Literatursammlung zu Atmosphärischen Plasmen


Literatursammlung Atmosphärische Plasmen - Jahr 2022

Surface modification of polylactic acid by ion, electron beams and low-temperature plasma: a review
O. A. Laput, I. V. Vasenina, V. V. Botvin, I. A. Kurzina
Journal of Materials Science, volume  57, pages 2335–2361 (2022)
We review the work that has been done on the modification of polylactic acid by irradiation methods including low-temperature plasma treatment, electron-beam irradiation, and ion implantation. The main features of the synthesis and properties of polylactic acid are described. We summarize the technical equipment used for surface treatment of polylactic acid, and changes in the chemical structure and functional properties are induced in this way. The research results of the physicochemical, mechanical and biological properties of polylactic acid modified by high-energy methods are presented.
Spark plasma sintering assisted rapid growth of titanium boride layers on titanium: Microstructures and growth kinetics
Hanlin Zhang, Faming Zhang, Li Fu, Qifa Wan
To increase the surface hardness of titanium (Ti), the boride layers composed of TiB2 and TiB, were prepared on the CP-Ti substrate by spark plasma sintering (SPS) technique with micro-TiB2 powders as boride source. Effects of sintering temperature and holding time on the microstructure, thickness, growth kinetic and hardness of boride layers were investigated. Experimental results showed that the boride layers were composed of a continuous TiB2 top-layer and a TiB nano-whisker sub-layer. The maximum thickness of boride layers of TiB2 and TiB were 2.24 ± 0.49 μm and 15.63 ± 6.97 μm, respectively. The activation energy of boron atom for the SPS boride process was calculated to be 386.49 kJmol−1 for the TiB2 layer and 343.57 kJmol−1 for the TiB layer, which indicates that the SPS can provide enough energy that required in the surface treatment. Boride layers can grow well at a vacuum level of 6 Pa in the SPS. The borided Ti is about six times the hardness of the pure Ti. Boron atoms in the TiB2 powders were activated by the high temperature and plasma, then reacted with Ti to form TiB nano-whiskers. The holding time of the present method was significantly shorter than other boriding processes. This SPS process provides a new approach for boriding of Ti and its alloys.
A zinc-doped coating prepared on the magnesium alloy by plasma electrolytic oxidation for corrosion protection
Chao Yang, Hu Cai, Suihan Cui, Jian Huang, Jiayu Zhu, Zhongcan Wu, Zhengyong Ma, Ricky K.Y. Fu, Liyuan Sheng, Xiubo Tian, Paul K. Chu, Zhongzhen Wu
Corrosion protection of magnesium alloys is a challenge in industrial applications because of the high chemical reactivity of Mg. In this work, a coating is prepared by plasma electrolytic oxidation (PEO) on the AZ31B Mg alloy and then modified by insoluble zinc phosphate to improve the corrosion resistance. To avoid the influence of the weak acidic Zn-containing electrolyte on the formation of the passivation layer on the magnesium alloy, a two-step process is designed to first produce a passivation layer before introduction of zinc phosphate. Zinc phosphate is mainly distributed on the surface and the sidewalls of the holes in the porous coating and blocks the interactions between the corrosive solution and Mg substrate. The corrosion potential of the optimal coating (Zn-15) increase while the passive current density at the terminal potential decreases, suggesting the significantly improved corrosion resistance compared to the pristine AZ31B. The life time demonstrated by neutral salt spraying is 4200 h that is about 3 times longer than that observed from the Mg alloy with the undoped coating.
Enhanced tribological performance of cylinder liners made of cast aluminum alloy with high silicon content through plasma electrolytic oxidation
S.A. Alves, P. Fernández-Lopéz, A. Lopéz-Ortega, X. Fernández, I. Quintana, J.T. San-José, R. Bayón
Aluminum-silicon (Al-Si) alloys have been increasingly used in several industries to develop novel lighter and high-performance components. Nevertheless, these novel advanced materials display poor wear resistance which hamper their application in several critical tribological components. This investigation is focused on the surface modification of Al-Si alloys with high Si content, through a breakthrough green coating technology named plasma electrolytic oxidation (PEO). The main aim is, for the first time, to study the tribological behavior of PEO-treated cylinder liners made of cast Al with high Si content, in a configuration mimicking the real contact between a cylinder liner and a piston ring. Additionally, this study is based on the development of a novel electrolyte especially designed to generate PEO films with improved tribological properties.
Novel films were successfully synthesized by PEO in an innovative aluminate-based electrolyte. The morphological, topographical, and chemical features of the films were assessed through scanning electron microscopy (SEM), thickness and average roughness (Ra) measurements, energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). Cross-sectional SEM images showed that PEO films developed in the novel electrolyte are denser and thicker. Additionally, the novel PEO-treated cylinder liners, presented a significantly improved resistance to wear damage when submitted to tribological actions simulating the cylinder liner/piston ring real contact movements, which was linked with the extremely higher hardness of the films. These cylinder liners presented a lower COF compared to the commercial reference, along the whole duration of sliding. Finally, tribological tests showed that PEO-treated Al cylinder liners displayed a similar level of mechanical wear damage that steel cylinder liners.
The results presented in this investigation envisage the feasibility of PEO to be applied on Al-Si engine components submitted to aggressive tribological conditions, enhancing their durability requirements to levels similar to components made of steel.
Performance analysis of plasma spray Ni60CuMo coatings on a ZL109 via a back propagation neural network model
Bing-yuan Han, Wen-wen Xu, Ke-bing Zhou, Heng-yi Zhang, Wei-ning Lei, Meng-qi Cong, Wie Du, Jia-jie Chu, Sheng Zhu
Plasma spray coating properties frequently depend -to a great extent- on the spray parameters. However, it is difficult to analyze and obtain a comprehensive model of the entire plasma spray process due to the complex chemical and thermodynamic reactions that take place during the process. In this study, Ni60CuMo coatings were prepared on ZL109 substrates. A Back Propagation (BP) Neural Network model in the artificial neural network was used to predict the change in bonding strength, microhardness, and porosity of the coatings under different spraying distances, spraying powers, and powder feeding rates. The results show that the R-value of the trained network training is 0.8828. Comparison of experimental and predicted results reveals that both show similar trends, which verifies that the BP model can effectively predict the properties of Ni-based coatings.
The influence of the plasma-nitriding temperature on the microstructure evolution and surface properties of additive-manufactured 18Ni300 maraging steel
Matjaž Godec, Francisco Ruiz-Zepeda, Bojan Podgornik, Črtomir Donik, Aleksandra Kocijan, Danijela A. Skobir Balantič
• A higher nitriding temperature increases the amount of austenite and causes cracks.
• During nitriding, the austenite on the surface transforms to Fe4N and TiN.
• Cracks are related to segregations and transformations of the austenite to nitrides.
• A higher wear resistance is obtained at higher nitriding temperatures.
• A corrosion enhancement is seen at lower nitriding temperatures.
Maraging steel grade18Ni300 produced by powder bed fusion (PBF) in its as built condition was plasma nitrided at three different temperatures. The aim of the work was to investigate the impact of the nitriding temperature on the microstructural changes as well as on the surface properties such as hardness, wear and corrosion resistance. The microstructural features in the bulk as well as in the nitride layer were investigated using electron-backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-Ray diffraction (XRD) analysis. The bulk microstructure consists of martensite with a small amount of retained austenite, the amount of which increases with a higher nitriding temperature. The nitriding process also causes the formation of precipitates and can therefore also act as an aging treatment. A specific lamellar structure occurs on the surface during the nitriding process, which in the majority of cases consists of the Fe4N phase. The retained austenite also transforms during nitriding to the nitride phase Fe4N. It was found that nitriding at higher temperatures leads to the formation of cracks in the nitride layer. The crack formation is related to nano and micro segregation during the LPBF. These segregations lead to austenite formation, which also takes place along the grain boundaries and transforms during nitriding to Fe4N. Higher nitriding temperatures lead to a thicker nitride compound layer and to better wear resistance. The impact of the cracks on the static mechanical properties is negligible. However, the corrosion resistance is governed by the formation of cracks at higher nitriding temperatures.
Keywords: Maraging steel, Powder bed fusion, Plasma nitriding, Microstructure, Wear resistance, Corrosion resistance
Corrosion and wear performance of La2O3 doped plasma electrolytic oxidation coating on pure Mg
Jiaping Han, Yucheng Yu, Junjie Yang, Lu Xiaopeng, Carsten Blawert, Mikhail L. Zheludkevich
China, Germany
With the aim of improving the corrosion and wear resistance of pure magnesium, La2O3 nano-particles are added into the PEO electrolyte. The influence of the particles on coating formation, morphology and performance is investigated. Results indicate that the porosity and thickness decrease remarkably after the particle incorporation which influences the corrosion and wear resistance in return. The coating with 1 g particle addition shows lowest porosity and highest hardness value, resulting in superior corrosion and wear performance, which implies the feasibility of the proposed strategy in fabricating functionalized PEO coatings on Mg-based materials.
Investigation into the formation of Ni splats plasma-sprayed on to mild steel and stainless steel substrates
Musharaf Abbas, Arslan Khalid, Gregory M. Smith, Paul R. Munroe
Australia, USA
The present study investigates the splat formation behaviour of Ni particles plasma sprayed onto AISI 1008 mild steel and 316 austenitic stainless steel substrates to draw a comparative analysis of splat formation on both surfaces. A range of analytical techniques were used to analyse the surface and cross-sectional characteristics of the splats formed on both substrates. Most of the splats observed on both of the substrates were halo type splats driven by Rayleigh–Taylor instabilities. A linear relationship was identified between the size of the central core of the splats and their outer ring of debris, which was distinct for each substrate. The diffusion profile, obtained through STEM-EDS analysis, revealed a higher degree of diffusion across the interface between splat and stainless steel substrate as compared to mild steel, suggesting a better bond efficiency for stainless steel. Cross-sectional observations, together with theoretical calculations, showed evidence of substrate melting as well as the presence of metallurgical bonds for both mild steel and stainless steel substrates.
Amine functionalization of carbon nanotubes with solid urea using different plasma treatments
Teresa Tromm Steffen, Luis César Fontana, Peter Hammer, Daniela Becker
• Amine functionalization of carbon nanotubes through plasma using solid-phase urea.
• Incorporation of 0.8 at.% of O and 0.5 at.% of N in 1 min of 100 W plasma treatment.
• Achievement of micro-arc discharge by generating micro holes on TiO2 coated electrode.
• Complete water removal from carbon nanotubes through high-density plasma treatment.
Carbon nanotubes (CNTs) were amine-functionalized through treatments in inductively coupled post-discharge, capacitively coupled micro spark and pulsed micro arc/glow discharge plasma regions, using urea in solid state as functionalization agent. In each plasma mode, the CNT functionalization yield was evaluated according to the variation of the plasma power and treatment time. For that, the samples were characterized through Fourier-transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The results show that, while preserving the integrity of the CNTs, an 80 % increase in oxygen content and up to 1.2 at.% of nitrogen was achieved using an asymmetric bipolar plasma power supply (ABiPPS). The adsorbed water can be completely removed from the CNTs through both a high-plasma-density treatment and a methanol washing procedure, conducted before sample characterization to remove any unreacted urea.
Keywords: Carbon nanotube, Plasma, Urea, Functionalization
On the growth of functionally graded self-lubricating layer during a plasma-assisted thermochemical treatment of M50NiL steel
Jiawei Yao, Fuyao Yan, Ying Yang, Hongtao Chen, Baofeng Chen, Lei Zhu, Bangzhuan Long, Mufu Yan, Yanxiang Zhang
• A novel self-lubricating layer was fabricated on M50NiL steel through a plasma-assisted thermochemical treatment.
• The DLC structure is anchored in the pre-nitrided layer by carbide/nitride.
• That layer shows excellent adhesion strength, wear resistance, and low friction coefficient.
• The relation between Fe5C2 crystal facet and growth of DLC is investigated by first-principle calculation.
• The thermodynamic calculation reveals the formation mechanism of the graded layer.
Diamond-like carbon (DLC) with excellent mechanical properties has aroused great interest. However, the weak adhesion between the DLC film and steel substrate restricts its application. Considering that the addition of interlayers needs cumbersome steps, fabricating a functionally graded self-lubricating layer through one-step remains a challenge. We reported a novel integrated self-lubricating layer, inspired by the gradient structure formed during the traditional thermochemical treatment. That integrated layer from DLC structure gradual transition to nitrided diffusion layer is in-situ fabricated on the M50NiL steel through a plasma-assisted thermochemical treatment. The gradient structure possesses excellent wear resistance due to the self-lubricating of the DLC structure and provides sufficient adhesion strength. A deep insight into the relation between Fe5C2 crystal facet and growth of DLC is conducted by first-principle calculation and find low Miller Index of Fe5C2 facets are favorable for the growth of DLC. The thermodynamic calculation reveals that gradient structure formation is the collaboration effect of non-equilibrium and equilibrium processes.
Keywords: diamond-like carbon, Thermochemical treatment, Self-lubricating, First-principle calculation, Thermodynamic calculation
Low temperature growth of semi-polar InN (1011) on non-crystalline substrate by plasma-assisted laser ablation technique
Sandip Hinge, Tahir Rajgoli, Tushar Sant, Vaibhav Kadam, Kashinath Bogle, Suhas M. Jejurikar
• Low-temperature growth of InN (1011) on non crystalline substrate i.e. quartz.
• The growth is demonstrated using the plasma-assisted laser ablation technique which is user friendly, economic and has a fast growth rate.
• The precise control overgrowth of the planar 2D nanostructures to 3D multifaceted nanocrystals of InN is reported by varying growth by a factor of 100 °C only.
• The temperature dependent growth of InN reported herewith is observed to govern by the Wulff principle.
• Semi-polar i.e. (1011) growth of InN low-cost non-crystalline substrates can be the choice towards the production of next-generation electronic devices.
We report low-temperature growth of semipolar (1011) InN films on a non-crystalline substrate (quartz) using a novel route i.e. plasma-assisted laser ablation technique. The structural, morphological, optical, electrical and chemical/elemental environment of these films was investigated using respective techniques. Dramatic changes associated with the surface morphology of these films/ nanostructures are observed to depend on the growth temperature which is changed only by the difference of 100 °C. These changes are mainly the transformation from a continuous planar 2D nanostructured film (deposited at RT) to 3D faceted nanostructured film (deposited at 300 °C). Observed changes/transformations are attributed to the surface diffusion processes, which are temperature-dependent. These structural transformations are observed to affect the optical as well as electrical properties of the films.
Keywords: III-Nitride films, InN, Plasma, Pulsed laser ablation
Functional plasma-polymerized hydrogel coatings for electrochemical biosensing
Monique Levien, Zdeněk Farka, Matěj Pastucha, Petr Skládal, Zahra Nasri, Klaus-Dieter Weltmann, Katja Fricke
Germany, Czech Republic
• Plasma-polymerized HEMA:DEAEMA hydrogels deposited on gold electrodes.
• Glucose oxidase and acetylcholin esterase immobilized on hydrogel films.
• HEMA:DEAEMA mixture ratios influence the current response towards the substrates.
• The higher the DEAEMA portion in the hydrogel, the higher the current response.
• Plasma-polymerized hydrogel films are suitable as functional layers for biosensing.
Acrylate-based hydrogels with multifunctional properties have proven to be suitable candidates for the development of sensor systems. They gained popularity especially in combination with bioelectronics, as there is a need to understand and control the interactions of bionic devices with the human body and other environments. In this study, we present results on the biointeraction capability of plasma-polymerized (pp) hydrogels made of hydroxyethyl methacrylate (HEMA) and 2-(diethylamino)ethyl methacrylate (DEAEMA) mixtures on gold screen-printed electrodes (SPE). The hydrogels were generated by an atmospheric pressure plasma jet, and their chemical composition was characterized via FT-IR. The FT-IR analysis revealed several functional groups suitable for biomolecule immobilization, whereas the amount of -C-N, –OH, and -C-O-C groups differs depending on the mixture ratios. The pp HEMA:DEAEMA (HD) hydrogel coatings provide alternative interfacing materials for electrochemical biosensing. The enzymes glucose oxidase (GOx) and acetylcholinesterase (AChE) were coupled to the hydrogel-based surfaces, and the effects of the mixture ratios on the biomolecule immobilization were investigated. It is possible to address different functional groups of the mixtures with different immobilization strategies; thus, the sensor response can be optimized. Finally, glucose as GOx substrate and eserine as AChE inhibitor were detected by amperometry to demonstrate the practical biosensing applicability of the coatings.
Keywords: Hydrogel coating, Functional surface, Atmospheric pressure plasma, polymerization, Electrochemical biosensor, Amperometry, Glucose oxidase, Acetylcholinesterase
Highly impermeable Al2O3 moisture barriers prepared by multiple plasma oxidation of discontinuous aluminum layers for optoelectronic devices
Geumhyuck Bang, Dooho Cho
Republic of Korea
We designed a method to fabricate highly transparent (optical loss < 0.5%), moisture-impermeable high-density Al2O3 moisture-barrier layers using a multiple oxidation process (MOP) of partially coated Al layers. The effectiveness of the moisture barrier was evaluated by measuring the variations in sheet resistance of underlying Cu layers as a function of time at a fixed temperature of 85 °C and a relative humidity of 85%. No resistance variations were observed with the 5-nm-thick Al2O3 layer formed by the proposed method, whereas a considerable resistance increase was displayed by the Al2O3 layer of equal thickness prepared following the conventional deposition methods such as sputtering an elemental Al2O3 target and reactive sputtering. We formed the MOP-Al2O3 layers on a ZnO/Cu/ZnO transparent heater, which validated the improved visible transparency as well as the excellent heater stability at temperatures beyond 100 °C.
Keywords: Plasma oxidation, Anti-corrosion layer, Aluminum oxide, Optoelectronic devices
Precipitation of bone-like apatite on plasma electrolytic oxidized Ti-6Al-4V alloy
Byeong-Seok Lim, Sang-Gyu Lim, Han-Cheol Choe
Republic of Korea
• Plasma electrolytic oxidation (PEO) of Ti-6Al-4V alloy in ion containing electrolytes.
• Mn-precipitates formed on PEO surface in bioactive ion solution.
• Bone-like apatite formed in simulated body fluid at pores of the PEO-treated surface.
• Apatite nuclei that formed in pores coalesced and grew into large precipitates.
• Bioactive elements, including Mn, were detected on the surface.
In this study, precipitation phenomena of bone-like apatite on plasma electrolytic oxidation (PEO)-treated Ti-6Al-4V alloys with various electrolyte compositions were studied by using various characterization techniques. A Ti-6Al-4V disk was used as a sample for the PEO treatment, which was performed using pulsed DC power for 3 min at 280 V in an electrolyte solution containing calcium acetate, calcium glycerophosphate, manganese(II) acetate tetrahydrate, magnesium acetate tetrahydrate, strontium acetate hemihydrate, zinc acetate dehydrate, and sodium metasilicate at 25 °C. The PEO-treated samples were immersed in a simulated body fluid (SBF) solution for 24 h to investigate their bioactivity. The surface morphology, composition, and microstructure of these samples were observed by field emission scanning electron microscopy, energy dispersive X-ray spectrometry, and X-ray diffractometry.
The surface of the PEO-treated alloy in the electrolyte containing Ca, P, Mn, Sr, Zn, Mg, and Si ions was covered with precipitates that formed a ring pattern around the pores. Furthermore, Mn was detected in the pores rather than on the surface; this Mn played a role in MnO2 and Mn2O3 formation on the PEO-treated alloy surface. Moreover, on the surface treated in SBF solution after PEO treatment in the electrolyte containing Ca, P, Mn, Sr, Zn, Mg, and Si ions, apatite nucleation occurred in the pores, which coalesced and grew into large precipitates. Fewer number of functional elements, including Mn, were detected on the surface when apatite was precipitated, than that in the case of the non-treated surface in the SBF solution.
Keywords: Titanium alloy, Plasma electrolytic oxidation, Functional elements, Bone-like apatite precipitation
Electrochemical characteristics of Sr/Si-doped hydroxyapatite coating on the Ti alloy surface via plasma electrolytic oxidation
Ji-Min Yu, Hye-Ri Cho, Han-Cheol Choe
Republic of Korea
• Number of pores increased in the plasma electrolyte oxidation (PEO) as sr ions increased.
• The pore size decreased in the PEO process as Sr concentration increased.
• In the case of Si and Sr addition to electrolyte, corrosion potential was apparently increased.
• Polarization resistances of PEO-treated Sr and Sr/Si specimens showed the higher compared to bulk.
The purpose of this study is to investigate the electrochemical characteristics of Sr/Si-doped hydroxyapatite coating on the Ti-6Al-4V alloy surface via plasma electrolytic oxidation(PEO).
Ti-6Al-4V alloy of extra low interstitial grade disk was used as the anode and the carbon rod was used as the cathode. PEO treatment was carried out using pulsed DC power at 280 V for 3 min. The electrolyte used for PEO was prepared by mixing Ca(CH3COO)2•H2O, C3H7NaCaO6P, Sr(CH3COO)2•0.5H2O, and Na2SiO3•9H2O. The potentiodynamic polarization test were performed by potentiostat in a 0.9% NaCl solution at 36.5 ± 1°C. Electrochemical impedance tests were carried out using potentiostat at the open circuit potential in a 0.9% NaCl solution at 36.5 ± 1°C. The PEO-treated surface and corrosion morphology were investigated by field mission scanning microscopy and energy dispersive X-ray spectroscopy.
The number of pores increase and average size of the pores decreased as Sr increase, and area occupied by pore was decreased. In the case of Si and Sr addition to electrolyte, corrosion potential was apparently increased compared to specimen of Sr addition to electrolyte. Polarization resistances of PEO-treated Sr and Sr/Si specimens showed the higher than those of Bulk and CaP specimens from data of electrochemical impedance test.
Keywords: Plasma electrolytic oxidation, Strontium, Silicon, Hydroxyapatite, Potentiodynamic test, AC impedance
Antimicrobial and Anticancer Efficacy of Atmospheric Pressure Cold Plasma Technology
Hom Bahadur Baniya, Sudip Panday, Pabitra Khadka, Anusuya Nepal, Rajesh Prakash Guragain, Gobinda Prasad Panta, Santosh Dhungana, Bhupal Govinda Shrestha, Deepak Prasad Subedi
The present work evaluated the inactivation efficiency of atmospheric pressure cold plasma (APCP) against three pathogenic microorganisms. We have successfully developed a plasma device that can 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 jets 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 anticancer tool. Atmospheric pressure cold plasma technology has the efficacy to show anticancer properties with the treatment of cancer cells. To demonstrate the anticancer properties of APCP generated at a 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.
Keywords: atmospheric pressure cold plasma, MTT assay, HeLa cells, HEK 293, DMEM media, Antimicrobial and anticancer efficacy of cold plasma, Shigella Flexneri, Escherichia coli, Klebsiella pneumoniae
Process and electrolyte effects on the nitrogen-doped anodic plasma electrolytic saturation coating electrochemical performance: Simultaneous participation of the applied and breakdown voltages
Nazanin Shakiba, Seyed Mohammad Mousavi Khoei
Anodic plasma electrolytic saturation (APES) is an eco-friendly method to deposit a composite coating for improving the performance of metal substrates. This study had investigated the corrosion behaviour of the nitrogen-doped Al2O3 layers deposited in alkaline-nitrite electrolytes at constant VAPES of 500 and 450 V. The results indicated that the coatings prepared at a lower VAPES had higher macro and microscopic qualities and electrochemical resistance than the higher VAPES. At the VAPES = 500 V, the best APES coating just had electrochemical resistance with 1.030 MΩ.cm2 values after 48 h of immersion in the 3.5 wt% sodium chloride medium. Based on this study's results, the vital ∆V parameter is the coating driving force that depends on changes in the breakdown voltage (VB.D.) and applied voltage value (VAPEP). This participation dependent parameter (∆V) significantly affects the macro and micro-quality of this nitrogen-doped composite coating and its corrosion behaviour. The APES coating deposited at a lower NaNO2 amount (1 g/L) and VAPEP of 450 V had the highest spinel and cubic nitrogenous phases and more closed pores than the best layer deposited at 500 V due to removing KOH and decreasing VAPEP and consequently declining the participation dependent parameter (∆V) value. Accordingly, this nitrogen-doped APEP coating with the best chemical-physical properties experienced the remarkably highest electrochemical resistance with the 353.500 MΩ.cm2 value compared to all studied samples and uncoated aluminium substrate after 48 h immersion time.
Amorphous coatings on tantalum formed by plasma electrolytic oxidation in aluminate electrolyte and high temperature crystallization treatment
Jiahui Lv, Yingliang Cheng
In this paper, amorphous coatings on tantalum obtained by plasma electrolytic oxidation (PEO) in alkaline sodium aluminate electrolyte (2–10 g/l NaAlO2 + 2 g/l KOH) are investigated. It was found that the amorphous component of the oxide coatings increased with NaAlO2 concentration in the electrolyte. The coatings obtained in the electrolyte of 10 g/l NaAlO2 + 2 g/l KOH are completely amorphous. Subsequently, the amorphous coatings were subjected to vacuum heat treatment at 600, 800, 900 and 1300 °C to study their crystallization behavior. The results show that crystallization does not occur at 600 °C. However, crystallization occurred partially at 800 °C and completed at 1300 °C, with orthorhombic AlTaO4 as the main phase structure. Nanoindentation tests show that hardness of the coating at dense regions increases after crystallization, but defects and cracks in the coating are also increased after heat treatment. The amorphous coatings have excellent corrosion resistance, but the defects generated in the crystallized coatings are detrimental to the corrosion performance. The reason for the formation of amorphous coatings may be derived from rapid cooling and the glass-forming ability of the binary system of Ta2O5 and Al2O3.
Bi2MoO6 and Ag nanoparticles immobilized on textile by plasma-derived innovative techniques to generate antimicrobial activity
Deyu Wang, Kun Li, Cong Zhou, Lei lei, Yoann de Rancourt de Mimérand, Xiaoyun Jin, Jia Guo
• Cotton fiber textile was modified using cold plasma discharge.
• Bi2MoO6 microflowers and AgNPs were successfully immobilized using three different techniques based on CPD.
• The textile composite was tested with two bacteria: E. coli and S. Aureus.
• Significant antimicrobial activity was observed with the two strains, both in dark conditions and under low-intensity visible light.
In this study, we expose various techniques based on cold plasma discharge (CPD), and more precisely aqueous-phase plasma-aided grafting (APPAG), to efficiently modify the surface of polymers as well as fabric made of natural fibers. Several directions were investigated to ultimately add a functional coating providing an antimicrobial effect to textiles. Our strategy relies on the immobilization of silver nanoparticles (AgNPs) and Bi2MoO6 (BMO) – a robust inorganic photocatalyst that can be activated by visible light – microflowers, at the surface of cotton fabric fibers. Notably, an in situ complexation-assisted precipitation route (ISCAP – an original method derived from CPD) was successfully employed to generate a very uniform coating of silver nanoparticles at the surface of organic substrates. As we demonstrate in this study, the surface functionalization with BMO and silver provides a significant protection against bacteria in dark conditions, through a bacteriostatic effect of nano silver, and under low-intensity artificial visible light (thanks to the photocatalytic effect of BMO/Ag), hence suitable for an indoor environment such as hospitals. Our composite nanomaterial, cotton/BMO/AgNPs, was assessed through antibacterial testing with Escherichia coli (E. coli) and Staphylococcus aureus (S. Aureus), showing a pronounced antimicrobial effect with both strains. This study opens prospects for the functionalization of natural or artificial fiber materials with possible applications in the field of biomedical protective equipment such as bandages, masks or technical cloths; or even photocatalysis.
Keywords: Cold plasma discharge, Textile, Bi2MoO6, AgNPs, Photocatalyst, Antimicrobial
Role of the nitrogen ratio on mechanical properties and wear resistance of CrN/Fe functionally graded coating produced by double glow plasma alloying
Yan Qia, Wenping Liang, Qiang Miao, Jinwei Yi, Hao Lin, Yangyang Liu, Hairui Ma
• Fabrication of CrN/Fe functionally graded coating using double glow plasma alloying.
• CrN/Fe FGCs owned a gradually transited structure of CrN ceramic phase and (Fe, Cr) ductile metal phase.
• Gradient structure relieved the stress concentration, and enhanced the toughness and wear resistance of coating.
The hard ceramic coating under the external load tends to show cracking and spallation due to the mismatch of deformation between coating and substrate. To moderate the property difference, a CrN/Fe gradient coating was fabricated by double glow plasma alloying at different Ar/N2 ratios. The thermodynamically favorable reaction between Cr and N ensured the spatially gradient structure of CrN and (Fe, Cr) phase without Fe nitrides. The outmost CrN phase possessed over-stoichiometry of N atoms, leading to the N1s spectrum shifted to the lower binding energy. The increased N2 ratio made the nitride content increase from 53.4, 73.6 to 74.0 %. Various volume gradients of nitride/metal contributed to different mechanical behavior of coatings, such as the enhanced hardness (16.3 to 21.5 GPa) and Young’s Modulus. Two indexes, H/E and H3/E2, showed an increasing trend with the increasing N2, which meant better toughness and adequate elastic abilities to suppress radial cracks. Compressive residual stress in these coating ranging from −1.06, −1.16 to −1.44 GPa, also restrained the radial cracks and accelerated the formation of circumferential cracks. Introducing nitride-metal transitional structure lowered the probability of cracks and spallation in the wear test.
Keywords: CrN/Fe gradient coating, N2 flux ratio, Toughness, Wear-resistance
Influence of plasma beam polishing process parameters on surface roughness of AISI 304 stainless steel
Tiantian Deng, Jianjun Li, Zhizhen Zheng, Wie Tian, Guoliang Li
• Methods to control the surface roughness during polishing process are analyzed.
• Autocorrelation function of the polished surface is investigated.
• Areal roughness  can be reduced to 0.81  0.01 μm from 8.67  0.12 μm.
• Possible changes of chemical composition and nano-hardness are discussed.
Industrial products used in medical equipment and food manufacture are usually made from AISI 304 and place great demands on surface polishing. The application of plasma beam in the field of energy beam polishing is a new technology to obtain a desired level of surface roughness. Therefore, this paper details an investigation conducted to focus on the effect of process parameters on the surface morphology of AISI 304 stainless steel during plasma beam polishing. The main arc current, nozzle height, scanning speed and plasma gas flux that have the greatest influence on the arc plasma characteristics and energy input values are considered to be the key experimental parameters. While the measured roughness values and their intensity autocorrelation functions are applied to evaluate the polished surfaces. The capacity of plasma beam polishing to produce glossy and defect-free surfaces on AISI 304 has been successfully verified. Under the specific combination of main arc current, nozzle height and scanning speed, the energy input could reach approx. 90 J/mm ~ 110 J/mm, corresponding to the more than 85.9% fall in areal roughness Sa. Although the plasma gas flux had no discernible impact on the energy input, it was observed that the surface uniformity varied from 0.81 +/- 0.01 μm Sa  to 1.04 +/- 0.04 μm Sa  with the increase of plasma gas flux. Possible changes of chemical composition and nano-hardness during plasma beam polishing of AISI 304 stainless steel are analyzed.
Keywords: Plasma beam polishing, AISI 304, Process parameters, Surface roughness, Autocorrelation function, Chemical composition, Nano-hardness
Influence of ring electrodes covered with dielectric layer on the characteristics of atmospheric pressure plasma jet and its interaction with polymer surface
Tao Wang, Jiahao Wang, Shengquan Wang, Xin Wang, Weizhi Yang, Meng Li, Liping Shi
• Plasma jet with ring electrodes covered with dielectric layers (DL) was investigated.
• The addition of DL can improve the uniformity of electric field distribution.
• DL addition can reduce the current intensity and decrease the intensity of the reactive species.
• Etching morphologies of polymer films can be improved after DL addition.
• Oxygen content in the etched region decreases rapidly with the addition of DL.
Atmospheric pressure plasma jet (APPJ) with ring-ring typed electrode configuration is widely utilized in material processing and biomedical applications. In this paper, the ring electrodes covered with dielectric layer (DL) is proposed for improving its electric field distribution and controlling the plasma characteristics and its interaction with polymer film. Simulation and experiment method was used to investigate the effect of the DL addition on the characteristics of plasma jet and plasma etching of polymer film. Simulation result indicates that DL addition can not only improve the uniformity of electric field distribution, but also reduce its intensity in the tube. The experimental results show that DL addition can reduce the plasma current intensity and decrease the intensity of the reactive species. Compared with bare ring electrodes, polymer etching morphologies are greatly improved after DL addition. Besides, the oxygen content in the etched region also decreases rapidly with DL addition, and the larger the dielectric constant is, the larger the O/Si and O/C ratio is. The interaction process between APPJ and polymer film was also discussed and the improvement of electrical field distribution was considered as the main reason for the results of plasma discharges and its interaction with polymer film.
Keywords: Dielectric layer, Plasma jet, Polymer etching, Ring electrode
Achieving high anti-sintering performance of plasma-sprayed YSZ thermal barrier coatings through pore structure design
Jibo Huang, Xin Chu, Tin Yang, Huanjie Fang, Dongdong Ye, Weize Wang, Xiaofeng Zhang, Wen Sun, Renzhong Huang, Chang-Jiu Li
Sintering is one of the critical factors leading to thermal and mechanical degradation of plasma-sprayed thermal barrier coatings (TBCs) in service under high temperature. The sintering resistance of the coating is expected to be improved through pore structure design. In this study, through a strategically improved powder feeding process, 8YSZ powders with fine-sized and coarse-sized pores were injected from the tail of plasma flame during plasma spraying to design porous coatings containing two differently flattened particles with different pore structures. The microstructural and property evolutions during sintering of the coatings were systematically studied compared with traditionally structured coatings. The effect of pore morphology on its sintering behavior was analyzed by quasi-in-situ observation of microstructure evolution. Results show that the anti-sintering performance of plasma-sprayed coating can be improved by adjusting the pore structure of coating with porous unmelted particles. In particular, the introduction of unmelted particles with coarse-sized pores can ensure that the coating has excellent thermal and mechanical properties for a long time. The results of this study provide guidance for structural design of anti-sintering plasma-sprayed coatings.
Plasma electrolytic oxidation coatings on additively manufactured aluminum–silicon alloys with superior tribological performance
Lili Wang, Guowei Wang, Hui Dong, Minheng Ye, Xiaoyuan Li, Ling Liu, Jinlong Pan, Zuoyan Ye
Due to the increasing demand for lightweight structures with complex geometries, additively manufactured (AM) aluminum–silicon (Alsingle bondSi) alloys have aroused considerable attention. However, their insufficient hardness and poor tribological performance remain a critical issue for several applications requiring high contact pressures and wear resistance. Herein, current-controlled plasma electrolytic oxidation (PEO) coatings were developed on AM Alsingle bondSi alloys in alkali electrolytes. To obtain PEO coatings with excellent mechanical properties, the electrolyte system was modulated and optimized by adjusting the concentration of the silicate and hexametaphosphate. The corrosion behavior of AM Alsingle bondSi alloys in various electrolytes were evaluated via potentiodynamic polarization tests. The influence of silicate and hexametaphosphate on the structure, composition, thickness, roughness, and hardness of the prepared PEO coatings were determined using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy system, microprofilometer, and microhardness tester. The tribological behavior of the PEO coatings were tested using a ball-disc-tribometer without lubrication. Silicate benefits the PEO process under the constant current mode; however, a mass of mullite and noncrystalline materials form. Hexametaphosphate adversely affects the formation of the initial passive film on AM Alsingle bondSi alloys, and many defects form on the obtained coating. But it can decrease the roughness of the coating and accelerate the dissolution of the matrix, promoting the formation of alumina and inhibiting the formation of mullite and SiO2. The PEO coatings, prepared in the mixed electrolytes (with a concentration ratio of silicate and hexametaphosphate of ~0.7–1), have the fewest defects and highest hardness (~1300 HV), and possess superior tribological performance; the wear rates of the coatings were only ~1/150th that of the AM AlSi10Mg substrate. Both the synergy of silicate and hexametaphosphate and the modified growth mechanisms of PEO coatings on AM Alsingle bondSi alloys have been proposed.
Effect of plasma nitriding on tribological properties of nickel‑boron-nanodiamond electroless coatings
Seyyed Saber Mirhosseini, Farzad Mahboubi
This study is an effort to investigate the synergic effect of nano-diamond (ND) addition and plasma nitriding (PN) treatment on tribological and structural properties of nickel‑boron (NiB) coatings. NiB/ND nanocomposites containing different amounts of NDs (0.0, 0.1, 0.5, and 1.0 g/L) were produced in an electroless bath. Then, plasma nitriding was conducted on the samples for 1 h at 400 °C in an N2-H2 environment. To study phase analysis and examine the surface morphology of the samples, X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) were utilized. The wear behavior and friction were determined under the normal load of 10 N using the pin-on-disk method. The surface roughness, microstructure, and microhardness were also assessed. The results showed that, as the ND concentration increased, the amorphous structure of as-plated (AP) Ni-B transformed to a semi-crystalline one. Moreover, the amorphous structure of the as-deposited NiB/ND coatings changed to a crystalline one after plasma nitriding, which resulted in a higher hardness value. NiB/0.5ND coating showed the highest hardness value (1523 HV0.1) and the highest wear resistance (0.8×10−10 Kg/N.m). The smoothest wear trace with no visible cracks is related to the worn surface of PN NiB/0.5ND sample, suggesting that the NiB/ND nanocomposite can be a promising candidate for surface engineering processes.
The role of microstructural evolution during spark plasma sintering on the soft magnetic and electronic properties of a CoFe–Al2O3 soft magnetic composite
Calvin H. Belcher, Baolong Zheng, Benjamin E. MacDonald, Eric D. Langlois, Benjamin Lehman, Charles Pearce, Robert Delaney, Diran Apelian, Enrique J. Lavernia, Todd C. Monson 
For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic polarization and high electrical resistivity are needed. This work aimed at the development of a soft magnetic composite synthesized via spark plasma sintering with both high saturation magnetic polarization and high electrical resistivity for efficient soft magnetic cores. CoFe powder particles coated with an insulating layer of Al2O3 were used as feedstock material to improve the electrical resistivity while retaining high saturation magnetic polarization. By maintaining a continuous non-magnetic Al2O3 phase throughout the material, both a high saturation magnetic polarization, above 1.5 T, and high electrical resistivity, above 100 lX m, were achieved. Through microstructural characterization of samples consolidated at various temperatures, the role of microstructural evolution on the magnetic and electronic properties of the composite was elucidated. Upon consolidation at relatively high temperature, the CoFe was to found plastically deform and flow into the Al2O3 phase at the particle boundaries and this phenomenon was attributed to low resistivity in the composite. In contrast, at lower consolidation temperatures, perforation of the Al2O3 phase was not observed and a high electrical resistivity was achieved, while maintaining a high magnetic polarization, ideal for more efficient soft magnetic materials for transformers and inductors.
Formation of pure τ-phase in Mn–Al–C by fast annealing using spark plasma sintering
F. Maccari, A. Aubert, S. Ener, E. Bruder, I. Radulov, K. Skokov, O. Gutfleisch 
Mn–Al–C is intended to be one of the “gap magnets” with magnetic performance in-between ferrites and Nd-Fe-B. These magnets are based on the metastable ferromagnetic \(\tau\)-phase with L1\(_0\) structure, which requires well controlled synthesis to prevent the formation of secondary phases, detrimental for magnetic properties. Here, we investigate the formation of \(\tau\)-phase in Mn–Al–C using Spark Plasma Sintering (SPS) and compare with conventional annealing. The effect of SPS parameters (pressure and electric current) on the phase formation is also studied. Single \(\tau\)-phase is obtained for annealing 5 min at \(500~^\circ \hbox {C}\)  with SPS. In addition, we show that the initial grain size of the \(\epsilon\)-phase is influencing the \(\tau\)-phase transformation and fraction at a given annealing condition, independently of the annealing method used. A faster transformation was observed for smaller initial \(\epsilon\)-grains. The samples obtained by SPS showed comparable magnetic properties with the conventional annealed ones, reaching coercivity of 0.18 T and saturation magnetization of 114 Am\(^2\)/kg in the optimized samples. The similarity in coercivity is related to the microstructure, as we reveal the presence of structure defects like twin boundaries and dislocations in both materials.
Plasma-derived in situ complexation-assisted precipitation for the fabrication of supported Zn-doped CdS, for water depollution
Deyu Wang, Yongfu Kang, Lei Lei, Yoann de Rancourt de Mimérand, Xiaoyun Jin, Jia Guo
• An ISCAP process was used to obtain Zn-doped CdS NPs in situ on a polymer substrate.
• Supported photocatalysts with fractal supports were tested through RhB degradation.
• Supported Zn-doped CdS was found to be photostable, with good recyclability.
• PVPA, the binder, displayed a protective effect on the immobilized CdS catalyst.
In this study, we explore the potential of an innovative method based on cold plasma discharge (CPD), to fabricate stable supported photocatalysts for the photodegradation of organic water pollutants. Supported catalysts bear significant advantages compared to colloidal ones, the main benefit being that they can be separated from water and reused much more easily, which is a crucial aspect especially of nanocompounds. They can also participate in reducing catalyst loss between operations or even enable continuous-flow processes, usually more productive than batch, discontinued operations. Hereby, we describe an immobilization approach, i.e. in situ complexation-assisted precipitation (ISCAP), which allows the fabrication of nanoCdS photocatalyst, directly at the surface of a polymer substrate. More specifically, we establish the potential of this process to obtain a hybrid coating of zinc-doped CdS, in situ. Our findings revealed that the resulting supported catalyst was photoactive – degrading Rhodamine B (RhB) dye, easily recyclable and photostable thanks to the successful doping of the catalytic phase. In addition, it seems that the immobilization itself stabilized the catalyst, probably thanks to polyvinylphosphonic acid (PVPA), used as a complexing and binding agent. The catalytic phase was immobilized on a resin substrate that was fabricated by liquid crystal diode (LCD) 3D printing, and conceived using fractal-inspired geometry.
Keywords: Cold plasma discharge, Doping, Fractal, 3D printing, Immobilization
Coarse-grained approach to amorphous and anisotropic materials in kinetic Monte Carlo thin-film growth simulations: A case study of TiO2 and ZnO by plasma-enhanced chemical vapor deposition
Jorge Budagosky, Xabier García-Casas, Juan R. Sánchez-Valencia, Ángel Barranco, Ana Borrás
The growth of TiO2 and ZnO thin films is studied by means of coarse-grained kinetic Monte Carlo simulations under conditions typically encountered in plasma-enhanced chemical vapor deposition experiments. The basis of our approach is known to work well to simulate the growth of amorphous materials using cubic grids and is extended here to reproduce not only the morphological characteristics and scaling properties of amorphous TiO2 but also the growth of polycrystalline ZnO with a good approximation, including the evolution of the film texture during growth and its dependence on experimental conditions. The results of the simulations have been compared with available experimental data obtained by X-ray diffraction, analysis of the texture coefficients, atomic force microscopy, and scanning electron microscopy.
Al matrix composites reinforced by in situ synthesized graphene–Cu hybrid layers: interface control by spark plasma sintering conditions
Bowen Pu, David Mesguich, Claude Estournès, Xiang Zhang, Geoffroy Chevallier, Naiqin Zhao, Christophe Laurent
China, France
Tremendous impacts are usually made by the synthesis method and consolidation technique on microstructure and interface of graphene/Al composites. In the present work, an in situ gel-precursor decomposition route is proposed for the one-step synthesis of graphene nanosheet (GNS) decorated with Cu nanoparticles in the form of hybrid layers encapsulating Al grains (designated as GNS–Cu/Al). Consolidation is performed by spark plasma sintering (SPS) using markedly different sets of maximum temperature and maximum uniaxial pressure (400 °C/400 MPa or 500 °C/100 MPa). The powder and dense samples are investigated by several techniques including thermal analysis, X-ray diffraction and electron microscopy. The microhardness and elastic modulus of selected GNS–Cu/Al composites are investigated and related to the microstructure and preparation conditions. Results demonstrate that the interface structure is primarily determined by the roles of GNS–Cu hybrid layers and finely controlled by SPS conditions. This work paves a novel way to elucidate the evolutions of metal-decorated graphene hybrids in Al matrix composites.
High aspect ratio tilted gratings through local electric field modulation in plasma etching
Zhitian Shi, Konstantins Jefimovs, Antonino La Magna, Marco Stampanoni, Lucia Romano
Switzerland, Italy
• Controlled tilted etching in plasma thanks to local metal electric field modulators.
• Demonstrated modulated tilt as a function of position in 1D and 2D.
• High precision slanted gratings etched in silicon without substrate tilt.
• Modelling of electric field modulator with a finite element method.
The anisotropic nature of plasma etching is usually exploited to realize vertical nano-/micro- silicon structures by deep reactive ion etching. However, some applications require tilted instead of perpendicular profiles with respect to the substrate. Here, a controlled tilted etching is realized by introducing a set of metal electric field modulator(s), which modify the near sample surface potential. The ions from the plasma body are accelerated under the influence of the distorted electric field, and hit the silicon surface with a certain incident angle. A model is built with finite elements method, taking into account the geometry of the experiment and the chamber conditions during the etching process. The thickness and the inter-distance of Al slabs have been varied in a range of 0.5–3 mm and 10–25 mm, respectively. A tilt angle ranging from 0° to 22.6° has been measured and validates the simulation results, showing that a desired tilt profile can be achieved with a proper parameters tuning. Examples of 1D and 2D modulations are reported with linear and chessboard slanted gratings for X-ray imaging applications.
Keywords: Plasma etching, High aspect ratio, Tilted etching, Electric field modulation, Diffractive optics, Fan shaped gratings
Low-temperature SiO2 film coatings onto Cu particles using the polygonal barrel-plasma chemical vapor deposition method
Yuji Honda, Yukari Mikami, Mitsuhiro Inoue, Koji Shinagawa, Takayuki Abe
Japan, The Netherlands
• Low-temperature SiO2 film coatings were investigated at 100 °C using the PB-PCVD method.
• The uniform SiO2 film coatings were achieved by supplying hexamethyldisilazane and O2 at 6 and 120 ml/min, respectively.
• The film thickness can be correctly controlled by the treatment time and the RF power.
• The PB-PCVD method can be used to deposit smoother SiO2 films at a relatively high rate.
• The PB-PCVD method is a high-speed and controllable ceramic coating system.
Surface coating of Cu particles with SiO2 thin films was investigated at a low temperature of 100 °C using the polygonal barrel-plasma chemical vapor deposition (PB-PCVD) method. The Cu particles were treated at 250 W for 30 min while a hexagonal barrel containing the samples was oscillated at 5 rpm with an amplitude of ± 75°. The results show that the particle surfaces were uniformly coated with amorphous SiO2 films at the flow rates of vaporized hexamethyldisilazane (used as a precursor) and O2 gas of 6 and 120 ml/min, respectively. The thickness of the SiO2 films (77 nm) changed linearly with the treatment time and the RF power, whereas for longer treatment times (>40 min at 250 W) and higher RF powers (>300 W for 30 min), impurities were regenerated, which was prevented by inserting a barrel-cleaning process during the treatment. The deposition rate of the SiO2 films for PB-PCVD was 15 times higher than that of our original sputtering method, and the smoother films can be obtained by PB-PCVD, as compared to the sputtering method. Thus, this high-speed and controllable PB-PCVD method would be useful for ceramic coating researches such as electric device fields, although further investigations are required.
Keywords: Polygonal barrel-plasma chemical vapor deposition (PB-PCVD) system, Particle surface modification, Ceramic coating, SiO2 film, Dry process
Effect of plasma-activated acetic acid on inactivation of Salmonella
Typhimurium and quality traits on chicken meats
Taemin Kang, Donggyun Yim, Sung-Su Kim, Ki Ho Baek, Hyun-Jun Kim , Cheorun Jo
Republic of Korea
This study investigated the bactericidal effects of plasma-activated acetic acid (PAAA) on Salmonella Typhimurium and its impact on the physicochemical traits of chicken meat. Twenty milliliters of 0.8% (v/v) acetic acid (AA) was treated with plasma (2.2 kHz and 8.4 kVpp) for 30 min. The chicken skins, breasts, and drumsticks, inoculated with S. Typhimurium, were immersed in AA or PAAA and incubated for 10 min. The S. Typhimurium on the breasts and drumsticks were significantly susceptible to treatment with AA and PAAA, compared to the control group (deionized water treatment), and the population of bacterial cells in PAAA-treated chicken breasts and drumsticks decreased by 0.98 and 1.19 log CFU/g, respectively, compared with AA. The values for pH and 2-thiobarbituric acid reactive substances (TBARS) of PAAA-treated samples decreased significantly compared to the control group. The lightness (L*) values of the chicken breasts after AA and PAAA treatments increased compared to the control group, whereas the value for yellowness (b*) decreased. The scanning electron microscopic (SEM) images and the results for volatile compounds in chicken meat revealed similar patterns, with no significant differences between AA and PAAA treatments. In conclusion, we found that PAAA was more effective than AA and synergistic PAAA treatment of chicken caused to the reduction of S. Typhimurium and improve the meat quality. Therefore, PAAA could be utilized as a promising decontaminant for the chicken meat industry.
Keywords: plasma-activated acetic acid, chicken meat, Salmonella Typhimurium, bactericidal efficiency, meat quality 
Influences of the near-spherical 3D pore on failure mechanism of atmospheric plasma spraying TBCs using a macro-micro integrated model
Zhi-Yuan Wei, Xiao-Xue Dong, Hong-Neng Cai, Sheng-Dun Zhao
The near-spherical 3D pores in the thermal barrier coatings (TBCs) by atmospheric plasma spraying (APS) affect the thermal insulation and anti-spalling performance of the coating. To explore the effects of near-spherical 3D pores on the coating failure, a macro-micro integrated model is developed. The randomly distributed pores are implanted into the ceramic layer inside the micro region by the secondary development of Python program. The dynamic propagation, coalescence, or branching of cracks in the ceramic layer are achieved by embedding cohesive elements between adjacent solid elements. The effects of pore characteristic parameters: porosity, aspect ratio, and orientation angle on the crack evolution are investigated. In addition, the effect of TGO on the ceramic cracking is also examined in the porous model. The results show that the stress concentration near the near-spherical pores can induce early crack initiation. Regular spherical pores with a porosity of about 10% are more conducive to the improvement of coating life. When a large number of near-spherical 3D pores appear, TGO thickening still induces premature spallation of the coating. These results can provide important theoretical guidance for the advanced TBC system design with long lifetime.
Uniform deposition of silicon oxide film on cylindrical substrate by radially arranged plasma jet array
Ruixue Wang, Zhangchuan Xia, Xianghao Kong, Shuang Xue, Huiyan Wang
In this work, the SiOx film was deposited on a cylindrical substrate by a radially arranged plasma jet array generated by an AC power supply. The properties of deposited SiOx film were studied systematically, including surface morphology, film thickness, elemental composition and chemical structure. Besides, the effect of surface modification on insulation improvement in a gas insulated transmission line (GIL) system was verified. The discharge uniformity of the plasma jet array was improved by adding ballast resistor in the series circuit. Our results showed that the SiOx films were composed with Si-O-Si group dominated by network structure along with a small amount of Si-OH group and inorganic groups (-CH2, Si-CH3). The film deposited by plasma jet array showed good uniformity on thickness and element composition. The lift-off voltage of metal particle improved by about 120.88% after SiOx film deposition. Our results provide a universal surface modification method for cylindrical substrate under mild conditions.
A novel reverse-polarity plasma torch with extended hot-wall nozzle for atmospheric plasma spraying of dense yttria-stabilized zirconia coatings
Fangyuan Liu, Deping Yu, Yiwen Chen, Bin Duan, Jin Yao
Due to the high heating temperature and low cost, atmospheric plasma spraying (APS) has been widely used in the preparation of ceramic coatings, but its coatings are normally formed by the stacked splats from fully or partially melted feedstock particles, which inevitably leads to some pores, unbonded interfaces or cracks. Thus, in this paper, a novel atmospheric plasma spraying technique using a reverse-polarity plasma torch (RPT) with extended hot-wall nozzle was proposed to fully melt and accelerate feedstock particles for the preparation of dense YSZ ceramic coatings. Firstly, the RPT spray system was designed in detail, and its main electro-thermal characteristics were experimentally studied. The results showed that the RPT exhibited higher arc voltage, thermal efficiency and lower arc voltage fluctuation than that of traditional rod-cathode/normal-polarity plasma torches (NPT) at the similar output power. Secondly, a numerical simulate was carried out to reveal the effect of the extended hot-wall nozzle on the temperature and velocity distributions of the plasma jet. The results showed that the extended hot-wall nozzle remarkably extended the high-temperature and high-velocity region of the plasma jet from the RPT exit to the downstream. Finally, the dense and uniform YSZ coatings with a porosity of about 5.3% were successfully prepared by the RPT with extended hot-wall nozzle. The results showed that the YSZ coating exhibited denser microstructure and fewer defects than that of the coating prepared by traditional APS process. Meanwhile, the hardness and Young's modulus of the YSZ coating were 11.9 ± 1.4 GPa and 197.9 ± 29.4 GPa, respectively, which were relatively higher than that of the coating prepared by traditional APS process, and were very close to that of the coating prepared by very low-pressure plasma spraying (VLPPS) process.
Mechanical and biological properties of atmospheric plasma-sprayed carbon nanotube-reinforced tantalum pentoxide composite coatings on Ti6Al4V alloy
W.T. Lin, Z.W. Lin, T.Y. Kuo, C.S. Chien, J.W. Huang, Y.L. Chung, C.P. Chang, M.Z. Ibrahim, H.T. Lee
Taiwan, ROC, Egypt, Malaysia
Ta2O5 coatings containing 0, 3, 5 and 7 vol% multi-walled carbon nanotubes (CNTs) were deposited on Ti6Al4V substrates by atmospheric plasma spraying (APS). The addition of CNTs had no obvious effect on the surface morphology and roughness of the coatings, but increased the coating porosity. The coatings consisted primarily of β-Ta2O5 phase, a small amount of α-Ta2O5, and minor C peaks corresponding to the CNTs. As the CNT content increased, the elastic modulus (E) and indentation fracture toughness also increased. However, the higher CNT content increased the coating porosity and reduced the microhardness. Following immersion in simulated body fluid (SBF) for 14 days, the surfaces of all the coatings were completely covered with hemispherical bone-like apatite. Furthermore, after incubation in osteoblast-like osteosarcoma MG-63 cell culture for 7 days, all of the coatings showed excellent cell attachment, growth and spreading. Overall, the present results show that the addition of CNTs to Ta2O5 raw powder improves the indentation fracture toughness of the resulting coatings without degrading their biological properties.
Microstructural evolution of ceramic nanocomposites coated on 7075 Al alloy by plasma electrolytic oxidation
Nastaran Barati, Jiechao Jiang, Efstathios I. Meletis
Alumina-zirconia nanocomposite coatings were prepared on 7075 Al alloy by plasma electrolytic oxidation (PEO) at current densities 0.1–0.3 A/cm2 in a Zr-containing electrolyte under DC galvanostatic mode. Coatings were investigated by X-ray photoelectron spectroscopy (XPS), X-ray and electron diffraction, and high-resolution transmission electron microscopy (HRTEM). The coatings developed at current density higher than 0.2 A/cm2 consist of γ-, t- and α-alumina and tetragonal zirconia and were composed of four sub-layers: (i) interface nanocomposite layer close to the substrate with a dense structure of heterogeneously distributed α-Al2O3 and t-Al2O3 nanocrystals (2–5 nm in size) embedded in an amorphous matrix, followed by (ii) a pure amorphous Al2O3 sublayer, (iii) a dense zirconia encapsulated alumina sublayer and (iv) a top amorphous sublayer with dispersed globular alumina and zirconia nanoparticles. The zirconia encapsulated alumina sublayer is composed of large t-Al2O3 and γ-Al2O3 grains bordered by fine t-ZrO2 nanoparticles. The t-ZrO2 phase was nucleated in an atomically coherent manner at Al2O3 grain boundaries. The microstructure evolution in the coating revealed alumina formation at the early stages of the process while the oxidation, crystallization and incorporation of zirconia occurred at the last stages of the PEO process. The phenomenology of the PEO Al2O3/ZrO2 nanocomposite coating formation is presented to account for the present experimental observations.
Erosion performance of suspension plasma spray thermal barrier coatings — A comparison with state of art coatings
Nicholas Curry, Satyapal Mahade, Abhilash Venkat, Shrikant Joshi
Austria, Sweden, India
Suspension plasma spray (SPS) thermal barrier coatings are currently at an early stage of industrial adoption. There remain questions about the performance of SPS columnar coatings under different engine environmental conditions as it may influence which established engine coatings can be replaced by SPS coatings. One particular area of concern has been the erosion resistance of SPS coatings.
In this study a columnar SPS coating has been evaluated against three types of state of art air plasma spray coatings: conventional porous coating, high porosity coating and dense vertically cracked coating. Air-jet erosion testing was performed on coatings at a glancing angle of 30 degrees and with direct impact at 90 degrees. Coatings have been ranked according to their mass loss per unit erodent mass. Coatings were also evaluated for their microstructure, porosity content, hardness, and fracture toughness. The erosion damage created during testing has also been investigated using electron microscopy to observe the damage mechanism. The results of this study demonstrate that SPS coatings can outperform porous APS coatings in erosion resistance and could be considered a match for dense vertically cracked coatings. The SPS columnar coatings have shown a decreasing erosion rate with exposure time that suggest the influence of surface roughness on initial erosion behaviour.
Application of diffuse coplanar surface barrier plasma discharge to polymeric materials
Anwendung der diffusen Koplanar-Plasmaoberflächenentladung auf Polymerwerkstoffen
R. Janík, M. Kohutiar, M. Pajtášová, D. Ondrušová, P. Skalková, M. Eckert
Slovak Republic, Czech Republic
The KPR 200 mm plasma reactor is a device designed for the surface modification of various materials. Such a modification occurs by applying a unique type of plasma – plasma generated on a ceramic dielectric. The ceramic dielectric is a durable system with which it is possible to continuously modify the surfaces of materials with such a plasma. The advantage of applying this unique type of plasma is that the modification of the materials occurs at room temperature and atmosphere. However, it is necessary to monitor and observe certain parameters, for example: the selected power, the exposure time of the surfaces of the modified materials, and the distance of the surface from the ceramic dielectric itself. Therefore, in the present paper, the effect of diffuse coplanar surface barrier discharge (DCSBD) plasma discharge on selected polymeric materials was investigated. Plasma impact assessment was also performed using image analysis, that could provide relevant information in the process of plasma-chemical modification. Changes in the surfaces of the investigated thin polyvynil chloride material, before and after exposure to plasma discharge, were also observed (changes in contact angle, atomic force microscopy).
Effect of plasma electrolytic oxidation on the hot salt corrosion fatigue behavior of the TC17 titanium alloy
Hailan Shi, Daoxin Liu, Xiaohua Zhang, Weidong Zhao, Zhen Liu, Mengyao Li, Yuting He
In this paper, the effect of plasma electrolytic oxidation (PEO) on the hot salt corrosion fatigue (HSCF) behavior of the TC17 titanium alloy at 420°C was investigated. Through microstructure characterization and fatigue fracture analysis, combined with a comparative study of its hot salt corrosion behavior, the mechanism of PEO on HSCF behavior was also investigated. The results showed that the high-temperature fatigue resistance of the TC17 titanium alloy was significantly reduced by the deposition of 0.4 mg/cm2 of solid NaCl compared with that without a salt coating. This behavior was observed because the corrosion pits caused by hot salt corrosion promoted the initiation of fatigue cracks, and hydrogen penetration promoted the growth of fatigue cracks. However, the HSCF resistance of the TC17 alloy with the PEO ceramic coating could be effectively increased. This was because the PEO ceramic coating with high bonding strength and good compactness effectively inhibited hot salt corrosion damage and delayed the formation of the resident slip zone and hydrogen permeation, thereby inhibiting the initiation and propagation of fatigue cracks.
Nitrogen incorporation in graphene nanowalls via plasma processes: Experiments and simulations
Andrea Jagodar, Johannes Berndt, Erik von Wahl, Thomas Strunskus, Thomas Lecas, Eva Kovacevic, Pascal Brault
France, Germany
• Low temperature plasma treatment of graphene followed by analysis and simulations.
• Synchrotron XPS and NEXAFS reveal the bonding situation and confirm N incorporation.
• Molecular dynamics simulations give insight into fundamental reaction mechanisms.
• Bonding situation can be controled by kinetic energy of impinging N-species.
• Model can be applied for plasmas as well as for beam doping and functionalisation.
The interest in doped and functionalized graphene nanomaterials for various applications is growing due to the development of new and simple production and treatment methods. Amongst the techniques used to treat graphene nanomaterials dry methods like plasmas or ion beams are of particular interest. In this work a low temperature plasma technique is used to incorporate nitrogen atoms into the carbon network of graphene sheets. In order to gain a better understanding of such processes material analysis techniques (NEXAFS and XPS) were combined with the results coming from molecular dynamics simulations and plasma know-how. The results show that the plasma post treatment of graphene nanowalls can be regarded as a balance between vacancy formation, functionalization, doping and crosslinking. Moreover, MD simulations provided insight into fundamental mechanisms like the formation of different bonds due to the interaction of the surface with different kind of species with variable kinetic energy. This can help to improve different types of doping/functionalization techniques using energetic species: the study reveals for example the role of N2+ species, the kinetics of vacancy formations depending on type and energy of the species, the formation of amines or graphitic nitrogen, and the role of impurities such as NHx species.
Keyword: Graphene, Graphene nanowalls, Plasma post-treatment, Nitrogen incorporation, Molecular dynamics simulations, NEXAFS spectroscopy, XPS spectroscopy
Surface modification of polypropylene non-woven filter by O2 plasma/acrylic acid enhancing Prussian blue immobilization for aqueous cesium adsorption
Narges Dehbashi Nia, Seung-Woo Lee, Sungjun Bae, Tae-Hyun Kim, Yuhoon Hwang
• PP filter was successfully activated by combination of O2 plasma and acrylic acid.
• Mechanical properties of PP were enhanced without morphological changes.
• Contents of Prussian blue was dramatically increased by surface modification.
• PP-O2/AA+PB shows high Cs adsorption capacity with long-term performance.
Radioactive cesium is commonly emitted during nuclear accidents and Prussian blue (PB) is an effective adsorbent with superior selectivity toward cesium. This study describes the surface modification of a polypropylene non-woven filter (PP) as the supporting material for PB immobilization, which included O2 plasma treatment and acrylic acid (AA) modification. AA was successfully polymerized using O2 plasma to provide a reaction site for the polymerization. The carboxylic acid groups introduced by the polymerization of AA induced a higher amount of PB immobilization on the surface. The cesium adsorption performance of the prepared adsorbent filter was evaluated via adsorption kinetics and isotherm analyses. The maximum adsorption capacity was calculated as 51.9 mg/g according to the Langmuir isotherm. To confirm its long-term practical applicability, the adsorbent filter was incorporated into a flow-through water treatment system that was operated for three months. The tested five-layer filter achieved a 100% cesium removal efficiency (initial concentration 40 μg/L) during the first 12 days, after which a 50% removal efficiency was maintained for 24 days. Therefore, the surface modification methodology proposed herein provides a promising means to convert commercial filter materials into advanced water treatment filters for the removal of radioactive cesium from contaminated water.
Keywords: Polypropylene, Surface modification, Cesium, Prussian blue, Adsorption
Influence of surface activation on the microporosity of PE-CVD and PE-ALD SiOx thin films on PDMS
Christian Hoppe, Felix Mitschker, Lukas Mai, Maciej Oskar Liedke, Teresa de los Arcos, Peter Awakowicz, Anjana Devi, Ahmed Gamal Attallah, Maik Butterling, Andreas Wagner, Guido Grundmeier
The microporosity, structure and permeability of SiOx thin films deposited by microwave plasma-enhanced chemical vapour deposition (PE-CVD) and plasma-enhanced atomic layer deposition (PE-ALD) on polydimethylsiloxane (PDMS) substrates were investigated by positron annihilation spectroscopy and complementary technique, such as X-ray photoelectron spectroscopy, infrared spectroscopy, time of flight mass spectroscopy and atomic force microscopy. The SiOx films were deposited onto spin-coated PDMS substrates, which were previously exposed to an oxygen plasma thus achieving the conversion of the top polymer layer into SiOx. The presence of this oxidised surface near the region led to an overall decrease in micropore density and to a shift towards smaller pore sizes within the deposited SiOx films. A correlation between the oxygen fluence during the oxygen plasma treatment and the microporosity of the PE-CVD and PE-ALD SiOx films could be established.
Keywords: FTIR, PALS, PDMS, PE‐ALD, PE‐CVD, porosity
Plasma induced reactive oxygen species-dependent cytotoxicity in glioblastoma 3D tumourspheres
Janith Wanigasekara, Carlos Barcia, Patrick J. Cullen, Brijesh Tiwari, James F. Curtin
Ireland, Spain, Australia
The aim of this study was to determine the effects of a pin-to-plate cold atmospheric plasma (CAP) on U-251 MG three-dimensional (3D) glioblastoma spheroids under different conditions. 3D tumorspheres showed higher resistance to the CAP treatment compared to 2D monolayer cells. A single CAP treatment was able to induce cytotoxicity, while multiple CAP treatments augmented this effect. CAP was also able to induce cytotoxicity throughout the tumoursphere, and we identified that reactive oxygen species (ROS) plays a major role, while H2O2 plays a partial role in CAP-induced cytotoxicity in tumourspheres. We conclude that ROS-dependent cytotoxicity is induced uniformly throughout glioblastoma and epidermoid tumourspheres by direct CAP treatment.
Keywords: 3D tumourspheres, cold atmospheric plasma, cytotoxicity, epidermoid, glioblastoma, reactive oxygen and nitrogen species, ROS dependent
Can we remove tattoos with non-thermal atmospheric plasma?
Francesco Tampieri, Ariadna G. Araguz, Cristina Canal
Current methods for tattoo removal are long, costly and have drawbacks such as scarring among others. Looking for alternatives, here we assess the feasibility of non-thermal plasma (NTP) as a standalone method for the removal of tattoos. We report the results of atmospheric pressure plasma jet treatment of real tattoo inks suspensions in water and in gelatin (liquid or as a solid film), selected as a model of skin. Analysis of the residual color and the temperature effect in all the samples after plasma treatment reveals significant differences between water and the skin model. Kinetic considerations and the extension of our results to more realistic scenarios allow us to conclude that NTP cannot compete with the current laser technology in a real application.
Keywords: cold plasma, decomposition, gelatin, ink, skin
Plasma-water-based nitrogen fixation: Status, mechanisms, and opportunities
Zhongzheng Huang, Ao Xiao, Dawei Liu, Xinpei Lu, Kostya (Ken) Ostrikov
Nitrogen-based crop fertilizers are the most important industrial chemicals supporting the global food supply. Plasma-water-based nitrogen fixation (PWBNF) provides a clean, sustainable, and flexible alternative, which is amenable for decentralized, small-to-medium-scale production systems. This process is based on the targeted activation of N2 or air molecules by plasmas. Plasma can interact with water molecules, water droplets, and water layers through the plasma physical and chemical mechanisms. This review summarizes the current state of the art of PWBNF and provides insights into the effective mechanisms for the synthesis of NH3, NO2− and NO3− in highly reactive plasma environments. The opportunities and challenges for this plasma-enabled approach are identified to guide the development of sustainable nitrogen fixation technology.
A review on the role of plasma technology in the nano-finishing of textile materials with metal and metal oxide nanoparticles
Maja Radetić, Darka Marković
Nano-finishing of textiles with metal and metal oxide nanoparticles (NPs) is relatively simple, but insufficiently efficient binding between the fibers and NPs poses a big problem because of the poor stability of textile nanocomposites. A good way to overcome this problem is to activate the fibers by plasma. Selection of gas and optimization of plasma processing parameters lead to a generation of new functional groups improving the binding of NPs. Another approach relies on the formation of stable nano-coatings by magnetron sputtering. Progress has been recently made in plasma-assisted in situ synthesis of metal NPs where toxic chemical reducing agents were replaced with short plasma treatment. This review paper addresses substantial roles of plasma, which enhance the performance of nano-finished textiles.
A numerical investigation of the effect of thermal aging, processing and humidity on initiation and delayed cracking in plasma-sprayed coatings
Bassem El Zoghbi, Rafael Estevez
Lebanon, France
The effect of aging by the relaxation of the initial thermal stresses related to the processing on the initiation and propagation of the inter-splat and the intra-spat cracks in plasma sprayed zirconia is analyzed using finite element model and a description of failure with cohesive surfaces. A multi-scale approach is adopted in which the inter-splat and intra-splat crack growth is described with a rate-temperature and humidity dependent cohesive zone model that mechanically represents the reaction-rupture mechanism underlying stress and environmentally assisted sub-critical failure. It is found that the relaxation of the initial thermal stresses generates a significant initial damage at the inter-splat scale by the nucleation of inter-splat cracks and a minor initial damage at the intra-splat scale. The results show that the rate of inter-splat cracks increases with the relative humidity and especially with the temperature at which the relaxation occurs. The effect of the initial damage generated by the thermal aging on the resistance of the polycrystal of plasma sprayed zirconia against intra-splat slow crack growth under static fatigue loading is investigated. The results show that the initial damage at the intra-splat scale does not affect its resistance against intra-splat slow crack growth. However, the initial damage at the inter-splat scale leads to an increase in the slow cracking rate for a loading level KI and a reduction in the threshold load K0 below which no slow crack growth occurs as the individual splat is embedded in a damaged equivalent continuum representing the overall splat structure. The aim of this work is to provide a reliable predictions and insight in long lasting applications of plasma sprayed ceramic materials.
Plasma electrolytic oxidation up to four-steps performed on niobium and Nb-Ti alloys
Bruno Leandro Pereira, Carlos Maurício Lepienski, Viviane Seba, Michael J.D. Nugent, Ricardo Torres, Pedro Akira Bazaglia Kuroda, Carlos Roberto Grandini, Paulo Soares
Brazil, ireland
Plasma electrolytic oxidation (PEO) of up to four steps were performed on Niobium (Nb), and binary Niobium-Titanium alloys (Nbx-Ti, x = 50%, 90 wt.%), and the resulting oxidized surfaces were compared to their respective metallic substrate. The first and third steps were carried out in the phosphorus electrolyte, whereas the second and fourth steps were oxidized in the electrolyte containing calcium ions. Coatings formed from the second step were porous, with the chemical composition containing both calcium and phosphorus elements. The PEO process decreased the elastic moduli to approximately 60 GPa and increased the surface cell viability compared to the metallic surfaces without treatment. All surfaces produced from the second step-PEO demonstrated improved characteristics for application in metallic implants. Additionally, those performed on the alloys in electrolytes containing phosphate ions (up to three steps) exhibited greater performance on cytocompatibility tests.
High density La-Fe-Si based magnetocaloric composites with excellent properties produced by spark plasma sintering
X.C.Zhong, S.M.Wu, X.T.Dong, Y.X.Li, J.H.Huang, C.L.Liu, H.Zhang, Y.L.Huang, H.Y.Yu, W.Q.Qiu, Z.W.Liu, M.L.Zhong, Z.C.Zhong, R.V.Ramanujan
China, Singapore
• High density La-Fe-Si based composites were fabricated by short time SPS followed by annealing.
• The magnetocaloric and mechanical properties could be tuned by changing the SPS temperature.
• The optimum process was SPS@1273 K/5min followed by annealing@1323 K/24 h.
• Excellent (σbc)max ∼ 1GPa, λ ∼ 17.68 W/m∙K and large (−ΔSM)max ∼ 2.3 J/kg‧K@2T were obtained.
La(Fe,Si)13 based magnetocaloric composites were prepared by spark plasma sintering (SPS), followed by annealing. The microstructure, mechanical and magnetocaloric properties were investigated. With increasing SPS temperature (TSPS) below 1373 K, the content of (La,Pr)(Fe,Co,Si)13 majority phase increased, while the content of minority phase α-Fe decreased. The increase of TSPS from 973 K to 1373 K greatly improved the composite density, and the density sharply increased from ∼ 68 % to 98 %. After SPS at 1273 K/5 min followed by 1323 K/24 h annealing, high content of 89.35 wt% of the desired (La,Pr)(Fe,Co,Si)13 phase was obtained in LaFe11.6Si1.4/10wt%Pr2Co7 composites. A large increase of Curie temperature (TC) from 196 K to 297 K was observed. The maximum magnetic entropy change (−ΔSM)max reached 2.3 J/(kg‧K) under 2 T magnetic field. ~ 97 % of full density, excellent compressive strength of ~ 1GPa and high thermal conductivity of 17.68 W/m∙K were exhibited. Thus, a route to produce high density La-Fe-Si based magnetocaloric composites with excellent mechanical properties and thermal conductivity, good (−ΔSM)max and adjustable TC by short time spark plasma sintering followed by annealing was demonstrated.
Keywords: Spark plasma sintering, Annealing, High density, Magnetocaloric effect, La(Fe,Si)13 based composites
Micro-scaled morphology of Ti-40Nb-xZr alloy with applied voltage via plasma electrolytic oxidation
Hye-Ri Cho, Han-Cheol Choe
Republic of Korea
• Needle-like structure of Ti-40Nb-xZr alloys changed to equiaxed structure as Zr content increased.
• Nanoindentation hardness and elastic modulus of Ti-alloys decreased as the Zr content increased.
• Irregular pores were formed on the alloy surface as the applied voltage increased in the PEO process.
• Surface roughness of the PEO-treated Ti-alloys increased as the applied voltage and Zr content increased.
• Contact angle of the PEO-treated Ti-alloys decreased as the applied voltage and Zr content increased.
In this study, the formation of micro-scale morphology on Ti-40Nb-xZr alloys was investigated under plasma electrolytic oxidation (PEO) treatment. By varying the Zr content to 0, 3, 7, and 15 wt.%, non-toxic, low-modulus alloys were prepared. PEO was then performed using a direct current power source with the sample as the anode and a carbon rod as the cathode in an electrolyte solution of 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate. The applied voltage was varied from 180–380 V at a current density of 75 mA for 3 min. In the Ti-40Nb-xZr alloys, as the Zr content increased, the microstructure changed from a needle-like structure to an equiaxed structure, and the elastic modulus and hardness in nanoindentation tests decreased (from 120 to 67 GPa and 4.55 to 2.00 GPa, respectively). As the applied voltage increased during the PEO process, the pore size increased. The TiO2 layer formed on the alloy surface contained Ca and P from the electrolyte. The surface roughness obtained from atomic force measurements was the lowest in the bulk samples (0.133 to 0.024 μm), and it gradually increased as the applied voltage increased and decreased as the Zr content increased. As the applied voltage increased, the contact angle decreased, whereas as the Zr content increased, the contact angle increased.
Keywords: Titanium-Niobium-Zirconium alloys, Plasma electrolytic oxidation, Applied voltage, Elastic modulus
Microstructural study of Ni and Ni-20Cr particles plasma sprayed on stainless steel substrate at 300 ˚C
Arslan Khalid, Musharaf Abbas, Yongang Zhang, Margaret Hyland, Paul R. Munroe
Australia, China New Zealand
• The addition of Cr to Ni modifies the splat formation by improving wettability during spreading.
• Good interfacial contact at the centre of the splat, but poor at the splat periphery due to the splat edge curling up.
• Splat-substrate inter-diffusion along with substrate localised melting.
• Fe/Cr-based material is intimately intermixed into the interior of the Ni splat.
In thermal spray coatings, the bonding and adherence of the spray particles (called splats) to the substrate surface significantly influence the overall quality of the finished coating. In this study, both elemental Ni and Ni-20Cr powders were plasma sprayed onto polished stainless-steel substrates held at 300 ˚C. Splat formation for both feedstock materials was investigated and compared. Detailed studies of the microstructure of single splats as well as the splat-substrate interface were performed using scanning electron microscopy (SEM), focused ion beam (FIB) microscopy and transmission electron microscopy (TEM). The additions of Cr to nickel promoted improved adherence of the splat to the substrate and modified splat formation by improving wettability during spreading. More intriguingly, energy dispersive spectroscopy (EDS) mapping and line scans, performed on TEM cross-sections, revealed splat-substrate inter-diffusion and chemical inter-mixing. Of particular note, a ‘jet’ of iron/chromium-based material, arising presumably from the substrate, was noted to be intimately intermixed into the interior of the nickel splat.
Keywords: Plasma spray, Ni and Ni-20Cr, Microscopy, Single splat morphology, Interfacial bonding
One-step fabrication of double-layer nanocomposite coating by plasma electrolytic oxidation with particle addition
Shuqi Wang, Lei Wen, Yaming Wang, Yulin Cheng, Yingliang Cheng, Yongchun Zou, Yixing Zhu, Guoliang Chen, Jiahu Ouyang, Dechang Jia, Yu Zhou
China, Germany
• A novel double-layer nanocomposite coating is prepared via a facile one-step PEO-SDSN technique.
• The addition of nanoparticles creates interesting rising and falling changes in current.
• A new fabrication strategy of multifunctional coatings by tailoring particles species is proposed.
• The instant, dense discharges are induced by Highfield, high temperature and bubbles accumulation.
• Such intense discharges significantly improve the growth rate of nanocomposite coating.
A novel double-layer structural nanocomposite coating was prepared via one-step plasma electrolytic oxidation-synchronous deposition & sintering of nanoparticles (PEO-SDSN) technique under unique threshold conditions of concentration of added nanoparticles, electrolyte temperature, and applied voltage. The special discharges at the coating/electrolyte interface lead to the directional migration, deposition and sintering of organic (eg. PTFE) or inorganic (eg. SiC) nanoparticles, combined with the dynamic growth equilibrium of bottom oxide layer and outer nanoparticle deposition & sintering layer. Different from traditional PEO, the addition of nanoparticles creates interesting rising and falling changes in current and corresponding discharging characteristics. The underlined formation mechanism of the double-layer coating was detected by OES combined with discharging phenomena and coating structure evolution. Moreover, compared with the single PEO coating, the double-layer structural nanocomposite coating has better comprehensive performances, such as corrosion protection, and low and stable friction coefficient. The PEO-SDSN technique is energy saving, more importantly, it provides a brand-new fabrication strategy for a series of double-layer multifunctional coatings by tailoring the nanoparticles species. Eventually, the potential applications and guiding strategies of double-layer nanocomposite coating are presented.
Keywords: Plasma electrolytic oxidation, Optical emission spectroscopy, Discharge spark, Organic/inorganic nanoparticles, Double-layer structural nanocomposite coating
Water-plasma-activated g-C3N4 for enhanced photodegradation of bisphenol A synergized with persulfate oxidation
Jian Xu, Xinran Li, Yanxia Zheng, Xuelian Yu, Jing Zhou, Xiaoqiang An
• A novel solution plasma method was used to activate the surface of g-C3N4.
• Nitrogen vacancies and hydrophilic groups are introduced.
• BPA removal rate for activated g-C3N4 is 4.5-fold higher than that of pristine one.
• The mechanism of this improvement is deduced.
• This study provides a new strategy for regulating surface microstructure
Herein, a facile water-plasma strategy is employed to modify the surface structure of graphite-carbon nitride (g-C3N4) to enhance its photocatalytic performance for persulfate activation. High energy electrons and highly active free radicals from water-plasma discharge not only induce nitrogen vacancies, but also generate hydrophilic groups on g-C3N4 surface, which can effectively modulate the energy levels, facilitate the interaction of water with catalyst, and meanwhile promote the separation and transfer of photogenerated charge carriers. When used for bisphenol A (BPA) degradation, water-plasma-activated g-C3N4 exhibits 4.5-fold enhancement of reaction rate compared to that of pristine g-C3N4. This work offers deep insights into in-situ defect engineering of g-C3N4 as Fenton-like catalyst.
Keywords: g-C3N4, Water-plasma, Nitrogen vacancies, Persulfate activation,
Bisphenol A
Quantification of complex protective surface oxide layer formed during plasma jet exposure of multicomponent ultra-high temperature carbides
Ambreen Nisar, Tamil Sakthivel, Cheng Zhang, Benjamin Boesl, Sudipta Seal, Arvind Agarwal
• Gradual addition in the UHTC components ranging from a binary to a quaternary (Ta,Nb,Hf,Ti)C system.
• Role of multi-elements on the surface oxide layer formation during simulated re-entry conditions via plasma arc jet exposure.
• Core-level X-ray photoelectron spectroscopy (XPS) to determine the oxidation state.
• Retention of metal carbide phase in MC-UHTCs observed both in XPS and XRD analysis.
• Complex mixed oxide scale formation via preferential oxidation to improve oxidation resistance.
Multi-component ultra-high temperature ceramics (MC-UHTCs) has garnered attention due to their improved thermo-mechanical and oxidation properties. MC-UHTC was progressively formed by adding a UHTC component at each step, producing binary, ternary and quaternary UHTC systems, processed by spark plasma sintering (SPS). We investigate the role of multi-elements and thermochemical stability of the surface oxide layer formed during plasma arc jet exposure (T > 2500 °C) of MC-UHTCs using core-level X-ray photoelectron spectroscopy (XPS) correlated with the structural investigation. The results indicate that adding a UHTC component improves oxidation resistance due to the assemblage of refractory phases forming complex mixed oxides via preferential oxidation. XPS spectra of Ta4f, Nb3d, Ti1p, and Hf4f showed that the nature of the chemical bonds switched from metal carbides to metal oxides (and metal oxy-carbides) in the binary system with retained metal carbides in ternary and quaternary UHTCs. The absence of a metal carbide peak in the high-resolution C1s scan of the binary system also supports this finding. The principal complex mixed oxide phases emanated in the exiguous oxidation of MC-UHTCs are quantified using Rietveld analysis. Overall, this study suggests that MC-UHTC is a promising material for possible application in thermal protection systems (TPS).
Keywords: Complex Surface Oxide Layer, Ultra-High Temperature Ceramics (UHTCs),
Multi-Component, Thermal Protection System (TPS), Plasma Jet Exposure
Effects of acid treatment and plasma micromachining on the surface properties of carbon fibers
Tingting Mei, Ming Gao, Yu Wang, Yifan Huang, Paul K. Chu
• The effects of strong acid and weak acid treatment on the carbon cloth (CC) surface assisted by plasma micromachining are investigated.
• Different surface properties are observed and protein adsorption is investigated to assess the biocompatibility.
• The combination of plasma micromachining and acetic acid treatment is demonstrated to mitigate protein adsorption by 30.06%.
The effects of strong acid and weak acid treatment on the carbon cloth (CC) surface assisted by plasma micromachining are investigated in terms of the morphology, chemical composition, and surface free energy. Different surface properties are observed and protein adsorption is investigated to assess the biocompatibility. The combined plasma and acetic acid treatment leads to more surface oxidation due to the large number of carboxyl groups on the CC surface and surface energy increase by 18.6 times. Since the effects of acetic acid are relatively mild, few morphological changes are found, but protein adsorption decreases by about 30% after the surface treatment compared to the untreated CC. The combination of plasma and weak acid treatment is not only simple and convenient, but also very effective in controlling protein adsorption on biomedical carbon cloth.
Keywords: Plasma micromachining, Carbon cloth, Protein adsorption, Strong and weak acid treatment
Effect of substrate temperature on microstructure and mechanical properties of TiAl alloy fabricated using the twin-wire plasma arc additive manufacturing system
Lin Wang, Wenlu Zhou, Chen Shen, Yuelong Zhang, Fang Li, Yuhan Ding, Jianwen Xin, Baosen Wang, Xueming Hua 
TiAl alloy becomes a promising high-temperature structural material due to excellent mechanical properties at elevated temperature. However, the inherent brittleness makes it difficult to be processed by traditional technologies. Therefore, an innovative twin-wire plasma arc additive manufacturing (TW-PAAM) process is developed to fabricate TiAl alloy. Substrate heating is indispensable during additively manufactured TiAl alloy, which can alleviate its crack tendency. In this paper, crack-free TiAl alloy samples are fabricated using TW-PAAM, and the effect of substrate temperature (560, 620 and 680 °C) on as-deposited TiAl alloy is investigated in detail. With the increase in substrate temperature, microstructural lamellar spacing and colony size exhibit the tendency of increase. Also, α2 phase content, recrystallization degree and high Schmid factor frequency present the decrease tendency. These variations of microstructure characteristics further lead to the decrease in both microhardness and tensile properties of the deposit. These findings provide a valuable reference for optimizing microstructures and mechanical properties of additively manufactured TiAl alloys.
Duplex treatment of arc plasma nitriding and PVD TiN coating applied to dental implant screws
Fei Sun, Xing-Long Liu, Shi-Qi Luo, Ding-Ding Xiang, De-Chun Ba, Zeng Lin, Gui-Qiu Song
In this research, APN and PVD processes were carried out uninterrupted using a homemade industrial coating machine. The APN-PVD duplex treatment method was applied to titanium alloy implant screws, and the conclusions were as follows:
1. APN-PVD reduced the surface roughness, increased the surface hardness, produced a gradient composite structure, and significantly improved the adhesion of the PVD TiN coating. ...
2. Compared with the PVD process alone, APN-PVD-treated screws improved the preload, ...
In modern dentistry, surface modification technology is critical for the long-term service of dental implants. The purpose of this study was to evaluate the effects of the duplex treatment of arc plasma nitriding and TiN coating on the mechanical behavior of implant systems. The Ti6Al4V screws of dental implants were treated by physical vapor deposition (PVD), arc plasma nitriding (APN), and arc plasma nitriding-physical vapor deposition (APN-PVD). The surface characteristics, loosening properties, and fatigue performance of different treated screws were analyzed. The results showed that APN-PVD duplex treatment produced a gradient surface structure, reduced the surface roughness, and improved the TiN coating adhesion. Compared with the PVD-treated screws alone, APN-PVD-treated screws improved anti-loosening performance, reduced surface wear, and prolonged fatigue life. Duplex treatment by arc plasma nitriding and TiN coating may be a method suitable for dental applications.
Structure-property correlation and high-temperature erosion performance of Inconel625-Al2O3 plasma-sprayed bimodal composite coatings
Gaurav Prashar, Hitesh Vasudev
The bi-modal and other coatings were developed using the plasma spray technique and were analyzed for erosion performance at the high-temperature condition. The structure-property correlation was developed to understand the erosion behavior of developed coatings. Here are the outcomes of the presented work:
• Three combinations of IN625-AL coatings were successfully developed by using the plasma spraying technique. ...
• The cross-section of the developed coatings showed a typical coating thickness of ...
In the present experimental work, Inconel-625 (IN625) was reinforced with Al2O3 (30 wt%) to develop composite coatings with plasma spraying technique on ASTM SA210 GrA1 boiler steel. Three composite coatings were developed by varying Al2O3 particle sizes in micrometric, nano, and bimodal forms. The Inconel625 + 30 wt% micrometricAl2O3, Inconel625 + 30 wt% nano-Al2O3 and Inconel625 + 15 wt% micrometric Al2O3 + 15%nano-Al2O3 combinations were considered. The developed composite coatings were analyzed for the detailed microstructure studies, microhardness, fracture toughness, and elevated temperature erosion test. The elevated temperature erosion tests for bare substrate and coatings were conducted at 900 °C by using an erosion test rig (air jet) at two impingement angles 30° and 90°. By studying the eroded surfaces through scanning electron microscopy (SEM) micrographs, the mechanism of material removal was predicted. The existence of grooves and lips at a 30° and 90° impact angle on surfaces indicate the erosion mechanism consists of ploughing and micro-cutting action in the substrate. At 30° and 90° impact angles, all composite coatings exhibited a brittle erosion mode as erosion characteristics. The micrographs of eroded surfaces indicated splat removal, cracks, and fracture as the main erosion mechanism. The outcomes of the tests revealed that the bimodal composite coatings successfully protect the underlying substrate owing to their hardness and fracture toughness which is higher than the other two coatings. The better outcome of bimodal coatings was related to refined microstructures and good interaction among nano and micrometric Al2O3 reinforcement.
Relationship between the mechanical properties and structure of a suspension plasma-sprayed thermal barrier coating with columnar microstructure
Yasuhiro Yamazaki, Masahiro Morikawa, Tatsuya Hamaguchi, Yoichiro Habu, Yuhei Ohide, Kaito Takagi
Japan, The Netherlands
The out-of-plane Young's modulus and shear strength of the single columns of an SPS TBC having a unique cauliflower-like columnar microstructure were evaluated. Moreover, the influence of thermal aging on the mechanical properties were discussed.
The following main conclusions were drawn.
1. The Eo of such SPS TBCs is significantly lower than that of conventional APS TBCs; moreover, SPS TBCs possess higher anisotropy of the Young's modulus between the in-plane and out-of-plane directions. ...
2. The Young's ...
To investigate the mechanical properties of a suspension plasma-sprayed (SPS) thermal barrier coating (TBC) with a unique cauliflower-like columnar structure, shear and cantilever bending tests were conducted on its single submillimeter-sized columns. In the shear test, the fracture of the single columns occurred at the porous layer near the top-coating/bond-coating interface. Compared with conventional atmospheric plasma-sprayed (APS) TBCs having a lamellar microstructure, the cantilever bending test revealed a significantly low Young's modulus along the out-of-plane direction and strong anisotropy in the elastic modulus of the SPS TBC. The shear strength and out-of-plane Young's modulus of the single columns increased due to the sintering resulting from thermal aging; however, the increasing ratio of the shear strength was higher than that of the Young's modulus. Both experimental and finite element analysis results indicated that the mechanical properties of the SPS TBC, as well as their variation with thermal aging, are dominated by those of the porous layer within the single column undergoing sintering. Moreover, the experimental results suggested that SPS TBCs having a cauliflower-like columnar microstructure have superior durability to thermal cycles compared with APS TBCs.
Fabricating an anti-corrosion carbonate coating on Mgsingle bondLi alloy by low-temperature plasma
Yuchen Li, Zhenwei Kang, Xiaoke Zhang, Jinshan Pan, Ying Ren, Genshu Zhou
China, Sweden
A thick coating with layered structure can be fabricated on Mgsingle bondLi alloy by low-temperature plasma, which exhibits an effective protection of the alloy in NaCl solution. The high corrosion resistance of the coating is attributed to the presence of a stable Li2CO3 outer layer, which is sparingly soluble in water. The plasma treatment leads to the growth of a thick oxide film with MgO dominant in the inner layer while Li2O dominant in the outer layer. The oxides react with water in air and ...
Despite the huge demand for ultra-light magnesium‑lithium (Mgsingle bondLi) alloys, practical applications of Mgsingle bondLi alloys are still severely restricted due to their poor corrosion resistance. Here, we report a new method utilizing low-temperature plasma to grow an oxide layer on the Mgsingle bondLi alloys in atmospheric condition, which reacts with CO2 and water in the air and consequently transform into a protective coating. The prepared coating has a layered structure consisting of a Mg(OH)2 inner layer and a Li2CO3 outer layer. The composition distribution can be attributed to the different migration rates between Li+ and Mg2+ during coating formation. The Li2CO3 outer layer is sufficiently compact and very stable, with an ultra-low solubility in water, explaining the superior corrosion resistance of the coating in 3.5% NaCl solution. This simple and eco-friendly surface treatment provides a novel way of fabricating protective coatings on Mgsingle bondLi alloys.
Real-time measurement of axial temperature in a coaxial dielectric barrier discharge reactor and synergistic effect evaluation for in-plasma catalytic CO2 reduction
Xiao-Song Li, Ye-Cheng Li, Li-Yuan Wang, Jing-Lin Liu, Ai-Min Zhu
Due to serious difficulty in the measurement of catalyst-bed temperature (Tb) for in-plasma catalysis (IPC), the evaluation of the IPC synergistic effect is still disputed. Herein, we reported a real-time measurement of axial temperature (Tax), which is much closer to Tb than wall temperature (Tw), using a thermocouple in a catalyst-packed coaxial dielectric barrier discharge reactor for the first time. In plasma catalytic CO2 reduction, the effects of discharge power and flow rate on Tax, Tw, and CO2 conversion were examined. On the basis of Tax, compared with the thermal catalytic case, the plasma catalytic case only shows a weak synergistic effect. It was confirmed that the synergistic effect is overestimated if based on Tw (except for the heat-insulated or quasi-adiabatic reactors).
Time resolved study of ignition of microwave discharge in liquid hydrocarbons
Yuri A. Lebedev, Galina V. Krashevskaya, Timur S. Batukaev, Andrey V. Mikhaylyuk
Results of the study of acoustic phenomena and changes in the structure of the microwave (2.45 GHz) discharge in liquid hydrocarbons in time are presented. Discharge was ignited at the tip of microwave antennas with conical or rounded ends. Petroleum solvent Nefras was chosen as representative of liquid hydrocarbons. Electret microphone and high-speed video cameras were used to study the discharge. It is shown that the discharge is always attached to the top of the cone in the case of the conical end of the antenna whereas ignition of the discharge generates in the gas part of the reactor a set of acoustic oscillations with frequencies corresponding to the characteristic oscillations of the reactor.
Revisiting the surface characterization of plasma-modified polymers
Jorane Berckmans, Annaëlle Demaude, Delphine Merche, Kitty Baert, Herman Terryn, Tom Hauffman, François Reniers
Many papers dealing with the surface analysis of plasma polymers or plasma-modified polymers report the use of X-ray photoelectron spectroscopy (XPS) to quantify the surface composition. However, most of the time, quantification is performed using software that includes an equation based on the assumption that the sample is homogeneous in composition. However, for plasma-treated samples, this is often not the case. The usual analysis of XPS spectra does not allow the exact quantification in the case of an inhomogeneous sample. In this paper, we show that it is possible to obtain a depth profile of the composition, and a more accurate surface composition by using another mathematical approach for surface quantification, being QUASES Tougaard.
Study of uniformity of atmospheric pressure plasma microjet array for maskless parallel micropatterned etching
Junfeng Yang, Lingju Xia, Shuneng Zhou, Lirui Liao, Zekun Wang, Li Wen, K. C. Yan, Hai Wang, Jiaru Chu
A novel atmospheric pressure plasma microjet (APPμJ) array is proposed to realize maskless parallel micropatterned etching of materials. Due to applying microfabrication technology, the dimension and distance of multiple jets in an array can be adjusted at a micro/nanoscale. However, interactions among multiple jets often lead to inconsistency of microjets and nonuniformity of sample etching. In this study, a 1 × 2 APPμJ array with 90-μm nozzles and varying jet-to-jet distance is developed. The effects of different operating factors on the consistency of the APPμJ array are investigated. The experiment results show that the consistency of the microjet array and uniformity of sample etching can be greatly improved by optimizing operating parameters, such as applied voltage, gas flow rate, and jet-to-jet distance.
Plasma-driven biocatalysis: In situ hydrogen peroxide production with an atmospheric pressure plasma jet increases the performance of OleTJE when compared to adding the same molar amount of hydrogen peroxide in bolus
Hannah L. Wapshott-Stehli, Brayden G. Myers, María J. Herrera Quesada, Amy Grunden, Katharina Stapelmann
Enzymes like fatty acid peroxygenase OleTJE are desirable enzymes for the industry. While they require inexpensive hydrogen peroxide for activity, the same hydrogen peroxide also causes overoxidation of their reactive heme center. Here, we generate hydrogen peroxide slowly in situ using the Cooperation in Science and Technology (COST)-Jet, an atmospheric pressure plasma jet, to avoid overoxidizing OleTJE. The COST-Jet was operated in helium with a water admixture to provide hydrogen peroxide for OleTJE activity. This helium/water admixture produced the highest enzyme turnover numbers after 2 min of treatment. These turnover numbers were even superior to using an equimolar amount of hydrogen peroxide to treat the enzymes exogenously, showing that this plasma source can provide a reliable amount of reaction mediator to support OleTJE activity.
Keywords: atmospheric pressure plasma jet, biocatalysis, cytochrome P450 enzymes,
hydrogenperoxide, plasma liquid chemistry
Operation mode recognition of surface microdischarge based on the gray level histogram
Chen Lu, Zilan Xiong
A visible image of gas discharge contains rich information. This study investigates the visible light information of surface microdischarge (SMD) under different operation modes and develops a method to realize online monitoring of the operation modes based on a gray level histogram (GLH). Two SMD sources were used to verify the effectiveness of the method. The distribution curve in the GLH gradually shifted to a large gray level as the operation mode transferred from ozone mode to NOx mode. The mean, variance, energy, entropy, and uniformity threshold values used to distinguish the operation modes were found to be approximately the same in both sources. Finally, a simplified distribution map based only on entropy and uniformity is proposed for the fast operation mode recognition of SMD.
Surface and subsurface AFM study of carbon-implanted polyurethane
Ilya A. Morozov, Alexander S. Kamenetskikh, Anton Y. Beliaev, Roman I. Izumov, Marina G. Scherban, Dmitriy M. Kiselkov
Carbon ions were implanted into polyurethane, a two-phase polymer whose internal structure is naturally covered with a soft nanofilm. The surface and subsurface of the modified material were studied by atomic force microscopy. A wrinkled nanolayer of inhomogeneous stiffness appears on the surface. Initial treatment affects the outer soft fraction of the polyurethane, then the modified layer extends deeper and starts to grow towards the surface finally becoming homogeneous. The subsurface of the modified layer has local stack-like fractures or mesh-like nanostructures of increased activity. Stretching the treated material gives nanocracks in the subsurface area. The cracks are hidden by the outer layer and visible on the surface as bumps. The developed methods are easily applicable to study the subsurface features of plasma-treated polymers.
Plasma assisted combustion of methane-air mixtures: Validation and reduction
L. Cheng, N. Barleon, B. Cuenot, O. Vermorel, A. Bourdon
France, Germany
For several years now plasma assisted combustion has been the subject of intense research due to stabilization effects a plasma can have on flames. Particularly, experiments have shown the promising impact of Nanosecond Repetitively Pulsed discharges on combustion while not exceeding an energy consumption of a few percent of the flame power. In this work, an incremental methodology with a step-by-step approach has been used to build a single plasma mechanism upon which combustion is added using the GRI 3.0 and Konnov v0.6. The methodology focuses on three key aspects of plasma assisted combustion: fast gas heating, slow gas heating and radical production. Selected experiments focusing on one or more of these aspects allow to validate the mechanism in large ranges of temperature (300-1500 K) and pressure (0.1-1 bar) in air, methane-air and argon diluted mixtures using glow and spark discharges. These experiments include a plasma assisted ignition case on which the ignition delay time is well captured by the mechanism. Slow gas heating has been modeled using a vibrational relaxation model validated against a detailed vibrational description. Discussions on ambiguous rates for critical reactions of excited nitrogen quenching are made in the light of their impact on the results on the chosen experiments. Finally, the resulting 100-species GRI 3.0-based and 264-species Konnov v0.6-based plasma mechanisms are reduced to make them suitable for multi-dimensional simulations. The DRGEP reduction method, based on plasma experiments and canonical combustion cases, is applied allowing to reduce the number of species by a factor larger than two. For the GRI-3.0 plasma mechanism, the reduced mechanism contains 47 species and 429 reactions. Hence significant performance is gained, opening the way to multi-dimensional simulations of plasma assisted combustion.
Keywords: Plasma assisted combustion, Chemistry, Discharges, Reduction
One-step plasma electrolytic oxidation with Graphene oxide for Ultra-low porosity Corrosion-resistant TiO2 coatings
Ziwei Guo, Zehui Yang, Yongnan Chen, Hongzhan Li, Qinyang Zhao, Yiku Xu, Haifei Zhan, Jianmin Hao,Yongqing Zhao
China, Australia
• By adding GO, the surface porosity and overall porosity of the GO/TiO2 coating decreases to 1.1% and 2.21 vol%, respectively, and the aspect ratio of the pores is increased to 0.7 ∼ 0.8.
• The energy release and functional groups of GO affect the amount and the time of molten oxide to eject from discharge channels to decrease the porosity. At the same time, the conductivity of GO causes the discharge to proceed along the surface of GO, and the pore shape changes from connected pores to isolated pores, resulting in a high pore aspect ratio.
• The corrosion resistance of the GO/TiO2 coating is higher 57.8% to 88.5% than that fabricated by one-step PEO.
The pores formed by molten material ejection from the discharge channel and rapidly solidification during plasma electrolytic oxidation (PEO) act as passageways for corrosive particles. The overall porosity and pore shape, the inevitable features of ceramic coatings, are main factors that determines the corrosion resistance. In this work, we propose a novel approach that utilizes the advantages of graphene oxide (GO) to alter the pore shape and plasma discharge to effectively reduce the overall porosity. Simultaneously, the overall porosity and pore shape were deconstructed by X-ray microscopy. We found that the GO additive not only formed covalent bonds with the metal oxide, limiting the amount and distribution of molten oxide, but also changed the discharge form of the plasma reaction. The obtained coating exhibited an ultra-low surface porosity (1.10%), ultra-low overall porosity (2.11 vol%), and high aspect ratio (0.7–0.8), which are lowered for 94.8%, 90.9%, and increased for 66.9% than that of the traditional coating, respectively. The ultra-low porosity eliminates channels inside the coating and reduces the number of corrosive ions invading the substrate, resulting in superior corrosion resistance.
Keywords: Light alloys, Graphene oxide, X-ray microscopy, Ultra-low overall porosity, Corrosion resistance
Plasma sprayed fluoride and zinc doped hydroxyapatite coated titanium for load-bearing implants
Arjak Bhattacharjee, Amit Bandyopadhyay, Susmita Bose
Titanium (Ti) alloys show excellent fatigue and corrosion resistance, high strength to weight ratio, and no toxicity; however, poor osseointegration ability of Ti may lead to implant loosening in vivo. Plasma spraying of hydroxyapatite [HA, Ca10 (PO4)6 (OH)2] coating on Ti surfaces is commercially used to enhance osseointegration and the long-term stability of these implants. The biological properties of HA can be improved with the addition of both cationic and anionic dopants, such as zinc ions (Zn2+) and fluoride (F−). However, the hygroscopic nature of fluoride restricts its utilization in the radiofrequency (RF) plasma spray process. In addition, the amount of doping needs to be optimized to ensure cytocompatibility. We have fabricated zinc and fluoride doped HA-coated Ti6Al4V (Ti64) to mitigate these challenges using compositional and parametric optimizations. The RF induction plasma spraying method is utilized to prepare the coatings. Multiple parametric optimizations with amplitude and frequency during the processing result in coating thicknesses between 80 and 145 μm. No adverse effects on the adhesion properties of the coating are noticed because of doping. The antibacterial efficacy of each composition is tested against S. aureus for 24, 48, and 72 h, and showed that the addition of zinc oxide and calcium fluoride to HA leads to nearly 70 % higher antibacterial efficacy than pure HA-coated samples. The addition of osteogenic Zn2+and F− leads to 1.5 times higher osteoblast viability for the doped samples than pure HA-coated samples after 7-days of cell culture. Zn2+ and F− doped HA-coated Ti64 with simultaneous improvements in anti-bacterial efficacy and in vitro biocompatibility can find application in load-bearing implants, particularly in revision surgeries and immune-compromised patients.
Microstructure and properties of B + C + N ternary hardening layers on Q235 low-carbon steel prepared by plasma electrolysis
Bin Wang, Chuanli Gao, Xiaoyue Jin, Chi Xu, Jiancheng Du, Wenbin Xue
Ternary surface hardening layers were prepared on the Q235 low-carbon steel by plasma electrolytic borocarbonitriding(PEB/C/N) under constant voltage of 260–300 V for 30 min. The microstructure, phase components and hardness depth profiles of the B + C + N ternary hardening layers were examined. The ternary hardening layers were composed of a boride layer with single Fe2B phase and a transition layer. The thickness of modified boride layers on the PEB/C/N samples was about 10 μm, 15 μm and 22 μm at 260 V, 280 V and 300 V, respectively. The maximum hardness of boride layer was 2400 HV for the 300 V PEB/C/N sample. The surface free energy of bare Q235 steel and PEB/C/N samples at 260, 280 and 300 V were 41.084, 32.039, 26.906 and 25.726 mJ/m2, which were calculated on the basis of their contact angles for water and n-hexadecane. Furthermore, the hardening layers exhibited excellent corrosion behavior due to the improved hydrophobicity for the dense boride layer. The lowest wear rate of PEB/C/N sample at 300 V is about 2.0375 × 10−6 mm3/ N·m, which is only 1/15 of the bare Q235 steel, the ternary hardening treatment shows a better wear resistance than the bare Q235 steel.
Evidence of in-depth incorporation of carbon nanotubes in alumina layers grown by plasma electrolytic oxidation
C. Da Silva Tousch, J. Martin, G. Marcos, T. Czerwiec, G. Henrion
France, Germany
Incorporation of carbon nanotubes (CNTs) into ceramic layers during plasma electrolytic oxidation (PEO) is promising for direct synthesis of composite protective coating on lightweight metallic alloys. In the present study, complementary characterization techniques were used in order to definitively assess the presence of CNTs through the thickness of a PEO alumina coating formed in a silicate-based electrolyte containing dispersed multi-walled carbon nanotubes (MWCNTs). Cross-checked results helped in evidencing that MWCNTs are partially incorporated in the thickness of the PEO alumina coating, and more precisely through the porous outer sublayer. They were mainly found in the form of scaffolds that line the interior walls of pores. To a lesser extent, some individual MWCNTs were found interlocked in the fine grain structure of alumina. The analysis of the specific Raman bands of MWCNTs also highlighted that incorporation is associated with an alteration of the structural integrity of the MWCNTs. It was also established that the increase in the amount of dispersed MWCNTs results in a thicker but more porous CNTs-enriched PEO coating. Based on the collected results, some precisions regarding the incorporation mechanisms were proposed.
Preparation and characterization of the low-energy plasma electrolysis oxide coatings on Mgsingle bondLi alloy
Haoyue Tian, You Zhang, Xuelong Hao, Hongju Zhang, Wenjia Wu, Guolei Han, Zheng Dou, Yuankun Wei, Yuefei Zhang, Fei Chen
Plasma electrolytic oxidation (PEO) is a promising surface treatment method to improve the surface properties of light alloys. However, the high operating voltages led to significant power consumption and a burden on the grid, which limited its application. In this work, we employ a relatively low voltage (~100 V) in an organic-inorganic mixed electrolyte solution, and successfully achieve aa low energy plasma electrolysis oxidation (LEPEO) coating, enabling the reduction of the energy consumption of PEO on Mgsingle bondLi alloy. The energy consumption per unit volume (ECPUV) of the LEPEO process is 8.3 kJ·(dm2·μm)−1, which is approximate 57.0% energy consumption savings compared with the PEO process (19.3 kJ·(dm2·μm)−1, NaOH-Na2SiO3 electrolyte). Results show no remarkable difference between the two coatings in terms of morphologies, thickness, element type and distribution. The fracture process and corrosion protection performance of the coatings were evaluated by in-situ SEM tensile test and electrochemical impedance spectroscopy (EIS). The LEPEO coating only consists of MgO and amorphous SiOx, showing higher tensile strength, deformation displacement and better corrosion resistance compared with the PEO coating. The improved surface properties and lower energy consumption of LEPEO coatings will facilitate the application and development of PEO technology.
Deposition of copper coatings on internal aluminum contact surfaces by high-energy plasma spraying
Aleksandr Sivkov, Yuliya Shanenkova, YuliyaVympina, Dmitriy Nikitin, Ivan Shanenkov
China, Russian Federation
The deposition of functional coatings for various purposes on internal surfaces of devices and equipment is highly requested in a wide variety of production areas. In the electric power industry, there is a problem of combining a copper‑aluminum contact pair in the conical terminals of vacuum switches with the possibility of providing a low contact resistance and a high tightening torque or compression force, respectively. In this work, it is proposed to use high-energy plasma spraying for reliable combining copper and aluminum by Cu plasma spraying onto the inner conical Al contact surfaces. For this, a unique configuration of a high-energy plasma accelerator has been developed, which ensures producing and uniform spraying of Cu material in a single short-term working process (less than 1 ms). The dependence of the amount of deposited Cu material on the value of the specific supplied energy has been established to ensure the deposition of coating with a thickness not less than 40 μm and porosity from 3 to 8%. Also, the process implementation at increased supplied energy is found to provide the Cu and Al combination with a fourfold decrease in the contact resistance in comparison with the classical method of their connection. In addition, the high-energy plasma spraying results in forming an intermediate layer between copper coating and aluminum substrate containing intermetallic phases of Al4Cu6 and Cu3Al2. This layer is characterized by increased microhardness (up to 6–12 GPa) and provides high adhesion (more than 2000 MPa) due to hydrodynamic mixing of Cu and Al.
Deposition of silicon oxide films on silicon using HelixJet - an atmospheric-pressure plasma jet process below 100 °C
L. Rebohle, A. Quade, T. Schumann, D. Blaschke, R. Hübner, R. Heller, R. Foest, J. Schäfer, W. Skorupa
• Silicon oxide deposition by an atmospheric-pressure plasma jet process at 70 °C.
• Excellent interface to silicon right after deposition.
• Post-annealing transforms the silicon oxide bulk into silicon dioxide.
Silicon oxide films are widely applied for their superior dielectric, chemical and mechanic properties as well as for their resistance against reactive chemicals. Simultaneously, there is an increasing number of applications which demand a low deposition temperature. In this work, we compare the material properties of SiOx layers deposited on silicon at ca. 70 °C by HelixJet, an atmospheric-pressure plasma jet deposition (PA) using double helix electrodes, with those of SiO2 layers thermally grown or deposited by plasma-enhanced chemical vapour deposition. According to cross-sectional transmission electron microscopy, the interface between the PA oxide and the Si substrate is, similar to the case of thermal oxide, smooth with no apparent defects. In addition, the electrically active interface defect density is only one order of magnitude higher than that of the interface between thermal oxide and Si. In contrast, the bulk of the PA oxide significantly differs from that of thermal oxide. Right after deposition, the PA oxide contains carbon and hydrogen in a concentration of several at%, and the SiO2 network comprises several active centres. After furnace annealing, the formation of the SiO2 network is completed and the optical and electrical properties of the PA oxide converge to that of thermal oxide.
Keywords: Dielectric coating, Insulation, Corrosion protection, Silicon oxide, Atmospheric plasma source, Thin films
Direct Amination of Benzene with Molecular Nitrogen Enabled by Plasma-Liquid Interactions
Xia Xu, Xuyang Zhao, Dr. Jie Tang, Dr. Yixiang Duan, Dr. Yong-Hui Tian
Nitrogen fixation is industrially realized by mass production of ammonia, the principal intermediate nitrogen source for N-containing organic molecules. Instead, direct C−N bond formation from dinitrogen (N2) is of great interest but remains a challenge. Here, by virtue of unique plasma–liquid interactions, we developed an environmentally benign one-pot approach to directly couple benzene and N2, two naturally abundant yet chemically inert molecules, into value-added arylamines. Under the optimal conditions, an amination yield of 45 % was rapidly achieved, far better than the reported benzene amination efficiency using ammonia. A tentative reaction mechanism was proposed involving the long-lived N2 (A3urn:x-wiley:00448249:media:ange202203680:ange202203680-math-0001 ) and N2+ species, as evidenced by the key intermediates detected. With a deeper mechanistic understanding and by further optimizing the plasma reactor, the realization of cost-effective electrical amination of benzene with N2 could become reality.
Facet passivation process of high-power laser diodes by plasma cleaning and ZnO film
Yu Lan, Guowen Yang, Yuliang Zhao, Yuxian Liu, Abdullah Demir
China, Turkey
• A novel surface cleaning and passivation method is demonstrated for semiconductor devices with AlGaAs-containing facet structure.
• The removal of surface states was implemented by Ar-plasma cleaning and passivated by ZnO films.
• The method is applied to semiconductor lasers with comprehensive optimization, material characterization, device testing, and reliability results.
• We demonstrated 21 W laser output power and reliable operation by utilizing this method.
Passivation of dangling bonds at the cleaved mirror facet and its durability are fundamental features of semiconductor lasers to obtain reliable operation with a long device lifetime. The high non-radiative recombination activity of the surface states needs to be controlled to prevent the Fermi level pinning before the deposition of mirror coating materials. Here, we report the incorporation of plasma cleaning of the facet and ZnO film as a passivation layer for the fabrication of high-power semiconductor lasers. The Argon plasma cleaning process was investigated to eliminate surface contamination without damaging the cavity surface. The ZnO passivation films were systematically studied by varying the chamber pressure and sputtering power of the radio frequency (RF) sputter coating process. We obtained homogeneous and dense ZnO films with high surface quality and optical absorption coefficient of zero. By incorporating the optimum plasma cleaning and passivation layer parameters, GaAs-based laser devices with significantly improved catastrophic optical mirror damage (COMD) power were achieved. COMD threshold was increased from 11.9 W to 20.7 W. The life test results demonstrate no failure for facet cleaned and passivated devices for more than 500 h, confirming the long-term effectiveness of the process for actual device integration.
Keywords: Laser diodes, Facet passivation, High reliability
Chemical surface treatment mechanisms involved in a flamed polypropylene/polyurethane bonded interface: Toward a treatment by nitrogen plasma
Clémence Bernardi, Bérangère Toury, Emmanuel Chefdeville, Jules Galipaud, Michelle Salvia, Elise Contraires, François Virelizier, Réda Ourahmoune, Benjamin Surowiec, Stéphane Benayoun
France, Germany
• Flaming grafts different groups onto the PPGFL: ethers, ketones, acids, hydroxyls.
• Only hydroxyl groups react favorably with the isocyanate contained in the adhesive.
• Amines grafted by plasma react immediately and completely with isocyanate, unlike hydroxyls.
• The nitrogen plasma treatment is more robust than flaming in a humid environment.
Flaming treatments have been used at the industry level since the 1950s to improve the chemical reactivity of polyolefins. This treatment allows the grafting of polar functional groups onto the substrate to improve its chemical affinity with paints and adhesives, which is important in fields such as the automotive industry. Therefore, the primary purpose of this study is to identify which groups grafted by flaming treatments are involved in the adhesion between polypropylene long glass fibers (PPGFL) and polyurethane (PU) adhesives, with or without surrounding water. The effect of an alternative low-pressure nitrogen plasma treatment on the PPGFL/PU interface was then studied.
The main conclusions arising from the study of flaming are the following. X-ray photoelectron spectroscopy analyses revealed that the flaming treatment grafted four different chemical groups: hydroxyl, ether, ketone, and acid. Model reactions studied using nuclear magnetic resonance spectroscopy showed that only hydroxyl groups played a role in PPGFL/PU adhesion, as long as the environment was not saturated with water.
On the other hand, the low-pressure nitrogen plasma study showed that adhesion could also be obtained through amine groups. Model reactions showed that these groups were very reactive with the isocyanates contained in the adhesive; the reaction was complete and immediate. In addition, this particular reaction produced urea groups that were only slightly parasitized by water, which made the process more robust than flaming.
This study primarily aims to link the chemical mechanisms occurring at the interface with a macroscopic adhesion measurement of a bonded system. Further, kinetic monitoring allows the comparison of the reaction speed of each grafted group with the adhesive. Consequently, this makes it possible to determine the functional groups that are most important for adhesion and the most efficient and robust treatment method.
Keywords: Glass fiber/polypropylene, Polyurethane adhesive, Flaming treatment, Plasma treatment, Adhesive joints, Model reactions, NMR
Precise morphology control of in-plane silicon nanowires via a simple plasma pre-treatment
Zhaoguo Xue, Wanghua Chen, Xianhong Meng, Jun Xu, Yi Shi, Kunji Chen, Linwei Yu, Pere Roca i Cabarrocas
China, France
• A method to tailor morphologies of IPSLS SiNWs by a-Si:H layer treatments was developed.
• The morphology control of island-chain, zigzag, and straight geometries was demonstrated.
• Growth modes of SiNWs with different morphologies induced by Gibbs energy were analyzed.
• a-Si:H modified by plasma treatments was evidenced by hydrogen effusion measurements.
• The changes of bonded hydrogen and degree of disorder in a-Si:H were analyzed.
Silicon nanowires (SiNWs) are advantageous building blocks to explore a wide range of high performance nanoelectronics and photonics devices. In-plane solid-liquid-solid (IPSLS) SiNWs, grown by metal catalyst droplets that absorb hydrogenated amorphous silicon (a-Si:H) thin film to produce crystalline SiNWs, are particularly suitable for planar device fabrication and integration. Here, we explore a new growth control dimension to tailor the geometry of the in-plane SiNWs from island-chain to zigzag and to straight morphologies by using a simple plasma modification of the a-Si:H thin film precursor. This unique capability is due to fact that the Gibbs energy and bonding status of the a-Si:H layer can be largely modified by the plasma treatments at various substrate temperatures, which in turn have a huge impact on the growth balance condition of the SiNWs and consequently on their morphologies. These results highlight a facile and yet highly effective strategy to tailor the morphologyof in-plane SiNWs that will find important applications in fabricating nanoelectronic, sensor and logic devices.
Keywords: In-plane nanowires, Plasma treatment, a-Si:H Gibbs energy, Morphology,  engineering, In-plane solid-liquid-solid interface
Regeneration of the ciprofloxacin-loaded clinoptilolite by non-thermal atmospheric plasma
Barbara Kalebić, Nikola Škoro, Janez Kovač, Nevenka Rajić
Serbia, Slovenia
• Non-thermal plasma was used for the ciprofloxacin-containing zeolite regeneration.
• Plasma treatment was performed using a SDBD source at atmospheric pressure in air.
• Over 90% of adsorption capacity was restored after 5 adsorption/regeneration cycles.
• Plasma did not affect zeolite crystallinity nor textural properties.
• Plasma treatment proved to be a promising method for spent adsorbent regeneration.
Natural clinoptilolite (CLI) exhibited a high efficacy in ciprofloxacin (CIP) removal from aqueous solution by adsorption. However, the regeneration of the spent adsorbent was a challenge since the adsorption occurred via electrostatic interactions and ion-exchange reaction. Herein, the feasibility of non-thermal plasma (NTP) was studied for the regeneration of ciprofloxacin-containing clinoptilolite (CIP-CLI) in five successive adsorption/NTP regeneration cycles. The NTP treatments were performed using a surface dielectric barrier discharge (SDBD) operating at atmospheric pressure in air. Plasma discharge gap, sample mass, and electrode surfaces were varied to find optimal regeneration parameters. For the plasma source with an electrode surface of 37.2 cm2, the 2 mm electrode gap and 20 min of plasma treatment were found as optimal parameters (sample mass of 0.2 g). The plasma treatment did not affect clinoptilolite features which were concluded from a study of textural properties and powder X-ray diffraction (PXRD) analysis. X-ray photoelectron spectroscopy (XPS) showed a decrease of total carbon content with around 10% of carbon residual left on the surface. The CLI adsorption capacity can be regenerated to at least 90% of its initial capacity during the five successive cycles, showing the involvement of plasma reactive species in decomposition of adsorbed CIP.
Keywords: Adsorption, Clinoptilolite, Ciprofloxacin, Non-thermal plasma, Regeneration
Defect engineering of hexagonal boron nitride nanosheets via hydrogen plasma irradiation
Yuhan Xiao, Haiying Yu, Hongyan Wang, Xingrui Zhu, Le Chen, Wie Gao, Caiyun Liu, Hong Yin
• The luminous position of BNNSs in the PL emission spectrum can be regulated by controlling hydrogen plasma irradiation.
• The hydrogen plasma treatment on BNNSs can form B-O bonds while O substitutes N.
• The population of oxygen related defects play important role in remediation of nonradiative recombination pathways.
Atomic defects capable of hosting optically active centers in hexagonal boron nitride (h-BN) demonstrate a rich spin and optoelectronic physics that can be exploited for next-generation nanoelectronics and photonics. The precise controlling of these active defects is thus of particular importance. Here, we demonstrate the modulation of optoelectronic properties of atomically thin h-BN nanosheets (BNNSs) based on defect engineering via hydrogen plasma irradiation. Detailed studies resolve the generation of point defects and oxygen related defects uniformly in h-BN lattice after treated by hydrogen plasma. These tailored defects can lead to stable room-temperature luminescent emissions varying from 440 nm (ca. 2.8 eV) to 580 nm (ca. 2.1 eV) in BNNSs and multiple recombination channels. In addition, we show significant variations in both lattice structure and energy bandgap in BNNSs that can be tuned by the hydrogen plasma treatment. Density functional theory calculations verify the nature of the defect-induced optoelectronic behavior. These results are highly valuable for the fabrication of future two-dimensional semiconducting electronics, optoelectronics, and spintronics.
Keywords: Defect engineering, Hexagonal boron nitride, Plasma irradiation, Photoluminescence, Density function theory
Plasma-enabled synthesis of Pd/GO rich in oxygen-containing groups and defects for highly efficient 4-nitrophenol reduction
Tengda Zhang, Bo Ouyang, Xiuling Zhang, Guangqing Xia, Nantao Wang, Haoyu Ou, Long Ma, Pengxin Mao, Kostya (Ken) Ostrikov, Lanbo Di, Xin Tu
China, UK, Australia
• Effective catalytic reduction of 4-NP over Pd/GO catalysts was carried out.
• Plasma synthesis of highly efficient Pd/GO catalysts was demonstrated.
• Plasma synthesized Pd/GO showed the highest 4-NP reduction reported thus far.
• Plasma treatment retains more oxygen containing groups on the GO surface.
• Pd/GO-P was more active compared to that prepared with conventional methods.
Effective catalytic removal of 4-nitrophenol (4-NP) in industrial wastewater remains a significant challenge due to the lack of highly efficient and stable catalysts. Herein, we demonstrated a promising plasma method for the facile, ultra-fast and low-temperature synthesis of graphite oxide (GO)-supported palladium catalyst (Pd/GO-P) rich in oxygen-containing groups (OCGs) and defects with smaller Pd nanoparticles (NPs) for highly efficient 4-NP reduction. The plasma method limited the damage to the OCGs and retained more OCGs (mainly alkoxy and hydroxyl groups) on the GO surface. In addition, plasma treatment can increase the active sites and the density of GO surface defects. These OCGs and defects promoted the 4-NP adsorption and improved the catalyst dispersion in the aqueous solution of 4-NP, thereby enhancing the catalytic reduction performance. The Pd/GO-P catalyst showed the highest reduction of 4-NP reported thus far, with a concentration-normalized rate constant of 5576 min−1 g−1 L. This value was 51.6 and 20.5 times greater than that using Pd/rGO-H prepared by a traditional thermal reduction method and a commercial Pd/AC catalyst, respectively. This work opens the avenue of exploring the use of plasma for the rational design of supported Pd catalysts with superior performance for the reduction and recycling of 4-NP in wastewater.
Keywords: Cold plasma, Pd/graphite oxide, Oxygen-containing groups, Defects, 4-nitrophenol reduction
Low surface damage laser processing of silicon by laser-induced plasma etching (LIPE)
Robert Heinke, Martin Ehrhardt, Jens Bauer, Andriyo Lotnyk, Pierre Lorenz, Roy Morgenstern, Thomas Lampke, Thomas Arnold, Klaus Zimmer
• LIPE enables low-defect machining compared to traditional laser ablation processes.
• Little chemical as well as structural defects are formed due to LIP etching.
• TEM characterization shows no crystal defects by the etching process.
• Increase of reaction layer thickness with an increasing substrate temperature.
The precise surface machining of silicon by pulsed laser processing is challenging. Laser ablation enables direct patterning but causes numerous modifications of the surface and sub-surface region. Due to the increasing demand of precisely structured silicon surfaces in various fields, such as optics and micro-electronics and micro-fluidics, new laser-based ultra-precise surface machining techniques are required. Therefore, the recently developed laser-induced plasma etching process (LIPE) was studied in relation to chemical as well as structural modifications after the etching of single-crystalline silicon. For the studies, a fs-laser (775 nm, 150 fs, 1 kHz) with a pulse energy of maximum 750 µJ was focused to a CF4/O2 gas mixture at atmospheric pressure igniting a laser-induced plasma in front of the 〈1 0 0〉 Si sample. For comparison, a silicon surface was also structured by direct laser ablation.
The LIP etched surface, that is characterized by SEM, TEM, XPS- and Raman-spectroscopy, shows no melting features, no structural surface or subsurface defects and almost no chemical contamination from etching besides a 2 nm thick silicon oxyfluoride on top of the atomically ordered silicon. The comparison shows clearly that the severe structural and chemical modifications at laser ablation of silicon can be avoided enabling ultraprecise surface machining.
Keywords: Ultrashort pulsed laser, Laser-induced plasma, Plasma etching, Silicon Subsurface defects, LIPE
Nanosecond pulse-driven atmospheric-pressure plasmas for polymer surface modifications: Wettability performance, insulation evaluation and mechanisms
Xinglei Cui, Jiefei Shen, Yangyang Zhou, Xi Zhu, Renwu Zhou, Rusen Zhou, Zhi Fang, Patrick J. Cullen
China, Australia
• A nanosecond pulsed Ar/OMCTS plasma system is developed for epoxy resin fabrication.
• Multiple properties of EP are improved simultaneously by regulating OMCTS contents.
• Formation of shallow traps contributes to the increment of surface conductivity.
• Quantum chemical simulations verify the mechanism of improved electrical insulation.
Epoxy resin (EP) is one of the most widely-used insulating support materials in electrical power systems, with its insulating performance playing an important role in high-voltage engineering. In this study, a nanosecond pulse-driven Ar/Octamethylcyclotetrasiloxane (OMCTS) plasma jet is developed for fabricating nanocomposite dielectric materials to enhance their EP properties. It is demonstrated that the plasma-enabled polymerization effectively modifies the physical morphology and chemical composition of EP surfaces, where the surface roughness greatly increases with the deposition of less-polar silicon-containing films. Moreover, with an increased OMCTS carrier gas flow rate, the surface conductivity of the EP increases by two orders of magnitude, which is directly related to the appearance of shallow traps in the dielectric surface after Ar/OMCTS plasma treatment. Results show that the trap depth of the electron decreases from 1.21 to 0.99 eV post-treatment, with the OMCTS fragments becoming shallow trap points for charge detrapping and transportation processes. Moreover, the addition of a controlled amount of OMCTS increases the plasma discharge intensity, promotes silicon film deposition, and thus significantly improves the insulation and wettability performance, with higher flashover voltages and water contact angles (WCA). By contrast, excessive addition of OMCTS inhibits the plasma discharge due to the absorption and consumption of energetic electrons by OMCTS molecules. Quantum chemistry calculations are further developed to explore the mechanisms of plasma-induced surface modifications. Overall, the proposed plasma polymerization strategy offers a promising fabrication technique and provides guiding insights into the fabrication of nanocomposite dielectric materials in electrical engineering.
Keywords: Plasma polymerization, Electrical insulation, Flashover voltage, Super-hydrophobic surface, Nanosecond pulse
One-step atmospheric plasma-assisted synthesis of FeOOH and FeOOH/graphite high performance anode materials for lithium-ion batteries
Evgenii V. Beletskii, Mikhail A. Kamenskii, Elena V. Alekseeva, Alexey I. Volkov, Daniil A. Lukyanov, Dmitrii V. Anishchenko, Anton O. Radomtseu, Anastasiya A. Reveguk, Oleg V. Glumov, Oleg V. Levin
Russian Federation, Belarus
• A high-performance amorphous FeOOH-based anode is developed for Li-ion batteries.
• One-step atmospheric plasma-assisted synthesis of FeOOH composite with graphite.
• A capacity of ca. 750 mAh g−1 is sustained after 500 cycles at 0.3 A g−1.
• A capacity of ca. 550 mAh g−1 is sustained after 2000 cycles at 1.2 A g−1.
Iron oxide derivatives are promising materials for large-scale use as anode materials, owing to their natural abundance, inexpensiveness, and high theoretical capacity. Here, we synthesized amorphous urchin-like FeOOH nanoparticles and their graphite composite (FeOOH/Gr) in a one-step atmospheric plasma-assisted procedure and employed it in anode materials for Li-ion batteries. The obtained FeOOH nanoparticles are up to 300 nm in diameter with a needle thickness of about (3–10) nm, while FeOOH/Gr composite consists of graphite sheets covered with FeOOH needles. The FeOOH and FeOOH/Gr materials show excellent electrochemical performance as anode materials, with 633 mAh g−1 and 740 mAh g−1 at 0.3 A g−1 after 500 cycles, 353 mAh g−1 and 542 mAh g−1 at 1.2 A g−1 after 2000 cycles, respectively. By analyzing the state of the material at various stages of their life, we identify electrochemical milling as the performance-boosting process responsible for the 277% specific capacity increase during charge-discharge cycling after 50 cycles.
Keywords: Atmospheric plasma solution synthesis, Lithium-ion batteries, FeOOH anode material, Conversion metal oxide anodes
Photocatalytic hydrogen production using liquid phase plasma from ammonia water over metal ion-doped TiO2 photocatalysts
Sang-Chul Jung, Kyong-Hwan Chung, Jaewook Choi, Young-Kwon Park, Sun-Jae Kim, Byung-Joo Kim, Heon Lee
Republic of Korea
• Photocatalytic hydrogen production by liquid phase plasma was assessed in ammonia water.
• The effects of irradiation of the liquid phase plasma were evaluated over TiO2 photocatalyst.
• N/Fe/TiO2 was employed as a visible light sensitive photocatalyst with N and Ni codoping.
• The rate of H2 evolution from NH4OH by the reaction system was approximately 133 L/h.
• The rate of hydrogen evolution was significantly higher than that obtained by electrolysis.
Ammonia can be applied as a hydrogen carrier and used directly as a hydrogen production supply. In this paper, a technique for mass-producing hydrogen from ammonia water is proposed by applying a liquid phase plasma (LPP) discharge technique and a photocatalyst. In this reaction, N- and Fe ion codoped TiO2 (N/Fe/TiO2) photocatalysts were prepared and applied as a visible light-sensitive photocatalyst. N/Fe/TiO2 (NFT) had a similar crystal shape and size to anatase TiO2, but the surface was doped with metal ions. The bandgap of the NFT photocatalyst obtained from the spectrum measured by photoluminescence spectroscopy was approximately 2.4 eV. Nitrogen and Fe ions played a role in narrowing the gap between the conduction band (CB) and valence band (VB) of TiO2, effectively reducing the bandgap. In the decomposition reaction of ammonia water by LPP irradiation, the NFT photocatalyst showed the highest hydrogen evolution rate. The amount of hydrogen produced from ammonia water by LPP irradiation on the NFT photocatalyst was approximately 133 L/h. The hydrogen production rate obtained from ammonia water by the photocatalyst and LPP irradiation was significantly higher than that obtained by the ammonia electrolysis process.
Keywords: Photocatalytic decomposition, Liquid phase plasma, Hydrogen evolution, Modified TiO2 photocatalyst, Ammonia water
Nanosecond-pulsed microbubble plasma reactor for plasma-activated water generation and bacterial inactivation
Chenxi Man, Cheng Zhang, Haiqin Fang, Renwu Zhou, Bangdou Huang, Yuanzhong Xu, Xiaoxing Zhang, Tao Shao
In this study, a microbubble-enabled plasma reactor driven by a nanosecond-pulsed generator was developed to provide an effective means for transferring highly reactive plasma species into liquids for plasma-activated water (PAW) production. The physicochemical characteristics of PAW at different temperatures were evaluated, and the corresponding antimicrobial effects of PAW against Escherichia coli cells were investigated. Results show that the microbubble-enabled PAW at a lower temperature (10°C) had the highest antimicrobial activity, resulting in a 2.43 ± 1.02-log10 reduction of E. coli in PAW. The excellent energy efficiency of the total reactive oxygen and nitrogen species production in PAW is 10.37 g kW−1 h−1. Overall, this study provides much-needed insights into the microbubble-enabled plasma chemistries for optimizing the biochemical activity of PAW.
In-situ plasma treatment of tomato and rice seeds in-liquid to promote seed germination and seedling growth
Jiramet Mekarun, Anyarat Watthanaphanit
We propose an in-liquid plasma technique—Solution Plasma (SP)—to help enhance seed germination. Tomato and rice seeds are selected as representatives for dicot and monocot plant seeds, respectively. The effect of SP treatment time on the seed surface's chemical morphology and wettability is investigated. Compared to the untreated seeds, surface erosion of both seeds is observed. The surface wettability is also enhanced. The SP helps improve the seed germination rate and seedling growth of both seeds. We present the effect of plasma on seed germination in the aspect that SP can degrade polysaccharides—the main constituent of the seed coat. The formation of reactive oxygen species during treatment is supposed to be another reason for better seed germination.
Cold atmospheric plasma inhibits vesicle transport of human osteosarcoma cells visualized by super-resolution fluorescence microscopy
Cheng Zhu, Chong Chen, Jinsong Guo, Qun Wang, Junfeng Rao, Hui Li, Xiaodong Wu, Jie Zhuang
Vesicle transport plays a key role in cancer invasion and metastasis. As a promising cancer treatment modality, the impact of cold atmospheric plasma (CAP) on vesicle transport has been barely examined. In this study, super-resolution structured illumination microscopy (SIM) was employed to track the intracellular vesicles of osteosarcoma cells. Results indicated that CAP exposure could disintegrate vesicle clusters and individual vesicles. After 20 s of CAP treatment, the average velocity of intracellular vesicles decreased from 0.140 to 0.037 μm/s, while the 60 s maximum displacement declined from 7.76 to 3.26 μm. Significant inhibition of vesicle transport between osteosarcoma cells and human bronchial epithelium was observed after CAP treatment. These findings may shed some light on understanding CAP–cancer cell interactions.
Preparation of TiO2 nanoparticles via cathode glow discharge electrolysis and its photocatalytic performance in the degradation of methylene blue
Quanfang Lu, Juanlong Li, Bo Wang, Jie Yu, Xiaojuan Ma, Lijuan Cui, Yan Feng
TiO2 nanoparticles (NPs) were prepared by cathode glow discharge electrolysis in sodium fluoride solution, in which cetyltrimethyl ammonium bromide (CTAB) acted as a stabilizer, and a Ti foil and a Pt needlepoint served as the anode and the cathode, respectively. The structure, component, and morphology of TiO2 NPs were characterized. A possible preparation mechanism was proposed. In addition, the photocatalytic performance of TiO2 NPs was assessed through the degradation of methylene blue (MB). The results showed that TiO2 NPs with 12.7 nm particle size could be prepared at 500 V discharge voltage. CTAB, as a stabilizer, can diminish the agglomeration. The photocatalytic property of TiO2 NPs for the degradation of MB with 0.15% CTAB is markedly superior to that of TiO2 NPs without adding CTAB and commercial TiO2 NPs (P25).
A poly-diagnostic study of the shield gas-assisted atmospheric pressure plasma jet propagation upon a dielectric surface
Mehrnoush Narimisa, Yuliia Onyshchenko, Olivier Van Rooij, Rino Morent, Ana Sobota, Nathalie De Geyter
The significance of shield gases on atmospheric pressure plasma jet (APPJ) propagation over a horizontal dielectric surface using various diagnostic methods has been investigated. The obtained results imply that adding nitrogen as a shield gas only has an impact on the N2 reactive species generation, mainly close to the plasma effluent while argon shield gas can boost the optical emission intensity of all excited species, especially at distances further away from the plasma jet, which is in agreement with the observed length of the plasma propagation all over the surface. On the basis of the obtained results, the employment of a shield gas can improve the plasma jet efficiency to achieve the desired treatment effect on a flat surface.
Advancement of plasma electrolytic oxidation towards non-valve metals
Xueyuan Nie, Ran Cai, Chen Zhao, Jiayi Sun, Jingzeng Zhang, D.T.A. Matthews
Canada, the Netherlands
Discharge phenomena in electrolytes were discovered many decades ago. However, the research and development of plasma oxidation in electrolytes for surface engineering have only truly been actively performed in recent years, particularly stimulated by a review paper entitled Plasma Electrolysis for Surface Engineering published in 1999. Among plasma electrolysis processes, plasma electrolytic oxidation (PEO) caught the most attention from academic and industrial communities. However, PEO has been largely restricted to valve metals, such as Al, Mg and Ti and their alloys. This research intends to explore the current boundaries of the PEO process and extend it into non-valve metals. The paper therefore first describes the coating growth mechanisms in non-valve metals, which are different from the conventional PEO (conversion) process on valve metals. Particular emphasis is given to revealing details of the coating deposition behavior through direct observations and analysis of non-valve metallic substrates and their coatings formed at different timescales of the PEO process. Copper and ferrous materials are chosen as appropriate non-valve metal substrates and their coating properties in terms of mechanical, corrosion, thermal and electrical aspects are summarized. The results show that high hardness and adhesion strength, high corrosion resistance, good thermal and electrical insulation performances are achievable for PEO-derived coatings on non-valve metals. These properties also open doors for emerging applications, for example in electrical vehicles. Such applications are presented by reporting the coating application on an e-motor bearing and brake disc as two examples. Future research perspectives are discussed with a hope to stir a new wave of PEO research for non-valve metals as realized by the first review paper for the previous wave of plasma electrolysis research.
Keywords: Plasma electrolytic oxidation, Coatings, Friction, Thermal conductivity,
Electrical insulation
Active-screen plasma surface multi-functionalisation of biopolymers and carbon-based materials – An overview
Behnam Dashtbozorg, Xiao Tao, Hanshan Dong
Biopolymer and carbon-based materials have found widespread applications, spanning across different industries, including the medical, energy storage, wind energy, and aerospace sectors. The increasing popularity of both types of materials in industry has created a driving force for the enhancement of their properties to meet the current and future requirements. Active-screen plasma (ASP) has attracted much attention as a versatile and powerful surface engineering solution to meet these growing demands, owing to its treatment uniformity, remote plasma nature, capability for treating both electrically conductive and insulating materials, ability to functionalise surfaces, and the unique combined function of surface activation and deposition (CFAD). Through the introduction of moieties, modification of chemical bonding, change of morphology, and improvement in wettability on the treated surfaces, recent studies have demonstrated the ability for ASP treatments to enhance the biocompatibility of biopolymers. Moreover, ASP has also been tested (and ‘bespoke’ ASP techniques developed) for advanced carbon-based materials for tailored applications with promising property/performance enhancements, including a) enhanced wettability and interfacial shear strength for carbon fibres in polymer matrix composites, b) improved catalyst layer growth on carbon paper, c) improved electrical conductivity and capacitive performance for carbon nanofibers, and d) enhanced electric and electrochemical properties for graphene oxide.
This review evaluates the recent achievements and findings of ASP treatments performed on biopolymers and carbon-based materials from the Surface Engineering group in the University of Birmingham. The current status of ASP surface multi-functionalisation is communicated, along with the future research focus for materials with poor electrical conductivity and/or vulnerability to degradation.
Keywords: Active-screen plasma, Functionalisation, Biopolymers, Graphene oxide, Carbon fibre, Carbon nanofibre
Impact-sliding behavior of Ni-based coating prepared on tunnel boring machine disc cutter material produced using a plasma transferred arc welding process
Hao-ping Wang, Rui-xue Sun, Meng-qi Zhang, Bin Gou, Ji-liang Mo
The working condition of the disc cutter of the tunnel boring machine (TBM) is extremely harsh and is severely worn during the rock-cutting and tunneling process. Reducing the wear rate of the cutter and extending the service life of the cutter are essential to improving the economic costs and safety of the TBM. This article explores the feasibility and effectiveness of using surface coatings to improve the wear resistance of the cutter ring. NiCrBSi/WC coatings with different current intensities were prepared on the disc surface using plasma surfacing technology. The wear performance of the coating was evaluated using a bespoke impact-sliding device that fits the actual working conditions, and the wear mechanism was studied in detail. According to the “tadpole-like” wear scar characteristics of the coating after the impact-sliding wear experiment, the wear scar zone can be divided into two regions: the impact region and the sliding region, which are consistent with the actual wear characteristics of the cutter ring. In addition, the wear behavior of the coating noticeably changed under each experiment parameter, and the evolution process of the impact-sliding wear of the gage cutter at each position can be well reproduced. When the impact angle was 45°, the wear depth and wear volume of the coating were significantly smaller than those of the uncoated samples. This is mainly due to the metallurgical bond between the Ni-based alloy zone (binder phase) and the spherical WC particles (hard phase) on the surface of each specimen. When impacted by the tribo-ball, the WC particles can undergo plastic deformation and relaxation through the Ni-based alloy zone under the applied force, thereby obtaining excellent impact and sliding resistance. When the impact angle was 60°, the impact dominates, causing the impact force to increase. Furthermore, compared with the uncoated specimens, the wear depth and wear volume of the coated specimens significantly increased, indicating that the anti-impact ability was seriously degraded in such situation. In summary, the powder composition and preparation process parameters should be reasonably selected according to the impact angle, and the impact-sliding wear experiment can effectively evaluate the impact and sliding wear performance of different coatings. This approach has an important directive function in the promotion and application of cutter ring coatings.
Plasma-based Surface Engineering: Celebrating the research career of Professor Allan Matthews, FREng
Adrian Leyland, Claus Rebholz, Jochen M. Schneider, Michael Stüber, Aleksey Yerokhin, The Editorial and Publishing Team – Surface & Coatings Technology
UK, Cyprus, Germany
Modification of physicochemical properties and bioactivity of oxide coatings formed on Ti substrates via plasma electrolytic oxidation in crystalline and amorphous calcium phosphate particle suspensions
Vladlens Grebņevs, Katarzyna Leśniak-Ziółkowska, Marta Wala, Mateusz Dulski, Şahin Altundal, Aleksandrs Dutovs, Līga Avotiņa, Donāts Erts, Roman Viter, Arturs Vīksna, Wojciech Simka
Latvia, Poland
• Particle crystallinity specifically affected surface topography and bioactivity.
• Amorphous particles led to the higher content of calcium phosphates in the surface.
• Both particle types showed similar incorporation pattern for Ti and TAV substrates.
• Particle crystallinity is a new potential instrument for adjustment of PEO coatings.
One way to improve characteristics of oxide coatings prepared by plasma electrolytic oxidation (PEO) method in suspensions lies in variation of solid particle properties. In this study, the effect of particle crystallinity on different physicochemical properties and bioactivity of coatings prepared on Ti and Ti6Al4V substrates was studied, and repeatability of resulting characteristics was assessed depending on selected substrates. PEO was performed in direct current mode at a voltage of 350 V in electrolytes containing 0.1 M KH2PO4 and 100 g.L-1 of stoichiometric crystalline hydroxyapatite or amorphous tricalcium phosphate particles with average size of ∼ 450 nm. Series of measured physical parameters included coating thickness, as well as surface wettability, roughness and topography. Surface and cross-sectional chemical composition was studied by Raman and EDX spectroscopy, while bioactivity was evaluated with simulated body fluid tests. Results showed specific influence of particle crystallinity on surface morphology and repeatable particle incorporation pattern depending on the substrate utilized. It was found that amorphous particles lead to the increased amount of incorporated calcium phosphate phases followed by improved coating bioactivity and possible explanation of this phenomenon was suggested. Variation of particle crystallinity was proposed as a new potential instrument for the adjustment of PEO coating properties.
Keywords: Plasma electrolytic oxidation, Particles, Crystallinity, Amorphous calcium, phosphate, Hydroxyapatite, Bioactive coatings, Suspensions, Titanium alloys
Structural modifications induced by ultrasonic vibration during plasma spray deposition Ni coating on Al substrate
Zhanliang Li, Yuxing He, Tie Liu, Baijun Yang, Pengfei Gao, Jun Wang, Qiang Wang
People's Republic of China
In this study, a 28 kHz ultrasonic vibration was applied to the Al substrate during plasma spraying of Ni coatings. The microstructure, mechanical properties, and wear resistance of the coatings were investigated. With application of the ultrasonic vibration, the bonding between splats increased and porosity of the coatings decreased from 6.2 % to 3.4 %. Grain size in the coatings also decreased. The hardness and Young's modulus of the coating increased from about 2.8 GPa and 111.5 GPa to about 4.4 GPa and 183.4 GPa, respectively, by application of the ultrasonic vibration. The width and depth of the wear trace and the wear rate of the Ni coating sprayed using ultrasonic vibration also significantly decreased. These results are ascribed to the effects of acoustic pressure and acoustic streaming, cavitation, and heating of the ultrasonic vibration that promote wetting and filling ability and affect solidification of molten Ni droplets during the spraying process.
Tribocorrosion properties of plasma nitrided, Ti-DLC coated and duplex surface treated AISI 316L stainless steel
Y. Uzun
In this study, the tribocorrosion behavior of untreated, plasma nitrided (450 °C–4 h), Ti-DLC coated and duplex treated (Ti-DLC coating after nitriding) AISI 316L stainless-steel were investigated. The plasma nitriding process was carried out in a gas mixture of 80 % H2 and 20 % N2 at 450 °C for 4 h. A titanium (Ti) interlayer was coated on the substrate for Ti-DLC coating. Then, a diamond-like carbon (DLC) film was grown on the Ti interlayer. As a result of the study, it was determined that the damage caused by the wear mechanism was much more than the corrosive effects. In general, thanks to the layers formed on the surface, the wear and tribocorrosion performance of the treated samples increased compared to the untreated sample. It was observed that the best tribocorrosion resistance among the treated surfaces was obtained in the duplex surface-treated sample.
Effects of silica nanoparticles addition on formation of oxide layers on Alsingle bondSi alloy by plasma electrolytic oxidation: The origin of stishovite under ambient conditions
Mikhail M. Krishtal, Alexander V. Katsman, Anton V. Polunina
Russian Federation, Israel
The effects of different amorphous silica nanoparticles (NPs) with average particle size of 48 nm – n−SiO2(48) and 100 nm – n−SiO2(100) added to the electrolyte under plasma-electrolytic oxidation (PEO) of Alsingle bondSi alloy 361.0 (9.8 wt. % Si) on the oxide layers structure, phase composition and properties were investigated. Unexpected formation of high pressure (HP) SiO2-phase – stishovite was detected in the oxide layers formed using n−SiO2(48) under ambient conditions. This HP-phase was not detected while using n−SiO2(100) and the electrolyte without nanoparticles. It was found that the addition of the n−SiO2 resulted in significant increase in the oxidizability, and, accordingly, in the thickness of the PEO-formed oxide layers, their wear resistance (by ~1.5 times) and thermal resistivity (by ~4 times) as compared to the oxide layers obtained without NPs. It also resulted in crystallite size reduction and an increase of the amorphous phase fraction, both effects are more pronounced while using n−SiO2(48) despite the equal initial concentrations of the nanopowders in the electrolyte (3 g/l). To explain these effects, a novel approach to the NPs/oxide layer interaction and the corresponding quantitative model were introduced. The interaction was considered as the colliding with the rigid oxide layer surface of rapidly moving charged NPs accelerated by electric field in the vapour-gas bubbles (VGB) formed in porous channels prior micro-arc discharge. During elastic/inelastic collision, the particle kinetic energy transforms to compressive strain energy, heating of the particle and/or to kinetic energy of the bounced off particle providing different interaction scenarios depending on the particle size. The developed model makes it possible to predict the HP SiO2-phase formation, an increase in the fraction of amorphous phases and reduction in the crystallite size in the PEO-formed layers in the presence of NPs, which can result in improvement of protective and mechanical properties of the layer.
Effect of energy distribution on the machining efficiency and surface morphology of Inconel 718 nickel-based superalloy using plasma electrolytic polishing
Chuanqiang Zhou, Ning Qian, Honghua Su, Zhao Zhang, Wenfeng Ding, Jiuhua Xu
PR China
Inconel 718 nickel-based superalloys are important aerospace materials whose precision surfaces have important applications in key aerospace components. It is significant and challenging to obtain precise surfaces of Ni-based superalloys with high efficiency and quality. Plasma electrolytic polishing (PEP) is a rapidly developing high-efficiency and high-quality metal surface polishing process and is an application process for obtaining precise surfaces of superalloys. Research on the influence of vapor gaseous envelope (VGE) behaviors and the evolution process on the polishing effect remain insufficient, although the behavior of the VGE affects the machining efficiency and surface morphology of the superalloy. In this study, the evolution process of the VGE was analyzed and simulated using experimental and simulation methods. The effects of the VGE behavior characteristics on the surface morphology and polishing efficiency were explained from the perspective of energy distribution. The experimental results showed that a discontinuous and fluctuating VGE favored the removal of materials and finishing of the workpiece surface. When the voltage exceeded 400 V, the heat flux at the gas-liquid interface exceeded the critical heat flux, and the VGE evolved from bubbles to a vapor film which deteriorated the polishing effect. Finally, the voltage range for obtaining the precision surface of the superalloy was 250–350 V, while the temperature range of the electrolyte was 70–85 °C.
Plasma treatment of cellulose: investigation on molecular changes using spectroscopic methods and chemical derivatization
Sven Gerullis, Andreas Pfuch, Oliver Beier, Björn‑Sten‑Mark Kretzschmar, Mario Beyer, Steffen Fischer
One interesting and sustainable method for the treatment of a large variety of surfaces is the atmospheric plasma technology. The use of plasma
technologies can lead to physicochemical interactions between the plasma and the substrate material. Such interactions can result in a wide variety of molecular
(creation of functional groups, radical formation, microscopic (roughness, etching, reduction of wood extractives and macroscopic (wettability, liquid penetration, surface energy) modifications of the substrate surface. Aim of this study was to take a deeper look on occurring molecular changes of cellulose by using spectroscopic methods. The treated materials were analyzed by Attenuated Total Reflection – Fourier Transform Infrared Spectroscopy (ATR-FTIR) and
X-ray Photoelectron Spectroscopy (XPS). The evaluation of XPS detail-spectra and their separation into sub-spectra can be used to describe general changes
in the chemical bonding states. For a better differentiation of the species produced by the plasma at the surface of the materials, specific derivatization reactions and subsequent analysis of the reaction products formed during derivatization are carried out in order to distinguish the different states of species that are present. The formation of oxygen-containing, polar functionalities on cellulose by plasma treatment could be confirmed. Chemical derivatization of cellulose in connection with subsequent XPS measurements showed the formation of O = C bonds in connection with the reduction of OH groups. In addition, the formation of carbonate groups on cellulose appears to be possible as a treatment effect, for which a corresponding reaction mechanism is discussed.
Keywords: Atmospheric pressure plasma, cellulose, XPS, Chemical derivatization, Ozone
Cold atmospheric pressure plasmas applications in dentistry
Wen Zhou, Xiuqing Wang, Xiaojing Huang
Cold atmospheric pressure plasmas (CAP) is widely used for various therapeutic applications in health care. With the enormous progress in the understanding of plasma physics and development of plasma devices, the application of CAP is greatly promoted in dentistry. The reactive chemical species and electromagnetic radiation generated by CAP can activate and control various biochemical procedures. Therefore, CAP showed promising usage in surface modification of dental materials, biofilm removal, disinfection, endodontic therapy, periodontitis treatment, wound healing, and head and neck cancer control. Therefore, the objective of the present review is to present recently published studies on CAP in dentistry.
Synergistic cytotoxicity from cold atmospheric plasmaand ultrasound in glioma cells
Andressa M. Aguiar de Carvalho, Laurence Scally, Brijesh Tiwari, Patrick J. Cullen, James F. Curtin
Ireland, Australia
The aim of this study was to investigate whether sonoporation of cancer cellsusing ultrasound (US) technology could enhance the anticancer effects of coldatmospheric plasma. US‐induced transient sonoporation of cancer cells with littleto no cytotoxicity observed onthe cell lines tested. Synergisticeffects of US were observedwhen  combined  with  bothdirect and indirect cold atmo-spheric plasma. These cytotoxiceffects  were  dependent  onreactive species production. Tothe best of our knowledge thatis the first time that the effects of those two nonthermal technologies wereevaluated in cancer cells, demonstrating a promising combined strategy forcancer therapies, particularly for thosewith penetration limitations, such asglioblastoma.
Keywords: cavitation, glioblastoma, nonthermal plasma, plasma, sonoporation
In-liquid plasma synthesis of iron–nitrogen-doped carbon nanoflakes with high catalytic activity
Hiroki Kondo, Ryo Hamaji, Tomoki Amano, Kenji Ishikawa, Makoto Sekine, Mineo Hiramatsu, Masaru Hori
Flake-shaped carbon nanomaterials with nitrogen (N) and iron (Fe) addition, so-called carbon nanoflakes (CNFLs), were synthesized by the in-liquid plasma using two different kinds of additive agents, such as hemin and iron (II) phthalocyanine (FePc). According to scanning electron microscopy images and Raman spectra, CNFLs with a size of at least 100 nm order were formed regardless of types of additive agents, and crystallinity of six-membered ring structures was improved as additive agents increased. Photoelectron spectra showed that pyridinic N contents increased from 1.05% to 2.02% with increasing FePc, while those decreased from 0.34% to 0.14% with hemin. In the oxygen reduction reaction, onset potential values also increased from 0.71 to 0.79 eV with increasing FePc, while those decreased from 0.60 to 0.47 eV with hemin. These results suggested that the catalytic activity of CNFLs was effectively improved by the increase of pyridinic N by the in-liquid plasma synthesis with FePc. In contrast, the electron transfer numbers reached 3.81 when hemin increased, although those were less than 2.88 in the cases using FePc. These results mean that the in-liquid plasma synthesis method of CNFLs using FePc has the potential to further improve its catalytic activity.
Does plasma jet sintering follow an Arrhenius-type expression?
Nazli Turan, Mortaza Saeidi-Javash, Yanliang Zhang, David B. Go
Atmospheric pressure, ambient temperature plasma jets have become a promising candidate for material processing in parallel with developments in additive manufacturing. Recent work has shown that plasma jets can be used to sinter printed nanoparticles at temperatures much lower than typically required for conventional thermal sintering. Here, we conduct a mechanistic study on plasma jet sintering that correlates specific energy input with the electrical conductivity of printed silver films after sintering. Increasing the specific energy input accelerated the sintering process following an Arrhenius-like exponential trend across a large range of conditions, including both helium and argon plasma jets. Although an exponential relationship is also found with the plasma heated substrate temperature, independent studies indicate that heating is not the primary mechanism. These results suggest there is a general behavior that couples the plasma jet with the surface.
Organosilica coating layer prevents aging of a polymer with intrinsic microporosity
Jens Rubner, Leonie Stellmann, Ann-Kathrin Mertens, Maik Tepper, Hannah Roth, Lara Kleines, Rainer Dahlmann, Matthias Wessling
This study tracks the physical aging behavior of coated and uncoated ultra-thin poly(1-trimethylsilyl-1-propyne) (PTMSP) films on silicon wafers based on the refractive index using ellipsometry. The measured refractive index directly correlates with the free volume and hence the physical aging progression. Plasma-enhanced chemical vapor deposition (PECVD) creates coatings with different thicknesses and oxidation degrees onto PTMSP films. Compared to uncoated PTMSP films, the PECVD-coated films show a reduction of the refractive index increase of more than two orders of magnitude for less than 10 nm thin SiOx coatings. In contrast, SiOCH films show only a minor impact. The results reveal the superior physical aging behavior of PECVD-coated films compared to untreated PTMSP films.
Keywords: aging, ellipsometry, hexamethyldisiloxane (HMDSO), plasma‐enhanced chemical vapordeposition (PECVD), thin films
Plasma deposited high surface area‐activated carboncoatings: Theory combining particle generation,aggregation and deposition explains microstructure
Clara T. Tran, Michael Raco, Louis M. Casey, David R. McKenzie
High surface area carbon coatings are produced by plasma‐enhanced chemicalvapour deposition using a high‐voltage dielectric barrier discharge underconditions where aggregates are formed in the plasma and the growing coatingis  subjected  to  plasma  immersion  ion  implantation.  We  extend  theSmoluchowski aggregation theory to include the continuous production ofmonomers to explain the observed microstructure of the coatings as a functionof the pressure of deposition. The larger particles show evidence of theaccretion of monomers on their surfaces with characteristic voids resultingfrom island growth. The coatings are subjected to plasma immersion ionimplantation   using   high‐voltage pulses that create radi-cals for binding biomolecules.The increased surface area bythe presence of the aggregatedparticles binds a significantlyhigher amount of protein thansmooth   coatings,   makingthem  potentially  useful  forelectrodes,  biosensing  anddrug delivery.
Keywords: dielectric barrier discharge, high surface area coating, plasma aggregation,
Effect of crosslinker on the wettability and mechanical properties of hydrophobic coatings deposited via atmospheric pressure plasma
Camilo Rendon-Piedrahita, Kamal Baba, Robert Quintana, Julien Bardon, Joanna Borek-Donten, Régis Heyberger, Patrick Choquet
Hydrophobic coatings based on dodecyl acrylate (DOCA) and perfluorodecyl acrylate (PFDA) have been generated via “postdischarge” atmospheric pressure plasma deposition. These coatings exhibit a water contact angle (WCA) of around 125° but are accompanied by poor mechanical strength. To improve this property, two different types of chemical crosslinkers, that is, hexanediol methacrylate (HDMA) and hexanediol diacrylate (HDA), are incorporated into the precursor mixture. After plasma polymerization, both coatings with crosslinkers admixture show different wettability behavior. The addition of HDMA reduces the WCA while increasing the mechanical strength, while the addition of HDA retains the initial WCA magnitude while also increasing the mechanical strength. These changes are related to variations of the surface free energy (SFE) and topography of the plasma coatings.
Keywords: atmospheric pressure plasma, crosslinkers, hydrophobicity, mechanical strength, plasma polymer
Characterizing the Biological Effects of Plasma-Activated Physiological Saline
Тatyana Pavlik, Namik Gusein-Zade
Plasma Medicine, 12(1):1–11 (2022)
Plasma medicine, an actively developing medical field, comprises both the direct treatment of biological surfaces and the effect of low-temperature plasma on solutions used in medicine. In this study, the cyto- and genotoxic properties of physiological saline treated with cold plasma were investigated. Mononuclear leukocytes obtained from notionally healthy donors and cells of two blood cancer patients were used as the target. The cyto- and genotoxic
effects of the plasma-treated solution were recorded according to the treatment time. No sig nificant selectivity was recorded for the investigated cell lines. The use of cold plasma–treated physiological saline as a nonspecific cyto- and genotoxic agent exhibiting a prolonged effect is proposed.
Keywords: cold atmospheric plasma, plasma treated solution, leukocytes, leukemia
Transient Spark Coating for Dentistry
M. E. Bergmann, Tobias Wieland, V. Straub, F. Engesser, E. Buerkin, M. J. Altenburger, G. A. Urban, Loïc Ledernez
Plasma Medicine, 12(1):13–25 (2022)
Cold atmospheric plasma jets have started to demonstrate their potential in vari ous medical applications. Those devices generate a plasma using noble gases or air and are used to disinfect the inflamed tissues and even trigger natural healing processes. We are developing a plasma jet device with the purpose of depositing in situ a coating on implant materials that reduces bacteria attachment. The coating is not antimicrobial which is regarded as controversial.
This new treatment shall offer physicians a possibility to control reinfection caused or triggered by medical implants. In this work, we present the method as well as first evaluation results. They show how the precursor and gas carrier influence the coating properties and allow to tune their surface properties. The adhesion of the coatings to the substrate was excellent, while the adhesion of Escherichia coli on the coated substrate was significantly reduced. Those preliminary results show the potential of this atmospheric plasma jet–based coating technique.
Keywords: plasma jet deposition, implant coating, transient spark, plasma polymerization
dental implant, dentistry atmospheric pressure, disinfection, infection control
Effects of Plasma-Activated Water on Soybean and Wheat: Germination and Seedling Development
Rajesh Prakash Guragain, Hom Bahadur Baniya, Niroj Banset, Suman Prakash Pradhan, Santosh Dhungana, Ganesh Kuwar Chhetri, Gobinda Prasad Panta, Binita Sedhai, Bikash Shrestha, Shreya Shrestha, Deepesh Prakash Guragain, Ujjwal Man Joshi, Bishnu Prasad Pandey, Deepak Prasad Subedi
Plasma Medicine, 12(1):27–43 (2022)
The goal of this study is to explore how water treated using plasma affects the germination and growth of soybean and wheat seedlings. Deionized water (DIW) was exposed to a gliding arc discharge (GAD) for 5 and 10 min to create plasma-activated water. DIW revealed significant changes in physical properties as well as chemical parameters after its treatment with plasma. The germination rate (growth metrics, such as shoot/seedling length, imbibition rate of seeds, and vigor indices), increased when plasma-treated water was used for irrigation purposes.
In conclusion, when plasma-treated water is used for irrigation, a better result yield in germination is acquired.
Keywords: plasma agriculture, deionized water, gliding arc discharge, plasma-activated water, reactive oxygen and nitrogen species, soybean, wheat
Pathways of organic micropollutants degradation in atmospheric pressure plasma processing–A review
B. Topolovec, N. Škoro, N. Puаč, M. Petrovic
Spain, Serbia
• Different applications of several types of non-equilibrium non-thermal plasma sources for wastewater treatment.
• Degradation mechanisms of organic micropollutants induced in plasma treatments.
• Challenges and future important steps in research for application of plasma technology in wastewater processing.
Concern of toxic compounds and their, potentially more harmful degradation products, present in aquatic environment alarmed scientific community and research on the development of novel technologies for wastewater treatment had become of great interest. Up to this date, many papers pointed out the challenges and limitations of conventional wastewater treatment and of some advanced oxidation processes. Advanced technologies based on the use of non-equilibrium or non-thermal plasma had been recognized as a possible solution for, not only degradation, but for complete removal of recalcitrant organic micropollutants. While previous review papers have been focused on plasma physics and chemistry of different types of discharges for few organic micropollutants, this paper brings comprehensive review of current knowledge on the chemistry and degradation pathways by using different non-thermal plasma types for several micropollutants’ classes, such as pharmaceuticals, perfluorinated compounds, pesticides, phenols and dyes and points out some major research gaps.
Keywords: Organic micropollutants, Non-equilibrium/non-thermal plasma types, Degradation pathways, Removal, Advanced oxidation technologies, Novel wastewater treatment procesess
Degradation of Bacterial Antibiotic Resistance Genes during Exposure to Non-Thermal Atmospheric Pressure Plasma
I. Courti, C. Muja, T. Maho, F.P. Sainct, P. Guillot
France, Germany
Bacterial resistance to antibiotics has become a major public health problem in recent years. The occurrence of antibiotics in the environment, especially in wastewater treatment plants, has contributed to the development of antibiotic-resistant bacteria (ARB) and the spread of antibiotic resistance genes (ARGs). Despite the potential of some conventional processes used in wastewater treatment plants, the removal of ARB and ARGs remains a challenge that requires further research and development of new technologies to avoid the release of emerging contaminants into aquatic environments. Non-thermal atmospheric pressure plasmas (NTAPPs) have gained a significant amount of interest for wastewater treatment due to their oxidizing potential. They have shown their effectiveness in the inactivation of a wide range of bacteria in several fields. In this review, we discuss the application of NTAPPs for the degradation of antibiotic resistance genes in wastewater treatment.
Keywords: wastewater treatment technologies, plasma, ARB, ARGs, HGT
Experimental and modeling studies of the plasma chemistry in a humid Ar radiofrequency atmospheric pressure plasma jet
J. Jiang, V.S.Santosh K. Kondeti, G. Nayak, Peter J. Bruggeman
While humid atmospheric pressure plasmas are extensively modeled, reaction set validation for these conditions remains limited. We present a detailed comparison of a modelling and experimental study with a goal to elucidate the plasma chemistry in a humid Ar radiofrequency-driven atmospheric pressure plasma jet. A large group of species including radicals (H, OH, O, HO2) and long-lived species (H2, O2 and H2O2) in the jet effluent was experimentally quantified by molecular beam mass spectroscopy (MBMS). MBMS measurements of H2O2, OH and H were validated by direct comparison with a liquid phase colorimetric measurement, laser-induced fluorescence (LIF) and two-photon absorption LIF respectively. While an excellent agreement was found for OH and H2O2 by both techniques, a significant difference was found for H and shown to be due to boundary layer effects at the MBMS sampling substrate. The measured O, OH, HO2 and H2 are in good agreement with the plug model while H and O2 were underestimated and H2O2 was overestimated by the model. The accuracy of both the used reaction set and the diagnostics, as well as the observed discrepancies between the modeling and experimental results, are critically assessed. The results presented in this work enable us to identify further data needs for describing H2O vapor chemistry in low-temperature plasmas.
Simultaneous degradation of p-nitrophenol and reduction of Cr (VI) in one step using microwave atmospheric pressure plasma
Chaoxia Zhao, Li Xue, Hongxiao Shi, Wenqi Chen, Yu Zhong, Yi Zhang, Yanping Zhou, Kama Huang
• Simultaneous oxidation and reduction were realized by electrodeless microwave plasma.
• Over 90% of PNP and Cr(VI) was removed simultaneously after 15 min of treatment.
• Mutual promotion of Cr(VI) and PNP for the removal was revealed to be distinctive.
• The reductive intermediates of PNP play a significant role in the reduction of Cr(VI).
• The promotion of Cr(VI) reduction by PNP is irrespective of pH value.
Different physicochemical properties between Cr(VI) and phenolic compounds pose serious challenges for the effective treatment of co-contamination. This study developed an electrodeless high-flow microwave atmospheric plasma jet for the single-step simultaneous degradation of p-nitrophenol (PNP) and reduction of Cr(VI). Following a 15 min treatment with microwave atmospheric pressure plasma, the removal efficiency of Cr(VI) and PNP reached 97.5% and 93.6%, respectively, whereas that of total organic carbon reached 30.2%. Adding PNP to the solution significantly improved Cr(VI) reduction, whereas PNP degradation increased slightly with Cr(VI). The results indicate that the PNP intermediates significantly affected Cr(VI) reduction. Additionally, long-lived H2O2 and short-lived 'H aided the reduction of Cr(VI) during plasma treatment. The addition of hydroxyl scavengers during treatment implied that 'OH was largely responsible for PNP oxidation. High-performance liquid chromatography–mass spectroscopy (HPLC-MS) revealed that PNP intermediates, including p-nitrocatechol and 5-nitrobenzene-1,2,3-triol, function as Cr(VI) reductants. On the basis of the examined intermediate products, the potential PNP degradation pathway was investigated. The factors that could influence simultaneous dehgradation and reduction, including solution pH, gas velocity, and distance between the plasma outlet and the water surface were researched. Low pH supports Cr(VI) reduction, and the promotion of PNP for Cr(VI) reduction applies to all pH values. The degradation of PNP is insensitive to pH values with or without Cr(VI). The optimal gas velocity for PNP degradation and Cr(VI) reduction was revealed to be 6 L/min. The simultaneous removal of PNP and Cr(VI) benefits from a shorter distance between the plasma outlet and the water's surface.
Keyword: Environment-friendly technology, Electrodeless atmospheric plasma, Complex wastewater, Mutual effects, Reductive intermediates
Plasma dynamics, instabilities and OH generation in a pulsed atmospheric pressure plasma with liquid cathode: a diagnostic study
Yuanfu Yue, V. S. Santosh K. Kondeti, Nader Sadeghi, Peter J. Bruggeman
USA, France
While plasma–liquid interactions have been an important focus in the plasma research community, the impact of the strong coupling between plasma and liquid on plasma properties and processes remains not fully understood. In this work, we report on the impact of the applied voltage, pulse width and liquid conductivity on the plasma morphology and the OH generation for a positive pulsed DC atmospheric pressure plasma jet with He–0.1% H2O mixture interacting with a liquid cathode. We adopted diagnostic techniques of fast imaging, 2D laser induced fluorescence of OH and Thomson scattering spectroscopy. We show that plasma instabilities and enhanced evaporation occur and have a significant impact on the OH generation. At elevated plasma energies, it is found that the plasma contracts due to a thermal instability through Ohmic heating and the contraction coincides with a depletion in the OH density in the core due to electron impact dissociation. For lower plasma energies, the instability is suppressed/delayed by the equivalent series resistor of the liquid electrode. An estimation of the energy flux from the plasma to the liquid shows that the energy flux of the ions released into the liquid by positive ion hydration is dominant, and significantly larger than the energy needed to evaporate sufficient amount of water to account for the measured H2O concentration increase near the plasma–liquid interface.
Hydrophilization of polytetrafluoroethylene using an atmospheric-pressure plasma of argon gas with water–ethanol vapor
Sukma Wahyu Fitriani, Shingo Ikeda, Masahiko Tani, Hideki Yajima, Hiroshi Furuta, Akimitsu Hatta
• Plasma treatment of argon with water–ethanol vapor is promising method to improve polytetrafluoroethylene wettability.
• Hydrophilic surface-finish of polytetrafluoroethylene was achieved after plasma treatment.
• Ethanol concentration and treatment duration influenced the mechanism of polytetrafluoroethylene surface modification.
This paper presents an approach to improve the surface wettability of polytetrafluoroethylene (PTFE) using an atmospheric-pressure plasma of argon gas with water–ethanol vapor. Plasma is generated by the dielectric barrier discharge of argon gas bubbled into a water-ethanol solution. Quadrupole mass analysis revealed that the plasma promoted the decomposition of ethanol and production of H2, CH4, and CO, which saturated at low ethanol concentrations. The modified PTFE surface was strongly influenced by the ethanol concentration in the solution and treatment time. Plasma treatment with 3%, 5% and 9% ethanol resulted in a significant reduction in the water contact angle from 115° to 16.5+/-2.8° after 10 s of treatment. X-ray photoelectron spectroscopy showed that oxygen-containing functional groups (hydroxyl, carbonyl, and carboxyl groups) formed on the plasma-treated PTFE surface, reflecting the hydrophilization of PTFE. At the beginning of the plasma treatment, the water vapor induced the breaking of the CF2 chain, and the additional ethanol vapor generated oxygen-containing polar groups on the PTFE surface. In addition to the modification of the PTFE surface itself, a low-molecular-weight oxidized material layer was deposited over the surface, which prevented further surface modification, and the deposited layer exhibited excellent wettability. The deposited low-molecular-weight oxidized material layer was easily removed by immersion in deionized water, and the exposed modified PTFE surface exhibited stable wettability with water contact angle of 52.7+/-3.5°.
Keywords: DBD plasma, Hydrophilic, Water vapor, Ethanol vapor, Wettability, Polytetrafluoroethylene
Cold Atmospheric Pressure Plasma Jet operated in Ar and He: From Basic Plasma Properties to Vacuum Ultraviolet, Electric Field and Safety Thresholds Measurements in Plasma Medicine 
Andrei Vasile Nastuta, Torsten Gerling
Romania, Germany
Application desired functionality as well as operation expenses of cold atmospheric pressure plasma (CAP) devices scale with properties like gas selection. The present contribution provides a comparative investigation for a CAP system operated in argon or helium at different operation voltages and distance to the surface. Comparison of power dissipation, electrical field strength and optical emission spectroscopy from vacuum ultraviolet over visible up to near infrared ((V)UV-VIS-NIR) spectral range is carried out. This study is extended to safety relevant investigation of patient leakage current, induced surface temperature and species density for ozone (O3) and nitrogen oxides (NOx). It is found that in identical operation conditions (applied voltage, distance to surface and gas flow rate) the dissipated plasma power is about equal (up to 10 W), but the electrical field strength differs, having peak values of 320 kV/m for Ar and up to 300 kV/m for He. However, only for Ar CAP could we measure O3 up to 2 ppm and NOx up to 7 ppm. The surface temperature and leakage values of both systems showed different slopes, with the biggest surprise being a constant leakage current over distance for argon. These findings may open a new direction in the plasma source development for Plasma Medicine.
Keywords: CAP, electric diagnosis, E-field measurements, vacuum-ultraviolet spectroscopy, patient leakage current, power measurement, voltage-charge plot, OES
Mit Kaltplasmaspritzen die Bioaktivität von Kunststoffknochenersatz verbessern
Jun Xu, Max Körner, Angelika Henning, Jürgen Schmidt, Andreas Pfuch, Sebastian Spange
Galvanotechik 8/2022, 1100ff Eugen G. Leuze Verlag
Mechanisms of atmospheric pressure plasma protection of neuronal cells under simulated ischemic stroke conditions
Xu Yan, Bingyan Yang, Jiting Ouyang, Chenyang Zhang, Yu Lai, Zhongfang Shi, Ruoyu Han, Wei Zhang, Fang Yuan, Kostya (Ken) Ostrikov
China, Australia
Physico-chemical and biological effects of atmospheric pressure plasmas (APPs) find numerous applications in biotechnology, medicine, and other fields. Recent studies revealed APPs’ potential for ischemic stroke treatment through the protection of neuronal cells from injuries.
However, the mechanisms of the plasma neuroprotection effects still remain unknown. This study reveals the key mechanisms of APP plasma jet (APPJ) enabled reduction of neuronal cell death caused by oxygen and glucose deprivation (OGD) under stroke-relevant conditions.
Plasma reduced OGD induced apoptosis of SH-SY5Y neuronal cells is based on reactive oxygen and nitrogen species production and on nitric oxide related activation of the cyclic guanosine monophosphate (cGMP) and cGMP-dependent protein kinase G (PKG) pathway, followed
by the Bcl-2/Bax level modulation and caspase3/9 activity inhibition. In addition, the protective effect of APPJ treatment on OGD injured SH-SY5Y cells could be abolished by cGMP pathway inhibitor LY83583 pretreatment. Collectively, our findings highlight that the mechanism
of the neuroprotection effects of the plasma treatment is closely related to the intracellular cGMP/PKG pathway, which provide experimental and theoretical references for future studies on plasma medicine.
Study on the grinding characteristics of fused glass through the dry chemical modification of atmospheric pressure plasma
Long Zhang, Limin Zhu, Xueke Xu, Tianfeng Zhou, Jun Chen, Peng Guo, Peng Liu, Wen Shao 
A grinding method of fused glass is proposed through the dry chemical modification of atmospheric pressure plasma. Before grinding, the surface of fused glass is chemically modified by atmospheric pressure plasma, then the grinding experiment is carried out without any coolant. The objective is to explore the grinding characteristics of the dry chemically modified grinding by atmospheric pressure plasma. First, the experiment on the dry chemical modification of fused glass was carried out with different parameters of atmospheric pressure plasma. Secondly, a #600 diamond wheel was used to perform the grinding experiment with and without modification. Then, the element content, morphologies, and nanoindentation test of the dry chemically modified surface were investigated with reference to the parameters of atmospheric pressure plasma. Finally, the grinding roughness and morphologies were investigated with reference to the modified degree. It is shown that the modified degree of fused glass is influenced by the flow rate of CF4 and the feed speed of plasma. The mechanical property of material changes with the change of the modified degree, which plays a great influence on grinding processing. The grinding roughness can reduce by 32.7% with modification than one without modification. Moreover, the grinding roughness and morphology are related to the modified degree of fused glass. It is confirmed that the grinding processing of fused glass may be improved through the dry chemical modification of atmospheric pressure plasma.
Atmospheric pressure plasma functionalization of polystyrene
Jordyn Polito, Mark Denning, Richard Stewart, David Frost, Mark J. Kushner
Atmospheric pressure plasma jets (APPJs) are used to improve the adhesive and hydrophilic properties of commodity hydrocarbon polymers such as polypropylene, polyethylene, and polystyrene (PS). These improvements largely result from adding oxygen functional groups to the surface. PS functionalization is of interest to produce high value biocompatible well-plates and dishes, which require precise control over surface properties. In this paper, we discuss results from a computational investigation of APPJ functionalization of PS surfaces using He/O2/H2O gas mixtures. A newly developed surface reaction mechanism for functionalization of PS upon exposure to these plasmas is discussed. A global plasma model operated in plug-flow mode was used to predict plasma-produced species fluxes onto the PS surface. A surface site balance model was used to predict oxygen-functionalization of the PS following exposure to the plasma and ambient air. We found that O-occupancy on the surface strongly correlates with the O-atom flux to the PS, with alcohol groups and cross-linked products making the largest contributors to total oxygen fraction. Free radical sites, such as alkoxy and peroxy, are quickly consumed in the post-plasma exposure to air through passivation and cross-linking. O-atom fluences approaching 1017 cm−2 saturate the O-occupancy on the PS surface, creating functionality that is not particularly sensitive to moderate changes in operating conditions.
Comparative structural and techno-functional elucidation of full-fat and defatted flaxseed extracts: implication of atmospheric pressure plasma jet
Chengzhen Nie, Xiaopeng Qin, Ziqiang Duan, Shasha Huang, Xiao Yu, Qianchun Deng, Qisen Xiang, Fang Geng
The relatively inferior techno-functionality of flaxseed protein/polysaccharide complexes, especially regarding emulsifying and antioxidant activities, has partially limited their implication in the health food system. The present study aimed to investigate the effects of an atmospheric pressure plasma jet (APPJ) on the physicochemical, structural and selected techno-functional properties of flaxseed extracts.
The results obtained showed that the full-fat and defatted flaxseed extract solutions (5 mg mL–1) displayed a sustainable decline in pH (−54.06%, −48.80%, P < 0.05) and zeta potential values (−29.42%, −44.28%, P < 0.05), but a gradual increase in particle sizes, as visualised by an optical microscope, during 0–120 s of APPJ treatment. Moreover, the APPJ led to initial decrease but subsequent increase in protein carbonyls and secondary lipid oxidation products, and concurrently changed the spatial conformation and microstructure of flaxseed extracts, as indicated by endogenous fluorescence properties and scanning electron microscopy (SEM). Additionally, the protein subunit remodeling and gum polysaccharides depolymerization were different for full-fat and defatted flaxseed extracts after 30 s of APPJ exposure. Importantly, the emulsifying and antioxidant activities of defatted flaxseed extract were particularly improved, as assessed by cyro-SEM and 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity following 15–30 s of APPJ treatment, as a result of the changing interactions between protein and gum polysaccharides, as well as the release of specific phenolic compounds.
APPJ could serve as a promising strategy for tailoring the specific techno-functionality of flaxseed extracts based on mild structural modification.
A spectral element method for modelling streamer discharges in low-temperature atmospheric-pressure plasmas
I.L. Semenov, K.-D. Weltmann
• The hierarchical Poincaré-Steklov scheme is applied to modelling streamer discharges for the first time.
• An alternative integral representation of the solution of the Poisson equation on rectangular domains is proposed.
• An alternative definition of the numerical diffusion flux for the discontinuous Galerkin method is proposed.
Streamers are ionization fronts that occur in gases at atmospheric and sub-atmospheric pressures. Numerical studies of streamers are important for practical applications but are challenging due to the multiscale nature of this discharge type. This paper introduces a spectral element method for modelling streamer discharges. The method is developed for Cartesian grids but can be extended to be used on unstructured meshes. The streamer model is based on the Poisson equation for the electric potential and the electron continuity equation. The Poisson equation is discretized via a spectral method based on the integral representation of the solution. The hierarchical Poincaré - Steklov (HPS) scheme is used to solve the resulting set of equations. The electron continuity equation is solved by means of the discontinuous Galerkin spectral element method (DGSEM). The DGSEM is extended by an alternative definition of the diffusion flux. A subcell finite volume method is used to stabilize the DGSEM scheme, if required. The entire simulation scheme is validated by solving a number of test problems and reproducing the results of previous studies. Adaptive mesh refinement is used to reduce the number of unknowns. The proposed method is found to be sufficiently fast for being used in practical applications. The flexibility of the method provides an interesting opportunity to broaden the range of problems that can be addressed in numerical studies of low-temperature plasma discharges.
Keywords: Streamer discharge, Low-temperature plasma, Spectral element method, Hierarchical Poincaré-Steklov scheme, Discontinuous Galerkin method
Synthesis of silver nanoparticles by atmospheric pressure plasma jet
Tatiana Habib, José Mauricio A Caiut, Bruno Caillier
France, Brazil
Silver nanoparticles are one of the most extensively used metallic nanomaterials due to their unusual physical and chemical properties as well as their promising applications in a wide range of different fields. In this study, a non-thermal atmospheric pressure helium plasma jet was used to successfully synthesize silver nanoparticles with silver nitrate as a precursor and trisodium citrate as a capping agent. The browning of the solution after only 5 min of plasma irradiation is a result of the surface plasmon resonance (SPR) from the obtained silver nanoparticles. The SPR was confirmed by the presence of an absorption band in the visible range between 400 and 450 nm demonstrated in the UV–vis spectra. The effect of different chemical parameters such as the concentration of silver nitrate and the concentration of citrate on the silver nanoparticles have been studied. These nanoparticles were further characterized using transmission electron microscopy and dynamic light scattering. Therefore, the plasma jet was advantageous to fast produce silver nanoparticles in friendly conditions. In addition, the used experimental setup allows further studies in different solvents conditions and with different capping agents. So, this methodology could be useful for the preparation of silver nanoparticles required for numerous applications such as bioactivity, catalysis, surface enhanced Raman scattering, and photonic.
Wettability modification of polystyrene surface by cold atmospheric pressure plasma jet
M. Bakhshzadmahmoudi, S. Jamali, E. Ahmadi
In this work, we have studied the modification process of polystyrene surface by cold atmospheric pressure plasma jet to achieve a hydrophilic surface. For this purpose, dielectric barrier discharge plasma jet with different powers in short times with radio frequency power supply and argon plasma irradiation in atmospheric pressure were used. It was found that polystyrene surface changed from hydrophobic into hydrophilic after 20-s plasma irradiation and the wettability of surface increased with time. Surface evaluation was done by measuring the water contact angle of the samples before and after the modification. Fourier transform infrared spectroscopy showed the proof for the induction of oxygen-based functional groups in polystyrene when treated with the argon plasma. Plasma parameters were examined using optical emission spectroscopy, voltage-current (VI), and temperature measurements. The relation between plasma parameters and surface modification of the polymer is also discussed.
Keywords: Atmospheric pressure plasma, Dielectric barrier discharge, Hydrophilicity
Surface Modification of Materials by Atmospheric-Pressure Plasma to Improve Impregnation with Essential Oils for the Control of Tropilaelaps Mites in Honeybees (Apis mellifera) 
Thummanoon Boonmee, Laedlugkana Wongthaveethong, Chainarong Sinpoo, Terd Disayathanoowat,
Jeffery S. Pettis, Veeranan Chaimanee
Thailand, USA
In this research, the absorption and release rate of the essential oil, Amomum krervanh, by seven different materials were evaluated. Cardboard showed the highest EO absorption capacity (0.93 ± 0.0052 μL of oil/mg of dry cardboard) followed by balsa wood and drawing board with the EO absorption of 0.77 ± 0.043 and 0.62 ± 0.010 μL of oil/mg of dry material, respectively. The results also demonstrated that cardboard had the highest EO retention (52.84 ± 0.687% after 20 min of analysis). Additionally, the essential oil was released from the drawing board and cardboard at the same rate during the observation period. Surface modification of drawing board and cardboard was performed using atmospheric-pressure plasma for enhancing the material properties for Tropilaelaps control. The absorption capacity of cardboard was decreased after plasma treatment at an argon flow rate of 0.25 and 0.5 Lpm for 60 s/cm2. However, the atmospheric-pressure plasma did not change the EO release property of these materials. Scanning electron microscopy analyses indicated a fractured and scaly surface after plasma treatment of gas flow rate at 0.5 Lpm and 1.0 Lpm for 30 s/cm2. The surface chemical composition of materials was not altered following plasma treatment. Although the number of mite-infested brood cells did not differ significantly between treatment groups at the end of the field experiment, Tropilaelaps spp. populations in the plasma-treated cardboard impregnated with EO 5% (v/v) treatment were lower on days 7–14 of the experiment. Thus, parameters related to the atmospheric-pressure plasma should be further optimized to improve the material surfaces for use with essential oils to control honeybee mites.
Keywords: atmospheric-pressure plasma, surface modification, essential oil, absorption capacity, release rate, Tropilaelaps mite control
The effect of non-thermal atmospheric pressure plasma treatment of wheat seeds on germination parameters and α-amylase enzyme activity
Y. A. Ussenov, Ainur Akildinova, Bissenbaev Amangeldy Kuanbaevich, Kistaubayeva Aida Serikovna, Maratbek Gabdullin, Merlan Dosbolayev, Talgat Daniyarov, Tlekkabul Ramazanov
DOI: 10.1109/TPS.2022.3145831
This contribution presents the results of a study of the germination rate and growth parameters of wheat seeds after atmospheric pressure surface coplanar dielectric barrier discharge (DBD) plasma treatment. The germination rate and biometric parameters such as the root, shoot length, mass of the seedlings, and the α -amylase enzyme activity were studied at different plasma exposure time. The seed coat surface wettability and morphology were determined by apparent contact angle measurement and scanning electron microscope (SEM) analysis. Seed surface disinfection and the presence of filamentous fungi have also been investigated at different discharge parameters. It is shown that the optimal plasma treatment duration for increasing the growth parameters and enhancing the enzymatic activity is 5–15 s. It was found that the longer plasma exposure requires complete sterilization of the seed surface from pathogens, compared to the optimal treatment time for high germination. Based on the obtained results, the possible mechanisms of the positive effect of plasma treatment on the enhanced germination of wheat seeds are discussed.
Keywords: Cold plasma, diffuse coplanar surface barrier discharges (DCSBD), enzyme activity, plasma agriculture, plasma food processing, wheat seed treatment
A resonator-based dual-frequency driven atmospheric pressure plasma jet
Robert Bansemer, Klaus-Dieter Weltmann
An atmospheric-pressure argon plasma jet featuring a novel integrated resonator-based multi-frequency impedance matching is presented and briefly characterized. Two narrow RF frequency bands can be chosen for operation or used simultaneously. This includes a mode with the higher frequency value being exactly five times the lower one. Phase-resolved optical emission spectroscopy measurements show a distinct influence of the input frequency combination on the discharge dynamics. Measurements of the dissipated electrical power and the emission spectrum for each operating mode complete the basic characterization of the device. Although it is constructively much simpler and more compact than dual-frequency discharges using a conventional impedance matching system, the presented device shows an excellent performance in dual-frequency operation.
Keywords: radio frequency, argon jet, dual frequency, impedance matching, discharge dynamics, PROES, lumped circuit
Enhanced Bioremediation of 4-Chlorophenol by Electrically Neutral Reactive Species Generated from Nonthermal Atmospheric-Pressure Plasma
Hiroyuki Kato, Kiyota Sakai, Shou Itoh, Naoyuki Iwata, Masafumi Ito, Masaru Hori, Masashi Kato, Motoyuki Shimizu
Enhanced Bioremediation of 4‑Chlorophenol by Electrically Neutral
Reactive Species Generated from Nonthermal Atmospheric-Pressure
Hiroyuki Kato,# Kiyota Sakai,# Shou Itoh, Naoyuki Iwata, Masafumi Ito, Masaru Hori, Masashi Kato,
and Motoyuki Shimizu*
Cite This: ACS Omega 2022, 7, 16197−16203 Read Online
ACCESS Metrics & More Article Recommendations *sı Supporting Information
ABSTRACT: 4-Chlorophenol (4-CP) is a chlorinated aromatic compound with broad industrial applications. It is released into the environment as an industrial byproduct and is highly resistant to biodegradation. Pseudomonas sp. in the environment and activated
sludge are used for 4-CP bioremediation; however, the degradation of 4-CP takes a long time. Consequently, the toxicity of 4-CP is a major barrier to its bioremediation. In this study, we investigated the synergistic effect of electrically neutral reactive species on the
bacterial bioremediation of 4-CP. Our results showed that the concentration of 4-CP decreased from 2.0 to 0.137 mM and that it was converted to 4-chlorocatechol (4-CC; 0.257 mM), 4-chlororesorcinol (0.157 mM), hydroquinone (0.155 mM), and trihydroxy
chlorobenzene and their respective ring-cleaved products following irradiation of neutral reactive species. These compounds were less toxic than 4-CP, except for 4-CC, which reduced the toxicity of 4-CP to Pseudomonas putida. When the neutral reactive species-
treated 4-CP fraction was added to P. putida cultured in a synthetic sewage medium for 48 h, the 4-CP concentration was reduced to 0.017 mM, whereas nontreated 4-CP (2.0 mM) was hardly degraded by P. putida. These results suggest that the biodegradation of 4-
CP can be efficiently improved by combining irradiation of neutral reactive species with microbial treatment. The irradiation of neutral reactive species of environmental pollutants may additionally lead to further improvements in bioremediation processes.
Optimization of Atmospheric Pressure Plasma Jet with Single-Pin Electrode Configuration and Its Application in Polyaniline Thin Film Growth 
Eun Young Jung, Choon-Sang Park, Hyo Jun Jang, Shahzad Iqbal, Tae Eun Hong, Bhum Jae Shin, Muhan Choi, Heung-Sik Tae
Korea, USA
This study systematically investigated an atmospheric pressure plasma reactor with a
centered single pin electrode inside a dielectric tube for depositing the polyaniline (PANI) thin film based on the experimental case studies relative to variations in pin electrode configurations (cases I, II, and III), bluff-body heights, and argon (Ar) gas flow rates. In these cases, the intensified charge-coupled device and optical emission spectroscopy were analyzed to investigate the factors affecting intensive glow-like plasma generation for deposition with a large area. Compared to case I, the intense glow-like plasma of the cases II and III generated abundant reactive nitrogen species (RNSs) and excited argon radical species for fragmentation and recombination of PANI. In case III, the film thickness and deposition rate of the PANI thin film were about 450 nm and 7.5 nm/min, respectively. This increase may imply that the increase in the excited radical species contributes to
the fragmentation and recombination due to the increase in RNSs and excited argon radicals during the atmospheric pressure (AP) plasma polymerization to obtain the PANI thin film. This intense glow-like plasma generated broadly by the AP plasma reactor can uniformly deposit the PANI thin film, which is confirmed by field emission-scanning electron microscopy and Fourier transform infrared spectroscopy.
Keywords: atmospheric pressure plasmas, glow-like discharge, single pin electrode, plasma deposition, PANI thin film
Antimicrobial finishing of cotton fabric by atmospheric pressure plasma
Yu Cheng, Leilei Jia, Chang Sun, Yunwen Liu, Hui-e Liang
In order to synthesize the antimicrobial cotton fabrics, two antimicrobial agents, 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (TX-DF) and 3-(acrylamidopropyl) trimethylammo-nium chloride (APTAC), were grafted onto cotton fabrics by atmospheric pressure plasma treatment.
Orthogonal array testing strategy (OATS) was applied to investigate the optimum treatment conditions of the atmospheric pressure plasma, including sputter-gas species, gas pressure, treatment power and time. The obtained cotton fabrics were characterized by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray (EDS). And the results revealed the successful grafting of two antimicrobial agents on cotton fabrics. The antimicrobial efficiency of the plasma treated cotton fabric were studied and found that the TX-DF-treated cotton fabric inactivated 99.85% S. aureus and 99.07% E. coli O157:H7 in 30 min contact time.
The cotton sample grafted with APTAC inactivated 74.6% S. aureus and 92.3% E. coli O157:H7 in 30 min. The hand feeling of the plasma treated antimicrobial cotton fabrics ware measured by PhabrOmeter system, and the result showed that the plasma treatment has little effect on hand value.
Thus, the antimicrobial property of cotton fabric finished with TX-DF by the argon/oxygen-plasma techniques achieved sound effects.
Keywords: antimicrobials, cotton, fabric, atmospheric, pressure, plasma, atmospheric, pressure plasma, cotton fabric, antimicrobial agent, graft
Helium atmospheric pressure plasma jet parameters and their influence on bacteria deactivation in a medium
Andrea Jurov, Nikola Škoro, Kosta Spasić, Martina Modic, Nataša Hojnik, Danijela Vujošević, Milena Đurović, Zoran Lj. Petrović, Uroš Cvelbar 
Slovenia, Serbia, Montenegro, UK
Atmospheric pressure plasmas are becoming relevant in local microbial deactivation and other combined effects of plasmas on living organisms. For this reason, our research was focussed on optimisation of atmospheric pressure plasma jet (APPJ) parameters to complete the deactivation of different bacteria strains in a medium. Different helium APPJ treatments with different discharge parameters were used, such as input voltages and gas flows. To better understand plasma properties behind complete bacteria deactivation at optimised discharge parameters, optical and electrical plasma jet diagnostics were performed, including electrical characterisation of the plasma source, optical emission spectroscopy of the plasma plume and intensified charged coupled device imaging of the discharge behaviour for every set of plasma parameters. Then, the resulting plasma liquid chemistry was assessed to establish the connections between reactive species generated in the gaseous and liquid phases. The most efficient deactivation was found for higher discharge powers and gas flow rates, and that was linked to higher densities of reactive oxygen and nitrogen species, especially hydrogen peroxide and medium solvated charges.
Atmospheric pressure plasma jet-mouse skin interaction: Mitigation of damages by liquid interface and gas flow control
 Andrea Jurov, Špela Kos, Tanja Blagus, Ivana Sremački, Gregor Filipič, Nataša Hojnik, Anton Nikiforov, Christophe Leys, Maja Čemažar, Gregor Serša, Uroš Cvelbar
Slovenia, Belgium
The possible benefits of an atmospheric pressure plasma jet skin treatment have been tested in vivo on mouse skin. Many studies have been conducted in vitro on mouse skin cells, but only a few in vivo where, due to the complexity of the biological system, plasma can cause severe damages. For this reason, we investigated how kHz plasma generated in a jet that is known to inflict skin damage interacts with mouse skin and explored how we can reduce the skin damage. First, the focus was on exploring plasma effects on skin damage formation with different plasma gases and jet inclinations. The results pointed to the perpendicular orientation of a He plasma jet as the most promising condition with the least skin damage. Then, the skin damage caused by a He plasma jet was explored, focusing on damage mitigation with different liquid interfaces applied to the treatment site, adding N2 to the gas mixture, or alternating the gas flow dynamics by elongating the jet's glass orifice with a funnel. All these mitigations proved highly efficient, but the utmost benefits for skin damage reduction were connected to skin temperature reduction, the reduction in reactive oxygen species (ROS), and the increase in reactive nitrogen species (RNS).
Atmospheric pressure plasma treatment for enhancing the conducting properties of polypyrrole coated nylon fabric
Smita Deogaonkar-Baride, Shital S. Palaskar
The present study describes a method for plasma-assisted in situ chemical polymerization of polypyrrole on nylon-66 fabric to improve adhesion and conductivity of the polypyrrole coating. Plasma generated from various gas mixtures in dielectric barrier discharge were used to modify the surface of nylon-66 fabric and investigated the influence of plasma on surface chemistry and morphology of nylon-66 fabric. Polypyrrole was then deposited over this plasma pretreated nylon fabric by using oxidative chemical polymerization to get electrically conducting nylon fabric. Surface physical and chemical changes of plasma treated nylon-66 fabric were studied by scanning electron microscopy (SEM), wettability, attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Effect of the plasma treatment on binding strength was analyzed by studying abrasion resistance and surface resistivity. Results showed that the strongest interfacial bonding and high conductivity were achieved for He+O2 plasma pretreated PPy coated nylon-66 fabric. Surface functional groups such as CO, COH, COOH, and CONH were detected on plasma treated nylon-66 fabric by XPS. These surface functional groups are responsible for the improved adhesion and conductivity of PPY coating on nylon fabric by 35% (up to 2500 abrasion cycles) and 50%, respectively.
Decontamination of aniline and malathion on material surface by array cold atmospheric pressure plasma jet: Mechanism and decontamination pathways
Zhihao Yi, Likun Chen, Yashuang Ren, Yang Li, Zhen Liu, Jina Wu, Anna Zhu
• The highly integrated hand-held ACAPPJ system with 4 × 4 array channels was developed.
• A total of 16 plasma jets with biggest length of 4 cm could be generated.
• The decontamination efficiency of ACAPPJ was significantly improved when H2O and O2 was introduced.
• The decontamination mechanism and pathways of aniline and malathion was proposed.
• The ACAPPJ could be directly applied on animal skins without causing any harms.
An array cold atmospheric pressure plasma jet (ACAPPJ) apparatus with 4 × 4 channels and coverage area over than 6 cm2 was developed to decontaminate toxic chemicals on material surfaces using Helium (He) gas as discharge gas. Experimental results indicated that 20.4 mg aniline on 6.25 cm2 stainless steel plate could be totally decontaminated within 3 min when the ACAPPJ was conducted under 20 kV, 15 kHz, 10 L/min gas flow and 1.5 cm distance. The decontamination efficiency of malathion was not as good as aniline, but addition of H2O and O2 could apparently improve the decontamination performances. The decontamination rate of malathion could be improved from 45% to 95% when 1% H2O and 1% O2 were simultaneously introduced with He into the ACAPPJ system. ACAPPJ could even decontaminate the malathion penetrated into wood or rubber materials. The decontamination of aniline and malathion were the first order kinetic reactions, in which the·OH and O3 formed in the ACAPPJ played major roles. The decontamination of aniline was mainly electrophilic and ring opening reactions, while the malathion was mainly decontaminated due to the breaking of Pdouble bondS and S-C bonds. The intermediate products of aniline and malathion could be mineralized into CO2 and H2O when they were decontaminated by ACAPPJ for enough time. According to the nude mouse skin experiments, the ACAPPJ could be directly applied on animal skins without any electrical and chemical harms
Keywords: Array cold atmospheric pressure plasma jet, Aniline, Malathion, Decontamination, Hydroxyl radicals, Ozone
Effect of material properties on electron density and electron energy in helium atmospheric pressure plasma jet
Wenchong Ouyang, Chengbiao Ding, Qi Liu, Weifeng Deng, Zhengwei Wu
• A two-dimensional self-consistent fluid model was developed.
• Propagation mechanism of helium APPJ is analyzed.
• Effects of material properties on the electron density and energy are discussed.
• The differential mechanism of the effect of material properties is discussed.
In recent years, Atmospheric pressure plasma jet (APPJ) have been widely used in biomedicine and material modification. APPJ exhibits different discharge characteristics when processing various materials or biological tissues, which has a certain influence on the processing effect. However, the influence of the processed material properties on the plasma characteristics has been ignored. This work developed a fluid model to study the influence of material properties (material thickness and relative permittivity) on the plasma characteristics of needle-plane APPJ, and the related influence mechanism was discussed. High electric field and electron energy appear in the head of streamer, which shows the plasma bullet has a substantial contribution to high-energy electrons in plasma jet. Both material thickness and relative permittivity increase the electric field strength, which leads to a corresponding increase in the electron energy and electron density of APPJ. Through further quantitative analysis, an interesting phenomenon was found that compared with the effect of material thickness, material relative permittivity has a more significant influence on the electron energy, while material thickness has a greater influence on the electron density. The reason is that material thickness has a greater effect on the ionization rate than the relative permittivity, resulting in greater degree of increase in electron density, while the increase in electron density has a certain contribution to the reduction of electron energy. The results depicts that processing effect will be further improved by taking into account the influence of material properties on the plasma characteristics of APPJ.
Keywords: Plasma jet, Material properties, Electron density, Electron energy
Comparison between atmospheric-pressure-plasma-jet-processed and furnace-calcined rGO-MnOx nanocomposite electrodes for gel-electrolyte supercapacitors
Jheng-Yun Lai, Cheng-Che Hsu, Jian-Zhang Chen
• APPJ for rGO-MnOx supercapacitors (SCs) processing.
• Results are compared with those processed by electric furnace.
• Better performance of the APPJ-processed SCs.
• Synergetic effect of heat and reactive nitrogen plasma species.
• 620 °C × 8 min APPJ processing exhibits the best areal capacitance of 57.01 mF/cm2.
Reduced graphene oxide (rGO)-Mn(NO3)2·4H2O pastes were screen-printed on a carbon cloth substrate and then calcined using a nitrogen atmospheric-pressure-plasma-jet (APPJ) and/or tube furnace to convert it into rGO-MnOx. The rGO-MnOx electrodes were then used in a PVA/H2SO4 gel-electrolyte supercapacitor (SC). The SCs were characterized by cycle voltammetry (CV) and galvanostatic charging/discharging (GCD). The results reveal better performance of the APPJ-processed SCs in comparison with furnace-processed ones under the same processing temperature, possibly owing to the synergetic effect of heat and reactive nitrogen plasma species. The rGO-MnOx SC is also superior to the rGO-SnOx SC reported in our previous study processed under similar APPJ processing. The rGO-MnOx SC processed by APPJ at 620 °C for 8 min exhibits the best areal capacitance of 57.01 mF/cm2 as evaluated by GCD with a capacitance retention rate of 84.41% after a 10,000-cycle CV test.
Keywords: Atmospheric-pressure plasma, Manganese oxide, Reduced graphene oxide,
Supercapacitor, Rapid calcination
Numerical study of singlet delta oxygen (O2 (a1Δg)) generation and transport in the He/O2 atmospheric pressure plasma jet
Yuanyuan Jiang, Yanhui Wang, Jiao Zhang, Dezhen Wang
J. Phys. D: Appl. Phys. 55 335203
This paper investigates the spatial-temporal evolution and the transport of the singlet delta oxygen (O2(a1Δg)) of an atmospheric pressure plasma jet using a 2D fluid modeling. The plasma jet is produced in pure helium or helium with small oxygen admixtures (no bigger than 2%), by applying a constant DC voltage of +5 kV on the annular electrode. It is found that, at the 0.7% O2 admixture, a higher O2(a1Δg) density is obtained inside the tube before the jet impacts the substrate. After the jet propagates along the substrate surface, the peak O2(a1Δg) density is transferred from the tube to the gap. Varying the O2 admixtures percentage in the working gas changes the O2(a1Δg) spatial distribution. The O2(a1Δg) with two thinner edges is dominantly produced in the helium–air mixing layer for pure helium. The addition of O2 in the working gas leads to O2(a1Δg) production in the tube. Meanwhile, the thickness of the O2(a1Δg) edges increases in the helium–air mixing layer. But the radius of the O2(a1Δg) density channel continuously reduces with the O2 admixture. The O2(a1Δg) density and its surface flux first increase within the 0.7% O2 admixture and then decreases with the further augment of the O2 admixture. The influence of the gas flow velocity on the production and transport of O2(a1Δg) is also studied. Increasing the gas flow velocity changes the spatial distribution of the O2(a1Δg) density from the solid structure to the annular structure in the gap. At the same time, lower volume average density and instantaneous flux are obtained at larger gas flow velocity.
Application of Sliding Discharge with Tri-Electrode Dielectric Barrier Discharge for Formation of Planar Atmospheric Pressure Plasma
Hiroshi Akamatsu
75th Annual Gaseous Electronics Conference, October 3–7, 2022
Session HT4: Poster Session I (4:00-6:00pm, JST)
Atmospheric pressure low temperature plasma has been formed by a tri-electrode dielectric barrier discharge configuration. This electrode configuration is used for sliding discharge in plasma actuators. The plasma is applied on formation of functional thin film with metal organic plasma decomposition. The first electrode, which is covered with an insulator layer, was grounded. The second electrode, which is attached on the insulator layer, was powered by low frequency AC high voltage power supply. The third electrode, which is also attached on the insulator layer, was powered by the other low frequency Ac high voltage power supply. In this experiment, two-dimensional plasma with 20 mm x 20 mm in area has been formed by feeding helium gas.
Sending and receiving acoustic waves using atmospheric pressure plasmas
Daniel Hufschläger, Mate Gaal
DAGA 2022: Jahrestagung für Akustik, Stuttgart
Effect of Atmospheric Pressure Plasma in Inert Gases on Orthopedic Ultra-High Molecular Weight Polyethylene
Victor N. Vasilets, Yuriy Velyaev, Andrew Mosunov, Maxim Evstigneev
In this work, studies have been conducted on the treatment of ultrahigh molecular weight polyethylene (UHMWPE), which is one of the structural materials used in the endoprostheses, with atmospheric pressure plasma in high-purity argon and helium. For this purpose, an installation consisting of a high-voltage pulsed generator, voltage and current measuring devices and a reaction quartz chamber with electrodes, in which UHMWPE samples were placed, was developed and constructed. It is shown that processing under certain conditions in Ar plasma and He at atmospheric pressure leads to the appearance of terminal double bonds in the structure of the processed polyethylene, as evidenced by the appearance of a peak of 880 cm-1, in the attenuated total reflection IR spectrum. This peak is observed both for samples treated in helium and argon plasma. The formation of such bonds is a consequence of the generation of active radicals in the UHMWPE surface layer under plasma treatment, which, during recombination, also form intermolecular crosslinking, thereby increasing the strength characteristics of the material as a whole. The modification of the surface of the treated samples begins within the first minute of processing and reaches its peak values 10-20 minutes after treatment in plasma.
Keywords: ultra-high molecular weight polyethylene, endoprostheses, plasmachemical treatment, atmospheric plasma, intermolecular crosslinking
Reactive oxygen and nitrogen species detection produced by an atmospheric pressure plasma jet
Louis Free
PhD Thesis
This thesis presents a novel, asymmetrical atmospheric pressure plasma jet, that uses air as its working gas, operating in the kilohertz range. The plasma system is designed to be mobile, easily set-up in many environments and has variable controllability, such as voltage, airflow and electrode position. The initial body of work presented in the thesis relates to the design and development of the atmospheric pressure plasma jet used throughout the bulk of the thesis. The key components of the atmospheric plasma jet are introduced. Electrical measurements of the plasma were also preformed and showed that the plasma operated electrically in two modes, the so called noisy and quiet modes. Optical emission spectroscopy was preformed on the plasma jet and showed that the emission spectrum of the jet was complex, containing emissions from many species, both molecular and atomic. These species included but were not limited to atomic species of nitrogen, oxygen and hydrogen and molecular emissions from N2, O2 and OH. In addition to this, it is possible to control the emission intensities from these species by varying the control parameters of the plasma jet such as voltage, airflow and electrode distance. The observed emission spectra were noticed to be lacking in any optical features due to emissions from nitric oxide, while it was believed to be the case that the plasma jet should produce nitric oxide. To test this hypothesis the experimental method laser induced fluorescence was chosen as a means to probe or nitric oxide in the plume region of the plasma. Experimentally it was found that nitric oxide was present within the plume. In addition by again varying the control parameters of the plasma jet the absolute number density of nitric oxide within the plume of the plasma could be varied. Finally, two-photon absorption laser induced fluorescence is used to probe for atomic oxygen in the plume region of the atmospheric pressure plasma jet. Two photon absorption differs from the single photon method in that two photons are simultaneously absorbed by and used to excite the species under investigation, opening up the possibility to probe species with excitation energies that are difficult to reach using conventional lasers systems. Like, the case for nitric oxide, atomic oxygen was confirmed to be present within the plume, although it was not possible to determine an absolute number density. Likewise, by varying the control parameters a change in the trend in the intensity of the fluorescence was observed.
Flame coatings by CCVD (Pyrosil) for R2R applications
Arnd Schimanski, Björn S.M. Kretzschmar
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 like roll to roll applications (R2R). 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 shown and the technical realization is given 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 like adhesion
promotion, optical effective and barrier layers are reviewed.
Dissolution Characteristics of Copper Oxide in Gas-liquid Hybrid Atmospheric Pressure Plasma Reactor Using Organic Acid Solution
Heoung Su Kwon, Won Gyu Lee
In this study, a gas-liquid hybrid atmospheric pressure plasma reactor of the dielectric barrier discharge method was fabricated and characterized. The solubility of copper oxide in the organic acid solution was increased when argon having a larger atomic weight than helium was used during plasma discharge. There was no significant effect of mixing organic acid solutions under plasma discharge treatment on the variation of copper oxide’s solubility. As the applied voltage for plasma discharge and the concentration of the organic acid solution increased, the dissolution and removal power of the copper oxide layer increased. Solubility of copper oxide was more affected by the concentration in organic acid solution rather than the variation of plasma applied voltage. The usefulness of hybrid plasma reactor for the surface cleaning process was confirmed.
Keywords: Gas-liquid hybrid, Plasma reactor, Cleaning process, Copper oxide, Organic acid solution, Solubility
Applications of Cold Atmospheric Pressure Plasma in Dentistry-A Review
Mitthra Suresh, V. T. Hemalatha, N. Mani Sundar, Arthi Nisha
Suresh et al.; JPRI, 34(11A): 45-55, 2022; Article no.JPRI.83210
DOI: 10.9734/JPRI/2022/v34i11A35533
Plasma is one of the most dominant states of matter in the universe and was identified
by Sir William Crooke in 1879. It is an electrically conducting medium that responds to electric and magnetic fields. It implies studies concerning the direct action of low temperature and the effect of low atmospheric plasma pressure on body tissues for various non-invasive therapeutic treatments or diagnostic purposes. Plasma consists of large quantities of highly reactive species, such as ions, energetic electrons, exited atoms and molecules, ultraviolet photons in the metastable state, and active radicals. Research has revealed promising and successful medical applications of these non-thermal, cold plasma-reactive oxygen species. The objective of this minor review is to highlight the numerous applications of cold atmospheric pressure plasma (CAPP) in dentistry, which include: dental caries prevention by bacterial inactivation; prevention of oral cancer by selective destruction of the tumour cells and damaged tissue repair effects; tooth bleaching or whitening procedures; in restorative dentistry for placement of composite restorations; in endodontic therapy for root canal disinfection; and for the treatment of oral thrush (induced by Candida albicans).
Keywords: Cold atmospheric pressure plasma, antimicrobial agent, plasma medicine,
Fouling resistant and performance tunable ultrafiltration membranes via surface graft polymerization induced by atmospheric pressure air plasma
Yian Chen, Jie Zhang, Yoram Cohen
USA, China
• Atmospheric pressure air plasma (Air APP) treatment of polysulfone UF membrane.
• Acrylic acid graft polymerization induced by PSf UF membrane treatment with Air APP.
• Polysulfone (PSf) UF membrane surface tethered with polyacrylic acid (PAA) chains.
• PSf-PAA membrane of improved antifouling characteristics and cleaning efficacy.
• Surface tethering of PAA enabled tuning of UF PSf membrane permeability and MWCO.
Surface modification of polysulfone (PSf) surface, via acrylic acid (AA) surface graft polymerization, induced by atmospheric pressure Air plasma (Air APP) surface treatment, was explored for imparting UF membrane fouling resistance and tuning its performance. PSf surface activation with Air APP and subsequent tethering of PAA chains resulted in a higher degree of surface hydrophilicity relative to the use of He and He/O2 plasmas. Surface-nano-structed (SNS) PSf membranes with tethered PAA chains were of increased surface hydrophilicity and the polar component of the surface energy by 14% and 556%, respectively, and had a greater negative zeta potential (by 26% at pH >~6) relative to the native-PSf membrane. Fouling filtration tests with bovine serum albumin (BSA) and sodium alginate demonstrated reduced fouling resistance, relative to the native-PSf membrane. Moreover, complete permeability recovery of the fouled SNS-PAA-PSf membrane was achieved, via simple water backwash, relative to 66%-81% permeability recovery for the native PSf membrane. Tethering the PSf UF surface with PAA chains was also enabled tuning of the membrane molecular weight cutoff (MWCO) and hydraulic
permeability. It was shown that starting with the same PSf UF membrane a series of SNS-PAA-PSf membranes can be synthesized whereby performance tuning was achieved over a MWCO range of 5.5–11 kDa and a corre-sponding permeability range of 12.7–23.5 L⋅m
Keywords: Ultrafiltration, Membrane modification, Fouling reduction, Membrane cleaning
Atmospheric pressure plasma, Graft polymerization, Surface tethered polymer chains, Membrane performance tuning
Effect of atmospheric pressure cold plasma (ACP) treatment on the technological characteristics of quinoa flour
Leila Zare, Neda Mollakhalili-Meybodi, Hossein Fallahzadeh, Masoumeh Arab
• Atmospheric pressure cold plasma (ACP) treatment have been applied on quinoa.
• ACP's active species influence the technological functionality of quinoa flour.
• ACP treatment results in protein polymerization and starch depolymerization.
• ACP treatment time and voltage affect the quinoa flour's technological properties.
Atmospheric pressure cold plasma (ACP) is considered as non-thermal treatment with potential microbial inactivation efficiencies. This study is aimed to determine the effect of ACP treatment on technological characteristics of quinoa flour using Fourier Transform Infrared Spectroscopy, flour hydration characteristics, thermal properties, rheological measurement and morphological characterization. Whole quinoa grains were
subjected to a dielectric barrier discharge plasma reactor for 5 min at 50 kV, 10 min at 50 kV, 5 min at 60 kV and 10 min at 60 kV known as S1, S2, S3 and S4 respectively. Untreated sample is named as control sample. Results indicated the significant impact of ACP treatment on rheological, thermal, hydration and morphological characteristics of quinoa flour depending on the exposed time and voltage. For example, while a voltage dependent
decrease (p < 0.05) has been found in enthalpy with values equal to 743.6 ± 0.5, 1395 ± 1, 635.6 ± 0.6 and 804.3 ± 0.9 J/g for S1, S2, S3 and S4 respectively, it is positively influenced by increasing the exposure time at constant voltage. Consequently, it seems that the influence of ACP treatment on technological characteristics which is mainly induced by time- and/or voltage-dependent changes in proteins and starch structures needs to be
optimized regarding the desired behavior characteristics.
Keywords: Atmospheric pressure cold plasma, Quinoa, Technological properties, Non-thermal processing
Application of atmospheric pressure cold plasma activated plant protein preparations solutions as an alternative curing method for pork sausages
Monika Marcinkowska-Lesiak, Iwona Wojtasik-Kalinowska, Anna Onopiuk, Adrian Stelmasiak, Agnieszka Wierzbicka, Andrzej Poltorak
This study was performed to determine the effect of plasma-activated solutions of protein preparations of selected plants, as an alternative nitrite source, on the quality characteristics of pork sausages. The used solutions contained 500 ppm nitrite. Sausages without nitrite (NC), with 75 ppm sodium nitrite (PC), and with solutions of soy (E1), pea (E2) and lentil (E3) preparations (100 g/kg of meat ingredients) were manufactured and stored for 8 days. The results showed that after processing sausages from E1, E2 and E3 groups showed similar nitrite content as PC group (20.69–21.89 mg nitrite/kg; P ≥ 0.05). Performed analyses (residual nitrite, nitrosylhemochrome content, a* values, thiobarbituric acid reactive substances, total aerobic plate count) suggested also that addition of nitrite through solutions of soy and pea plasma-activated preparations extended the shelf life of sausages comparable to sodium nitrite without a negative effect on aroma (PCA), as was reported for some other sources of nitrite.
Keywords: Alternative meat curing method, Non-thermal atmospheric pressure plasma, Nitrite, Plasma activated solution, Plant protein preparations, Sausages
Enhanced Adsorption Removal of As (Iii) Using Mnofe2o3 Via Catalytic Redox Transformation with the Non-Thermal Atmospheric Pressure Plasma Jet
Shaik Abdul Munnaf, Jun Sup Lim, Janardhan Reddy Koduru, Eun Ha Choi
In this study, redox adsorption of the heavy metal, As(III), was performed using non–thermal plasma discharge in an aqueous medium. The generated reactive species like O, OH, and H2O2 by the interaction of water molecules with the plasma discharge at ambient conditions were used to transform As(III) to As(V) and surface modification of adsorbent, MnOFe2O3. In this study, the maximum amount of reactive species, H2O2 was found to be 31.71 μM in the plasma-treated water.
These reactive species (H2O2) were utilized for the oxidation of As(III) to As(V), which was
successfully confirmed by XPS analysis. Also found the catalyzing adsorption ability of adsorbent was enhanced by 30 % owing to the redox transformation of its surface in the presence of plasma discharge when compared to the absence of plasma. Further, the batch kinetics and isotherms studies revealed that the adsorption process was which is rate-limiting, on the𝑅2 ≈ 1.00, homogeneous surface of the adsorbent. The resultant maximum adsorption capacity was estimated to be 12.82 mg As/g based on the Langmuir model at pH 6.50, 0.15 g/l of MnOFe2O3, and 1 mg/l of As(III), under an applied voltage of 3.5 kV. The resultant adsorption yield enhancements were 29.3 g/kWh, 15.2 g/kWh, and 13.1 g/kWh at 0.5, 1.0, and 1.5 mg/l of As(III), respectively. Overall, the results indicate that eco-friendly non-thermal plasma discharge potentially could remove the
As(III) from contaminated water as per the WHO level, which could assist the redox Keywords: adsorption, process, Non-thermal plasma, heavy-metal (As (III)), reactive species, MnOFe2O3, redox adsorption process
Experimental study on the treatment of oil-based drill cutting by pulsed dielectric barrier discharge plasma at atmospheric pressure
Yongqian Wu, Lijian Ding, Cheng Zhang, Tao Shao, Weijiang Chen
Oil-based drilling cuttings produced in the process of oil exploration and shale gas development are harmful to the ecological environment. The emerging low-temperature plasma technology has shown potential for environmental protection. In this paper, pulsed dielectric barrier discharge (DBD) plasma was used to treat contaminated drilling cuttings at atmospheric pressure. The effect of adding active aluminium oxide (Al2O3) balls to the oil-based cuttings on the degradation rate of mineral oil was evaluated. Results showed that when the oil-based drilling cuttings were mixed with active Al2O3 balls, the highest degradation rate of mineral oil (68.1%) was achieved when the treatment time was 30 min. This rate was 41.8% higher than that obtained by DBD treatment alone. The Fourier transform infrared spectroscopy showed that the content of alkanes in the treated samples decreased significantly. The gas chromatography-mass spectrometry and ion chromatography analysis showed that formic acid, acetic acid, and other by-products were formed. The contents of C and H in the samples treated by DBD decreased. Overall, this study provides much-needed insights into the reaction mechanism and pollutant degradation process of the synergistic treatment system of pulsed DBD and active Al2O3 balls in the field of oil-based drilling cuttings treatment.
Spectrally filtered ps–ns emission dynamics of atmospheric-pressure nanosecond pulsed plasmas
Karna Patel, Anup Saha, Tanbo Zhou, Terrence R. Meyer, Sally Bane, Aman Satija
The temporal dynamics of atmospheric-pressure nanosecond pulsed plasma discharges in a pin-to-pin electrode configuration are studied using streak-camera line imaging of the interelectrode gap with a time resolution as short as ∼25 ps. Discharge emission initiates homogeneously throughout the interelectrode gap with no detectable streamer propagation and then temporally decays in two distinct phases. Plasma emission bands attributed to various electronic transitions are tracked for single discharges in air and N2. Spectral filtering of the excited molecular states reveals that the N2(C–B) and N2(B–A) emission bands evolve in distinct early and late phases, respectively, with a time separation of ∼15–20 ns. Furthermore, significant differences in the temporal dynamics of plasma discharges in air and N2 are observed. High levels of excited-state atomic oxygen and NO appear after the initial decay of the N2(C) state and coincide primarily with the latter phases of plasma evolution in air environments. From temporal traces of discharge emission, the formation and relaxation timescales of the electronically excited states of N2 are quantified in pure N2 and air environments with sub-nanosecond resolution. The streak-OES (optical emission spectroscopy) technique enables quantitative time-resolved studies of key chemical species for model validation in ultra-short-pulsed plasmas.
Keywords: Electric discharges, Plasma discharges, Emission spectroscopy, Streak cameras,
Plasma spectroscopy

Literatursammlung Atmosphärische Plasmen - Jahr 2021

Effect of plasma remelting on microstructure and properties of a CoCrCuNiAl0.5 high-entropy alloy prepared by spark plasma sintering
Mingliang Wang, Guojia Zhang, Hongzhi Cui, Yiping Lu, Yong Zhao, Na Wei & Tingju Li
2021 Journal of Materials Science volume 56, pages 5878–5898(2021)
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.
Cu2O/CuO heterojunction catalysts through atmospheric pressure plasma induced defect passivation
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
UK, India, Singapoore Applied Surface Science Volume 541, 1 March 2021, 148571
• 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.
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.
Corrosion properties of β-Ta alloyed Ti6Al4V by double-glow plasma surface alloying technique
Ying Liu, Bing Zhou, Hongkong Wang, Jie Gao, Yong Ma, Hongjun Hei, Yanxia Wu, Shengwang Yu
China  J Mater Sci 56, 6487–6498 (2021)
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.
Effect of plasma oxidation on tin-oxide active layer for thin-film transistor applications
Zong-Wei Shang, Qian Xu, Guan-You He, Zhi-Wei Zheng, Chun-Hu Cheng
China, Taiwan J Mater Sci 56, 6286–6291 (2021)
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.
Direct coating of copper nanoparticles on flexible substrates from copper precursors using underwater plasma and their EMI performance
Kangil Kim, Jin Young Huh, Yong Cheol Hong
Republic of Korea
• 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.
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.
Environmental reliability and moisture barrier properties of silicon nitride and silicon oxide films using roll-to-roll plasma enhanced chemical vapor deposition
Won Jae Lee, Tae-Yeon Cho, Sung-Hoon Cho, Seong-Keun Cho
• 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.
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.
Ceramic coating on Ti-6Al-4V by plasma electrolytic oxidation in molten salt: Development and characterization
Alexander Sobolev, Michael Zinigrad, Konstantin Borodianskiy
• 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.
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.
Comparing the properties of commercially treated and air plasma treated carbon fibers
Racim Radjef, Karyn L. Jarvis, Bronwyn L .Fox, Sally L. McArthur
• 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.
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.
Fast and facile synthesis of carbonate-modified NiFe layered double hydroxide nanosheets by dielectric barrier discharge microplasma: mechanism and application in enhanced water oxidation
Zhipeng Wang, Jiahui Zhang, Qiang Wang, Xue Jiang, Ke Huang, Xiaoli Xiong
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.
Characterization of surface physico-chemistry and morphology of plasma-sized carbon fiber
D. Gravis, S. Moisan, F. Poncin-Epaillard
• 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
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.
Tribological performance assessment of Al2O3-YSZ composite coatings deposited by hybrid powder-suspension plasma spraying
Ashish Ganvir, Sneha Goel, Sivakumar Govindarajan, Adwait Rajeev Jahagirdar, Stefan Björklund, Uta Klement, Shrikant Joshia
Sweden, India
• 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.
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.
Inhibitory effects of hematite nanoparticles on corrosion protection function of TiO2 coating prepared by plasma electrolytic oxidation
Amin Hoseini, Benyamin Yarmand, Alireza Kolahi
• 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.
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.
Influence of ZnO on thermal control property and corrosion resistance of plasma electrolytic oxidation coatings on Mg alloy
Xinyan Wang, Xiaopeng Lu, Pengfei Ju, Yan Chen, Tao Zhang, Fuhui Wang
• 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.
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.
Dual-strengthening of steel surface and bulk via synergistic effect of plasma nitriding: A case study of M50 steel
Jiawei Yao, Fuyao Yan, Baofeng Chen, Ying Yang, Yueming Xu, Mufu Yan, Yanxiang Zhang
• 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.
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.
Effects of Co addition on microstructure and cavitation erosion resistance of plasma sprayed TiNi based coating
Xinlong Wie, Wuyan Zhu, Aolin Ban, Dejia Zhu, Chao Zhang, Hongbiao Dong
China, UK
• 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.
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.
Thermal shock behavior of Ba(Mg1/3Ta2/3)O3-YSZ double-ceramic-layer thermal barrier coatings prepared by atmospheric plasma spraying
Yupeng Cao, Xianjin Ning, Quansheng Wang
• 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.
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.