Anode Plasma Research Articles

The deflection of a wide electron beam from the longitudinal axis of the source with a plasma cathode and plasma anode

An electron source with a plasma cathode based on a low-pressure arc discharge having a grid (layer) stabilization of the emission (cathode) plasma boundary and the open edge of the anode plasma has been used to study the deflection of a broad intense submillisecond electron beam from the electron source axis by a leading magnetic field. Measurements of the energy density distribution of the generated electron beam were made both under conditions of its deflection and in the mode of “direct” transport, when the collector target is in direct line of sight from the emission electrode. It was experimentally shown that the stability of the electron source operation with a beam deflection significantly increases. It allows to expand the range of beam parameters, which opens up new possibilities for use the electron source for both scientific and technological purposes.

Some features of anodic plasma electrolytic processes in aqueous solution

Effect of the electrolyte temperature on the current-voltage and temperature-voltage characteristics of the anodc plasma electrolytic treatment of a steel sample, as well as the features of the formation of a stable vapour-gaseous envelope were considered. Spectral analysis revealed the glow of the heated anode zone without lines of elements of electrolyte and electrode. The result of the influence of the plasma electrolytic treatment mode on the surface condition was shown.

Plasma electrolytic polishing of nitrided steel under force convection condition

The effect of plasma electrolytic polishing in an ammonium chloride electrolyte under force convection condition on the characteristics of medium carbon steel after anodic plasma electrolytic nitriding was investigated. The morphology of the steel surface was studied using a metallographic microscope. The phase composition of the surface layers was studied using an X-ray diffractometer. Treatment specimens were tested under dry friction conditions with a counter body made of bearing steel. Corrosion studies were performed using potentiodynamic polarization curves in a 3.5 % sodium chloride solution. Nitriding increased the surface hardness up to 1130 HV due to the formation of a nitride-martensite layer with an outer oxide layer. After polishing of the nitrided surface, the loose outer part of the oxide layer containing microcracks and pores is removed, surface lightening has occurred. The reduction of the wear rate of 45-fold and the corrosion current density of 4.8-fold of nitrided steel by plasma polishing without changing the structure of the diffusion layers was shown.

Computer simulation of high current vacuum arc with developed anode spot

A self-consistent simulation of anode heating by 4.5 kA vacuum arc during the half-wave of 50 Hz current with 1 m/s contact opening was carried out. The calculations were done in the framework of hybrid high current vacuum arc model, which treats ions and atoms as macroparticles with the help of particle-in-cell methods, but electron subsystem is treated as massless fluid with quasineutrality assumed. The occurrence of an anode plasma plume (similar to that found in experiments) was obtained as a result of modeling. It is shown that the energy flux of line radiation from the interelectrode plasma to the anode is a critical reason of the appearance and maintenance of the anode plume.

Anodic plasma electrolytic saturation of the Ti6Al4V alloy with nitrogen and oxygen

The structure of the Ti6Al4V alloy, its microhardness, surface roughness, and wear and corrosion resistance after anodic plasma electrolytic saturation with nitrogen and oxidation of the surface were investigated. It was shown that an electrolyte containing ammonia and ammonium chloride provided the saturation of the alloy with nitrogen and oxygen and the formation of TiO2 with rutile structure and a nitrogen solid solution in the alloy. The treatment at 750 °C during 5 min results in an increase in microhardness up to 790 HV and a decrease in surface roughness by 1.4-fold owing to the anode dissolution of titanium. The dry friction coefficient of the samples after treatment at 700 °C can be 3.5-fold reduced through sliding with a speed of 0.144 and a load of 105 N. These regimes allow diminishing the wear rate of samples of titanium alloy after their wear testing by 2 orders of magnitude. Corrosion resistance in Ringer’s solution does not deteriorate after treatment at a low temperature, when an oxide layer forms on the surface.

C-V Characterization and Electric Parameters of ZrO2 Received by UV Stimulated Plasma Anodizing

Low temperature technologies creating metals oxides are a promising solution for formation integral circuit elements. In this report the electric properties of zirconia (ZrO2) received by low temperature (∼ 400° C) UV stimulated plasma anodizing have been investigated. Zirconia is a potential high-k dielectric material with potential applications as agate insulator in transistors. This dielectric distinguished by good electric parameters. For this purpose, we used C-V characterization technic and calculate dielectric constant, flatband voltage, threshold voltage, bulk potential, work function, oxide effective charge, charge concentration. The C-V measurement was carried out on Keithley Instrument Semiconductor Parameter Analyzer 4200, oxide thickness was measured by reflectometer – MprobeVis System.

Characteristics of anodic glow pulsed plasma

Using the triple Langmuir probe, the characteristics of the glowing plasma adjacent to a constricted anode is obtained. The glow discharge is generated by applying a train of high voltage pulses between the constricted anode and cylindrical cathode with a pulse frequency of 2 kHz at 50% duty cycle. The axial plasma characteristics along the central line of the anode shows crest and trough resembling a double layer. The bulk plasma showed uniform electron density outside the glow. The visual images show an enhancement in the volume of the glow consistent with the discharge current. The mechanism behind the particular double layer characteristics around the anode is being explained in detail.

Dynamic Characteristics of the Spark Channel Plasma in Nitrogen Trigatron Investigated by the Laser Mach–Zehnder Interferometer

The spark channel plasma generated in the atmospheric nitrogen trigatron is studied with the laser Mach–Zehnder (M–Z) interferometer. The development of the spark channel plasma is described by analyzing the temporal and spatial evolution of the plasma electron density from the interferograms. The regions of the shock wave and the plasma are distinguished by the phase shift. Different spatial distributions of the anodic and cathodic plasma channels are obtained. The anodic spark channel shows good axial symmetry with constant radial expansion velocity. On the periphery of the main spark channel, a secondary spark channel occurs simultaneously in the cathodic region. After the collision of the two channels, the stagnation forms in the overlapping region and the secondary channel merges with the main one gradually. The leftward expansion velocity of the secondary channel is higher than the rightward velocity of the main channel, but both of them are lower than that near anode. The speculation on the production of the secondary spark channel is given and its influence on the development of the spark discharge in the gap is discussed in this work.

Surface Modification of Steel by Anodic Plasma Electrolytic Boronitriding and Polishing

The paper shows the possibility of plasma electrolytic polishing of the steel surface after its chemical-thermal treatment. Positive results of the plasma electrolytic polishing are obtained for low carbon steel after its anodic plasma electrolytic boronitriding. An X-ray diffractometer and a scanning electron microscopy were used to characterize the phase composition of the modified layer and its surface morphology. Surface roughness was studied with the use of a roughness tester. The hardness of the treated and untreated samples was measured using a microhardness tester. Corrosion properties of the samples treated surfaces were evaluated using potentiodynamic polarisation tests in solution of sodium chloride. The reduction of the surface roughness of 1.7 times and the corrosion current density of 1.5 times of boronitrided steel by plasma polishing using mode of current interruption for 2 min without changing the structure of the diffusion layers is shows.

Study of Plasma Electrolysis Method on Starch-Based Hybrid Latex Synthesis

The plasma electrolysis is a rich source of free radicals, it commonly induces unusual chemical reaction. This paper focus to study plasma electrolysis induces grafting reaction between latex and starch to prepare a functional material – ether bond – with radicals as the initiator to produce hybrid latex which presume has acoustic property. By the method of plasma electrolysis, the reaction can take place and the difference of polarity between the reactants can be overcome. The synthesis – both by using anodic and cathodic plasma – is said to work qualitatively when the characterization results by using Fourier Transformation Infrared Spectroscopy (FTIR) arises a new ether bond waves at around 1560 cm-1. The synthesis processes – both by using anodic and cathodic plasma – were investigated more specifically by looking at the effect of electrolyte, Na2SO4 concentration used with variations of 0.02; 0.03; 0.04 M to the efficiency of synthesis. The applied operating voltage of the process are 567.5 and 340.5 volt for anodic and cathodic, respectively. The reaction time is 10 minutes, and the efficiency of synthesis is represented by % yield of hybrid latex per kJ of electric energy consumption. The obtained efficiencies – from anodic and cathodic – were 0.04; 0.02; 0.01 and 0.18; 0.13; 0.12, for each of electrolyte concentrations, respectively.

Study of Plasma Electrolysis Method on Starch-Based Hybrid Latex Synthesis

The plasma electrolysis is a rich source of free radicals, it commonly induces unusual chemical reaction. This paper focus to study plasma electrolysis induces grafting reaction between latex and starch to prepare a functional material – ether bond – with radicals as the initiator to produce hybrid latex which presume has acoustic property. By the method of plasma electrolysis, the reaction can take place and the difference of polarity between the reactants can be overcome. The synthesis – both by using anodic and cathodic plasma – is said to work qualitatively when the characterization results by using Fourier Transformation Infrared Spectroscopy (FTIR) arises a new ether bond waves at around 1560 cm-1. The synthesis processes – both by using anodic and cathodic plasma – were investigated more specifically by looking at the effect of electrolyte, Na2SO4 concentration used with variations of 0.02; 0.03; 0.04 M to the efficiency of synthesis. The applied operating voltage of the process are 567.5 and 340.5 volt for anodic and cathodic, respectively. The reaction time is 10 minutes, and the efficiency of synthesis is represented by % yield of hybrid latex per kJ of electric energy consumption. The obtained efficiencies – from anodic and cathodic – were 0.04; 0.02; 0.01 and 0.18; 0.13; 0.12, for each of electrolyte concentrations, respectively.

Oxygen reduction reaction at few-layer graphene structures obtained via plasma-assisted electrochemical exfoliation of graphite

Few-layer graphene structures with a surface decorated with oxygen functional groups and sulfur-containing groups have been obtained during electrochemical exfoliation of graphite performed in the cathodic and anodic plasma modes. Conductivity of a synthesized carbon material has been estimated and its catalytic activity towards the oxygen reduction reaction has been studied. For the few-layer graphene structures synthesized in the anodic plasma mode, a considerable catalytic effect has been observed, which involved decrease in overpotential of the oxygen reduction and increase in contribution of a four-electron oxygen reduction in the overall process. This effect is shown to be determined by the surface carbonyl groups which are the active centres of the four-electron oxygen reduction at potentials less than −700 mV vs. Ag/AgCl.

Plasma electrolytic oxidation ceramic coatings proceed by porous anodic film

Ceramic coatings were performed on aluminum through plasma electrolytic oxidation (PEO) in a Na5P3O10 solution with various concentrations of NaOH. It was revealed that the concentration of NaOH affected the types of anodic films and the activity of plasma discharges. Emphatic investigation was performed on the coatings fabricated in the electrolyte with addition of 1 g L−1 NaOH, focusing on the coating microstructure evolution and coating corrosion resistance. Some coatings were detached from the substrate, showing that the oxide particles on the anodic film C/S interface underwent profile variations from hemisphere to polygon, and its interpore distance decreased over time. The formations of pores of anodic films and plasma discharge of the PEO coatings were both easy to occur around the existing pores and the existing discharge channels. Fractured cross-section showed that a pancake-like structure corresponded to a discharge channel, a cavity, and a barrier layer protrusion whose area was similar to that of the corresponding pancake-like structure. The data of potentiodynamic polarization measurements showed that the sample treated with PEO for 10 min possessed the lowest icorr value of 4.97E-8 A cm−2, the most positive Epit value of −0.63 V, and the highest Rp value of 2.66E5 Ω cm2. EIS data of 10 min sample exhibited the highest R2 value of 1.61E6 Ω cm2, demonstrating the best corrosion resistance among these samples.

PLASMA ASSISTED CONVERSION OF CARBON DIOXIDE IN LOW-PRESSURE GAS DISCHARGES

Experimental results of comparative study of carbon dioxide conversion efficiency to CO and O2 in the plasmas of different low-pressure discharges are presented. Inductively coupled plasma source, magnetron discharge and anode layer discharge in Hall-type ion source were used in CO2 pressure range 0.5…3 mTorr. It is shown that the best combination of high conversion rate with significant energy efficiency of the conversion is demonstrated by the ICP source.

2D3V kinetic simulation of Hall effect thruster, including azimuthal waves and diamagnetic effect

Axial-azimuthal (2D3V) full-kinetic PiC+MCC-model was built to simulate dynamics of Hall effect thruster discharge plasma taking into account azimuthal waves and diamagnetic effect. The transition from ignition to the steady-state regime was simulated. Calculation of discharge ignition shows a significant distortion in the shape of the magnetic field caused by high azimuthal-drift current. This effect and intensive ionization lead to the fact that full potential drop localizes in a thin non-magnetized cathode layer. In the steady-state regime, the distortion of the magnetic field is small. Plasma divides into three regions: dense anode plasma where ionization occurs; magnetic layer where ions accelerate and quasineutral cathode-side plasma (plume). The steady-state regime is subject to auto-oscillations at a gas-transit frequency (20 kHz ‘breathing modes’). Also, two types of azimuthal instabilities have been observed: gradient drift instability and electron cyclotron instability. All these instabilities lead to collisionless ‘anomalous’ electron transport across the magnetic field. Kinetic effects also were considered. It was found that the electron distribution function evolves from initial isotropic (Maxwellian) to essentially anisotropic due to electric field heating. Isotropy is partially restored inside anode plasma due to collisions.

A Conical Ion Diode with Self-Magnetic Insulation of Electrons

The results of studying the generation of a gigawatt-power pulsed ion beam formed by a diode in the mode of self-magnetic insulation of electrons are presented. Studies were carried out at the TEMP-4M accelerator in the mode of generating two pulses: the first is negative (500 ns, 150–200 kV) and the second is positive (150 ns, 250–300 kV). The formation of anode plasma occurs during the explosive emission of electrons during the first pulse. To improve the efficiency of generating an ion current, a conical geometry of the diode was proposed in which the electron-drift length exceeds that in the previous diode structures by factor of 2. It was found that the energy efficiency in the conical diode increased to 15–17%, while the ion-beam energy density at the focus increased to 2–3 J/cm2; the beam consisted of protons and carbon ions. The efficiency of suppression of the electron component of the total current in the diode was analyzed and the calculations of the electron-drift duration and ion acceleration were performed. It is shown that in the diode of the new design, efficient plasma formation occurs on the entire working surface of the graphite anode, while the plasma concentration may limit the ion current.

Fluctuation of arc plasma in arc plasma torch with multiple cathodes**Project supported by the National Natural Science Foundation of China (Grant Nos. 11875256, 11675177, and 11705202) and Anhui Provincial Natural Science Foundation, China (Grant No. 1808085MA12).

Fluctuation phenomena commonly exist in arc plasmas, limiting the application of this technology. In this paper, we report an investigation of fluctuations of arc plasmas in an arc plasma torch with multiple cathodes. Time-resolved images of the plasma column and anode arc roots are captured. Variations of the arc voltage, plasma column diameter, and pressure are also revealed. The results indicate that two well-separated fluctuations exist in the arc plasma torch. One is the high-frequency fluctuation (of several thousand Hz), which arises from transferring of the anode arc root. The other is the low-frequency fluctuation (of several hundred Hz), which may come from the pressure variation in the arc plasma torch. Initial analysis reveals that as the gas flow rate changes, the low-frequency fluctuation shows a similar variation trend with the Helmholtz oscillation. This oscillation leads to the shrinking and expanding of the plasma column. As a result, the arc voltage shows a sinusoidal fluctuation.

Theoretical model for magnetically insulated flow with both negative and positive ions

Negative and positive ions crossing the anode-cathode gap of a magnetically insulated transmission line (MITL) can cause non-negligible current loss and energy deposition on the electrodes, which may lead to the formation of anode plasma and the growth of cathode plasma. Furthermore, gap closure could occur due to the expansion of cathode plasma and anode plasma. In this paper, a model for magnetic insulation of both negative ion flow and positive ion flow is developed. The operating voltage V of the MITL is expressed as a function of the total current I0 and the boundary current Ib. The total current and the boundary current of the MITL are derived at saturated and self-limited flows, respectively. In addition, particle-in-cell simulations are implemented for the validation of the theoretical model. The thickness and density of the magnetically insulated ion layers are analyzed, and an empirical expression for space charge factor g is obtained through simulation results. This work extends the understanding of magnetically insulated ion flow in MITLs.

Effect of Plasma-Assisted Electrochemical Treatment of Glassy Carbon Electrode on the Reversible and Irreversible Electrode Reactions

A glassy carbon electrode is modified by generating cathodic and anodic electrolytic plasma near its surface. Voltage pulses of amplitude up to 250 V, pulse-on time of 10 ms, and rise time <0.5 µs in the Na2SO4 aqueous solution are used to form plasma. It is found that, as a result of treatment by the anodic plasma, the glassy carbon surface acquires electrocatalytic properties toward the oxygen reduction reaction, whereas the cathodic plasma has no noticeable effect as compared to the pristine glassy carbon. At the same time, a pronounced effect of plasma-assisted electrochemical treatment of surface on the electron transfer rate constants is found only for the [Fe(CN)6]4–/3– redox reaction. By contrast, for the outer-sphere ([Ru(NH3)6]2+/3+) and inner-sphere (Fe2+/3+) reactions, the effect is not observed. It is supposed that the observed electrocatalytic effect toward the oxygen reduction reaction is caused by the formation of carbonyl fragments of functional groups, which are active centers of oxygen reduction, on the surface of glassy carbon electrode under the action of anodic plasma. However, they have no pronounced effect on the [Ru(NH3)6]2+/3+ and Fe2+/3+ redox systems.

Algorithm of calculation of focal parameters of profile electron beams, formed by the gas-discharge electron guns

An algorithm of calculation of the focal distance of a hollow conical electron beam, formed by high voltage glow discharge electron guns, as well as the calculation of the diameter and thickness of a focal ring of such a beam, are considered in the article. The proposed algorithm is based on the model of free moving of electrons in the anode plasma and formed on the base of the laws of electron optics with using the methods of discrete mathematics and minimax analysis. Obtained simulation results allow to find the important regularities, which characterized the dependencies of focal parameters of a hollow conical electron beam, formed by the high voltage glow discharge electron guns, on the constructive parameters of electrodes’ system of the electron gun.