A Vapor-Air Discharge with a Porous Electrolytic Cathode at Atmospheric Pressure

An experimental investigation is performed for the first time of the structures and electrical and thermal characteristics of a vapor-air discharge between a porous (solid cylindrical body and hollow cylinder) electrolytic cathode and a solid anode in the range of current from 0.2 to 8 A with an interelectrode spacing of 2 to 200 mm for electrolytes of different compositions and concentrations with vertical and horizontal orientations of the plasma column in space at atmospheric pressure. An electrode of a new type is developed, namely, a porous electrolytic cathode (PEC), which makes it possible to produce cone-shaped, multichannel, and mixed discharges. The moist, boiling, and film modes of PEC operation are revealed. It is found that the heat loss on a PEC depends on the mode of its operation. The minimal heat loss is observed in the moist cathode mode, in which the electrolyte is delivered to the cathode working surface in the form of vapor only. In so doing, an almost complete regeneration occurs of heat delivered to the cathode from discharge plasma. It is found that the characteristics of a vapor-air discharge between a PEC and electrolytic anode depend significantly on the composition and concentration of the PEC electrolyte. The discharge voltage fluctuations and the nonuniform pattern of distribution of electric field intensity are revealed. The results of experimental investigation of a vapor-air discharge with a PEC are generalized in the form of an empirical formula.     

A Vapor-Air Discharge between Electrolytic Anode and Metal Cathode at Atmospheric Pressure

An experimental investigation is performed of the structure, mechanism, and electrical and thermal characteristics of a vapor-air discharge between an electrolytic anode (EA) and a metal cathode (MC) in a wide range of parameters at pressure P = 8×10⁴ to 10⁵ Pa, current I = 0.02 to 60 A, interelectrode spacing l = 0.1 to 40 mm, and metal cathode diameter d _c = 1 to 40 mm. The main types of vapor-air discharge with EA are identified. The possibility of burning of a multichannel discharge between a metal cathode and an electrolytic anode at atmospheric pressure is demonstrated for the first time, and a vapor-air discharge with a diffuse plasma column is investigated at high currents and large interelectrode spacings. It is determined that the electrical and thermal characteristics depend significantly on current, interelectrode spacing, electrolyte composition and concentration, geometric shape, diameter, and cooling of the MC. The significant effect of the vapor-air discharge on the electrolytic anode surface is revealed. Transverse waves are observed on the electrolyte surface. Significant turbulent mixing is observed for the first time on the electrolyte-plasma interface in the case of a vapor-air discharge with electrolytic anode at atmospheric pressure and high currents.     

Numerical Investigation of the Effect of the Cathode Geometry on the Characteristics of an Electric Arc

The effect of the cathode geometry on the characteristics of an electric arc is treated. It is found that the characteristics of plasma in discharges with cathodes of different geometry (cone, sphere, cylinder) are almost the same on condition of equality of the areas of current-conducting surfaces. It is assumed that a ring-shaped arc discharge may be realized in the case of axisymmetric arc spot on the external side surface of a cylindrical cathode.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 3, 2005, pp. 359–366.Original Russian Text Copyright © 2005 by R. M. Urusov and T. E. Urusova.     

Calculation of a flow of plasma in the vicinity of a profiled surface of an electric arc cathode

Some features are treated which are characteristic of a flow of arc plasma in the vicinity of a profiled cathode surface. Comparison of theoretical and experimental results leads one to assume that the formation of a plasma circulation zone in the vicinity of a profiled cathode surface contributes to reducing the erosion of the cathode material.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 2, 2005, pp. 175–180.Original Russian Text Copyright © 2005 by A. Zhainakov R. M. Urusov, and T. E. Urusova.     

A multichannel discharge between a stream electrolytic cathode and a metal anode at atmospheric pressure

An experimental investigation is performed of the structure and current-voltage characteristics (CVC) of a multichannel discharge (MD) between a stream electrolytic cathode (SEC) and a metal anode, as well as of the density of SEC and anode current in a wide range of values of current I = 0.02–10 A, interelectrode spacing l = 5–50 mm, and anode diameter d _a = 5–40 mm. The development of cathode spots on the SEC surface is studied. It is found that a cathode spot of SEC may have various shapes and structures (regular circle, horseshoes, filamentary spots, and so on). The CVC of a multichannel discharge between SEC and metal anode depends significantly on I, l, and d _a , as well as on the material of the anode and on the composition and concentration of electrolyte. The dependence of the density of SEC current on discharge current is nonmonotonic. It is for the first time that a bundle-like MD between SEC and metal anode and multichannel and diffuse discharges between the plasma region and stream electrolytic cathode are observed, and their characteristics are investigated.     

Investigation of High Voltage Discharges in Low Pressure Gases Through Large Ceramic Superconducting Electrodes

A device has been built and tested, in which a ceramic superconducting cathode and a copper anode cause electrical discharges in low pressure gases, at temperatures between 50 and 70 K. The electrodes are connected to a capacitors array charged up to 2000 kV; peak currents are of the order of 10⁴ A. The cathode has the diameter of 10 cm and is fabricated by OCMTG technology. In discharges at voltage above 500 kV two new phenomena were observed, probably related to each other. First, the discharge does not look like a spark, but is a flat, glowing discharge, which originates from the whole surface of the superconducting electrode. Furthermore, a radiation pulse is emitted at the discharge, which propagates orthogonally to the cathode, towards the anode and beyond it, in a collimated beam, apparently without any attenuation. The radiation pulse carries an energy of 10^–3 J at least. The features and the nature of this radiation have been investigated by several means, still it was not possible to identify it; we can only exclude that it is electromagnetic radiation or any other radiation with energy-momentum relationship E=cp.     

The energy balance and the mechanism of discharge transport on the surface of a thermionic cathode in an arc discharge

Modes of burning of an electric arc are treated under conditions in which the thermionic current from the cathode is much lower than the arc current. The conditions on the cathode surface are refined; it is demonstrated that the hypothesis of ion transport of discharge does not contradict the energy balance on the cathode surface.Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 1, 2005, pp. 011–020. Original Russian Text Copyright © 2005 by V. P. Polishchuk.     

High-current electron sources based on gaseous discharges

We review the operation of a ferroelectric plasma source (FPS) with enhanced plasma density and of high-current hollow cathode (HC) and hollow anode (HA) discharges. Different schemes (arc sources, magnetron and FPS) were used for ignition and sustaining the HC and HA discharges with current amplitude ?4 kA.These discharges are characterized by a positive anode potential with respect to the hollow electrode walls and the plasma density and temperature inside the hollow electrode cavity reach ∼3×10¹⁹m⁻³ and ?12 eV, respectively. It was shown that the incorporation of the FPS in the HA and HC enables one to develop a compact high-current electron source. The characteristics of an electron diode with FPS, HA and HC were studied under an accelerating voltage ?250 kV and ∼400 ns pulse duration. It was shown that these sources allow the generation of an electron beam with a cross-sectional area of 0.01 m² and amplitude up to 1-2 kA.     

VUV Radiation spectra of erosion plasma of a jet of high-current diaphragm discharge in vacuum

Experimental results are given of spectral investigations of radiation of a cathode jet of varying chemical composition produced by a diaphragm discharge in a vacuum ultraviolet spectral region (115–190 nm) under conditions of magnetogasdynamic flow of plasma over a decimeter-scale interelectrode gap.Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 1, 2005, pp. 032–038. Original Russian Text Copyright © 2005 by E. V. Kalashnikov, A. G. Bedrin, S. N. Rachkulik A. N. Zhilin V. K. Elts.     

Absorption of molecular radioiodine from the water vapor-air flow

Sorption of ¹³¹I₂ from the water vapor-air medium on inorganic nanocomposite materials was studied. All the nanocomposite materials synthesized, containing 1, 2, 4, and 8 wt % Ag in various chemical forms, remove ¹³¹I₂ from the water vapor-air flow with more than 99% efficiency.     

Kinetics of the initial stage of electrolytic deposition of metals III. Galvanostatic conditions

The kinetics of the initial stage of the electrolytic deposition of a thin metal film onto an inert cathode are considered for the case when the electric current flowing through the electrolytic cell is held constant with time. In studying the process the Gibbs-Thomson effect is taken into account and the cases of pure ohmic control, volume diffusion control and phase boundary transition control are examined separately. Expressions are derived for the radius of a single crystallite, the mean crystallite radius and the overvoltage as functions of time and current strength for each of the above types of growth control. Formulae are also obtained for the maximum overvoltage, the time taken to reach it and the maximum number of crystallites on the cathode as functions of the electric current. The analysis shows that the decrease in the maximum number of crystallites with decreasing current approximately obeys a power law and that there exists a critical value of the electric current, different for the different types of control, below which only one crystallite forms and grows on the cathode.     

Special features of mechanisms of formation of transverse nanosecond discharge with slot cathode, confined by dielectric walls

Experiments are performed and comparison is made of the electrical and optical characteristics of open and confined transverse nanosecond discharges with a slot cathode. It is found that the duration and shape of current pulse under conditions of open and confined discharges are significantly different and, under some conditions, the current density of confined discharge exceeds that of open discharge by more than an order of magnitude. Estimates are obtained of the coefficient of electron emission from cathode plasma, which significantly exceed the coefficient of electron emission in an abnormal discharge. It is demonstrated that the beam mode of primary electrons in the cathode layer during motion in the anode direction gradually transforms to hydrodynamic mode. The free paths of accelerated electrons in plasma are determined, and it is demonstrated that they reach the anode and have a significant impact on the dynamics of development and on the structure of optical radiation of transverse nanosecond discharge with a slot cathode.     

Numerical study of the two-dimensional flow of a binary mixture with a vapor-ice phase transition at the channel wall

An analysis is made of the problem of the desublimation of vapor from a laminar stream of a vapor-air mixture in a plane channel with allowance for the changes in the boundary conditions connected with the buildup of a layer of ice.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 35, No. 2, pp. 297–302, August, 1978.     

Electrolysis method of intercalation of layered transition metal dichalcogenides

A new method of intercalating organic Lewis bases, alkali hydroxides, Cu and Ag metals in to Group V layered dichalcogenide single crystals at room temperature is reported. It involves electrolytic reduction, in a suitable electrolysis cell, using the dichalcogenide as cathode and generation of the fresh intercalate species at the cathode surface. The organic intercalated complexes exhibit superconductivity like the parent dichalcogenides below 4.2°K.     

Investigation of thermal noise in a dynamic thermovacuum method for measuring moisture content of loose materials

The effect of thermal noise due to adiabatic expansion of a vapor-air mixture in the chamber of a primary transducer is considered and methods to decrease this destabilizing factor are proposed. Based on an analysis of thermal processes in the sample-vessel-medium system a mathematical heat and mass-transfer model for a dynamic thermovacuum method for measuring the moisture content is proposed. G. V. Plekhanov St. Petersburg State Mining-Engineering Institute (Technical University), St. Petersburg, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 1, pp. 734–738,     

Sorbents for treatment of water vapor-air flows to remove volatile organic compounds of radioactive iodine

Sorption of CH₃ ¹³¹I from water vapor-air medium on Fizkhimin and Siloksid inorganic sorbents and on SKT-3I activated carbon was studied. The sorption power of Fizkhimin, Siloksid, and SKT-3I sorbents toward CH₃ ¹³¹I was examined (1) after their 20-h contract with water, followed by removal of the liquid phase and drying at 110°C; (2) after 4-h treatment with steam (95–98°C), followed by drying at 25°C; (3) after keeping for 9 months in 100% humid air at ambient temperature of 10 to 45°C; and (4) after treatment with a water vapor-air flow (95–98°C, 60–80 vol % water vapor) for 2 h. In most cases, Fizkhimin sorbent and SKT-3I activated carbon preserve high sorption efficiency toward CH₃ ¹³¹I from water vapor-air flow.     

Breakdown in planar magnetron discharges of argon on copper

In magnetrons the magnetic field confines partially the electron swarm in a trap near the cathode increasing sputtering yield and deposition rates. The magnetic field also decreases the ignition voltage even at relatively low pressures thus allowing sputtering at lower pressures. Under this conditions fewer collisions, less diffusion and less thermalization of the sputtered atoms occur during the transport to the substrates. Atoms arrive at substrates with larger energy and at higher rates.We present an experimental study of the magnetic field influence on the breakdown voltage in planar magnetron abnormal glow discharges for argon on copper. A magnetron cathode was constructed, with a finely tuneable magnetic configuration. The experimental curves of the breakdown voltage as a function of the discharge pressure at constant “confinement power” show minima similar to those occurring in Paschen's law. At lower pressures the breakdown voltage has a strong dependence on magnetic configuration and changes from 750 to 250 V can be found. At higher pressures the breakdown voltage is less sensitive to the magnetic field.Paschen's law could not be fitted to the experimental results and as alternative an empirical expression is proposed and its parameters discussed.The results can be understood by the increased length of the average electron path both in helical and cycloid type trajectories near the cathode and by the reduction of the electron drift towards the anode and the walls of the chamber. In the Townsend regime, before breakdown and fixed voltage the electron density near the cathode increases with the confinement power. This causes a higher flux and energy of the ions that strike on the cathode for the same applied voltage. The voltage needed to get the self-sustained discharge is strongly reduced.     

基于标准阴极特性的面齿轮阴极设计方法

目的 解决电解加工过程中,简单曲面阴极设计方法不能保证面齿轮加工精度的问题。方法 利用标准阴极进行正交试验,得出钢制面齿轮的最优电解工艺参数。利用该工艺参数对阴极重新设计,加工试件,根据试件的测量结果对原始阴极进行修形,得出最终阴极形状。结果 通过对正交试验数据进行处理,得出钢制面齿轮的最优电解工艺参数为K=20, U=10 V, v=0.6 mm/min;根据试件的误差测量结果,推导出最优修形数为0.4602。结论 此阴极设计方法所设计的阴极能保证面齿轮的加工精度,而且能够加工出IT7级精度制件,同时为复杂型面的高精度电解加工方案提供了一种可行的阴极设计方法。     

Laser Cladding of Layered Ti/Nb/Cu Cathode with Homogeneous Arc Ablation Behaviors

Arc ablation threatens the cathode operating time and restricts the development of high-power arc heaters. Surface modification is an effective strategy in improving cathode ablation resistance without reducing matrix conductivities. Herein, Nb layer and Ti layer are laser clad on Cu matrix to decrease the arc ablation of Cu cathode. The total thickness of laser-clad Nb/Ti layer reaches 1850 μm. The Nb layer restrains Cu from diluting into surface cladding and no detrimental Ti–Cu intermetallic is formed. The surface Ti content is as high as 98.34 at%, guaranteeing the arc discharge homogeneity. The arc ablation behaviors of Ti/Nb/Cu cathodes are investigated in air atmosphere. The layered cathode discharges and ablates homogeneously. The arc discharge center is shallow with no appearance of deep pits or craters. The maximum ablation depth (72.1 μm) after 30 s discharging is ≈33.4% lower than that of Cu cathode. Besides, the cathode ablation rate, 1.61 μg C⁻¹, is ≈27.5% lower than Cu cathode. The improved arc ablation resistance is interpreted in the protective effect of refractory TiO₂ layer formed during air arc discharging.     

Sorption of 131I2 and CH3 131I from Water Vapor-Air Phase on Polysorb-1

Sorption of ¹³¹I₂ and CH₃ ¹³¹I from water vapor-air phase on Polysorb-1 polymeric sorbent was studied. The efficiency of radioiodine sorption depends on the humidity and flow rate of the vapor-air stream, column temperature, and the amount of volatile radioiodine compounds. Polysorb-1 effectively removes molecular iodine at the relative humidity of up to 100% and the sorption temperature from 20 to 125°C. Under these conditions, more than 99.9% of ¹³¹I₂ is removed from a gas flow at the height of the sorbent bed of 22.0 cm and time of gas-sorbent contact of 3.4 s. Polysorb-1 does not sorb methyl iodide from a water vapor-gas flow.