Use of boundary element method for the determination of tool shape in electrochemical machining

The problem of cathode shape determination for a given anode shape in electrochemical machining is considered. An algorithm based on the boundary integral equation technique and non-linear optimization for this inverse problem is developed. The additional flux condition at the anode is used as the constraint in this ill-posed problem. Through an iterative process, the shape of the cathode is determined by minimizing a functional. The algorithm is tested on two examples. It is shown that the algorithm is consistently superior compared to published numerical techniques based on the embedding method or the method of the lines.     

Two-Dimensional Model of Plasma Cathode with an Open Plasma Boundary

The paper deals with the solution of two problems for which a two-dimensional distribution is found of the current density and of the electric field in the hollow-cathode plasma. In the first one of these problems, the anode surface of the cavity represents two concentric flat anodes separated by an insulator. This system is used to study the problem of switching the current over from the external to internal anode, with the anode drop being a nonlinear function of current density. The distribution of the current density and of the anode voltage drop on the surfaces of both anodes is calculated for different potentials of the external and internal anodes. In the second problem, the function of internal anode is served by the open boundary of plasma with zero anode drop. The shape of the plasma boundary is determined depending on the plasma cathode geometry and parameters. The singularities are discussed that characterize the extraction of current from the open plasma boundary for different forms of electric discharges.     

Operating characteristics of the hollow anode glow discharge ion source

In this work, a new shape of a glow discharge ion source with axial extraction has been designed and constructed. High output ion beam current can be extracted axially in a direction normal to the discharge region without using extraction system. Optimization of the distance between the anode and the cathode has been determined using argon gas. It is found that the optimum gap distance between the anode and the cathode is equal to 3.5 mm, where stable discharge current and maximum output ion beam current can be obtained. The discharge characteristics of the ion source at different operating gas pressures have been measured at this optimum distance between the anode and the cathode. A disk of Teflon insulator has been put between the anode and the cathode. This disk was covering the cathode area and reducing the discharge area on the cathode surface for discharge confinement, therefore, a higher output ion beam current could be obtained.     

圆锥形阴极真空微三极管的计算机模拟

利用有限元法对圆锥形场致发射阴极的真空微三极管进行了计算机模拟。改变真空微三极管的各项结构参数及阳极和栅极电压 ,得到一系列模拟数据。然后对模拟结果进行分析讨论 ,总结出圆锥形阴极有效发射、阳极电流与真空微三极管的结构尺寸、阳极电压和栅极电压之间的关系 ,对于真空微三极管的实际设计和制作有一定的参考价值     

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.     

An alternative approach to shape design sensitivity analysis

A novel method is presented in this paper for calculating shape design sensitivity, which is based on the finite difference method (FDM). By analysing the numerical procedure of the FDM, the perturbation of the geometry is replaced by a perturbation load which can be calculated once the stress field of the initial problem and the design boundary perturbation are known. The final shape design sensitivity is obtained by solving the perturbation problem which has the same geometry and the kinematical boundary condition as the initial problem, but under the perturbation loads. Therefore the new method does not require the calculation of the matrices of the perturbed structure, and is independent of the perturbation step. A numerical implementation of the finite difference load method (FDLM) is described in which the boundary element method is used to evaluate the structural response. The numerical examples demonstrate that this new method for shape design sensitivity analysis is very accurate.     

钛基二氧化铅作为阳极电解制备羟基氧化镍的研究

使用钛基二氧化铅作为阳极,不锈钢作为阴极进行了电解制备羟基氧化镍(NiOOH)的研究,并和以泡沫镍为阴阳极的体系在氧化机理,氧化效率,产品型貌等方面进行了比较,结果说明钛基二氧化铅作为阳极电解法制备羟基氧化镍是一种更为高效、绿色的制备方法.     

Etching‐Assisted Crumpled Graphene Wrapped Spiky Iron Oxide Particles for High‐Performance Li‐Ion Hybrid Supercapacitor

From graphene oxide wrapped iron oxide particles with etching/reduction process, high‐performance anode and cathode materials of lithium‐ion hybrid supercapacitors are obtained in the same process with different etching conditions, which consist of partially etched crumpled graphene (CG) wrapped spiky iron oxide particles (CG@SF) for a battery‐type anode, and fully etched CG for a capacitive‐type cathode. The CG is formed along the shape of spikily etched particles, resulting in high specific surface area and electrical conductivity, thus the CG‐based cathode exhibits remarkable capacitive performance of 210 F g^?1 and excellent rate capabilities. The CG@SF can also be ideal anode materials owing to spiky and porous morphology of the particles and tightly attached crumpled graphene onto the spiky particles, which provides structural stability and low contact resistance during repetitive lithiation/delithiation processes. The CG@SF anode shows a particularly high capacitive performance of 1420 mAh g^?1 after 270 cycles, continuously increases capacity beyond the 270th cycle, and also maintains a high capacity of 170 mAh g^?1 at extremely high speeds of 100 C. The full‐cell exhibits a higher energy density up to 121 Wh kg^?1 and maintains high energy density of 60.1 Wh kg^?1 at 18.0 kW kg^?1. This system could thus be a practical energy storage system to fill the gap between batteries and supercapacitors.     

Mathematical modeling of the electron beam formatting systems on the basis of field emission cathodes with various shapes

In the present paper we solve some problems of field emission cathodes mathematical modeling and the electron guns for vacuum electronics. The supposed shape of the field emission cathode was either “sphere-on-cone” or “sphere-on-spindle” (as a cathode) on the sphere substrate and the spherical segment (as an anode).     

Phenomenological features of diaphragm discharge

Flame formations of relatively little-studied diaphragm discharge in water at low energy of discharge (up to 10 J) are investigated. Its particular features show up in the fundamental difference in shape between the anode and cathode flames on both sides of the diaphragm, in the difference in variation of their shape and size with the variation of electrical conductivity of the medium, in polar development of flames from the diaphragm to their electrodes, in the possibility of existence of “half-breakdowns”, and in the difference between them depending on polarity, in a special form of cathode breakdown.     

The effect of axisymmetric two-dimensional magnetic field on the configuration of vacuum-arc plasma

An experimental investigation is made of the effect of axisymmetric two-dimensional magnetic field on the forming of plasma and on the configuration of cathode spots in a vacuum-arc discharge. It is demonstrated that a magnetic field with a transverse (relative to the discharge axis) component has a significant effect on the shape of plasma column and on the rate of expansion of the cathode spot region. In a magnetic field, arc plasma has the form of truncated cone expanding toward the anode. The cathode spots take up a part of the cathode area which decreases with increasing magnetic field. Arguments are given in support of the assumption that the arrangement of cathode spots and the form of arc plasma are defined by the minimum principle similar to the Steinbeck principle. In so doing, the displacement of spots is caused by their emergence in a new region corresponding to a lower arc voltage. Also discussed is the mechanism associated with retrograde motion of cathode spot in view of the effect of azimuthal magnetic field on the axial component of current and of the effect of axial magnetic field on the azimuthal component of current.     

等离子喷涂制造固体氧化物燃料电池三合一电极

采用大气等离子喷涂法在阳极支撑上制备了电解质与阴极.利用X射线衍射分析了阴极与阳极喷涂前后的成分和相结构,用扫描电镜观察了SOFC( solid oxide fuel cell)三合一电极的截面形貌以及阳极、电解质与阴极的表面形貌.结果表明:喷涂前后阴极的化学成份未发生改变,阴极为单斜相、钙钛矿型的(La0.8Sr0.2MnO3)LSM;阳极在喷涂前为Ni/YSZ(Y2O3稳定ZrO2),在喷涂后Ni被氧化成NiO.由阳极、电解质与阴极构成的三合一电极界面不明显,其中电解质致密,阳极与阴极有一定孔隙.     

Cathodic titania nanotube arrays as anode material for lithium-ion batteries

The titanium dioxide nanotube arrays (TNAs) have been synthesized at cathode and anode via standard electrochemical method for their subsequent use as anode material for lithium-ion batteries (LIBs). The TNAs fabricated at cathode have higher Ti³⁺ in comparison to TNAs at anode, which was confirmed using X-ray photoelectron spectroscopy and Raman spectrometry. Moreover, the lattice parameters of cathodic TNAs are estimated via Rietveld refinement of X-ray diffraction, which also conform to Ti³⁺ doping and insertion of protons (H⁺). The electrochemical impedance spectroscopy hints an increment in the electronic conductivity of TNAs fabricated at cathode. As a result, high reversible areal–specific capacity (~385.5 µAh cm^?2 at 100 µA cm^?2) with excellent rate capability is acquired by utilizing TNAs fabricated at cathode as anode material in LIBs.     

Spectral diagnostics of plasma discharge between a metal cathode and liquid anode

The results from studies of an electric discharge between a metal cathode and liquid anode at atmospheric pressure are presented. We investigate the discharge shape, the plasma emission spectrum, the electron concentration and temperature, and the molecule temperature; we analyze the continuous emission in the plasma spectrum and perform infrared thermography.     

The Disappearing Anode Myth

The goal of this paper was to simply demystify the disappearing anode problem. Three key concepts for anode control were presented. First, anode / cathode area ratio, second, magnetron ejection angle and, lastly, the concept of aspect ratio / acceptance angle were introduced. Examples of the application of these principles were demonstrated. Finally, tradeoffs associated with dual magnetron sputtering and DC pulsed deposition were discussed.     

An experimental study of the dynamics of formation of plasma in a vacuum-arc discharge

An experimental study is made of the dynamics of formation of plasma in a vacuum-arc discharge (VAD) at different currents and different transverse dimensions of CuCr50 electrodes. High-speed multipleframe photography is used to obtain the time dependence of the current channel diameter and determine the rate of plasma expansion. It is demonstrated that the rate of expansion under the experimental conditions is independent of the discharge current, as well as of the presence or absence of external axial magnetic field. Two modes are identified, which differ from one another by the rate of expansion. Experiments are performed with anodes and cathodes of different diameters in the range of currents from 2 to 15 kA. It is demonstrated that, with electrodes of different sizes, a discharge initiated at the cathode center expands with time to the size of the smaller electrode while retaining the cylindrical shape. The anode temperature is calculated for two modes in view of the variation of the source power and of the transverse dimension of the zone of heating. It is demonstrated that the anode spot in the mode of rapid expansion is formed under insignificant heating of the anode. In the case of slow expansion, a strong heating of the anode is possible, under which its intense evaporation occurs. The anode temperature is calculated in view of the evaporation losses for modes with different numbers of jumpers arising as a result of the breaking of vacuum switch contacts.     

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.     

Singularities of interaction between a cathode stream and anode vapors in a vacuum arc: Numerical simulation results

Numerical simulation is performed of the process of interaction of cathode and anode ions in a highcurrent vacuum arc with evaporating anode. The presence of the friction force between ion flows, as well as of the friction work, leads to heating and acceleration of slow anode ions and deceleration of fast cathode ions. The boundaries of stable passage of current are determined, associated with the presence of the limiting value of density of anode vapors     

常开型后栅极场致发射显示板工作特性的研究

常开型后栅极场致发射显示板是一种新型的场致发射器件.它直接利用阳极使阴极产生场致电子发射,而通过埋在阴极之下的栅极上施加负电压来阻止阴极产生场致电子发射来调制显示所需的图像.为了研究该场致发射显示板的阴极发射特性,本文采用有限元法对场致发射区域内的电场分布进行了模拟计算,用Fowler-Nordheim(F-N)公式计算了阴极表面的发射情况.并研究了阳极电压、阴极电压、阴调距、阴极宽度和阴极厚度等参数的改变对阴极发射特性和栅极调制能力的影响.计算结果显示阴极发射特性和栅极调制能力与上述电参数和结构参数关系密切,从而为优化设计这种显示器件提供了方向.     

Laser-Monitor-Assisted Investigation of the Regions of Closure of Current on the Electrodes of an Atmospheric-Pressure Low-Current Carbon Arc

The results are given of observations of regions of closure of current on the electrodes of an atmospheric-pressure low-current carbon arc, performed using a laser monitor immediately during the time of burning of the arc. It is found that the time of existence of a cathode crater on a graphite cathode is 0.2–0.3 s. An analysis of images of the region of closure of current on a pyrographite cathode reveals evidence of melting of pyrographite. A comparison of images of the region of closure of current on the electrodes of a carbon arc with the available literature data on the conditions of closure of current on the anode and cathode enables one to establish the origins of the various details of images of the region of closure of current on the cathode and anode of a low-current carbon arc. The results of this comparison further lead one to conclude that a low-current electric arc is an arc with liquid cathode and anode spots, and that the melting process is a stabilizing factor as regards the current density in those spots.