Plasma Sources
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Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 104
Author(s):  
Panagiotis Dimitrakellis ◽  
François Faubert ◽  
Maxime Wartel ◽  
Evangelos Gogolides ◽  
Stéphane Pellerin

We studied the epoxy polymer surface modification using air plasma treatment in a Gliding Arc (GA) plasma reactor and a pulsed Dielectric Barrier Discharge (DBD). We employed optical emission spectroscopy (OES) measurements to approximate the vibrational and rotational temperatures for both plasma sources, as well as surface temperature measurements with fiber optics and IR thermography to corelate with the corresponding hydrophilization of the epoxy material. Water contact angle measurements revealed a rapid hydrophilization for both plasma sources, with a slightly more pronounced effect for the air DBD treatment. Ageing studies revealed stable hydrophilicity, with water contact angle saturating at values lower than 50°, corresponding to a >50% decrease compared to the untreated epoxy polymer. ATR-FTIR spectroscopy studies showed an additional absorption band assigned to carbonyl group, with its peak intensity being higher for the DBD treated surfaces. The spectra were also correlated with the surface functionalization via the relative peak area ratio of carbonyl to oxirane and benzene related bands. According to SEM imaging, GA plasma treatment led to no apparent morphological change, contrary to DBD treatment, which resulted in nano-roughness formation. The enhanced surface oxidation as well as the nano-roughness formation on epoxy surface with the air DBD treatment were found to be responsible for the stable hydrophilization.


Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 238
Author(s):  
Josef Khun ◽  
Anna Machková ◽  
Petra Kašparová ◽  
Myron Klenivskyi ◽  
Eva Vaňková ◽  
...  

A non-thermal plasma (NTP) is a promising tool against the development of bacterial, viral, and fungal diseases. The recently revealed development of microbial resistance to traditional drugs has increased interest in the use of NTPs. We have studied and compared the physical and microbicidal properties of two types of NTP sources based on a cometary discharge in the point-to-point electrode configuration and a corona discharge in the point-to-ring electrode configuration. The electrical and emission properties of both discharges are reported. The microbicidal effect of NTP sources was tested on three strains of the bacterium Staphylococcus aureus (including the methicillin-resistant strain), the bacterium Pseudomonas aeruginosa, the yeast Candida albicans, and the micromycete Trichophyton interdigitale. In general, the cometary discharge is a less stable source of NTP and mostly forms smaller but more rapidly emerging inhibition zones on agar plates. Due to the point-to-ring electrode configuration, the second type of discharge has higher stability and provides larger affected but often not completely inhibited zones. However, after 60 min of exposure, the NTP sources based on the cometary and point-to-ring discharges showed a similar microbicidal effect for bacteria and an individual effect for microscopic fungi.


2021 ◽  
pp. 260-270
Author(s):  
Sergey M. Polozov ◽  
Vladimir I. Rashchikov

Conventionally, electron guns with thermionic cathodes or field-emission cathodes are used for research or technological linear accelerators. RF-photoguns are used to provide the short electron bunches which could be used for FEL’s of compact research facilities to generate monochromatic photons. Low energy of emitted electrons is the key problem for photoguns due to high influence of Coulomb field and difficulties with the first accelerating cell simulation and construction. Contrary, plasma sources, based on the laser-plasma wakefield acceleration, have very high acceleration gradient but rather broad energy spectrum compared with conventional thermoguns or field-emission guns. The beam dynamics in the linear accelerator combines the laser-plasma electron source and conventional RF linear accelerator is discussed in this paper. Method to capture and re-accelerate the short picosecond bunch with extremely broad energy spread (up to 50 %) is presented. Numerical simulation shows that such bunches can be accelerated in RF linear accelerator to the energy of 50 MeV with output energy spread not higher than 1 % .


Author(s):  
Feng Liu ◽  
Yue Zhuang ◽  
Yulei Zhao ◽  
Jie Chen ◽  
Zhi Fang

Abstract Dielectric barrier discharges (DBDs) have been widely used in ozone synthesis, materials surface treatment, and plasma medicine for their advantages of uniform discharge in atmospheric pressure and high plasma-chemical reactivity. To further improve the plasma treatment efficiency and activity, a small amount of admixture can be introduced into working gases (usually Ar, He, N2), while it can affect plasma uniformity significantly. In this paper, oxygen is added into Ar nanosecond (ns) pulsed and AC DBDs DBD and the effect of the added oxygen on the uniformity and reactivity have been investigated with optical and electrical methods. The plasma uniformity is quantitatively analyzed by Gray Value Standard Deviation (GVSD) of discharge images. The optical emission spectroscopy (OES) measurement of the emission lines with different energy thresholds can reveal the tendency of T e under different operation conditions. The n e are estimated from the electrical analysis. It is found that the ns pulsed DBD shows a much better uniformity than AC DBD. With the addition of O2, the uniformity of ns-pulsed Ar DBD gets worse for the O2- negative ions by the attachment of electron on O2 distorts the space electric field and promotes the filamentary formation. While, in AC Ar DBD, the added O2 can reduce the n e and brightness of filaments, which enhances the plasma uniformity. Overdose O2 molecules cause drops of n e and T e to plasma extinction. The results can help to realize the establishment of the reactive and uniform atmospheric low temperature plasma sources.


Coatings ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1506
Author(s):  
Kenneth Scott Alexander Butcher ◽  
Vasil Georgiev ◽  
Dimka Georgieva

Recent designs have allowed hollow cathode gas plasma sources to be adopted for use in plasma-enhanced atomic layer deposition with the benefit of lower oxygen contamination for non-oxide films (a brief review of this is provided). From a design perspective, the cathode metal is of particular interest since—for a given set of conditions—the metal work function should determine the density of electron emission that drives the hollow cathode effect. However, we found that relatively rapid surface modification of the metal cathodes in the first hour or more of operation has a stronger influence. Langmuir probe measurements and hollow cathode electrical characteristics were used to study nitrogen and oxygen plasma surface modification of aluminum and stainless-steel hollow cathodes. It was found that the nitridation and oxidation of these metal cathodes resulted in higher plasma densities, in some cases by more than an order of magnitude, and a wider range of pressure operation. Moreover, it was initially thought that the use of aluminum cathodes would not be practical for gas plasma applications, as aluminum is extremely soft and susceptible to sputtering; however, it was found that oxide and nitride modification of the surface could protect the cathodes from such problems, possibly making them viable.


2021 ◽  
pp. 23-30
Author(s):  
Andrii Breus ◽  
Sergey Abashin ◽  
Ivan Lukashov ◽  
Oleksii Serdiuk ◽  
Oleg Baranov

Plasma-enhanced growth of copper oxide nanostructures is widely explored in science and manufacturing, since it provides the flexibility, productivity, and cost-effectiveness necessary to meet the growing demands of customers. However, in the field of growth of metal oxide nanostructures, thermal methods still prevail in plasma methods in spite of long production time up to ten hours. Radiofrequency and microwave plasma sources were applied to grow CuO nanostructures, which are of high interest in various branches of industry, and allowed obtaining a large variety of the nanostructures, and nanowires in particular. At that, high price of the equipment limits the implementation of the results and urges to find cheaper plasma-enhanced method of growth. For this purpose, a common glow discharge plasma setup was engaged to grow the nanostructures in an oxygen atmosphere on surfaces of samples installed on the anode of the electric circuit designed to sustain the glow discharge. An additional heater was mounted under the anode. The proposed combination allowed conducting the growth process under conditions of the delivery of the necessary heat flux and removal the excessive ion flux that can destroy the growing nanostructures because of sputtering. In the first set of experiments, the additional heater was not used, and the observed nanostructures were presented by grains (2D) of about 370 nm in diameter and 80 nm in thickness. This structure is supposedly formed because of action of the internal stresses in the oxide layer. After turning on the heater, the nanowires (1D) were the only nanostructures observed in the experiment, and since no nanowires were found in a case of heating the anode without plasma ignition, one can consider the plasma as a factor determining the nanowire growth.


Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4173
Author(s):  
Petra Šrámková ◽  
Zlata Kelar Tučeková ◽  
Michal Fleischer ◽  
Jakub Kelar ◽  
Dušan Kováčik

Biaxially oriented polypropylene (BOPP) is a highly transparent polymer defined by excellent mechanical and barrier properties applicable in the food packaging industry. However, its low surface free energy restricts its use in many industrial processes and needs to be improved. The presented study modifies a BOPP surface using two different atmospheric-pressure plasma sources operating in ambient air and capable of inline processing. The volume dielectric barrier discharge (VDBD) and diffuse coplanar surface barrier discharge (DCSBD) were applied to improve the wettability and adhesion of the 1–10 s treated surface. The changes in morphology and surface chemistry were analyzed by SEM, AFM, WCA/SFE, and XPS, and adhesion was evaluated by a peel force test. Comparing both plasma sources revealed their similar effect on surface wettability and incorporation of polar functional groups. Additionally, higher surface roughness in the case of VDBD treatment contributed to slightly more efficient adhesion in comparison to DCSBD. Although we achieved comparable results for both plasma sources in the term of enhanced surface wettability, degree of oxidation, and stability of induced changes, DCSBD had less effect on the surface deterioration than VDBD, where surface structuring caused an undesirable haze.


Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2069
Author(s):  
Antonella Uricchio ◽  
Fiorenza Fanelli

Low-temperature atmospheric pressure (AP) plasma technologies have recently proven to offer a range of interesting opportunities for the preparation of a variety of nanocomposite (NC) coatings with different chemical compositions, structures, and morphologies. Since the late 2000s, numerous strategies have been implemented for the deposition of this intriguing class of coatings by using both direct and remote AP plasma sources. Interestingly, considerable progress has been made in the development of aerosol-assisted deposition processes in which the use of either precursor solutions or nanoparticle dispersions in aerosol form allows greatly widening the range of constituents that can be combined in the plasma-deposited NC films. This review summarizes the research published on this topic so far and, specifically, aims to present a concise survey of the developed plasma processes, with particular focus on their optimization as well as on the structural and functional properties of the NC coatings to which they provide access. Current challenges and opportunities are also briefly discussed to give an outlook on possible future research directions.


2021 ◽  
Vol 9 ◽  
Author(s):  
Avinash Maharaj ◽  
Antonio D’Angola ◽  
Gianpiero Colonna ◽  
Samuel A. Iwarere

A plasma discharge in a Helium gas reactor at different pressures and at low currents (0.25–0.45 A) has been investigated by Computational Fluid Dynamic modeling coupled with the Maxwell’s equations. The results show different discharge dynamics across the pressure range (0.1–8 MPa), with an arc discharge obtained at high pressure and a low current arc discharge observed at atmospheric pressure. A large density gradient at higher pressure causes a strong natural convection effect in the reactor. This density gradient affects drastically the discharge shape and the velocity field at high pressures while at atmospheric pressure, a lower density gradient was observed resulting in a low velocity magnitude. It has been observed that the velocity magnitude is not affected by the electric current. The discharge electric potential has been calculated by considering the electrical characterization of the electrodes and numerical results have been compared with experimental results. The comparison shows a good agreement between the measured and calculated discharge electric potential at lower pressures. These devices can be used as plasma sources for wastewater treatment.


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