aluminum substrate in water-based sodium tungstate electrolyte by plasma electrolytic oxidation (PEO) is discussed and experimentally illustrated. The growth is carried out using a distinctive ultra-low duty cycle pulsed direct current (DC) power supply. During the PEO processing elements present in micro-discharges are identified using standard optical emission spectroscopy (OES) technique. The spectral line shape analysis of the first two hydrogen Balmer lines shows the presence of two types of micro-discharges. Obtained coatings are also characterized with respect to their morphology and chemical and phase composition. It is shown that coatings are composed of Al, O, and W, featuring low roughness and porosity. Partial crystallization of the coatings resulted in identification of WO3, W3O8, and γ-Al2O3 crystalline phases. |
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Corrosion resistance and tribological behavior of ZK30 magnesium alloy coated by plasma electrolytic oxidation |
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Joelda Silva Rodrigues, Leonardo Marasca Antonini, António Alexandre da Cunha Bastos, Jie Zhou, Céliade Fraga Malfatti |
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Brazil, Portugal, the Netherlands |
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https://doi.org/10.1016/j.surfcoat.2021.126983 |
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• Plasma electrolytic oxidation was used to produce a ceramic coating.
• A porous coating with greater wear resistance was formed on the surface of the ZK30 magnesium alloy. • The coating reduced the rate of hydrogen release of the ZK30 magnesium alloy. • The susceptibility to localized corrosion of the ZK30 magnesium alloy reduced with the application of the coating. |
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The rapid bio-corrosion of magnesium-based alloys, the formation of hydrogen gas and, consequently, the premature loss of biomechanical functions hinder their applications as biodegradable implant materials. The corrosion becomes even accelerated, when fretting wear occurs at implant junctions, as a result of repeated disruptions of the magnesium (hydr)oxide layer formed on implant surfaces. To improve the overall performance of these materials in a bio-relevant environment, especially corrosion resistance and wear resistance, in this research, plasma electrolytic oxidation (PEO) was applied to create a coating on a magnesium alloy, ZK30. The resulting gains in corrosion resistance and wear resistance were evaluated. In vitro immersion tests in Hank's solution at 37 °C showed a reduction in hydrogen release from the PEO-treated alloy. The results obtained from applying the scanning vibrating electrode technique (SVET) indicated a decreased susceptibility of the PEO-treated alloy to localized corrosion, accounting for the improved corrosion resistance. In addition, PEO was found to change the surface topography and roughness, in addition to surface chemistry, which contributed to an increased but stable coefficient of friction and a decreased material removal rate, as revealed by the tribological tests with a ball-on-plate configuration. The results indicate an enlarged opportunity of magnesium-based materials for orthopedic applications, where friction and wear are involved, by applying PEO. |
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Degradation of methyl orange in heterogeneous photo-Fenton reaction over V(IV)-containing oxide-phosphate coatings formed on titanium by plasma electrolytic oxidation |
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M.S. Vasilyeva, I.V. Lukiyanchuk, T.P. Yarovaya, A.Yu. Ustinov, P.M. Nedozorov, A.N. Fedorets, O.D. Arefieva |
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Russia |
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https://doi.org/10.1016/j.surfcoat.2021.126898
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• V-rich oxide phosphate coatings were formed on Ti by PEO.
• The oxidation state of vanadium in the surface layers is mainly 4 + . • When exposed to UV or Vis light, the samples are active in MO degradation. • Surface vanadium peroxide complexes determine the samples activities. |
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V-, P-containing coatings on titanium have been formed through one-step method of plasma electrolytic oxidation in aqueous electrolyte containing 0.049 mol/L Na6P6O18 and 0.095 mol/L NaVO3 (рН = 6) at different current densities and processing times. The coatings have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrum analysis (EDX), microprobe X-ray spectrum analysis (XSA), and X-ray photoelectron spectroscopy (XPS). As to XSA, all coatings are enriched with vanadium (11–16 at.%) and phosphorus (17–21 at.%), the ratio of which is constant and does not depend on the formation mode. According to XPS, vanadium is mainly found in the +4 oxidation state. The photocatalytic activity of oxide coatings has been investigated in the reaction of methyl orange (MO) degradation in the presence of H2O2 under UV or Vis irradiation. After 180 min of UV and Vis irradiation, 80% and 30% the MO dye, respectively, were degraded on almost all V-, P-containing PEO-coated samples. It has been suggested that their activity is determined by the formation of vanadium peroxide complexes fixed on the coating surface and, thereafter, of active radicals under the UV and Vis irradiation. |
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Dense and anti-corrosion thin films prepared by plasma polymerization of hexamethyldisilazane for applications in metallic implants |
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Wei-Ting Ting, Ko-Shao Chen, Meng-Jiy Wang |
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Taiwan |
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https://doi.org/10.1016/j.surfcoat.2021.126932 |
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• Dense and anti-corrosion plasma polymerized HMDSZ (ppHMDSZ) thin films coated on stainless steel (SS) by single step method.
• Correlation between the thickness of ppHMDSZ coatings and the responses of corrosion current is reported for the first time. • An accurate method to determine mass and density of thin films was conducted by using quartz crystal microbalance (QCM). |
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Plasma polymerized hexamethyldisilazane (ppHMDSZ) thin films with specific thickness and density coated on substrates (ppHMDSZ/substrate) to promote the corrosion resistance for the potential applications in metallic implants is reported in this study. Comparing with the conventional anti-corrosion thin film coatings, plasma polymerization method provided an effective, dry, and simpler process, which allowed to prepare dense thin films with the thickness of a few hundred nanometers. This study proposed that the anti-corrosion behavior could be correlated closely to the density of thin film coated on stainless steel (SS) that can be precisely controlled by the plasma deposition time. The physico-chemical properties of the as-prepared ppHMDSZ thin films were evaluated by field-emission scanning electron microscope (FE-SEM), water contact angle (WCA), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and electron spectroscopy for chemical analysis (ESCA). The corrosion resistance of the ppHMDSZ coated stainless steel (ppHMDSZ/SS) was improved by depositing ~140 nm in thickness and 1.15 g/cm3 in density which reduced 90% of the original corrosion performance against the corrosion in Hank's solution, measured by potentiodynamic polarization tests. The resultant ppHMDSZ thin film coatings allowed to protect substrates toward corrosion and can be further applied in implants for tissue engineering and biomaterials. |
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Effect of coating composition on the micro-galvanic dissolution behavior and antifouling performance of plasma-sprayed laminated-structured CuTi composite coating |
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Jia-Jia Tian, Kai Wang, Kang-Wie Xu, Xiao-Tao Luo, Guo-Sheng Shao, Chang-Jiu Li |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.126963 |
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• Plasma-sprayed laminated CuTi coatings with tunable Cu loading were prepared.
• Cu loading had little effect on the formation and mechanism of Cu/Ti galvanic cell. • Cu ions release rate and antifouling efficiency increased with increase in Cu loading. • Antifouling efficiency of 100% was achieved as Cu loading exceeded 19.2%. • The optimization strategy of CuTi antifouling coating was proposed. |
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Marine biofouling is a critical issue significantly deteriorating the service performance of marine infrastructures. Thus, development of an effective and long-lasting antifouling coating is highly desirable. Here, a laminated-structured copper-titanium (CuTi) antifouling coating was fabricated by plasma spraying of mechanically blended Cu and Ti powders. The coating was designed to enable controlled release of Cu ions from Cu/Ti micro-galvanic cells and thus to achieve effective and long-term antifouling performance. The effect of CuTi coating composition on its micro-galvanic dissolution behavior and antifouling performance was systematically investigated. The coating compositions were changed by varying Cu content from 8.1 to 65.2%. Analysis of scanning Kelvin probe force microscopy and long-term immersion test results indicated that Cu loading within CuTi coating exhibited little influence on the formation and mechanism of Cu/Ti micro-galvanic cells. However, the Cu ions release rate and antifouling duration increased with increasing Cu loading. The antifouling efficiency of CuTi coating against bacterial survival increased with the increase in the Cu loading from 8.1 to 19.2% and it reached ~100% when Cu loading exceeded 19.2%. Electrochemical test results revealed that with the variation of Cu loading, the amount of micro-galvanic cells rather than the dissolution rate of each single micro-cell played a more prominent role in deciding the total Cu dissolution rate; and consequently, the Cu ions release rate and self-polishing rate. These results may guide the advanced design of versatile CuTi antifouling coatings with environment-friendly, durable, and remarkable antifouling capability for different practical requirements in marine engineering through facilely tailoring coating composition. |
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Comparing medium pressure dielectric barrier discharge (DBD) plasmas and classic methods of surface cleaning/activation of pure Mg for biomedical applications |
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Lu Cheng, Rouba Ghobeira, Pieter Cools, Berengere Luthringer, Mahtab Asadian, Nathalie De Geyter, Zhen Liu, Keping Yan, Rino Morent |
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China, Belgium, Germany |
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https://doi.org/10.1016/j.surfcoat.2021.126934
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• Pure Mg samples are subjected to mechanical, chemical, Ar and NH3/He DBD plasma treatments.
• The comparative study is tackling the surface chemical properties, the degradation behavior and the cytocompatibility. • The surface chemical analysis is done by local XPS measurements. • The chemical treatment removes most of the organic layer but leads to excessive oxidation. • Plasma treatments are efficient in Mg cleaning, outperform in cell-surface affinity and do not alter degradation process. |
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Pure magnesium (Mg), being a lightweight biodegradable material, is increasingly attracting attention for its use in biomedical applications. However, surface contaminations arising from material machining can result in a deleterious degradation behavior thus a poor implant biocompatibility performance. Therefore, this paper represents a comparative study tackling the surface chemistry, cytocompatibility and degradation of Mg discs subjected to classical grinding and chemical treatments and to unconventional medium pressure (5 kPa) plasmas operated in Ar and NH3/He. Results reveal that both plasmas remove more than 40% of the carbonaceous contaminations while introducing surface oxygen (and nitrogen) containing functionalities. However, grinding only removes 34% of the initial surface carbon. Despite being the most efficient in eliminating the organic layer, the chemical treatment leads to an excessive surface oxidation. In vitro tests involving mesenchymal stem cells reveal that plasma-treated samples outperform their ground and chemically cleaned counterparts in terms of cell-surface affinity as more spread out cells with significantly bigger areas are detected, suggesting higher cell attachment. Moreover, plasma does not alter the degradation rate of Mg discs, thus providing a striking insight for their application in tissue engineering. Overall, one can conclude that the eco-friendly and economical sub-atmospheric plasma is an effective alternative synergistically cleaning and improving the cytocompatibility of Mg surfaces. |
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Atmospheric pressure plasma jet fabricating of porous silver electrocatalyst as a promising approach to the creation of cathode layers of low temperature solid oxide fuel cells |
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Yu-Lin Kuo, Sagung Dewi Kencana, Yi-Jun Lin |
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Taiwan |
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https://doi.org/10.1016/j.surfcoat.2020.126810 |
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• The coating process of Ag on YSZ electrolytes for LT-SOFCs via a green chemistry atmospheric pressure plasma jet.
• A gas-to-particle synthesis mechanism produces an Ag cathode with suitable porosity. • The dominate mechanism of oxygen ions transportation from Ag cathode to YSZ electrolyte is the surface pathway. |
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Silver (Ag) electrocatalysts as cathode layers for low-temperature solid oxide fuel cells (LT-SOFCs) are prepared using an atmospheric pressure plasma jet (APPJ). The material characteristics of APPJ-coated silver are observed by an X-ray diffractometer and a field-emission scanning electron microscope. The porous cathode films, composed of Ag nanoparticles coated on YSZ electrolytes are observed. The porous Ni anodic layer is also prepared via an APPJ process on the other side of the YSZ. The values of area specific resistance and conductivities of Ag|YSZ are linearly increased with increasing operating temperatures. High conductivities of 139.6 and 143.2 S/cm are obtained at 550 and 600 °C, respectively. The exchange current and power density at 600 °C are 497.9 mA/cm2 and 108.4 mW/cm2, respectively. The AC impedance shows the two oxygen pathways, surface and bulk, of Ag electrocatalysts as reflected by the responses at low and high frequencies, respectively. Furthermore, LT-SOFCs which consist of cathode|electrolyte|anode are fabricated by APPJ technology in a fast-coating process. |
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Impact of atmospheric pressure plasma treatment on surface
metallization of CFRP composites |
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L.D. Rafailović, M. Stupavska, V. Prysiazhnyi, G. Polt, O. Rohr, S. Nixon, J. Rahel |
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Austria, Czech Republic, Germany |
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https://doi.org/10.1016/j.surfcoat.2021.127046 |
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1. Woven topology of embedded carbon fibers interferes with plasma treatment
2. Several minutes of atmospheric plasma treatment is needed to achieve good adhesion of Cu 3. Nanoindentation showed uniform plating adhesion for longer plasma treatment |
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Carbon fiber reinforced composites (CFRP) were activated by atmospheric pressure plasma source to improve the performance of galvanically plated Cu layer on its surface. Plasma activation was done by use of diffuse coplanar surface barrier discharge. Owing to its fabric structure, the morphology and chemical composition of CFRP structure is inherently heterogeneous. Therefore, the attention has been paid to mutual comparison of plasma induced chemical changes and the actual performance of metalized layers at morphologically distinct areas of CFRP surface. To evaluate these performances the XPS, FTIR, determination of surface free energy, nanoindentation, SEM and scratch tests were employed. The chemical
analysis confirmed that the positive effect of plasma pre-treatment can be attributed to the introduction of the polar oxygen containing groups: -C=O and -O-C=O into the thin topmost epoxy resin areas, and –C-OH into thick inter-yarn epoxy resin areas. The results also showed that optimized plasma activation can mitigate the adhesion differences between the distinct surface structures. |
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Tailoring adaptive bioresorbable Mg-based scaffolds with directed plasma nanosynthesis for enhanced osseointegration and tunable resorption |
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Viviana M. Posada, Ana Civantos, Juan Ramírez, Patricia Fernández-Morales, Jean Paul Allain |
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Colombia, USA |
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https://doi.org/10.1016/j.apsusc.2021.149388
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• Porous AZ31 was modified at the nanoscale via directed plasma nanosynthesis (DPNS).
• Ar+ irradiation modified the nanotopography and chemistry of the outer surface. • Al segregation on porous AZ31 surfaces was dependent on the DPNS parameters. • DPNS allowed the tunability of the hydrogen release of porous AZ31. • DPNS improved the apatite formation ability in porous AZ31. |
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Directed plasma nanosynthesis (DPNS) is a plasma-based surface modification process used to provide high-fidelity bioactive and bioresorbable interfaces for Mg-based foams having an average 500-μm pore size and containing main components of Al, Zn and Ca at bal., 3.3%, 1.11%, and 0.21%, respectively. Correlations of incident particle energies of 400–700 eV and room temperature, normal and off-normal incidence angles of 0° and 60°, respectively, and high-ion fluence conditions are combined to elicit a bioreactive Mg-foam surface. H2 evolution and pH levels of irradiated and non-irradiated Mg-foams were examined and correlated to the DPNS parameters. In situ X-ray photoelectron spectroscopy and focused ion-beam results have shown that energies of ~ 400–700 eV can control surface topography and composition, which, in turn, controls the foam-corrosion mechanism. Samples are immersed in Dulbecco’s modified eagle media, and a synergistic reaction is found in which the irradiated samples enhance the formation of calcium–phosphate (CaP) phases to CaP ratios close to the hydroxylapatite phase that enhances bone-tissue regeneration. These results lead to a surface modification strategy that adjusts the interaction of the material and the environment without using a coating that could affect the geometry and the bulk properties of the porous material. |
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Surface characterization and resistance changes of silver-nanowire networks upon atmospheric plasma treatment |
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Lewis O. Akinsinde, Tomke E. Glier, Matthias Schwartzkopf, Marie Betker, Matz Nissen, Maximilian Witte, Sarah Scheitz, Christian Nweze, Benjamin Grimm-Lebsanft, Marc Gensch, Andrei Chumakov, Ivan Baev, Ulrich Schürmann, Torben Dankwort, Frank Fischer, Michael Martins, Stephan V. Roth, Lorenz Kienle, Michael Rübhausen |
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Germany, Sweden |
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https://doi.org/10.1016/j.apsusc.2021.149362
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• Controlled etching of silver nanowire networks and tuning of its resistance by atmospheric plasma.
• Investigation of network changes by photoelectron spectroscopy and real time X-ray scattering. • Monte Carlo resistance simulation using electron tunneling in line with experimental results. |
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Highly conductive silver-nanowire (Ag-NW) networks are used in composite materials as conductive channels. Their resistance tuning can be accomplished by changing the Ag-NW concentration, and, therefore, changing the network structure. In this study, an alternative pathway to resistance engineering of conductive Ag-NW networks by local atmospheric plasma treatment is employed. The corresponding changes in nanowire network morphology and crystallinity as a function of plasma etching time are investigated by time-resolved grazing-incidence X-ray scattering, field-effect scanning electron microscopy, and X-ray photoelectron spectroscopy. Three characteristic etching phases are identified. The first two phases enable the controlled engineering of the electrical properties with different rates of resistance change, which results from changes in nanowire shape, network morphology, and different oxidation rates. Phase III is characterized by pronounced fragmentation and destruction of the Ag-NW networks. These results show the feasibility of atmospheric plasma treatments to tune the local electrical properties of conductive Ag-NW networks. Furthermore, we present a physical Monte Carlo model explaining the electrical network properties as a function of plasma etching time based on the network connectivity and a constant plasma etching rate of 570 ng s−1 cm−2. |
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Plasma sprayed Lanthanum zirconate coating over additively manufactured carbon nanotube reinforced Ni-based Composite: Unique performance of thermal barrier coating system without bondcoat |
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Sumit Choudhary, Aminul Islam, Biswajyoti Mukherjee, Julia Richter, Tizian Arold, Thomas Niendorf, Anup Kumar Keshri |
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India, Germany |
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https://doi.org/10.1016/j.apsusc.2021.149397
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• Thermal barrier coating system was fabrictaed without the bond coating.
• NiCrAlY-1 wt% CNT substrates was synthesized by selective laser melting technique. • Lanthanum zirconate coating was deposited on top of SLM processed substrate. • CNT increased the H and E by 1.6 and 2.7 times of the SLM processed substrates. • TGO layer drastically reduced at 1800 °C in LZ coated NiCrAlY-1 wt% CNT substrates. |
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For advanced thermal barrier coating (TBC) system in a modern aero and land based engine, there is pressing needs to impede the uncontrolled growth of thermally grown oxide (TGO) layers as well as the weight reduction of overall TBC system. To address both the issues, present study introduces a ‘bondcoat less’ TBC. Selective laser melting (SLM) technique has been used to fabricate two different substrates of composition NiCrAlY and NiCrAlY + 1 wt% carbon nanotube (CNT). Lanthanum zirconate (LZ) coating was deposited over the prepared substrate by plasma spraying technique. SLM processed NiCrAlY + 1 wt% CNT substrate showed the relatively higher increase in hardness and elastic modulus by 1.6 and 2.7 times, respectively. Top coat LZ coating and reinforced CNTs in NiCrAlY significantly suppressed the growth of the TGO layer at 1800 °C. It is shown that a fine microstructure, absence of pores in the coating and addition of CNTs in conjunction prevent the diffusion of the reactive species Al, Cr, Y from the NiCrAlY substrate towards the coating interface. Further, LZ coating despotised over NiCrAlY + 1 wt% CNT substrate was intact even after 48 cycles during the thermal shock resistance performed at 1800 °C. |
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Handbook of Modern Coating Technologies
6 - Flame pyrolysis—a cost-effective approach for depositing thin functional coatings at atmospheric pressure |
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I. Zunke, B.S.M. Kretzschmar, A. Heft, J. Schmidt, A. Schimanski, B. Grünler |
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Germany |
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https://doi.org/10.1016/B978-0-444-63240-1.00006-1
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Most optical, electrical, mechanical, or biological active thin films are deposited using the well-known and established vacuum-based physical vapor deposition and chemical vapor deposition methods. The deposition of thin functional layers under atmospheric pressure conditions is an attractive alternative for especially large-area coatings. In recent years many different methods have been established for various applications. Particularly the flame-based techniques offer a cost-effective solution. The basic principles of the flame-based deposition techniques are reviewed and the technical realization is shown by means of selected examples of the current research and developments. The formation of silicone oxide layers with a wide range of properties is investigated in detail. Applications such as adhesion promotion, optical effective, and barrier layers are reviewed. The deposition of transparent conductive zinc oxide is investigated. Further thin films like photocatalytic active TiO2, electrochromic WOx, and elemental silver are also introduced. |
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The rapid and large-scale production of carbon quantum dots and their integration with polymers |
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Xiang-Yun Du, Cai-Feng Wang, Guan Wu, Su Chen |
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China |
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https://doi.org/10.1002/ange.202004109 |
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Carbon quantum dots (CDs) have inspired vast interests due to their prominent photoluminescence (PL) performances and promising applications in optoelectronic, biomedical and sensing fields. Notably, the development of effective approaches for largescale CDs production may greatly promote the further advancement of their practical applications. In this review, the newly emerging methods for the large-scale production of CDs are summarized, such as microwave, ultrasonic, plasma, magnetic hyperthermia and microfluidic technology. Then, we introduce the available strategies for constructing CDs/polymer composites with intriguing solid-state PL. Particularly, the multiple roles of CDs are emphatically presented,
including fillers, monomers and initiators. Moreover, the typical applications of CDs/polymer composites in light-emitting diodes, fluorescent printing and biomedicine are outlined. Finally, we discuss their current problems and speculate on their future development. |
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Fabrication of γ-TiAl intermetallic alloy using the twin-wire plasma arc additive manufacturing process: Microstructure evolution and mechanical properties |
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Lin Wang, Yuelong Zhang, Xueming Hua, Chen Shen, Fang Li, Ye Huang, Yuhan Ding |
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China |
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https://doi.org/10.1016/j.msea.2021.141056
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Due to the intrinsic high room temperature brittleness and cold-cracking susceptibility, the fabrication and forming of γ-TiAl intermetallic alloy component is extremely difficult. Therefore, in recent years, a wire-arc additive manufacturing (WAAM) technique has been developed to fabricate the γ-TiAl intermetallic alloy by depositing the Ti and Al wires into a single tungsten arc generated molten pool with specific wire feed ratios. However, the WAAM fabricated γ-TiAl intermetallic alloy has been found having inhomogeneous layer-by-layer microstructure and the excessive heat input of tungsten arc would induce significant residual stress in the bulk sample. In the present paper, the previous WAAM has been further upgraded and an innovative twin-wire plasma arc additive manufacturing (TW-PAAM) process has been developed. Afterwards, a γ-TiAl intermetallic alloy wall component with specific chemical composition of Ti-48Al has been fabricated and the metallography, phase composition and tensile properties are characterized subsequently. It has been found that a significantly more uniform microstructure is obtained in the TW-PAAM fabricated γ-TiAl intermetallic alloy than the previous WAAM technique. The content of α2 phase, lamellar colony size and lamellar spacing exhibited the tendency of decreasing from the lower to upper part along building direction. And the tensile strength and ductility of the lower section are lower than the middle and top sections. In general, the present TW-PAAM technique has shown promising capability of fabricating γ-TiAl intermetallic alloy with lower cost, and the investigation results would become a valuable reference for understanding the evolution mechanism of microstructure and mechanical properties of the additively manufactured TiAl alloy. |
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Microstructure and mechanical properties of in situ TiC/Ti composites with a laminated structure synthesized by spark plasma sintering |
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Chengxin Lei, Yan Du, Ming Zhu, Wangtu Huo, Hao Wub, Yusheng Zhang |
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China |
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https://doi.org/10.1016/j.msea.2021.141136
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• Laminated TiC/Ti composites were synthesized by spark plasma sintering.
• The composites exhibited better strength-ductility combination. • The strengthening mechanisms are discussed and quantitatively evaluated. |
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A series of novel in situ TiC/Ti composites with laminated microstructure have been fabricated via electrophoretic deposition followed by spark plasma sintering (SPS), in which the electrophoretic deposition has been used to deposit graphene oxides (GOs) on commercially pure Ti foils and the SPS has been used to induce in situ reaction between Ti and GOs to form TiC and simultaneously achieve densification. With increasing deposition duration, the volume fraction of TiC reinforcement increases and the grain size of Ti matrix decreases in the as-sintered composites, resulting in continuous strength increment. Attributed to the introduction of TiC reinforcement and laminated structure, a strength increment of 93.9% can be reached with a considerable elongation of 6.1%. Moreover, different strengthening mechanisms are discussed and quantitatively evaluated based on microscopy analysis. |
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Positive and negative streamer propagation in volume dielectric barrier discharges with planar and porous electrodes |
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Quan‐Zhi Zhang, Li Zhang, De‐Zheng Yang, Julian Schulze, You‐Nian Wang, Annemie Bogaerts |
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China, Belgium, Germany |
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https://doi.org/10.1002/ppap.202000234 |
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The spatiotemporal dynamics of volume and surface positive and negative streamers in a pin‐to‐plate volume dielectric barrier discharge is investigated in this study. The discharge characteristics are found to be completely different for positive and negative streamers. First, the spatial propagation of a positive streamer is found to rely on electron avalanches caused by photoelectrons in front of the streamer head, whereas this is not the case for negative streamers. Second, our simulations reveal an interesting phenomenon of floating positive surface discharges, which develop when a positive streamer reaches a dielectric wall and which explain the experimentally observed branching characteristics. Third, we report for the first time, the interactions between a positive streamer and dielectric pores, in which both the pore diameter and depth affect the evolution of a positive streamer. |
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Catalyst‐enhanced plasma oxidation of n‐butane over α‐MnO2 in a temperature‐controlled twin surface dielectric barrier discharge reactor |
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Niklas Peters, Lars Schücke, Kevin Ollegott, Christian Oberste‐Beulmann, Peter Awakowicz, Martin Muhler |
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Germany |
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https://doi.org/10.1002/ppap.202000127 |
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A twin surface dielectric barrier discharge is used for the catalyst‐enhanced plasma oxidation of 300 ppm n‐butane in synthetic air. Plasma‐only operation results in the conversion of n‐butane into CO and CO2. Conversion is improved
by increasing the temperature of the feed gas, but selectivity shifts to undesired CO. α‐MnO2 is used as a catalyst deposited on the electrodes by spray coating with a distance of 1.5mm between the uncoated grid lines and the square catalyst patches to prevent the inhibition of plasma ignition. The catalyst strongly influences selectivity, reaching 40% conversion and 73% selectivity to CO2 at a specific energy density of 390 J·L−1 and 140°C, which is far below the onset temperature of thermocatalytic n‐butane conversion. |
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Plasma deposition of a stable SiOx‐like layer on copper surface for enhanced pool boiling heat transfer performance: A combination of microstructures and wetting properties |
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Hamid R. Mohammadi, Hamed Taghvaei, Ataollah Rabiee |
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Iran |
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https://doi.org/10.1002/ppap.202000209 |
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In this study, a thin film composed of inorganic SiOx is deposited on the copper surface by atmospheric pressure plasma‐enhanced chemical vapor deposition. A pool boiling experiment is performed and the influence of the coating on pool boiling performance is examined. Morphology, composition, and wettability of the thin films are assessed using a scanning electron microscope, energy‐dispersive X‐ray spectrometer, and contact angle measurements. In addition to the enhancement of pool boiling thermal characteristics, especially a 103% increase in heat transfer coefficient, it is observed that the plasma‐deposited thin film on the copper surface is stable after the four boiling/cooling cycles. Finally, the underlying mechanism behind the improvements achieved by use of coated surface is studied. |
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Atmospheric‐pressure plasma actuators: Enhancement of the free charges' transport mechanism |
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Anna Chiara Ricchiuto, Carlo Angelo Borghi, Andrea Cristofolini, Gabriele Neretti |
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Italy |
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https://doi.org/10.1002/ppap.202000214 |
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Charge particles can increase the biocidal efficacy of nonthermal plasmas in indirect treatments. The aim of this study is to increase the amount of free charges produced and delivered by a surface dielectric barrier discharge fluid‐dynamics actuator. Different linear actuators and supplying conditions have been considered. Actuators were utilized to produce an ionic wind impinging an insulating target surface. Charged particles' distribution over the target was measured with and without a metallic mesh between the actuator and target itself. Linear actuators have proven to be more effective in charge delivery with respect to an annular one previously studied by our research team. A two‐dimensional electrostatic finite‐element analysis has been carried out to get a better insight into this physical behavior. |
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Identification of key neutral species in atmospheric‐pressure plasma for promoting proliferation of fibroblast cells |
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Yuki Hori, Naoyuki Iwata, Vladislav Gamaleev, Jun‐Seok Oh, Tomiyasu Murata, Masaru Hori, Masafumi Ito |
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Japan |
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https://doi.org/10.1002/ppap.202000225 |
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To identify the key neutral species from atmospheric‐pressure plasma for promoting the proliferation of fibroblast cells, an atmospheric‐pressure radical generator was employed. A cell viability assay showed that the proliferation of fibroblasts was significantly promoted through radical treatment, resulting in the highest promotion ratio of 24%. The densities of the neutral radicals supplied by the radical generator were measured via mass spectrometry at atmospheric pressure. To determine an effective factor for the promotion, the dose dependencies of these radicals on the promotion ratio were investigated. The promotion ratio exhibited a strong correlation only with the NO• dose. These results confirmed that NO• is a direct trigger of plasma‐enhanced cell proliferation. |
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Cold Atmospheric Pressure Plasma as a Tool to Control the Proliferation of Various Mammalian Cells Including Human Mesenchymal Stem Cells for Regenerative Medicin |
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Jeongyeon Park, Kiwon Song |
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Republic of Korea |
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Plasma Medicine, 10(4):203 – 216 (2020) |
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Cell proliferation is one of the most critical processes for development, tissue regeneration, and wound healing, and is tightly linked with cell differentiation and migration. Also, the regulation of cell proliferation is essential for appropriate tissue regeneration and improved culture system, which requires an effective control tool for cell proliferation both in vivo and in vitro. Recently, cold atmospheric pressure plasma (CAP) has been shown to have considerable effects on cell proliferation that have been attributed to the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Many studies on CAP application suggest that CAP can be developed as an efficient tool to activate proliferation in vitro for personalized cell therapies and in vivo for wound healing. In this review, we discuss how CAP has been applied to control proliferation in various mammalian cells and its molecular mechanisms for biomedical applications. In our study, we demonstrated that nitric oxide (NO) from CAP is the major factor for activating the proliferation of human mesenchymal stem cells. When exposed to CAP, many different types of human cells displayed highly increased expression of cytokines and growth factors both in vitro and in vivo, strongly suggesting that common mechanisms and components are involved in CAPinduced cell proliferation. Furthermore, CAP induced epigenetic modifications in human mesenchymal stem cells to boost the expression of cytokines and growth factors, thereby promoting cell proliferation. Further studies are needed to verify that NO of the CAP and epigenetic modifications are the common mechanism of action of CAP in culture and in wounded tissues. In addition, the molecular mechanism of the epigenetic modifications induced by CAP treatment should be investigated to develop CAP as an applicable tool for regenerative medicine and wound healing. |
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From Precancers to Skin Rejuvenation—A Review of the Wide Spectrum of Current Applications and Future Possibilities for Plasma Dermatology |
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Peter C. Friedman |
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USA |
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Plasma Medicine, 10(4):217 – 232 (2020) |
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Cold plasma medicine is a quickly evolving field with great laboratory research backing and expanding clinical use. Because of the easy accessibility of skin, dermatology is uniquely positioned to be at the forefront of exploring new areas for plasma treatment. Dermatologists are already using cold plasma for ulcers and conducting trials to treat precancerous keratoses, warts, nail fungus, and acne. Based on our understanding of cold plasma principles, numerous other skin conditions may become the targets of successful cold plasma therapies. In this article, we review the concepts behind current dermatological uses of cold plasma, challenges specific to dermatology, and the possible future of expanding cold plasma use to treat skin diseases.
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Analyzing the Possible Action Mechanisms of Atmospheric Pressure Nonthermal Plasma upon Melanoma Cells |
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Jorge Humberto Serment-Guerrero, Alexa Adrian-Aguilar, Régulo López-Callejas, Rosendo Peña-Eguiluz |
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Mexico |
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Plasma Medicine, 10(4):233 – 242 (2020) |
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Cancer refers to a group of diseases characterized by an uncontrolled growth of aberrant cells as a consequence of multiple genetic alterations; melanoma is considered the most dangerous of all types of skin cancer due to its capability to produce metastasis and chemo or radioresistance. Recently, several studies point to atmospheric pressure nonthermal plasma (APNTP) as a good alternative for cancer treatment. The effect of APNTP upon cells has been largely attributed to the generation of reactive oxygen and nitrogen species that act upon biomolecules; however, there are some other factors that could contribute to the full effect on cells or tissues. The main objective of the present work is to contribute to the understanding of the action mechanisms of nonthermal plasma upon cancer cells. For this work, B16 murine melanoma and 3T3 murine fibroblasts cells were used, as well as human lymphocytes. B16 and 3T3 cells were grown in MEM with 10% FBS at 37°C and 5% CO2 atmosphere, while human lymphocytes were separated from total blood by using the Ficoll Hypaque technique. Cells were resuspended in HBSS, distributed in a 96-microwell plate, and exposed to APNTP. To evaluate the possible membrane disruption, cells were counted before and immediately after plasma exposure considering that, if the membrane was crashed, they could not be seen under the microscope. The presence of intracellular oxygen species was determined by fluorescence microscopy using the dihydrorhodamine/ethidium bromide test. The effect of UV-B component of plasma upon DNA was evaluated by a modified microelectropheresis (Comet) assay. The results indicate that the number of cells considerably decreased due to membrane disruption; also, the presence of ROS was confirmed in the cytoplasm of treated cells, as well as DNA damage generated by the UV-B fraction of APNTP, which in turn could be a factor triggering apoptosis. |
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Cold Atmospheric Helium Plasma Induces Apoptosis by Increasing Intracellular Reactive Oxygen and Nitrogen Species |
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Latha Ramireddy, Chih Ho Lai, Bih Show Low, Chuan Li, Jang Hsing Hsieh, Jyh Wei Lee, Hui Yu Wu |
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Taiwan |
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Plasma Medicine, 10(4):243 – 257 (2020)
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Cold atmospheric pressure plasma (CAPP) has been proposed as a novel method for anticancer therapy. This field gained much interest in the last decade, with biological applications such as wound healing, bacterial sterilization, and cancer treatment. However, the mechanism at the basis of plasma-cell interaction remains unclear. Here, we studied the effect of helium (He) gas CAPP on oral squamous cell carcinoma (OSCC) in vitro. CAPP treatment was performed under different treatment time conditions: 1, 3, and 5 min. Results showed that CAPP treatment induces cell death in OSCC cells in a dose-dependent manner. He-CAPP also induces cell death and G1 cell cycle arrest associated with the ATM/P53 pathway. Furthermore, CAPP activates the mitochondria-mediated apoptosis pathway by enhancing Bax expression and of the Bcl-2 protein suppression. Hydrogen peroxide (H2O2) generation increased immediately after He plasma treatment but reached basal level after 3 h. Further studies showed that CAPP increases intracellular ROS and RNS and reverts after a long period of plasma treatment. Taken together, these results indicated that He-CAPP induces cell death and cell cycle arrest and activates mitochondria-mediated apoptosis by increasing intracellular reactive oxygen and nitrogen species (ROS and RNS) in OSCC cells. Our study provides deep understanding of He-CAPP’s effect on OSCC cells. We suggest that CAPP could be a potential therapeutic and clinical research tool for oral cancer treatment. |
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Plasma Jet Effectiveness Alteration in Acute Wound Healing by Binahong (Anredera cordifolia) Extract |
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S. Darmawati, N. Nasruddin, P. Kurniasiwi, A. H. Mukaromah, A. Iswara, G.S.A. Putri, H.S.E. Rahayu, E.S. Wahyuningtyas, H. Lutfiyati, A Kartikadewi, S. Rejeki, T. Ishijima, T. Nakatani, J. Sugama |
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Indonesia, Japan |
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Plasma Medicine, 10(4):259 – 271 (2020) |
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An atmospheric pressure plasma jet (APPJ) using medical-grade argon gas as the carrier gas was developed and used to investigate wound healing in small animals combined with Binahong (Anredera cordifolia) leaf extract treatment. The experiment was divided into 4 treatment groups, control (C), plasma jet (P), Binahong leaf extract (B), and Binahong leaf extract followed by plasma jet (PB). Plasma jet treatment for wounds was applied in different styles based on the treatment day. Both P and PB treatments were contact-style for days 0–4 (5-mm distance for 1-min duration) and noncontact style for days 5–13 (20 mm for 3 min). The total period of wound observation was 14 days. Histological evaluation using hematoxylin-eosin (HE) staining was performed on days 7, 11, and 14 to evaluate wound reepithelialization. Meanwhile, the number of neutrophil cells was counted using a hematology analyzer on days 11 and 14, and malondialdehyde (MDA) levels were examined on days 7 and 14. This research revealed that plasma jet successfully improved wound healing; on the other hand, plasma jet treatment preceded by Binahong leaf extract treatment tended to impede wound healing. It is hypothesized that Binahong may reduce plasma jet effectiveness in wound healing. |
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Wettability and in-vitro study of titanium surface profiling prepared by electrolytic plasma processing |
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Wisanu Boonrawd, Kamal R. Awad, Venu Varanasi, Efstathios I. Meletis |
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USA |
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https://doi.org/10.1016/j.surfcoat.2021.127119
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• Electrolytic plasma processing produced a desirable hills and valleys surface morphology.
• Surface roughness increased linearly with increasing treatment time. • Processing for 150 s produced a superwetting surface with a 5° contact angle. • Surface profile by electrolytic plasma processing can enhance bioactivity of Ti. • Stoichiometric hydroxyapatite formed on treated Ti after 21 days immersion in α-MEM. |
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Electrolytic plasma processing (EPP) was used to create hydrophilic surface profiles on titanium. The wettability, surface morphology characteristics and chemical composition of the treated samples were studied as a function of EPP processing parameters. The EPP profiled surfaces comprised of a characteristic “hills and valleys” morphology because of continuous surface melting and freezing cycles. A bimodal surface profile was produced with 2–3 μm height hills and valleys with nano-roughness (≤200 nm). The produced profile resulted in a significant contact angle decrease (from 38.7° to 5.4°). Ratios of actual surface area to projection area (r) and fraction of solid surface remaining dry (φ) were obtained from profilometry. The surface characteristics and large r values produced by EPP were able to induce hemi-wicking. Hence, EPP produced superhydrophilic surfaces on Ti. The bioactivity of EPP treated Ti was evaluated using cell free and MC3T3 cells in-vitro studies. The treated Ti surface significantly increased the bioactivity and formed stoichiometric hydroxyapatite after immersion in a bone cell culture medium for 21 days. Cells' attachment and proliferation studies indicated that EPP treated surface significantly enhances the cells' adhesion and growth after 24 and 48 h compared to the untreated surface. The results show that Ti surface profiling by EPP constitutes a promising method to potentially improve bone implant bonding. |
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Plasma assisted ammonia combustion: Simultaneous NOx reduction and flame enhancement |
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Jinhoon Choe, Wenting Sun, Timothy Ombrello, Campbell Carter |
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USA |
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https://doi.org/10.1016/j.combustflame.2021.02.016
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This work reports that plasma can simultaneously reduce NOx emission and extend the lean blowoff limits of ammonia flames. The results show dramatic differences from similar work using hydrocarbon fuels in which plasma promoted NOx emission. Therefore, this work could lay the foundation of plasma application in practical ammonia combustion. |
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Plasma electrolytic oxidation of Ti-6Al-4V alloys in nHA/GNS containing electrolytes for biomedical applications: The combined effect of the deposition frequency and GNS weight percentage |
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Oktay Yigit, Burak Dikici, Niyazi Ozdemir, Ersin Arslan |
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Turkey |
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https://doi.org/10.1016/j.surfcoat.2021.127139
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• The TiO2-nHA/GNS coatings have been deposited on Ti6Al4V by PEO method, successfully.
• GNS addition affected pore formation, size and homogeneity. • The in-vitro corrosion resistance of Ti6Al4V increased with higher GNS ratio. • GNS addition improved surface hardness and decreased of micro cracks on ceramic basic coatings. • High pore number, small pore size and in-vitro resistant have been observed in nHA/1.5GNS coating |
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In this study, nano-hydroxyapatite (nHA) based coatings reinforced with graphene nanosheets (GNS) were successfully synthesized on Ti6Al4V alloys using AC-plasma electrolytic oxidation (PEO) technique. The PEO treatments were carried out at 1000, 1500, and 2000 Hz frequencies in different GNS containing electrolytes (free, 1.0, and 1.5 wt%). The combined effect of the deposition frequency and GNS weight percentage on the morphological and crystallographic properties of the coatings was investigated by SEM, AFM, XRD, EDS, and FT-IR analysis. The in-vitro corrosion susceptibilities of the coatings were compared by using the potentiodynamic scanning (PDS) technique in simulated body fluid (SBF) at body temperature. Besides, surface hydrophilicity and microhardness measurements were made on the coatings. The characterization of the coatings confirmed that GNS was successfully deposited in nHA-matrix with a porous and rough structure. Coating thickness and hardness increased with increasing GNS weight percentage in the coating layers and deposition frequency. A bone-like apatite formation was also observed on the surfaces after electrochemical tests in SBF. The results revealed that bioactive and hard coatings can be obtained by PEO in nHA/GNS baths. |
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Effect of plasma nitriding temperature on microstructure and wear properties of electroless nickel-boron coatings |
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R. Tima, F. Mahboubi |
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Iran |
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https://doi.org/10.1016/j.surfcoat.2021.127084
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• Plasma nitriding could be used as an alternative to conventional heat treatment of electroless nickel boron coatings.
• Plasma nitrided electroless nickel boron coatings exhibited higher hardness and wear resistance in comparison with heat treated ones. • Plasma nitriding suppressed the nickel boron grain growth during post-deposition treatment due to interaction of Nitrogen atoms with the coating. • Plasma nitriding of electroless nickel boron coatings caused precipitation of lubricant hexagonal boron nitride |
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This study investigates the effects of plasma nitriding (PN) temperature on the microstructural properties and wear behavior of electroless nickel‑boron (ENB) coatings. To this end, the ENB coatings are deposited on the mild steel substrates and submitted to PN treatment at 350, 400, and 450 °C. The Morphology, roughness, microstructure, microhardness and wear resistance of the coatings are evaluated and compared to the conventional heat-treated ENB coatings. The results indicate that a crystalline structure has appeared in the as-deposited amorphous ENB coatings through PN treatment, leading to enhancement of their hardness. The highest hardness value (1406 HV0.1) and consequently the highest wear resistance are obtained for the PN-treated ENB coating at 350 °C. These results could be assigned to the grain growth suppression achieved by doping nitrogen atoms into the coating through PN treatment. Moreover, the precipitation of the lubricant h-BN phase during PN treatment of the ENB coatings has decreases the coefficient of friction in the sliding wear test. |
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Laminar plasma jet surface hardening of P20 mold steel: Analysis on the wear and corrosion behaviors |
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Da Guo, Deping Yu, Peng Zhang, Wenjie Song, Bin Zhang, Keming Peng |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127129
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• Laminar plasma jet surface hardening was employed on P20 mold steel.
• Higher surface hardness and uniformly distributed Cr were obtained. • Microstructure transformation mechanism was clarified by temperature simulation. • LPJ treated P20 mold steel has superior wear and corrosion resistance |
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Insight into the effects of the laminar plasma jet (LPJ) surface hardening on the wear and corrosion behaviors of P20 mold steel is critical for seeking an effective way to improve the service life of the injection mold. In this study, the LPJ treatment was conducted on the surface of commercial P20 mold steel. Numerical simulation for the temperature field of the workpiece surface was employed to analyze the transformation mechanism of the microstructure. According to the numerical simulation results, the formation of a hardened layer with the lath-martensite microstructure was attributed to the ultra-fast cooling rate. Alteration in the wear and corrosion behaviors were investigated in detail by a series of ball-on-disk tribological tests and electrochemical corrosion tests. The results showed that the average coefficient of friction for the treated sample decreased from 0.314 to 0.186, and the wear rate decreased from 0.323 × 10−4 to 0.141 × 10−4 mm3/N·m. In addition, the wear mechanism of the surface of the P20 mold steel changed from abrasive wear combined with adhesive wear to mild oxidative wear after LPJ treatment. Improvement of the wear resistance was mainly attributed to the formation of lath-martensite with high hardness. Besides, it was found that the corrosion rate for the treated sample decreased from 0.2427 to 0.0680 mm/year. This was mainly attributed to the generation of the compact lath-martensite structure and the homogeneously distributed Cr element after LPJ treatment. These findings provide the theoretical feasibility for applying the LPJ surface hardening to the P20 mold steel to elevate the service life of the injection mold. |
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On the mechanisms of surface microdischarge plasma treatment of onychomycosis: Penetration, uptake, and chemical reactions |
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Zilan Xiong, Renjie Huang, Yu Zhu, Kang Luo, Mengqi Li, Zhenping Zou, Rui Han |
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China |
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https://doi.org/10.1002/ppap.202000204 |
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Despite becoming increasingly established as a treatment technique, the mechanism underlying the plasma treatment of onychomycosis has yet to be elucidated. Here, we focus on the interactions between the nail plate and a surface microdischarge plasma, including penetration, uptake, and chemical reactions. Results show that long‐lived gaseous species from plasma can penetrate the nail plate effectively and are primarily responsible for the instantaneous antionychomycosis effect. The amount of uptake far exceeded that of penetration. Attenuated total reflection‐Fourier‐transform infrared spectroscopy and X‐ray photoelectron spectroscopy results show that antimicrobial compounds form on the nail surface. Combined with the uptake of active species in the nail plate, these antimicrobial compounds may inhibit microorganism growth, thereby promoting long‐term protection against onychomycosis. |
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Nitrogen‐containing organic products from the treatment of liquid toluene with plasma‐activated N2 gas |
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Hamideh Hosseini, Mubbshir Saleem, Ester Marotta, Cristina Paradisi |
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Italy, Iran |
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https://doi.org/10.1002/ppap.202100012 |
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This proof‐of‐principle study explored the possibility to form nitrogen‐containing organic products via exposure of liquid toluene to a flow of molecular nitrogen, at room temperature and atmospheric pressure, activated by dielectric barrier discharges. N‐containing organic compounds indeed formed under these conditions, including benzonitrile, a high‐value chemical that is industrially synthesized from toluene under demanding conditions. Toluene‐derived higher hydrocarbons, as well as oxygen‐containing derivatives, were also detected, the latter due to efficient reactions of residual oxygen in the system. A mechanistic description of the observed chemistry is provided, together with guidelines for increasing the selectivity for C–N forming reactions and the development of this approach into a novel synthetic approach for high‐value organic N‐containing chemicals. |
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Glycolytic inhibitor induces metabolic crisis in solid cancer cells to enhance cold plasma‐induced cell death |
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Nagendra K. Kaushik, Neha Kaushik, Pradeep Bhartiya, Linh N. Nguyen, Eun H. Choi |
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Republic of Korea |
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https://doi.org/10.1002/ppap.202000187 |
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Targeting metabolic regulation in cancer cells through metabolic reprogramming is of interest among researchers with regard to preferential cancer cell killing. Evidence indicates that the combination of metabolic modifiers with anticancer therapies attains the expected therapeutic efficiency, suggesting a potential for selective cancer cell death. Here, we have shown that the use of 2‐deoxy‐d‐glucose, a metabolic modifier, enhances the efficiency of air gas plasma treatment at lower doses, resulting in cellular energy loss, which can be attributed to metabolic energy crisis in mitochondria. Interestingly, this novel approach is selective for solid cancer cells over normal cells, thus displaying great potential for increasing nonthermal plasma activity. |
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Preparation and characterization of PCL‐grafted zein film via atmospheric‐pressure cold plasma pretreatment |
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Shuang Dong, Xiao‐yu Li, Peng Guo, Ye Chen, Hong‐jun Li |
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China |
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https://doi.org/10.1002/ppap.202000242 |
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To improve the water resistance property of zein film, polycaprolactone (PCL) was grafted on the zein film after atmospheric‐pressure cold plasma (ACP) pretreatment. The grafting yields of PCL ranging from 15.91% ± 0.67% to 28.95% ± 0.79% were remarkably enhanced than the untreated one (12.15% ± 0.57%; p < . 05), which indicated that ACP modification could effectively improve the grafting ability of the zein film. Fourier‐transform infrared spectrum and X‐ray diffraction patterns revealed that PCL layer had been successfully grafted and the lateral α‐helix packing was susceptible to plasma treatment. Findings from this study indicated that ACP pretreatment was an effective modification approach in zein‐based polymers for packaging application. |
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Study of the anticancer effects of a helium plasma jet combined with four anticancer drugs on 3D bladder tumour spheroids |
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Jishen Zhang, Bing Li, Shengduo Xu, Dingxin Liu, Hao Zhang, Dehui Xu, Li Guo, Michael G. Kong |
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China, USA |
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https://doi.org/10.1002/ppap.202000226 |
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Current studies of cold atmospheric plasma cancer therapy mainly focus on the application of plasma alone and neglect the application of plasma combined with traditional therapeutic techniques. In this paper, the anticancer effects of a plasma jet combined with four clinical anticancer drugs (cisplatin, methotrexate, adriamycin and paclitaxel) on three‐dimensional bladder tumour spheroids (T24 cells) were studied. The results show that all four drugs had little impact on the liquid‐phase oxidative pressure induced by the plasma jet, and anticancer effects from strong to weak were as follows: Plasma jet + paclitaxel, plasma jet + adriamycin, plasma jet + cisplatin, plasma jet and plasma jet + methotrexate. Our research indicates that plasma exhibits selectivity in combination with particular anticancer drugs. |
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Elaboration and characterisation of plasma sprayed alumina coatings on nickel with nickel oxide interlayer |
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S. Valette, R. Bernardie, J. Absi, P. Lefort |
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France |
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https://doi.org/10.1016/j.surfcoat.2021.127159
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• The coating adhesion of Al2O3 on Ni is strongly improved by pre-oxidizing Ni.
• The adhesions values are of 8 MPa for polished Ni and 48.5 MPa for sandblasted Ni. • The adhesion reaches 105 MPa for pre-oxidized Ni, then alumina-coated by APS. • At the interface, NiO is a buffer zone that adapts the Ni and γ-Al2O3 lattices. |
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A process implying the pre-oxidation of nickel substrates was proposed alternatively to the usual Atmospheric Plasma Spraying (APS) of alumina on sandblasted substrates. This process comprised two steps, the substrate pre-oxidation (instead of the sandblasting of the substrate) followed by APS. The pre-oxidation formed a thin layer of the NiO oxide, 0.7–3.5 μm thick, which entirely covered the nickel substrate. During APS, the deposit did not react with NiO due to the very high cooling rate of the alumina splats at the surface of the substrates. The characterisation of the interfacial zone showed the crystallographic continuity of the different lattices, from the nickel substrate (f.c.c.) to the NiO interlayer (f.c.c.) and to the monoclinic γ-Al2O3 coating. The NiO interlayer played the role of a buffer zone that adapted the crystal lattices of the three phases. The adhesion of the coatings was determined according to the ASTM C633 test modified by reducing the contact area substrate/coating, in order to quantify the adhesion of strongly-linked coatings. The coating adhesion reached 105 MPa for the pre-oxidized samples when NiO was 1.8 μm thick, instead of 48.5 MPa for the sandblasted samples and only 8 MPa for the simply polished nickel. |
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Effects of post-annealing on microstructure and mechanical properties of plasma sprayed Ti-Si-C composite coatings with Al addition |
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Liping Zhao, Fanyong Zhang, Liangquan Wang, Shu Yan, Jining He, Fuxing Yin |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127164
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In this study, Ti-Si-C composite coatings were fabricated by plasma spraying using Ti/SiC/C/Al powder mixtures, and then these coatings were annealed at 500–900 °C in an Ar atmosphere. The influences of post-annealing on the microstructure and mechanical properties were analyzed via X-ray diffraction (XRD), scanning electron microscope (SEM) and micro-hardness tester. Results showed that the annealing treatment hardly changed the phase structure of the composite coatings. Coatings before and after annealing were composed of Ti5Si3, Ti3SiC2 and TiC phases. Compared with coatings without annealing, the peak intensity of Ti3SiC2 increased, the porosities decreased and the microstructure became more uniform after annealing. The composite coatings showed an increased microhardness and fracture toughness, which reached the maximum value of 1232 HV0.2 and 3.19 MPa·m1/2 when annealed at 700 °C. The improvement of mechanical properties was mainly attributed to the more uniform microstructure and the toughening effect of closed micro-cracks. |
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Boride-based ultra-high temperature ceramic coatings deposited via controlled atmosphere plasma spray |
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B.A. Kahl, C.C. Berndt ,A.S.M. Ang |
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Australia |
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https://doi.org/10.1016/j.surfcoat.2021.127128
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• Controlled Atmosphere Plasma Spray (CAPS) achieved a 46% reduction in oxide inclusions and 40% reduction in elemental oxygen.
• CAPS deposited zirconium boride coating exhibited less variation in hardness. • Hafnium boride coating exhibited heterogenous microstructure that was attributed to pre-processing of the feedstock. |
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This study investigates the capability of a custom-built controlled atmosphere plasma spray (CAPS) system for deposition of zirconium boride (ZrB2) and hafnium boride (HfB2) thermal protection system (TPS) coatings. Due to poor oxidation resistance these materials must be deposited in the absence of oxygen to avoid high inclusions of oxides that detrimentally effect TPS coating properties. A low cost, simple CAPS system was developed to allow for the deposition of these coatings within an inert atmosphere, in a typical lab environment. The CAPS system has demonstrated a 46% reduction in oxide inclusions for ZrB2 coatings with a 40% reduction in elemental oxygen and facilitated the deposition of a HfB2 coating with low oxide inclusions. Weibull analysis on the variability in the hardness of ZrB2 samples revealed a tri-modal distribution of hardness that was attributed to regions of differing oxide inclusions. The CAPS deposition of HfB2 did not achieve a deposited microstructure that was considered effective as a TPS. A Weibull analysis of the hardness of the HfB2 coating demonstrated a bi-modal distribution that corresponded to low oxide regions and locations composed of a similar mix of boride and monoclinic oxide. The heterogeneous microstructure was attributed to the pre-processing of the HfB2 powder. |
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Different concepts for creating antibacterial yet biocompatible surfaces: Adding bactericidal element, grafting therapeutic agent through COOH plasma polymer and their combination |
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Elizaveta S. Permyakova, Anton M. Manakhov, Philipp V. Kiryukhantsev-Korneev, Alexander N. Sheveyko, Kristina Y. Gudz, Andrey M. Kovalskii, Josef Polčak, Irina Y. Zhitnyak, Natalia A. Gloushankova, Ivan A. Dyatlov, Sergei G. Ignatov, Sergey Ershov, Dmitry V. Shtansky |
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Russia, Czech Republic, Luxembourg |
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https://doi.org/10.1016/j.apsusc.2021.149751
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• Antibacterial yet biocompatible nanosurfaces prepared.
• The presence of immobilized drugs confirmed by XPS depth profiling and FTIR. • Silver ions affected layer stability and accelerated release of drugs. |
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Antibacterial coatings have become a rapidly developing field of research, strongly stimulated by the increasing urgency of identifying alternatives to the traditional administration of antibiotics. Such coatings can be deposited onto implants and other medical devices and prevent the inflammations caused by hospital-acquired infections. Nevertheless, the design of antibacterial yet biocompatible and bioactive surfaces is a challenge that biological community has faced for many years but the “materials of dream” have not yet been developed. In this work, the biocompatible yet antibacterial multi-layered films were prepared by a combination of magnetron sputtering (TiCaPCON film), ion implantation (Ag-doped TiCaPCON film), plasma polymerization (COOH layer), and the final immobilization of gentamicin (GM) and heparin (Hepa) molecules. The layer chemistry was thoroughly investigated by means of FTIR and X-ray photoelectron spectroscopies. It was found that the immobilization of therapeutic components occurs throughout the entire thickness of the plasma-deposited COOH layer. The influence of each type of bactericide (Ag+ ions, GM, and Hepa) on antibacterial activity and cell proliferation was analyzed. Our films were cytocompatible and demonstrated superior bactericidal efficiency toward antibiotic-resistant bacterial E. coli K261 strain. Increased toxicity while using the combination of Ag nanoparticles and COOH plasma polymer is discussed. |
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Instantaneous vapor-liquid-solid growth of amorphous SiO2 nanowires within a local-equilibrium plasma and the optimized lithiation/delithiation activity |
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Wenfei Yang, Xue Zhan, Feirong Huang, Zhongyuan Zhang, Javid Muhammad, Xiyang Li, Zhiguo Rong, Xiane Guo, Youngguan Jung, Xinglong Dong |
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China, South Korea |
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https://doi.org/10.1016/j.apsusc.2021.149848
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• Random Ni@a.-SiO2 NWs are synthesized through an instantaneous VLS growth.
• The energy state of working arc plasma are diagnosed by real-time OES. • Ni@NiO@a.-SiO2 NWs is obtained by controlling Ni to convert to Ni@NiO in air. • Optimal Ni@NiO@SiO2 a.-NWs exhibit better cycling stability and rate capability. |
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Amorphous SiO2 (a.-SiO2) species is a promising anode material for lithium ion batteries (LIBs) due to its high theoretical capacity (1965 mAh g−1) and abundant resource. One-dimensional a.-SiO2 nanowires (NWs) can provide efficient pathways for charge transport/diffusion and fast strain release during reciprocating lithiation/delithiation. Herein, an instantaneous vapor–liquid-solid (VLS) growth of a.-SiO2 NWs was performed in a high-temperature DC arc plasma using metal Ni as the catalyst. The Ni@a.-SiO2 NWs contain a high content of Ni (26.68 wt%) at the tips of NWs, allowing the synthesis of two derived products of Ni@NiO@a.-SiO2 NWs and NiO@a.-SiO2 NWs via an oxidation treatment in flowing air. A real-time optical emission spectroscopy (OES) diagnosis was carried out on the working arc plasma. This indicates the electron temperature (Te) of 8088.3 K and electron density (ne) of 1.7 × 1014 cm−3 within the local-equilibrium plasma. Electrochemical properties of typical products show the optimization available by control of the core-shell structure attached at the tip of nanowire. In other words, the Ni@NiO@a.-SiO2 NWs exhibited a higher specific capacity of up to 996.8 mAh g−1 after 200 cycles with Coulombic efficiency of 99.5%, and a better rate capability at an intense current of 2.0 A·g−1. |
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Ca-based sealing of plasma electrolytic oxidation coatings on AZ91 Mg alloy |
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Xiaopeng Lu, Jirui Ma, Marta Mohedano, Borja Pillado, Raúl Arrabal, Kun Qian, Yan Li, Tao Zhang, Fuhui Wang |
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China, Spain |
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https://doi.org/10.1016/j.surfcoat.2021.127220
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• The corrosion resistance of PEO coatings was enhanced by facile sealing treatment.
• Ca containing precipitate was deposited on the coating surface. • The existence of SDS provides hydrophobicity and inhibition effect for the coating. • Increased hydrophobicity has negative influence on the paint adhesion of the coating. |
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Plasma electrolytic oxidation (PEO) coatings on AZ91 Mg alloy were sealed in calcium nitrate solutions at different pH values (3, 4 and 5). Sodium dodecyl sulfate (SDS) was added to study the effect of SDS on the corrosion resistance of the sealed coatings. The microstructure, chemical composition and corrosion resistance of the coatings were investigated by means of SEM, XPS, XRD and electrochemical corrosion tests. The corrosion performance of the coatings was improved due to precipitation of Ca-containing precipitate. Low pH and SDS addition enhanced hydroxyapatite precipitation and produced hydrophobic coatings with worse paint adhesion but better corrosion resistance. |
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In vitro bioactivity and antibacterial performances of atmospheric plasma sprayed c-axis preferential oriented hydroxyapatite coatings |
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Xiaomei Liu, Dingyong He, Zheng Zhou, Xingye Guo, Yi Liu, Wenjia Hou, Hua Li |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127209
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• HA coatings with c-axis crystalline orientation were produced by atmospheric plasma spraying.
• HA coating with c-axis crystalline orientation is effective to promote the proliferation of osteoblasts cells. • The c-axis oriented HA coating provides beneficial effects on the antibacterial activity. |
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Atmospheric plasma spraying (APS) is widely used in the fabrication of hydroxyapatite (HA) coating due to the advantages of low-cost, simple operation and it can be used to fabricate coatings with controllable structure. Despite all these advantages, the application of APS deposited HA coating for long-term use is limited by its low crystallinity, low phase purity and poor antibacterial property efficiency. Herein, HA coatings with high crystallinity, phase purity and c-axis crystalline orientation were fabricated by APS. In vitro cell, culture testing suggested that the c-axis oriented HA coating was more effective to promote the proliferation of osteoblasts cells compared with other coatings. The antibacterial activity of HA coating against the bacteria indicated that the c-axis oriented HA coating restrained the bacterial adhesion, and the antibacterial effect of the E. coli bacteria was more pronounced than that of the S. epidermidis bacteria. This study suggests that the HA coatings with the specific c-axis crystalline orientation are available for their potential applications for orthopedic and dental implantation. |
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Wear performance and osteogenic differentiation behavior of plasma electrolytic oxidation coatings on Ti-6Al-4V alloys: Potential application for bone tissue repairs |
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Pedro Bell Santos, Estela K. Baldin, Daniel A. Krieger, Victor Velhode Castro, Cesar Aguzzoli, José Carlos Fonseca, Miguel Rodrigues, Maria Ascensão Lopes, Célia de Fraga Malfatti |
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Brazil, Portugal, the Netherlands |
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https://doi.org/10.1016/j.surfcoat.2021.127179
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• PEO coatings were constituted by rutile and anatase phases.
• Ti-PEO200V showed superior wear resistance compared to that Ti-PEO300V. • Wear resistance was compromised by the formation of cracks in the Ti-PEO300V. • Ti-PEO200V sample showed better behavior with MSCs compared to the Ti6Al4V. |
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Plasma electrolytic oxidation (PEO) can be used to obtain oxide coatings able to improve the biocompatibility, wear and corrosion properties of metal implants, due to complex morphology and the formation of oxides with the possibility of incorporating bioactive elements. This study aims at producing coatings on Ti-6Al-4V alloys with potential application for bone tissue repairs, evaluating cytocompatibility behavior and the potential for osteogenic differentiation, by using mesenchymal stem cells. Coatings have been produced on Ti6Al4V alloys by PEO with a calcium and phosphate-based electrolyte, by applying the potentials of 200 V (Ti-PEO200V) and 300 V (Ti-PEO300V), with a pulsed electrical regime. The SEM/FEG characterization shown that the samples obtained are typically porous, have different thicknesses and roughness, which were found to be dependent on the maximum applied voltage. The bioactive elements (Ca and P) were incorporated into the coatings and their concentrations grew with the maximum applied voltage, as indicated by RBS analysis. In addition, the same analysis indicated that the coatings were mainly composed of Ti oxides. XRD patterns confirmed that the coatings consist mainly of titanium oxides in the rutile and anatase phases. The tribological properties were evaluated by a ball-on-plate tribometer. Both samples show very similar tribological behavior. The wear resistance of Ti-PEO300V was more impaired by the microcracks present in its morphology and its great surface roughness than the Ti-PEO200V sample. Biological properties were assessed by studying the cytocompatibility with MSC cells. The coating obtained for the Ti-PEO200V sample showed a great cytocompatibility level and initial adhesion, as well as an innate ability for osteo-differentiation of MSCs, displaying considerable potential for usage as bone-repair applications. |
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In-flight particle states and coating properties of air plasma sprayed ytterbium disilicates |
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Dianying Chen, Robert Harmon, Gopal Dwivedi, Chris Dambra, Mitch Dorfman |
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USA |
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https://doi.org/10.1016/j.surfcoat.2021.127186
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• Effects of plasma enthalpy on the in-flight particle behavior, phase composition, and properties of APS Yb2Si2O7 coatings were investigated.
• Higher plasma enthalpy caused higher in-flight particle temperature and more Yb2SiO5 phase content in the APS Yb2Si2O7 coatings. • Steam thermal cycling lives of EBCs decrease with the increase of Yb2SiO5 phase content. • The predominant EBC failure mechanisms are due to TGO growth as well as the stresses induced by CTE mismatch. • CMAS tests showed that the recession rate decreases with the increase of Yb2SiO5 phase content in APS Yb2Si2O7 coatings. |
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The effects of processing parameters on the in-flight particle behavior, phase composition, and properties of air plasma sprayed ytterbium disilicate (Yb2Si2O7) coatings were investigated in this study. With the increase in plasma enthalpy, in-flight particle temperature increases. Higher particle temperature caused an increase in silica (SiO2) evaporation from the Yb2Si2O7 particles and, as a result, additional Yb2SiO5 phase appears in the Yb2Si2O7 coating. Thermal expansion tests showed the coating containing a higher volume of Yb2SiO5 phase has a larger coefficient of thermal expansion (CTE). Thermal cycling tests in a steam environment indicated that the Yb2SiO5 phase content in the APS Yb2Si2O7 coatings has a significant effect on the EBC's durability. Thermal cycling lives decrease with the increase of Yb2SiO5 phase content in APS Yb2Si2O7 coatings. Analysis of the failed coatings indicated that the predominant EBC failure mechanisms are due to growth of the thermally growth oxides (TGO) as well as the stresses induced by CTE mismatch. Furthermore, Calcium–magnesium–alumina-silicate (CMAS) corrosion tests showed that the recession rate decreases with the increase of Yb2SiO5 phase content in APS Yb2Si2O7 coatings. |
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Advances of microwave plasma-enhanced chemical vapor deposition in fabrication of carbon nanotubes: a review |
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Yanjing Liu, Jiawei He, Nan Zhang, Wencong Zhang, Yanping Zhou, Kama Huang |
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China |
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https://doi.org/10.1007/s10853-021-06128-1 |
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Microwave plasma chemical vapor deposition (MPCVD) has received tremendous research interest in fabrication of carbon nanotubes (CNTs) due to its unique advantages of high reactivity, rapid heating, no pollution, good controllability, etc. It would be meaningful to summarize the efforts that have been devoted in this area. Up to now, no such review has been seen in the literature. In this review, a summarization and discussion of the MPCVD devices applied in CNTs fabrication are firstly given, followed by the discussion on effect and affecting mechanisms of H2 plasma pretreatment, nitrogen atoms in the reacting gases and microwave power. Notably, the parameters of as-synthesized CNTs products and the corresponding synthesizing MPCVD conditions are listed out. Finally, the capabilities of MPCVD in facilitating atmospheric-pressure, low-temperature and in situ growth of CNTs are reviewed. This review can give a comprehensive grasp of current progress and understanding of MPCVD in preparation of CNTs and may provide a useful guidance for readers to design their fabricating systems to obtained required CNTs using MPCVD. |
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Dynamically oleophobic epoxy coating with surface enriched in silicone |
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Yang Wang, Yong Fan, Ping Zhang, Limei Tian, Jianing Xu, Shichao Niu, Luquan Ren,
Jie Zhao, Weihua Ming |
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China, USA |
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https://doi.org/10.1016/j.porgcoat.2021.106170 |
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• The smooth coatings display extremely low oil contact angle hysteresis.
• This dynamical oleophobicity of the coating stems from surface-enriched PDMS • The coating can be easily applied to a variety of substrates without sacrificing interfactial adhesion. • The coating can endure continuous acid/alkali immersion, heating or UV irradiation. |
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We successfully prepared a dynamically oleophobic epoxy coating with low contact angle hysteresis (≤ 5.2°) for different low surface-tension liquids. Due to significant enrichment of covalently bonded polydimethylsiloxane (PDMS) at the coating surface, the obtained coating displays remarkable repellency against various low surface-tension liquids, including hexadecane, dodecane, decane, and soybean oil, as well as anti-smudge property and strong interfacial adhesion towards various substrates. Moreover, these excellent surface/interfacial properties have demonstrated to be very robust after being subjected to different environments (low pH, high pH, heating, and UV exposure). This type of coating may find promising applications in a broad range of fields where oil repellency is desired. |
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Low temperature open-air plasma deposition of amorphous tin oxide for perovskite solar cells |
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Oliver Zhao, Yichuan Ding, Dali Cheng, Jinbao Zhang, Florian Hilt, Nicholas Rolston, Guochen Jiang, Reinhold H. Dauskardt |
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USA |
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https://doi.org/10.1016/j.tsf.2021.138708
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• SnOx chemical composition is finely tuned by plasma deposition parameters.
• Highly transparent and low electrical resistivity 13.3 Ω*m amorphous SnOx film. • Demonstration of SnOx as an electron transport layer in perovskite solar cells. • Scalable open-air plasma deposition of a 100 cm2 SnOx thin film. |
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A low-temperature, open-air plasma process to deposit amorphous SnOx thin films as an electron-transport layer in a planar-heterojunction n−i−p perovskite solar cell is reported. Open-air plasma processing is a scalable, low capital expenditure technique capable of manufacturing-scale production without enclosures or vacuum pumps. The technique provides flexibility to tune SnOx film composition and properties by adjusting several easily accessible processing parameters. In this study, we demonstrate large area SnOx thin film deposition on substrates up to 100 cm2. The SnOx films are deposited using monobutyltin trichloride as the chemical precursor and formed without any post-annealing, which has the potential for lowering costs as an in-line process. The film exhibits low surface roughness, excellent optical transmission of greater than 90 % across the visible regime, and low electrical resistivity of 13.3 Ω*m, which is multiple orders of magnitude lower than previously reported values of amorphous SnO2 thin films. The film is then incorporated into a planar perovskite solar cell with a power conversion efficiency of 11.8 %. These factors suggest that open-air plasma-deposited SnOx thin films can potentially be compatible with low-cost and large-scale fabrication of organohalide lead perovskite solar cells and modules. |
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Assessment of plasma sprayed carbon nanotube reinforced Al2O3-based nanocomposite with micro-scratching |
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Ariharan S, Rita Maurya |
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India |
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https://doi.org/10.1016/j.surfcoat.2021.127216
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• Efficient Al2O3-based TBCs with improved (~97%) scratch resistance.
• CNT declines (49–56%) the scratch toughness, endorses there is no contribution. • Poor bonding of CNT with matrix leads to low critical load of failure and work of adhesion. • Failure in the coatings were improved by the CNT bridging and pull-out mechanism. |
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An efficient Al2O3-based nanocomposite coating was developed to fabricate the top thermally insulative layer of the thermal barrier coatings (TBCs). Here, Al2O3-based coatings were prepared by atmospheric plasma spraying and the scratch properties were investigated using progressive-load scratching. Scratch mechanism and the role of carbon nanotube (CNT), 3 and 8 mol% Y2O3 stabilized ZrO2 (3YSZ and 8YSZ, respectively) during progressive load scratching were analysed. The investigations revealed that the Al2O3-based nanocomposite coatings were showed a high scratch coefficient (0.165–0.219) compared to that of monolithic Al2O3 (0.128). Also, the monolithic Al2O3 coating showed a decent scratch resistance (0.35 mm3N−1 m−1) compared to 3YSZ/8YSZ and CNT reinforced nanocomposite (0.49–69 mm3N−1 m−1). It was attributed to the synergistic effect of hardness, fracture toughness and the bonding of the reinforcement with the matrix Al2O3. The work of adhesion of lamella in the YSZ and CNT reinforced nanocomposite was measured as 1.16–2.75 × 103 J, which is lower (up to 2.5 times) than the monolithic Al2O3 (2.91 × 103 J). It is attributed to the poor bonding of CNTs with the lamella contains Al2O3 and YSZ. Further, the failure of the nanocomposite coatings, such as flaking and chipping were resisted by CNT. Nevertheless, CNT addition declines the scratch toughness of the nanocomposite coatings (1.05–2.04 MPa.m0.5). It endorses no effective contribution of CNT in the scratch toughness of the coatings. Meanwhile, the mere addition of 8YSZ and 3YSZ in the Al2O3 matrix showed an increment (10.5% and 67.5%, respectively) in the scratch toughness compared to that of monolithic Al2O3 (2.37 MPa.m0.5) coating. |
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Effect of high-enthalpy atmospheric plasma spraying parameters on the mechanical and wear resistant properties of alumina ceramic coatings |
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Xian-Yu Jiang, Jing Hu, Shao-Liang Jiang, Xin Wang, Lin-Bo Zhang, Qi Li, Hai-Peng Lu, Liang-Jun Yin, Jian-Liang Xie, Long-Jiang Deng |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127193
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• Alumina coatings were prepared by high-enthalpy atmospheric plasma spraying.
• Studies on microstructure, porosity, phase composition, adhesion, microhardness and wear resistance • Porosity is crucial for improving mechanical properties and wear resistance. |
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Over the past decade, alumina ceramic coatings have become promising candidates for anti-wear and anti-corrosion applications owing to their excellent mechanical properties, such as chemical inertness and high temperature resistance, high hardness, and high abrasion resistance. In this work, alumina ceramic coatings are prepared via high-enthalpy atmospheric plasma spraying. The effect of plasma spraying parameters should be paid to attention, such as spraying power, powder feeding rate, and initial substrate temperature, on the mechanical and wear characteristics of the obtained coatings. According to the results, the increase in the plasma spraying power allows one to substantially reduce the porosity of coatings and in turn improves the wear resistance. The use of the higher powder feeding rates enables one to achieve the lower density and adhesion of coatings, which is due to the rising amount of unmolten particles. Finally, an increase in the initial substrate temperature reduces to a large extent the defects of the coating by decreasing the quenching stress, which enhances their mechanical properties. A decrease in the porosity of the coating is beneficial to improve the wear resistance. |
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Pulsed laser remelting supersonic plasma sprayed Cr3C2-NiCr coatings for regulating microstructure, hardness and corrosion properties |
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Kai Chong, Yong Zou, Dongting Wu, Yingwen Tang, Yongang Zhang |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127258
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• The supersonic plasma sprayed Cr3C2-NiCr coating was remelted by the pulsed-laser.
• The remelted Cr3C2-NiCr coating was featured of Cr7C3 and Ni-crystal phases. • Marangoni flow induced regular carbide morphology with uniform distribution. • Microhardness and corrosion resistance of remelted Cr3C2-NiCr coatings were improved. |
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Supersonic atmosphere plasma sprayed Cr3C2-NiCr coatings have been gradually used for protecting industrial components from the severe wear and corrosion attack. In this study, the pulsed laser technique was applied to remelt the deposited Cr3C2-NiCr coatings. The evolution in microstructure and corrosion resistance between the as-sprayed coating and pulsed laser remelted coating was carefully investigated. It is found that desirable metallurgical bonding was achieved between the pulsed laser processed coating and the substrate. After pulsed laser remelting treatment, the metastable phase disappeared and the coating was composed of equilibrium phases of Cr7C3 and Ni-crystal. Interestingly, the morphology of the newly formed carbides became regular and the high-speed Marangoni flow inside the molten pool facilitated their homogeneous distribution. Overall, the porosity decreased from 4.3% of the as-sprayed coating to 1.1% of the laser-treated coating while the carbide volume fraction increased from 49% to 70%. Due to that the coating microstructure became more homogeneous and denser after pulsed laser remelting, the hardness and corrosion resistance were greatly improved. |
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Tuning Ta coating properties through chemical and plasma etching pre-treatment of NiTi wire substrates |
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Ben Pace, Avi Bendavid, Mohammed Ahsan, Matthew Dargusch, Vijay Bhatia, Jacob Byrnes, Julie Cairney |
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Australia |
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https://doi.org/10.1016/j.surfcoat.2021.127214
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• Bulk <111> texturing in Tantalum coatings with etched substrates
• Plasma etching introduces ß-Ta into the majority α-Ta film matrix. • Σ3 CSL boundary density substantially regulated by pretreatment method • More uniform and columnar grains in Ta film under chemical etching • Different film microstructures produced with similar adhesive strength |
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Tantalum coatings have wide applications including as corrosion resistant coatings and radiopaque films for biomedical implants. However, producing coatings of sufficient thickness with the desired mechanical properties remains a substantial challenge. In this study, we show that the microstructure and properties of thick Ta films deposited on NiTi wires can be controlled significantly by pre-treating the substrate surface via ultrasonication followed by Aqua Regia etchant, or by plasma-based etching alone, while maintaining overall adhesive strength. Films from plasma and chemically etched samples exhibited substantially greater bulk texturing in the <111> direction than the control film, also yielding more elongated and columnar grains. The extent of <111> texturing in each sample was reflected in differences in Σ3 CSL boundary density. Additionally, only plasma etching yielded a β-Ta secondary phase. These microstructural observations demonstrate that film phase composition, texturing, grain shape distribution and grain boundary characteristics can be optimised for particular applications, simply by applying different NiTi substrate pretreatment regimes. It is suggested that this bears significant implications for influencing bulk properties such as cohesive and shear strength, as well as ductility, conductivity and cohesion in thick tantalum coatings. |
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Propulsive effect of microwave-induced plasma jet on spark ignition of CO2-diluted CH4-air mixture |
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Xinhua Zhang, Zhaowen Wang, Huimin Wu, Chaohui Liu, Xiaobei Cheng, Jyh-Yuan Chen |
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China, USA |
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https://doi.org/10.1016/j.combustflame.2021.111400
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To explore the application potential of microwave-assisted spark ignition (MAI) under exhaust gas recirculation conditions, the ignition performance of MAI under CO2 dilution is tested with CH4-air premixed spherical flames. Experiments are carried out in a constant volume combustion chamber with CO2 dilution ratio of 0–20% and equivalence ratio varied from 0.5–1.0. The microwave pulse repetition frequency (PRF) and trigger delay are altered to evaluate the interaction time window between microwave and flame kernel according to the occurrence of bright spot. Results show that MAI extended the lean limit from 0.7 to 0.6 when the mixture is diluted with 8% CO2. At equivalence ratio 1.0, the CO2 dilution limit is extended from 8% in SI mode to 20% in MAI mode. Delaying the microwave trigger beyond 1 ms, the bright spot no longer occurs implying that the time window is about 1 ms. The time window is extended to 2 ms with 1 kHz microwave triggered synchronously with spark, and increasing the microwave PRF to 10 kHz prolongs the time window to 3 ms. However, as CO2 added, the time window is obviously shortened and no more than 1 ms, indicating that CO2 dilution accelerates the decay of electron density in the flame kernel, so that the enhancement is mainly reflected in the first microwave pulse with 1 kHz PRF. The single microwave pulse of 1 kHz induces stronger plasma jet propelling the flame front, and its direction directly decides the ignition success rate near ignitable limit. On the whole, under high ratio of CO2 dilution, increasing the intensity and controlling the direction of microwave-induced plasma jet is beneficial to MAI performance. |
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Understanding the influence of microstructure on hot corrosion and erosion behavior of suspension plasma sprayed thermal barrier coatings |
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Nitish Kumar, Satyapal Mahade, Ashish Ganvir, Shrikant Joshi |
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Sweden, Finland |
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https://doi.org/10.1016/j.surfcoat.2021.127306
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• SPS TBCs with varying columnar microstructural features and mechanical properties were deposited.
• Influence of parameters (suspension feed rate, spray distance, etc.) on microstructural features in SPS TBCs examined. • Desirable microstructural features were identified to minimize erosion and hot corrosion. |
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Thermal barrier coatings (TBCs) are bilayer systems comprising a 7–8 wt% yttria partially stabilized zirconia (YSZ) top coat deposited over a metallic bond coat. Suspension plasma spraying (SPS) is an advanced and attractive top coat processing technique due to its capability to yield a variety of microstructures, including the desired columnar microstructure for enhanced strain tolerance and durability. This work attempts to investigate the desirable microstructural features in an SPS processed TBCs to mitigate hot corrosion and minimize erosion related losses that are often responsible for coating degradation. SPS processed TBCs were deposited utilizing three different spray conditions to obtain distinct microstructural features (column density, interpass [IP] porosity bands, column width), porosity content, and mechanical properties. Apart from comprehensive characterization utilizing SEM, XRD and micro-indentation tests, the as-deposited TBCs were subjected to hot-corrosion tests in the presence of vanadium pentoxide and sodium sulfate as corrosive salts. Post-corrosion analysis revealed complete infiltration of the molten salts in all the investigated TBCs. However, the delamination cracks generated due to the infiltrated corrosive species were minimal in case of TBCs with higher fracture toughness. The differences in microstructure and mechanical properties also led to differences in erosion performance, with TBCs possessing minimal total porosity content and high fracture toughness best resisting erosion related damage. Post-erosion analysis revealed that the TBCs with higher fracture toughness and micro-hardness showed superior erosion resistance. Based on the erosion and corrosion results and subsequent post-mortem of failed specimens, plausible damage mechanisms are proposed. Findings from this work provide new insights on developing damage tolerant TBCs microstructures with enhanced durability when exposed to erosion and hot corrosion environments. |
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Unipolar plasma electrolytic oxidation: Waveform optimisation for corrosion resistance of commercially pure titanium |
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Luca Casanova, Livio Vicentini, MariaPia Pedeferri, Marco Ormellese |
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Italy |
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https://doi.org/10.1002/maco.202012198 |
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This study deals with the anodisation of titanium grade 2 in 0.5-M sulphuric acid using a pulsed signal in a unipolar regime. The electrical parameters investigated are voltage, frequency and duty cycle. The use of duty cycles with a high percentage of anodic polarisation (90%), combined with high frequencies (1000 Hz) and the higher voltage tested (220 V), favoured the establishment of a plasma regime involving strong dielectric discharges, allowing the growth of thicker oxides but with rough architecture. The corrosion resistance of the formed film has been characterised by potentiodynamic tests in 0.5-M NaBr for localised corrosion resistance and by immersion tests in 10% v/v sulphuric acid solution for a uniform corrosion assessment. Current–time curves, visual observations and electron microscope analysis (scanning electron microscopy, energy-dispersive X-ray spectroscopy) were the tools selected to provide a correlation between technological parameters and oxide growth mechanism. For localised and uniform corrosion, anodisation at 220 V with a high level of anodic polarisation (90%) and frequency (1000 Hz) was verified to be particularly advantageous. |
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Strengthening of copper with homogeneous dispersion of nanoscale tungsten particles fabricated by spark plasma sintering |
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J. G. Ke, Z. M. Xie, R. Liu, R. Gao, X. P. Wang, X. B. Wu, K. Jing, L. Wang, B. L. Zhao, Q. F. Fang, C. S. Liu |
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China |
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https://doi.org/10.1016/j.msea.2021.141438
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• Cu–W alloys with high strength and excellent thermal conductivity were fabricated.
• W nanoparticles significantly refine the grains and improve the strength of Cu. • The average particle size of W is 43 nm and the grain size of Cu–W is 500–900 nm. |
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Copper alloys are promising heat sink materials in future fusion reactors owing to the high thermal conductivity and good mechanical properties at medium temperatures. In the present study, aiming at enhancing the strength of copper while keeping the high thermal conductivity, nanoscale W particle dispersion strengthened Cu alloys with different W content of 2 at% (2.6 vol%), 5 at% (6.5 vol%) and 8 at% (10.3 vol%) were fabricated through ball-milling and spark plasma sintering (SPS). The effects of nanoscale W particles on the microstructure, mechanical properties and thermal conductivity of the Cu–W alloys were investigated. The average size of tungsten particles dispersed in copper matrix is 43 nm. The dispersion of W nanoparticles in copper could significantly refine the grain and improve the strength of Cu alloys. The average grain size of Cu-2at%W, Cu-5at%W and Cu-8at%W is as small as 0.84 μm, 0.65 μm and 0.54 μm, respectively. The tensile strength of Cu-8at%W reaches 495 MPa and the elongation is 10.6% at room temperature. The grain size refinement of Cu–W alloys can be attributed to the pinning effects of nanoscale W particles dispersed in the Cu matrix. Although the addition of W nanoparticles leads to a decrease in thermal conductivity, the thermal conductivity for all Cu–W samples is still above 300 Wm-1K-1 at room temperature. |
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Comparative Study of the Influence of Helium and Argon Plasma on Crystallogenic Properties of the Blood |
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Andrew K. Martusevich, Alexander G. Galka, Elena S. Golygina, Alexandra S. Fedotova, Alexander N. Tuzhilkin, Svetlana L. Malinovskaya |
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Russia |
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DOI: 10.1615/PlasmaMed.2021038035
Plasma Medicine, 11(1):69 – 79 (2021) |
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The aim of this study was to compare the biological effects of helium and argon plasma in vitro. The cold plasma was generated using a device developed at the Institute of Applied Physics of the Russian Academy of Sciences (Nizhny Novgorod), which uses the principle of microwave ionization of the gas flow. We studied the crystallogenic activity of blood plasma. The description of dehydrated blood plasma samples was performed morphologically, using a system of visuametric parameters. Main morphometric parameters for analysis of blood plasma crystallization include crystallizability, structure index, facia destruction degree, and size of marginal zone. This study allowed us to establish that the effect of helium and argon in both free and ionized forms on the crystallogenic activity of blood varies significantly. The effect of cold plasma in general should be described as more favorable relative to the corresponding nonionized fluxes. At the same time, the most optimal nature of the reaction of the biological fluid was recorded when using a helium cold plasma. A specific feature of the helium flow is the suppression of the crystallogenic activity of the biological fluid, and the argon flow leads to its increase. Ionization of gases optimizes the nature of their influence, moreover, according to the modeling effect, the helium cold plasma is closest to the control sample. |
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Development of a Compact Plasma Sterilization Device for Contact Lenses |
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Takehiko Sato, Kazuki Okazaki, Tomoki Nakajima, Shigeru Fujimura, Tatsuyuki Nakatani |
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Japan |
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DOI: 10.1615/PlasmaMed.2021037288
Plasma Medicine, 11(1):57 – 67 (2021) |
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In this study, our goal was to develop a contact lens sterilization device using non-thermal plasma. Three types of sterilization devices, a plasma-container-separated type (Ver. 1), a screw electrode type (Ver. 2), and a plasma actuator type (Ver. 3), were constructed and the electrical, chemical, and flow characteristics were investigated. Ver. 2 and Ver. 3 showed a good sterilization performance. The sterilization time was 2 minutes in air for both Ver. 2 and Ver. 3. In water, sterilization times were 30 minutes for Ver. 2 and 25 minutes for Ver. 3, because the chemical reactive species generated by these two devices were transported by the gas and water flows in the contact lens case. The effect of pH was also investigated, and we found that the low pH value with other reactive species such as ozone were important for sterilization. Finally, we propose a safe, small, and low power consumption device with high contact lens sterilization performance using plasma.
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Application of Nd-Fe-B Permanent Magnets with Ion-Plasma ZrO2 Coating in Orthodontics |
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V.I. Kutsevliak, S.L. Starikova, A.V. Taran, O.I. Tymoshenko, I.O. Misiruk, V.V. Starikov |
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Ukraine |
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DOI: 10.1615/PlasmaMed.2021037741
Plasma Medicine, 11(1):47 – 55 (2021) |
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The use of braces for correcting the position of single teeth in some cases seems to be impractical, since this may lead to a violation of the position of adjacent teeth used as a support for such correction. An alternative way to displace single teeth into a normal position is to use an apparatus with permanent Nd-Fe-B magnets, which allows localizing the impact of force and the required aesthetic and functional result with fewer side effects, as well as reducing the cost of treatment. The structure, phase composition of zirconium oxide films on Nd-Fe-B magnets have been investigated by means of scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray fluorescent analysis (XRF). The influence of the ZrO2 coating in terms of its barrier properties for corrosion in quasi-physiological 0.9 NaCl solution has been studied. Clinical case of the treatment of malocclusion by using orthodontic appliances with permanent magnets is discussed. |
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Plasma Activated Water: Implication as Fungicide, Growth and Yield Stimulator of Potato (Solanum Tuberosum L.) |
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A. Aktar, S. Sarmin, U.A. Irin, M.M. Rashid, M.M. Hasan, M.R. Talukder |
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Bangladesh |
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DOI: 10.1615/PlasmaMed.2021038184
Plasma Medicine, 11(1):31 – 46 (2021) |
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Seed germination rate, plant growth, and yield of crops are increased due to treatment of seeds with atmospheric pressure cold plasma (ACP). Seed treatment and foliar spray with ACP-treated water (PAWs) may play important roles in the control of plant disease because of the presence of highly reactive oxygen species in water. PAWs were prepared with atmospheric pressure discharges in waters with different treatment durations. The present experiment explored the effects of seed treatment and foliar spray by PAWs to control late blight disease and the yield of potato (Solanum tuberosum L.). The study reveals that the late blight incidence, disease severity, and the number of leaf infections were significantly reduced, with a few exceptions, in comparison with control, due to the seed treatments and foliar spry of PAWs. The plant height, tuber number, and tuber yield were increased. The results obtained in this filed experiment are promising. Thus, this investigation reveals that the PAWs can be an effective alternative of fungicides to control the late blight disease and to stimulate the enhancement of yield of potato as well. Further investigations have to be conducted in order to draw definite conclusion. |
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The Potential Use of a Cold Atmospheric Plasma Jet for Decontamination of Hospital Surfaces. A Pilot Study |
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Muireann Fallon, Sarah Kennedy, Sharath Kumar, Stephen Daniels, Hilary Humphreys |
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Ireland |
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DOI: 10.1615/PlasmaMed.2021037267
Plasma Medicine, 11(1):15 – 30 (2021) |
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Hospital surfaces are a source of potential infection due to contamination by microorganisms such as bacteria and viruses. Bacterial biofilms are of particular importance, due to their persistence in the hospital environment. Cold atmospheric pressure plasma (CAPP) is a novel potential method of hospital surface decontamination. In this study, we aimed to show the potential use of a CAPP jet for hospital decontamination. Bacterial biofilms were grown on common hospital surface materials and treated with an air-driven CAPP jet. Viable bacteria in treated biofilms were measured. Confocal microscopy and staining were used to gather images of CAPP-treated biofilms. The effect of CAPP inactivation was also assessed alongside the use of a detergent. CAPP inactivated clinically relevant bacteria both in planktonic and biofilm structures. A 90 s CAPP treatment led to an average of 82% decrease in Escherichia coli (E. coli) and 70% decrease in methicillin-resistant Staphylococcus aureus (MRSA) biofilm viability grown on polysterene. Confocal microscopy was used to confirm CAPP-induced inactivation of bacterial cells within mature growth on glass. CAPP treatment was also compared to treatment with detergent commonly used in hospitals. It was found that biofilm inactivation was greatest when treated with both detergent and CAPP. When in combination with detergent, viability of E. coli and MRSA biofilms grown on polysterene were decreased by 97% and 94%, respectively. A CAPP jet was shown to inactivate biofilms on hospital surfaces, particularly when used alongside detergent. This may suggest a role for CAPP in hospital decontamination. |
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Effect of Plasma Discharge on Epidermal Layer Structure in Pig Skin |
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Ahmad Guji Yahaya, Jaroslav Kristof, Marius Blajan, Fariha Mustafa, Kazuo Shimizu |
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Japan |
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DOI: 10.1615/PlasmaMed.2021036925
Plasma Medicine, 11(1):1 – 13 (2021) |
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Plasma can efficiently inactivate microbial pathogens. Application of plasma on the skin can not only kill bacteria but also change the nature of skin. The influence of plasma jet treatment on the stratum corneum was investigated using the skin of a Yucatan micro pig. Microscopic observation of the histological skin section was used to characterize the etching effect of plasma jet depending on treatment time. Changes in lipid conformations were determined by the bandwidth and absorbance of the symmetric and asymmetric stretching of CH2 and CH3 bands and their ratios using ATR-FTIR spectroscopy. Plasma jet caused structural changes observed via an increase in bandwidth and a decrease in absorbance of the lipid vibrational bands. Plasma effects were saturated after 2 min of treatment. The influence of temperature and UV irradiation was also evaluated. The monitoring of plasma-treated skin demonstrated the temporal effect of changes caused by plasma. |
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Hard Anodizing and Plasma Electrolytic Oxidation of an Additively Manufactured Al-Si alloy |
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H. Mora-Sanchez, R. del Olmo, J. Rams, B. Torres, M. Mohedano, E. Matykina, R. Arrabal |
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Spain, Belgium |
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https://doi.org/10.1016/j.surfcoat.2021.127339
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• Anodic films by HA and PEO are studied on DMLS Al10Si1Mg and cast A361 alloys.
• Anisotropy in the AM alloy is translated into HA and PEO coatings. • Wear resistance of PEO is superior to that of HA for both alloys. • Oxidation of the fine 3D Si network in the AM alloy results in softer coatings. |
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Plasma Electrolytic Oxidation (PEO) and Hard Anodizing (HA) coatings are investigated on an Additively Manufactured (AM) Al10Si1Mg alloy obtained via Direct Metal Laser Sintering (DMLS). Results are compared to those obtained for a conventional A361 cast alloy. Findings revealed that the microstructure of the AM alloy, consisting of α-Al cells enclosed in a Si network, produces coatings that are more uniform –in terms of morphology, thickness and roughness of the coating/substrate interface– than those obtained on the cast alloy. However, enhanced oxidation of the fine Si network in the AM alloy results in softer coatings. In both alloys, PEO coatings demonstrate superior wear protection than HA due to the presence of mullite in the former. The anisotropy in the microstructure of the AM alloy influences the tribological behaviour of studied coatings, with the XZ plane showing superior wear performance. |
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Microstructure and properties of plasma electrolytic oxidation coating on 55% SiCp/Al matrix composites |
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Chunyan Du, Shutao Huang, Xiaolin Yu, Quanzhao Wang, Hui Zhao |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127321
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• The influence of SiC particles size on plasma electrolytic oxidation is analyzed.
• SiC particles hinder the formation of the film and the ejection of the melt. • The large size of SiC particles causes the coating ablation. • SiC particles affect the properties of plasma electrolytic oxidation coating. |
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Protective coating was successfully prepared on two types of SiCp/Al matrix composites by plasma electrolytic oxidation (PEO) method, where the SiCp/Al matrix composites contains high volume fraction of SiC particles with sizes of 60 μm and 40 μm, respectively. Current-time curves were recorded during the PEO process in a constant voltage mode. The surface and cross-section morphologies, composition and adhesive force of the coatings were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), and coating adhesion automatic scratch tester, respectively. The electrochemical corrosion behavior of the substrate and coated composites was investigated in 3.5% NaCl solution by potentiodynamic polarization tests and EIS. The results show that the current change trend and coating morphology features of the two type of composites were consistent. SiC particles at high volume fraction could hinder the formation of the film and the ejection of the melt, resulting in rough, uneven pores with variable sizes, coarse molten particles and micro-cracks on the coatings. There is ablation on 60 μm-SiC/Al coating. The PEO coating was mainly composed of mullite, α-Al2O3, γ-Al2O3 and amorphous phases. The adhesive force of coating on 40 μm-SiC/Al matrix composite (68.1 N) is better than that of 60 μm-SiC/Al matrix composite (22.0 N). The corrosion resistance of SiCp/Al matrix composite was improved by plasma electrolytic oxidation treatment. |
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Effect of electrolytic plasma polishing on microstructural evolution and tensile properties of 316L stainless steel |
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Gangqiang Ji, Huanwu Sun, Haidong Duan, Dongliang Yang, Jinyan Sun |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127330
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• EPP has no adverse effect on the surface properties while reducing the surface roughness of machined 316L stainless steel.
• The average grain size of machined 316L stainless steel surface is reduced after EPP. • EPP may be an effective method to improve the grain boundary distribution and dislocation density. • The tensile properties of 316L stainless steel are improved by EPP treatment. • The dynamic composite energy during EPP might be the main factor of the surface microstructure evolution. |
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Electrolytic plasma polishing (EPP) is an advanced technique for high-quality surface finishing of metal and alloy materials. Austenitic 316L stainless steel (SS) is extensively used in various industrial applications due to its excellent comprehensive performance. Therefore, it is widely studied to improve its properties by specific means and methods and expand its scope of application. In this paper, the influence of EPP generated dynamic composite energy on the microstructural evolution and tensile properties of machined 316L SS is investigated. A decrease in the surface roughness (from 0.103 μm to 0.046 μm), average grain size (from 5.65 μm to 5.21 μm), and low angle grain boundaries (LAGBs) are observed, along with an increase in geometrically necessary dislocation density in post EPP samples. Post EPP, grains are found to be predominantly oriented in 〈101〉. Schmid factor variation (from 0.475 to 0.45) shows a reduction in plastic deformability of the material. The yield strength and tensile strength of the material is increased by 8.98% and 4.32%, approximately, after EPP treatment. The dynamic composite energy produced during the EPP process may induce a cavitational effect, causing (i) rupture of the vapor-gaseous envelope, (ii) high-energy plasma bombardment, and (iii) development of annealing stress inside the material, resulting in microstructural evolution of 316L SS. |
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Enhancement of metal adhesion, owing to the plasma texturing of PEEK |
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David Gravis, Grégoire Rigolé, Mayssa Yengui, Wolfgang Knapp, Jean-François Coulon, Fabienne Poncin-Epaillard |
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France |
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https://doi.org/10.1002/ppap.202100009 |
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To understand both chemical and anchoring aspects of Al adhesion, the poly-ether-ether-ketone (PEEK) surface was plasma-textured before being coated. The practical adhesion was compared with that obtained by laser texturing. The surfaces and assemblies were characterized by scanning electron microscopy, atomic force microscopy, surface free energy determination, and pull-off tests. Patterning processes increase Al adhesion. O2 plasma appears to be the most efficient through a texture assigned to the chemical erosion, whereas Ar plasma mostly induces material etching with thermal effects altering the PEEK crystallinity. With low-pressure plasmas, this texturing can be added to the chemical functionalization to further increase the adhesion. |
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Tuning the wicking and wettability properties of PET textiles by DBD or a remote atmospheric RF torch: A comparison |
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Annaëlle Demaude, Rosanna Inturri, Cristina Satriano, Perrine Leroy, François Reniers |
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Belgium |
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https://doi.org/10.1002/ppap.202100005 |
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Textile industry is constantly searching for easy and rapid ways to improve the properties of textiles. In this matter, plasma treatments have already proven to be an efficient and green solution, as they proceed in a dry environment and require minimal use of chemicals. To date, most of the work on the subject has been performed with low-pressure plasmas. Recently, atmospheric plasmas have received increasing interest, especially for industrial applications. Indeed, the possibility to avoid the use of pumping systems makes this technology easily implementable in continuous in-line processes. For many applications, the treatment aims at modifying the textile surface to increase the overall hydrophilicity. The latter is often probed by the water contact angle, but this does not always reflect the global hydrophilic behavior of the textile as a three-dimensional material. A complementary study of the wicking properties is important to better reflect the penetration of liquids into the textile, but it is poorly reported in the literature. The present work aims at increasing the water uptake of polyethylene terephthalate (PET) textile by direct or remote plasma treatment, which are the two main trends in this field. For this purpose, a dielectric barrier discharge (DBD) and a radiofrequency plasma torch at atmospheric pressure are used, respectively. Different plasma parameters are varied and their respective effect on the wicking properties of the fabric, assessed by an absorbency test developed ad hoc, are correlated to their surface chemical composition determined by X-ray photoelectron spectroscopy. These results are compared with the possible changes in wetting of the fiber surface witnessed by water contact angles measured on PET foil samples submitted to the same plasma treatments. Complete wicking of water in PET textile can be obtained after 20 or 10 s of torch treatment with pure Ar plasma or Ar/O2 mixture, respectively. However, a comparable effect is detected, after 30 s of DBD Ar plasma treatment, under the used experimental conditions. Besides, the addition of O2 to the discharge has an opposite effect on the fabric wicking. These results are discussed in terms of the peculiar processes in surface activation and modification of the fabric surface triggered by the two different plasma technologies. |
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Diagnostics of a large volume pintoplate atmospheric plasma source for the study of plasma species interactions with cancer cell cultures |
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Laurence Scally, Sean Behan, Andressa M. Aguiar de Carvalho, Chaitanya Sarangapani, Brijesh Tiwari, Renee Malone, Hugh J. Byrne, James Curtin, Patrick J. Cullen |
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Ireland, Australia |
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https://doi.org/10.1002/ppap.202000250 |
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A large gap pin-to-plate, atmospheric-pressure plasma reactor is demonstrated as means of in vitro study of plasma species interactions with cell cultures. By employing optical emission and optical absorption spectroscopy, we report that the pin-to-pate plasma array had an optimal discharge frequency for cell death of 1000 Hz in ambient air for the target cancer cell line, human glioblastoma multiform (U-251MG). The detected plasma chemistry contained reactive oxygen and nitrogen species including OH, N2, N2+ and O3. We show that by varying the plasma discharge frequency, the plasma chemistry can be tailored to contain up to 8.85 times higher levels of reactive oxygen species (ROS) as well as a factor increase of up to 2.86 for levels of reactive nitrogen species (RNS). At higher frequencies, ROS are more dominant than RNS, which allows for a more dynamic and controlled environment for sample study without modifying the inducer gas conditions. When used for treatment of culture media and cell cultures, variation of the plasma discharge frequency over the range 1000–2500 Hz demonstrated a clear dependence of the responses, with the highest cytotoxic responses observed for 1000 Hz. We propose that the reactor offers a means of studying plasma–cell interactions and possible cofactors such as pro-drugs and nanoparticles for a large volume of samples and conditions due to the use of well plates. |
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Synergistic anticancer effects of different combinations of He+O2 plasma jet and doxorubicin on A375 melanoma cells |
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Hao Zhang, Shengduo Xu, Jishen Zhang, Bing Li, Dingxin Liu, Li Guo, Zhijie Liu, Dehui Xu |
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China |
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https://doi.org/10.1002/ppap.202000239 |
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Cold atmospheric plasma technology is expected to become an option for adjuvant therapy in cancer due to its promising anticancer effect. Here, we evaluated the effects of different combinations of He+O2 plasma jet and clinical anticancer drug, doxorubicin, on A375 melanoma cells in vitro. The results show that the synergistic anticancer effect of plasma jet and doxorubicin is dependent on the manner of their combination. Although doxorubicin does not affect plasma jet-induced exogenous oxidative stress in A375 cells, the synergistic anticancer effect of continuous doxorubicin treatment with subsequent plasma jet treatment is significantly better than that of simultaneous continuous doxorubicin and plasma jet treatment. It is proposed that plasma jet interventions may create transitory therapeutic windows for continuous chemotherapy. Our results will help to optimize therapeutic approaches that include combinations of anticancer drugs and plasma for future clinical applications. |
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Evaluation of microbial species inactivation and purification of pond sewage by a custom-built air surface discharge plasma |
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Zhijie Liu, Dehui Xu, Bolun Pang, Sitao Wang, Shuai Wang, Yuting Gao, Sansan Peng, Hailan Chen, Michael G. Kong |
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China, USA |
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https://doi.org/10.1002/ppap.202100004 |
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The presence of the hazardous microbial species in pond sewage is a serious threat to the aquatic environment and human health, and an effective purification method is urgently needed. Here, we reported the evaluation and purification effect of sewage by a custom-built air surface discharge plasma. Results show that the most sensitive bacterial flora mainly includes Cyanobium, Candidatus, and Proteobacteria, based on inactivation map by the DNA sequence. The inactivation of microbial species by plasma treatment would reach beyond 5-log reduction and the water turbidity would be effectively improved. Identification of the significance of reactive oxygen and nitrogen species with scavengers indicates that the purification effect is closely linked to the key agents ONOO− and H2O2. This study would contribute to an in-depth insight into decontamination and provide a potential alternative for sewage purification. |
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Antimicrobial and anticancer efficacy of atmospheric pressure cold plasma technology |
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Hom Bahadur Baniya, Sudip Panday, Pabitra Khadka, Anusuya Nepal ,Rajesh Prakash Guragain, Gobinda Prasad Panta, Santosh Dhungana, Bhupal Govinda Shrestha, Deepak Prasad Subedi |
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Nepal |
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https://doi.org/10.33263/MaterialsXY.ABCDEF |
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In the present work, the inactivation efficiency of atmospheric pressure cold plasma (APCP) was evaluated against three pathogenic microorganisms. We have successfully developed a plasma device that is able to generate atmospheric pressure cold argon plasma of low temperature (240 - 270C) downstream using a high-voltage power source (6 kV) operating at a frequency of 19.56 kHz which can be widely used in biomedicine. Therefore, a cost-effective system of generating cold plasma jet at atmospheric pressure with potential applications in biomedical research has been developed. The discharge has been characterized by an optical method. This research aims to investigate the antimicrobial property shown by the atmospheric pressure cold plasma Jet (APCPJ). Three pathogenic bacterial strains (Shigella flexneri, Escherichia coli, and Klebsiella pneumoniae) were used to test the antimicrobial property. The effects of atmospheric pressure cold plasma (APCP), today, have been identified worldwide in disinfection, decontamination, and sterilization as well as oncology applications. This work aims to demonstrate the effect of APCP irradiated media as a promising anti-cancer tool. Atmospheric pressure cold plasma technology has the efficacy to show anticancer properties with the treatment of cancer cells. To demonstrate the anti-cancer properties of APCP generated at high voltage power supply (12 kV) at an operating frequency of 50 Hz. 10% Dulbecco’s Modified Eagle Medium (DMEM) media were treated with cold plasma using Argon as a process gas for various time durations (0.5-4 min). The treated media was transferred to Henrietta Lacks (HeLa), and Human Embryonic Kidneys 293(HEK 293) cells and the viability of cancer cells was observed using MTT assay. |
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Effect of the width and depth of laser-textured grooves on the bonding strength of plasma-sprayed coatings in the scratch direction |
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Delong Jia, Peng Yi, Yancong Liu, Hongyu Jia, Xiaoshuang Yang |
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China |
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https://doi.org/10.1016/j.msea.2021.141558
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In this study, atmospheric plasma spraying was used to deposit molybdenum coatings on stainless steel substrates with laser-textured groove patterns and grit blasting substrate pretreatment. The groove depth and width were controlled by selecting the number of scans with a nanosecond pulse laser (1, 3, 5, and 7), while the groove spacing was 100 μm, 150 μm, and 200 μm. The pull-off bonding strength and shear bonding strength parallel and perpendicular to the grooves of the coatings were analyzed using a pull-off and scratch instrument. Furthermore, optimal laser scan times of the groove opening angle were obtained. The results showed that the coating adhesion strength on the grooved substrate with a 100 μm spacing and 5 scans was greater than the cohesive strength. On the other hand, the pull-off bonding strength of coatings on the substrates made with 5 and 3 scans was superior to that on the grit-blasted stainless steel substrate; furthermore, the shear bonding strength in parallel and perpendicular scratch directions of the coating made on the grooved substrate with 5 scans was greater than that on the grit-blasted substrate; for all textured substrate coatings, the shear bonding strength in the parallel direction higher than that in the perpendicular direction. Finally, the equations that correlate the groove width, opening angle, pull-off bonding strength, shear bonding strength, and scanning times were predicted. The study provides significant experimental findings and a theoretical basis about the bonding strength of the laser-textured substrate plasma spraying coatings. |
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Low-temperature inductively coupled plasma as a method to promote biomineralization on 3D printed poly(lactic acid) scaffolds |
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John P. Bradford, Bernabe Tucker, Gerardo Hernandez-Moreno, Phillip Charles, Vinoy Thomas |
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USA |
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https://doi.org/10.1007/s10853-021-06227-z |
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For bone tissue engineering, additive manufacturing offers promise in the development of biomimetic scaffolds; however, common polymers used in typical 3D printing methods often suffer from less than ideal surface properties for proper mineralization. As a result, they can underperform with respect to biointegration without additional modification. In this study, low-temperature plasma was utilized to modify the surface of 3D printed poly(lactic acid) (PLA) for promoting mineralization in biomimetic in vitro conditions. Detection of calcium phosphates on the polymer surfaces was accomplished via Fourier transform infrared (FT-IR) spectroscopy and X-ray photoelectron (XPS) spectroscopy. Scanning electron microscopy (SEM) was employed to identify and image the mineralization products on the surfaces of the scaffolds. Further, a fluorescent assay of surface extracts identified calcium-containing mineral deposits at significantly higher levels for treated scaffolds versus controls. Taken together, these results suggest the futuristic potential of this surface modification method for bone tissue engineering applications. |
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State of the art in nonthermal plasma processing for biomedical applications: Can it help fight viral pandemics like COVID‐19? |
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Nilanjal Misra, Sudhir Bhatt, Farzaneh Arefi-Khonsari, Virendra Kumar |
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India, France |
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https://doi.org/10.1002/ppap.202000215 |
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Plasma processing finds widespread biomedical applications, such as the design of biosensors, antibiofouling surfaces, controlled drug delivery systems,
and in plasma sterilizers. In the present coronavirus disease (COVID‐19) situation, the prospect of applying plasma processes like surface activation, plasma grafting, plasma‐enhanced chemical vapor deposition/plasma polymerization, surface etching, plasma immersion ion implantation, crosslinking, and plasma decontamination to provide timely solutions in the form of better antiviral alternatives, practical diagnostic tools, and reusable personal protective equipment is worth exploring. Herein, the role of nonthermal plasmas and their contributions toward healthcare are timely reviewed to engage different communities in assisting healthcare associates and clinicians, not only to combat the current COVID‐19 pandemic but also to prevent similar kinds of future outbreaks. |
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Highly efficient nitrogen fixation enabled by an atmospheric pressure rotating gliding arc |
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Hang Chen, Angjian Wu, Stéphanie Mathieu, Peihan Gao, Xiaodong Li, Bo Z. Xu, Jianhua Yan, Xin Tu |
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China, UK |
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https://doi.org/10.1002/ppap.202000200 |
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A rotating gliding arc is proposed as a promising alternative to enable direct nitrogen fixation from ubiquitous air under mild conditions. The effect of different process parameters on NO x generation and energy consumption has been investigated through a combination of experiments and artificial neural network (ANN) modeling. The optical emission spectroscopic diagnostics together with electrical diagnostics and high-speed photography has been used to understand the variation of the discharge characteristics. The lowest energy consumption of NO x production (4.2 MJ/mol) is achieved at a gas flow rate of 12 L/min and an O2 concentration of 20 vol%. The simulation results from the ANN model show a good agreement with the experimental data and the model enables us to evaluate the relative importance of the process parameters to the reaction performance. |
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Fourier-transform infrared spectroscopy of ethyl lactate decomposition and thin-film coating in a filamentary and a glow dielectric barrier discharge |
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Natalia Milaniak, Gaétan Laroche, Françoise Massines |
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Canada, France |
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https://doi.org/10.1002/ppap.202000248 |
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Glow and filamentary regimes of atmospheric pressure plasma-enhanced chemical vapor deposition in a planar dielectric barrier discharge configuration were compared for thin-film deposition from ethyl lactate (EL). EL decomposition in the plasma phase and thin-film composition were both characterized by Fourier-transform infrared spectroscopy. EL chemical bonds' concentration along the gas flow decreases progressively in the glow dielectric barrier discharge (GDBD), whereas it drastically oscillates in the filamentary dielectric barrier discharge (FDBD), with values higher than that of the initial mixture. EL decomposition route depends on the discharge regime, as the decrease of the concentration of the different investigated bonds is different for an identical amount of energy provided to EL molecules. CO2 is systematically formed reaching concentrations of 25 and 40 ppm, respectively, in FDBD and GDBD. |
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An investigation of adhesion mechanisms between plasma-treated PMMA support and aluminum thin films deposited by PVD |
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Mohamed Mounder Kouicem, Eric Tomasella, Angélique Bousquet, Nicolas Batisse, Guillaume Monier, Christine Robert-Goumet, Laurent Dubost |
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France |
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https://doi.org/10.1016/j.apsusc.2021.150322
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• Aluminum thin films are deposited on PMMA sheets by magnetron sputtering.
• Oxygen containing plasma pre-treatment improves the adhesive properties of PMMA. • Carbonyl groups are grafted on the PMMA surface during plasma pre-treatment. • Plasma UV can degrade the polymer surface by carbon chain scission phenomena. |
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The metallization of polymers has been the subject of several scientific studies Polymethylmethacrylate PMMA is known to have very bad adhesion to plasma deposited aluminum thin films. This study focuses on understanding the phenomena of adhesion between PMMA and metallic aluminum films deposited by magnetron sputtering. Before deposition, in situ pulsed DC plasma pre-treatment was performed in various atmospheres. We showed that oxygen-rich and short duration plasma pre-treatment considerably increase PMMA’s adhesives properties. Contact angle measurements showed a significant increase in the wettability of plasma pre-treated samples. XPS analysis revealed that the interaction between plasma species and polymer surface results in two simultaneous phenomena: surface functionalization by the introduction of oxygenated chemical functions such as carbonyl groups (CO) and surface degradation by the splitting of carbon chains by plasma UV radiation. Moreover, AFM analyses showed that the slight increase in surface roughness leads to best adhesion between PMMA and aluminum. |
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Atmospheric pressure plasma engineered superhydrophilic CuO surfaces with enhanced catalytic activities |
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Avishek Dey, Gauthaman Chandrabose, Paheli Ghosh, Lois A.O Damptey, Adam H. Clark, Vimalnath Selvaraj, Ramachandran Vasant Kumar, Nicholas St. J. Braithwaite, Siarhei Zhuk, Goutam Kumar Dalapati, Seeram Ramakrishna, Satheesh Krishnamurthy |
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UK, Switzerland, Singapore, India |
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https://doi.org/10.1016/j.apsusc.2021.150413
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• Fast and environment friendly route to engineer CuO thin film surfaces.
• Low power atmospheric pressure plasma jet transforms CuO surface superhydrophilic. • Plasma functionalisation boosts electro and photocatalytic activities. • Presence of oxygen radicals critical for the enhanced activities. • Energetic species in plasma perturbs the local electronic and lattice structure. |
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Cupric oxide (CuO) thin film has found widespread application as a low-cost, earth-abundant material for electro and photo catalytic applications. High surface wettability is a key factor to achieve enhanced efficiency in these catalytic applications. Here, we report a fast and environment friendly route to fabricate super hydrophilic CuO thin films using a low power (5–10 W) atmospheric pressure plasma jet (APPJ). With APPJ treatment for 5 min, the CuO surface transforms from hydrophobic to super-hydrophilic with threefold increase in catalytic activity. The electrodes were extensively characterized using various bulk and surface-sensitive techniques. APPJ introduces anisotropy in the crystal structure and creates unique three-dimensional surface morphology with distinct surface chemical and electronic features. Interestingly, presence of oxygen in the plasma was found to be critical for the enhanced activities and the activity decreased when the functionalised with nitrogen plasma. Oxygen plasma functionalisation of CuO electrodes resulted in a 130 mV reduction in the onset potential for oxygen evolution reaction along with enhanced current density, 10 mA cm−2 against 3 mA cm−2 at 1 V vs Saturated Calomel Electrode in 0.1 M KOH without iR compensation. Importantly, without introducing any external dopants the work function could be decreased by 80 mV. Moreover, the treated films exhibited a higher rate of photo degradation (0.0283 min−1 compared to 0.0139 min−1) of Methylene Blue and phenol indicating efficient charge separation. This work presents the potential of APPJ functionalisation of CuO surface to boost the activity of other thin film catalyst materials and solutions processed systems. |
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Acrylic acid plasma polymerization and post-plasma ethylene diamine grafting for enhanced bone marrow mesenchymal stem cell behaviour on polycaprolactone nanofibers |
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Mahtab Asadian, Ke Vin Chan, Tim Egghe, Yuliia Onyshchenko, Silvia Grande, Heidi Declercq, Pieter Cools, Rino Morent, Nathalie De Geyter |
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Belgium |
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https://doi.org/10.1016/j.apsusc.2021.150363
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• Deposition of plasma polymerized layer on polycaprolactone nanofibers did not cause any changes to their delicate nano-morphology.
• X-ray photoelectron spectroscopy measurements confirmed a significant increase in O-content for the plasma polymerized PCL nanofibers. • An additional post-grafting step successfully converted the surface carboxylic acid functionalities into primary amines. • Both treatment approaches caused a profound improvement in cell activities due to the incorporation of cell-interactive functional groups. • The conversion of carboxylic acids to primary amine functionalities resulted in a significant improvement in cell-surface interactivity. |
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Electrospun polycaprolactone (PCL) nanofibers (NFs) have been extensively researched for tissue engineering purposes, despite their hydrophobic surface properties which compromise their cell interactivity. To enhance this interactivity, within this study, the surface of PCL NFs was first modified by acrylic acid plasma polymerization. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirmed that the plasma process did not damage the NFs. Water contact angle (WCA) and zeta potential measurements showed a significant wettability increase and surface charge decrease, respectively. X-ray photoelectron spectroscopy (XPS) confirmed that the NFs were coated with a plasma polymer containing O-based functional groups, which could be related to the aforementioned changes in surface wettability and charge. Additionally, a post-plasma grafting step of ethylene diamine on the surface carboxylic acid groups was performed to investigate the influence of COOH-groups on bone marrow mesenchymal stem cell (BMST) adhesion and proliferation. WCA, zeta potential and XPS measurements confirmed the successful conversion of carboxylic acid into primary amine groups, while SEM indicated that the NF morphology did not change upon the reaction. PCL NFs subjected to this post-plasma grafting evoked the best BMST behaviour, indicating that minor changes in the surface chemistry can have a significant effect on cell-biomaterial interactions. |
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Highly-energy efficient oxidation of MWCNT with nanosecond pulsed dielectric barrier discharge plasma |
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M.K. Daletou, C.A. Aggelopoulos |
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Greece |
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https://doi.org/10.1016/j.apsusc.2021.150139
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• Nanosecond pulsed (NSP) dielectric barrier discharge plasma used to oxidize MWCNT.
• Successful NSP-plasma modification with high energy efficiency (~200 g-MWCNT/kWh). • Higher concentration of defects/oxygen groups by NSP plasma compared to HNO3 oxidation. • Similar percentage of introduced CO groups by HNO3 and NSP plasma. • Preferential decoration with CO groups (e.g. hydroxyl) by NSP plasma. |
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Carbon nanotubes constitute a unique class of materials with intriguing properties related to their structure. In most cases, their effective use requires a change in their surface chemistry. The most common functionalization is oxidation, introducing oxygen-based groups onto the outer tube walls. As reported herein, such functionalization can be achieved conveniently by means of cold plasma (CP) discharge driven by high voltage nanosecond pulses (NSP), which offers a rapid, controllable, non-wet and less destructive process compared to the chemical treatment method (e.g. with nitric acid). It is notable that compared to other plasma discharge types (e.g. AC-driven), the energy efficiency of the NSP is seriously increased showing the potential for industrial grade processing. MWCNT were treated under various CP operational parameters and thoroughly characterized in terms of surface elemental composition, morphological and physicochemical properties. Despite the validation of the successful modification, a correlation is made between the CP treatment time and pulse voltage with the final degree and type of functionalization, as well as the overall properties of the materials. The combinatorial interpretation of the obtained characterization data allowed a deeper understanding of the functionalization mechanism and showed the possibility to control the amount and type of functionality to suit the application. |
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The adhesion of epoxy treated by microwave oxygen plasma |
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Lai Fan Choong, Kuan Yew Cheong, Sivakumar Ramakrishnan, Ahmad Faiz Roslan |
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Malaysia |
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https://doi.org/10.1016/j.apsusc.2021.150224
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• Shear strength of un-aged and aged epoxy for up to two months as a function of plasma power was investigated.
• Shear strength of aged (up to two months) oxygen plasma treated epoxy with silicone increased significantly. • Hydrophobic recovery was observed after ageing but contributed minimal effect on the shear strength. • 300-W plasma-treated epoxy produced the highest shear strength with the lowest adhesive failure percentage. • Increment of LMWOM that formed cross-links with underlying polar groups in epoxy contributed to enhancement of the strength. |
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Strong adhesion between epoxy and silicone is essential for optoelectronic packaging. The adhesion of epoxy can be enhanced by microwave plasma treatment in oxygen flow. However, the plasma effect is time dependent. The shear strength of un-aged and aged epoxy for up to two months was systematically investigated as a function of plasma power (200–600 W) with different surface analysis tools. The shear strength between epoxy and silicone assembly was correlated with surface wettability, chemical, and structural properties. 300-W plasma-treated epoxy revealed the highest shear strength and the factors contributing to the improved strength were identified. The phenomenon of hydrophobic recovery was recorded after ageing, which had minimal effect on the reduction of shear strength. By keeping the plasma-treated surface for up to two months, a significant increment of shear strength was demonstrated below one week of ageing. Beyond that, a slight deterioration of the strength was observed but the reduction was still higher than the un-aged surface. The reasons behind of these observations have been elucidated and justified. |
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Plasma electrolytic oxidation as an effective tool for production of copper incorporated bacteriostatic coatings on Ti-15Mo alloy |
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Katarzyna Leśniak-Ziółkowska, Alicja Kazek-Kęsik, Krzysztof Rokosz, Steinar Raaen, Agnieszka Stolarczyk, Małgorzata Krok-Borkowicz, Elżbieta Pamuła, Wojciech Simka |
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Poland, Norway |
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https://doi.org/10.1016/j.apsusc.2021.150284
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• Ti-15Mo alloy surface was treated via plasma electrolytic oxidation.
• Insoluble Cu3(PO4)2 particles were used for the first time as PEO bath additives. • A successful incorporation of copper into oxide coatings was confirmed. • Bacteriostatic properties against S. aureus and E. coli were established. • Cytocompatibility was determined using MG-63 osteoblast-like cells tests. |
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This report describes the plasma electrolytic oxidation (PEO) treatment of Ti-15Mo alloy surfaces in baths containing 0.1 M Ca(H2PO2)2 with different insoluble copper-based additives: CuO or Cu3(PO4)2. The aim of this work was to fabricate oxide coatings with bacteriostatic and cytocompatible properties. The surface morphology, roughness, and wettability (based on dynamic water contact angle measurements) of the oxide coatings were evaluated. Additionally, the presence of copper compounds and bioactive calcium and phosphorus in the investigated oxide coatings was confirmed using various spectroscopic and crystallographic techniques. The highest copper concentration (3.5 at.%) was detected in the oxide layer obtained using a PEO suspension bath comprising Cu3(PO4)2 and Ca3(PO4)2. The oxide coating generated from a PEO bath containing CuO had the lowest copper concentration (0.1 at.%). The bacteriostatic properties of the obtained Cu-doped oxide layers were established based on bacterial adhesion tests using Gram-positive Staphylococcus aureus (ATCC 25923) and Gram-negative Escherichia coli (ATCC 25922). On the Cu-incorporated surfaces, the number of surface-adhered bacterial colonies was ~10–100 times lower than on the reference Ti-15Mo surface, and ~105 times lower than on tryptic soy broth medium. The materials’ cytocompatibilities were confirmed through tests with MG-63 osteoblast-like cells. |
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Application of combined transfer learning and convolutional neural networks to optimize plasma spraying |
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Jinwei Zhu, Xinzhi Wang, Luyao Kou, Lili Zheng, Hui Zhang |
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China |
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https://doi.org/10.1016/j.apsusc.2021.150098
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• Transfer learning is used to model spraying reverse process with different material.
• Trained CNN model can predict spraying process parameters according to particles. • Transfer learning method solves problem of insufficient high-quality training data. |
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Deep transfer learning can make full use of pre-trained neural networks and has been used in many cases with limited sample data. In this work, parameter-transfer learning was implemented to model the relationship between process control parameters and in-flight particle behavior. Six different parameter-transfer learning models were designed to fine-tune the variables of the convolutional neural network (CNN) model pre-trained with a dataset of yttria-stabilized zirconia (YSZ) particles. Then transfer learning models were trained with the new dataset obtained from simulation results of NiCrAlY particles and the losses of different models in the training set and test set were compared. Results indicate that the method in which the entire pre-trained CNN model was fine-tuned, combined with a decreasing learning rate, exhibited the lowest loss in the training dataset and the highest testing accuracy. Particle status distributions obtained from the control parameters predicted by the transfer learning model were found to be in good agreement with the corresponding designed target values. |
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Deposition of zirconium oxide using atmospheric pressure plasma enhanced chemical vapor deposition with various precursors |
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Dhruval Patel, Lucia Bonova, Zachary Jeckell, D. Eitan Barlaz. Santanu Chaudhuri, Daniel V .Krogstad, David N. Ruzic |
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USA, Slovakia |
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https://doi.org/10.1016/j.tsf.2021.138815
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• Atmospheric plasma deposition of zirconia thin films.
• Liquid droplet precursor delivery for plasma deposition. • Non-thermal decomposition of nitrate salt solutions. |
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Plasma based processes, if applied under controlled conditions, can replace harmful liquid effluents produced today in manufacturing for cleaning and surface protection of metals. In this work, an atmospheric pressure plasma process has been demonstrated to deposit zirconium oxide from three different precursors, namely zirconium tetra-tert butoxide, zirconium acetylacetonate and zirconium oxynitrate hydrate. Of these, the zirconium acetylacetonate and zirconium oxynitrate hydrate deposition processes resulted in conformal thin films. Continuous 115 nm thick zirconium oxide coatings could be deposited from zirconium acetylacetonate, although heavy carbon contamination was observed. In contrast, coatings deposited using zirconium oxynitrate hydrate as a precursor has an approximate thickness of 518 nm, a Zr:O ratio in the bulk of 1:2.2, and no nitrogen or carbon contamination. This study shows that zirconia films can be deposited using atmospheric pressure plasma and the films should be explored further as surface treatments for corrosion protection . |
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Green synthesis of Ag/g-C3N4 composite materials as a catalyst for DBD plasma in degradation of ethyl acetate |
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Xu Deng, Dianya Zhang, Siheng Lu, Teng Bao, Zhimin Yu, Chengxun Deng |
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China |
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https://doi.org/10.1016/j.mseb.2021.115321
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• The application of DBD plasma technology to industrial waste gas treatment has made great progress, and gradually gained wide attention in the field of air purification.
• By combining DBD treatment technology with photocatalytic technology, which effectively reduces energy consumption. In the process of collaborative treatment, the final products are non-toxic inorganic small molecules , with few and harmless byproducts. • The catalytic properties of Ag/g-C3N4 photocatalysts prepared by chemical oxidation, photoreduction deposition and ultrasonic calcination were investigated. |
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An Ag/g-C3N4 composite was successfully synthesized through an ultrasonic-calcination process. The catalyst was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and ultraviolet visible absorption spectroscopy (UV–Vis) analyses. The results showed that Ag supported on g-C3N4 was highly dispersed, and the number of active sites increased. Ag/g-C3N4 was applied as a catalyst to dielectric barrier discharge (DBD) plasma for ethyl acetate (EA) degradation. The Ag loading improved the response range of g-C3N4 to visible light and increased the photocatalytic performance. The infrared spectrum analysis of exhaust gas indicated that the main degradation products of EA were CO, CO2, ozone (O3), and NO2. DBD coupled with the catalyst not only elevated the degradation efficiency of EA as well as the mineralization ratio of EA, but also reduced the content of O3 and abated secondary pollution. |
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Characteristics of magnesium phosphate coatings formed on AZ31 Mg alloy by plasma electrolytic oxidation with improved current efficiency |
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Anawati Anawati, Efrina Hidayati, Hasna Labibah |
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Indonesia |
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https://doi.org/10.1016/j.mseb.2021.115354
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• High current efficiency was obtained at 800 A.m−2.
• Incorporated Na in the coating played role in the corrosion mechanism. • The PEO coating enhanced surface hardness by fivefold. • The corrosion resistance improved by two orders magnitude. |
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A combination of short processing time and high current density is proposed to enhance the current efficiency of the plasma electrolytic oxidation (PEO) process. Magnesium phosphate coating was synthesized on AZ31 Mg alloy using the PEO method for 3 min at a current density of 600, 800, and 1000 A.m−2. The current efficiency was predicted by the mass gain. The hardness and corrosion behavior were investigated by micro-Vickers hardness and electrochemical measurements, respectively. The resulting magnesium phosphate coatings enhanced the specimen hardness five times and improved the corrosion resistance by two orders of magnitude. The efficiency of the PEO process was relatively high in the range 21.3–53.3%. The highest efficiency was attained at 800 A.m−2, where an intense micro-arc dominated the PEO process over initial sparking and post arcing. The proposed parameter proved to be beneficial in improving the efficiency of the PEO process. |
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Microhardness, compression performance and high-temperature tribological properties of Ti2AlNb-silver self-lubricating composite
Mikrohärte, Druckverhalten und tribologische Eigenschaften unter hoher Temperatur eines selbst schmierenden Ti2AlNb-Silber-Verbundwerkstoffes |
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Y. Gao, S. Zhao, W. Wang, H. Zhou, Q. Wang |
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China |
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https://doi.org/10.1002/mawe.202000251 |
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The Ti2AlNb-based self-lubricating composite material reinforced with silver particles of 0 wt% to 15 wt% was prepared by spark plasma sintering, and the microhardness, compression performance and high-temperature tribological properties were investigated. The results show that the silver is distributed in the Ti2AlNb matrix as small islands. The microhardness reaches the maximum at 5 wt% silver content but then decreases sharply. The compressive strength is reduced due to the silver-rich areas have become the initiation points of cracks, and the softening of silver at high temperatures intensifies the process. The friction coefficient and wear rate of the composite material at 500 °C are significantly reduced by silver, and the lubrication mechanism is attributed to the synergistic effect of silver and oxides. |
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Plasma electrolytic oxidation of copper in an aluminate based electrolyte with the respective additives of Na3PO4, NaH2PO4 and NaH2PO2 |
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Yulin Cheng, Binjian Wie, Yuanyuan Liu, Yingliang Cheng |
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China |
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https://doi.org/10.1016/j.apsusc.2021.150477
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• Plasma electrolytic oxidation of copper is first reported in an aluminate electrolyte.
• The additives of sodium phosphates/ hypophosphite are critical to the PEO behavior. • An initial layer of AlPO4 and Al2O3 (AAP) favors the stable discharges with NaH2PO4 as additive. • Hypophosphite reduced original passive film on Cu, leading to deposition of Cu(OH)2. • Cu(OH)2 and AAP re-passivate Cu and coatings were ultimately formed in the case of NaH2PO2. |
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Plasma electrolytic oxidation of copper is first investigated in an aluminate-based electrolyte using trisodium phosphate (TP), sodium dihydrogen phosphate (DP) and sodium hypophosphite (HP), respectively, as additives. Black coatings can be successfully formed in the electrolytes of DP and HP. Detailed characterizations show that an initial thin layer of aluminum phosphate and alumina (AAP) was formed on cooper in DP electrolyte, which helps the fast establishment of plasma discharges, leading to successful coating formation. The AAP layer also formed in the electrolyte with TP as additive, but the AAP layer may be too thin to ensure stable plasma discharges. The coating formation mechanism is drastically different in HP: pitting corrosion along with loose Cu(OH)2 deposition occurs at initial stage, which may be a dual effect of local acidification and the destruction of the passive layer by the reducing hypophosphite ions. However, the deposited Cu(OH)2 and the subsequent formation of AAP layer may re-passivate the copper surface and provide an insulating layer for plasma discharging and coating formation. Optical emission spectroscopy (OES) and Mott-Schottky tests have also been used to investigate the features of plasma discharges and the semiconductor properties of the coatings, respectively. |
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Directly grown Te nanowire electrodes and soft plasma etching for high-performance MoTe2 field-effect transistors |
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Daehan Choi, Donghwan Kim, Yonghee Jo, J.H. Kim, Euijoon Yoon, Hyo-Chang Lee, TaeWan Kim |
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Republic of Korea |
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https://doi.org/10.1016/j.apsusc.2021.150521
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• The vdWs epitaxy of merged t-Te NWs on 2H-MoTe2 atomic layers by MOCVD.
• Subsequently, isolation of t-Te NWs electrodes was achieved by soft plasma etching. • Directly grown merged t-Te NWs reduce the contact resistance of the 2H-MoTe2 atomic layers. • This provides a record high mobility of 544 cm2/V·s for t-Te NWs/2H-MoTe2 back-gated FETs. |
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Contact tailoring for two-dimensional (2D) transition metal dichalcogenides (TMDs) to achieve high-performance devices remains a challenge. Fermi-level pinning at 2D TMD–metal contacts leads to a Schottky barrier for contacts. In addition, when there are no dangling bonds between 2D TMDs and contacts, the contact resistance increases. In this study, Te nanowire (NW) contacts were employed for a MoTe2 p-channel of enhancement mode field-effect transistor (FET). The Te NWs were directly grown on 2D MoTe2 film by metal–organic chemical vapor deposition and selectively etched by a soft plasma etching technique for contact isolation. Using t-Te NW contacts on three-atomic-layer MoTe2, a highly effective field-effect mobility of 543.9 cm2/Vs, as well as ohmic contacts and atomic hybridization, was achieved. These results of t-Te NW electrodes provide a novel device structure for p-type 2D TMD transistors with excellent performances. Further, they offer a practical guideline for wafer-scale 2D TMD-based high-performance electronics and optoelectronics. |
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Aging of plasma-activated carbon surfaces: Challenges and opportunities |
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Euth Ortiz-Ortega, Samira Hosseini, Sergio O. Martinez-Chapa, Marc J. Madou |
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Mexico, USA |
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https://doi.org/10.1016/j.apsusc.2021.150362
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• Aging effect or reorientation phenomenon is a time-induced loss of surface activity.
• Physicochemical properties of plasma-treated carbons change with time. • Aging impacts the performance of plasma-treated carbons in different applications. • Different characterization techniques can detect signs of aging on carbon platforms. • Plasma treatment parameters and storage conditions can alter aging and its speed. |
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Plasma-activated carbon surfaces demonstrate an immediately enhanced surface energy, wettability, and roughness and perform considerably well in their intended applications. However, as the time progresses, plasma-treated carbon materials rapidly lose the generated features and functions as a result of aging. While plasma-generated surface functional groups reorient themselves in an attempt to occupy lower states of energy, the surface begins to also suffer from a brief shelf life that severely impacts its performance in various disciplines. This time-induced decay of the surface that manifests as the gradual loss of surface properties and functionalities is rarely mentioned or discussed in the literature. The main contribution of plasma treatment is to produce activated and functional platforms that can serve several applications including environmental monitoring, bio-diagnosis, food quality control, and extreme point-of-care. To reach the hands of final users at any of these destinations, plasma-activated carbon platforms have to remain active and stable over an acceptable period of time to fulfill their purpose. The current review article is an effort to garner the attention of the scientific community to this shortcoming and gather all the existing evidences on the aging of plasma-activated carbon platforms. |
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The grain size-dependent control of the phase composition in ion-plasma treated 316L stainless steel |
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V.A. Moskvina, E.G. Astafurova, K.N. Ramazanov, R.S. Esipov, G.G .Maier, S.V. Astafurov, M. Yu. Panchenko, K.A. Reunova, E.V. Melnikov, A.I. Smirnov |
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Russia |
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https://doi.org/10.1016/j.msea.2021.141777
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• 316 L steel with different grain size was modified with ion plasma treatment (IPT).
• Phase composition of IPT-processed steel is grain size-dependent characteristic. • IPT-assisted Fe-γN,C and intragranular Fe4(N,C) prevail in coarse-grained specimens. • Fe-γN,C + Cr(N,C)+Fe-α microstructure is peculiar for fine-grained steel after IPT. |
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We study the influence of different grain size (density of grain boundaries) on the way of phase transformations in the surface layers of 316 L-type austenitic stainless steel under ion-plasma treatment. Using thermomechanical treatments, we fabricated a series of specimens possessing a single-phase austenitic structure, close density of the defects of the crystal lattice and different grain sizes (fine-grained with d ≈ 3–6 μm and coarse-grained with d ≈ 55 μm). These specimens were subjected to ion-plasma surface treatment at 550 ± 10 °C in N2+C2H2+Ar gases mixture to provoke a precipitation hardening. Although fine-grained and coarse-grained specimens possess similar penetration depth of interstitial atoms (N, C) under ion-plasma treatment (≈40–48 μm), the distribution of interstitials and phase composition are different in them. After ion-plasma treatment, specimens with low density of grain boundaries (coarse-grained structure) maintain a high level of N, C atoms in the solid solution of austenite (a = 0.3653–0.3674 nm) with a strip-like arrangement of Fe4(N,C) particles within grains, while precipitation of Cr(N,C) phase is suppressed. For these specimens, tensile diagrams have the extended linear stages typical of nitrogen-bearing austenitic steels, and the loss of ductility assisted with ion-plasma treatment is the smallest among studied specimens. Ion-plasma treated specimens with high density of grain boundaries (fine-grained structure) are prone to a decomposition of Fe-γN,C phase with the formation of grain-boundary and intragranular Cr(N,C) and Fe-α phases and partial preservation of a solid-solution strengthening of austenite (a = 0.3597–0.3622 nm). Precipitation hardening is more characteristic of these specimens and their flow curves are parabolic. The complex fracture mode of the specimens subjected to ion-plasma treatment is caused by the surface solid-solution strengthening and precipitation hardening. In the surface-hardened region (where the concentrations of N, C atoms are the highest), brittle quasi-cleavage fracture occurs due to the presence of Fe-based and Cr-based precipitates and austenite oversaturated with interstitials. |
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Multilayer graphene and β-Si3N4 whisker-reinforced porous Si3N4 ceramics by spark plasma incomplete sintering |
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Fei Chen, Ke Yan, Jianping Zhou, Yongsheng Zhu, Jun Hong |
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China |
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https://doi.org/10.1016/j.msea.2021.141770
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• Spark plasma incomplete sintering was proposed to fabricate porous Si3N4 ceramics.
• MLG/β-Si3N4w were doped into porous Si3N4 ceramics to advance its strength. • MLG/β-Si3N4w-enhanced Si3N4 ceramics with a porosity of 21% were prepared at 1500 °C. • Hardness of MLG/β-Si3N4w-reinforced porous Si3N4 ceramics reached 2.81 GPa. • Fracture toughness of porous Si3N4-based ceramics was improved to 3.14 MPa m1/2. |
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Combining the advantages of spark plasma sintering (SPS) and incomplete sintering (IS) in preparation of Si3N4 ceramics, the spark plasma incomplete sintering (SPIS) was presented to fabricate porous Si3N4 ceramics. Considering balancing the contradictory relationship between the porosity and toughness, 1 wt% multilayer graphene (MLG) was incorporated into porous Si3N4 ceramics. Meanwhile, for the sake of compensating for the decrease in the hardness of porous Si3N4 ceramics induced by MLG, 0–8 wt% β-Si3N4 whisker (β-Si3N4w) were synergistically added. The element distribution, phase constitutions and microstructures of MLG/β-Si3N4w-reinforced porous Si3N4 ceramics were characterized by energy dispersive spectroscopy (EDS), x-rays diffraction (XRD) and scanning electron microscope (SEM). The effects of β-Si3N4w content on porosity, hardness and fracture toughness of porous Si3N4-based ceramics were analyzed. Results indicated that the porosity of porous Si3N4-based ceramics reached 21%, and then decreased significantly after the β-Si3N4w content exceeded 4 wt%. The hardness of porous Si3N4-based ceramics obtained the maximum value 2.81 GPa when β-Si3N4w was added 8 wt%, which was 31.92% higher than monolithic porous Si3N4 ceramic. The mass transfer, diffusion and fusion induced by β-Si3N4w were considered to be the main responsible for the increase of hardness. The fracture toughness of specimen with 1 wt% MLG and 4 wt% β-Si3N4w was advanced to 3.14 MPa m1/2, which was 15.44% higher than monolithic porous Si3N4 ceramic. The markedly enhanced of the fracture toughness was attributed to the synergistic effects of crack deflection, pull-out and bridging resulted by MLG/β-Si3N4w. |
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Oxidation behavior of dense Yttrium doped B2-NiAl bulk material fabricated by ball milling self-propagating high-temperature synthesis and densified by spark plasma sintering |
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J. Muñoz-Saldaña, A. Valencia-Ramirez, L.A.Castillo-Perea, S. Díaz-De la Torre, L.A. Caceres-Diaz, J.M. Alvarado Orozco, A.L. Giraldo Betancur, U. Schulz |
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Mexico |
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https://doi.org/10.1016/j.surfcoat.2021.127448
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• SHS process parameters by ball milling to prepare highly ordered NiAl-Y powder.
• 7YSZ coated NiAl-Y model alloys to evaluate their furnace cyclic oxidation behavior at 1100 °C. • 0.1–0.5 at.%Y reduce the oxidation kinetics to one third of undoped NiAl mass gain. • Longest TBC lives and lowest spallation rates were achieved on NiAl-1.0 - 1.5 at.%Y/7YSZ. • Y-additions improved oxidation behavior and TBC live respective to undoped NiAl. |
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The effect of Y additions on the oxidation behavior in furnace cyclic tests and its correlation with thermogravimetric analysis of sintered NiAl alloys is here reported. Part of the samples got an EB-PVD 7YSZ coating on top. Highly ordered B2-NiAl intermetallic powder was obtained by self-propagating high-temperature synthesis (SHS) during ball milling of elemental precursors with Y additions in amounts between 0 and 1.5 at.%. The SHS process was optimized to identify the combination of milling parameters that leads to a sharp increase in the reaction temperature for intermetallic synthesis. The tested samples consisted of NiAl-Y buttons densified by spark plasma sintering (SPS). Furnace cyclic testing of the SPS- buttons at 1100 °C showed high resistance to spallation of the 7YSZ top-coat and a significant decrease in its oxide growth kinetics attributed to Y-additions. Contents below 0.5 at.% Y reduce the oxidation kinetics of NiAl exposed to thermal cycles at 1100 °C, while higher Y contents are favorable for a longer TBC life. |
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Fretting wear behavior of nano ZrO2 doped plasma electrolytic oxidation composite coatings on TC21 titanium alloy |
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Kai Zhou, Faqin Xie, Xiangqing Wu, Shaoqing Wang |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127429
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• ZrO2 plasma electrolytic oxidation composite coatings improved fretting resistance.
• Composite coatings inhibited crack initiation and propagation in the partial slip regime. • Composite coatings eliminated delamination wear in the slip regime. |
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Basic and ZrO2 doped composite plasma electrolytic oxidation coatings were prepared on the surface of TC21 titanium alloy. Subsequently, fretting wear tests of these two kinds of coated samples and the substrate alloy against GCr15 steel balls were conducted at 50 μm and 150 μm displacement amplitudes. The morphology, composition, valence states and topography of the fretting wear tracks were characterized and the wear mechanisms were studied. The results indicated that the porosity of the composite coatings was lower than that of the basic coatings, and the microhardness, adhesion strength and toughness were higher. When the fretting was in the partial slip regime (50 μm displacement amplitude), the fretting damage of the three materials was slight. Meanwhile, the cracks and delamination in the microslip zone of the TC21 alloy were not observed in the coated samples. When the fretting was in the slip regime (150 μm displacement amplitude), although the TC21 alloy and basic coatings experienced local wear, there was no significant material loss of the composite coatings, which demonstrated that the composite coatings could improve the fretting wear resistance. |
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Microstructural optimization and anti-wear performance of supersonic atmospheric plasma sprayed nickel based self-lubricating coatings under heavy load |
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Q. Liu, Y. Wang, Y. Bai, Z.D. Li, M.Y. Bao, H. Zhan, N. Liu, Z.D. Chang, Y.S. Ma |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127383
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• Lubricating phases transform into some independent lamellar structures during SAPS.
• Graphite can compensate the loss of MoS2 and improve the fracture toughness. • Graphite-dominated debris transfer layer significantly improves the wear performance. |
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The aim of this work is to explore high-property nickel based self-lubricating coatings to meet the challenge of the increasing demand of heavy load wear condition. Thus, a series of Ni-MoS2/graphite coatings were designed and prepared by supersonic atmospheric plasma spraying. The microstructural evolution of lubricating phases was systematically studied by plasma focused ion beam (FIB) and field-emission transmission electron microscopy (FE-TEM). The results suggested that the lubricating phases, such as graphite and MoS2, can transform into some independent lamellar structures due to their low binding energy. MoS2 phase was easy to decompose into nanoscale Mo with preferred (110) crystal plane at high temperatures, leading to the decrease of self-lubrication property of coatings. Due to the rapid formation of the graphite-dominated debris transfer layer, the coating with approximately 19 vol% graphite showed the longest friction time and the lowest wear rate. The graphite with a large size range (1–60 μm) not only effectively compensated the loss of MoS2 caused by the thermal decomposition, but also improved the density and fracture toughness of coatings. In addition, the content of monoclinic β-MoO3 was significantly decreased with the addition of graphite, which further improved the tribological properties of the coatings. This work provided an in-depth understanding for the development of composite coatings with high anti-wear performance under heavy load. |
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Superhydrophobic micro-tube fabricated via one-step plasma polymerization for lossless droplet transfer |
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Shuai Huang, Yayu Zhang, Zeming Wang, Faze Chen |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127272
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• A new one-step approach for the preparation of superhydrophobic film in transparent Teflon or glass micro-tubes has been developed.
• Unapparent damage was done to the micro-tube by APCP and the reduction in transparency of the micro-tube was less than 5%. • Using the as-prepared superhydrophobic micro-tube as the core component, the lossless droplet transfer platform based on the non-contact ultrasonic driving was set up. |
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Lossless droplet transfer via micro-tube is urgently demanded in the fields of microfluidics and biomedicine. However, as the core component for the construction of lossless droplet transfer platform, the fabrication of low-adhesion micro-tubes is still a longstanding challenge. To solve the problems such as complex reaction procedures, difficult-to-clean reaction products, non-uniform wettability, etc. during the synthesis of the low-adhesion micro-tubes, a new one-step approach for the preparation of superhydrophobic micro-tubes has been developed, with the help of atmospheric pressure cold plasma (APCP) deposition technology. This method can break through the limitations of micro-tube materials, and achieve the preparation of superhydrophobic surface in glass and transparent Teflon tubes using a lab-made plasma generator. The mechanism of the superhydrophobic surface preparation by APCP deposition involves the formation of a micro-nano composite structure and hydrophobic functional groups. The results point out that the inner wall of the superhydrophobic micro-tube has good and consistent wettability, and uniform morphology. The reduction in transparency of the micro-tube was less than 5% within the wavelength range of 400 nm~1100 nm. Using the as-prepared superhydrophobic micro-tube as the core component, the lossless droplet transfer platform based on the non-contact ultrasonic driving was set up. Finally, the lossless droplet transfer under extreme conditions like in vertical micro-tubes, curve micro-tubes, spiral micro-tubes, using high-speed liquid feed at 850 μL/min was successfully achieved, with the transportation distance reaching hundreds of millimeters. With excellent performances, the lossless droplet transfer platform promises great potential applications in the fields like microfluidics, biomedicine and advanced device design. |
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Improved in-vitro corrosion performance of titanium using a duplex system of plasma electrolytic oxidation and graphene oxide incorporated silane coatings |
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Behnaz Hamrahi, Benyamin Yarmand, Abouzar Massoudi |
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Iran |
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https://doi.org/10.1016/j.surfcoat.2021.127558 |
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• The surface roughness and hydrophilicity reduced by preparing PEO-Silane-GO.
• The in-vitro corrosion stability of PEO-Silane-GO promoted upon 14 days. • The precipitated calcium-phosphate on the duplex coating system increased slightly. |
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In this study, pure and 0.1 wt% graphene oxide (GO) incorporated silane layers were deposited on plasma electrolytic oxidation coated titanium as biocompatible sealants using the sol-gel method. Thereafter, their corrosion protection performance was investigated during 14-day in-vitro immersion. The characterization revealed that the silane layers with amorphous structure covered surficial inherent defects of plasma electrolytic oxidation coated titanium and decreased surface roughness as well as hydrophilicity. Further, the embedment of GO nanosheets improved the integrity of the silane layer and caused a reduction in work of adhesion and surface free energy. Accordingly, the chemical affinity and dissolution kinetics of plasma electrolytic oxidation coated titanium in simulated body fluid (SBF) weakened such that the polarization resistance rose to 956.33 and 2213.69 k
Ω ·cm2 after applying pure and GO incorporated silane layers, respectively. The electrochemical impedance spectroscopy demonstrated that the pure silane layer promoted the stability of the plasma electrolytic oxidation coated titanium from about 3 to 7 days. Also, the GO incorporated silane layer provided better stability to the end of 14 days and its protective performance was higher in the first 3 days. The SBF immersion test clarified that the bioactivity of the silane layers was higher than that of titanium due to the induction of particulate calcium-phosphate precipitations. |
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Comparison of the microstructural characteristics and electrical properties of plasma sprayed Al2O3 and Al2O3–Ca2SiO4 coatings immersed in deionized water |
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Fang Shao, Yin Zhuang, Jinxing Ni, Jing Sheng, Huayu Zhao, Shunyan Tao, Kai Yang |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127530
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• Plasma sprayed Al2O3 and Al2O3–Ca2SiO4 coatings were successfully prepared.
• Complete characterization of as-sprayed and water immersed coatings. • Al2O3–Ca2SiO4 coatings were self-sealed during the immersion process. • The introducing of Ca2SiO4 in Al2O3 coatings can improve the electrical resistivity. |
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In this study, Al2O3 and Al2O3–Ca2SiO4 coatings were deposited by atmospheric plasma spraying technique. Immersion experiments were performed in deionized water for 1 day and 10 days. The composition and microstructure evolutions of pure and composite coatings with immersion time were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). Microhardness, roughness and insulation resistance of as-sprayed and immersed coatings were evaluated. In particular, a temperature of ~25 °C and various humidity levels (~10% RH, ~42% RH, ambient humidity and ~95% RH) were applied in the test of electrical resistance. Relationships between mechanical and electrical properties with coating characteristics were discussed. It is shown that the introducing of Ca2SiO4 in Al2O3 coatings can improve the electrical resistivity under low, middle and ambient humidities, especially after 1 day of immersion. Taking into account the insulation resistance values and mechanical properties of the considered coatings, the plasma sprayed Al2O3–5 wt% Ca2SiO4 is perhaps a promising material for industrial applications. |
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Characterization of the combination of microwave and laser ablation plasmas |
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Enrique Camps, E. Campos-González, C. Rivera-Rodríguez |
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Mexico |
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https://doi.org/10.1016/j.surfcoat.2021.127509
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• An experimental arrangement allowing the combination of two types of plasmas was implemented (the hybrid system).
• OES measurements showed that this hybrid system produces highly excited plasma. • High quality AlN thin films with low oxygen content can be produced in the hybrid system. • The hybrid system allows introducing metallic elements in the microwave discharge without the use of corrosive substances. |
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The main aim of the present work is to report on the study of the combination of continuous plasma, formed by a microwave electron cyclotron resonance (ECR) discharge and the pulsed plasma obtained by the laser ablation of a solid target. Such arrangement allows studying the formation of materials in the form of thin films making use of the relatively high densities of the microwave discharge and the wide range of ion energies produced in the pulsed laser ablation plasmas. With this arrangement it is possible to deposit thin films of materials that in the usual microwave discharge require the use of dangerous and corrosive substances, as the required element is obtained from a pure solid target. Moreover, as the laser ablation process is carried out in plasma as the background gas, instead of a neutral gas, the presence of contaminants, such as oxygen can be significantly reduced. For the purpose of the present paper a nitrogen microwave ECR discharge was combined with the plasma created during the ablation of an aluminum target, in order to deposit AlN thin films. Plasma parameters were measured by a Langmuir probe, and the chemical species contained in the plasma were analyzed by optical emission spectroscopy (OES). The optical properties and chemical composition of the AlN thin films are reported. |
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Atmospheric pressure plasma deposition of eugenol-derived film on metallic biomaterial for suppression of Escherichia coli and Staphylococcus aureus bacterial biofilm |
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Tsegaye Gashaw Getnet, Milton E. Kayama, Elidiane C. Rangel, Iolanda C.S. Duarte, Gabriela F da Silva, Nilson C. Cruz |
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Brazil, Ethiopia |
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https://doi.org/10.1016/j.tsf.2021.138833
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• Eugenol-derived film is grown by dielectric barrier discharge plasma.
• Coating increased the substrate's roughness, hydrophilicity, and surface energy. • The monomer's mean functional group was largely retained in the deposited films. • Bacterial adherence was reduced on the biofunctional coating surfaces. |
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Eugenol (4-Allyl-2‑methoxy phenol) is widely used as a condiment and bactericidal coatings for food packing and biomaterials. We have investigated the deposition and characterization of eugenol-derived films (EDF) on stainless steel surfaces deposited using atmospheric pressure plasma discharge for suppression of Escherichia coli and Staphylococcus aureus bacterial adhesion and proliferation. The thickness of the deposited films was in the range of 1,000 to 2,500 nm with a roughness up to 800 nm. Infrared spectra showed that the EDF preserves the hydroxyl and aromatic groups found in liquid eugenol, which is a key feature for the antibacterial activity of the film. X-ray photoelectron spectroscopy analysis has revealed increased oxygen content with the deposition time. Scanning electron microscopy has shown that the entire surface of the substrate is covered by a circular structure approximately 10 to 20 µm in diameter. Wettability analysis revealed an increase in the hydrophilicity of the surface after the deposition. Microbiological evaluation of bacterial growth, revealed that the surfaces inhibited the adhesion and proliferation of E. coli and S. aureus by more than 78 and 65%, respectively, while in the untreated samples the growth was greater than 90% for both microbes in comparison with polystyrene plates used as a positive control. Therefore the eugenol thin film deposited by this method was effective for biofilm suppression with a potential application for biocompatible material coating processes. |
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Investigation on the electron density and temperature in a nanosecond pulsed helium plasma jet with Thomson scattering |
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Fan Wu, JiaYin Li, YuBin Xian, Xiao Tan, XinPei Lu |
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China |
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https://doi.org/10.1002/ppap.202100033 |
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Diagnostic of spatiotemporal distribution of the electron density and temperature of atmospheric pressure plasma jets is a difficult task, as Thomson scattering, which is the most used measurement, suffers from the stray light induced by Rayleigh scattering. In this paper, a new strategy is reported to restrain the stray light in Thomson scattering. With a physical mask placed at the output of a single spectrometer, the scattering signal is obtained with a relatively high ratio of signal to noise. The electron density in a pulsed kHz-driven atmospheric plasma jet interacting with a dielectric target is measured by using this method. A donut-shaped distribution of electron density is observed at an axial position 1 mm away from the nozzle. The radius of the ring structure decreases with the reduction of the gas flow rate. The electron density reaches a maximum of about 4.5 × 1020 m−3 at a delay time of 150 ns from the onset of the pulse. A similar time relationship between the electron density and plasma emission intensity is also identified. Higher applied voltage leads to a faster increasing and a higher peak value of the electron density. Pulse width shows little impact on the generation and decay of electrons. |
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Unique combination of spatial and temporal control of maleic anhydride plasma polymerization |
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Syrine Jebali, Aissam Airoudj, Isabelle Ferreira, Dirk Hegemann, Vincent Roucoules, Florence Bally-Le Gall |
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France, Schweiz |
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https://doi.org/10.1002/ppap.202000244 |
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The chemical properties of plasma polymers strongly depend on the operating conditions of plasma polymerization and impact their final application. Low-pressure pulsed plasma polymerization of maleic anhydride was investigated at different positions from the glow discharge in a unique 1-m-long reactor. Based on a macroscopic approach, the growth kinetics of maleic anhydride plasma polymerization was investigated, leading to the identification of three growth regimes. The calculation of apparent activation energies associated with each regime and each position and the chemical characterization of polymer films by X-ray photoelectron spectroscopy and attenuated total reflection–Fourier-transform infrared as well as optical emission spectroscopy analyses of plasma species formed during deposition strongly indicate a combined spatial and temporal influence on the plasma polymerization kinetics. |
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Investigation of NH4NO3 formation by air plasma and wasted ammonia |
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Yu Zhu, Zilan Xiong, Mengqi Li, Xingyu Chen, Chen Lu, Zhenping Zou |
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China |
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https://doi.org/10.1002/ppap.202000223 |
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This study investigated NH4NO3 formation by air plasma and NH3 in three different reaction modes for nitrogen fixation and environmental protection. A DC-driven needle–needle discharge was used. We found that NH4NO3 could be effectively formed by directly mixing NO x (generated by air discharge) and NH3 in Mode 1. In Mode 3, when discharging in the air/NH3 mixture, no NH4NO3 was detected. However, in Mode 2, when discharging in the NO x /air/NH3 mixture, NH4NO3 was first formed and then subsequently decreased as the discharging time increased. NH4NO3 was identified by white smoke observation and gas/aqueous-phase Fourier-transform infrared spectroscopy (FTIR) analysis. Stable NH4NO3 formation may be affected by self-thermal decomposition and NH3 decomposition through discharge. |
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Al/SiC nanocomposites with enhanced thermomechanical properties obtained from microwave plasma-treated nanopowders |
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M.K. Kutzhanov, A.T. Matveev, D.G. Kvashnin, S. Corthay, A.G. Kvashnin, A.S. Konopatsky, A.V. Bondarev, N.A. Arkharova, D.V. Shtansky |
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Russia, Czech Republic |
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https://doi.org/10.1016/j.msea.2021.141817
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• Al/SiC composites obtained by high-energy ball-milling and spark plasma sintering.
• Microwave Ar plasma treatment of nanoAl/nanoSiC powder mixtures prevents SiC agglomeration. • Plasma processing leads to uniform distribution of SiC nanoparticles in Al matrix. • Adding 10% SiC significantly increases composite strength at room and elevated temperatures. • Silicon vacancies and oxygen atom impurities at Al/SiC interface increase critical shear stress. |
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Al-based composites with enhanced thermomechanical properties are in high demand. However, obtaining a uniform distribution of the strengthening phase in the metal matrix and achieving a strong metal/ceramic interface is still a great challenge. In this work, nanoAl/nanoSiC powder mixtures after high-energy ball milling were treated with Ar microwave plasma. Plasma processing was designed to remove the initial oxide film covering Al nanoparticles (NPs) and adsorbed impurities from the surface of SiC NPs, improve the wetting of SiC with Al melt, prevent SiC nanoparticle agglomeration, and ensure their uniform distribution in the metal matrix. During plasma treatment, Al/SiC composite particles were obtained, which were subsequently utilized as ready-made structural blocks with uniformly distributed reinforcing SiC NPs to obtain Al/SiC composites with 5, 10, and 30 wt% of SiC. Spark plasma sintered Al/SiC composites using plasma-treated powder mixtures showed approximately 20% higher tensile strength. The addition of 10% SiC led to an increase in hardness by 480% (145 HV), tensile strength by 70% (317 MPa) and 95% (238 MPa) at 25 °C and 500 °C, respectively, compressive strength by 135% (578 MPa), and wear resistance by 35–50%. The effect of point defects at the Al/SiC interface, such as impurity oxygen atoms and Si monovacancies, on the binding energy and temperature-dependent critical shear stress at the interface was assessed using molecular dynamics simulations with machine learning interatomic potentials. Our study demonstrated that the plasma-chemical treatment of Al/SiC powder mixtures is a promising approach for improving the thermomechanical properties of the Al/SiC composites. |
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High strength conductive bulk Cu-based alloy/metallic glass composites fabricated by spark plasma sintering |
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Weizong Bao, Han Yan, Jie Chen, Guoqiang Xie |
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China |
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https://doi.org/10.1016/j.msea.2021.141919
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• The bulk CuCrZr alloy/CuZrAl metallic glass composites (CA/CMGCs) with both high strength and high conductivity was prepared by ball milling and SPS process.
• The CuZrAl MG provides high strength and the CuCrZr alloy contributes greatly to the plasticity and conductivity of the CA/CMGCs. |
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High strength conductive materials are the basic materials in the fields of electronic communication and mechanical manufacturing. In this study, we synthesize high-strength and high-conductivity bulk CuCrZr alloy/CuZrAl metallic glass composites (CA/CMGCs) via spark plasma sintering (SPS) process. The effect of CuZrAl metallic glass (MG) content on the mechanical and electrical properties of the composites is investigated. The CuZrAl MG provides high strength and the CuCrZr alloy contributes significantly to the plasticity and conductivity of the composites. In addition, it is demonstrated that a good bonding state between metallic glass and crystalline alloy contributes primarily to the high strength and high conductivity of the bulk CA/CMGCs. This study provides insights into the untapped potential of high-strength and high-conductivity Cu matrix crystal/amorphous composites. |
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Effect of Al content on the microstructure and mechanical properties of γ-TiAl alloy fabricated by twin-wire plasma arc additive manufacturing system |
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Lin Wang, Chen Shen, Yuelong Zhang, Fang Li, Ye Huang, Yuhan Ding, Jianwen Xin, Wenlu Zhou, Xueming Hua |
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China |
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https://doi.org/10.1016/j.msea.2021.142008
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TiAl alloys are considered as promising high temperature structural materials. However, the inherent brittleness makes it difficult to be processed. In the present research, TiAl alloys with different Al content are fabricated successfully using an innovative twin-wire plasma arc additive manufacturing system. The effect of Al level on the phase composition, microstructure characteristics, microhardness and tensile properties of as-deposited TiAl alloy is investigated in detail. The results show that the α2 phase content exhibits increase tendency with the decrease of Al level, and the α2 phase content is higher in the top region than that in the middle region. The tetragonal ratio c/a of γ phase tends to reduce with the decrease of Al content. The microstructure characteristics also present obvious difference for as-deposited TiAl alloys. The lamellar spacing gradually decreases with the decrease of Al concentration. With decreasing Al level, the microhardness of alloy tends to increase. In addition, the as-deposited Ti-48 Al (at.%) alloy exhibits much better tensile properties than other TiAl alloys due to optimum microstructure characteristics. The findings provide a valuable reference for additively manufactured TiAl alloy with proper composition ratio. |
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Spark plasma sintering and mechanical properties of tungsten carbide in presence of Ni and Al2O3 binders |
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Aida Najmi Azar, Leila Nikzad, Azam Moosavi |
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Iran |
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https://doi.org/10.1016/j.msea.2021.141968
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The current study was conducted to investigate the effect of nickel (Ni) and alumina (Al2O3) binders on the sintering behavior, microstructure, and final mechanical properties of WC-based cermets consolidated by the spark plasma sintering (SPS) method. To examine this, batches were mixed according to WC86-(Al2O3)14-x Nix where X= 0, 3, 6 wt % and WC94-(Al2O3)6-x Nix with X= 0, 3; applying high-energy ball milling. Sintering was carried out at temperatures of 1350 ◦C and 1500 ◦C. The results revealed that without Ni, in WC-6wt% Al2O3 and WC-14 wt% Al2O3 samples, the relative density and the fracture toughness were less than 94% and 7 MPa m 1/2, respectively. However, with Ni addition and its partial replacement in the microstructure, not only sintering temperature decreased to 1350 ◦C, but also the obtained relative density was increased to higher than 98% and in the case of WC-3wt%Ni-3wt% Al2O3 cermet, almost full density samples have been achieved. Accordingly, due to better consolidation, this sample exhibited the combination of high strength (1127±53 MPa), high hardness (16.5±0.5 GPa), and proper fracture toughness (15.33 MPa m 1/2). |
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Complex pulse magnetization process and mechanical properties of spark plasma sintered bulk MgB2 |
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Muralidhar Miryala, Sai Srikanth Arvapalli, Naomichi Sakai, Masato Murakami, Hidehiko Mochizuki, Tomoyuki Naito, Hiroyuki Fujshiro, Milos Jirsa, Akira Murakami, Jacques Noudem |
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Japan, Czech Republic, France |
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https://doi.org/10.1016/j.mseb.2021.115390
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• Superior critical current density (Jc) and mechanical properties are observed.
• An eightfold increment in bending strength is observed compared to HIP based bulks. • Trapped field along with local temperature values are systematically discussed. |
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High-density MgB2 bulks with superior mechanical and superconducting properties were fabricated using spark plasma sintering (SPS). The sharp superconducting transition at 37.5 K proved high quality of the superconductors. Critical current density significantly exceeded that of conventionally sintered bulks. Flux pinning diagrams indicated dominance of grain boundary pinning, with peak position at 0.2. SPS bulks showed improved mechanical properties with 8-times higher bending strength compared to dense hot isostatic pressed bulks. Trapped field was measured at 14 K and 20 K, 1 mm above the bulk’s surface, with applied pulse field up to 2 T. A local overheating together with a complex trapped field formation in the MgB2 bulks during pulse-field magnetization were studied to elucidate limitations of Pulse Field Magnetization. |
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Durability of plasma sprayed Thermal Barrier Coatings with controlled properties part II: Effects of geometrical curvature |
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Edward J. Gildersleeve V,Toshio Nakamura, Sanjay Sampath |
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USA |
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https://doi.org/10.1016/j.surfcoat.2021.127671
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• A systematic Furnace Cycle Test (FCT) study of APS 7YSZ TBCs on rod substrates was conducted
• Initial results revealed TBCs on rods yield <10% durability vs. planar disks • Higher porosity TBCs yielded higher durability on rods • The radial stress (unique to rod TBCs) provides the difference in failure mode • The failure mechanisms change when the substrate geometry or bond coat are changed |
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The present investigation elucidates the effects of substrate curvature on the durability of Air Plasma Sprayed (APS) Thermal Barrier Coatings (TBCs). Traditionally, planar disk specimens are utilized in Furnace Cycle Testing (FCT). In most cases, delamination is initiated at the disk's free edge and then propagates along the TBC-bond coat interface. However, in turbine components (e.g., blades/vanes), they lack significant free edges and the coatings are deposited on non-flat surfaces of varying radii of curvature. These geometrical discrepancies imply significant differences in the stress states as compared to planar disk specimens. Therefore, the part geometry inevitably affects the TBC failure mechanisms in the turbine system, and consequently influences TBC durability. Nevertheless, these effects have not been fully explored in the past, despite the anecdotal knowledge which suggests the leading edge of turbine blades to be one of the most common failure/spallation locations.
In this study, representative TBC systems were deposited onto superalloy disks with flat substrate and rods with curved substrate. The experimental results from FCT suggest TBC durability on rods is significantly lower than when sprayed on disks. Furthermore, the durability of TBCs on rods appears to increase with higher porosity, which is contradictory to reported trends for TBCs on disks. In addition, the effects of various bond coats are not consistent with those observed in disks. To clarify the underlying effects of curved geometries, detailed stress analyses were performed. They revealed a state of thermal stresses which is unique to curved geometries. It was found that TBC on rods experience tensile radial stresses as well as tensile hoop stresses during the cooling. These stresses result in a complex interplay in failure processes in rods, which explains the different observed trends in the durability from those obtained with disks. |
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Durability of plasma sprayed thermal barrier coatings with controlled properties part I: For planar disk substrates |
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Edward J. Gildersleeve V, Sanjay Sampath |
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USA |
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https://doi.org/10.1016/j.surfcoat.2021.127678
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• Plasma-sprayed YSZ TBCs were studied systematically for their FCT durability.
• Over 6 years, one YSZ TBC was sprayed and generated reproducible FCT durability. • HOSP and Agglomerated & Sintered TBCs were evaluated for their FCT durability. • Elastic Energy analysis revealed durability trends that were otherwise not obvious. • Flash Thermography showed highly porous TBCs resist constrained sintering. |
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Thermal Barrier Coatings (TBCs) have been qualified for their thermo-mechanical performance and durability using Furnace Cycle Testing (FCT) for decades. FCT provides guidance toward materials and process improvements. Although FCT is a relatively straightforward test, the interpretation can often be subject to uncertainty, making it difficult to link test results directly to engine performance. This is because in FCT, the coating and substrate are isothermally treated, while real turbine components experience strong thermal gradients and time transients. Gradient testing can be time-consuming and expensive, thus FCT tests provide a cost-effective first-order confidence screening for development.
A review of the available literature on Air Plasma Spray (APS) TBC durability by FCT does not reveal consistent trends among processing, microstructure (i.e., porosity), and durability. Furthermore, the available literature does not comprehensively capture the influence of microstructural changes (i.e., sintering) on FCT durability. In this two-part study, APS TBCs were produced with systematically-controlled microstructures, using multiple powder types on different bond-coated superalloy substrates and subjected to different FCT conditions. In Part I, the focus is on disk specimens, where edge-delamination failure predominates, while Part II will address curved surfaces with different failure mechanisms. The FCT results for the systematically produced coatings suggest marginal trends between durability and porosity of APS TBCs, with denser/tougher microstructures providing more durable outcomes, i.e., segmented coatings. One coating was sprayed multiple times over six years and tested in FCT to benchmark the durability testing and coating process reproducibility at Stony Brook. The results were compiled in a unified framework, utilizing published formulations to calculate available elastic strain energy, which serves as a driving force for delamination. The current results highlight a few regimes of FCT performance based on coating toughness, stiffness, and nonlinear elastic parameters. In addition, the benefits and limitations of FCT are discussed in this study. |
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Elastic constants of plasma-sprayed yttria-stabilized zirconia coatings determined via resonant ultrasound spectroscopy coupled with laser-Doppler interferometry |
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K. Adachi, K. Kawamata, H. Waki |
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Japan |
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https://doi.org/10.1016/j.surfcoat.2021.127676
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• All the elastic constants of free-standing YSZ coatings were determined precisely.
• YSZ coatings exhibited degenerate transverse isotropy with inter-splat pores. • Elastic constants provided appropriate information on the coating microstructures. |
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Plasma-sprayed yttria-stabilized zirconia (YSZ) coatings exhibit five independent elastic constants with transverse isotropy owing to splat-based layered structures, including numerous preferentially oriented defects. In this study, we measure all the elastic constants of free-standing YSZ coatings in both as-sprayed and thermally treated conditions from 800 °C to 1300 °C for 2 h. The YSZ coatings were produced via atmospheric plasma spraying under one typical processing condition. The elastic constants are determined using resonant ultrasound spectroscopy coupled with laser Doppler interferometry. This approach allows us to overcome the difficulty of resonant-mode identification caused by the high internal friction of plasma-sprayed YSZ coatings; hence, reliable elastic constant data are obtained. We discovered that the splat-based layered structures provide strong elastic anisotropies in both the shear and longitudinal moduli. In addition, our measurements in the as-sprayed condition suggest that the as-sprayed YSZ coatings exhibit degenerate (elliptic) transverse isotropy with inter-splat pores that tend to be perpendicular to the spraying direction. The dependence of the elastic constants on the heat-treatment temperature shows that the elastic anisotropy of the plasma-sprayed YSZ coatings increases slightly and then decreases as the heat-treatment temperature increases. This finding is supported by the different effective sintering temperatures of the inter-splat pores and intra-splat cracks. |
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Enhanced corrosion resistance of magnesium alloy by plasma electrolytic oxidation plus hydrothermal treatment |
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Jinhe Dou, Jing Wang, Huancai Li, Yupeng Lu, Huijun Yu, Chuanzhong Chen |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127662
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• A dense Ca3Al2(OH)12 layer was fabricated on the PEO coating surface by HT.
• The anti-corrosion property of the PEO/HT coating was significantly higher than that of both Mg alloy and PEO coating. • The formation mechanism of Ca3Al2(OH)12 structure layer was proposed. |
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Plasma electrolytic oxidation (PEO) is a promising surface treatment technique to enhance the corrosion resistance of Mg alloy. However, the micro-pores and micro-cracks of the PEO coating limit its anti-corrosion protection capability. In this study, a dense Ca3Al2(OH)12 layer was fabricated on the PEO coating surface by hydrothermal treatment (HT), forming a PEO/HT composite coating. Surface morphologies, chemical composition, phase composition and growth process of the PEO/HT composite coating were characterized using Field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectrophotometer (FT-IR). Corrosion resistance of the samples was studied through immersion test, hydrogen evolution test, and electrochemical test. Results demonstrated that the PEO/HT coating possessed a polyhedral structure and the micro-pores and micro-cracks of the PEO coating were sealed. The PEO/HT composite coating showed improved bioactivity in comparison with PEO coating and Mg alloy after immersion in Hanks' solution. Moreover, the Ca3Al2(OH)12 crystals layer improved the corrosion resistance of PEO coating significantly. Furthermore, the growth process of Ca3Al2(OH)12 layer was discussed. |
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Microstructure evolution and properties of in-situ TiC reinforced titanium matrix composites coating by plasma transferred arc welding (PTAW) |
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T. Zhao, S. Zhang, F.Q. Zhou, H.F. Zhang, C.H. Zhang, J. Chen |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127637
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• In situ TiC reinforced surface modified coatings were prepared by PTAW.
• The formation mechanism of each phase in the coating was analyzed in detail. • Revealed the anti-cavitation erosion mechanism of TMCs coating. • The passivation kinetics of TMCs coating and Ti6Al4V coating were compared. • Revealed the wear mechanism of TMCs coating and Ti6Al4V substrate. |
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In-situ TiC reinforced titanium matrix composites coating was prepared on the surface of Ti6Al4V by plasma transfer arc welding using pure Ti powder and Cr3C2 powder. The obtained TMCs coating is dense, no porosity and forms a good metallurgical bond with the substrate. There are obvious composition differences in the coating along the direction of temperature gradient: Mixture structures of TiC dendrites, β-Ti, needle-like α-Ti and TiCr2 phases were formed at the top of the coating due to heat accumulation and slow cooling rate, and the formation mechanism of these phases was analyzed in detail. The cavitation erosion resistance, corrosion resistance, microhardness and wear resistance of Ti6Al4V substrate and TMCs coating were compared and clarified. The TiC ceramic phase generated in situ is anchored by β-Ti, so that the TMCs coating is both tough and hard. The microhardness of the top of the coating reaches 1325 HV0.2, which is 4 times that of the substrate. In addition, the α-Ti + TiCr2 phase precipitates along the minimum mismatch crystal orientation and presents a certain crystallographic orientation relationship with β-Ti. The TMCs coating exhibits higher resistance to wear and corrosion than Ti6Al4V substrate. Therefore, the surface modified TMCs coating prepared in this study is expected to apply in the surface protection of Ti6Al4V under the working conditions of wear and sea water erosion corrosion in the field of ocean engineering. |
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Plasma electrolytic synthesis and characterization of oxide coatings with MWO4 (M = Co, Ni, Cu) as photo-Fenton heterogeneous catalysts |
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M.S. Vasilyeva, I.V. Lukiyanchuk, A.A. Sergeev, K.A. Sergeeva, A.Yu. Ustinov, V.V. Tkachev, O.D. Arefieva |
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Russia |
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https://doi.org/10.1016/j.surfcoat.2021.127640
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• The MWO4 (M = Cu, Ni, or Co) were formed on titanium by plasma electrolytic oxidation.
• The formed composites are characterized by a small bandgap. • The samples are effective photo-Fenton-like heterogeneous catalysts in the neutral media. • For Co-containing samples the methyl orange degradation reaches 85 and 55% under UV and Vis irradiation. • The some metal leaching did not lead to a decrease in MO degradation. |
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Titanium-supported oxide coatings with MWO4 (M = Cu, Ni, or Co) were formed by the single-stage plasma electrolytic oxidation of titanium in alkaline tungstate-phosphate electrolytes with M(II)–EDTA complex ions. All formed coatings exhibited photocatalytic activity in the reaction of degradation of methyl orange (10 mg/L MO, pH = 6.8) in the presence of 10 mmol/L hydrogen peroxide under UV and Vis irradiation. The Ti/TiO2-CoWO4 composite was most effective catalyst: the degree of MO azo dye degradation reached 85 and 55% after 180 min irradiation under UV and Vis light, respectively. The bandgap values determined by the Tauc's method for the direct allowed transition were 2.2, 2.45 and 2.5 eV for Co-, Cu- and Ni-containing samples, correspondingly. The leaching of cobalt, copper and nickel from catalysts during the degradation process was less than 0.88, 0.52 and 1.47 mg/L per cycle, but this fact did not lead to a decrease in MO degradation with the number of cycles. The degradation reaction under UV and Vis irradiation has a first order rate coefficient of (8.9–11.0) × 10−3 and (2.0–8.3) × 10−3 min−1, respectively. |
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Attainment of high specific hardness and specific modulus in spark plasma sintered aluminium-copper-silicon carbide-titanium carbide hybrid composite
Hohe spezifische Härte und spezifisches Schubmodul von einem sparkplasmagesinterten Aluminium-Kupfer-Siliziumkarbid-Titankarbid-Verbundwerkstoff |
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S. Saha, M. Ghosh, A. Kumar Pramanick, C. Mondal, J. Maity |
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India |
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https://doi.org/10.1002/mawe.202100105 |
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Aluminium matrix hybrid composites have been consolidated effectively by spark plasma sintering with new combinations of reinforcement and high volume percentage of ceramic particulates to maximize specific hardness and specific modulus through the powder metallurgy route. The aforementioned techno-scientific accomplishment with regard to metal matrix composite aims to meet a continuous increase in the global demand for a material with minimum structural weight and high-modulus for structural (automotive and aerospace) applications. The new aluminium based hybrid composite developed by incorporating ceramic particulate reinforcements (12.5 wt.% silicon carbide and 12.5 wt.% titanium carbide) along with 22.5 wt.% copper as the metallic reinforcement attains significantly high specific hardness (85 HV/gcm−3), specific Young's modulus (33.56 GPa/g cm−3), specific bulk modulus (27.97 GPa/g cm−3) when compared with the reported range of specific hardness (13 HV/g cm−3–89 HV/g cm−3), specific Young's modulus (24 GPa/g cm−3–27 GPa/g cm−3) and specific bulk modulus (20 GPa/g cm−3–22 GPa/g cm−3) possessed by structural steels. This is accredited to the genesis of a novel microstructure that consists of fine copper, silicon carbide and titanium carbide particulates together with a nominal in-situ originated aluminium-copper equilibrium phases distributed in a highly substructured aluminium based matrix with a significant dislocation density (7.56 ⋅ 1014 m-2). |
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Enhancement of coating characteristics via improved plasma electrolytic oxidation set-up
Weiterentwicklung der Beschichtungscharakteristik durch verbesserte Konfiguration der plasmaelektrolytischen Oxidation |
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M.S. Sharizal, A.R Bushroa, M.A. Zavareh, N.A. Sukrey |
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Malaysia, USA |
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https://doi.org/10.1002/mawe.202000087 |
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The plasma electrolytic oxidation process involves high-temperature operations and exposed to corrosive chemicals. Thus it requires stringent experimental set-up to produce uniform and high-quality coatings. This study proposes an enhancement to the current plasma electrolytic oxidation experimental set up to improve: 1) electrode holder; 2) cathode-anode electrodes, and 3) water-cooling system. In this paper, the focus is dedicated to the first two items. For the first item, the redesigned electrode holder is developed using 3-dimensional software. For the second item, results due to cathode via stainless container as well as carbon electrode are discussed. The performance of the new set-up plasma electrolytic oxidation is compared with the old one by analysing the microstructure and the mechanical properties of titanium dioxide coatings formed on a titanium aluminium vanadium alloy substrate using both set-ups. Surface morphology shows that the coating produced using the new set-up is thicker, denser and has lower porosity as compared to the coating deposited using the old set-up. The mechanical properties of hardness and adhesive strengths of the coating are also improved in the new set-up. Thus, the use of this set-up is recommended for improved coating performance to produce a uniform coating having enhanced mechanical performance. |
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Effect of sealing treatment on corrosion behavior of plasma sprayed ZrO2 coated Cf/Mg composites |
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Li Yang, Xiao hongShi, Xinfa Tian, Xu Han, Jierui Mu, Lehua Qi |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127627
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• A SiO2 layer successfully sealed the ZrO2 coating by sol-gel method assisted by heat treatment.
• The SiO2 sealing layer decreased the corrosion rate of ZrO2 coated Cf/Mg composites by nearly 10 times. • The improved electrochemical properties were attributed to the dense structure and hydrophobicity of the SiO2 layer. |
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To improve the corrosion resistance of plasma sprayed ZrO2 coated Cf/Mg composites, the pores on the ZrO2 coating were sealed with the SiO2 coating prepared by sol-gel technology. The surface porosity of the ZrO2 coating was reduced by 65.47% after the SiO2 sealing treatment. The electrochemical results demonstrated that the corrosion potential was significantly improved by 44.61% after the SiO2 sealing treatment. The corrosion current density was degraded from 1.94 × 10−5 A·cm−2 to 2.37 × 10−6 A·cm−2, and the corrosion rate was even reduced by nearly 10 times. Besides, the contact angle of the corrosive solution on the coating was raised from 45.3° to 72.4° after the sealing treatment. The good corrosion resistance after the sealing treatment is ascribed to the dense structure and the improved hydrophobicity of the SiO2 sealing layer, which provide an effective barrier to block the penetration of corrosive solution for Cf/Mg composites. |
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Fundamental understanding on the microstructure and corrosion resistance of Cr-(Cr, Al)2O3 composite coatings in-situ synthetized by reactive plasma spraying |
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Meihui Sun, Jinsong Song, Cuiwei Du, Yong Yang, Dianran Yan |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127608
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• Cr-(Cr,Al)2O3 composite coatings are in-situ synthesized by reactive plasma spraying.
• The eutectic coating is composed of solid solution and dispersed nano-Cr particles. • The corrosion resistance is related to the microstructure and defects of the coating. • Nano-Cr particles form a stable Cr(OH)3 film to improve the corrosion resistance. |
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Three composite coatings were prepared with Al-Cr2O3-Al2O3 composite powders feedstocks by in-situ reactive plasma spraying, and the microstructures and corrosion resistances were studied. The results show that the CAC-1 coating is the hypoeutectic microstructure consisting of large-size Cr particles and the eutectic structure, the CAC-2 coating presents a typical eutectic microstructure [nano-Cr + (Cr, Al)2O3], and the CAC-3 coating is the hypereutectic microstructure which is composed of (Cr, Al)2O3 solid solution and eutectic structure. The corrosion resistance of the coating is closely related to the microstructure and defects of the coating. The surface of the nano-Cr particles in the CAC-2 coating can form a stable Cr(OH)3 film, which hinders the further contact with the electrolyte, thereby improving the corrosion resistance of the coating itself. In addition, the uniform and dense microstructure also leads to the least coating defects, further improving the corrosion resistance of the coating. While the surface product film of large-size Cr particles in the CAC-1 coating cannot exist stably, causing the Cr to continue to dissolve until it peels off. The coating itself has the highest porosity, so the coating has the worst corrosion resistance. The CAC-3 coating mainly exhibits the characteristics of ceramic coating due to the limited eutectic structure contained. Due to the unevenness of the microstructure, the coating has more defects, resulting in lower corrosion resistance than the CAC-2 coating. |
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Improvement of oxide layers formed by plasma electrolytic oxidation on cast AlSi alloy by incorporating TiC nanoparticles |
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Anton V. Polunin, Alisa O. Cheretaeva, Eugeny D. Borgardt, Igor A. Rastegaev, Mikhail M. Krishtal, Alexander V. Katsmana, Igor S. Yasnikov |
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Russian Federation, Israel |
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https://doi.org/10.1016/j.surfcoat.2021.127603
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• PEO coating was formed on AlSi alloy under the adding TiC NPs into electrolyte.
• TiC NPs demonstrated inert mechanism of incorporation into the coating during PEO. • Incorporation of TiC NPs increased hardness, wear and corrosion resistance. |
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The effect of titanium carbide nanoparticles (TiC NPs) on the structure, chemical and phase composition of the oxide layers obtained by plasma electrolytic oxidation (PEO) on the aluminum-silicon alloy (7.5 wt% Si) was investigated. A significant increase in hardness and effective elastic modulus (~1.4 times), wear resistance (~3 times) and corrosion resistance (~10 times) along with a substantial increase of the layer thickness (about 30%) were found to be connected with chemically inert incorporation of TiC NPs into the oxide layer, while the volume fraction of the incorporated particles in the oxide layer was only about 1%. Improvement of the layer properties was concerned with a decrease in the number of pores and cracks, an increase in the layer crystallinity, and a shift in the phase composition towards more stable phases such as mullite. The assumed mechanism of the TiC NPs effect is a decrease in the breakdown voltage of vapor-gas bubbles (VGB) due to sparking (local breakdowns) from cathodic electrolyte onto the TiC nanoparticles incorporated into the microchannel walls. Sparking to these particles can promote ionization of the gaseous medium, providing earlier microarc discharge through the entire VGB. It results in a substantial increase in the number of microarc discharges, which then initiate larger volumes of melted splash metal and subsequently larger volumes of oxide layer. The higher average temperature results in a decrease in the defectiveness of the macrostructure, the removal of gas from the layer, the growth of crystallites, the removal of residual strains, and a stabilization in the phase composition. |
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Cuboid Cu(HBTC)(H2O)3 synthesis via plasma pretreatment of trimesic acid solution |
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Moriyuki Kanno, Tsuyohito Ito, Yoshiki Shimizu, Kazuo Terashima |
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Japan |
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https://doi.org/10.1002/ppap.202100047 |
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Metal–organic frameworks (MOFs) have attracted considerable research attention in recent years, with the focus being on controlling their morphology for various applications. Cu(HBTC)(H2O)3, a one‐dimensional MOF, is constructed with a copper(II) ion and 1,3,5‐benzenetricarboxylic acid (H3BTC, trimesic acid). A twodimensional structure can be achieved by adding ethanol and polyvinylpyrrolidone during synthesis. In this study, its three‐dimensional cuboid Cu (HBTC)(H2O) structure was synthesized by plasma pretreatment of an H3BTC solution. |
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Improvement of the adhesive capacity of SBR for footwear outsoles by surface activation and coating deposition with atmospheric pressure plasma |
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Rodolfo Múgica-Vidal, Juan Mercadal-Guillén, Fernando Alba-Elías, Elisa Sainz-García |
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Spain, Belgium |
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https://doi.org/10.1002/ppap.202100046 |
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Looking for a cleaner alternative to halogenation in the preparation of rubber for bonding with leather in footwear, atmospheric pressure plasma treatments were applied on styrene–butadiene rubber (SBR). Its adhesive capacity was improved and the highest bond strength standards for footwear were met. Two optimal processes were identified: (1) Plasma polymerization of (3-aminopropyl)triethoxysilane coatings on flat SBR and (2) plasma-activation of mechanically roughened SBR. The improvement on coated, flat SBR was mainly due to its surface chemistry having greater concentrations of polar carbon–oxygen species than the untreated SBR. For plasma-activated, mechanically roughened SBR, combined contributions of mechanical roughening and roughening by plasma irradiation were found. Coating flat SBR at 100 mm/s showed the best balance between improved bond strength and durability. |
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Production of carbon monoxide from a He/CO2 plasma jet as a new strategy for therapeutic applications |
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Claire Douat, Pablo Escot Bocanegra, Sébastien Dozias, Éric Robert, Roberto Motterlini |
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France |
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https://doi.org/10.1002/ppap.202100069 |
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A new method to deliver carbon monoxide (CO) for medical applications is presented using a kHz-driven helium plasma jet with a 1% CO2 admixture. Despite being known for its anti-inflammatory, vasorelaxing, and anti-apoptotic effects, a possible role of CO generated from plasma for the treatment of various diseases has so far been neglected. Here, we show that CO production of a plasma jet can be tuned from 100 to 2000 ppm. The number of CO molecules produced per pulse is in the range of 1 × 1012 to 1.5 × 1013. To assess the delivery of CO, mouse blood hemoglobin was used as a scavenger of CO and the consequent formation of carboxyhemoglobin was quantified. This study reveals for the first time that plasma can generate and deliver CO for therapeutic interventions. |
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Effect of metal mesh addition on polymer surface etching by an atmospheric pressure plasma jet |
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Tao Wang, Jiahao Wang, Shengquan Wang, Li Lv, Meng Li, Liping Shi |
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China |
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https://doi.org/10.1016/j.apsusc.2021.151258
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• Plasma working with grounded metal mesh is difficult to realize effective polymer etching.
• The etched surface without metal mesh has higher etching rate and rougher surface. • Higher surface oxidation was obtained with the participation of charged particles. • Synergetic etching process of charged particles and reactive species was discussed. |
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Atmospheric pressure plasma jet has shown great potential for polymer film treatment, but the etching process of polymer surface by the plasma jet is still not developed. In this paper, the effect of a grounded metal mesh addition on the etching process of polymer surface through the plasma jet was investigated. Comparative study of polymer film treated by the plasma jet with and without a grounded stainless steel mesh (SSM) is systematically investigated by the analysis of etching rate, surface morphologies and chemical compositions. Compared with the plasma etching process with SSM, the etching results without the addition of SSM have much higher etching rate, rougher etched surface, and higher surface oxidation. Finally, the etching process occurring at the plasma/polymer interface was also discussed. Since the addition of SSM could filter out the charged particles in plasma jet, the role of charged particles in the etching process was discussed and the synergetic etching process was proposed based on the structural dependence and chemical analysis of the observed results. |
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A nanoscale investigation on the influence of anodization parameters during plasma electrolytic oxidation of titanium by high-resolution electron energy loss spectroscopy |
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Luca Casanova, Mattia Arosio, Mohammad Taghi Hashemi, Maria Pia Pedeferri, Gianluigi A. Botton, Marco Ormellese |
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Italy, Canada |
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https://doi.org/10.1016/j.apsusc.2021.151133
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• EELS combined with advanced data analysis enhances process understanding.
• Use of DC regime favors growth of TiO and Ti2O3 in contact with the substrate. • Pulsed PEO homogenizes the oxide stoichiometry favoring Ti+4 oxide bearing phases. • Cathodic polarization and high frequency promoted development of type-B plasma. • Plasma events generally cause oxide vaporization in the form of TiO molecules. |
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High-resolution electron energy loss spectroscopy (EELS) in a transmission electron microscope is performed on titanium oxide coatings obtained by plasma electrolytic oxidation (PEO) with application of different electrical parameters. Core loss spectra were used to evaluate the structural evolution occurring at the two main regions characterizing a PEO coating, i.e. barrier and porous layers. Local crystalline information, extracted from EELS, was correlated to macroscopic technological parameters such as duty cycle and frequency, based on advanced data analysis. Using the spectral differences, structural maps are, for the first time, provided for titanium oxide grown anodically. Cathodic current was found to favour the growth of a mainly crystalline barrier layer, responsible for abundant O2 evolution during the treatment. A detailed mechanism regarding the stimulation of type-B discharges, when using cathodic polarization at high frequency, is given comparing outcomes from optical emission spectroscopy and structural information. As the result of the intense plasma interaction with the growing layer, the structure evolved towards the formation of 18 nm of titanium oxide characterized by a strong Ti+3 fingerprint, followed by 85 nm of Ti3O5 formed according to high temperatures and the de-oxidative condition encountered. |
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Incorporation of graphene nano platelets in suspension plasma sprayed alumina coatings for improved tribological properties |
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Satyapal Mahade, Antonio Mulone, Stefan Björklund, Uta Klement, Shrikant Joshi |
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Sweden |
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https://doi.org/10.1016/j.apsusc.2021.151227
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• GNP incorporated in alumina matrix to deposit composite coatings via SPS.
• Raman analysis confirmed retention of GNP in as-processed composite coatings. • Improved mechanical and tribological properties achieved for composite coatings. • Wear mechanisms for composite and monolithic coating were revealed. |
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Graphene possesses high fracture toughness and excellent lubrication properties, which can be exploited to enhance tribological performance of coating systems utilized to combat wear. In this work, suspension plasma spray (SPS) process was employed to deposit a composite, graphene nano-platelets (GNP) incorporated alumina coating. For comparison, monolithic alumina was also deposited utilizing identical spray conditions. The as-deposited coatings were characterized in detail for their microstructure, porosity content, hardness, fracture toughness and phase composition. Raman analysis of the as-deposited composite coating confirmed retention of GNP. The composite coating also showed good microstructural integrity, comparable porosity, higher fracture toughness and similar alumina phase composition as the monolithic alumina coating. The as-deposited coatings were subjected to dry sliding wear tests. The GNP incorporated composite coating showed lower CoF and lower specific wear rate than the pure alumina coating. Additionally, the counter surface also showed a lower wear rate in case of the composite coating. Post-wear analysis performed by SEM/EDS showed differences in the coating wear track and in the ball wear track of monolithic and composite coatings. Furthermore, Raman analysis in the wear track of composite coating confirmed the presence of GNP. The micro-indentation and wear test results indicate that the presence of GNP in the composite coating aided in improving fracture toughness, lowering CoF and specific wear rate compared to the monolithic coating. Results from this work demonstrated retention of GNP in an SPS processed coating, which can be further exploited to design superior wear-resistant coatings. |
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Spark plasma sintering of nanostructured ZnS ceramics: Grain growth control and improved hardness |
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Damien Bregiroux, Julie Cedelle |
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France |
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https://doi.org/10.1016/j.msea.2021.142064
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The densification and grain growth behavior of a ZnS nanopowder during spark plasma sintering (SPS) were investigated under the pressure of 125 MPa and constant heating rate of 25 °C min−1. At a sintering temperature of 550 °C, almost fully dense ZnS ceramics (98.2%) could be obtained with grain size as low as 75 nm. At higher temperature, ZnS is subject of a very important grain growth that is detrimental to the mechanical properties. A maximum Vickers microhardness of 4.2 GPa was measured, which is 70% higher than the current state of the art. Retaining the grain size below 100 nm appears to be the key to developing competitive ZnS functional ceramics. |
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Accelerated Healing of Chronic Wounds under a Combinatorial Therapeutic Regimen Based on Cold Atmospheric Plasma Jet Using Contact and Noncontact Styles |
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Sri Darmawati, N. Nasruddin, Gela Setya Ayu Putri, Arya Iswara, Putri Kurniasiwi, Eka Sakti Wahyuningtyas, Laela Hayu Nurani, Defi Nurul Hayati, Tatsuo Ishijima, Toshio Nakatani, Junko Sugama |
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Indonesia, Japan |
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Plasma Medicine, 11(2):1 – 18 (2021) |
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One critical element for applying atmospheric pressure plasma jet for medical purposes is that it is possible to construct a combinatorial therapeutic regimen based on contact and noncontact styles for the cold atmospheric plasma jet. This study evaluates plasma jet effectiveness for bacteria-infected wounds in a small animal model. In this investigation, we test a novel combinative treatment using contact and noncontact style for plasma jet that was generated at high voltage of ~ 9 kV. We use medical-grade argon gas as a single carrier gas. The object of plasma treatment is BALB/c mouse skin wounds that were infected with Staphylococcus aureus. We use four plasma jet treatments, namely, C (control), CP–CP (contact), NCP–NCP (noncontact), and CP–NCP (contact–noncontact). For CP–NCP, from days 0 to 7 we apply a contact style of plasma jet treatment to wounds to kill bacteria; from days 8 to 13, a noncontact style of plasma jet is applied to stimulate wound healing. Our results show that with CP–CP, contact plasma treatment can remove the biofilm layer, but after the biofilm layer disappears contact plasma treatment inhibits the wound-healing process. NCP–NCP is not effective in eliminating bacterial biofilms and impedes the wound-healing process. With CP–NCP, contact plasma exposure during days 0 to 7 is able to remove bacterial biofilms, and irradiation of noncontact plasma during days 8 to 14 accelerates wound healing. Finally, CP–NCP significantly accelerates healing. The combinatorial therapeutic regimen based on contact and noncontact styles of cold atmospheric plasma jet is recommended for chronic wound management, because it effectively removes bacterial biofilms and accelerates wound healing. |
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Efficacy of Contact-Type Cold Atmospheric Plasma on Skin Rejuvenation for Persons with Aged Skin |
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Warumpa Suwannarat, Phannapat Intarit, Supaporn Pitiporn, Wachana Tungkwampian, Piyapong Prasertsri, Wicharn Girdwichai |
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Thailand |
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Plasma Medicine, 11(2):19 – 28 (2021) |
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Current research has proven that cold atmospheric plasma (CAP) is beneficial for stimulating and promoting tissue healing. Application of CAP to skin results in rejuvenation of collagen and elastic fibers and enhances the spread of active agents. This study evaluates efficacy of contact-type CAP on skin rejuvenation in individuals with aging skin. We recruited 80 participants (aged 40–70 yr) and divided them into two groups (40 participants/group). The first group received contact-type CAP only (CAP group), and the other received contact-type CAP after applying Emblica Plus® Facial Cream (EM) on the face and neck (CAP + EM group). Both groups received contact-type CAP for 20 min/wk for 8 consecutive wk. We evaluated skin parameters before and immediately after each application and repeatedly evaluated during the 9th wk. Decreased skin pigmentation and oiliness and increased skin elasticity were observed immediately following each application of contact-type CAP, and these effects continued through the following weeks. At weeks 7 and 8, skin elasticity was significantly superior in the CAP + EM group compared to the CAP group. Contact-type CAP can be applied to rejuvenate skin, especially aging skin. Moreover, facial cream can be applied to enhance efficacy amid skin elasticity.
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Effects of Direct and Indirect Treatment of Human Cells with Cold Atmospheric Plasma Devices |
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Cian D. Madigan, Fiona O’Neill, Denis O'Sullivan, Darren F. Kavanagh, Liam O'Neill |
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Ireland, USA |
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Plasma Medicine, 11(2):29 – 42 (2021) |
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An in vitro study was conducted to compare the interaction of two cold atmospheric plasma devices on mammalian cells. The two devices were powered by the same FDA-cleared radio frequency power supply, but operated under different power regimes—direct and afterglow. Cells were plasma-treated for various amounts of time, and cell counts were performed at 24 and 48 hours after treatment. Thermal and electrical analyses in combination with chemical analysis of peroxide, nitrites, nitrates, and pH were conducted to identify the long-lived interactions that could impact cell viability. Optical emission spectroscopy was used to monitor the short-lived plasma species generated by each method. It was found that both plasma modes gave rise to differences in the levels of active species generated and this impacted the cellular response.
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Growth Comparison between Lymphocyte BW5147 T Cells and EL4 T Cells Using Atmospheric Oxygen Plasma Irradiation |
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Sitti Subaedah, Haruka Uematsu, Nobuya Hayashi |
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Japan |
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Plasma Medicine, 11(2):43 – 54 (2021) |
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The activation of T cells (EL4 and BW5147) was examined when they were sensitized with monoclonal antibodies against CD3/CD28 followed by irradiation with atmospheric oxygen plasma. The proliferation of EL4 and BW5147 T cells sensitized by anti-CD3/CD28 was evaluated as a function of the duration of oxygen plasma irradiation. Plasma irradiation significantly promoted cell proliferation; when plasma irradiation was applied to sensitized T cells for 50 s, cell numbers increased 1.8 times over 24 h compared with cells that were not exposed to irradiation. We compared IFN-gamma production between EL4 T cells and BW5147 T cells after plasma irradiation. The results indicated that the IFN-gamma production in EL4 T cells tends to increase under most conditions compared with controls (without plasma irradiation), while in BW5147 T cells, due to few active oxygen species produced from plasma irradiation, IFN-gamma tends not to increase for any irradiation periods compared with the control. In addition, gene expression analysis of EL4 T cells indicated that MAPK-related ERK genes and IFNG genes were upregulated by oxygen plasma irradiation, which proves that plasma irradiation enhances immune function.
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Multifunctional DBD-Based Ozone Sterilizer with Ultrasonic Cavitation for Low-Temperature Treatment of Medical Tools |
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Alina S. Lozina, I. E. Garkusha, S. A. Shypilov, P. M. Vorontsov, I. N. Bolduriev, Y. P. Gnidenko, A. V. Taran, O. G. Chechelnitckij |
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Ukraine |
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Plasma Medicine, 11(2):55 – 61 (2021) |
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The development of a dielectric barrier discharge (DBD) sterilizer for cleaning, disinfection, and low-temperature sterilization in water saturated with ozone is described. The sterilizer consists of an ozone generator based on glow barrier dielectric discharge with flat electrodes covered with dielectric operated at a high-voltage power supply of 250 W. The 2.5-L sterilization bath is equipped with a 100-W ultrasound source to provide additional cleaning of complexly shaped objects. High ozone concentrations in water (up to 10 mg/L) are necessary for effective and complete sterilization of tools and is achieved by dissolving ozone in cooled water (~ 10–15°C). The ozone concentration at the output of the ozone generator is 25 mg/L. The main characteristics of the ozone sterilizer with ultrasonic cavitation are given, and the effectiveness of this sterilizer in inactivating a number of microbiological objects is shown.
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Collagen Coating of Titanium Implants Using Nonthermal Plasma |
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Liam O'Neill, Barry Twomey, Fei Tan, John O'Donoghue, John A. Hunt |
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Ireland, China, UK, Taiwan |
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Plasma Medicine, 11(2):63 – 78 (2021) |
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Surface modification of implants is now an essential aspect of biocompatibility. A single-step process to attach biomolecules to implants represents a major advance, and plasma coating potentially achieves this. An aqueous solution of collagen was sprayed into a nonthermal plasma and deposited onto titanium surfaces. The plasma instantly transformed the liquid aerosol into a coagulated dry coating on the implant surface. Surface analysis confirmed the presence of a thin, conformal protein layer on the metal surface. Titanium fixation screws were coated first with hydroxyapatite and then with a layer of collagen and were implanted into the femurs of New Zealand white rabbits and compared to various control surfaces. Measurements of the rotational torque removal force indicated that the collagen coating enhanced bone fixation and created a more reproducible well-anchored, stable implant than the traditional plasma-sprayed hydroxyapatite coatings. Nonthermal plasma processing offers a single step route to the biological functionalization of implantable surfaces. The process requires no polymers, primers, or linkers and offers an opportunity to control biocompatibility and to tailor local response to the implant in vivo. This opens the door to a wide variety of novel biological surface coatings across all aspects of life sciences and medicine.
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Spark discharges in liquid heptane in contact with silver nitrate solution: Investigation of the synthesized particles |
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Kyana Mohammadi, Ahmad Hamdan |
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Canada |
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https://doi.org/10.1002/ppap.202100083 |
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In this study, spark discharges are generated in liquid heptane that is in contact with an immiscible solution of silver nitrate. The results demonstrate that the discharges produced at 22 kV voltage amplitude and 500 ns pulse width change the color of both liquids and lead to the formation of nanoparticles. Most particles collected from heptane are nanocomposites of Ag nanoparticles (<10 nm) in the hydrocarbon network. Meanwhile, the material collected from the silver nitrate solution is Ag nanoparticles (10–150 nm of diameter). At shorter pulse width (100 ns), the discharges generate similar materials in both liquids; however, the size distribution of these materials is smaller. Finally, a scenario of particle synthesis is proposed and discussed. |
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Antitumor effects of hyperthermia with plasma-treated solutions on 3D bladder tumor spheroids |
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Hao Zhang, Jishen Zhang, Shengduo Xu, Zifeng Wang, Dehui Xu, Li Guo, Dingxin Liu, Michael G. Kong, Mingzhe Rong |
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China, USA |
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https://doi.org/10.1002/ppap.202100070 |
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As a form of cold atmospheric plasma application, plasma-treated solutions have shown promise in tumor therapy. Especially for the treatment of intracavitary tumors, plasma-treated solutions combined with traditional perfusion therapy have strong application potential. Here, we assessed the antitumor effects of the plasma-treated medium combined with hyperthermia on three-dimensional bladder tumor spheroids in vitro. We found that the combined treatment of plasma-treated medium and hyperthermia (43°C) presented better antitumor effects than a single treatment. Further research showed that synchronous hyperthermia can promote the penetration of plasma-generated reactive oxygen species from the plasma-treated medium into cancer cells. Our results suggest that hyperthermic perfusion therapy using plasma-treated solutions may serve as a novel and valuable therapeutic strategy for bladder cancer. |
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Validation of colorimetric assays for hydrogen peroxide, nitrate and nitrite ions in complex plasma-treated water solutions |
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Valeria Veronico, Pietro Favia, Francesco Fracassi, Roberto Gristina, Eloisa Sardella |
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Italy |
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https://doi.org/10.1002/ppap.202100062 |
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Liquids treated with cold plasma emerged as ‘redox drugs’ in biomedicine, as sources of reactive oxygen and nitrogen species targeting cellular functions, including wound healing and cancer progression. The use of cell culture media as starting liquid, however, challenges the identification of plasma-generated chemistry, limited by the presence of many reactive species and organic compounds. Available detection methods need, therefore, to be confirmed in these liquids to avoid inaccurate results. In this research, robustness, linearity, accuracy and specificity of three colorimetric assays are investigated to detect H2O2, NO2− and NO3−, predominant plasma-induced products. The results clearly highlight the presence of some factors affecting the detection in cell culture media like high concentrations of chlorides found interfering with the detection of NO3− in the medium. |
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Plasma-activated Ringer's lactate solution inhibits the cellular respiratory system in HeLa cells |
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Hiromasa Tanaka, Shogo Maeda, Kae Nakamura, Hiroshi Hashizume, Kenji Ishikawa, Mikako Ito, Kinji Ohno, Masaaki Mizuno, Yashiro Motooka, Yasumasa Okazaki, Shinya Toyokuni, Hiroaki Kajiyama, Fumitaka Kikkawa, Masaru Hori |
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Japan |
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https://doi.org/10.1002/ppap.202100056 |
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Nonequilibrium atmospheric pressure plasma has enabled a variety of new applications in medicine, agriculture, and other industries. It is particularly noteworthy that plasma itself and/or plasma-activated culture medium have been shown to preferentially kill various cancer cells. We have previously developed a plasma-activated Ringer's lactate solution (PAL) for use as a new cancer treatment. In this study, behaviors of extracellular and intracellular reactive oxygen and nitrogen species in the cellular respiratory system of PAL-treated HeLa cells were investigated using an extracellular flux analyzer and a probe to measure mitochondrial membrane potential. In PAL-treated HeLa cells, extracellular hydrogen peroxide in PAL was found to be responsible for the induction of intracellular hydrogen peroxide and apoptosis, while other components in PAL are responsible for the induction of non-H2O2 intracellular ROS and non-apoptotic cell death, which should be clarified by further experiments. We believe that these are long-lived species derived from plasma-activated lactates. Furthermore, we found that the plasma-activated lactates inhibited glycolysis and the tricarboxylic acid (TCA) cycle, but not the electron transport chain in HeLa cells. These results suggest that PAL induces multiple modes of cell death, including apoptosis through hydrogen peroxide, and non-apoptotic cell death associated with the impairment of mitochondrial functions (glycolysis and TCA cycle). These findings shed light on the novel mechanism underlying plasma-activated lactate-induced cell death. |
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Light emission from microwave discharges in liquid hydrocarbons at the initial stages of their development |
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Yuri A. Lebedev, Galina V. Krashevskaya, Timur S. Batukaev, Irene L. Epstein |
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Russia |
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https://doi.org/10.1002/ppap.202100051 |
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Time-resolved optical techniques (spectrograph, high-speed camera, photodiode) were used for scrutinizing the initial stages of the microwave discharge (2.45 GHz, 200–500 W) achieved in liquid alkanes (CnH2n + 2). Petroleum solvent Nefras S2 80/120 (a mixture of light hydrocarbons with boiling temperatures ranging between 33°C and 205°C) was considered to be representative of alkanes. The discharge was ignited in the liquid, at the end of a molybdenum antenna located under ambient conditions above the liquid. The discharge displaced sequences of light pulses of different shapes and amplitudes, randomly distributed in time. The minimum pulse duration is 0.5 ms. At times close to 1 ms, the spectrum comprises emission bands of the C2 molecule, lines of hydrogen, and the C+ ion, but there is no continuum associated with the emission of the formed solid carbon-containing particles. In a number of cases, an anomalous spectrum of the C2 molecule was recorded, with no such sequences having been observed before. |
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Insights into the low-temperature deposition of a dense anatase TiO2 film via an atmospheric pressure pulse-modulated plasma |
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Yu Xu, Tao He, Yu Zhang, Haozhe Wang, Ying Guo, Jianjun Shi, Chengran Du, Jing Zhang |
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China |
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https://doi.org/10.1002/ppap.202100050 |
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A pulse-modulated atmospheric pressure radio frequency (RF) plasma is used to prepare a dense TiO2 thin film at a low temperature. With certain plasma on time (Ton = 50 ms), the discharge temperature decreases with plasma off time (Toff), and the lengths of the thin films increase. An anatase TiO2 thin film was successfully deposited on a temperature-sensitive substrate (polyethylene terephthalate). The transmission electron microscope (TEM) results show that the film is composed from anatase TiO2 nanoparticles grown through plasma in 0.07 s. By using laser light scattering, the TiO2 particles are found to be trapped above the substrate at about 0.27 mm during plasma on, which is close to the simulated plasma sheath thickness (0.26 mm). The deposition mechanism of pulse-modulated atmospheric pressure RF plasma has been investigated. |
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The investigation of RONS permeation in plasma-activated oil–water mixed system |
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Yuting Gao, Zhijie Liu, Sitao Wang, Bolun Pang, Dehui Xu, Dingxin Liu, Michael G. Kong |
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China, USA |
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https://doi.org/10.1002/ppap.202100038 |
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Insight into the permeation of reactive oxygen and nitrogen species (RONS) in plasma-activated water is key to optimize and control the biochemical effects. Recently, most investigations on the permeation of RONS mainly concentrate in plasma-activated water where the solution is a single-phase system, while little attention is paid to mixed-phase systems. In this study, we select the oil–water mixed system as a research object and aim at evaluating the effectiveness of different volumes of oil on the generation and transport of RONS in a plasma-activated oil–water (PAOW) mixed system. Results show that the oil layer could significantly impede the permeation ratio of RONS causing a reduction of formation of aqueous RONS in PAOW. The mechanism may be due to the consumption of RONS reacting with the unsaturated bonds in the oil or being adsorbed for the high viscosity of the oil. This study provides valuable guidance for in-depth research on RONS permeation and optimization of wide applications in biomedicine and wastewater treatment. |
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Cold plasma for insect pest control: Tribolium castaneum mortality and defense mechanisms in response to treatment |
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Dana Ziuzina, Robin van Cleynenbreugel, Claudio Tersaruolo, Paula Bourke |
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Ireland, Belgium |
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https://doi.org/10.1002/ppap.202000178 |
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The insecticidal properties and mechanisms of high-voltage air-based atmospheric cold plasma using a contained dielectric barrier discharge reactor were investigated against Tribolium castaneum as an important bio-contaminant in stored grains spoilage. The mortality of 95.0%–100% for preadult stages can be achieved within seconds of treatment, but longer plasma exposure (5 min) is required to kill adult insects. Cold plasma treatment reduces both the respiration rate and the weight of insects and affects the levels of oxidative stress markers in adult populations. Sufficient toxicity is achievable through plasma process control in air to address the range of insect lifecycle stages that are disease vectors and pose risks for grain stability in storage. Balancing insecticidal activity with grains' quality retention can provide a route to sustainable integrated pest management. |
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On the selective killing of cold atmospheric plasma cancer treatment: Status and beyond |
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Dayun Yan, Alex Horkowitz, Qihui Wang, Michael Keidar |
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USA |
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https://doi.org/10.1002/ppap.202100020 |
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Compared with many chemotherapy and radiotherapy modalities, selective killing of cancer cells is a pivotal feature of cold atmospheric plasma (CAP). Understanding its underlying mechanism will build the foundation of CAP-based cancer treatment. Additionally, we provided forward-looking thinking to extend the definition of selectivity from conventional cases involving a single-cell line to a coculture case. Finally, the newly established physically based treatment strategy provides unprecedented visions to realize selectivity beyond the previously established concepts based on reactive species and direct killing effect. |
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Dynamics of plasma formation and gas heating in a focused-microwave discharge in nitrogen |
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A. I. Saifutdinov, E. V. Kustova |
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Russia |
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https://doi.org/10.1063/5.0031020 |
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A self-consistent extended fluid-dynamic model describing a focused microwave discharge in a molecular gas is developed, and numerical simulations of the formation of plasmoids in nitrogen in an experimentally operating cylindrical paraboloid focusing system are carried out. It is shown that, depending on the input power and gas pressure, plasmoids ranging from one to four can be formed. The main spatial–temporal parameters of the plasmoid formed at the main focus of the system are studied in the active phase and in the afterglow phase. The main channels of gas heating in the domain of plasmoid formation are investigated. The importance of taking into account gas heating in the self-quenching reactions of excited nitrogen molecules, both in the active phase and in the first microseconds of the afterglow phase, is shown. The main mechanism at long times in the afterglow phase is the release of energy in vibrational–translational relaxation. |
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A medium-scale volume dielectric barrier discharge system for short-term treatment of cereal seeds indicates improved germination performance with long-term effects |
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H. Brust, T. M. C. Nishime, N. Wannicke, T. S. M. Mui, S. Horn, A. Quade, K.-D. Weltmann |
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Germany, Brazil |
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https://doi.org/10.1063/5.0033369 |
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Atmospheric pressure plasma has the potential of being applied in pre-harvest processes as a sustainable technology for seed and plant treatment. In this study, a medium-scale volume dielectric barrier discharge reactor with a power density of 53.5mW/cm3 was developed and applied for continuous treatment of larger amount of seeds. Within the argon plasma, reactive oxygen and nitrogen species were observed by optical emission spectroscopy. Short-term plasma treatment in the range of seconds of wheat and barley seeds revealed improved germination performance accompanied by altered seed surface properties. Depending on the exposure time, plasma displayed a positive impact on maximum germination and germination speed in both species. In line with this, the t50 values were significantly decreased for plasma treated seeds compared to untreated seeds for wheat and barley. Cumulative germination was enhanced from 20% up to 53% after 27 h of germination for wheat seeds treated from 10 s to 60 s with plasma. Barley seeds respond to the short plasma treatment times with increased germination of 10%–23% after 24 h observation time. Moreover, the seed surface of both plant species became more hydrophilic after plasma treatment supported by a decrease in the water contact angle and an increase in hydrophilic functional groups being detected by x-ray photoelectron spectroscopy. Water uptake by seeds was moderately increased after 2 h of imbibition for both plant species. The positive effects of plasma treatment on germination performance were still detectable after storage of seeds for one and two months. |
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Large volume spark discharge and plasma jet-technology for generating plasmaoxidized saline targeting colon cancer in vitro and in vivo |
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Eric Freund, Lea Miebach, Ramona Clemen, Michael Schmidt, Amanda Heidecke, Thomas von Woedtke, Klaus-Dieter Weltmann, Stephan Kersting, Sander Bekeschus |
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Germany |
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https://doi.org/10.1063/5.0033406 |
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Cold physical plasma is a new anticancer agent. Various prototypes and a few certified devices have been developed during recent years. However, the large number of metastases disseminated into the peritoneal cavity is challenging to target directly with this emerging technology. Plasma-oxidized liquids containing tumor-toxic reactive species, in turn, are promising adjuvants in chemotherapeutic regimens. Yet, the generation of larger volumes of such liquid currently hinders its further exploration for practical application. In this study, the anticancer effect of oxidized saline generated using a spark discharge was investigated using CT26 colorectal cancer cells in vitro and in vivo and compared against oxidized saline generated by the well-investigated medical plasma jet kINPen. The reactive species deposition, as well as the storability of the liquid, was investigated. In a murine, syngeneic, orthotopic model of colorectal peritoneal carcinomatosis, the spark
discharge-oxidized saline reduced the tumor burden to a lower extent when compared to the kINPen. However, and despite the lower therapeutic efficacy, the former had profound immunomodulatory effects on the levels of several peritoneal cytokines, as indicated by the marked decrease of interferon-γ, interleukin (IL)-2, IL-6, IL-10, and IL-17F. The effect observed with the kINPen on these mostly T-cell-related cytokines was less pronounced. This suggests that the spark discharge-oxidized saline unintendedly decreased the T-cell activity, presumably because of its low pH (2.7). Collectively, our results are vital in understanding the plasma-liquid-chemistry for use in oncology and will help design more optimal liquids for further exploration in research and future surgical applications. |
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Ar metastable densities (3P2) in the effluent of a filamentary atmospheric pressure plasma jet with humidified feed gas |
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S.-J. Klose, R. Bansemer, R. Brandenburg, J. H. van Helden |
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Germany |
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https://doi.org/10.1063/5.0037695 |
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The Ar(3P2) metastable density in the effluent of the cold atmospheric pressure plasma jet kINPen was investigated as a function of the feed gas humidity, the gas curtain composition, and the distance from the nozzle by means of laser atomic absorption spectroscopy. The filamentary character of the plasma jet was considered as the absorption signals are from single individual events. From the effective lifetime, the quenching coefficient for Ar(3P2) by water was determined. A maximum Ar(3P2) density of (6:0+0:7) 1013 cm 3 was obtained close to the nozzle for a feed gas humidity of 20 ppm. The densities near the nozzle decreased inversely proportional to the water content in the feed gas leveling off at approximately 1 1013 cm 3, independently from the gas curtain composition. With the addition of water to the feed gas, the excitation dynamics changed, and the production and lifetime of Ar(3P2) was reduced. The impact of Ar(3P2) on the reactive species composition in the effluent was found to be smaller than within the plasma zone inside the plasma jet device. |
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Fundamentals and Applications of Atmospheric Pressure Plasmas
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Michael Keidar, Klaus-Dieter Weltmann, Sergey Macheret
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USA, Germany |
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https://doi.org/10.1063/5.0065750 |
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Characterization of an atmospheric pressure air plasma device under different modes of operation and their impact on the liquid chemistry |
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Sing Wei Ng, Elmar Slikboer, Aaron Dickenson, James L. Walsh, Peng Lu, Daniela Boehm, Paula Bourk |
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Ireland, UK |
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https://doi.org/10.1063/5.0039171 |
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It has been shown that plasma generated in contact with liquid can be tailored to tune the composition of plasma functionalized liquids. For biomedical applications, it is necessary to understand the generation of the plasma treated liquids to modulate the composition and thus the biological response. In this work, two distinct discharge compositions were realized by modifying the location of the ground electrode in a pin-to-liquid plasma system. Through this simple modification to the configurations, the spatiotemporal characteristics of the discharge were significantly affected which, in turn, affected the composition of the generated plasma activated water (PAW). Colorimetric testing of the PAW generated from each system revealed that only one configuration was able to generate PAW with a high concentration of H2O2. Using time-, space-, and wavelength-resolved imaging of excited plasma species [OH, N2 (SPS), N2 + (FNS), and atomic O], the differences in PAW composition were linked to the differences observed in the discharge dynamics between the two configurations. |
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Antimicrobial Activity of a Novel Cu(NO3)2-Containing Sol–Gel Surface under Different Testing Conditions |
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Daniela Toplitsch, Jürgen Markus Lackner, Alexander Michael Schwan, Andreas Hinterer,
Philipp Stögmüller, Kerstin Horn, Natalie Fritzlar, Andreas Pfuch, Clemens Kittinger |
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Austria, Germany |
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https://doi.org/
10.3390/ma14216488 |
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In this study, assessment of the antimicrobial activity of a novel, plasma-cured 2.5% (w/v) Cu(NO3)2-containing sol–gel surface was performed. In contrast to state-of-the-art sol–gel coatings, the plasma curing led to a gradient in cross-linking with the highest values at the top of the coating. As a result, the coating behaved simultaneously hard, scratch-resistant, and tough, the latter due to the more flexible bulk of the coating toward the substrate. Further, the diffusion and permeation
through the coating also increased toward the substrate. In our study, tests according to ISO 22196 showed antibacterial activity of the 2.5% (w/v) Cu(NO3)2-containing sol–gel surface against all bacterial strains tested, and we expanded the testing further using a “dry” evaluation without an aqueous contact phase, which confirmed the antimicrobial efficacy of the 2.5% (w/v) Cu(NO3)2-containing sol–gel surface. However, further investigation under exposure to soiling with the addition of 0.3% albumin, used to simulate organic load, led to a significant impairment in the antibacterial effect under both tested conditions. Furthermore, re-testing of the surface after disinfection with 70% ethanol led to a total loss of antibacterial activity. Our results showed that besides the mere application of an antimicrobial agent to a surface coating, it is also necessary to consider the future use of these surfaces in the experimental phase combining industry and science. Therefore, a number of tests corresponding to the utilization of the surface should be obligative on the basis of this assessment. |
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Wear behavior at high temperatures of ZrO2 - Al2O3 plasma sprayed coatings and an electro-melted AZS refractory |
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D. Franco, H. Ageorges, E. López, F. Vargas |
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France, Colombia |
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https://doi.org/10.1016/j.surfcoat.2021.127715
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• The wear resistance at 1000 °C of two different ZrO2-Al2O3 coatings was evaluated.
• The quantity of α-Al2O3 and t-ZrO2 increased at 1000 °C in both coatings. • Both ZrO2-Al2O3 coatings showed similar wear resistance at 1000 °C. • Both coatings showed better wear resistance at 1000 °C than the reference refractory. • Both coatings can protect the refractory used as substrate at 1000 °C. |
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Two ZrO2-Al2O3 atmospheric plasma coatings were applied to a pressed and sintered aluminosilicate refractory brick, which were compared to an electro-melted alumina-zirconia-silica (AZS) refractory typically used in the glass industry for its high temperature wear resistance. The samples were subjected to sliding contact using a ball-on-disk test at 25, 500, 750, and 1000 °C and then, physical, crystallographic, and mechanical characterizations were performed before and after the wear tests in order to monitor the wear behavior. Both ZrO2-Al2O3 coatings exhibited better wear performance than the electro-melted AZS refractory at all temperatures evaluated, owing to their high hardness and fracture toughness, which were mainly related to the increase of α-Al2O3 and t-ZrO2 phases from γ-Al2O3 and the crystallization of amorphous phases respectively. In the same way, both coatings also showed the same wear mechanisms at all temperatures evaluated. At 25 °C, wear by ductile deformation was identified, while at 500 and 750 °C, wear by brittle deformation was produced, and at 1000 °C, the transition of wear from brittle to ductile deformation was evident. For the electro-melted AZS refractory, until 750 °C, wear by brittle deformation was developed, while at 1000 °C, wear by both, brittle and ductile deformation was detected. |
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Tailoring microstructure of double-layered thermal barrier coatings deposited by suspension plasma spray for enhanced durability |
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Satyapal Mahade, Adwait Jahagirdar, Xin-Hai Li, Björn Kjellman, Stefan Björklund, Nicolaie Markocsan |
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Sweden |
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https://doi.org/10.1016/j.surfcoat.2021.127704
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• Double-layered TBCs comprising combination of dense and porous microstructures of GZ and YSZ deposited by SPS.
• Hypothesis of higher fracture toughness at probable failure location to enhance TBC durability evaluated. • Denser GZ top-layer with high fracture toughness led to improved TCF and BRT lifetime. • YSZ base-layer porosity modulation led to different TCF and BRT lifetime ranking. |
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Gadolinium zirconate (GZ)-based TBCs comprising GZ as the top layer and yttria stabilized zirconia (YSZ) as the base layer, are attractive double-layered thermal barrier coatings (TBCs) for high temperature gas turbine engine application. This work attempts to understand the influence of individual layer microstructure on the durability of GZ/YSZ double-layered TBCs processed by suspension plasma spray (SPS). Two different spray parameters were chosen to obtain a combination of three microstructurally distinct GZ/YSZ double-layered TBCs i.e. GZ porous (P)/YSZ porous (P), GZ dense (D)/YSZ porous (P) and GZ dense (D)/YSZ dense (D). Thermal diffusivity of the as-deposited coatings was measured using Laser Flash Analysis (LFA) technique and the thermal conductivity of the TBCs was calculated. The GZ/YSZ double-layered TBC specimens were subjected to two different durability tests, i.e. thermal cyclic fatigue (TCF) and burner rig test (BRT). Sintering behavior of the individual layer TBC microstructures was evaluated by comparing the porosity evolution in as-deposited and TCF tested TBCs. Fracture toughness measurements performed on each layer of the double-layered TBCs were correlated with the durability results. Thermal cycling results amply demonstrate that the individual layer microstructure of GZ/YSZ double-layered TBC influenced its durability. Detailed failure analysis of the TCF and BRT failed specimens revealed similar failure modes for GZ (P)/YSZ (P), GZ (D)/YSZ (P) and GZ (D/YSZ (D) TBCs under identical thermal cyclic test conditions. However, failure modes differed when subjected to different thermal cyclic test conditions (TCF and BRT) and the probable causes are discussed. Findings from this work provide key insights on designing durable GZ/YSZ double-layered TBCs. |
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Microstructure and properties of CrB2-Cr3C2 composite coatings prepared by plasma spraying |
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Yan-wie Wang, Xiao-wen Sun, Lei Wang, Yong Yang, Xian-xing Ren, Yu-duo Ma, Yu-hang Cui, Wen-wei Sun, Xing-yu Wang, Yan-chun Dong |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127693
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• CrB2 composite coating was prepared by plasma spraying Cr-B4C composite powder.
• Cr reacted with B4C during plasma spraying and CrB2, CrB, Cr3C2, Cr7C3 were generated. • The in-situ reaction of Cr-B4C had great influence on the properties of coatings. • The mechanical properties of the CrB2-Cr3C2 and Cr-B4C coatings were compared. |
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Two different CrB2 composite coatings were prepared on TC4 alloy substrates by atmospheric plasma spraying CrB2-Cr3C2 and Cr-B4C composite powders. The microstructure, microhardness, toughness, scratch resistance and wear resistance of the as-prepared CrB2 composite coatings were investigated. The results show that the phase composition of the CrB2-Cr3C2 composite coating did not change obviously compared with the composite powder. However, Cr reacted with B4C during the spray process and CrB2, CrB, Cr3C2, Cr7C3 phases were generated. Compared with the CrB2-Cr3C2 composite coating, the Cr-B4C composite coating had uniform microstructure, relatively low porosity, higher hardness and toughness, good scratch resistance and dry sliding wear resistance, which is attributed to the in-situ exothermic reaction between Cr and B4C. |
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The mechanisms of carbon nano-flake balls growth by laser ablation and microwave plasma chemical vapor deposition |
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Yue-Zhen Huang, Shih-Chun Tseng, Yi-Hung Chen, Hung-Yin Tsai |
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Taiwan |
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https://doi.org/10.1016/j.surfcoat.2021.127668
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• CNFBs were fabricated without using catalysts but only defects on silicon substrate.
• Growth of CNFBs is simultaneous formation of diamond nanoparticle and growth process. • The predominantly defects by Hα etched and react with carbon atoms to form SiC. • SiC serves as the nucleation site for growing diamond and following lead to graphite. • Hα played a critical role to form SiC and assisted re-nucleation and growth CNFBs. |
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The role of laser ablation (LA) for synthesis of carbon nano-flake balls (CNFBs) in microwave plasma chemical vapor deposition (MPCVD) has been investigated. In this article, a systematic study in frequency, speed, pulse width and processing time of LA were conducted in order to identify the role of LA and find an optimized condition window of the growth process. In addition, the study also demonstrates the nucleation and growth mechanism of CNFBs through Optical Emission Spectroscopy (OES), high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS) observation on the spacing between graphite and diamond and the SiC interface between Si and diamond site. The defect areas, which are caused by Hα etching, react with carbon atoms to form a layer of SiC film, then followed by the increasing amount of CH and CN-C2 radicals, forming diamond nanoparticle and graphite, respectively. In other words, the growth of CNFBs is the near simultaneity of the formation of diamond nanoparticle and the growth process (diamond and graphite). It is discovered that the existence of defects on the silicon substrate and the silicon carbide (SiC) layer after LA are the key factors of growing CNFBs. |
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Micromechanical behaviour and wear resistance of hybrid plasma-sprayed TiC reinforced Tribaloy-400 |
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Veronica Testa, Stefania Morelli, Giovanni Bolelli, Luca Lusvarghi, Stefan Björklund, Shrikant Joshi |
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Italy, Sweden |
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https://doi.org/10.1016/j.surfcoat.2021.127682
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• Composite coatings are obtained by hybrid plasma spraying of a TiC suspension and dry Tribaloy-400.
• The coatings contained Ti-oxycarbides because TiC was partly oxidized during spraying. • The hard phase tends to cluster when its content is >25 vol%. • The coating with ≈25 vol% hard phase had sliding wear rates of 10−6–10−5 mm3/(N·m) from room temperature to 700 °C. • Wear mechanisms change from abrasion and fatigue to tribo-oxidation as temperature increases. |
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Cobalt-based alloys such as Tribaloy-400 are known for their sliding wear resistance at room as well as elevated temperature. However, further enhancement in terms of hardness and wear resistance could be achieved by creating metal matrix composites reinforced by ceramic particles. For this purpose, Tribaloy-400 based coatings were deposited with the addition of different amounts of TiC reinforcement (≈25 vol%, ≈40 vol%, ≈60 vol%) through a “hybrid” plasma spray process, using a dry Tribaloy-400 powder with 10–45 μm particle size and a water-based TiC suspension (d50 = 2.2 μm). Pure Tribaloy and pure TiC coatings were employed for comparison. During spraying, TiC was partly oxidized but could nonetheless be embedded between the bigger Tribaloy-400 lamellae. Specifically, the coating containing ≈ 25 vol% TiC shows a homogeneous microstructure, whilst greater amounts of hard phase lead to some agglomeration. Accordingly, the coating with 25 vol% TiC exhibits a good combination of hardness and toughness (the latter being assessed by scratch testing) and low sliding wear rates of ≈10−5–10−6 mm3/(N·m) from room temperature up to 700 °C in ball-on-disc tests against an Al2O3 counterbody. At room temperature, the tribological behaviour of the coatings is controlled by abrasive grooving and spallation due to surface fatigue. With increasing temperature, tribochemical phenomena take on an ever-increasing role and, at 700 °C, a uniform, oxide-based tribofilm is developed, so that the wear rates are often lower than are recorded at 400 °C. |
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Plasma electrolytic oxidation of zircaloy-4 in a mixed alkaline electrolyte |
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Fajar Al Afghani, Anawati Anawati |
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Indonesia |
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https://doi.org/10.1016/j.surfcoat.2021.127786
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• PEO of zircaloy-4 was successfully performed at 30, 50, and 70 mA/cm2.
• The coating was composed of amorphous SiO2 and crystalline t- and m-ZrO2 phases. • The fraction of m decreased while t increased with increasing current density. • The highest abrasive wear and corrosion resistances were obtained in 70 mA/cm2 due to low porosity and high content of t-ZrO2. |
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Characteristics of coating resulted from plasma electrolytic oxidation (PEO) of zircaloy-4 in an electrolyte containing phosphate, silicate, and hydroxide were investigated. The mixed electrolyte is proposed to reduce power consumption. PEO was conducted in a DC mode at a current density of 30, 50, and 70 mA/cm2. Plasma was generated at a relatively low breakdown voltage of 150 V, independent of the current density. The resulting coating was composed of amorphous SiO2 and crystalline monoclinic (m) and tetragonal (t) ZrO2 phases. XRD analysis revealed that the porous outer layer developed at 30 mA/cm2 was dominated by the m phase. The percentage of the m phase decreased while the t phase increased with increasing current density. Therefore, the coating formed at 70 mA/cm2 showed the highest abrasive wear resistance, three times higher than the substrate. Similarly, the polarization curve and electrochemical impedance spectroscopy showed that the highest corrosion resistance, more than two orders of magnitude higher than the substrate, was obtained in the coated-70 mA/cm2 specimen. The use of low power and a mixed electrolyte is beneficial in producing PEO coating with high wear resistance and excellent anti-corrosion characteristic. |
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Plasma duplex treatment influence on the tribological properties of the UNS S32760 stainless steel |
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P.R.Q. de Almeida, P.L.C. Serra, M.R. Danelon, L.S. Rossino, T.H.C. Costa, M.C. Feitor, A.S. de Menezes, R.M. Nascimento, R.M. Sousa, F.R. Marciano |
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Btrazil |
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https://doi.org/10.1016/j.surfcoat.2021.127774
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• UNS S32760 samples were plasma nitrided and then received TiN films.
• The coatings composition was confirmed by Rietveld Refinement method. • The nitriding step provided excellent adhesion conditions, HF1, for TiN films. • Wear volumes were significantly reduced with the duplex treatment application. • The treatments contributed to decrease the tendency to wear by scratching. |
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Super duplex stainless steels are widely used in harsh environments due to their high corrosion resistance. However, the improvement of their tribological properties can contribute to a better performance of these materials in service. In this regard, this study aimed to evaluate the application influence of duplex treatment on the tribological properties of the UNS S32760 super duplex stainless steel. Two treatment times, 2 h and 4 h, were studied for both the nitriding step and the cathodic cage plasma deposition step. The results showed that the combination of the nitrided layer and the TiN film, confirmed with the application of Rietveld refinement on the XRD data, contributes to the wear volume decrease by up to 9.41 times. This behaviour was associated with the increase in surface microhardness and the excellent adhesion conditions (HF1) presented by the film deposited over the nitrided layer. The film provided a change in the wear mechanism, evidenced by the reduction in the tendency to wear by scratches. Additionally, was observed the presence of lower oxygen content in the wear region of the treated samples, that can be associated a lower heating of the samples during the test. Thus, the duplex treatment has a great application potential for improving the wear resistance of UNS S32760 steel. |
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Power controlled microstructure and infrared properties of air plasma spraying based on YSZ coatings |
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Juhang Yin, Chao Wang, Hanyu Zheng, Li Zhang, Min Zhang, Xiaodong Ma, Tao Shen, Wenting Zhang, Xiaolong Weng, Shaoliang Jiang, Xiaofeng Zhang, Jiafeng Fan, Chunming Deng, Longjiang Deng |
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China, USA |
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https://doi.org/10.1016/j.surfcoat.2021.127768
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• With increase of the porosity, the infrared emissivity decreases though.
• In simulation, the large the porosity of YSZ coating have the great energy of backscattering. • The extinction coefficient of YSZ coating increases with the increase of porosity. |
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Yttria stabilized zirconia (YSZ) exhibits low thermal conductivity as well as high electrical conductivity in a high temperature environment, which plays an important role in the infrared stealth field. This work studied YSZ coatings with different porosities by controlling the spraying power of air plasma spraying (APS), while analyzing the influence of spraying power on the microstructure and crystalline structure of the YSZ coating, and the mechanism of porosity on the infrared emissivity of the YSZ coating. The results showed that the cross-sectional porosity decreased from 19% to 9% with a spraying power increase from 55 kW to 95 kW. However, the infrared emissivity of the coatings at 3–5 μm decreased from 0.56 to 0.46 with porosity increases. Through the analysis of model simulation and theoretical calculation, it was found that YSZ coatings with higher porosity levels had more scatterers in the coating, which increased the backscattering of the coating and reduced the emissivity. The results showed that YSZ as a low emissivity coating has a dual effect and more potential in high temperature infrared stealth. |
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Microstructure and mechanical properties of plasma transferred wire arc spray coating on aluminum cylinder bores |
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J. Zhang, D.C. Saha, H. Jahed |
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Canada |
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https://doi.org/10.1016/j.surfcoat.2021.127757
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• PTWA alloyed steel coating on die cast aluminum alloy cylinder bores was studied.
• Steel coating contains microcracks, various oxides, and re-solidified particles. • Visible IMCs are not present, indicating lack of diffusional phase transformation. • Residual stress is compressive in the coating and around 100 MPa at the interface. • Maximum coating bending strength is 1480 ± 108 MPa with three failure modes. |
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This study examines the microstructure and mechanical properties of plasma transferred wire arc (PTWA) coating of typical alloyed steel, deposited on diecast aluminum alloy cylinder bores. The coating surface and microstructure were characterized in terms of surface roughness, features (i.e., defects, splats formation mechanisms, distribution of oxides, re-solidified particles, and interfacial metallurgical bonding) using laser scanning confocal microscope, scanning and transmission electron microscope (SEM and TEM). Residual stress through the thickness of the coating was measured using X-ray diffraction (XRD) and hole-drilling method. In post-processed samples, compressive residual stress was measured throughout the coating with a value close to 100 MPa at the interface, resulting from the thermal mismatch between coating and substrate materials. In terms of mechanical properties, coating hardness was estimated at both the micro- and nanoscale and examined the influence of microstructure inhomogeneity on the mechanical performance and failure modes. Three-point bending tests and consequent analysis using the equivalent section method yielded stress-strain properties for both the substrate and coating materials with a maximum coating strength averaging 1480 ± 108 MPa. SEM observation of fracture surfaces showed three modes of failure involving coating delamination and breakage, which is related to the deposition process and the various features within the coating. |
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Effect of nanoscopic defects on barrier performance of thin films deposited by plasma-enhanced atomic layer deposition on flexible polymers |
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Réka Lilla Kovács, Szilvia Gyöngyösi, Gábor Langer, Eszter Baradács, Lajos Daróczi, Péter Barkóczy, Zoltán Erdélyi |
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Hungary |
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https://doi.org/10.1016/j.tsf.2021.138960
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• In-situ barrier layer cracking-gas permeation measurement method.
• CO2 permeability of as-deposited and in-situ cracked Al2O3 thin layers. • CO2 permeability of cracked films decreases exponentially with increasing film thickness. • Computer simulation, fully analytical model of the gas permeability of defective barrier layers. |
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Penetration paths caused by nanoscopic defects in plasma-enhanced atomic layer deposited (PEALD) Al2O3 thin films could increase their transmission rate, mechanical limitations could impair their encapsulation utility. In contrast, this phenomenon could be beneficial in the case of polymer electrolyte fuel cells containing a proton exchange membrane, where water retention in the membrane is crucial for efficient transport of hydrated ions. Nanocracks in the deposited layer can act as nanovalves at low humidity levels and maintain the suitable level of hydration for the membrane. This paper presents the results of a unique, in situ oxide film cracking-gas permeation measurements on 25–100 nm Al2O3 coated low-density polyethylene. The developed measurement chamber enables the bulging of the substrate/coating system, which initiates the cracking of the coating. Under the same mechanical load, the permeability decreases exponentially with film thickness: quadrupling the film thickness reduced it by a tenth. Simulation-based empirical models on gas diffusion through defected barrier layers are summarized, and an analytical model is constructed instead. We have also carried out simulations to help understand the processes. The derived analytical equations perfectly describe the literature data, our simulations, and experimental results. The introduced technical setup, experimental and theoretical work may open further perspectives in understanding the behavior of barrier layers under mechanical loading. |
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Plasma-assisted template removal and consolidation of silica coatings on polycarbonate |
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Lenke Kócs, András Késmárki, Szilvia Klébert, János Madarász, Zoltán Hórvölgyi |
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Hungary |
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https://doi.org/10.1016/j.tsf.2021.138976
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• Mesoporous silica coatings with face-centred cubic symmetry were obtained.
• Abrasion-resistant silica coatings on polycarbonate were prepared with air plasma. • Oxygen plasma is a substitute for calcination or solvent extraction of templates. • Silica thin films are resistant against complex simulated environmental conditions. |
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This paper presents a fast and efficient method of removing the template from silica thin films on polycarbonate. Radiofrequency-generated oxygen plasma induced the decomposition of the non-ionic surfactant. The reference samples were silica coatings on silicon, which had different pore sizes. We removed the surfactant by solvent extraction and calcination from these samples. Grazing incidence angle X-ray diffraction analysis shows a highly ordered arrangement of mesopores. The formation of the face-centred cubic structure of mesopores is independent of the substrate and the template removal method. Atomic force microscopy analysis showed open-pore channels after oxygen plasma etching. It also proved that the ammonia treatment increases the hardness of the layer. A short air-plasma treatment is effective for the consolidation of the silica layer and improves the abrasion resistance of the layer on polycarbonate. Air plasma treatment is an alternative to the long heat treatment process. We performed environmental tests according to the relevant ISO standards for optical coatings. Air plasma treated silica coatings have passed all the weathering tests. Therefore, it can be used in outdoor applications, such as a protective layer for the plastic cover of LED street lights. These thin films on polycarbonate have at least one year of service life and are weather-resistant. Plasma treatment can consolidate the silica network and the thin films on polycarbonate have high light transmission (T = 98.8 %). |
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Repetitively pulsed nanosecond discharge plasma decay in propane–oxygen gas mixture in the presence of a heating electric field |
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M.A. Popov, V. Kochetov, A.Y. Starikovskiy, N.L. Aleksandrov |
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Russian Federation, USA |
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https://doi.org/10.1016/j.combustflame.2021.111611
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Plasma decay in the afterglow of a repetitively pulsed nanosecond discharge in a stoichiometric propane–oxygen mixture was experimentally investigated when a weak heating DC electric field was applied and in its absence. The discharge was ignited at room gas temperature and a pressure of 1–2 Torr and was characterized by low specific energy inputs (<0.004 eV per molecule in one pulse). Using microwave interferometry, the temporal evolution of the electron density during plasma decay was studied, and the effective recombination coefficients were obtained from data processing. It was shown that the rate of plasma decay behaved in a non-monotonic manner with increasing degree of propane oxidation; at first the decay rate grew, then passed through a maximum, fell and saturated in the limit of a large (~2000) number of pulses. In this limit, the effect of the heating DC electric field on the plasma decay decreased with approaching chemical equilibrium. Numerical simulation of the observed effects was performed for low and high oxidation degrees of propane taking into account changes in the composition of positive ions in the plasma. Good agreement was obtained between measurements and calculations of the electron density during plasma decay in these cases. It was shown that the formation of cluster ions in the discharge afterglow plays a fundamental role. The plasma decay was controlled by electron recombination with hydrocarbon cluster ion at low oxidation degree of propane and with water cluster (hydrated) ions at high oxidation degree. A hypothesis was proposed to explain the observed nonmonotonic behavior of the plasma decay rate with an increase in the propane oxidation in the discharge, based on the formation of hydrated hydrocarbon ions CxHy+(H2O)k at moderate oxidation degrees. |
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Low-Temperature Atmospheric Pressure Plasma Processes for the Deposition of Nanocomposite Coatings |
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Antonella Uricchio, Fiorenza Fanelli |
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Italy |
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https://doi.org/10.3390/pr9112069 |
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Low-temperature atmospheric pressure (AP) plasma technologies have recently proven to offer a range of interesting opportunities for the preparation of a variety of nanocomposite (NC) coatings with different chemical compositions, structures, and morphologies. Since the late 2000s, numerous strategies have been implemented for the deposition of this intriguing class of coatings by using both direct and remote AP plasma sources. Interestingly, considerable progress has been made in the development of aerosol-assisted deposition processes in which the use of either precursor solutions or nanoparticle dispersions in aerosol form allows greatly widening the range of constituents that can be combined in the plasma-deposited NC films. This review summarizes the research published on this topic so far and, specifically, aims to present a concise survey of the developed plasma processes, with particular focus on their optimization as well as on the structural and functional properties of the NC coatings to which they provide access. Current challenges and opportunities are also briefly discussed to give an outlook on possible future research directions. |
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Solar-light elimination of various dye effluents using plasmon AgBrCl solid solution on carbon defects-MWCNTs modified with DBD-plasma: Nano-hybrid photocatalyst and ultrasonic precipitation design |
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Nazanin Mikaeeli, Mohammad Haghighi, Esmaei lFatehifar, Maryam Shabani |
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Iran |
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https://doi.org/10.1016/j.apsusc.2021.151433
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• Synthesis of the AgBrCl over carbon defects-MWCNTs modified with DBD-plasma.
• Fabrication by the facile one-pot sonochemical precipitation method. • Enhancing photocatalyst properties using of plasma modified carbon defects-CNTs. • Confirmation the hetero-meso-structure for AgBrCl/CNT(PT)(1%) nanophotocatalyst. • Highest degradation efficiency of various dyes over AgBrCl/CNT(PT)(1%). • Higher spectrum response and the effective separation of charge carriers. |
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AgBr0.75Cl0.25 solid solution on carbon defects-MWCNTs, modifying with DBD-plasma, was fabricated via the sono-precipitation method, employing to degrade dye pollutants under simulated sunlight. XRD, FTIR, Raman, BET-BJH, FESEM, TEM, DRS and PL analyses were applied to characterize the nanophotocatalyst. Results illustrated the improvement of band gap (2.19 eV), existence of SPR property, reducing the recombination rate, improving the separation and transmission of charge carriers, and increasing the access to active sites as a result of the formation of AgBr0.75Cl0.25 solid solution over carbon defects-MWCNTs. Besides, existing MWCNTs along with carbon defects as a result of using DBD-plasma, in AgBrCl/CNT(PT)(1%) structure led to well dispersion, decreasing agglomeration, smaller particles, formation of hydroxyl, epoxy and carboxyl groups on the surface and stronger bonding, trapping of excitons, increasing separation of them, and increasing the access to active sites. So that, the excellent photocatalytic performance was obtained over AgBrCl/CNT(PT)(1%) for the degradation of 50 mg/L crystal violet (87.5%), rhodamine B (95.6%) and methyl orange (81.9%) during 180 min. Reusability was investigated in four cycles; and a reaction mechanism for the photodegradation was suggested. |
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Nitrogen plasma activation of cactus-like MnO2 grown on carbon cloth for high-mass loading asymmetric supercapacitors |
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Weiliang Zeng, Hongying Quan, Jiangyan Meng, Wei Wei, Meng Liu, Dezhi Chen |
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China |
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https://doi.org/10.1016/j.apsusc.2021.151323
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• Nitrogen plasma can fabricate disorder layers (3 ∼ 5 nm) on the surface of α-MnO2.
• Abundant oxygen vacancies appeared in the disorder layers of α-MnO2. • Oxygen vacancies improved the capacitive performance of α-MnO2 even at high mass loading (12 mg cm−2). |
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The electrochemical performance of high theoretical capacitance MnO2 is usually restricted to low mass loading electrode due to the slower electron/ion diffusion kinetics in dense electrodes. Defect engineering has been supposed to an effective way to improve the capacitive performance of transition metal oxides. Herein, cactus-like structure MnO2 was grown on carbon cloth (CC) and treated with N2-plasma to obtain the N-MnO2 electrode with high mass loading of 12 mg cm−2. Benefiting from the hierarchical structure and rich oxygen vacancies, the as-prepared N-MnO2 electrode delivered a high mass specific capacitance of 443F g−1 and a high areal capacitance of 5320 mF cm−2. Furthermore, the N-MnO2 electrode released an excellent rate capability with 71.8% capacitance retention at 20 mA cm−2 as well as gratifying cycling life with 96 % capacitance retention after 8 000 cycles at 20 mA cm−2. Moreover, an asymmetrical supercapacitor device assembled by N-MnO2 and activated CC can achieve a high energy density of 0.56 mWh cm−2 (46 Wh kg−1) at the power density of 5.14 mW cm−2 (420 W kg−1) with good cycle stability. Such facile N2-plasma treatment for defect engineering shows great potential in the rational design for advanced supercapacitor electrodes with high mass loading. |
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Multiscale mechanics of yttria film formation during plasma spray coating |
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Youngoh Kim, JaeHwang Kim, Jang-Woo Han, Joonmyung Choi |
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Korea |
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https://doi.org/10.1016/j.apsusc.2021.151416
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• A multi-scale analysis method for the plasma spray coating process is developed.
• The mechanical properties of films are predicted through DSMC and MD simulations. • The increase in powder feed let the sprayed particle have an oblique incidence angle. • The oblique incident trajectory reduces the ionic bond density on the Y-O-Al network. |
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In this study, we proposed a multiscale analysis method that integrates the direct simulation Monte Carlo (DSMC) method and all-atom molecular dynamics (MD) simulation to comprehend the process of unsteady plasma spray coating of yttria nanoparticles (YNPs) on an alumina substrate. The correlation between the increase in the powder feed rate and growth mechanism of the film microstructure was obtained by solving the collisions of the sprayed YNPs and corresponding spatial trajectories. The results showed that higher powder feed rates form a wider spray cone angle, and a reduction in spray distance increased the probability of powder impinging normal to the substrate. This also explained the changes in the interfacial adhesion and hardness of the films with the powder feed rate and spray distance observed in the experiments. In particular, vertically incident YNPs not only constituted the densest bulk layer, but also contributed to strong adhesion by increasing the probability of generating Y-O-Al binding structures at the interface. The findings were the first to examine the complexity of chemo-mechanical behavior between spatial particle trajectories and facing material, thus throwing light on an important factor in the quality of sprayed ceramic coatings. |
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Microscale investigation on the wettability and bonding mechanism of oxygen plasma-treated PDMS microfluidic chip |
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Bingyan Jiang, Hongyu Guo, Dan Chen, Mingyong Zhou |
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China |
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https://doi.org/10.1016/j.apsusc.2021.151704
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• MD model of plasma-treated PDMS based on the experimental result is constructed.
• The change in wettability mainly comes from the exposure of OH and CH2OH groups. • The intermolecular interaction plays a decisive role at the modified interface. • Oxygen plasma treatment improves the interaction and bonding strength of PDMS chip. |
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The bonding of polydimethylsiloxane (PDMS) microfluidic chip is one of the major concerns during the fabrication process. Plasma treatment can be applied to produce the hydrophilic groups, thus forming an irreversible bonding permanently. The surface wettability and bonding mechanism at the microscale level after plasma treatment need further investigation. In this study, the contact angle, surface morphology and the chemical composition of PDMS surface that were modified by oxygen plasma treatment were experimentally analyzed. Accordingly, molecular dynamics simulation models were constructed to investigate the wettability and bonding mechanism. Experimental results show that the contact angle decreases rapidly with the treatment time. The change in wettability mainly comes from the exposure of hydrophilic OH and CH2OH groups on silicon atoms, while the slight change in surface morphology can be negligible. With the help of hydroxyl groups, the spreading process of water droplet on the PDMS surface becomes much quicker because strong intermolecular interactions are generated. During the bonding process, atoms in both layers are gradually pushed towards the interface and penetrate each other, thus forming a reliable bonding at the interface. It is revealed in the debonding simulation that the plasma treatment on PDMS surface improves the bonding strength. |
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Surface roughening of Ti-6Al-7Nb alloy plasma nitrided at cathode potential |
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J. Morgiel, Ł. Maj, K. Szymkiewicz, M. Pomorska, P. Ozga, D. Toboła, M. Tarnowski, T. Wierzchoń |
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Poland |
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https://doi.org/10.1016/j.apsusc.2021.151639
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• Lowering plasma nitriding temperature of Ti-6Al-7Nb minimized surface roughness.
• Surface roughening was studied both by plan-view and cross-section observations. • Nitriding at ~600 °C induces planar growth of TiN reproducing substrate morphology. • Nitriding in 600–800 °C range causes competitive growth and spalling of TiN. • Mechanism of development of surface roughness during plasma nitriding was proposed. |
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A plasma nitriding of titanium alloys is very efficient method of their surface hardness and wear resistance improvement without compromising a core strength of the treated elements. The surface roughening increasing with the temperature of this treatment is a major obstacle on the way toward production of the fine quality products. Confronting of the roughness measurements performed at different scales with complementary plan-view surface observations (OM, SEM/SE, FIB/SE, AFM) and cross-section (TEM) ones, focused on description of the surface defects, allowed the mechanism of their development to be explained. Namely, the TiN layer produced at lower temperatures (~620 °C) grows predominantly with a flat front, roughly reproducing the substrate morphology, while at intermediate and higher temperatures (680 °C−830 °C) it is a subject of severe self-spalling of the upper part of this layer. It means that simultaneous hardening and preservation of a high surface quality of Ti-6Al-7Nb after CP-PN is possible only during the plasma nitriding performed at the temperatures close to 600 °C. Additionally, a strong self-spalling of the upper part of the TiN layer during this treatment at higher temperatures means that only its remaining part, growing toward the core, could eventually serve as a corrosion protection barrier. |
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Phase stability, thermal shock behavior and CMAS corrosion resistance of Yb2O3-Y2O3 co-stabilized zirconia thermal barrier coatings prepared by atmospheric plasma spraying |
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Huanjie Fang, Weize Wang, Zining Yang, Ting Yang, Yihao Wang, Jibo Huang, Dongdong Ye |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127864
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• A double-ceramic-layer (DCL) coating comprised of dense layer was prepared.
• The YbYSZ material exhibits higher resistance to high temperature. • The YbYSZ coatings have a longest thermal shock lifetime comparatively. • The DCL-YbYSZ coatings show enhanced CMAS resistance due to high chemical inertness. |
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Rare-earth element doping has been extensively employed as one of the effective methods to enhance the durability of thermal barrier coatings (TBCs). In present study, ytterbia and yttria co-stabilized zirconia (YbYSZ) coatings and corresponding double-ceramic-layer (DCL) coatings comprised of a dense layer were produced by atmospheric plasma spraying. And the service capability including phase stability, thermal shock behavior and CMAS resistance were systemically evaluated. After heat treatment at 1500 °C for various durations, less monoclinic phase can be found in YbYSZ specimen, indicating excellent phase stability at high temperature. In the thermal shock test, the conventional YbYSZ coatings show a longest thermal shock lifetime, which increases by ~10% as compared with that of conventional yttria-stabilized ZrO2 (YSZ) coatings. CMAS corrosion resistance of DCL coatings was studied using an isothermal corrosion test at 1300 °C. The results show that YbYSZ systems with a dense layer performed a high resistibility to CMAS corrosion, and less damage can be observed in coatings as well as smaller infiltration depth within the same time. |
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Etching and annealing treatment to improve the plasma-deposited SiOx film adhesion force |
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Ruixue Wang, Zhangchuang Xia, Xianghao Kong, Lihong Liang, Kostya (Ken) Ostrikov |
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China, Australia |
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https://doi.org/10.1016/j.surfcoat.2021.127840
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• The plasma etching and annealing processes improved the adhesion force between SiOx film and substrate by 5 times;
• A rich oxygen contained and randomly oriented SiOx film was obtained after etching and annealing processes; • The SiOx film with a high oxidation degree possesses a high relative dielectric constant value; • The SiOx deposited sample showed a 119% improvement in the lift-off voltage compared to that of the bare electrode. |
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In this paper, an atmospheric pressure plasma jet driven by an AC power supply was applied for SiOx film deposition on a metal surface. To improve the adhesion strength between the film and substrate, the processes of plasma etching and annealing were applied. The deposited SiOx film properties, including film thickness, surface morphology, chemical composition and electrical properties, were studied systematically. In addition, the deposited film was used for the metal particle lift-off voltage in a gas-insulated line (GIL) system. Our results showed that the adhesion strength between the film and substrate was 5 times higher in the films subjected to plasma etching and annealing treatment than that in the untreated group. The high oxygen content attained in the SiOx film after the etching and annealing processes was responsible for the adhesion force improvement. The composition changes in the film also increased the relative constant value, which was in good agreement with the metal particle lift-off voltage results. After thermal annealing, the sample showed a 119% improvement in the lift-off voltage compared to that of the bare electrode. |
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Effect of Cr2O3 addition on mechanical and tribological properties of atmospheric plasma-sprayed NiAl-Bi2O3 composite coatings |
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Huwei Sun, Gewen Yi, Shanhong Wan, Charlie Kong, Shengyu Zhu, Liuyang Bai, Jun Yang |
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China, Australia |
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https://doi.org/10.1016/j.surfcoat.2021.127818
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• NiAl-Bi2O3 coatings with different amount of Cr2O3 were prepared by the APS process.
• Proper amount of Cr2O3 enhanced the mechanical capability and wear resistance. • The consolidation of Cr2O3 on tribo-layer supported the lubricity of Bi2O3 and NiO. • Grain refinement and evolution of Bi2O3, Cr2O3 and NiO governed the resulting wear. |
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Existing atmospheric plasma sprayed NiAl-20 wt% Bi2O3 composite coating displays the poor mechanical properties, thus this paper investigated the influence of adding different fractions of Cr2O3 on microstructural alteration and tribological behavior of NiAl-20 wt% Bi2O3 coating at RT, 400 °C and 800 °C. Desirable lubrication of NiAl-Bi2O3-Cr2O3 coating primarily resulted from Bi2O3 by its virtues of soft, low shear stress, and diffusion with temperature stimulus. Instead, Cr2O3 addition improved the wear resistance significantly, which was attributed to the increase of hardness and plastic deformation resistance, especially when 15 wt% Cr2O3 was adopted. The relationship between the Cr2O3 addition and relevant composition migration and mechanical transition on the worn surface at varying temperatures was further researched in this work. |
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Heat treatment for microstructure and mechanical properties improvement of powder plasma arc melted 17Cr-2Ni steel containing boron |
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Yan Liu, Tong Wang, Ze-yu Li, Jian-xun Zhang |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127742
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• Heat treatment of plasma arc melted 17Cr-2Ni steel containing boron was evaluated.
• Carbides were dissolved mainly in the homogenization treatment stage. • MX-type nanoprecipitate existed in intragranular ferrite matrix after heat treatment. • Two sizes of intragranular carbides existed in the isothermal quenched samples. • Modification of martensite is main manner to improve its mechanical properties. |
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Plasma arc melted 17Cr-2Ni steel containing boron was studied under conditions of as-deposited and heat-treated state in this paper. The deposits showed high hardness and strength. However, it contained carbides network and martensite lath which are known as a deleterious phase to both mechanical and corrosion properties of steels. Various double austenitizing treatments were performed to improve the mechanical properties of deposits. At first, to reduce the degradation caused by carbides network, the deposits were subjected to different austenitizing temperatures of 1000, 1050 and 1140 °C during the homogenizing treatment. Homogenizing at 1140 °C was selected due to significant dissolution of carbides network and intragranular large size carbides (>2 μm). Second, to reduce the influence of martensite lath on the mechanical properties, the samples were subjected to isothermal quenching (IQ) and tempering at 420 °C for 60 min following the double austenitizing treatment, which were referred to as IQ1140 and T1140, respectively. Different from the microstructure of tempered martensite lath structure of the T1140, the microstructure of pearlite with carbide particles size less than 500 nm was found in IQ1140, which was verified to improve the tensile strength and ductility of steels from 1486 MPa and 0.5% to 1708 MPa and 3.8%, respectively. In addition, MX-type nanoprecipitate were found in the ferrite matrix of heat-treated steels. The deposits heat-treated by IQ1140 process was proved to have comprehensive high hardness, high strength and a certain ductility, with an improvement of 11%, 15% and 660% to the ones of deposits, respectively. |
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Femtosecond laser surface roughening and pulsed plasma polymerization duplex treatment on medical-grade stainless steel substrates for orthodontic purpose |
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Cheng-Wie Lin, Ping-Yen Hsieh, Chia-Man Chou, Chi-Jen Chung, Ju-Liang He |
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Taiwan |
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https://doi.org/10.1016/j.surfcoat.2021.127819
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This study developed a surface modification technique to obtain nearly superamphiphobic films on AISI 304 stainless steel substrates, which are usually made into dental appliances in orthodontics for malocclusion. Direct fabrication of micro- and nanoscale roughened surfaces on stainless steel substrates were treated using femtosecond laser (FL) processing. Subsequently, pulsed plasma polymerization (P3) was adopted using hexamethyldisiloxane (C6H18OSi2) and octafluorocyclobutane (C4F8) as the precursors to deposit siloxane and fluorocarbon stacking films. The surface characteristics of the deposited films were examined, and in vitro cytotoxicity and antimicrobial tests were performed.
Experimental results showed that the surfaces treated by FL and P3 processes exhibited nearly superamphiphobicity with water apparent contact angle (CA) 160°, advancing CA 161°, receding CA160°, contact angle hysteresis (CAH) 1°; sunflower oil apparent contact angle 146°, advancing CA 141°, receding CA137°, CAH 4°; and hexadecane oil apparent contact angle 124°, advancing CA 118°, receding CA113°, contact angle hysteresis CAH 5°, respectively. The nearly superamphiphobicity are attributed to the synergistic effects of pre-roughening by the FL process and post-flourinating with siloxane and fluorocarbon coating by the P3 process, which were consistent with the results of scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared analyses. In addition, the steel wool abrasion test exhibited the film's surface wear resistance, and in vitro tests revealed the film's non-cytotoxicity and effective inhibition of bacterial growth. Thus, the nearly superamphiphobic coating may be beneficial for applications in orthodontics. |
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Mitigation of chloride driven stress corrosion cracking susceptibility of 316L austenitic stainless steel using plasma sprayed TiO2 coating
Minderung der Anfälligkeit für chloridbedingte Spannungsrisskorrosion von austenitischem Edelstahl 316L durch plasmagespritzte TiO2-Beschichtung |
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K. Kumar, S. S. Bhadauria, A. P. Singh |
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India |
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https://doi.org/10.1002/mawe.202100199 |
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The present study proposes a protective TiO2 coating against chloride driven stress corrosion cracking problem of 316L austenitic stainless steel. To test the performance of the proposed coating, the severe chloride-based boiling magnesium chloride solution at 155 °C was chosen. For experimentation, the constant strain-based U-bend specimens were coated with TiO2 using atmospheric plasma spray method. The results indicated higher resistance by TiO2 coated specimens against stress corrosion cracking problem, while the bare specimens experienced severe damage in the boiling magnesium chloride solution under various strain loading configurations. The coating-electrolyte system of TiO2 coated sample demonstrated over seven times higher resistance, eventually led to reduction in corrosion rate over fifteen times compared to the bare 316L stainless steel in the boiling magnesium chloride solution. This improved performance of the coated 316L stainless steel is attributed to inhibition of outward diffusion of iron-chromium-nickel in the corrosive environment and the high chemical stability of TiO2. |
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Ultrafine-grained twinning-induced plasticity steel prepared by mechanical alloying and spark plasma sintering |
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Dan Wang, Kun Wang, Xinfu Wang |
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China |
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https://doi.org/10.1016/j.msea.2021.142302
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A twinning-induced plasticity (TWIP) steel was prepared by mechanical alloying and spark plasma sintering (SPS), and its microstructure and mechanical behavior were examined. The ultrahigh microhardness and considerable tensile strength of the sintered bulk sample were mainly attributed to grain-size strengthening and particle strengthening by numerous Mn-rich particles dispersed in the matrix. Micropores coupled with large internal inclusions easily produced cracks in the bulk sample under uniaxial tensile stress, resulting in poor ductility with rapid intergranular brittle fracture. The ductility of the material showed significant improvement with the elongation increased from 4% to 13% after annealing the bulk sample at 850 °C for 1 h. The size of the inclusions in the annealed sample dramatically reduced and several small dimples with high densities and depths were formed, presenting a mixed fracture mode in which intergranular fracture was the dominant mechanism, whereas transgranular fracture was the supplementary mechanism. |
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Comparing chemical and plasma modification of stainless steel surfaces – Relevance for adsorption of adhesion promotor vinyltrimethoxysilane (VTMS) |
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Dustin Quinones, Kai Braun, Alfred Meixner, Thomas Chassé |
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Germany |
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https://doi.org/10.1016/j.apsusc.2021.151674
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• Surface modification of V2A stainless steel by plasma and NaOH treatment investigated by XPS.
• Higher influence on the surface modification due to NaOH treatment. • Concentration of NaOH identified as the most significant parameter for modification. • Surface oxidation has an influence on adhesion promoter VTMS bonding. • Functional groups of VTMS on steel were detected using SERS. |
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Coated stainless steel surfaces with silane compound coupling agent are implemented in many industrial applications. For vinyltrimethoxysilane (VTMS) adsorption optimization, surface modification of stainless steel type V2A was performed with plasma, ozone and in sodium hydroxide (NaOH) solutions. Subsequent a systematic study of a central composite design of experiments (DoE) accomplished with X–ray photoelectron spectroscopy (XPS) data. Similar results in ozone, oxygen (O2)–, and water (H2O)–plasma treatment led to a detailed presentation of the results from the O2–plasma and NaOH treatment. Treatment effects on the surface roughness were determined using atomic force microscopy (AFM) and the functional groups of VTMS on the surface with surface enhanced Raman spectroscopy (SERS). All treatments resulted to a reduction of C and a higher oxidized surface whereas the Fe/Cr–ratio and OH-content were changing significantly after NaOH treatment. Only the root mean squared (RMS)–values calculated from the AFM images of NaOH treated V2A samples indicated an increased coverage of VTMS after longer treatment time in higher concentrated NaOH solutions. The results of this study enable setting the amount of VTMS bonding to the surface of V2A due to NaOH pretreatment. |
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Significant enhancement of electrical conductivity by incorporating carbon fiber into CoSb3 thermoelectric skutterudite fabricated by spark plasma sintering method |
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Ridwone Hossain, Al Jumlat Ahmed, Frank. F. Yun, Lina Sang, Sheik Md Kazi Nazrul Islam, Guangsai Yang, Michael B. Cortie, Xiaolin Wang |
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Australia |
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https://doi.org/10.1007/s10853-021-06588-5 |
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The effects of carbon fiber additions on the electrical and thermoelectric performance in p-type CoSb3-based skutterudite are reported. A threefold enhancement in electrical conductivity is found. Two different explanations for the increased electrical conductivity are considered: Either carbon atoms enter the CoSb3 lattice as a dopant that makes it more and more conductive, or the increase in conductivity is due to electrical percolation of the carbon fibers in the composite. X-ray diffraction data show that the lattice parameter of the CoSb3 is not affected by the presence of the carbon fiber; however, adding carbon is associated with precipitation of 20 wt. % elemental Sb. DFT calculations show that the enthalpy of formation of a solid solution of carbon (interstitial or as a substitution for Sb) is slightly positive. This would be offset by an increased entropy contribution at higher temperatures, so the free energy change overall is likely to be favorable. All of the results support an explanation based on an improved electrical conductivity of a very dilute solid solution of C in CoSb3. The average thermoelectric parameters of the composite material, including heat conductivity, average composite Seebeck coefficient, Hall effect, carrier mobility, and carrier concentration, were influenced by the carbon addition. Unfortunately, the effects largely cancel each other so that the overall zT of the composite was not improved. |
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A critical review on spark plasma sintering of copper and its alloys |
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Mohammad Abedi, Atefeh Asadi, Stepan Vorotilo, Alexander S. Mukasyan |
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Russia, USA |
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https://doi.org/10.1007/s10853-021-06556-z |
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Copper and its alloys have been in the service of humankind earlier than any other metal throughout history. In the present review, all aspects of the SPS of copper and its alloys are comprehensively investigated, and their potential effects on the microstructure and properties of alloys are thoroughly reviewed. In this regard, the densification phenomenon during SPS treatment is fully investigated. The effects of raw powder characteristics involving particle size, contamination content, and powder morphology on the sinterability of these materials are examined. Then, the influence of SPS operation parameters consisting of pressure, heating rate, dwelling time, pulsed electrical current, electrical pulses pattern, sintering temperature, and sintering tooling on densification of these materials is extensively discussed. Furthermore, the microstructure evolution and grain growth behaviors during SPS are explored. In addition, current challenges and future perspectives of this field are addressed. |
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Comparison of the anticancer effects between helium plasma jets and electrochemical treatment (EChT) |
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Dingxin Liu, Zifeng Wang, Zeyu Chen, Dehui Xu, Min Chen, Jinkun Chen, Mengying Zhu, Hao Zhang, Xiaohua Wang, Michael G. Kong, Mingzhe Rong |
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China |
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https://doi.org/10.1002/ppap.202100087 |
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Cold atmospheric plasma, a promising technology for cancer therapy, can simultaneously induce electrochemistry, which has been widely demonstrated to be effective against cancer. Herein, the anticancer effects of direct current plasma jets and electrochemical circuit are comparatively studied with similar topological structures and average currents. The cell inactivation patterns formed by plasma and electrochemical treatment (EChT) are disparate, and the inactivation is mainly caused by the emission of charged species, helium flow, in situ OH radical production, or local alkalization. The culture medium treated by EChT exerted no sustained anticancer effect, whereas the medium treated by plasma could maintain a strong effect due to the production of more reactive species, suggesting that the electrochemistry does not dominate the plasma inactivation of cancer cells. |
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Low-temperature plasma-jet-activated medium inhibited tumorigenesis of lung adenocarcinoma in a 3D in vitro culture model |
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Ying Li, Yang Lv, Mengxiong Tang, Eun H. Choi, Junjie Wang, Guoqing Lv, Yu Zhu, Shubin Wang, Yajie Liu |
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China |
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https://doi.org/10.1002/ppap.202100049 |
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Many studies have shown, using two-dimensional culture, that low-temperature plasma-jet-activated medium (PAM) inhibits the growth of various tumor cells, whereas its effects and mechanisms in the three-dimensional (3D) culture system remain unclear. In this study, a 3D cell culture model was used to study the inhibition of tumorigenesis of PAM in vitro. Our results showed that PAM significantly suppressed tumor spheroid formation and downregulated stemness-related genes of A549 cells “before,” “during,” and “after” sphere formation. Additionally, we found that the specific signature of reactive oxygen species-induced autophagy was involved in the antiproliferation effect of PAM on A549 spheroids. Our study complemented and extended the application of PAM for its anticancer effects in lung adenocarcinoma cancer. |
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Enhanced transmembrane transport of reactive oxygen species by electroporation effect of plasma |
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Zihao Yang, Dawei Liu |
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China |
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https://doi.org/10.1002/ppap.202100054 |
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Recently, plasma has been proposed as a new efficient tool for various biological and medical applications. The function of plasma is mainly realized through two aspects: Electric field and reactive species. However, because the interactions between plasma and cells are quite complicated, the synergistic effect of electric field and reactive species has not been studied in depth. In this paper, the synergetic effects of electric field and transportation of reactive species on cells are investigated by a two-dimensional finite element model. The exposure of cells to plasma results in the sufficiently high transmembrane voltage (1 V) and electroporation. When the electric field of plasma is less than 104 V/cm, the radius of nanopores generated by plasma increases with the electric field. The further increase of electric field to 105 V/cm does not cause a significant increase of nanopore radius, whereas the pore density increases by five times. The increase of discharge frequency significantly decreases the time needed to generate stable nanopores. The nanopores enhance the diffusion of H2O2 generated by plasma through the cell membrane significantly. Compared with the reality that H2O2 does not freely diffuse across cell membranes, the “generation and enhanced transportation” effect will further expand the application range of plasma medicine. |
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Nebulized plasma-activated water has an effective antimicrobial effect on medically relevant microbial species and maintains its physicochemical properties in tube lengths from 0.1 up to 1.0 m |
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William Chiappim, Aline Sampaio, Felipe Miranda, Gilberto Petraconi, Argemiro da Silva Sobrinho, Paulo Cardoso, Konstantin Kostov, Cristiane Koga-Ito, Rodrigo Pessoa |
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Brazil |
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https://doi.org/10.1002/ppap.202100010 |
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This study applies a proof of concept for future applications in controlling the microbiota in tubes and tracheal appliances used in the respiratory tract. Therefore, the physical–chemical parameters of the plasma-activated and nebulized water (NPAW) are measured in a nebulizer tube with different lengths between 0.1 and 3.0 m. The pH values and oxidation–reduction potential (ORP) do not change during nebulization of PAW over a 1.0 m tube. However, for longer lengths, there is an increase in pH and a decrease in ORP. At 3.0 m, the pH increases approximately 16% compared with the 1.0 m position with a 20% decrease in the ORP values. Hydrogen peroxide (H2O2) measured quantitatively using test strips presents values between 0.5 and 2.0 mg/L for condensed NPAW in different tube lengths between 0.1 and 3.0 m, and maintains the approximate value of 2.0 mg/L in tubes up to 1.0 m, with a reduction proportional to the increase in the length of the tube. The antimicrobial efficacy of NPAW applied for 15 min shows the inactivation of Staphylococcus aureus and Escherichia coli but without significant inactivation of Candida albicans. |
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Gas-phase peroxynitrite generation using dielectric barrier discharge at atmospheric pressure: A prospective sterilizer |
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Kun Liu, Qingsong Duan, Zhenfeng Zheng, Rusen Zhou, Renwu Zhou, Weibin Tang, Patrick Cullen, Kostya (Ken) Ostrikov |
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China, Australia |
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https://doi.org/10.1002/ppap.202100016 |
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Peroxynitrite is an important chemical in the human immune system, which has high biocidal activity and can resist the invasion of pathogens. Currently, in vitro generation of peroxynitrite faces major technological challenges, especially for gas‐phase production, which requires low‐pressure conditions. Here, we report the method of how to generate gas‐phase peroxynitrite at atmospheric pressure using dielectric barrier discharge. Results show that the peroxynitrite concentration positively correlates with energy density. Moreover, Penicillium digitatum, a common fungus contaminant greatly affecting food and fruit preservation, was used as a microbial pathogen model to confirm the biocidal effects of ozone‐free nitrogen oxides under different discharge conditions. The germination inhibition efficiency of P. digitatum is highly likely attributed to the synergistic effect of gaseous peroxynitrite and NO. |
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Depyrogenation using plasmas: A novel approach for endotoxin deactivation using a dielectric barrier discharge at atmospheric pressure |
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Naman Bhatt, Justin Brier-Jones, Duncan Trosan, Cade Brinkley, Joshua Pecoraro, Jann Smallwood, Andrew Crofton, Samuel Hudson, Wolff Kirsch, Katharina Stapelmann, Steven Shannon |
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USA |
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https://doi.org/10.1002/ppap.202100089 |
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Developing a low-cost depyrogenation process is vital in extending the medical applicability of polymers that can be used in medicine. We present an overview of the plasma-based depyrogenation literature and address the need to develop a nonthermal plasma-based depyrogenation process for delicate materials such as chitosan. We present a low-cost plasma apparatus to treat chitosan powder in hermetically sealed bags. We decouple the experiments into two parts: depyrogenation experiments for dried standard endotoxin on glass slides and analysis of chitosan modifications through Fourier-transform infrared spectroscopy. We demonstrate depyrogenation efficacy with up to a 4-log reduction in endotoxin levels and discuss minor changes observed in plasma-treated chitosan. |
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Microstructure and wear properties of atmospheric plasma-sprayed Cr3C2-NiCr composite coatings |
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Dimitry Dzhurinskiy, A. Babu, P. Pathak, A. Elkin, S. Dautov, P. Shornikov |
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Russia |
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https://doi.org/10.1016/j.surfcoat.2021.127904
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Gas turbines and other critical power generation components in coastal areas are susceptible to corrosion and erosion due to solid particle erosion by air-borne particles, humidity, and sea salt, that severely damage the parts. The synergistic effect of both erosion and corrosion can accelerate the material degradation process compared to the individual effects, which might thus lead to less safety, economic loss, and in extreme cases, rapid failure of the components. Cr3C2-NiCr coatings around 150 to 250 μm are commonly used to safeguard these high-valued components. To further enhance the wear resistance of the base coating's secondary particles, B4C and Cr2O3 were added (5 and 10% weight fraction). These coatings were deposited on SS 304-L substrate material by using the atmospheric plasma spray process and Metco TriPlex Pro-210 gun. The microstructure, microhardness, contact stiffness, fracture toughness, sliding wear and dry erosion resistance of the as-deposited coatings were investigated. The results showed that there was a slight phase change Cr3C2-NiCr composite powder after the spraying process. The developed coating has a dense microstructure with relatively low defects such as micro-cracks and pore; high hardness, and toughness. Among all the tested coatings, Cr3C2-NiCr coating, with a 10% weight fraction of Cr2O3 exhibited high wear resistance under all conditions. Cr3C2-NiCr with 10% Cr2O3 exhibited an almost 3.12 times lower wear rate and almost 1.15 times higher erosion resistance than the base coating (Cr3C2-NiCr). This improvement in the wear resistance could be attributed to the improvement in hardness and fracture toughness of the coating material after the addition of hard secondary phases. Morphology of wear samples was analyzed using SEM to investigate the damage mechanism. |
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The rolling-sliding wear behavior and damage mechanism of the rail steel treated by plasma selective quenching |
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Bin Zhang, Deping Yu, Wenjie Song, Keming Peng, Ganyang Wu |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127908 |
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Plasma selective quenching (PSQ) is a promising technique for creating discrete hardened spots (PSQ spots) in the surface layer of the rail to increase its service life. However, cracks occur at one side of the PSQ spots after long-term service, hindering the large-scale application of PSQ treated rails. To reveal the effect of PSQ on the wear behavior of rail steel and damage mechanism of PSQ spots, rail rollers with a thickness of 10 mm were firstly PSQ treated by a laminar plasma jet. Then rolling-sliding contact wear tests were conducted to explore the wear behavior and damage characteristics of the PSQ treated rail rollers. In addition, contact simulation of the contact wear tests was carried out. Results showed that the wear resistance of the PSQ treated rail rollers was improved by 1.26–1.75 times. Such improvement is a result of the increased hardness of the PSQ spots and the reduced plastic deformation of the substrate between two adjacent PSQ spots. Severe cracks and breaks were observed at the entry side of the PSQ spots while no obvious damage appeared at the exit side. The mechanism of such a special pattern of damage was that there was a strain difference at the boundary between the entry side of hardened PSQ spot and the soft substrate while no different strains were produced at the exit side. This paper clarified the damage mechanism of the PSQ spots under the rolling-sliding contact conditions, providing the basis for further improvement on the performance of the PSQ treated rail steel. |
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Microwave plasma oxidation of near-equiatomic NiTi alloy for obtaining low-Ni TiO2 coating |
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Jin Bai, Jie Gao, Meng Zhang, Ke Zheng, Yan Cao, Yamei Mao, Shengwang Yu, Zhiyong Hea |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127883
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In this paper, microwave plasma oxidation (MPO) treatment was carried out on near-equiatomic NiTi alloy for the first time, in order to reduce Ni content and improve cytocompatibility on its surface. The specimens were oxidized at 600 °C for 10, 30, and 60 min, named MPO-1, MPO-2, and MPO-3, respectively. The differences in surface properties, corrosion resistance in DMEM, protein adsorption, and cytocompatibility between the MPO-treated specimens and original substrate were investigated. The results showed that uniform and dense rutile TiO2 coatings with nano-sized granular structures could be formed on the NiTi surface under all MPO time. The Ni/Ti ratio on the MPO-treated surfaces was reduced to ~0.04, close to zero. For MPO-1 and MPO-2, a Ni-rich layer with Ni content of ~70 at.% was formed underneath the outermost TiO2 layer, while an extra high Ni-rich layer with Ni content of ~90 at% was formed between them for MPO-3. Due to the dense TiO2 coating and suitable nanostructure on the surface structure, MPO-2 possessed better corrosion resistance in DMEM and biocompatibility than the original substrate, MPO-1, and MPO-3. Besides, the oxidation rate of MPO treatment is higher than that of other oxidation methods, such as thermal oxidation. That is, the proposed MPO treatment is an oxidation method with high efficiency and effectiveness. |
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Calcium phosphate composites to synergistically promote osteoconduction and corrosion resistance on bone materials via plasma polymerized hexamethyldisilazane coatings |
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Wei-Ting Ting, Tzu-Hsien Yang, Yuan Cheng, Ko-Shao Chen, Shiu-Huey Chou, Mu-Rong Yang, Meng-Jiy Wang |
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Taiwan |
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https://doi.org/10.1016/j.surfcoat.2021.127834
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A facile and effective plasma polymerized hexamethyldisilazane (ppHMDSZ) combining with calcium phosphate (Ca-P) coating to promote osteoconduction meanwhile provide resistance to corrosion is developed in this study. The composites of Ca-P and ppHMDSZ thin films were deposited on bone substitutes to investigate the osteoblast compatibility. The amount of the Ca-P coatings was modulated with a linear deposition rate of 7.37 μg/(cm2∙cycle) by alternative immersion cycles (1, 2, 5, and 10) in solutions containing calcium and phosphate, measured by quartz crystal microbalance (QCM). Importantly, cell behaviors including cell adhesion, proliferation, and functional activity responded positively toward the surface wettability and roughness of the Ca-P layers. Moreover, the human osteoblast cells (hFOB1.19) revealed excellent compatibility on the stainless steel coated with Ca-P/ppHMDSZ composite films. The combination of bioceramics and corrosion resisting plasma polymerized HMDSZ films showed a synergistic effect on the biocompatibility and osteoconductive for bone tissue engineering applications. |
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Evolution of model roughness on quasi-pure aluminum during plasma electrolytic polishing |
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A. Spica, J. Roche, L. Arurault, M. Horville, J. Rolet |
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France |
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https://doi.org/10.1016/j.surfcoat.2021.127839
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The present paper studies the material removal evolution, during Plasma Electrolytic Polishing (PeP), on model roughnesses prepared on 1050 aluminum alloy (AA), i.e. a quasi-pure aluminum, used as a model substrate.
The results obtained in this study confirm the significance of the applied voltage on aluminum removal. In particular, the minimal voltage to be applied to generate the plasma is seen to be above 230 V. Meanwhile, at a higher voltage of 300 V, high quality polishing is obtained. Using this technique, rolling streaks are eliminated rapidly without the workpiece's geometry being adversely affected. Finally, roughness evolution was accurately studied on a series of samples with various well-defined levels of model roughness generated by microindentation. The study shows that only a few minutes of processing are needed to obtain a significant reduction in roughness, even representing up to 70%. Results show also that roughness valleys do not undergo material removal at all as long as peak to valley height remains high enough. As the process goes on, roughness (i.e. mainly peaks) is reduced and valleys become submitted to material removal as well. |
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Formation of plasma electrolytic oxidation coatings on pure niobium in different electrolytes |
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Ting Wu, Carsten Blawert, Maria Serdechnova, Polina Karlova, Gleb Dovzhenko, D.C. Florian Wieland, Stevan Stojadinovic, Rastko Vasilic, Kristina Mojsilovic, Mikhail L. Zheludkevich |
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Germany, Serbia |
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https://doi.org/10.1016/j.apsusc.2021.151629
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• Plasma electrolytic oxidation process on pure niobium is voltage-controlled.
• Optical emission spectra reveal indirect influence of discharge on coating formation. • All coatings exhibit remarkable corrosion resistance and photocatalytic activity. • The present findings will be useful for bio application and environmental protection. |
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The development of PEO surface treatments for Nb (niobium) provides a possibility to produce functionalized coatings with a combination of new compositions and phases. In the frame of this work, PEO coatings on pure Nb are produced in three electrolytes containing aluminate, phosphate and silicate. Furthermore, the influence of the electrolyte composition on the PEO process and the microstructure, composition and properties of the coatings were studied. It was observed that most of the coating forming species did not participate in the plasma reactions directly, while the chemical-, electrochemical- and thermal stimulated reactions are dominating the coating formation. The results show that all the coatings are mainly composed of the Nb2O5 phase. An additional mixture of oxides (Al2O3 and AlNbO4) is found in the coating formed in aluminate-containing electrolyte, and the coating formed in phosphate-containing electrolyte contains a small amount of Nb2(PO4)3 and amorphous phosphate. No additional crystalline phase other than the amorphous silica phase is detected in the coating formed in silicate-containing electrolyte. Additionally, different morphology of the coatings is revealed and the most uniform coating is produced in silicate-containing electrolyte, which further improves its corrosion resistance. This coating also shows the highest photocatalytic activity due to the combination of Nb2O5 and silica. Since all PEO coatings on pure Nb show superior corrosion resistance and photocatalytic activity, they might be interesting for a wide range of applications ranging from transportation, biomedical implants to environmental protection. |
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Reduction of copper surface oxide using a sub-atmospheric dielectric barrier discharge plasma |
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Viktor Udachin, Lienhard Wegewitz, Sebastian Dahle, Wolfgang Maus-Friedrichs |
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Germany, Slovenia |
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https://doi.org/10.1016/j.apsusc.2021.151568
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• Deoxidation of copper by a non-thermal plasma in Ar/H2.
• Cu2O native oxide was almost fully removed after ca. 20 s. • Kinetics of oxide reduction was studied. • Deoxidation related to atomic hydrogen radicals. |
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Oxide layers on metal surfaces adversely affect processability and material properties in many industrial applications. Although several plasma-based approaches for deoxidation were investigated in the past, oftentimes they either work under conditions expensive to create or require long processing times. In this study, the deoxidation effect of a non-thermal dielectric barrier discharge plasma in an Ar/H2 gas mixture at 100 hPa and 20 °C was investigated on copper surfaces with a native oxide layer. The chemical structure of surfaces before and after deoxidation was analyzed by X-ray photoelectron spectroscopy (XPS). The results revealed that ∼98% of the surface lattice oxide Cu2O was reduced to Cu after around 20 s of plasma treatment, whereas all oxygen contaminants were almost completely removed from Cu surface after around 50 s. Additionally, the kinetics of the reduction of surface oxide was studied and a Johnson-Mehl-Avrami-Erofeev-Kholmogorov kinetic model was proposed. The analysis of the morphology of surfaces was performed with atomic force microscopy (AFM), showing minor changes in the roughness after deoxidation. Moreover, optical emission spectroscopy (OES) showed atomic hydrogen radicals in the plasma phase, which likely causes deoxidation effect. |
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Microplasma-assisted synthesis of TiO2–Au hybrid nanoparticles and their photocatalytic mechanism for degradation of methylene blue dye under ultraviolet and visible light irradiation |
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Seong Youl Lee, Hoang Tung Do, Joon Heon Kim |
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Republic of Korea, Viet Nam |
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https://doi.org/10.1016/j.apsusc.2021.151383
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• Plasmonic photocatalysts, TiO2–Au hybrid NPs, were synthesized using microplasma–liquid interaction.
• TiO2–Au hybrid NPs showed enhanced photocatalytic activity for degradation of MB under both UV and visible light. • Hole and electron induced pathways for degradation of MB at different light and pH conditions were systematically studied. • Photocatalytic MB degradation mechanism under different light was explained by the concept of remote oxidation. |
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Plasmonic photocatalysts consisting of TiO2 and Au nanoparticles (NPs) have recently been intensively studied to overcome the limited photocatalytic activity of pristine TiO2 NPs. Here, we synthesized TiO2–Au hybrid NPs using atmospheric microplasma–liquid interaction and demonstrated their enhanced photocatalytic activity, under both ultraviolet (UV) and visible light irradiation, for the degradation of the organic dyes methylene blue (MB) in water. Through mechanism studies using a hole scavenger and external source of hydroxyl radicals, it was also revealed that the contribution of hole oxidation and electron reduction pathways for degradation of MB via hydroxyl radicals by the TiO2–Au hybrid NPs differed depending on the wavelength of irradiating light. This is because the MB dye is likely remotely oxidized under UV irradiation, but not under visible light. This systematic study on the role of hole and electron pathways for photocatalytic dye degradation by TiO2–Au hybrid NPs at different light and pH conditions is helpful for understanding and developing plasmonic photocatalysts. |
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Patterned superhydrophobic surface fabrication by coupled atmospheric pressure RF and pulsed volume dielectric barrier discharges |
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Yijia Song, Qinghua Huang, Chuanlong Ma, Qi Yang, Zhan Shu, Pengfei Liu, Qiang Chen, Anton Nikiforov, Qing Xiong |
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China, Belgium |
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https://doi.org/10.1002/ppap.202100045 |
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Superhydrophobic (SH) surfaces have great potential in numerous applications. Plasma polymerization is one of the most efficient technologies for engineering SH surfaces due to its unique feature of tailoring surface chemistry and surface topography simultaneously. Herein, a novel sandwich-like plasma device that consists of contiguous two-stage dielectric barrier discharges (DBDs) driven by the time-modulated radiofrequency (RF) and pulsed power sources is proposed to polymerize hexamethyldisilazane (HMDSN) at atmospheric pressure for the purpose of SH surface engineering. The coordination of dual power sources shows effective performances in plasma operation and material surface treatment, compared to the case driven by any power source alone. Easy ignition and enhanced stability are achievable for the upper RF DBD with the assistance of the bottom pulsed DBD. Vice versa, a diffuser pulsed discharge is obtainable with the input of abundant active and energetic species and precursor fragments from the upper RF plasma. Diagnostic measurements by optical emission spectroscopy and Mie scattering demonstrate that HMDSN fragmentation and nanoparticle nucleation are initiated predominantly by the RF-driven plasma. These species and nanoparticles are further fragmented and dispersed in the bottom pulsed discharge. Consequently, the desired SH surface is fabricated with a similar pattern to that of the pulsed DBD geometry. This study provides a new pathway based on the plasma-assisted method to control surface hydrophobicity and provides insights on a new plasma deposition method suitable for atmospheric pressure material processing. |
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Application of plasma-activated water as an antimicrobial washing agent of fresh leafy produce |
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Panagiotis Dimitrakellis, Marianna Giannoglou, Zacharoula Maria Xanthou, Evangelos Gogolides, Petros Taoukis, George Katsaros |
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Greece |
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https://doi.org/10.1002/ppap.202100030 |
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Plasma-activated water (PAW) was investigated as a “green” antimicrobial washing agent for decontamination of ready-to-eat rocket salads. PAW was generated using a dielectric barrier discharge jet and the plasma chemistry was correlated to the PAW characteristics. The low helium flow rates favored the NOx formation and resulted also in higher reactive species concentration upon storage. PAW activity was retained even after 12 days of storage at low temperatures. The application of fresh and 7-days-stored PAW as washing agents resulted in significant microbial load reduction, whereas the quality indices of PAW-treated rocket leaves were retained. Finally, the PAW treatment increased the shelf-life of the leafy salad by a factor of ~2.5 upon storage at 5°C, demonstrating the potential application of plasma technology in the processing and shelf-life extension of sensitive food products. |
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High-performance rollable polymer/metal/polymer thin-film heater and heat mirror |
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Sung Hyun Kim, Eunmi Cho, Mac Kim, Sang-Jin Lee |
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Republic of Korea |
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https://doi.org/10.1002/ppap.202100098 |
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In this study, we propose high-performance polymer/metal/polymer (HP–PMP) films with simultaneous heat reflection/transparent heater functions. The thickness-optimized HP–PMP films showed a maximum transmittance of 77.12% (86.65% without the base film) at a wavelength of 460 nm, sheet resistance of 5.982 Ω/□, and figure of merit of 12.44 × 10−3 Ω−1 (39.89 × 10−3 Ω−1 without the base film). In the surface heating test, the temperature reached approximately 150°C at an applied voltage of 11 V. In the heat mirror experiment using an infrared lamp, the HP–PMP film showed 85.1% heat shielding, compared to the base film. After the mechanical rolling reliability test, the HP–PMP film did not show any change in resistance after 10 ,000 cycles under a rolling condition of 240°. |
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Inhibition of biofilm formation on polystyrene substrates by atmospheric pressure plasma polymerization of siloxane-based coatings |
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Rodolfo Múgica-Vidal, Elisa Sainz-García, Ignacio Muro-Fraguas, Ana Sainz-García, Ana González-Marcos, María López, Beatriz Rojo-Bezares, Paula Toledano, Yolanda Sáenz, Fernando Alba-Elías |
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Spain |
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https://doi.org/10.1002/ppap.202100097 |
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Biofilms pose important economic and health risks in biomedical applications and in food industries. In this study, coatings that reduce the biofilm formation of Pseudomonas aeruginosa on polystyrene cell culture plates are deposited by plasma polymerization of (3-aminopropyl)triethoxysilane using an atmospheric pressure plasma jet system at three different power levels. Surface characterizations and quantification of biofilm formation during 1 week after deposition suggest that the higher concentration of oxygenated carbon groups on the coated samples than on uncoated ones can induce higher levels of oxidative stress in the bacteria in contact with the coatings. This causes an initial overproduction of extracellular polymeric substances that can avoid further bacterial attachment and biofilm formation at later cycles of biofilm development. |
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Machine Learning with Explainable Artificial Intelligence Vision for Characterization of Solution Conductivity Using Optical Emission Spectroscopy of Plasma in Aqueous Solution |
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Ching-Yu Wang, Tsung-Shun Ko, Cheng-Che Hsu |
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Taiwan |
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https://doi.org/10.1002/ppap.202100096 |
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This study presents an explainable artificial intelligence (XAI) vision for optical emission spectroscopy (OES) of plasma in aqueous solution. We aim to characterize the plasma and OES with XAI. Trained with 18000 spectra, a multilayer artificial neural network (ANN) model accurately predicted the solution conductivity. Local interpretable model‐agnostics explanations (LIME), an XAI method, interpreted the model through perturbing spectral features and fitting the feature contribution with a linear model. LIME showed that OH, Hγ, and Hβ emission lines were critical to the model, differing from the lines typically selected by humans. The results demonstrated that machine captured the spectral features neglected by humans. We believe using XAI for plasma OES analysis impacts the fields of plasma and analytical chemistry. |
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Determination of electron properties of a helium atmospheric pressure plasma jet with a grounded metallic target |
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Tuyen Ngoc Tran, Cha-Hwan Oh, Wonwook Lee |
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South Korea |
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https://doi.org/10.1002/ppap.202100092 |
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An atmospheric pressure plasma jet (APPJ) was configured to generate helium atmospheric pressure plasma. A kilohertz AC voltage was applied to APPJ electrodes, and a grounded aluminum target was placed outside of a quartz tube on the plasma propagation axis. The electron temperature and density of APPJ were determined using the emissivity of continuum radiation in 380–500 nm spectra. Electron temperatures and densities for the helium plasmas with and without a target were compared. When the target was installed, the continuum radiation was enhanced, and electron density increased. Spatial distributions of electron temperature and density from the nozzle of the quartz tube to the target were examined. The electron temperature increased up to ∼2.75 eV, and electron density increased and decreased along APPJ propagation. |
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Deposition of charged aerosols by E × B enhanced low-temperature plasma jet array |
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Baihan Chen, Zhongzheng Huang, Dawei Liu |
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China |
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https://doi.org/10.1002/ppap.202100085 |
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In this paper, an efficient plasma jet array based on the E × B enhancement was developed. The direction of the magnetic field was the same as the propagation direction of the plasma jet, and the direction of the electric field was perpendicular to the plasma jet. The E × B enhancement increased the length of the plasma jet from 0.5 to 1.8 cm, the discharge current peak by 37.8%, and the plasma power by 11.1%, compared with the control case. Three-dimensional simulation of electrons movement indicates that the confinement of electrons in the high argon concentration region was the main reason for the E × B enhancement. The stronger discharge based on the E × B enhancement increased the ion density in the open air significantly. The charged aerosols were generated through the diffusion charging mechanism. The image charge electric force between charged and neutral aerosols increased the collision rate between aerosols, therefore, the larger aerosols were generated, and 108% more deposition of aerosols than the natural settlement case were achieved. |
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Numerical study on interactions of atmospheric plasmas and vegetable oils by reactive molecular dynamic simulations |
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Shu-Qi Tian, Xiao-Long Wang, Yuan-Tao Zhang |
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China |
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https://doi.org/10.1002/ppap.202100124 |
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Plasma medicine is a rapidly growing multidisciplinary field. Recently, experimental observations have shown that plasma-activated oil (PAO) with high reactive activity can effectively promote wound healing. In this study, a reactive molecular dynamic (MD) simulation is performed to investigate the interactions of reactive oxygen species (ROS), such as O, OH, and O3 produced in atmospheric plasmas, and fatty acids in vegetable oils with the ReaxFF field. The reaction processes of the chemical bond breaking and formation of fatty acids upon impact by the ROS are deeply explored. The simulation shows that the reactions typically start with the H abstraction from fatty acids, then often resulting in the formation of double C═C bonds or conjugated double bonds. The insertion of functional groups, such as aldehyde and alcohol groups, and the detachment of the carboxyl group are also observed from the simulation. Based on the computational data the final products in PAO upon impact of ROS are given. Moreover, the dose effects of ROS on the oxidation processes are explored by changing the number of ROS in the simulation box. Usually, by increasing the number of ROS in the simulation, more reactive groups are generated in PAO, which are consistent with the experimental observation. This study unveils the formation and breaking of chemical bonds and the production of new reactive groups, which enables us to deeply understand the mechanisms of plasma pharmacy and plasma medicine. |
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Sealing of porous titanium oxides produced by plasma electrolytic oxidation |
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Luca Casanova, Nicola Belotti, MariaPia Pedeferri, Marco Ormellese |
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Italy |
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https://doi.org/10.1002/maco.202112612 |
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Plasma electrolytic oxidation is a powerful technique allowing the formation of ceramic coatings with a high degree of functionalization. Plasma–chemical interactions, resulting from the application of a high voltage in a conductive electrolyte, like 0.5 M NaOH, favor the development of a porous surface, which deserves to be sealed to obtain proper corrosion resistance. In the present work, the effect of temperature employed during sealing in calcium acetate is investigated, finding 85°C as an optimum temperature to allow pores closure. Furthermore, a comparison with sealing performed in hot water is presented, which demonstrated similar sealing efficiency. Scanning electron microscope and electrochemical impedance spectroscopy are the tools selected to investigate sealing effects. Impedance spectra are fitted according to feasible electrochemical equivalent circuits finding two-time constants when applied to sealed samples indicative of the presence of barrier and porous layer, respectively. |
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Effect of treatment time on a PEO-coated AZ31 magnesium alloy |
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Yu Zhang, Yao Chen, Xiangyu Duan, Yanwei Zhao |
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China |
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https://doi.org/10.1002/maco.202112552 |
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Plasma electrolytic oxidation (PEO) coatings were formed in a phosphate–silicate-based electrolyte containing K2ZrF6 on an AZ31 Mg alloy. The physical and chemical properties of the coatings were investigated using scanning electron microscopy, atomic force microscopy, X-ray diffraction (XRD), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The results showed that the thickness of the PEO coatings increased linearly with increased treatment times. Additionally, the micropores on the coating surfaces increased in size, but decreased in porosity with increased PEO treatment time. The XRD results showed that the coatings were mainly composed of MgO, MgF2, MgSiO3, and ZrO2, and the electrochemical tests revealed that the corrosion resistance of the coatings increased with increased treatment time. Besides, the EIS results correlated well with the potentiodynamic polarization test results. |
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Flame pyrolysis – a cost-effective approach for depositing thin functional coatings at atmospheric pressure |
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I. Zunke, B.S.M. Kretzschmar, A. Heft, J. Schmidt, A. Schimanski, B. Grünler |
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Germany |
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https://doi.org/10.1016/B978-0-444-63240-1.00006-1 |
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Most optical, electrical, mechanical, or biological active thin films are deposited using the well-known and established vacuum-based physical vapor deposition and chemical vapor deposition methods. The deposition of thin functional layers under atmospheric pressure conditions is an attractive alternative for especially large-area coatings. In recent years many different methods have been established for various applications. Particularly the flame-based techniques offer a cost-effective solution. The basic principles of the flame-based deposition techniques are reviewed and the technical realization is shown by means of selected examples of the current research and developments. The formation of silicone oxide layers with a wide range of properties is investigated in detail. Applications such as adhesion promotion, optical effective, and barrier layers are reviewed. The deposition of transparent conductive zinc oxide is investigated. Further thin films like photocatalytic active TiO2, electrochromic WOx, and elemental silver are also introduced. |
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Cold Atmospheric Plasma Treatment: A Novel Method of Diabetes Mellitus Therapy: A Basic Study |
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Alireza Rezaeinezhad, Marjan Mahdavi-Gharavi, Mohammad Talebi-Khoshmehr, Hossein Mirmiranpour, Hamid Ghomi |
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Iran |
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DOI: 10.1615/PlasmaMed.2021040177
Plasma Medicine, 11(3):19 – 30 (2021) |
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We investigate the effect of cold atmospheric plasma (CAP) therapy on diabetes in the streptozotocin (STZ)‐induced diabetic rat model. In all, 30 male Wistar rats were distributed into three experimental groups: healthy, diabetic, and diabetic receiving plasma treatment. The two diabetic groups were injected with STZ to induce diabetes. Plasma treatment was performed by exposure of rats to argon plasma jet for 600 s twice a week, for 4 weeks. The results showed that the cold plasma course of therapy greatly downregulated the oxidative stress and secretion of inflammatory cytokines. Moreover, the results revealed that the glucose level of the diabetic rats decreased significantly after treatments in comparison to the diabetic control groups. Also, a decrease in advanced glycation end-product (AGE) content was achieved after therapy. The results of the study showed that cold plasma has a therapeutic effect on diabetic rats and can be considered as a noninvasive method for therapy of diabetes. |
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Effects of Nonthermal Atmospheric Pressure Plasma Jet on Human Dental Pulp Stem Cells |
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Seyedeh Fatemeh Peyro Mousavi, Alireza Ganjovi, Ali Eskandarizadeh, Masoud Parirokh, Ali Derakhshani, Ali Reza Saidi, Amir Falahat |
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Iran |
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DOI: 10.1615/PlasmaMed.2021040860
Plasma Medicine, 11(3):41 –58 (2021) |
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The effects of a nonthermal atmospheric plasma jet with argon and argon/oxygen (Ar/O2) gases on live human dental pulp stem cells (hDPSCs) were studied to verify tooth vitality in the pulp-capping process. Using MTT assay, the surviving hDPSCs after plasma jet exposure for 1, 2, and 3 min were counted. First, for the pulsed plasma jet the frequency varied from 10 to 50 kHz for 5 groups with Ar and 5 groups with Ar/O2 plasma jet. Later, with the alternating current (AC) plasma jet, the voltage was changed between 5.5 and 16.05 kV for 13 groups. The cells in the control group were only exposed to Ar and Ar/O2 gases. To control thermal damage to hDPSCs, optical emission spectroscopy was used. For data analysis, the ANOVA repeated measure was used. There were significant differences between the various frequencies and exposure durations (p < 0.05) for the Ar plasma. For the Ar/O2 gas, there were significant differences between frequencies (p < 0.001). For the AC plasma jet with Ar gas, there were significant differences between voltages (p < 0.001). At the higher pulsed jet frequencies, temperatures increased. Eventually, the suitable durations for root canal disinfection and hDPSC survival with the Ar pulsed jet were 2 and 3 min at 10 and 30 kHz, respectively. Since cold plasma disinfection keeps hDPSCs alive, it can be helpful in promoting tooth survival and durability for pulp capping in clinical treatments. |
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Cytotoxicity of Nonthermal Plasma Treatments on Three Cancer Cell Lines Induces Changes in Cell Morphology and in HSP70 Gene Expression |
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Roberto Gristina, Daniela Pignatelli, Giuseppe Camporeale, Giorgio Dilecce, Valeria Veronico, Pietro Favia, Eloisa Sardella |
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Italy, Germany |
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DOI: 10.1615/PlasmaMed.2021041643
Plasma Medicine, 11(3):59 –81 (2021) |
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Nonthermal plasma processes recently emerged as promising therapeutic tools for the treatment of cancer. Most anticancer effects of plasma have been related to the induction of oxidative stress due to the release of reactive oxygen and nitrogen species (RONS), among other plasma components, during discharge. The exact mechanism of action in the eradication of cancer, though, is still far from being fully understood. In this research, three cancer-derived cell lines were exposed to pulsed dielectric barrier discharge (DBD) to investigate the effect of direct plasma exposure on cancer cells. Among many cellular functions, cell adhesion and morphology were found to be visibly influenced. Morphological assays showed the inhibition of intercellular adhesion, losses in cell clustering, and changes in the external shape and actin cytoskeleton. These effects were related to the decrease in cell viability and plasma operational conditions. The increased expression of the heat shock protein HSP70 in plasma-exposed Saos2 cells confirmed that changes in morphology and viability in cancer cells are representative of internal changes in the oxidative state of cells that are caused by plasma-induced oxidative stress. |
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Improving surface wettability and adhesion property of polytetrafluoroethylene by atmospheric-pressure ammonia water-mixed plasma treatment |
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Yuheng Li, Yuyang Zhou, Yukai Gu, Boxi Chen, Bingqi Wang, Jingcan Yan, Jiyu Liu, Faze Chen, Danyang Zhao, Xin Liu |
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China |
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https://doi.org/10.1016/j.vacuum.2021.110763 |
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• Ammonia water is added into working gas of plasma jets to better modify PTFE.
• The ammonia-mixed plasma jets show much better hydrophilization effect than others. • Water contact angle decreases from ∼101° to ∼19° after 120s plasma treatment. • Peel strength with epoxy glue is improved by 431% after the treatment. |
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Polytetrafluoroethylene (PTFE) has excellent properties and has been widely used in various fields. However, the PTFE surfaces have relatively poor wettability and adhesive property, which restrains their widespread applications. Although atmospheric-pressure plasma jets have been employed to treat the PTFE surfaces, hydrophilization effect and processing efficiency still need to be further improved. In this paper, we propose to add ammonia water into the working gas of the atmospheric-pressure plasma jets to better modify the PTFE surfaces. The influences of ammonia water contents on surface wettability and adhesive property of the PTFE surfaces were investigated by water contact angle (WCA) measurement and peel strength experiments, respectively. When the ammonia water-mixed ratio was 1%, a WCA of ∼19° was obtained after 120 s plasma treatment, which was much lower than that treated by pure helium plasma jet (∼29°) and untreated surface (∼101°). In addition, the adhesive property was also well improved by the ammonia water-mixed plasma jets: peel strength of the sample treated by the ammonia water-mixed plasma jet was respectively 119 N/m and 446 N/m larger than that of the sample treated by pure helium plasma jet and the untreated sample. |
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Antithetic superhydrophobic/superhydrophilic surfaces formation by simple gas switching in an atmospheric-pressure cold plasma treatment |
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Donghyun Kim, Jonggu Han, Rodolphe Mauchauffé, Jongwoon Kim, Se Youn Moon |
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Republic of Korea |
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https://doi.org/10.1016/j.matchemphys.2021.125482 |
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• A facile method for surface wettability control using an atmospheric-pressure plasma.
• Elucidation of surface chemistry and morphology modified by the plasma. • Correlation between plasma chemistry and surface wettability. • Modulation of water contact angle by simply plasma gas chemistry fine tuning. |
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The wettability control of surfaces is a significant issue in many industrial fields such as encapsulation, water repellency enhancement, oil recovery, etc. From a practical point of view, to reach the intended surface wettability, it is important for a surface modification process to be low-cost, easily implemented and fast. Therefore, in this work, a facile plasma deposition method is suggested to form surfaces with antithetic wettabilities, i.e. superhydrophobic and superhydrophilic, via simple introduction of additive gases in an atmospheric-pressure plasma generated with argon and hexamethyldisilazane (HMDS). The hydrophobic surface (WCA: 115°) modified by Ar/HMDS plasma is easily switched to superhydrophobic surface (WCA: 160°) by N2 addition and to superhydrophilic surface (WCA: 10°) by O2 addition. From physical and chemical analyses of plasma treated surfaces, a small amount of N2 or O2 gas is shown to dramatically change the surface morphology and chemical composition. Besides, by finely tuning the additive gases flow rates, the surface wettability could be continuously modulated in the whole ∼0° to 160° water contact angle range. |
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Hydrophobic Waxes in Ivory Nuts Affect Surface Modification by Atmospheric Air Plasma Jet |
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Yuri Ferreira da Silva, Renata Nunes Oliveira, Renata Antoun Simao |
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Brazil |
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https://doi.org/10.33263/BRIAC114.1222712237 |
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Ivory nuts, bioproducts from South American palms, possess a hard, water-insoluble, and microporous endosperm with a strong resemblance to elephant ivory. The nuts sustainable appeal made them popular as eco-friendly substitutes to ivory and, more recently, microbeads. However, their hygroscopicity and mannan composition impart susceptibility to deterioration by microbes and insects. Cold plasma treatment has been widely investigated as a clean and cost-effective procedure for seed disinfection and surface modification. Hence, in this work, ivory nut endosperm was treated by an air plasma jet to modify wettability. Plasma treated samples were characterized by the water contact angle, AFM, and Raman imaging. Water contact angle results presented an increase from (31.5 ± 8.7)º to (78.9 ± 5.4)º, demonstrating surface hydrophobization. This result was attributed to the modification of surface chemistry by migration and repolymerization of extractives promoted by plasma treatment. AFM results evidenced the formation of a heterogeneous layer containing lamellar features similar to plant epicuticular waxes. Besides, principal component analysis of Raman imaging results highlighted
spectral contributions from wax, xylan, mannan, and lignin. These results demonstrate that atmospheric air plasma jets can be employed for ivory nut hydrophobization with no need for additional precursors, altering surface chemistry by crosslinking endosperm native substances. |
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Surface modification of polytetrafluoroethylene film by argon cold atmospheric pressure plasmas for enhancing bonding with graphene-filled polyimide adhesives |
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Yung-Sen Lin, Hsiang-Yu Wan, Bing-Rong Wu |
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Taiwan |
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https://doi.org/10.1002/pen.25878 |
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Significantly enhanced adhesion of polytetrafluoroethylene (PTFE) films to graphene-filled polyimide (PI) adhesives by argon (Ar) cold atmospheric pressure plasmas (CAPPs) at the exposure durations of 72–96 s was undertaken. Poor adhesion of PTFE film to PI adhesive with no bonding (100% delamination) was highly improved to good bonding (100% attachment) for PTFE film treated by Ar CAPPs. Hydrophobic PTFE surface (water contact angle up to 91.1°) was changed to hydrophilic PTFE surfaces (water contact angle up to 37.4°–66.0°) with Ar CAPPs treatment by formation of polar chemical bonds such as C–O and C=O. To realize how the chemical bonds of C–O and C=O were produced onto the PTFE surface by Ar CAPPs, the plasma active species of Ar CAPPs were detected by optical emission spectroscopy. |
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A systematic study on Na2SO4-induced hot corrosion behavior of plasma-sprayed La2(Zr0.75Ce0.25)2O7 coating |
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Pan Yang, Zhenyu Bu, Yulong An, Huidi Zhou, Yuhong Li, Jianmin Chen |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127979
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To better understand the hot corrosion behavior of LCZ ceramic coatings against Na2SO4 molten salts, three series of hot corrosion tests were performed from the perspectives of Na2SO4 content, corrosion duration and corrosion temperature. Different corrosion products of La2O2SO4, La2O2S and Ce7O12 were identified depending on the hot corrosion conditions and the probable reaction mechanisms were proposed. The effects of Na2SO4 content, corrosion duration and corrosion temperature on hot corrosion behavior were investigated systematically. Results show that Na2SO4 molten salt is hard to react chemically with LCZ coating. The chemical reaction between LCZ coating and Na2SO4 molten salt needs a long time. When the content of Na2SO4 salts is high, the corrosion reaction could be accelerated. The phase transition and decomposition of corrosion products are responsible for the different hot corrosion behaviors at 1050–1500 °C. Moreover, a model describing the hot corrosion process induced by Na2SO4 molten salt is built, which includes two stages of eroding LCZ coating. |
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Plasma electrolytic oxidation of magnesium by sawtooth pulse current |
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Yue Guo, Aleksey Rogov, Alexander Hird, Beatriz Mingo, Allan Matthews, Aleksey Yerokhin |
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UK, Russia |
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https://doi.org/10.1016/j.surfcoat.2021.127938
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Mg2SiO4 coatings were formed on cp-Mg by Plasma Electrolytic Oxidation (PEO) using electrical regimes based on sawtooth anodic current pulses with extended ascending or descending segments (ramps). Voltage, current and light emission signals were simultaneously acquired to derive and analyse the evolution of system current and discharge population density during PEO process, while optical emission spectroscopy was employed for identification of plasma species. Coating morphological characterisation was carried out using Scanning Electron Microscopy. Phase composition was identified by X-ray diffraction. The corrosion performance was evaluated with Electrochemical Impedance Spectroscopy at various periods of exposure to corrosive media (0.5 wt% NaCl). It was shown that the application of sawtooth pulses allowed the controlling of microdischarge characteristics and coating morphology in both pulsed unipolar and reversed current regimes. Results further demonstrate that the application of anodic sawtooth pulses with the negative ramp facilitated defect healing during coating formation leading to production of more uniform PEO coatings with lower porosity and a slower degradation rate of magnesium substrate. A steady decay in the coating resistance with immersion time provides a possibility for controlling magnesium degradation and thereby for optimisation of component lifetime in applications where predictable Mg dissolution rate is required, such as sacrificial anodic protection of metallic structures and resorbable biomedical implants. |
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Analyses of electrochemical behavior of plasma electrolytic oxidation film on Zirlo alloy in lithium borate buffer solution at 25–300 °C |
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Kejian Wei, Xingping Wang, Chi Xu, Jiancheng Du, Wenbin Xue, Gang Cheng |
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China |
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https://doi.org/10.1016/j.surfcoat.2021.127935
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The electrochemical behavior of plasma electrolytic oxidation (PEO) film on Zirlo alloy in 25–300 °C lithium borate buffer solution was evaluated by in-situ electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. As the solution temperature rose to a critical value (150 °C), a new relaxation process related to the distinguishable maximum in phase angle vs. frequency curves was observed at medium frequency and became more pronounced with increasing temperature. This relaxation process almost disappeared after a short exposure time under 300 °C. The transition of the relaxation process was closely related to the impedance of PEO film. The new relaxation process was ascribed to the diffusion of corrosion product through the PEO film. In addition, the degradation of the protective properties of PEO film was observed with increasing temperature, which resulted from the enhanced ionic conductivity of doped zirconia under high temperature. Finally, the PEO film hardly changed in morphology and microstructure after in-situ EIS tests at 25–300 °C. |
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Corrosion inhibition of Ti6Al4V alloy by a protective plasma electrolytic oxidation coating modified with boron carbide nanoparticles |
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Parisa Molaeipour, Saeed Reza Allahkaram, Sajjad Akbarzadeh |
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Iran |
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https://doi.org/10.1016/j.surfcoat.2021.127987
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Plasma electrolytic oxidation (PEO) is a cost-effective and versatile technique to achieve protective oxide coatings in light metals. Composite coatings containing B4C nanoparticles were produced by the PEO technique on a Ti6Al4V alloy. The influence of nanoparticles on the microstructure and corrosion resistance of the prepared ceramic composite coatings, as well as its incorporation mechanism into the PEO layer, were investigated. B4C nanoparticles were added to aluminate-based electrolytes and a pulse power supply was used as a constant voltage regime to obtain PEO composite coatings. Improvement in corrosion protection was also assessed by electrochemical impedance spectroscopy (EIS) and polarization tests, illustrating that a reduction in the corrosion resistance ratio was 8 for the composite coating compared to 16 for the sample without nanoparticles, after three weeks of immersion. The effect of nanoparticles on the phase composition was examined by X-ray diffraction (XRD) tests. Moreover, scanning electron microscopy (SEM) images illustrated the capability of B4C nanoparticles in filling the inherent pores of PEO coatings. |
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Thermal decomposition and crystallization behavior of Yb/Y co-doped SrZrO3 precursor used in the suspension plasma spray process |
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Yuanming Gao, Yu Bai, Peng Zhang, Weicheng Liang, Qi Liu, Shufang Yan, Jiao Huang, Hongying Dong, Ruigang Wang, Wen Ma |
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China, USA |
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https://doi.org/10.1016/j.surfcoat.2021.127991
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A double rare-earth (Yb/Y) co-doped SrZrO3 [Sr1.0(Zr0.9Yb0.05Y0.05)O2.95] thermal barrier coating was prepared via suspension plasma spraying (SPS). The rare-earth nitrates [Zr(NO3)4·5H2O, Sr(NO3)2, Yb(NO3)3·6H2O, Y(NO3)3·6H2O] and NH4(C2O4)2·H2O were used to prepare the precursor suspension by co-precipitation. The thermal decomposition and crystallization of the precursor suspension powders calcined at 1200 °C were characterized with X-ray diffraction and a synchronous thermal analyzer coupled with quadrupole mass spectrometry. Zr2(C2O4)2(OH)4 decomposed into Zr(C2O4)2, ZrO2, and H2O initially, followed by the decomposition of Zr(CO3)2 into ZrO2. The SrC2O4 precursor decomposed into SrCO3and SrO consecutively. The ZrO2 reacted with SrO (Yb2O3, Y2O3) to generate the Yb/Y co-doped SrZrO3. And the Yb/Y co-doped SrZrO3 coating with a columnar crystal structure was prepared by SPS, which was analyzed with scanning electron microscopy, an inductively coupled plasma atomic emission spectrometer, and a laser flash analyzer. The thermal conductivity of the as-prepared coating was 1.77 W·m−1·K−1 at 1000 °C, which was more than 19% lower than that of the SPS SrZrO3 coating. |
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Effect of OH species in the oxynitride titanium formation during plasma-assisted thermochemical treatment |
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J. de O. Vitoriano, R.S. Pessoa, A. de A. Mendes Filho, J. de Amorim Filho, C. Alves-Junior |
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Brazil |
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https://doi.org/10.1016/j.surfcoat.2021.127990
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Currently, the study of oxynitrides surfaces emerges as one of the most promising ways to obtain improvements in several properties of titanium and expand its applications. In this context, the plasma-assisted thermochemical technique has stood out due to its versatility and easy to control precisely the structure and composition of the compound layer. In this work, titanium samples were subjected to 40%H2–60%N2 and 40%H2–45%N2–15%O2 plasma treatment for surface modification where the effect of OH species in the oxynitride formation was investigated. Grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy and X-ray induced photoelectron spectroscopy (XPS) were used for structural and chemical composition analyses. Also, optical emission spectroscopy (OES) was used in order to study the plasma chemistry. Results evidenced that the addition of H2, which consequently increases the concentration of OH species in the plasma, during the pre-treatment and treatment was important for the cleaning and reduction of native titanium oxides. XPS results showed that the titanium surface, which had 92% TiO bond before treatment, was totally reduced, giving rise to Ti-N-O (56%) and TiN (44%) bonds when nitrided. When oxygen was added to the atmosphere, the TiN bond disappeared, giving rise to the TiO bond (27%) and Ti-N-O bond (73%). The treatments were suitable for oxynitriding the titanium surface in a predominantly diffusive process with about 290 nm thickness. Material analysis allow us to describe the main mechanisms for oxynitride formation as well as correlate this phenomenology with some investigated plasma properties by OES analysis. |
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Photoelectrochemical properties of plasma-induced nanostructured tungsten oxide |
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Shuangyuan Feng, Shin Kajita, Masanobu Higashi, Anja Bieberle-Hütter, Tomoko Yoshida, Noriyasu Ohnoa |
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Japan, The Netherlands |
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https://doi.org/10.1016/j.apsusc.2021.151979
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• Nanostructured WO3 synthesized by helium plasma irradiation and calcination.
• The 15min-WO3-773K photoelectrode exhibited the highest photocurrent density. • The reasons for the excellent photoelectrochemical performance have been proved. • It can be ascribed to the proper oxide layer thickness and exposed crystal facets. |
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Helium (He)-induced nanostructured tungsten sheets were synthesized by He plasma irradiation under different plasma exposure durations. After calcination, nanostructured tungsten oxide samples were used as photoelectrodes to test photoelectrochemical (PEC) performance. The results showed that nanostructured WO3photoanodes have higher PEC performance compared to the sample without nanostructures. The 15 min irradiated sample had the highest photocurrent density of 3.5 mA/cm2 under the thermodynamic potential of water oxidation (1.23 V vs. RHE). It was found that the oxide layer thickness and exposed crystal facet have a significant impact on PEC performance. The plasma synthesis technique has proved to be an effective method for preparing nanostructured WO3photoelectrodes. |
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Facile preparation of hazy Ga-doped ZnO electrodes by atmospheric pressure plasma jet |
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Ping-Chia Hsu, Jia-Yang Juang |
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Taiwan |
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https://doi.org/10.1016/j.apsusc.2021.152232
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• A simple yet effective way to introduce textured films in a single-step process.
• Deposited hazy GZO electrodes under ambient conditions for solar cells. • Achieved high haze (25%) while retaining high transmittance and low resistivity. • New functionality that conventional techniques such as sputtering cannot achieve. |
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Increasing the optical path length without degrading optoelectronic properties of front electrodes of solar cells is promising to enhance the power conversion efficiency. This can be achieved by increasing the haze (H) of the electrode through texturing, while retaining high transmittance (Tt) and low sheet resistance (Rs). However, it is challenging to balance these properties simultaneously since they are mutually influenced. Here, we present a facile, low-cost, and single-run method of preparing gallium-doped zinc oxide (GZO) with high H (>25%), high Tt (>90% in the visible range, referenced to glass), and low Rs (6.62 Ω sq−1) using atmospheric pressure plasma jet. First, we increase the nozzle-substrate distance, or working distance (WD), to deposit a thin, rough GZO as a haze enhance (HE) layer and immediately deposit a standard GZO layer using the same apparatus. By tailoring the roughness of the HE layer using WD and scanning pitch, we successfully produce high-quality hazy GZO that have competitive figures of merit of 6.3 × 10−2 Ω−1 (referenced to the glass) and 2.1 × 10−2 Ω−1 (overall), and H = 25%. Also, unlike conventional methods, our approach does not require vacuum, etching, additional materials, or change of machine/tooling, which can significantly reduce the operational complexity. |
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Doping and defects: The coloring mechanism of black plasma electrolytic oxidation (PEO) films on aluminum alloys |
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Jinlong Pan, Yanwei Wen, Lili Wang, Zhiyong Wu, Hui Dong, Zuoyan Ye |
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PR China |
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https://doi.org/10.1016/j.surfcoat.2021.128035
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Plasma electrolytic oxidation (PEO) can be used to fabricate black ceramic films on aluminum alloy by adding transition-metal anions into the electrolyte. Although the coloration was attributed to transition-metal oxides, a thorough explanation of the relationship between oxides and black color was required. In this study, black PEO films were created by incorporating ammonium metavanadate or sodium tungstate into the electrolyte. The research focused on alumina band-gap modification to explain the mechanism of black coloring. The absorption spectrum and X-ray photoelectron spectroscopy (XPS) valence band characterization revealed that the bandgap of alumina after doping was significantly narrowed. The density of state of alumina, including before doping, after doping, and introducing point defect was simulated by first-principles density functional theory calculation. It was discovered that doping transition metals into alumina decrease the conduction band while defects in alumina cause an upper shift of the valence band. The narrowing of the bandgap resulted in the absorption of all visible light and the appearance of black. |
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Microstructure and performance of YTaO4 coating deposited by atmospheric plasma spraying on TC4 titanium alloy surface |
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Jing Feng, Jun Wang, Kailong Yang, Ju Rong |
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PR China |
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https://doi.org/10.1016/j.surfcoat.2021.128004
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In view of the good thermal insulation, good high-temperature phase stability, high thermal expansion coefficients and ferroelastic transformation of YTaO4 ceramics, which can be prepared as thermal insulation and anti-oxidation coating material on Ti6Al4V alloy (TC4). Herein, a bond coating (BC, NiCrAlY) and top coating (TC, YTaO4) were deposited on a TC4 surface via atmospheric plasma spraying (APS), the microstructure, multi-scale mechanical properties and failure mode of TC were investigated. XRD results demonstrate YTaO4 coating has good phase stability below 900 °C, both average particle size and intrinsic strain are calculated by Williamson-Hall (WH) method. The surface hardness, wear resistance and service life of YTaO4 coating deposited on TC4 is higher than that of pure TC4, and thermal shock tests results (>300 times at 900 °C; 269 times at 1000 °C; 79 times at 1100 °C) exhibits YTaO4 coating has an excellent protective effect against thermal shock and oxidation for TC4. |
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Interactions between successive high-velocity impact droplets during plasma spraying |
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Yongang Zhang, Steve Matthews, Dongting Wu, Yong Zou |
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PR China, New Zealand |
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https://doi.org/10.1016/j.surfcoat.2021.128006
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During plasma spraying, interactions between successive impacting particles/droplets are critical to the interfacial bonding properties between splats and the microstructural development of the bulk coating. The transient spreading process of two successive plasma- sprayed Ni20Cr droplets with different impacting spacing was numerically studied while the interfacial features between these two solidified splats were experimentally characterized by focused ion beam (FIB) microscope and transmission electron microscope (TEM). Droplets directly impacting onto the center of a previously deposited splat solidified quickly, inducing splashed fingers and smaller solidified grains. A higher droplet impact temperature could remelt the bottom splat and promote metallurgical bonding along the splat-splat interface more readily. For droplets impacting away from the previously solidified splat, the second molten droplet could either climb over the periphery of the previous splat inducing significant finger splashing, or spread beneath the curling-up splat modifying the solidification process. The solidification behavior of the subsequent droplet at the splat-splat interaction region played an important role in influencing the formation of inter-splat pores and grain growth. |
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Hot corrosion behavior of dense CYSZ/YSZ bilayer coatings deposited by atmospheric plasma spray in Na2SO4 + V2O5 molten salts |
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Jhonattan de la Roche, Juan Manuel Alvarado-Orozco, Pablo Andrés Gómez, Irene García Cano, Sergi Dosta, Alejandro Toro |
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Colombia, Mexico, Spain |
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https://doi.org/10.1016/j.surfcoat.2021.128066
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In this work, the hot corrosion (HC) resistance of bilayer thermal barrier coatings (TBC) architectures composed of dense Ceria-Yttria Stabilized Zirconia (CYSZ) and Yttria-Stabilized Zirconia (YSZ) deposited using the Atmospheric Plasma Spray (APS) technique was evaluated. Two kinds of HC tests were performed using different salt concentrations and thermal cycling (adding fresh salt between cycles) with a constant salt mixture (Na2SO4-V2O5) and constant testing temperature (900 °C). The results showed that the HC mechanism changes with the testing procedure, and the outer dense CYSZ layer acts as a barrier to protect the inner layers against HC degradation. However, the formation of vertical cracks during the coating deposition process affected the corrosion resistance of the TBC systems. |
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Green chemical production of biocompatible conductive poly(3,4-ethylenedioxythiophene) by nonthermal plasma-activated water |
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Tungpo Chen, Yu-Ting Tseng, Chieh-Hao Wan, Yesong Gu |
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Taiwan, ROC |
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https://doi.org/10.1002/ppap.202100117 |
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To synthesize a conductive polymer poly(3,4-ethylenedioxythiophene) using a more environmentally friendly approach, we have previously used a nonthermal plasma (NTP) to activate H2O2 for the initiation of water-soluble PEDOT:PSS synthesis, which has been confirmed to be degradable. Considering the instability of H2O2, we have attempted to use NTP to activate water instead of H2O2 and optimize the polymerization to achieve better effectiveness. In this study, we have also demonstrated that for the synthesis of PEDOT, an acidic condition is more suitable for more radical formation and a mild heating procedure could be used for better polymerization. Further characterizations revealed that the final product of PEDOT:PSS was not only biocompatible but also comparable to other approaches regarding conductivity. |
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The effect of nonthermal plasma on the oxidation and removal of particulate matter under different diesel engine loads |
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Kan Zhu, Yixi Cai, Yunxi Shi, Yirui Lu, Yin Zhou, Yong He |
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China |
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https://doi.org/10.1002/ppap.202100104 |
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Nonthermal plasma (NTP) can oxidize and decompose particulate matter (PM) of diesel engines at low temperatures (≤200°C), exhibiting good application prospects. PM samples were collected under different diesel engine loads and were oxidized using an NTP method. The volatile fraction (VF) mass fraction of the PM samples decreases under low engine loads (<70%) and increases under high engine loads (≥70%) after the NTP treatment. NTP can remove aldehyde groups in PM and weaken the volatilization of PM. A higher temperature is needed for the VF to reach its maximum volatilization rate after the NTP treatment. The relative content of the small molecules is significantly higher after the NTP treatment. |
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Applications of plasma synthesized ZnO, TiO2, and Zn/TiOx nanoparticles for making antimicrobial wound-healing viscose patches |
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Nikolay Sirotkin, Anna Khlyustova, Dmitry Costerin, Irina Naumova, Valeriy Titov, Alexander Agafonov |
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Russia |
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https://doi.org/10.1002/ppap.202100093 |
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In this study, an environment-friendly, energy-saving, and useful synthesis of zinc oxide (ZnO) nanoparticles (NPs), titanium oxide (TiO2) NPs, and mixed Zn/TiOx-NPs was achieved using underwater pulse discharge plasma. The obtained NPs were characterized by UV spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. In the discharge cell, the viscose patch is impregnated with ZnO, TiO2, and mixed Zn/TiOx-NPs in a one-step process. The adhesive patch is effective against Escherichia coli, Staphylococcus albicans, and Bacillus subtilis. The viscose patch containing 0.22% Zn/TiOx-NPs demonstrated the highest antimicrobial activity. These antimicrobial patches can be used to treat and cover wounds susceptible to infection. |
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Investigation of the chemical characteristics and anticancer effect of plasma-activated water: The effect of liquid temperature |
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Bolun Pang, Zhijie Liu, Huaiyan Zhang, Sitao Wang, Yuting Gao, Dehui Xu, Dingxin Liu, Michael G. Kong |
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P.R. China |
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https://doi.org/10.1002/ppap.202100079 |
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The liquid temperature during the preparation of plasma-activated water (PAW) seriously affects the PAW chemical characteristics and its biological effect. In this study, four different temperatures (4°C, 25°C, 40°C, and 70°C) of deionized water are selected as variable parameters to investigate the effect on PAW. The results show that the physicochemical properties and the concentration of reactive oxygen and nitrogen species of PAW are significantly reduced when the temperatures are higher than 25°C; moreover, the above indexes are slightly decreased when the temperature is down to 4°C. Furthermore, by comparing the results of cell viability and apoptosis, it is found that the PAW of 25°C has a higher inactivation efficiency than other temperatures. Research on the temperature effect during PAW production is beneficial for tailoring the plasma–liquid system to enhance production efficiency. |
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Parallel and independent true random bitstreams from optical emission spectra of atmospheric microplasma arc discharge |
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Di Zhang, Sohaib Majzoub, Anis Allagui, Ahmed Elwakil |
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UAE |
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https://doi.org/10.1002/ppap.202100141 |
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In this study, we propose the possibility of generating several parallel and independent random bitstreams from the time-varying optical emission spectra of an atmospheric pressure air microplasma system. This is achieved by splitting the plasma arc emission into discrete wavelengths using an optical spectrometer and then monitoring the fluctuating intensities of each wavelength as an independent time series. As a proof of concept, we considered eight wavelengths centered at 377.8, 389.1, 425.8, 591.4, 630.5, 673.0, 714.2, and 776.4 nm corresponding to atomic emissions lines from species either from the surrounding atmospheric air gap or from the electrodes' materials. NIST SP 800-22 statistical randomness tests and other statistical estimates (auto- and cross-correlation analysis and binary vector similarity measures) are subsequently applied to the binarized data, and the obtained results confirm the possibility of generating several parallel and independent random bitstreams from the microplasma system. The data throughput is, however, relatively low with the optical setup we used, which can be improved using faster spectrometry. |
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Entering the plasma agriculture field: An attempt to standardize protocols for plasma treatment of seeds |
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Alexandra Waskow, Fabio Avino, Alan Howling, Ivo Furno |
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Switzerland |
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https://doi.org/10.1002/ppap.202100152 |
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Plasma treatments are currently being assessed as a seed processing technology for agricultural purposes. There is sufficient information as a proof-of-concept, but a lack of standardization in the methodology prevents a convincing evaluation of plasma treatment on seeds. It would be helpful to coordinate research efforts to make the entry for newcomers into this interdisciplinary field less overwhelming and to aid in transferring this technology into the industry by establishing a common protocol. This review presents the parameters used in the seed preparation, the plasma treatment of the seed, and the seed posttreatment. This summary of the plasma and biological parameters is intended to raise awareness about questions that need to be addressed to properly record protocol details and reproduce results for the plasma treatment of seeds. |
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Effect of dielectric parameters on the transformation of operation mode and the energy cost of nitrogen fixation of surface microdischarge in air |
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Chen Lu, Xingyu Chen, Yuqi Wang, Yu Zhu, Zhenping Zou, Zilan Xiong |
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China |
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https://doi.org/10.1002/ppap.202100107 |
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In this study, we examine the effect of dielectric parameters (permittivity of the dielectric sheet urn:x-wiley:16128850:media:ppap202100107:ppap202100107-math-0001 and thickness of the dielectric sheet urn:x-wiley:16128850:media:ppap202100107:ppap202100107-math-0002) on the operational mode transformation and energy cost of nitrogen fixation in surface microdischarge (SMD). Three dielectric materials with different thicknesses were used. It was found that urn:x-wiley:16128850:media:ppap202100107:ppap202100107-math-0003 has a negative correlation with the power consumption, while a larger urn:x-wiley:16128850:media:ppap202100107:ppap202100107-math-0004 could effectively lower the applied voltage for mode transformation and decrease the energy cost. The trend of energy cost has the shape of a checkmark symbol (√), and the lowest energy cost in this investigation was 489.07 GJ/tN. Increasing urn:x-wiley:16128850:media:ppap202100107:ppap202100107-math-0005 and reducing urn:x-wiley:16128850:media:ppap202100107:ppap202100107-math-0006 could further decrease the energy cost in SMD. Finally, the mechanism was briefly discussed. |
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Effect of electrode configurations on the characteristics of the ring–ring typed atmospheric pressure plasma jet and its modification on polymer film |
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Tao Wang, Shengquan Wang, Jiahao Wang, Sile Chen, Meng Li, Liping Shi, Xingquan Zhang |
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China |
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https://doi.org/10.1002/ppap.202100139 |
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This paper investigates the effect of three different ring electrode configurations (copper wire electrode [CWE], copper foil electrode [CFE], and copper block electrode [CBE]) on the characteristics of the ring–ring typed atmospheric pressure plasma jet (APPJ) and polyethylene terephthalate modification. The characteristics of APPJ were simulated and experimentally explored. The results show that APPJ with CWE has the maximum electric field magnitude, power, concentration of reactive species, and gas temperature. While CBE has the most uniform electric field distribution and the most stable discharge process. Besides, CWE has the maximum hydrophilization rate while the CBE has the most uniform modification area. The plasma characteristics and modification effect of APPJ with CFE fall in between. |
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Highly spherical SiC nanoparticles grown in nonthermal plasma |
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Pavel Galář, Jiří Stuchlík, Martin Müller, Jan Kočka, Kateřina Kůsová |
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Czechia |
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https://doi.org/10.1002/ppap.202100127 |
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Silicon carbide (SiC) nanoparticles have excellent properties and varied possible applications. However, the synthesis of this material usually requires high temperatures due to its high melting point (2730°C). In this study, we report on a synthesis of highly spherical SiC nanocrystals (50–150 nm) using nonthermal plasma, a method not yet widely employed for the synthesis of SiC, but generally very suitable for high-melting-point materials. We perform the synthesis in a two-stage reactor, where Si nanocrystals are synthesized in the first stage and these are used as growth seeds for SiC in the second stage. The Si nanocrystals remain inside the SiC nanoparticles after the synthesis. The produced SiC nanocrystals exhibit yellow-orange naked-eye-visible photoluminescence. |
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Efficient trapping of RONS in gelatin and physiological solutions |
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Kinga Kutasi, Etelka Tombácz |
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Hungary |
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https://doi.org/10.1002/ppap.202100077 |
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The work aims to determine the long-term stability of reactive oxygen and nitrogen species (RONS)-enriched gelatin solutions and of plasma-activated physiological solutions produced with an atmospheric pressure surface-wave microwave discharge. It is demonstrated that the H2O2, NO3- and NO2- concentrations are quasi-stable during 1 month of storage in the 0.5%–2% gelatin solutions prepared with plasma-activated water, Ringer's (PAR), and phosphate-buffered saline (PAPBS) solutions, respectively, even at acidic pH 4.5–5.5 conditions. The trapping of RONS is attributed to the protein network developed with gelation. The salt content of the physiological solutions influences the RONS creation and deposition, while stabilizes the 6.5 and 7.2 pH, which ensures the stability of the PAR and PAPBS, respectively, for months. |
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Numerical investigation on the heterogeneous pulsed dielectric barrier discharge plasma catalysis for CO2 hydrogenation at atmospheric pressure: Effects of Ni and Cu catalysts on the selectivity conversions to CH4 and CH3OH |
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Jun Du, Lijun Zong, Shuai Zhang, Yuan Gao, Liguang Dou, Jie Pan, Tao Shao |
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China |
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https://doi.org/10.1002/ppap.202100111 |
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The simulation model of the pulsed dielectric barrier discharge plasma catalytic CO2 hydrogenation is established to numerically investigate the effects of Ni and Cu catalysts on the selectivity conversions to CH4 and CH3OH. Under plasma without catalyst, the electron impact CO2 and CO produce CO and C, and then stepwise hydrogenations of CO and C generate CH3OH and CH4. Under plasma with Ni catalyst, Langmuir–Hinshelwood (LH) reactions mainly form the CHx(s) and Eley–Rideal (ER) reaction CH3(s) + H → CH4 are the key paths of CH4 synthesis. Under plasma with Cu catalyst, the intermediate CH3O(s) is principally produced by the LH reaction between CH2O(s) and H(s), followed by the ER reaction CH2O(s) + H → CH3O(s). While CH3OH(s) is mainly produced by the ER reaction CH3O(s) + H → CH3OH(s), CH3O(s) + H(s) → CH3OH(s) + S is a rate-limiting step owing to the higher reaction energy barrier. |
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Hydrophilic to hydrophobic: Ultrafast conversion of cellulose nanofibrils by cold plasma fluorination |
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Ana Oberlintner, Vasyl Shvalya, Aswathy Vasudevan, Damjan Vengust, Blaž Likozar, Uroš Cvelbar, Uroš Novak |
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Slovenia |
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https://doi.org/10.1016/j.apsusc.2021.152276 |
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• Ultrafast hydrophobic cellulose nanofibrils films fabrication by cold plasma.
• Hydrophilic to hydrophobic conversion of the surface by cold plasma fluorination. • Achieved water contact angles as high as 130°after 30 s of treatment. • In-depth FTIR, Raman, XPS and SEM analysis of the modified surface. |
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The cellulose-based products are gaining increased interest, especially as a top-choice material for replacing plastics in packaging-related fields. Nevertheless, the high inherent wettability often hinders its advancement in becoming an efficient substitute in packaging industry. To bridge this challenge,the fluorocarbon plasma processing was implemented for improvement of cellulose surface hydrophobicity. This was done on the example of nanofibrils films exposed to CF4 plasma, in order to achieve hydrophilic to hydrophobic conversion in less than 10 s. The saturation of water contact angle (approximately 130 +/-5°) was obtained after only 30s of plasma processing. The surface fluorination was the result of the presence of newly formed C–F3, C–F2 and C–F bonds confirmed by high-resolution C 1s XPS spectra. A prolonged continuous plasma functionalization resulted in structural vibrational alterations associated mostly with intense IR and Raman active stretching C–F2 mode. Simultaneously, ATR-FTIR revealed a formation of the surface-linked IR active H–F functional group. Our findings successfully demonstrate that the CF4 plasma processing can be an effective way for ultrafast cellulose conversion from hydrophilic to hydrophobic surface. |
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Promotion of biofilm production via atmospheric-pressure plasma-polymerization for biomedical applications |
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Elisa Sainz-García, María López, Rodolfo Múgica-Vidal, Beatriz Rojo-Bezares, Carmen Lozano, Ana González-Marcos, Paula Toledano, Ignacio Muro-Fraguas, Ana Sainz-García, Yolanda Sáenz, Fernando Alba-Elías |
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Spain |
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https://doi.org/10.1016/j.apsusc.2021.152350 |
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• Plasma-polymerization promoted P. aeruginosa biofilm formation on polystyrene dishes.
• 3-(Aminopropyl)triethoxysilane was deposited in different numbers of passes. • The more passes applied, the higher roughness and biofilm production were. • The coatings promoted bacterial attachment and accumulation in surface valleys. • Relative biofilm formation on coatings after 24 h incubation: 157% − 457%. |
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The ability of bacteria to form biofilms that enhance their resistance to disinfectants and antibiotics is a matter of concern in the fields of food processing and healthcare. Since culture conditions in laboratories are not exactly the same as in the real environments where bacterial infection takes place, developing models that rapidly produce biofilm on test surfaces has become an interesting topic of research. In this work, Pseudomonas aeruginosa biofilm production on polystyrene Petri dishes was promoted by atmospheric-pressure plasma-polymerization of 3-(Aminopropyl)triethoxysilane (APTES). Different coatings were deposited varying only the number of plasma-polymerization passes. Biofilm productions, ranging from 157% to 457% relative to that on the uncoated dishes, were quantified after 24-h incubation. According to morphological and chemical characterizations, the APTES precursor promoted biofilm production in several ways: providing amines that facilitated the attachment of more bacterial cells than on uncoated dishes, inducing an oxidative stress to the attached bacteria that caused an overproduction of extracellular polymeric substances, and generating siloxane-based particles that formed a granular pattern that facilitated bacterial accumulation in its valleys. Comparing the coatings, a direct relationship was identified between the number of plasma-polymerization passes, the roughness and the biofilm production. |
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ZnO nanofibers prepared by plasma assisted calcination: Characterization and photocatalytic properties |
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Veronika Medvecká, Juraj Surovčík, Tomáš Roch, Miroslav Zahoran, David Pavliňák, Dušan Kováčik |
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Slovak Republic, Czech Republic |
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https://doi.org/10.1016/j.apsusc.2021.152384 |
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• ZnO nanofibers were fabricated by plasma assisted calcination (PAC) method.
• Plasma pre-treatment preserve well-defined fibrous mat during thermal treatment. • ZnO nanofibers prepared by PAC exhibit enhanced photocatalytic activity. |
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The ZnO nanofibers (ZnO-NF) have been fabricated by the novel approach of plasma assisted calcination using the low-temperature atmospheric pressure plasma generated by diffuse coplanar surface barrier discharge (DCSBD). The electrospun polyvinyl pyrrolidone/zinc acetate fibers were exposed to DCSBD plasma before the thermal processing at different temperatures (400 °C,500 °C and 600 °C) and characterized in term of chemical composition and morphological structure by ATR-FTIR, XPS, SEM, XRD, and BET analysis. The photocatalytic activity of prepared ZnO-NF has been investigated under UV-radiation using methylene blue and the kinetics of photodegradation and reusability were studied. The results showed that initial removal of organic matrix at low-temperature by application of plasma leads to better formation of Zn-O even at lower calcination temperature. The plasma pre-treated (PT) fibers exhibit lower diameter of final products and helps to preserve a well-defined fibrous structure during thermal processing. The ZnO-NF prepared by a combination of plasma treatment and thermal processing showed significantly higher photodegradation activity and the difference was higher with decreasing calcination temperature. The highest rate constants were reached for fibers calcined at 600 °C with and without plasma treatment – kPT = 0.0149 min−1, kNT = 0.0107 min−1, respectively. The slight improvement of re-usability in cyclic photodegradation was observed on samples calcined at 600 °C. |
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Suppression of combustion mode transitions in a hydrogen-fueled scramjet combustor by a multi-channel gliding arc plasma |
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Rong Feng, Jiajian Zhu, Zhenguo Wang, Fan Zhang, Yangyang Ban, Guoyan Zhao, Yifu Tian, Chenglong Wang, Hongbo Wang, Zun Cai, Mingbo Sun |
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China |
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https://doi.org/10.1016/j.combustflame.2021.111843 |
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A multi-channel gliding arc (MCGA) plasma was utilized to suppress combustion mode transition in a hydrogen-fueled cavity-based scramjet combustor with an inflow speed of Ma2.92. Several optical and electrical techniques, including OH* chemiluminescence, optical emission spectrum, discharge waveform acquisition, and pressure measurements, were employed to show the characteristics of the MCGA discharge and the processes of the combustion mode transitions. When the MCGA is off, the flame frequently oscillates between a cavity shear-layer mode and a cavity-stabilized mode at a low global equivalence ratio, whereas the flame is more likely to be kept in the cavity-stabilized mode when the MCGA is on. The ratio of the cavity-stabilized mode increases from 28.2% to 93% when the plasma is on. The combustion frequently oscillates between a cavity-stabilized mode and a jet-wake stabilized mode at a high global equivalence ratio, but the mode transitions can be suppressed significantly in the presence of the MCGA. The ratio of the jet-wake stabilized increases from 21.9% to 48.8% when the MCGA is on. The Proper Orthogonal Decomposition (POD) method is employed to analyze the oscillation, and it is found that the mean energy content of the large-scale oscillation across the different modes can be significantly suppressed by the MCGA. A plausible explanation can be mainly related to the reactions of species with O generated by the MCGA, which increases the temperature in the vicinity of the plasma. The temperature rises spread to the entire cavity with higher backpressure, and results in better mixing and more intense combustion, leading to the suppression of the combustion mode transitions. |
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The active role of organic molecules in the formation of long-lived reactive oxygen and nitrogen species in plasma-treated water solutions |
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Valeria Veronico, Pietro Favia, Francesco Fracassi, Roberto Gristina, Eloisa Sardella |
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Italy |
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https://doi.org/10.1002/ppap.202100158 |
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Plasma-treated water solutions (PTWS) allow the delivery of reactive oxygen and nitrogen species (RONS) to cells and tissues for different purposes. The mechanism of RONS formation has been clearly modelled in simple liquids like water, by assuming a plasma-driven process independent from the liquid. PTWS for biological experiments, however, are often produced from solutions of complex composition, where the formation mechanism of RONS is far from being understood. In this paper, we describe how water, phosphate-buffered saline solution and two cell culture media were plasma-treated in different conditions to demonstrate how the different composition of the liquids affects the formation of stable RONS (H2O2 and NO2−) in the resulting PTWS, especially when aromatic organic molecules are present. |
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Promoting volatile organic compounds removal by a magnetically assisted nanosecond pulsed gear-cylinder dielectric barrier discharge |
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Nan Jiang, Yun Sun, Bangfa Peng, Jie Li, Kefeng Shang, Na Lu, Yan Wu |
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China |
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https://doi.org/10.1002/ppap.202100108 |
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In this study, a magnetic field perpendicular to the electric field is introduced to the gear-cylinder dielectric barrier discharge (DBD) to enhance the plasma density and improve the volatile organic compounds removal performance at atmospheric pressure. Higher discharge intensity, enlarged plasma streamers region, and better toluene removal performance are obtained after introducing a 0.2 T magnetic field due to the intensified ionization reactions caused by the Larmor movement of electrons. Time-resolved Intensified Charge-coupled Detector images indicate that both the propagation velocities of the primary and secondary streamers are enhanced and their durations are prolonged by the magnetic field. The optical emission spectra results imply that the vibrational temperature (Tvib) of N2(C-B) and the reduced electric field (E/N) are promoted by applying the magnetic field, while the rotational temperature (Trot) of N2(C-B) is rarely affected by the magnetic field. There is an optimal combination between the electric field and magnetic field in the gear-cylinder DBD reactor, according to the mechanism of the magnetically assisted DBD plasma. The pulsed discharge current, toluene removal efficiency, and energy yield with the magnetic field are increased by 26%–40%, 50%–70%, and 7%–20% within the range of 16–20 kV, respectively, compared to those without the magnetic field, implying that magnetically assisted DBD plasma presents superior toluene degradation performance compared to common DBD plasma. |
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Degradation of gemfibrozil in aqueous solutions by gas–liquid dielectric barrier discharge plasma combined with CNTs/γFe2O3 |
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Zimu Xu, Bin Zhu, Zhengxin Ye, Nannan Zhang, Jie Shen, Yan Lan, Shuheng Hu, Cheng Cheng, Yunxia Li, Fan Yang, Paul K. Chu |
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China |
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https://doi.org/10.1002/ppap.202100122 |
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The degradation effects and mechanism on gemfibrozil (GEM) in aqueous solution by dielectric barrier discharge (DBD) plasma combined with the catalyst CNTs/γFe2O3 are investigated. The concentrations of plasma-generated reactive species, including H2O2, O3, , and OH, are measured with spectrophotometric and fluorescent probes. The effects of the plasma treatment period, discharge power, initial GEM concentration, solution pH value, conductivity, and the catalytic property are studied on the degradation rate and energy efficiency. Compared with the sole plasma treatment, CNTs/γFe2O3 could maximally improve the GEM degradation rate and energy efficiency to 99.7% ± 0.2% and 76.5 ± 5.2 mg·kW−1·h−1, respectively. The solution's total organic carbon removal efficiency has been increased to 47.2% ± 2.7%. Meanwhile, the possible degradation pathways of the plasma-treated GEM solution and overall biological toxicity of GEM degradation intermediates and residual catalyst in solution are investigated. |
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Cold atmospheric plasma decontamination of SARS-CoV-2 bioaerosols |
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Alina Bisag, Pasquale Isabelli, Giulia Laghi, Romolo Laurita, Giorgio Dirani, Francesca Taddei, Cristiana Bucci, Filippo Capelli, Matteo Gherardi, Alessandro Paglianti, Vittorio Sambri, Vittorio Colombo |
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Italy |
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https://doi.org/10.1002/ppap.202100133 |
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Bioaerosols (aerosolized particles with biological origin) are strongly suspected to play a significant role in the transmission of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), especially in closed indoor environments. Thus, control technologies capable of effectively inactivating bioaerosols are urgently needed. In this regard, cold atmospheric pressure plasma (CAP) can represent a suitable option, thanks to its ability to produce reactive species, which can exert antimicrobial action. In this study, results; on the total inactivation of SARS-CoV-2 contained in bioaerosols treated using CAP generated in air are reported, demonstrating the possible use of CAP systems for the control of SARS-CoV-2 diffusion through bioaerosols. |
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Enhanced aerosol deposition by a low-cost compact nanosecond-pulsed plasma system |
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Haotian Gao, Jiacheng Li, Dawei Liu |
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China |
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https://doi.org/10.1002/ppap.202100147 |
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Nanosecond (ns)-pulsed air plasmas are promising for environmental and biomedical applications. This paper presented a low-cost ns-pulsed plasma system that consists of a two-stage Cockcroft–Walton voltage multiplier, a spark gap gas switch, and a plasma reactor. This ns power supply generated a uniform air plasma with a volume of 25 × 25 × 2 cm and a maximum ion wind of 0.8 m/s. The ion wind transported aerosols through plasma volume. Aerosols were charged and deposited on the grounded mesh electrode. The direct interactions between reactive ns plasma and deposited aerosols can promote the development of plasma applications. |
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Toward defining plasma treatment dose: The role of plasma treatment energy of pulsed-dielectric barrier discharge in dictating in vitro biological responses |
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Abraham Lin, Eline Biscop, Yury Gorbanev, Evelien Smits, Annemie Bogaerts |
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Belgium |
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https://doi.org/10.1002/ppap.202100151 |
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The energy dependence of a pulsed-dielectric barrier discharge (DBD) plasma treatment on chemical species production and biological responses was investigated. We hypothesized that the total plasma energy delivered during treatment encompasses the influence of major application parameters. A microsecond-pulsed DBD system was used to treat three different cancer cell lines and cell viability was analyzed. The energy per pulse was measured and the total plasma treatment energy was controlled by adjusting the pulse frequency, treatment time, and application distance. Our data suggest that the delivered plasma energy plays a predominant role in stimulating a biological response in vitro. This study aids in developing steps toward defining a plasma treatment unit and treatment dose for biomedical and clinical research. |
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Tailoring electric field signals of nonequilibrium discharges by the deep learning method and physical corrections |
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Yifei Zhu, Yin Bo, Xiancong Chen, Yun Wu |
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China |
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https://doi.org/10.1002/ppap.202100155 |
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Smart modulation of discharges is necessary to generate specific reactive species in an energy-efficient way. A physics corrected plasma + deep learning framework, the DeePlaskin, is proposed. This framework can be used for the nonequilibrium plasma systems that can be described by a global chemistry model (assuming global uniformity, e.g., in spark channels or the early afterglow of the fast ionization wave discharges). Knowing the kinetics scheme and the predefined temporal evolution of target species, we will be able to reconstruct the temporal profile of the reduced electric field and all the other species. To generate the same concentration of O atom at the end of the discharge, the electric field profiles customized by the DeePlaskin differ significantly depending on the predefined evolution, resulting in different energy consumption. The combination of the deep learning method and plasma physics/chemistry model shows great potential in optimizing the design of plasma sources in practical applications. |
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Effects of applied voltage waveform on the uniformity of a microplasma array confined inside polydimethylsiloxane microchannels |
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Shuqun Wu, Xuhui Liu, Fan Ouyang, Yunxiang Luo, Yue Guo, Chaohai Zhang |
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China |
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https://doi.org/10.1002/ppap.202100164 |
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The uniformity of the microplasma array is essential to modify the hydrophilicity of the inner surface of polydimethylsiloxane (PDMS) microchannels by plasma treatment. In this study, the effects of applied voltage waveforms on the uniformity of the microplasma array are investigated. Interestingly, the microplasma array excited by AC (alternate current) voltage looks more “uniform” by a digital camera and has higher gas temperature and electron density than that excited by unipolar and bipolar pulse voltage. Imaging the microplasma array by a fast intensified charge-coupled device camera shows that the ignition of microplasma inside each microchannel has strong randomness in spatial distribution, and the opportunity of each microchannel being ignited is almost equal. Detailed analysis reveals that the low density of surface charges and the small overvoltage in the case of AC voltage are expected to play crucial roles in the stochastic behavior of microplasma ignition inside PDMS microchannels. This study is useful for understanding the uniformity of the microplasma array for surface modification of PDMS microchannels. |
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Nonthermal tetravinylsilane plasma used for thin-film deposition: Plasma chemistry controls thin-film chemistry |
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Vladimir Cech, Martin Branecky |
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Czech Republic |
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https://doi.org/10.1002/ppap.202100192 |
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The power dependence of the plasma species in nonthermal tetravinylsilane plasmas used for thin-film deposition is investigated by mass spectrometry. Mass spectra analysis reveals the dominant carbon- and silicon-containing species responsible for film growth. The deposition rate determined by in situ spectroscopic ellipsometry correlates with the flux of these species chemisorbed on the film surface if distinct sticking coefficients are taken into account. Then, the carbon to silicon ratio in the deposited film strongly correlates with the C/Si flux ratio for the various power-controlled plasmas. Similarly, the concentration of vinyl groups incorporated into the deposited film and the proportion of sp2 hybridization of the carbon network correlate with the fluxes of the respective plasma species. |
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The study of plasma effects on quinine solutions |
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Michaela Procházková, Joanna Pawlat, František Krčma, Zdenka Kozáková |
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Czech Republic |
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https://doi.org/10.1002/ppap.202100184 |
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This study compares the effects of nonthermal plasma treatment on quinine water solutions for two configurations—the corona-like discharge and the gliding arc discharge (GAD). Different electrolytes were added to the quinine solutions to modify the initial pH and enhance electrical conductivity for plasma discharge ignition directly in the liquid. A slightly higher quinine decomposition rate of 2.9 μg W−1 after 5 min of the treatment was achieved by GAD. From measured spectra, it was found that the absorption maximum at 332 nm was split into two separated peaks in the acidic and basic solution. The study of the time stability of quinine solutions has revealed quinine instability and that postpreparation time has influenced the plasma treatment effect. |
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A novel two-dimensional atmospheric pressure plasma jet device |
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Nanya Zhong, Gang Fu, Junjun Li, Chen Lian, Wenqi Chen, Kama Huang |
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China |
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https://doi.org/10.1002/ppap.202100159 |
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A novel two-dimensional atmospheric pressure plasma jet device is proposed for large-area processing. A finite element algorithm is adopted to obtain the optimized dimensions of the designed device based on microwave power reflection coefficient |S11| and electric field intensity. The plasma parameters of electron density ne and electron temperature Te within 0.1 ms after microwave power input were analyzed. When plasma is fully excited, ne is close to 3.5 × 1018 m−3, and Te is calculated to be 2 eV. Besides, an experimental system is established, and microwave power of 70 W can process 30 L of argon per minute, which shows a high energy efficiency. Two plasma jets with a width of 10 mm and a length of 5 mm are successfully excited. In addition, reflected power measured by the power meter is only 9.5% of incident power, which is in good agreement with simulation results. |
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Characterization of Cold Atmospheric Pressure Plasma Technology and Its Anticancer Properties |
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Hom Bahadur Baniya, Pabitra Khadka, Sudip Panday, Anusuya Nepal, Rajesh Prakash Guragain, Tika Ram Lamichhane, Santosh Dhungana, Bhupal Govinda Shrestha, Deepak Prasad Subedi |
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Nepal |
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Plasma Medicine, 11(4):53–62 (2021)
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The anticancer properties of plasma were studied by treating Dulbecco’s modi fied Eagle’s medium (DMEM) with cold atmospheric pressure plasma (CAPP). The CAPP was generated by using high voltage power supply (11.75 kV) at an operating frequency of 50 Hz. The DMEM was treated with cold plasma using argon as the process gas for the different exposure time ranging from 0.5 to 3 minutes. The treated media were transferred to Henrietta Lacks (HeLa) and Human Embryonic Kidneys 293 (HEK 293) cells. The viability of cancer cells was observed using 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Cold atmo spheric pressure plasma discharge has been characterized by electrical and optical methods. The cold plasma treatment selectively killed cancer cells without affecting normal cells in vitro. It has been observed that the percentage viability of the cell lines varies with the plasma treatment time along the best fitted curve of a power function. The curve is steeper for the cancer cells than for the normal cells after plasma treatment. The faster decaying curve signifies the selective killing of the cancer cells compared to the normal cells within the exposure time. This study indicates that the reactive oxygen species in the CAPP activate the apoptosis pathway in the cancer cells. As a novel strategy, using the CAPP stimulated media has become a promising anti-cancer tool. |
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UV Dissociation and Calculation for O3 Gas Generated from Nonthermal Atmospheric-Pressure Biocompatible Plasma Sterilizer |
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Jang Sick Park, Se Hoon Ki, Do Young Kim, Young Oh Shin, Eun Ha Choi |
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Korea |
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Plasma Medicine, 11(4):63–72 (2021)
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Nonthermal atmospheric–pressure biocompatible plasma (NBP) sterilizers effec tively deactivate microorganisms, such as viruses, bacteria, and fungi, using eco-friendly treat ment methods without generating any waste or toxic by-products. The ozone density generated from the plasma source of surface microdischarge (SMD) in plasma sterilizers has been decreased by 70%, resulting in a density of less than 0.05 ppm, whereas the densities of OH and H2O2 have significantly increased due to UV-C dissociation with a high absorption cross section for ozone gas. The ozone density was calculated by estimating the oxygen atoms using the major reaction equations for ozone formation and dissociation, and measurement of the time constant of diffu sion decrease (τdif). The ratio of the O density for the O3 density generated from the plasma source decreased as the distance between the ozone measurement locations and the plasma source in creased. In particular, the excited state density of atomic oxygen O(1D) could be estimated at the downstream region of the air outlet in this study. |
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Cold Plasma Generation of Peracetic Acid for Antimicrobial Applications |
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Bhagirath Ghimire, Endre J. Szili, Bethany Lee Patenall, Adrian Fellows, Dharmit Mistry, Andrew Toby A. Jenkins, Robert D. Short |
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UK, Australia |
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Plasma Medicine, 11(4):73–84 (2021) |
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This study compares how a helium plasma jet activates peracetic acid (PAA) from tetraacetylethylenediamine (TAED) and acetic acid (AA). Hydrogen peroxide (H2O2) generated from the plasma jets reacts with TAED resulting in the formation of PAA which further dissoci ates into AA. The by-product AA can also react with H2O2 to form PAA, which might also be use ful for antimicrobial applications when coupled with plasma. Equivalent concentrations of TAED and AA solutions are used to compare the formation of PAA after activation with a helium plasma jet. Our results showed that the concentrations of both H2O2 and PAA in plasma-activated TAED (PAT) are higher than plasma-activated AA (PAAA), and that PAT is more efficient in reducing the growth of Pseudomonas aeruginosa and Staphylococcus aureus; the pathogens commonly found in wounds. The results are attributed to the presence of more acetyl donor groups in TAED, resulting in the formation of higher concentrations of PAA and H2O2. |
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Impact of Bacterial Growth Phase on Liquid Decontamination Efficiency Using Atmospheric Pressure Plasma |
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Ibtissam Courti, Cristina Muja, Thomas Maho, Florent P. Sainct, Philippe Guillot |
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France, Germany |
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Plasma Medicine, 11(4):85–104 (2021)
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Atmospheric pressure plasma processes have been increasingly studied for the microbiological decontamination of liquids. Plasma discharges produce a series of reactive oxy gen and nitrogen species (RONS) that diffuse through cell membranes, triggering complex bio chemical processes leading to physical and chemical changes in bacteria. The efficiency of plasma liquid decontamination is influenced by the Gram type of bacteria, the bacterial strain, the cell density, and the physiological state of bacteria. The objective of this study was to examine how bacterial growth phases affect the efficiency of plasma liquid decontamination. An atmospheric plasma multijet was used to treat Escherichia coli K12, in the midexponential and stationary phases of growth. The plasma discharge was characterized by optical emission spectroscopy, and the reactive oxygen and nitrogen species (RONS) formed in the treated liquid were quantified by spectrophotometry. The viability assays showed that the growth phase of bacteria influences the effectiveness of the treatment. Cells in the midexponential phase were more susceptible to plasma treatment than stationary-phase cells. After 30 min of plasma treatment, the plasma produced a complete inactivation 7 log reduction in bacteria in the midexponential phase while only a 3 log reduction was observed in stationary phase. Metabolic activity and membrane integrity measure ments confirmed the increased sensitivity of exponential phase bacteria compared to stationary cells. In order to study the mechanisms involved in the bactericidal process and cellular defense against plasma-induced oxidative stress, we focused on intracellular ROS levels and genomic DNA damage. The results show a significant difference in intracellular ROS levels between the two phases of growth. However, DNA degradation extent did not reveal any significant differenc es. These results suggest that a combination of physiological and metabolic responses determine bacterial survival for both growth phases after exposure to plasma treatment. |
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Multi-Electrode Plasma Torch Characterization for Rapid Wound Healing and Sterilization |
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Bhavya Bellannagari, Syed Hassan A. Kazmi, Sohail H. Zaidi |
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USA |
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Plasma Medicine, 11(4):105–116 (2021 |
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A multi-electrode dielectric barrier discharge (DBD) plasma jet device/plasma torch is designed and tested. It is shown that plasma characteristics (plasma temperature and radi cal relative concentration) can be varied in a passive manner without changing the plasma input power and working gas flow rates. For this purpose, several outer electrodes are mounted on the plasma torch/device exiting ceramic tube that acted as a dielectric medium to produce a dielectric barrier discharge (DBD) plasma. Additionally, it is found that plasma characteristics strongly depends on the choice of outer electrode. The DBD plasma discharge was generated using helium at voltages up to 10 kV and 25 kHz with input power that was less than 20 W at all operating conditions. Plasma temperatures were measured along the plasma jet with a thermocouple and spectroscopy was conducted to capture the relative concentration of various radicals including various nitrogen second positive system, OII, and multiple helium lines. Plasma wound healing and sterilization processes were investigated and for this purpose blood coagulation process was captured in real time showing that plasma exposure could accelerated the coagulation process. Preliminary work on bacteria mitigation was conducted by exposing Escherichia coli K-12 to a plasma jet and then investigating/counting the bacterial colonies to estimate the plasma impact. |
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Critical Aspects in Generation, Analysis, and In Vitro Testing of RONS in Plasma-Treated Water Solutions for Cancer Treatments |
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Valeria Veronico, Francesco Fracassi, Pietro Favia, Roberto Gristina, Eloisa Sardella |
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Italy |
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Plasma Medicine, 11(4):117–135 (2021)
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Plasma-treated water solutions (PTWS) containing reactive oxygen and nitrogen species can be generated by means of different plasma processes. The delivery of these species through PTWS demonstrated useful for the redox control of many physiological and pathological states, including cancer. Many critical aspects need to be considered in the study of these liquids, namely: the plasma process, the choice of the liquid to be treated, its analysis and the experimen tal protocols to test its biological effects. Flaws and inaccuracies in each of these steps actually limit the prevision of the clinical efficacy and impair the comparison of results among different laboratories. The aim of this short review is to offer an overall view on the topic, with highlights on the critical aspects in the generation, characterization and use of liquids processed by plasma to selectively attack cancer cells. |
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Synergistic catalytic degradation of ciprofloxacin using magnetic carbon nanomaterial/NiFe2O4 promoted cold atmospheric pressure plasma jet: Influence of charcoal, multi walled carbon nanotubes and walnut shell |
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Alireza Badi Sar, Eslam Ghareh Shabani, Mohammad Haghighi, MaryamShabani |
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Iran |
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https://doi.org/10.1016/j.jtice.2021.10.031 |
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• Synergism effect of hybrid atmospheric non-thermal plasma jet-magnetic carbon nanomaterial/NiFe2O4.
• Excellent ciprofloxacin remediation over 0.25 g/L charcoal-atmospheric plasma jet and charcoal/NiFe2O4-atmospheric plasma jet. • Facilitation of separation and inceasing active species and their lifetime. |
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Background:
Currently, water polluted to antibiotics such as ciprofloxacin (CIP) has been a main concern for the ecosystem and environment. Hence, the removal of these emerging contaminants is essential. Method: In this research, a hybrid process including magnetic carbon nanomaterial/NiFe2O4 promoted atmospheric non-thermal dielectric barrier discharge plasma jet (APJ) as an environmentally friendly hybrid system was evaluated for eliminating CIP from polluted synthetic effluent. Multi walled carbon nanotubes (MWCNTs), activated carbon formed using charcoal (ChAC), and the walnut shell was applied as the carbonous source. Besides, to solve the separation problem, the charcoal, as optimum sample, was magnetized with NiFe2O4 (ChAC/NiFe2O4) using the treatment solvothermal route. Characterizations of all carbon materials were carried out by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Brunauer-Emmett-Teller and Barrett-Joyner-Halenda and vibrating-sample magnetometer analyses. Finding: The degradation amount for 80 mg/L CIP gained 48.8, 80.8, and 98.1% over APJ system + walnut shell, MWCNTs, and ChAC, respectively, after 90 min at 15 kVp-p output voltage and 0.05 g/L of catalyst loading. The results showed the ChAC/NiFe2O4 (87.2%) had less removal than ChAC (98.1%), but it has magnetic properties that can facilitate the separation problem. |
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Atmospheric pressure plasma jet pretreatment to facilitate cassava starch modification with octenyl succinic anhydride |
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Shengyang Ji, Tao Xu, Weisu Huang, Sunan Gao, Yongheng Zhong, Xuan Yang, Mohamed Ahmed Hassan, Baiyi Lu |
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China |
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https://doi.org/10.1016/j.foodchem.2021.130922 |
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• A novel modification method for starch succinylation is proposed.
• APPJ pretreatment could change the surface structure of native CS. • The DS of OSA–CS improved by 39.23% after CS pretreated by APPJ. • APPJ-OSA-CS exhibited better emulsion stability and emulsion activity. |
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Cassava starch (CS) was pretreated with atmospheric pressure plasma jet (APPJ), followed by esterification with octenyl succinic anhydride (OSA). This study was the first report investigating the effect of APPJ on CS modification with OSA. Results showed that APPJ pretreatment could change the morphological characteristics and crystallinity of CS. Consequently, the degree of substitution and reaction efficiency significantly improved compared with the unpretreated CS (P < 0.05). In Confocal laser scanning microscopy, the fluorescence intensity of OSA-modified CS pretreated with APPJ for 10 min and 15 min was higher than those pretreated with APPJ for 1, 3, and 5 min. The onset temperature and enthalpy (ΔH) of native starch decreased after APPJ pretreatment and further decreased by OSA modification. APPJ–OSA–CS also showed better emulsion stability and emulsion activity. This study demonstrated that APPJ could be used as a novel approach to facilitate starch modification with OSA. |
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Decontamination of 2-Chloroethyl ethyl sulfide on the surface by atmospheric pressure plasma jet |
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Yang Li, Shitong Han, Zhanguo Li, Zhen Liu, Longhui Liang, Keping Yan, Anna Zhu |
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China |
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https://doi.org/10.1016/j.jhazmat.2021.127536 |
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• 2-Chloroethyl ethyl sulfide could be decontaminated in a very short time.
• The device had the characteristic of low power. • The safety has been verified even used on skin surface. • No intermediate products were detected in the gaseous, ensured the safety of personnel operating in open spaces. |
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Atmospheric pressure plasma jet (APPJ) were used to decontaminate the surface’s 2-Chloroethyl ethyl sulfide (2-CEES), a kind of sulfur mustard (HD) simulant. The power of the APPJ device didn’t exceed 7.77 W. Helium APPJ was easier to generate plasma jet than argon APPJ. The treated nude mouse skin surface’s temperature slowly reached 30.4 °C and no obvious lesions in the dermis and skin appendages after 15 min treatment. Compared with argon APPJ, the helium APPJ produced more ·OH and the maximum concentration of ·OH was 3.748 × 10−9 mol/L. Attributed to the low density and more ·OH content, the helium APPJ had a better decontamination effect. With a maximum voltage of 7 kV and a helium flow rate of 4 L/min, 2-CEES (4.53 mg/cm2) can be completely decontaminated in 2.5 min, and no gaseous 2-CEES was detected. The detection of the 2-Hydroxyethyl ethyl sulfide proved the role of ·OH in the reaction system. During the reaction, 2-Chloroethyl ethyl sulfoxide and 2-Chloroethyl ethyl sulfone were also detected. The plasma jet could reduce the toxicity by destroying the parent molecule (2-CEES) in a short time, but it took more time to eliminate the intermediate products. No relevant intermediate products were detected in the gaseous, ensured the safety of personnel operating in open spaces. |
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Ultrafast epitaxial growth of CuO nanowires using atmospheric pressure plasma with enhanced electrocatalytic and photocatalytic activities |
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Avishek Dey, Paheli Ghosh, Gauthaman Chandrabose, Lois A. O. Damptey, Navaratnarajah Kuganathan, Sami Sainio, Dennis Nordlund, Vimalnath Selvaraj, Alexander Chroneos, Nicholas St J. Braithwaite, Satheesh Krishnamurthy |
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UK |
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https://doi.org/10.1002/nano.202100191 |
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This work reports an environment friendly alternative to epitaxially grow copper oxide nanowires (NWs) on copper substrates using single step atmospheric pressure plasma jet assisted oxidation. NWs of average length 300 nm are grown rapidly in 5 minutes along with transforming the surface to superhydrophilic. This method introduces defects in the nanowire structure which is otherwise difficult to achieve due to the highly isotropic nature of nanowire growth. High resolution transmission electron microscopy reveals vacancies and structural defects such as lattice twinning and kinks. Theoretical investigations using density functional theory calculations indicated that oxygen vacancies reduces the adsorption energy of methanol molecules onto the CuO (111) surface and shifts the Fermi level towards conduction band. During electrocatalysis, these defect-rich nanowires exhibit twice the catalytic activity toward oxygen evolution reaction (OER) and methanol oxidation reaction (MOR) in comparison to the traditionally thermally grown nanowires. Moreover, retreating the electrodes after each stability test drops the contact resistance similar to the prisitine sample. Additionally, these NW photocathodes demonstrate an exceptional photocurrent of 2.2 mAcm–2 and have an excellent degradation activity towards organic pollutants namely phenol and paracetamol. This facile growth method can be used to engineer nanowires of other transition metals with enhanced activities. |
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Improvement of polymer properties for powder bed fusion by combining in situ PECVD nanoparticle synthesis and dry coating |
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Juan S. Gómez Bonilla, Björn Düsenberg, Franz Lanyi, Patrik Schmuki, Dirk W. Schubert, Jochen Schmidt, Wolfgang Peukert, Andreas Bück |
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Germany |
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https://doi.org/10.1002/ppap.202000247 |
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Polypropylene (PP) powders are coated with silica nanoparticles in a fluidized bed to improve the flow behavior of the powders and the processability in powder bed fusion. The nanoparticles are produced in situ via dusty plasma-enhanced chemical vapor deposition (PECVD) in an atmospheric-pressure Ar/O2 plasma jet fixed at the distributor plate of the fluidized bed. Hexamethyldisiloxane is used as a precursor of the nanoparticles. The influence of the oxygen concentration in the plasma gas and the number of treatment cycles on the chemical composition of the nanoparticles, the amount of nanoparticles deposited, and the flow properties of the coated PP powders is investigated. The chemical composition of the formed silica particles is determined by X-ray photon spectroscopy and infrared spectroscopy. The results reveal that the composition of the nanoparticles is SiOxCy, that is, the portion of organic residues introduced by the precursor can be controlled by changing the oxygen concentration in the plasma gas. The mass of nanoparticles deposited on the polymer powder's surface, as determined by inductively coupled optical emission spectroscopy, shows a linear dependence of the number of cycles and the oxygen concentration in the plasma gas. A considerable improvement of the flow behavior of the PP powders is observed after PECVD treatment. |
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Plasma-activated medium induces apoptosis in chemotherapy-resistant ovarian cancer cells: High selectivity and synergy with carboplatin |
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Milad Rasouli, Hassan Mehdian, Kamal Hajisharifi, Elaheh Amini, Kostya (Ken) Ostrikov, Eric Robert |
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Iran, Australia, France |
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https://doi.org/10.1002/ppap.202100074 |
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In the present study, A2780 CP and SKOV-3 cells, relevant to ovarian cancer and granulosa cells, as normal ovarian cells, were evaluated through cold atmospheric plasma (CAP) directly, indirectly, and by a concomitant modality of plasma-activated medium (PAM) with common drugs to overcome chemotherapy resistance in ovarian cancer. Our results confirm the high potential of PAM in comparison to common drugs and CAP for the selected cell lines, and the selectivity mechanism was related to the pH and concentration of H2O2, NO2−, and NO3− reactive species in the plasma-treated medium. Our data confirm that PAM alone and in combination with carboplatin sensitizes cancer cells to carboplatin, inhibits the SOD1 gene, and selectively induces apoptosis accompanied by high expression of p53, bax, and activation of caspase-3. |
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An investigation of plasma-driven decomposition of per- and polyfluoroalkyl substances (PFAS) in raw contaminated ground water |
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Joseph R. Groele, Nathaniel Sculley, Terese M. Olson, John E. Foster |
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USA |
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https://doi.org/10.1063/5.0039264 |
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Per- and polyfluoroalkyl substances (PFAS) are contaminants of emerging concern owing to their ability to bioaccumulate in the body and subsequently cause cancer. PFAS, while recalcitrant to advanced oxidation, can be degraded by plasma action. In this work, we investigate the efficacy of two plasma reactors on degrading PFAS in ground water derived from two different contaminated sites. The reactors included an array of underwater plasma jets and a dielectric barrier discharge (DBD) with water dielectric barriers. While both reactors showed effectiveness in removing PFAS, the DBD with water barriers was most efficient with regard to the rate of degradation and power consumed. This better performance was attributed to the increased plasma–liquid contact area. Experiments indicate that air is a suitable working gas alternative to argon, and both AC and ns-pulsed power sources can generate the plasmas for these reactors. Furthermore, it was found that for both reactors, the removal rate for low and high PFAS concentration in ground water was the same, suggesting that the reactors are most efficient at treating heavily contaminated water. In this respect, a concentration step followed by plasma treatment may be a cost-effective means to treat the PFAS-contaminated water. |
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