水中脉冲放电金属电极烧蚀机理

采用板-板电极, 在放电间隙距离为2 mm、放电电流峰值为22 kA条件下, 对黄铜、钨铜电极的烧蚀特性进行了对比研究。利用高精度天平测量放电过程中的电极质量损失, 分别获取了阴极、阳极及总的平均烧蚀速率。通过放电后电极表面微观形貌、微观元素组成的分析及液体中金属离子的含量分析, 对水中脉冲放电金属电极的烧蚀机理进行了探讨。结果表明, 水中脉冲放电时, 钨铜电极的抗烧蚀性能明显高于黄铜电极。黄铜电极的主要烧蚀是以中心的大量孔洞及其边缘的波纹结构为表现形式的液体金属的溅射;钨铜电极的突出物及较平整的表面暗示了气相侵蚀的作用。以电弧的焦耳热效应为催化剂, 钨铜与水的电化学反应更为强烈, 因此电化学腐蚀是水中放电电极烧蚀的形式之一。     

大脉冲电流下钨铜电极水和空气中的烧蚀特性

针对水中、空气中脉冲放电条件下金属电极烧蚀速率及烧蚀机理差异,对脉冲大电流作用下水中、空气中钨铜电极的烧蚀特性进行了对比研究。在保证放电电流波形一致性的前提下,通过采用高精度天平测量并获取了水中、空气中钨铜电极的阴、阳极烧蚀速率及总烧蚀速率,并对电极表面进行了二次电子观察和背散射电子观察分析。结果表明,大脉冲电流作用下,水中钨铜电极烧蚀较空气中更为严重,钨铜电极的烧蚀主要是金属蒸发引起的汽相侵蚀。由于水介质较空气具有不可压缩性,水中放电电弧集中,电极表面电弧斑点处电流密度和电流作用时间较空气中更为严重,同时由于水中脉冲放电时发生的高温物理化学反应,是造成水中电极烧蚀要高于空气中的根本原因。     

LTD模块气体开关电极材料烧蚀性能实验

针对直线变压器驱动源(LTD)对开关的长寿命需求,基于前期研制的200kV低抖动多间隙气体开关电极几何参数以及开关通流水平,详细开展了不同电极材料(钼、黄铜、铜钨合金、高密度石墨、304和321不锈钢)的烧蚀性能实验。实验结果表明,在单次电荷转移量15.4mC,脉冲电流20kA条件下,体积烧蚀速率从大到小依次为:石墨、黄铜、铜钨合金、钼、不锈钢。电极烧蚀微观形貌分析表明,不锈钢是用于LTD开关相对较好的电极材料。根据不锈钢电极的体积烧蚀速率,可知理论上LTD开关的运行寿命可以超过1×106次,但前提是开关外壳需保持足够的绝缘强度。     

气体火花开关电极烧蚀研究综述

气体火花开关是脉冲功率装置中最常用的关键器件。电极烧蚀作为脉冲功率开关中的难点问题，会引起开关自击穿电压降低、触发抖动增大及开关寿命降低，已成为制约气体开关发展和应用的一个瓶颈。本文回顾梳理了国内外学者针对电极烧蚀问题进行的一系列研究，从电极烧蚀理论和实验研究成果两个方面，介绍了电极烧蚀的基本机制及仿真模型，归纳了影响开关电极烧蚀的因素以及电极耐烧蚀材料的研究进展，最后讨论了电极烧蚀研究面临的问题以及优化电极材料抗烧蚀性能的方向。     

±100 kV三电极场畸变气体火花开关

设计了一种用于直线变压器驱动源的三电极场畸变气体火花开关。开关采用SF6气体绝缘,开关尺寸和电感较小,实测开关电感约为67 nH。在工作电压80 kV、工作系数为70%时,开关触发时延为40.0 ns,抖动约2.8 ns。对比研究了钨铜合金和黄铜两种电极材料对开关静态和触发击穿特性的影响,研究结果表明:铜钨合金电极开关的自击穿电压分散性、触发时延及抖动、自放电概率和电极表面烧蚀均小于黄铜电极,更适宜作为三电极场畸变开关的电极材料。     

电极材料对气体火花开关静态性能的影响北大核心CSCD

在工作气压和火花间隙固定的条件下,针对稍不均匀场的圆饼形电极开关开展了不同电极材料下开关自击穿实验,开关间隙距离为5mm,工作气压为0.25 MPa,击穿电压平均值为40kV。分别选取了不锈钢、黄铜、钨铜合金和石墨材料作为实验对象,对比了不同电极材料下电极质量损失、电极表面形貌和开关静态特性的差异。实验结果表明,石墨电极质量损失速率略高于金属电极,但是由于石墨电极烧蚀产物多为气体,因此石墨电极绝缘子污染程度远小于金属电极。石墨电极开关在低欠压比下自击穿概率也远小于金属电极开关。三种金属电极开关,其静态特性差异不大,但钨铜电极烧蚀程度显著低于不锈钢和黄铜电极开关。     

高功率气体火花开关电极烧蚀机理

气体火花开关以其工作电压高、功率容量大、结构简单等优点，在脉冲功率技术中得到了广泛的应用。但这种开关工作在高功率重复频率状态时，由于电极的很快烧蚀，影响了开关性能，限制了其寿命。因此，抑制电极烧蚀、寻找耐烧蚀的电极材料是提高高功率重复频率气体开关工作寿命的关键，也是本文研究的内容。     

大电流两电极气体开关研究

 由于引燃管难以满足现在能源系统对放电开关承受大电流的要求，因此研制了大电荷转移量两电极气体开关。这种新型气体开关电极间距可调，无触发极，采用同轴结构，并将主电极置于金属腔体内，减少了放电对绝缘支撑的污染。主电极为铜钨合金材料，设计为平顶圆柱状，以提高烧蚀均匀度和热传导效率，减少电极材料喷溅，延长其寿命。绝缘支撑采用碗状结构，提高了机械强度，增加了沿面击穿距离。该开关工作电压达25 kV，放电电流超过100 kA（脉冲宽度600 μs），单次脉冲电荷转移量达50 C。实验结果显示该气体开关触发性能稳定，电极表面烧蚀均匀，多次大电流实验后电极表面保持完好，可应用于强激光能源系统。     

高气压大电流放电条件下的电极烧蚀

归纳了影响开关电极烧蚀量的因素,包括开关电极材料、放电条件等,分析了开关电极烧蚀特征与烧蚀后表面形貌,总结了开关电极烧蚀的主要机制电极加热和电极材料去除机制。为了延长开关工作寿命,提出了减少开关电极烧蚀的措施,包括选用抗烧蚀性能优异的材料作为开关电极材料、采用合适的开关电极结构和优化的放电条件等。     

气体火花开关电极烧蚀研究

采用Mo,WCu和W分别作为三种气体火花开关的主电极材料,进行放电条件下电极烧蚀实验,研究开关电极烧蚀率和烧蚀形貌,分析电极烧蚀特征。结果表明,Mo,WCu和W开关的主电极烧蚀率分别为3.32×10-2 C-1·m-2,2.63×10-2 C-1·m-2和1.74×10-2 C-1·m-2,W开关主电极烧蚀率最小。实验后开关的主电极中心烧蚀严重,呈现明显裂纹和烧蚀坑。Mo主电极表面呈现明显熔融态,阴极表面形成大量裂纹(宽度达10μm)和孔隙(孔径达10μm);WCu和W主电极表面形成少量圆球状W突起(粒径达20μm及以上)。开关外壳内壁沉积了喷溅颗粒。WCu开关外壳沉积颗粒较大(粒径达10μm),Mo开关外壳沉积颗粒居中(粒径为2μm),W开关外壳沉积颗粒最小(近1μm)。因此可优先选用具有优异抗烧蚀性能的W作为气体火花开关电极材料。     

FLTD三电极场畸变气体开关寿命特性

针对设计的一种场畸变气体开关,研究中间电极材料分别为不锈钢和黄铜条件下的烧蚀特性,结合开关寿命期间静态与触发特性的变化规律,获得决定开关寿命的关键因素,为三电极场畸变气体开关的性能优化提供理论支撑。研究结果表明,采用不锈钢和黄铜作为中间电极的烧蚀区域以及表面粗糙度均随着放电次数增加而增大,黄铜电极烧蚀较为严重且表面有明显的烧蚀圆斑,不锈钢电极则具有更高的表面粗糙度,阴阳极表面烧蚀存在明显差异,随着放电次数的增加,击穿点向电极边缘区域集中,影响开关的沿面绝缘特性,是导致开关寿命终结的主要原因。     

Surface modification of platinum by laser-produced X-rays

Laser-induced plasma is used as an X-ray source for the growth of hillocks like nanostructures on platinum surface. To generate X-rays, plasma is produced by Nd:YAG laser, which is operated at second harmonics (λ?=?532?nm, E?=?400?mJ). Analytical grade 5?N pure Al, Cu and W are used as laser targets for X-rays production. X-rays produced from Al, Cu and W plasmas are used to irradiate three analytical grade (5?N pure) platinum substrates, respectively, under the vacuum ～10^?4 torr. XRD analysis shows considerable structural changes in the exposed platinum. The decrement in reflection intensities, increment in dislocation line density, change in d-spacing and disturbance in the periodicity of planes evidently prove these structural changes. Atomic force microscope AFM topographic analysis of the platinum exposed to X-rays emitted from Al, Cu and W targets showed that nanometer-size hillocks are produced on the platinum surface irrespective of the source. It has also been observed that due to these hillocks, the roughness of the surface has increased. Conductivity of hillocks produced from X-rays produced by Al, Cu and W targets is compared and it is shown that the hillocks produced by Al target X-rays have better conductivity compared to the hillocks produced by X-rays from Cu and W targets.     

System-independent release adiabats from shocked states1

Suitable combinations of three parameters of any “linear” material: the initial density, and the coefficients of the linear relationship between shock and particle velocities, are used to define in reduced form most of the variables involved in shock pressures thermodynamic phenomena. This reduced variables formalism is applied, in conjunction with the mirror-image approximation, to obtain pressure-volume relationships for the release adiabats from any given shocked state. The resulting equations are system-independent, that is, they contain only pure numbers and reduced variables. Each adiabat is characterized by the coordinates of the point of crossing with the Hugoniot. Some of the adiabats so obtained for Al, Cu, W, Ti and Cr are in good agreement, at least down to pressures about one half that of the initial shocked state, with those computed using other procedures. A table of adiabats, valid for all “linear” materials, is also included.     

Generation and Measurements of Ion Species from Vacuum Arcs

We have measured the ion flux for different electrode materials in a vacuum arc. The vacuum arc has a point-plane geometry. The ion species in the generated plasma are identified using a time-of-flight (TOF) spectrometer. Ion species that have been generated to date include D+, Mg+, Mg++, Al+, Al++, Al+++, Ti+, Ti++, Ni+, Ni++, Cu+, Cu++, Zn+, Zn++, and In+. We found that in all cases, the ion flux measured is directly proportional to the interelectrode gap spacing and to the arc current. Typical current densities measured were ~300 mA · cm-2 at a distance of 10 cm from the gap for 150-?s pulse. The study will be used for the development of a multiple-arc array source for application to intense ion beam generation.     

��һ�ڲ���W/Cu����������Ʊ��о���״

介绍了目前解决W/Cu连接界面缓解热应力的方法——添加适配层。在对不同适配层进行分析后,选出最佳W/Cu适配层,再对W/Cu适配层进行结构优化分析,得出选用W/Cu功能梯度材料作为适配层具有足够的结合强度,而且良好的导热性能能有效地缓解热应力。此外,重点阐述了目前成功的制备的W/Cu功能梯度材料用作W/Cu第一壁材料的适配层的常用方法。最后,对W/Cu功能梯度材料用作适配层解决W/Cu第一壁材料连接界面的问题做出了总结和展望。     

Anode erosion during pulsed arcing

An experimental study of the anode erosion rates of Cu, Zr, Ti, Mo, Ta, and W is presented under conditions similar to those used for electrodischarge coating. The arcs are conducted between a small anode and a larger cathode in air with pressures ranging from 10^-4 to 10³ torr. Unipolar arc pulses of 200-400-A peak current and 0.1-ms duration are produced at a 100-Hz pulse repetition rate by an RC circuit. For most materials, the electrode mass loss is primarily from the anode, and the mass loss is independent of pressure for pressures less than 0.1 torr, decreases steeply with increasing pressures in the range 0.1 to 10 torr, and decreases more gradually with increasing pressure above 10 torr. The experimental results are explained by using a limiting case of the integral conservation laws. In the low-pressure region the input energy is expended mainly in the acceleration of the metal vapor, and thus the erosion rate is independent of pressure. In the intermediate-pressure region the metal vapor jet is braked by its interaction with the surrounding gas. In the high-pressure region the vapor jet is completely halted, and vapor transport takes place only by diffusion through the surrounding gas     

Lifetime and erosion of silver-based wire electrodes in an ultracorona in air

Anode erosion rates and lifetime-limiting parameters for a range of different silver-based wire materials have been investigated in a positive corona in atmospheric pressure air. The electrode wear was determined by measuring electrical resistance and diameter of the corona wires. Among the test materials were AgMn and AgCu alloys and Ag-coated stainless steel. As a rule, the erosion rate of AgCu and AgMn alloy anode wires decreases with the logarithm of the total amount of the transferred charge. It is likely that the anode lifetime of AgCu alloys with the content of Ag below the eutectic point are limited by initiation of the streamer mode with extremely ozone production.