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The work carried out theoretical and experimental studies of a glow discharge in a space with a non-uniform gas density in cases of axisymmetric and planar arrangement of electrodes. In experimental studies, a nonuniform gas density in the interelectrode space was created by pumping gas at supersonic speed near one of the electrodes. The inhomogeneity of the gas density distribution in the interelectrode space was determined on the basis of theoretical calculations of the parameters of a supersonic jet formed by a Laval nozzle with a central body. It has been established that supersonic gas pumping makes it possible to organize a non-uniform distribution of gas density in the interelectrode space. It is shown that the characteristics of the discharge in terms of spatial localization, radiation intensity, and formation of near-electrode zones depend on the gas density distribution in the interelectrode space. [ABSTRACT FROM AUTHOR]

The work carried out numerical calculations to study the dynamics of plasma-chemical processes in a glow discharge in argon with small admixtures of methane CH4 at low pressures. The dynamics of changes in the main conversion products and various types of ions in the process of establishing a discharge are presented. It is shown that the time it takes for the conversion products to reach a stationary regime is about t = 8 s. The main products of methane conversion in steady state are atomic hydrogen, as well as atomic and molecular carbon. [ABSTRACT FROM AUTHOR]

Glow discharges are known to be limited for running at high current densities (typically below 0.1 A ⋅ c m − 2 ). Magnetically enhanced plasmas overcome this limitation, reaching up to two orders of magnitude higher current densities. However, the highest reported discharge current density hardly reaches 10 A ⋅ c m − 2 even in high power impulse magnetron sputtering (HiPIMS). Here, we report on the long (∼1 ms) pulsed operation of the magnetron in helium with an over-dense current (∼30 A ⋅ c m − 2 , usual for arcs) while preserving the glow mode. This regime defying the arcs was called hyper power impulse magnetron (HyPIM) because the power injected per pulse is several times higher than in HiPIMS for the same average power and pulse duration. HyPIM operation mode is distinguished from HiPIMS by the limited pulse voltage and is unsuitable for thin film deposition but may interest plasma switches. These huge currents were obtained for two cathode materials, molybdenum (Mo) and tungsten (W). Different experimental diagnostics bring insights into the physical phenomena governing the HyPIM plasma. A discussion on the role played by the metal atoms on the current unveils the origin of such exceptional glow current all along the pulse and the key role of the helium metastable atoms. A schematic of the kinetic steps of the HyPIM discharge is proposed. [ABSTRACT FROM AUTHOR]

In this study, we examined non-thermal atmospheric pressure plasma processes operating under varying conditions using different liquid and gaseous hydrocarbon materials. The light emission from the discharges were analyzed through optical emission spectroscopy to comprehend the products generated in different parameter space. The gaseous products from each of these analyses were also collected and analyzed through gas chromatography. Analysis of the optical emission from the discharge and concentration of the gaseous products show a linear trend between emission intensity ratio H α /C2 and gas concentration ratio H2/C2H x. Gas temperature and electronic excitation temperature of different experimental conditions were also compared and indicates that spark discharge relates to higher electronic excitation temperature compared to glow discharge of similar medium. Higher electronic excitation temperature leads to generation of different products from spark discharge compared to glow discharge. Glow discharge generates more of the intermediate products. Whereas spark discharge, because of its higher electronic excitation temperature, leads to higher rate of dissociation and therefore generates more of the dissociated products. Glow discharge, for example generates more of OH and H from the moisture present in the carrier gas as impurity, whereas spark discharge would generate more of H α and O particles further breaking down the OH bonds. Finally, UV–Vis analysis was performed on the liquid products of the discharge and reveals that the photo-centers and the newly generated soot nano particles absorb the UV range lights and some of the visible range light emission mostly up to ∼600 nm. [ABSTRACT FROM AUTHOR]

The effect of the dust grain flows on a spatial dusty structure in a stratum of a glow discharge in two inert gases (neon and argon) in a weak magnetic field was studied. The discharge parameters were determined that are necessary for the creation of three-dimensional dusty structures made from dust grains of the same size in both gases in a magnetic field. The dependences were obtained of the angular velocities of the dusty structures in the two gases on the magnetic field and on the gas pressure. The rotation speeds of the dust grains in the magnetic field were used to compare the ion fluxes acting on the dust formations. [ABSTRACT FROM AUTHOR]

Mars has nearly ideal conditions for CO2 dissociation by glow discharge plasmas. The directly generation of O2 and CO on Mars was considered to be feasible and practical for in situ resource utilization of Martian atmosphere to get respirable O2 and fuel. In this paper, we conduct several experiments under simulated Martian conditions to investigate the process and how the key parameters effect the generation of O2 and CO in CO2 glow discharge reactions. The yields of new products (i.e., O2 and CO) under various gas discharge work parameters (i.e., discharge power, frequency, voltage, gap between the discharge plane electrodes and gas pressure) were systematically investigated. The reaction mechanism and reaction path of CO2 glow discharge has been discussed. In our study the max yield of O2 by CO2 discharge dissociation was got about 21.8 g/h at 168 W which is very close to that of NASA MOXIE (Mars Oxygen In-Situ Resource Utilization Experiment) at the same power. Our results showed the great potentiality of glow discharge for the practicable technology of O2 and CO generation for in-situ resource utilization on Mars. [ABSTRACT FROM AUTHOR]

The parameters of the plasma of a low-pressure glow discharge in neon with microparticles, at which regions with equal values of the ion confinement efficiency in the cloud of microparticles are realized, are determined numerically. It is noted that such features are characteristic of dissipative synergetic systems controlled by the feedback. The simulation of a complex plasma of glow discharge in neon with microparticles shows that feedback in the plasma is realized through the source of the main losses of its energy—a cloud of microparticles. Controlling the discharge parameters by changing the concentration of microparticles in the cloud makes it possible to control the concentration of the ions in the plasma. [ABSTRACT FROM AUTHOR]

Purpose. To review and classify currently existing glow discharge models by the method of mathematical description of processes, pressure, gas type and electrode geometry. The article is aimed at creating a generalized model of the discharge, which will determine the influence of each parameter on the characteristics of the discharge. Methodology. To achieve the goals of the research, methods of theoretical analysis of scientific sources were used, as well as a mathematical method for describing a generalized discharge model based on an orthonormal basis, in particular a trigonometric basis. Findings. An overview of the glow discharge was conducted, a classification of models based on analytical methods in their basis was proposed. The vector of parameters common to all models is isolated. Also, during the analysis, a comparison of the characteristics of the models was carried out in the form of a table. A generalized model for the study of gas discharges by the method of modeling using orthonormal bases was proposed. As an example, the formation of a vector of variable parameters in the trigonometric basis is given. Originality. The article offers a generalized discharge model that demonstrates how a change in a specific parameter affects the discharge characteristics. Such a model allows you to simultaneously change the parameters of the model, accumulate reactions to changes in parameters in each test, and upon completion, based on the results of the analysis, isolate the effect of each parameter with a cumulative change in the parameters of the model. Practical value: The model allows analyzing the influence of various parameters on the discharge regardless of the specific conditions of the experiment. The use of an orthonormal basis for the representation of parameters makes it possible to identify which parameters have the greatest influence on the stability and efficiency of the discharge both individually and in combination with other parameters. This makes it possible to optimize these parameters to achieve the best results in specific conditions, making it a universal tool for researchers and engineers, which facilitates the analysis of the relationships between parameters and allows you to get a more complete picture of the system's behavior. [ABSTRACT FROM AUTHOR]

The sizes of dust particles capable of levitating in dust traps in striations in a glow discharge in all inert gases are quantitatively determined for the same discharge parameters. A more than twofold decrease in the particle size was established upon passing from the gas with the maximum ionization potential (He) to Xe. The dependence found in the experiment is interpreted from the point of view of the conditions of particle levitation. It is shown that in gases with a low ionization potential in the balance of forces, the ion drag force exceeds the force of gravity, while the absolute values of the forces decrease with decreasing particle size. The discovered effect can be used for fine trapping of dust particles in plasma traps. [ABSTRACT FROM AUTHOR]

The bactericidal components of air plasma jets generated by a direct-current glow discharge and a dielectric barrier discharge were studied using IR and UV absorption spectroscopy. The mole fractions of bactericidal components with an absorption spectrum band structure were determined by selecting a mole fraction value in the calculated spectrum that ensured correlation with the experimental spectrum. The spectra were calculated using the HITRAN spectral database and the Specair 3.0 program. The error in the mole fractions due to violation of the Bouguer–Lambert–Beer law when using absorption coefficients convoluted with the instrument function was determined. The mole fractions of bactericidal components with a continuous absorption spectrum were calculated using the Bouguer–Lambert–Beer law in a standard way. IR and UV absorption spectroscopy were shown to enable determination of the mole fractions for the full set of bactericidal components in air plasma jets of glow and barrier discharges. [ABSTRACT FROM AUTHOR]

Fast atom beam (FAB) source is used for surface activated bonding. This process is attracting attention as an essential process for next-generation semiconductor manufacturing. Traditional wafer direct bonding processes require annealing or cannot be directly bonded at room temperature. Therefore, there are restrictions on the materials that can be bonded and the combinations of materials that can be bonded. However, surface activated bonding has made it possible to directly bond dissimilar materials at room temperature. This technology is expected to be applied to the manufacturing of various MEMS and three-dimensional stacking of semiconductors. This bonding process involves bombarding the wafer surface with fast argon atom beam in a vacuum chamber. Irradiation removes oxide layer and contaminants, exposing dangling bonds. By pressing the wafers together, the dangling bonds are bonded together, and a strong bond is achieved. The device that generates this fast argon atom beam is FAB source. This device has been of the type that generates a saddle field electric field. However, this FAB source had a narrow beam irradiation area and was unable to support the recent increase in wafer diameter. Therefore, it was necessary to perform irradiation using multiple FAB sources. At production sites, there is a need to develop new FAB sources that can irradiate large areas. In this study, we developed FAB source in which the beam is generated by parallel plate electrodes. We performed a comparison with the saddle field type FAB source and found that the performance was inferior in initial experiments. Next, we improved the design to operate at higher voltages and increased the aperture area. Through these improvements, we have achieved performance superior to the saddle field type FAB source. [ABSTRACT FROM AUTHOR]

Time-resolved optical emission and absorption spectroscopy was used to analyze a 50 kHz Ar-NH3 dielectric barrier discharge operated in a homogeneous glow discharge regime at atmospheric pressure. In addition to the typical NH(A-X), N2(C-B), and Ar(2p-1s) transitions, a continuum emission linked to de-excitation of H 2 a 3 Σ g + states was detected between 180 and 250 nm and lasted for a long time after discharge extinction. Over the range of experimental conditions investigated, the emitting H 2 a 3 Σ g + states are proposed to be populated by collisions of H 2 X 1 Σ g + with Ar(1s) states during discharge, and by dissociative recombination of the vibrationally-excited ammonia ion (NH3+(v)) after the discharge. NH3+(v) is produced by charge transfer from Ar2+ to NH3, and it breaks into H 2 a 3 Σ g + (or H 2 c 3 Π u or H 2 d 3 Π u ) and NH upon gas phase recombination with a low-energy electron. Based on this proposed mechanism, a 1D fluid model was refined to include these reactions and used to simulate the emission intensity from H 2 a 3 Σ g + and revealed good agreement with experimental data. [ABSTRACT FROM AUTHOR]

A liquid sampling-atmospheric pressure glow discharge (LS-APGD) ionization source operating at a nominal power of 30 W and solution flow rate of 30 µL min−1 and supported in a He sheath gas flow rate of 500 mL min−1 was interfaced to an Orbitrap mass spectrometer and assessed for use in rapid identification of inorganic and organic arsenic species, including As(III), As(V), monomethylarsonic acid, dimethylarsinic acid, and arsenobetaine in a 2% (v/v) nitric acid medium. Mass spectral acquisition in low-resolution mode, using only the ion trap analyzer, provided detection of protonated molecular ions for AsBet (m/z 179), DMA (m/z 139), MMA (m/z 141), and As(V) (m/z 143). As(III) is oxidized to As(V), likely due to in-source processes. Typical fragmentation of these compounds resulted in the loss of either water or methyl groups, as appropriate, i.e., introducing DMA also generated ions corresponding to MMA and As(V) as dissociation products. Structure assignments were also confirmed by high-resolution Orbitrap measurements. Spectral fingerprint assignments were based on the introduction of solutions containing 5 µg mL−1 of each arsenic compound. [ABSTRACT FROM AUTHOR]

The influence of the addition of hydrogen on the electrophysical parameters and emission spectra of tetrafluoromethane under conditions of a direct current glow discharge is studied. It is established that the gas temperature changes nonlinearly with an increasing proportion of hydrogen in the plasma-forming mixture. The emission spectra of tetrafluoromethane plasma with hydrogen are obtained and analyzed. It is shown that plasma radiation is represented by atomic and molecular components, and the dependencies of the line radiation intensities on the external conditions of the discharge are determined by the excitation of emitting states during direct electron impacts. [ABSTRACT FROM AUTHOR]

A fundamental study of CO 2 / CH 4 plasma is performed in a glow discharge at a few Torr. Experimental and numerical results are compared to identify the main reaction pathways. OES-based techniques and FTIR (Fourier Transform Infrared) spectroscopy are used to determine molecules densities and gas temperature. Several conditions of pressure, initial mixture and residence time are measured. The main dissociation products are found to be CO and H 2 . The LoKI simulation tool was used to build a simplified kinetic scheme to limit the uncertainties on rate coefficients, but sufficient to reproduce the experimental data. To this aim, only molecules containing at most one carbon atom are considered based on the experimental observations. Obtaining a good match between the experimental data and the simulation requires the inclusion of reactions involving the excited state O (1 D) . The key role of CH 3 radical is also emphasized. The good match obtained between the experiment and the simulation allows to draw the main reaction pathways of the low-pressure CO 2 - CH 4 plasmas, in particular to identify the main back reaction mechanisms for CO 2 . The role of CH 2 O and H 2 O in the gas phase is also discussed in depth as they appear to play an important role on catalytic surface studied in the part II of this study. [ABSTRACT FROM AUTHOR]

In situ FTIR transmission experiments for CO 2 and CO 2 – CH 4 plasma were performed for a fundamental study of surface plasma interaction with cerium oxide ( CeO 2 ) as catalytic surface. Utilizing a DC glow discharge plasma reactor at low pressure, it was observed that CO 2 gas adsorbs in the surface forming tridentate carbonates and hydrogen carbonates. When CO 2 – CH 4 plasma is ignited, formate species were formed while carbonate species disappeared from the surface. The CeO 2 pellet has also been placed downstream the plasma in order to observe the role of the gas composition at the exit of CO 2 – CH 4 plasma on CeO 2 without any heating or strong electric field. In addition, the effect of water was investigated in several surface phenomena. OH groups play an important role in the reaction with tridentate carbonates to generate formates under plasma. The gas phase chemistry of the CO 2 – CH 4 plasma used here has been described in details in the part I of this work. The conclusions drawn on the gas phase contribute to the understanding of the observed phenomena on CeO 2 . These results enlighten the complex mechanisms occurring during CO 2 – CH 4 plasma reactions on surfaces that could help in the improvement of CO 2 recycling. [ABSTRACT FROM AUTHOR]

Plasma nitriding in a glow discharge is a relatively new and extremely promising method of steel surface hardening. Ion-nitrided samples show a tendency to a longer lifespan during severe wear and cyclic loading compared to the traditional gas nitriding. However, a significant disadvantage of plasma thermochemical processes is their relatively long duration of about 20–30 hours. As a result, the surface treatment becomes inefficient and too expensive. As known, the properties of the nitrided layer, its phase composition and growth rate depend strongly on the parameters of the plasma nitriding (temperature, time, gas pressure, composition of the gas mixture, etc.). At the same time, there is still an open question regarding the choice of optimal modes of hardly-nitrided stainless-steels plasma nitriding, which will ensure of high treatment efficiency and obtaining of high-hardness strengthened layers with a controlled structural–phase composition. As established, to prevent the formation of Сr–N metastable phases’ precipitations on the surface of stainless steels, the appearance of which leads to deterioration of their corrosion performance, the treating temperatures should be limited: ≤ 450 °C. Low-temperature plasma nitriding provides the formation of a homogeneous nitrided layer of ‘white’ phase with a nitrogen concentration of 15 at.% and more. This phase ensures the nitrided-surface hardness of 1500 HV, which is by 4-to-5 times greater than the hardness of the untreated one. The possibility of the plasma-nitriding intensification by increasing the gas pressure in the reactor in the range from 130 to 400 Pa is shown. This provides an increase in the thickness of the nitrided layer and its hardness from ≈ 8 µm up to ≈ 18 µm and ≈ 700 HV up to ≈ 1500 HV, accordingly. Significant growth dynamics of the nitrided layer on the stainless-steels’ surfaces is achieved by determining the optimal 3-component gas mixture with a content of 55%Ar–30%N2–15%H2 that ensures the obtaining of a hardened layer with a thickness of ≈ 30 µm and a surface hardness of 1100 HV.

Microplasma at atmospheric pressure has been widely used in many fields due to the lower power consumption, higher plasma density, as well as better uniformity and stability. In this work, the microplasma characteristics of direct current atmospheric pressure glow discharge, including discharge morphology and electrical properties have been investigated with various interelectrode gaps (10–600 μ m) and discharge currents (1–6 mA), and simultaneously, a finite element simulation has been conducted to obtain the distribution of the electric field and particle density. The evolution of cathode layer, anode layer and Faraday dark space at this scale was captured with a higher spatial resolution (∼1 μ m) for the first time, demonstrating that the cathode layer, especially the cathode sheath rather than the positive column, plays a dominant role in the transition of the microplasma. As the gap shrinks to a size less than cathode layer (∼40 μ m), the cathode sheath with a high electric field is compressed, leading to a rapid decrease of the discharge voltage. The discharge voltage remains basically unchanged regardless of the discharge current, because the electric field in the cathode sheath is limited by the accumulated space charge. The experimental results are well verified and explained by the simulation results. This study provides an in-depth understanding of the glow discharge mechanism at microscale, and of the stability of glow discharge at atmospheric pressure, and benefits to future research on the atmospheric pressure large-area microplasma and its related application. [ABSTRACT FROM AUTHOR]

The work describes the possibility of using a conducting fluid model (single-fluid model) to analyze physical phenomena observed in the inhomogeneous gas discharge plasma. A technique for calculation of the heat fluxes and temperature fields in a discharge in a cylindrical glass tube with metal sections is proposed. The presence of metal sections leads to a change in the thermal balance in the plasma volume. Specific calculations have been carried out for conditions with significantly different thermal conductivity coefficients of gases (argon and helium) and metals (steel and copper). Two cases of the discharge state—diffuse and constricted—are considered. Spatial distributions of heat sources, temperature fields and heat fluxes depending on the gas type, and discharge tube configuration are presented. The considered discharge configuration and the proposed calculation method can be useful for practical applications, for example, in laser physics. [ABSTRACT FROM AUTHOR]

Ozone production in a planar dielectric barrier discharge (DBD) in atmospheric oxygen in different discharge modes was investigated. Results show that the gas temperature in discharge channel depends strongly on discharge mode, with a value of 300–310 K in glow regime and 440–465 K in streamer regime. Ozone production yield in glow DBD is much higher than that in streamer one, with the best yield of 342.6 and 162.6 g/kWh, respectively. Gas temperature in discharge channel relates to the effective discharge area of DBD, which is a small fraction of the whole electrode surface in streamer DBD compared with nearly the whole surface in glow DBD. The gas temperature in the channel plays a decisive role in the conversion of oxygen atoms to ozone as well as the ozone equilibrium concentration. Excellent performance of glow DBD demonstrates the high energy efficiency and reliability for practical application of planar DBD-based ozone generator. [ABSTRACT FROM AUTHOR]

The formation of a plasma jet by a glow discharge in an air flow in the electrode system of a so-called gliding arc is considered at an average discharge current of 100 mA and an air flow rate of 0.1 g/s. The displacement of a negative glow region over the cathode surface is analyzed using a sectioned plane cathode. A method for the plasma jet diagnostics by measuring the charged particle current on a special diagnostic electrode placed inside the jet is proposed. Based on the data obtained, the characteristic features of the current transfer inside the jet are obtained. The charged particle concentration inside the jet is estimated for the proposed current transfer model. [ABSTRACT FROM AUTHOR]

The plasma density and electron temperature are governed and influenced by the high-power pulsed magnetron sputtering parameters (e.g., operating voltage, pulse width, and working gas pressure), which are critical factors in determining the quality of high-power pulsed magnetron sputtering deposited films. This article proposes a vertical cylindrical magnetron sputtering plasma model based on the equivalent magnetic charge model to study the particle spatiotemporal and electron temperature distribution in high-power pulse magnetron sputtering. The results show that the electron converges in the highest magnetic field region in high-power pulsed magnetron sputtering during the increase of argon pressure from 3 to 7 Pa. The electron density distribution width ratio decreases from 80 to 64%, reducing target utilization. At the same time, for every 1 Pa increase in pressure, the average electron temperature in the discharge region is reduced by about 2 eV, which is inversely proportional to the pressure. As the voltage increases to 1000 V, the electric field intensity increases to 2 × 105 V/m, and the distribution of sputtered particles tends to be closer to the electrode, and the cathode dark zone changes from 2 to 1 mm. The increase in voltage has little effect on the shape of the plasma particle density distribution, but the electron temperature near the electrode increases to 19 eV at high voltages. The study reveals the change of plasma particles during the magnetron sputtering process, which is of guidance for magnetron sputtering. [ABSTRACT FROM AUTHOR]

Plasma nitriding in a glow discharge is a relatively new and extremely promising method of steel surface hardening. Ion-nitrided samples show a tendency to a longer lifespan during severe wear and cyclic loading compared to the traditional gas nitriding. However, a significant disadvantage of plasma thermochemical processes is their relatively long duration of about 20-30 hours. As a result, the surface treatment becomes inefficient and too expensive. As known, the properties of the nitrided layer, its phase composition and growth rate depend strongly on the parameters of the plasma nitriding (temperature, time, gas pressure, composition of the gas mixture, etc.). At the same time, there is still an open question regarding the choice of optimal modes of hardly-nitrided stainless-steels plasma nitriding, which will ensure of high treatment efficiency and obtaining of high-hardness strengthened layers with a controlled structural-phase composition. As established, to prevent the formation of Сr-N metastable phases' precipitations on the surface of stainless steels, the appearance of which leads to deterioration of their corrosion performance, the treating temperatures should be limited: ≤450 °C. Low-temperature plasma nitriding provides the formation of a homogeneous nitrided layer of 'white' phase with a nitrogen concentration of 15 at.% and more. This phase ensures the nitrided-surface hardness of 1500 HV, which is by 4-to-5 times greater than the hardness of the untreated one. The possibility of the plasma-nitriding intensification by increasing the gas pressure in the reactor in the range from 130 to 400 Pa is shown. This provides an increase in the thickness of the nitrided layer and its hardness from ≈8 μm up to ≈18 μm and ≈700 HV up to ≈1500 HV, accordingly. Significant growth dynamics of the nitrided layer on the stainless-steels' surfaces is achieved by determining the optimal 3-component gas mixture with a content of 55%Ar-30%N2-15%H2 that ensures the obtaining of a hardened layer with a thickness of ≈30 μm and a surface hardness of 1100 HV. [ABSTRACT FROM AUTHOR]

The International Standard ISO 18115‐1 on terminology in surface chemical analysis has been revised with clarifications, modifications, and deletions to more than 70 terms and with the addition of more than 50 terms in response to trends, issues, and needs identified by the surface analysis community. This revision adds terminology and concepts associated with emerging methods such as atom probe tomography, near ambient pressure XPS, and hard X‐ray photoelectron spectroscopy. It includes 25 new and revised terms to ensure that the description of resolution is consistent across all surface analysis methods. The 630 terms in the document cover words or phrases used in describing the samples, instruments, and concepts involved in surface chemical analysis. The terms have been collated into subject specific sections to ensure that related terms can be found easily. [ABSTRACT FROM AUTHOR]

This article describes the vacuum system of the KTM tokamak and also presents an algorithm for the technological mode of conditioning of the tokamak vacuum chamber (VC) performed before and during the experiment and its influence on production of glow discharges. The applied procedure of the vacuum chamber preparation, despite the atmospheric leakage in 2021, provided the possibility to develop conditions for conducting experiments at the KTM tokamak and to obtain discharges with the highest currents and discharge durations for this facility achievable at the time of writing of this article. As a result of the analysis of experimental data, the conditions have been established under which plasma discharges are not formed. [ABSTRACT FROM AUTHOR]

Changes in the surface of micron-sized melamine-formaldehyde microparticles in dust structures in a glow-discharge plasma in Ne and Kr are experimentally studied. The microparticles are placed in plasma-dust structures with subsequent extraction. Two effects depending on the exposure time in plasma are established in the experiment: a comprehensive decrease in the particle size and a change in the morphology of their surface. A model is considered, which makes it possible to estimate the contribution of various mechanisms of the interaction of charged plasma particles with the surface of melamine formaldehyde. The estimates obtained are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In order to further investigate the conditions and the coupling mechanisms for generating the hollow cathode effect (HCE) for the process optimization in the field of surface modification, the plasma distribution and density in single glow and double glow hollow cathode discharge (HCD) were explored by experiments and simulations based on the two-dimensional fluid model. Additionally, we investigated the effects of the key parameters on the plasma density, the electron temperature and the potential field during the HCD. The experimental and simulation results showed that the high plasma density is owing to the HCE in the hollow cathode. It is found that there is a critical pore diameter for generating HCE, which is approximately the sum of the thickness of the plasma sheath and four times the electron-neutral mean free path in the single glow discharge while twice thickness of the plasma sheath and four times the electron-neutral mean free path in the double glow discharge. The HCE in the double glow discharge can be observed when the ignition voltage that the source cathode voltage be 250 V greater than the workpiece cathode voltage can be met while the PD value is about 1.5 ∼ 3.8 Torr ⋅ mm. Consequently, we believe that our investigation on the plasma characteristics of hollow cathode in glow discharge will contribute to the development of the more optimal processing parameters for the application of the glow plasma discharge phenomena. [ABSTRACT FROM AUTHOR]

Features of the plasma jet formation by the glow discharge in an air flow in the system of electrodes of a low-current coaxial plasmatron are considered at an average discharge current of 100 mA and a mass air flow of 0.1 g/s. The peculiarity of experimental conditions is the positive polarity of the internal (potential) electrode of the plasmatron. Features of the discharge maintenance in the plasmatron are investigated. The technique of plasma jet diagnostics by measuring the gas temperature and the charged particle current on the special diagnostic electrode placed inside the jet is proposed. Based on the data obtained, the characteristic features of current transfer inside the jet have been obtained. The charged particle concentration inside the jet is estimated for the proposed model of current transfer. [ABSTRACT FROM AUTHOR]

The photoluminescence of lithium fluoride nanocrystals and crystals placed on the anode of an atmospheric-pressure glow discharge in helium and exposed to the discharge components was studied. The luminescence spectra showed that color centers with new properties inherent to near-cluster centers were formed in unannealed nanocrystals after exposure to the discharge. However, the conditions necessary for formation of near-cluster centers were eliminated upon annealing of the nanocrystals. These necessary conditions were partially restored when annealed nanocrystals were exposed to the discharge. This opened new possibilities for elucidating the processes and mechanisms of formation of centers with new properties. [ABSTRACT FROM AUTHOR]

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Modulated laser absorption spectroscopy is an ideal technique for evaluating flow-field parameters and determining flow-field quality by measuring the atoms dissociated in high-temperature environments. However, to obtain the absolute number density of atoms in the flow field, it is necessary to compare the measured modulated absorption spectroscopy signal with a known atomic concentration and establish a quantitative relationship through concentration calibration. Nevertheless, it remains a challenging task to prepare transient atomic samples with known concentrations that meet the calibration requirements. This study utilized the alternating-current glow discharge technique to dissociate oxygen in the air flow, resulting in the continuous generation of oxygen atoms. The absolute number densities of the generated oxygen atoms were determined by measuring the direct absorption spectra of centered on 777 nm for oxygen atoms. The number densities of the generated atoms were finely tuned by adjusting the discharge parameters. Throughout the 120-min continuous operation of the discharge system, the concentration of excited-state oxygen atoms remained stable within the range of (2.51 ± 0.02) × 108 cm−3, demonstrating the remarkable stability of the transient atomic concentration generated by the glow discharge plasma. This observation suggests that the generated atoms can be utilized as a standardized atomic sample of known concentration for absolute concentration calibration purposes. [ABSTRACT FROM AUTHOR]

This study demonstrates that the surface roughness of a copper sample can be controlled by treating it with glow discharge plasma. It is established that the main process affecting the morphology and composition of the surface is oxidation. Treatment causes the formation of various copper oxide nano- and microstructures on the surface of a copper sample. It is shown that, in the parameter range studied, the working gas pressure has a more significant effect on the formation of various structures than the glow discharge current density. As a result of the treatment, various stages of the surface oxidation are observed, caused by differences in the surface temperature. [ABSTRACT FROM AUTHOR]

Three-dimensional plasma-dust formations consisting of calibrated dust particles differing in sizes and material densities are studied. The characteristic features of the structures formation in stratified glow discharge were studied, as well as their shapes and dynamics in the external magnetic fields. From several types of powders, the spatially separated double structures were obtained, which filled the dust trap, being located in different stratum phases. For each part of the structure, the average rotational velocities were obtained as functions of the magnetic field. In the range, in which the rotation mechanism depends on the particle size and the ion drag force is dominant, the rotational velocity was numerically estimated with allowance for the parameters variation along the stratum. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of an axial magnetic field on several plasma parameters of hollow electrode argon abnormal glow discharge. The discharge is generated by applying a DC voltage ranging from 0-6KV. By varying the pressure and magnetic field strength (0-25mT), the plasma potential, frequency, and degree of ionization were measured. The plasma potential, frequency, and degree of ionization were evaluated using spectroscopic measurements of the electron temperature and density. The results of the experiment show that the plasma potential decreases as the magnetic field strength increases, while the plasma frequency increases for lower pressure but reaches a constant value for higher pressure due to the increasing number of excitation collisions among the plasma-charged particles. The degree of ionization, determined using the ideal gas law, shows a near-linear relationship with the axial magnetic field at both low and high pressure. [ABSTRACT FROM AUTHOR]

Sputtering is the process of depositing thin films on the surface of a material using plasma. Plasma is created by adding extremely high energy to a surrounding gas, which turns into plasma. The plasma is directed towards the material on which you want to deposit the films, and the plasma particles interact with the material to form a thin film of the desired material. Oxygen plasma has many important applications in industry. When adding a small percentage of it, it can change the properties of the plasma significantly. In this research, the spectrum of the plasma generated from the application of different energies (175,200,250,300) watts of direct current was studied on a mixture of argon and oxygen gases in a ratio of (9: 1). The spectrum emitted from the plasma was measured Within the wavelength range (400-800) nm, the plasma parameters (Te, ne, λD, ND) were diagnosed by examining the spectrum corresponding to the applied power using optical emission spectroscopy (OES). The results showed an increase in the electron temperature and electron density with the increase in the applied power. Where the highest and lowest values for the electron temperature and density were respectively (1.645-1.305) eV, (26.03-25.36) x 1017/cm3.

This paper investigates the impact of an axial magnetic field on several plasma parameters of hollow electrode argon abnormal glow discharge. The discharge is generated by applying a DC voltage ranging from 0-6KV. By varying the pressure and magnetic field strength (0-25mT), the plasma potential, frequency, and degree of ionization were measured. The plasma potential, frequency, and degree of ionization were evaluated using spectroscopic measurements of the electron temperature and density. The results of the experiment show that the plasma potential decreases as the magnetic field strength increases, while the plasma frequency increases for lower pressure but reaches a constant value for higher pressure due to the increasing number of excitation collisions among the plasma-charged particles. The degree of ionization, determined using the ideal gas law, shows a near-linear relationship with the axial magnetic field at both low and high pressure.

The influence of cold plasma of atmospheric-pressure glow discharge on the surface properties of rice grains has been studied. It has been established that as a result of the impact of nonthermal atmospheric-pressure glow-discharge plasma on the seed surface, the surface becomes hydrophilic and is characterized by a decrease in the contact angle, an increase in surface energy, and enhancement of surface roughness, indicating the effective formation of polar groups on the surface of rice grains. [ABSTRACT FROM AUTHOR]

Copyright of Al-Mustansiriyah Journal of Science is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Formation of iron oxyhydroxide nanostructures was experimentally studied by low-temperature plasma electrolysis including spectroscopic investigation of glow-discharge plasma between a metal electrode and liquid at atmospheric pressure. The results of characterization of the structure and composition of the formed nanoparticles were discussed. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The thin layer of Silicon film has been deposited on molybdenum samples at room temperature for the first time by a mixture of silane and He gas (90 % He+10 % SiH4) using the glow discharge method as an application of a low -Z protective material to a fusion reactor. Siliconization has been conducted for 170 min with the gas pressure of 4–6 ×10-2 torr. the DC power supply parameters were as follows, the anode voltage of 500–600 V, and the current of 190-210 mA. The films have been characterized by using scanning electron microscopy, EDX, X-ray diffraction, FTIR, and AFM. SEM images show that the silicon coating covers the entire surface smoothly and there is no boundary for granulation. The thickness of the coating has been estimated to be around 450 nm using AFM measurement. The Si-O-Si tensile vibrations and Si-H tensile vibrations have been detected using FTIR method.

The characteristics of post-cathode plasma maintained by a self-made DC short glow-discharge plasma generator with grid electrodes were measured by optical emission spectroscopy. The discharge existed in an abnormal glow discharge mode at a voltage of 250–400 V and a helium pressure of 3–15 Torr and a discharge gap of 3 mm. The results indicate that the intensity distribution of helium atom spectral lines in the post-cathode space differs from that in the post-anode space. The temperature of electron excitation in the post-cathode plasma reaches its peak of 1500–3000K at 5–6 mm from the grid cathode. The difference in the intensity distributions of helium atom spectral lines in the post-cathode and post-anode spaces is associated with electron generation mechanism in these cases.

The possibility of changing the silicon surface morphology at certain glow discharge parameters is shown. It is established that oxidation is the main process influencing the surface morphology during glow discharge plasma treatment. As a result of processing in the investigated parameter range, various stages of the surface oxidation process are observed: the formation of a uniform oxide layer and the formation of nano- and microstructures of silicon oxide. It is shown that these processes lead to surface modification, which acquires stable hydrophilic and superhydrophilic properties. [ABSTRACT FROM AUTHOR]