gas plasma
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2022 ◽  
Vol 92 (2) ◽  
pp. 232
Author(s):  
А.И. Пушкарев ◽  
С.С. Полисадов

The results of modeling and experimental investigation of the formation of anode and cathode plasmas in a vacuum diode with an explosive-emission cathode during the generation of a pulsed electron beam with a current density of 0.3-0.4 kA/cm^2 and an accelerating voltage of 300-500 kV are presented. It is shown that the concentration of the anode plasma does not exceed 10^10 cm^-3 and it does not significantly contribute to the operation of the diode. However, the complete desorption of molecules from the working surface of the explosive-emission cathode and the high efficiency of shock ionization of atoms ensure the formation of a cathode gas plasma with a concentration of 10^16 cm^-3. It is found that the charge of the explosive-emission plasma layer is significantly less than the charge of the electron beam and the main source of electrons is not an explosive-emission plasma, but a cathode gas plasma. In this case, the electron current is limited by the concentration of the cathode plasma. The use of a cathode with a developed surface (a cathode with a carbon fabric coating) allows increasing the total charge of the electron beam by more than 1.5 times without changing the cathode diameter and the anode-cathode gap.


2022 ◽  
Vol 2150 (1) ◽  
pp. 012026
Author(s):  
N M Barbin ◽  
A M Kobelev ◽  
D I Terent’ev ◽  
S A Titov

Abstract In this work, the composition and thermophysical properties of the “Reactor graphite-H2O” system at temperatures from 2123 to 3223 K are calculated. It was found that the main components of the vapor phase at a temperature of 2123-2923 K: carbon dioxide, carbon monoxide, water vapor, hydroxide, hydrogen, atomic hydrogen. At temperatures above 3223 K, oxygen and atomic oxygen are added to the gases present. The balances of uranium and plutonium are considered. Uranium at temperatures above 2123 K is present in the system in the form of gaseous and ionized uranium dioxide and trioxide. Plutonium at temperatures above 2123 K is present in the system in the form of gaseous and ionized plutonium oxide, gaseous plutonium dioxide. The calculation of thermophysical properties for the considered system is carried out.


Fuels ◽  
2021 ◽  
Vol 2 (4) ◽  
pp. 556-651
Author(s):  
Sergey M. Frolov

This review considers the selective studies on environmentally friendly, combustion-free, allothermal, atmospheric-pressure, noncatalytic, direct H2O/CO2 gasification of organic feedstocks like biomass, sewage sludge wastes (SSW) and municipal solid wastes (MSW) to demonstrate the pros and cons of the approaches and provide future perspectives. The environmental friendliness of H2O/CO2 gasification is well known as it is accompanied by considerably less harmful emissions into the environment as compared to O2/air gasification. Comparative analysis of the various gasification technologies includes low-temperature H2O/CO2 gasification at temperatures up to 1000 °C, high-temperature plasma- and solar-assisted H2O/CO2 gasification at temperatures above 1200 °C, and an innovative gasification technology applying ultra-superheated steam (USS) with temperatures above 2000 °C obtained by pulsed or continuous gaseous detonations. Analysis shows that in terms of such characteristics as the carbon conversion efficiency (CCE), tar and char content, and the content of harmful by-products the plasma and detonation USS gasification technologies are most promising. However, as compared with plasma gasification, detonation USS gasification does not need enormous electric power with unnecessary and energy-consuming gas–plasma transition.


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.


Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4249
Author(s):  
Diana Popescu ◽  
Florin Baciu ◽  
Catalin Gheorghe Amza ◽  
Cosmin Mihai Cotrut ◽  
Rodica Marinescu

Producing parts by 3D printing based on the material extrusion process determines the formation of air gaps within layers even at full infill density, while external pores can appear between adjacent layers making prints permeable. For the 3D-printed medical devices, this open porosity leads to the infiltration of disinfectant solutions and body fluids, which might pose safety issues. In this context, this research purpose is threefold. It investigates which 3D printing parameter settings are able to block or reduce permeation, and it experimentally analyzes if the disinfectants and the medical decontamination procedure degrade the mechanical properties of 3D-printed parts. Then, it studies acetone surface treatment as a solution to avoid disinfectants infiltration. The absorption tests results indicate the necessity of applying post-processing operations for the reusable 3D-printed medical devices as no manufacturing settings can ensure enough protection against fluid intake. However, some parameter settings were proven to enhance the sealing, in this sense the layer thickness being the most important factor. The experimental outcomes also show a decrease in the mechanical performance of 3D-printed ABS (acrylonitrile butadiene styrene) instruments treated by acetone cold vapors and then medical decontaminated (disinfected, cleaned, and sterilized by hydrogen peroxide gas plasma sterilization) in comparison to the control prints. These results should be acknowledged when designing and 3D printing medical instruments.


2021 ◽  
Vol 2064 (1) ◽  
pp. 012029
Author(s):  
I V Lopatin ◽  
Yu H Akhmadeev ◽  
S S Kovalsky ◽  
D Yu Ignatov

Abstract This paper presents the results of a study of an electron-ion-plasma alitization system using two arc plasma generators: a gas plasma generator based on a non-self-sustained arc discharge with a thermionic cathode “PINK” and a gas-metal plasma generator based on an arc discharge with a cathode spot. The system for discharges supplying and biasing of the samples assumes two sub-modes of operation: the ion cleaning sub-mode (ion sub-mode) and the sub-mode of samples electron heating (electron sub-mode), thus realizing the “elion” mode of the system operation. During the experiments, both the dependences of the average values of currents and voltages of discharges burning and probe measurements of the instantaneous plasma parameters values in both system operating sub-modes were investigated. It is shown, that the electron sub-mode of system operation is characterized by an increased burning voltage, which is caused by the formation of a positive anode drop of more than 10 V in the plasmas. Such a potential distribution in the discharges ensures effective heating of the samples by the discharges plasmas electron component.


2021 ◽  
Vol 2100 (1) ◽  
pp. 012005
Author(s):  
V G Brovkin ◽  
A I Klimov ◽  
I Ch Mashek ◽  
A S Pashchina ◽  
N M Ryazansky ◽  
...  

Abstract The results of a preliminary study of the interaction of supersonic gas-plasma flows created by a magneto-plasma compressor and a pulsed erosion plasma jet are presented. Stable initiation of the MPC discharge at atmospheric pressure was achieved for the first time. The advantage of using the coaxial arrangement of plasma jets sources for MPC discharge initiation is shown. A noticeable change in the shock wave front velocity and pressure (up to 20%), created during the MPC discharge and dispersed powders and liquid mixtures interaction, is discovered.


2021 ◽  
Vol 2021 ◽  
pp. 1-20
Author(s):  
Milad Rasouli ◽  
Nadia Fallah ◽  
Sander Bekeschus

Nanomedicine and plasma medicine are innovative and multidisciplinary research fields aiming to employ nanotechnology and gas plasma to improve health-related treatments. Especially cancer treatment has been in the focus of both approaches because clinical response rates with traditional methods that remain improvable for many types of tumor entities. Here, we discuss the recent progress of nanotechnology and gas plasma independently as well as in the concomitant modality of nanoplasma as multimodal platforms with unique capabilities for addressing various therapeutic issues in oncological research. The main features, delivery vehicles, and nexus between reactivity and therapeutic outcomes of nanoparticles and the processes, efficacy, and mechanisms of gas plasma are examined. Especially that the unique feature of gas plasma technology, the local and temporally controlled deposition of a plethora of reactive oxygen, and nitrogen species released simultaneously might be a suitable additive treatment to the use of systemic nanotechnology therapy approaches. Finally, we focus on the convergence of plasma and nanotechnology to provide a suitable strategy that may lead to the required therapeutic outcomes.


2021 ◽  
Vol 22 (21) ◽  
pp. 11446
Author(s):  
Fariba Saadati ◽  
Juliane Moritz ◽  
Julia Berner ◽  
Eric Freund ◽  
Lea Miebach ◽  
...  

Reactive oxygen species (ROS) have been subject of increasing interest in the pathophysiology and therapy of cancers in recent years. In skin cancer, ROS are involved in UV-induced tumorigenesis and its targeted treatment via, e.g., photodynamic therapy. Another recent technology for topical ROS generation is cold physical plasma, a partially ionized gas expelling dozens of reactive species onto its treatment target. Gas plasma technology is accredited for its wound-healing abilities in Europe, and current clinical evidence suggests that it may have beneficial effects against actinic keratosis. Since the concept of hormesis dictates that low ROS levels perform signaling functions, while high ROS levels cause damage, we investigated herein the antitumor activity of gas plasma in non-melanoma skin cancer. In vitro, gas plasma exposure diminished the metabolic activity, preferentially in squamous cell carcinoma cell (SCC) lines compared to non-malignant HaCaT cells. In patient-derived basal cell carcinoma (BCC) and SCC samples treated with gas plasma ex vivo, increased apoptosis was found in both cancer types. Moreover, the immunomodulatory actions of gas plasma treatment were found affecting, e.g., the expression of CD86 and the number of regulatory T-cells. The supernatants of these ex vivo cultured tumors were quantitatively screened for cytokines, chemokines, and growth factors, identifying CCL5 and GM-CSF, molecules associated with skin cancer metastasis, to be markedly decreased. These findings suggest gas plasma treatment to be an interesting future technology for non-melanoma skin cancer topical therapy.


2021 ◽  
Vol 11 (20) ◽  
pp. 9777
Author(s):  
Akikazu Sakudo ◽  
Yosuke Tsuji

Prions are highly resistant to physical or chemical damage, although previous studies have shown that STERRAD®, a hydrogen gas plasma sterilizer using radiofrequency (RF) discharge, has an inactivation effect. Here, the effect of hydrogen peroxide gas combined with dielectric barrier discharge (DBD) plasma and corona discharge plasma using a RENO-S130 sterilizer on scrapie prions was examined. Scrapie prion-infected mouse brain homogenate was air-dried on a cover glass, sealed in a Tyvek pouch, and subjected to RENO-S130 treatment using either non-lumen mode (28 min) or Eco mode (45 min) with hydrogen peroxide gas derived from 50% hydrogen peroxide. Control (untreated) samples were prepared on a cover glass using the same procedure but without exposure to RENO-S130. PrPres (proteinase K (PK)-resistant prion protein), an index of the conformational variant of prion protein (PrPSc), was decreased by treatment with RENO-S130 under both modes of operation. Specifically, PrPres was identified after the 1st and 2nd cycles of protein misfolding cyclic amplification (PMCA) in control samples but was below the detection limit in RENO-S130-treated samples. A bioassay showed that treatment of prions with RENO-S130 (non-lumen or Eco mode) significantly prolonged mouse survival time. Taken together, these findings show hydrogen peroxide gas combined with DBD/corona discharge plasma can inactivate prions by reducing prion propagation and prion infectivity. This treatment is potentially applicable to the sterilization of prion-contaminated heat-sensitive medical devices.


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