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Carbon nanoparticles produced from alcohols by pulsed spark discharge in liquid (PSDL) was investigated in this work. The spherical carbon particles with about 10 nm diameter can be produced by PSDL, which were similar to the commercial carbon particles. With the increase of discharge power, the mean diameter of carbon particles was decreased and the size distribution was more uniform. Meanwhile, the yield of carbon produced from ethanol was more than from methanol that may be attributed to the more carbon atoms in ethanol compared with the same volume of methanol. In addition, the mechanism of carbon produced from alcohols by PSDL was also analyzed. The possible reactions were given according to the production analysis. This work presents a new method for carbon nanoparticles production and the results can play a guidance role in producing nanometer materials by plasma reforming. [ABSTRACT FROM AUTHOR]

Microwave discharge was established in the central part of a long quartz tube mounted perpendicular to the waveguide to investigate the behaviour of the O-atom density within the interface between highly non-equilibrium plasma and neutral gas approaching thermal equilibrium. A movable catalytic probe was mounted upstream the drifting gas of a drift velocity approximately 1.5 m s −1 to determine the gradients in the O-atom density in the dark non-equilibrium gas. The gradient at the axis of the discharge tube decreased with the increasing distance from the glowing plasma. At a gas flow of 4 L h −1 and a discharge power of 1000 W the gradient was approximately 7 × 10 22 m −3 /m close to the plasma edge, whereas 10 cm away from the plasma edge, it was approximately 1 × 10 22 m −3 /m. The behaviour of the O-atom density at a fixed position of the probe but different gas flows and discharge powers was measured within the interface, where samples of different coefficients for heterogeneous surface recombination of O-atoms were mounted. The O-atom density increased with the increasing power, exhibited a maximum at the gas flow 1.5 L h −1 , and a strong dependence on the type of a material was found and explained qualitatively. [ABSTRACT FROM AUTHOR]

Capacitively coupled RF glow discharge was used to form novel coatings of SiO x C y H z using varying proportions of trimethylsilyl acetate (TMSAc) monomer and the carrier gas argon. The properties of the TMSAc-based plasma polymers produced depend significantly on the proportion of argon in TMSAc/Ar gaseous mixture, which ranged from 0 % to 75 %. Reaction mixtures containing less than 50 % Ar produced hydrophobic polymers, for which the indentation hardness values were less than 1.5 GPa. Seventy-five percent argon in the reaction mixture yielded a crosslinked carbon-rich organosilicon structure with a hardness of 6 GPa. As many applications require good stability in a liquid environment, the TMSAc-based coatings were immersed in phosphate buffered saline (PBS) for 14 days. Because any material used in a medical application must be resistant to the techniques used for sterilization, the prepared coatings were subjected to a standard sterilization procedure using UVC radiation. A degree of the structural changes induced by both environments corresponded to the argon ratio used for production of thin films. Possible degradation mechanisms were examined and discussed. Using 7.7–21.4 % Ar during the deposition process led to the TMSAc-based plasma polymers exhibiting good resistance to the prolonged immersion in PBS and UVC sterilization. • Plasma polymerization of TMSAc using RF capacitively coupled glow discharge. • Properties of TMSAc-based coatings depend on the argon ratio in the TMSAc/Ar mixture. • Prolonged immersion in PBS and UVC sterilization degraded the TMSAc-based surfaces. • The degree of degradation depends on the argon ratio in the reaction mixture. • Possible degradation mechanisms are discussed. • Using 7.7–21.4 % argon significantly improved the stability of prepared coatings. [ABSTRACT FROM AUTHOR]

Innovative plasma processing provides localized heating of grounded metallic surfaces under low pressure. Here we exploit a specifically designed Cylindrical Capacitive Coupled Discharge (CCCD), Radio-Frequency (RF) powering the inner cylinder and keeping the outer one grounded. Both cylinders have a longitudinal slit. These slits are aligned to each other and faced to a grounded metallic plate (target) placed underneath. When RF power is applied, the plasma glows inside the inner tube cavity, but it leaks out through the slits and spreads onto the surface of the target as a linear slab of plasma. The parametric study of the process focuses on the nature of gas (Argon and Nitrogen), the pressure range (0.8–50 mbar), the RF power (100–1800 W), and the cylinders/plate gap distance (1 or 8 mm). The optimized operation of the plasma system provides the highest ion production in front of the plate. The fastest heating condition increases the target temperature to 614 °C within 1s exposure to plasma. Furthermore, simulations using the Plasimo™ software package gives several other essential parameters such as the ion flux and their energy carried to the plate. Experimental and numerical results are in good agreement. This device has demonstrated the proof-of-principle for plasma heating of metallic surfaces. • Linear plasma slab is formed facing a metallic plate using a Capacitive Coupled Discharge. • Moving striations are observed in Radio-Frequency (RF) Argon plasma while standing striations are formed in RF Nitrogen plasma. • The efficiency of the discharge is mainly studied in terms of energy deposited to the plate, by varying the nature and the pressure of gas, the RF power, and the geometrical parameters. • Plasma processing can provide efficient localized heating of grounded metallic surfaces under low pressure. [ABSTRACT FROM AUTHOR]

The microwave discharge cusped field thruster is a novel electric propulsion concept developed for the space-borne Gravitational Wave detection mission. It is an effective combination of the cusped magnetic field and the ECR microwave plasma source, which provide the thruster strong confinement for the plasma and the ability to operate on low mass flow rate conditions. To meet the requirements on the high accuracy, low noise thrust over a wide range, a series of studies are carried out on the microwave discharge cusped field thruster. Since the magnetic field strength is one of the critical factors with a significant impact on the thruster, a plume plasma diagnosis is performed to analyze the discharge performance and plasma characteristics with different magnetic field strength conditions. A Faraday probe, a retarding potential analyzer, and an emissive probe are employed to characterize the plume. The results show that the variation of the magnetic field strength performs strong effects on the plume structure, the ion acceleration, and the electron conduction process. As the magnetic field strength weakens, the single-peaked plume profile transforms to a hollow cone structure, which is attributed to the conversion of acceleration mechanism. The thruster prototype performs a continuous thrust of 2–26.9 μN and a highest specific impulse of 248s with superior reproducibility in a low mass flow rate of 0.1sccm. • An MW-DC hybrid discharge is achieved in a blend mode. • An efficient microwave plasma generator, CTLR, is creatively applied on an electric propulsion device. • A newfound acceleration phenomenon in a CFT is revealed. • A multiparameter plasma diagnosis is conducted to study the thruster. [ABSTRACT FROM AUTHOR]

An ion-induced electron emission cathode is applied for the first time in micro electric propulsion devices. In this investigation, ion-induced electron emission is operated on an annular LaB6 emitter for the neutralization and ion extraction of a microwave discharge HEMP Thruster (High Efficiency Multi-staged Plasma Thruster). A plume plasma diagnosis is performed with a Faraday probe and a retarding potential analyzer to analyze the discharge characteristics and plasma parameters. The results show that the ion-induced electron emission cathode can provides an emission current of over 0.4 mA. Compared with the condition with a thermionic cathode, there is a reduction in the thruster extracted ion current due to the deficiency of the emission current. The emission current shows different trends over anode voltage in different position configurations, which are affected by the incident ion flux and ion energy. Since the ion-induced electron emission cathode is free of power supply and propellant, it is of significant potential for low-power electric propulsion systems. • Ion-induced electron emission is applied in micro plasma thruster for the first time. • The ion-induced electron emission cathode is free of electricity and propellant. • A novel typed of plasma-based micro electric thruster, the microwave discharge HEMP Thruster, is operated for the investigation. • It is indicated that the Kinetic Electron Emission (KEE) is the dominant effect in typical conditions. [ABSTRACT FROM AUTHOR]

Various dyeing techniques are utilised at dyeing different types of fabrics and current study discuss the possibility of using a single dye bath for the given purpose. The current study utilised a radio frequency glow discharge plasma source maintained at near atmospheric conditions (around 200 mbar) in nitrogen and air environments to treat cotton, nylon, and polyester fabrics. Similar surface modifications produced in all three types of fabrics by OH and O radicals tailoring them more sensitive to certain dyes and glues. SEM images verified that bulk material is well protected by plasma treatment and the presence of additional surface functionalities (hydroxyl, carboxylic, and carbon-nitrogen groups) on the treated fabric surfaces were determined by FTIR and XPS analysis. The plasma-treated samples were dyed in a single dye bath using a reactive dye under atmospheric neutral conditions and a significant enhancement in fabric dyeability (cotton- 124%, nylon- 61%, polyester- 38%) was observed. PVA glue was used for fastening the fabric samples and the adhesion was analysed through tensile measurement. Well improved adhesion capabilities (148%, 95%, and 57.3% respectively for cotton, nylon, and polyester) also confirm the advantages of RF glow discharge plasma treatment for unified fabric processing. • RF glow discharge plasma for unified fabric processing. • Fabric surface modification with O and N containing surface functionalities. • The enhancement in fabric dyeability with reactive dyes. • Enhanced adhesion capabilities with PVA based glues. [ABSTRACT FROM AUTHOR]

In gridded ion thrusters, it is generally known that the ion extraction from the grid significantly decreases the neutral density. However, because it is difficult to measure the density inside thruster, it has not been revealed how the local density decreases including the inhomogeneous effects (e.g., gas injection, ionization, and ion recombination). To investigate these inhomogeneous effects, two-photon laser-induced fluorescence (TALIF) and Direct Simulation Monte Carlo (DSMC) applied to a gridded microwave discharge ion thruster. First, the TALIF directly measured the density distribution. Second, the DSMC reproduced the measured density distribution. From these results, the main effect of the ion extraction is the decrease of ion recombination at the grid. This decrease makes the density distribution more sensitive to the ionization distribution and increases the inhomogeneity. Based on this knowledge, we propose improvement against 'simulated experiment without ion extraction' and 'decoupled numerical simulation' which reproduce the density distribution of ion extraction under the condition without ion extraction by decreasing flow rate. Specifically, we suggest that the grid transparency is expanded and the rest discrepancy is adjusted by the flow rate because the difference of the inhomogeneous effect due to gas injection can be reduced. • Measurement of neutral density distribution inside gridded ion thruster by TALIF. • Comparison of neutral density distribution between without and with ion extraction. • DSMC simulation was performed to reproduce TALIF measurement. • Inhomogeneity of gas injection, ionization, and ion recombination on neutral density. • Expansion of grid transparency is better solution to reproduce sate of ion extraction. [ABSTRACT FROM AUTHOR]

The paper studies the plasma-assisted chemical vapor deposition of a-C:H:SiO x coatings in plasma of non-self-sustained arc discharge with a hot cathode combined with inductively excited radio-frequency (RF) discharge. The a-C:H:SiO x coatings are produced by polyphenyl methylsiloxane (PPMS) dissociation in plasma with and without RF discharge. The optical emission spectroscopy is used to study the PPMS dissociation process. Raman spectroscopy provides the structural investigations of the obtained coatings, while the energy dispersive X-ray spectroscopy is used to analyze the chemical composition. It is shown that the mechanical and tribological properties of a-C:H:SiO x coatings depend on the RF discharge power and the bias voltage amplitude of the substrate. It is demonstrated that substrate bias voltage can be reduced during the coating deposition in combined discharge without significant degradation of its mechanical and tribological properties due to the better dissociation and ionization of PPMS vapor molecules in inductively excited RF discharge. • a-C:H:SiO x coatings were prepared by combined RF + PACVD system. • Inductively coupled RF discharge used for improved PPMS vapors dissociation. • RF discharge power affected structure and chemical composition of a-C:H:SiO x coatings. • a-C:H:SiO x coatings had low wear rate of 2.7·10−7 mm3/N·m. [ABSTRACT FROM AUTHOR]

The present work aims to analyze the mutual influence of channels in a combined discharge based on the RF inductive and DC discharges and to find the conditions under which the gain in the plasma density can be obtained. A cylindrical plasma reactor with a diameter of 20 cm and a length of 20 cm has been used as an object of research. The measurements have been carried out in argon at pressures of 0.08 and 8 Pa, as well as in air at pressures of 8 and 18.7 Pa. The performed experiments have shown that the gain in plasma density in the combined discharge is possible under conditions when the plasma density in DC discharge overcomes that in the inductive one. As a rule, such situation occurs when inductive discharge is in a E-mode. Due to the higher value of the plasma density, provided by the DC channel, the RF power input through the inductive discharge increases. A synergistic effect appears, and the resulting plasma density exceeds the sum of the densities, specific to the inductive and DC discharges separately. • The gain in plasma density in the combined RF and DC discharge can be obtained. • A synergistic effect appears when the resulting plasma density exceeds the sum of the densities, characteristic of the inductive and DC discharges separately. • The DC channel can be locked in the combined discharge. • The properties of the combined discharge are close to that in the inductive one near antenna and to DC discharge near the cathode if the electron mean free path is smaller than the distance between antenna and electrodes. [ABSTRACT FROM AUTHOR]

The experimental results show that when the pressure is constant, with the increase of power, the thrust-power ratio of the thruster decreases, and the wind speed and thrust increase, but the increase rate gradually decreases and finally tends to be stable；When the pressure is 5.5 kPa, The rate of increase in thrust decreases the slowest, that is, the thruster has the maximum thrust potential at 5.5 kPa, and when the input power is greater than 75 W, the relative maximum thrust can be generated, reaching 14.8 μN; At the same time, with the increase of input power, the thrust - power ratio increases first and then decreases; When the input power is constant in the range of 15–65 W, as the air pressure increases, the wind speed decreases, and the thrust and thrust-power ratios all have local extremes, that is, when the air pressure is 8 kPa, it reaches the regional maximum, the maximum is 12.7 μN and 0.45 μN/W, respectively, at 16 kPa, it reaches the minimum value of the area, and the minimum is 4 μN and 0.14 μN/W, respectively. By comparing the discharge images under different atmospheric pressures, it can be concluded that the thrust generated by the accelerated collision of particles with a single short-time large current pulse is less than that generated by the accelerated collision of ions with a long-time small high-frequency pulse discharge, and the particle collision probability is the main reason affecting the wind speed; Meanwhile, with the increase of input power, the "virtual electrode" formed by the accumulation of positive ion space charge reduces the increase rate of wind speed and thrust. • We found that the discharge characteristics of many thrusters in near spaces are different from the discharge characteristics under atmospheric pressure and low pressure. • Experimental data shows that: the wind speed generated by the thruster increases with the decrease of air pressure • Under the same input power, the thrust has a maximum value of 8 kPa and 16 kPa • The phenomenon that the thrust reaches saturation with the increase of power under different air pressures • But the thrust growth potential is the largest at 5.5 kPa, and after the input power is about 75W, the thruster can produce the maximum value under all air pressure conditions • The maximum thrust and the maximum thrust power ratio of the thruster appear at 5.5 kPa and 8 kPa respectively. [ABSTRACT FROM AUTHOR]

The cusped field thruster has become a candidate thruster in next-generation space science missions due to its low complexity and potential long life over a wide range of thrust conditions. However, the reduction of propellant utilization and, as a result, the total performance degradation has emerged in works on cusped field thruster downscaling. In this work, a coaxial resonator is utilized to feed the microwave (MW) into the near-anode region of the cusped field thruster, which contributes to ionization at a relatively low mass flow rate. With a LaB6 thermionic emission cathode, the thruster can operate in two modes: MW excited mode and the MW-DC mixed mode. The results show that the thruster can operate with a minimum mass flow rate minimum of 0.004 mg/s and achieves a continuously adjustable thrust from 1.9 μN to 30.8 μN. The performance variation characteristics over the three control parameters (anode voltage, mass flow rate, and MW power) are considered. Additionally, a plume plasma diagnosis is performed with a Faraday probe and a retarding potential analyzer to analyze the discharge performance and plasma characteristics with different operating conditions. • An MW-DC combined discharge is achieved in a blend mode. • An efficient microwave plasma generator, CTLR, is creatively applied on an electric propulsion device. • Thrust which fulfills the primary application demands of the GW observation mission is achieved. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents results on the spatial structure of 27-MHz discharges sustained in a diffusion-controlled regime by the wave field of Trivelpiece-Gould modes. Methods of probe diagnostics of high-frequency discharges with magnetized plasma production are applied. [Copyright &y& Elsevier]

Abstract: A self-consistent fluid–plasma model of argon discharges produced in the field of surface waves at low gas pressure is presented in the study. The radial structure of the discharge resulting from the model is built by complete profiles of the discharge characteristics which smoothly cover the plasma core and the wall sheath of the discharges. The analysis is in terms of varying gas pressure. [Copyright &y& Elsevier]

Abstract: The paper presents a review on recent development in modelling and diagnostics of diffusion-controlled gas discharges produced in the fields of travelling waves as well as on their instabilities, with a stress on the results obtained in the Plasma and Gas-discharge Physics Group at Sofia University. Directed to basic features of the discharge, the discussion is on argon discharges with unmagnetized and magnetized plasma production. [Copyright &y& Elsevier]

The study presents results from probe diagnostics of 27 MHz argon-discharges with magnetized plasma production in the field of travelling Trivelpiece–Gould modes. The external magnetic field and the gas pressure are varied in the experiment. Radial profiles of the plasma density and the electron temperature are obtained and discussed in terms of the regimes of the discharge maintenance. [Copyright &y& Elsevier]

During the wall conditioning of the MT-I spherical tokamak, the addition of nitrogen impurity in the argon and helium microwave discharges has been investigated using the optical actinometric technique. This simple technique exploits the change in emission intensity of the selected Ar/He lines at constant partial pressure to normalize the electron energy distribution function with changing plasma conditions provided that both transitions have close excitation thresholds and similar dependence of excitation cross-sections. Accordingly, the selected line intensity of the nitrogen can be related to the ground state concentration of the nitrogen molecules and ions involving in optical emission. The electron temperature for both discharges has been determined separately from the Boltzmann plot method. For measurement of electron number density empirical formulas have been derived from the isolated spectral lines of Ar–I (750.38 nm) and He–I (587.56 nm & 667.81 nm). Stark broadening of well-isolated argon Ar–I (750.38 nm) and helium He–I (587.56 nm & 667.81 nm) lines have been used after de-convolution of other broadening contributions. It is observed that the electron temperature reduces with time indicating the plasma cooling with the addition of nitrogen impurity in the chamber. • Sensing of Nitrogen impurity content in MT-I tokamak discharge through emission spectrum during wall conditioning. • Optical actinometric technique is used to measure the concentration of the nitrogen impurity. • Boltzmann plot method is used to measure the electron temperature of argon and helium discharges. • Electron density is determined from the Stark broadening after de-convolution of Voigt profile of spectral lines. [ABSTRACT FROM AUTHOR]