大气条件下的沿面闪络等离子体演化过程研究

电子器件在大气环境下发生沿面闪络导致工作失效是限制其性能的瓶颈问题之一。本文基于高速相机诊断得到了大气条件下陶瓷沿面闪络发展过程,并与真空沿面闪络过程进行了比较。然后基于二维网格粒子法耦合直接模拟蒙特卡罗法(PIC-DSMC)建立了相应的仿真模型,得到了大气条件下陶瓷沿面闪络过程中电子和离子数密度分布演化特性,分析了大气条件下沿面闪络过程中等离子体通道的形成与竞争特性,并与实验结果进行了验证,阐明了大气条件下沿面闪络过程的物理机制,为进一步深入理解沿面闪络问题提供了支撑。     

大气条件下的沿面闪络等离子体演化过程研究北大核心CSCD

电子器件在大气环境下发生沿面闪络导致工作失效是限制其性能的瓶颈问题之一。本文基于高速相机诊断得到了大气条件下陶瓷沿面闪络发展过程,并与真空沿面闪络过程进行了比较。然后基于二维网格粒子法耦合直接模拟蒙特卡罗法(PIC-DSMC)建立了相应的仿真模型,得到了大气条件下陶瓷沿面闪络过程中电子和离子数密度分布演化特性,分析了大气条件下沿面闪络过程中等离子体通道的形成与竞争特性,并与实验结果进行了验证,阐明了大气条件下沿面闪络过程的物理机制,为进一步深入理解沿面闪络问题提供了支撑。     

液氮中聚四氟乙烯冲击沿面闪络的极性效应

为了探究液氮浸渍下的沿面放电问题,对聚四氟乙烯在液氮环境中极不均匀电场下的沿面闪络电压进行了测量。结果表明其极性效应表现出正极性脉冲下的沿面闪络电压普遍高于负极性时的规律。通过对闪络痕迹的分析,结合电场分布仿真和液氮中沿面闪络机理的理论研究,提出液氮环境中沿面闪络极性效应的表现与变压器油相反的原因是液氮介质极易气化,在闪络过程中气化层的形成较容易,而液氮介质相对于气化层内的氮气产生空间电离的程度要小得多。     

CSNS/RCS二极陶瓷真空盒磁控溅射镀TiN薄膜研究进展

中国散裂中子源(CSNS)将在快循环同步加速器(RCS)的二极磁铁和四极磁铁内应用陶瓷真空盒。为降低陶瓷表面的二次电子发射系数(SEY),采用直流磁控溅射的方法,对二极陶瓷真空盒内壁镀氮化钛(TiN)薄膜工艺进行实验研究。结果表明:薄膜附着力较好,镀TiN膜后陶瓷表面SEY峰值由4.2降到2.3,但薄膜Ti/N比例及膜厚均匀性还有待进一步改善。     

电极锥角对真空沿面放电等离子体生成特性的影响

本实验采用持续时间为微秒级、放电电流为100 A～300 A的单脉冲电源形式,设计了三种不同锥角的铝电极.通过朗缪尔探针法测量放电生成的等离子体相关参数,讨论了电极锥角对真空沿面放电等离子体生成特性的影响.由于爬距相同时沿面放电的路径具有不确定性,导致探针法无法准确测得等离子体参数.本实验采用OPT101光电转化芯片对真空沿面放电瞬间的电弧发光强度进行测量,并通过双缝法对放电路径进行了筛选,从而保证探针法测量数据的可靠性.实验结果表明,阴极锥角越小,阴极三结合点处电场强度越大,越容易发生沿面放电;阴极三结合点处电场强度越大、阴极三结合点的分布范围越大,沿面放电得到的主放电电流越大,最终测得的等离子体密度也越大.     

(Mg0.527 Al0.473)(Al1.758 Mg0.126)O4薄膜制备及其沿面耐压性能的研究

采用丝网印刷法在95％(质量比)Al2O3基板上制备MgO薄膜,在大气环境1650℃下烧结使MgO与Al203基板反应形成(Mg0.527Al0473)(Al1758Mg0.12)O4薄膜(MAO).通过X射线衍射仪、扫描电子显微镜、能谱仪、X射线光电子能谱仪和激光共聚焦显微镜分别对MAO薄膜的结构、微观形貌、成分和表...     

Relationship of porcelain insulator temperature and flashover voltage measurement procedure in vacuum

In this paper the existence of a connection between a conditioning procedure and the solid insulator temperature changes in a vacuum is shown. The increase of an insulator temperature and consolidation of the other working-temperature in the system insulator-electrodes, is a predominant feature for the high voltage measurements performed on dimensionally small insulators in a vacuum. It was found that numerous surface breakdowns influence the insulator surface strength due to its temperature changes.     

Flashover voltage of spacer insulators in a vacuum at 290-6 K

The dependence of insulator surface strength on temperature in the range of 290 - 6 K in a vacuum is presented. The insulator surface strength was found to increase in the range of liquid nitrogen and liquid helium temperatures compared with the flashover voltage measurements at ambient temperatures.Complex distributions of flashover voltage were obtained and were plotted on Weibull probability paper. The effect seems to be the result of the increase in insulator temperature near the triple junction.A suitable model of the correlation between the insulator flashover voltage and its temperature was proposed.     

Thermal conductivity of ceramic fibrous insulators at high temperatures

The temperature and bulk density dependence of the thermal conductivity of commercial aluminosilicate fibrous insulators were studied by using the transient hot wire method. The thermal conductivity of ceramic fibrous insulators in both air and helium gas atmosphere increased with increasing bulk density. At high temperatures, however, the insulators with lower bulk density showed a higher thermal conductivity because of heat radiation. The following experimental relation between thermal conductivity and temperature was obtained for aluminosilicate fibruous insulators: =a exp(b). Relationships are given between the constants a and b and the bulk density. From the relation, the optimum bulk density of ceramic fibrous insulators can be calculated for each working temperature.Paper presented at the Fourth Japan Symposium on Thermophysical Properties, October 20–22, 1983, Yokohama, Japan.     

Study of elastic waves of acoustic frequencies generated by surface partial discharges of solid insulators in vacuum

The paper presents studies on the electrical properties of cylindrical shape samples of insulators made from polyamide, epoxy resin, polymethyl methacrylate, and electrical porcelain, located in vacuum at a pressure of 0.1 mPa. The insulator samples had a diameter of 20 mm and a height of 1-10 mm. The study was performed with an alternating voltage of 50 Hz in the range up to 70 kV (peak). The examination has shown that partial discharges on the surface of the insulator generate elastic waves of acoustic frequency. The waves may be used to locate the position of the partial discharges by means of suitably sensitive equipment. During the measurements the following parameters of the acoustic signals have been recorded: the largest amplitude of signal, the number of signal amplitudes exceeding the discrimination level, the rate of signals, the number of events the envelopes of which exceed the discrimination level, the rate of events and the root mean square value of signal. It was found that for purposes of determining the voltage threshold necessary for occurrence of acoustic activity, a measurement of the largest amplitude of a given acoustic signal is the most appropriate. Nevertheless, for forecasting a flashover occurrence of examined insulators a measurement of the root mean square value of acoustic emission signal may be also effectively used. Values of both of these parameters significantly increased just before an instance of surface flashover.     

High voltage,helium flow cryostat for solid insulator surface strength investigations in a vacuum

A high voltage, helium flow cryostat comprising two metal cryogenic liquid containers and a glass vacuum chamber is presented. The simplicity of the cryostat's construction is convenient in that it can be used in different types of high voltage investigations in a vacuum, in the range from the liquid helium temperature to the room temperature.     

电子陶瓷用钛酸钡粉体制备工艺及其发展

对近年来国内外电子陶瓷用钛酸钡粉体制备工艺及发展进行了综述，指出了水热法由于其优良特性在近年来受到广泛关注，并预测用水热法和其它各种方法相结合的工艺必将在日后制备电子陶瓷用钛酸钡粉体工艺中占据重要地位。     

陶瓷膜表面粗糙度对含油废水过滤性能的影响

采用表面粗糙度仪、扫描电子显微镜(SEM)和三维非接触表面形貌仪(WLI)表征膜表面形貌,并考察了陶瓷膜表面粗糙度对过滤含油废水性能的影响.结果显示,具有不同表面粗糙度的相同孔径陶瓷膜,其纯水通量基本相同;粗糙度越大的膜,过滤含油废水的膜通量衰减越快,稳定通量也越低;陶瓷膜表面粗糙度对油截留率基本没有影响;废水中油滴粒...     

预处理剂对陶瓷膜表面性质及渗透通量的影响

考察了不同预处理剂对陶瓷膜表面性质及渗透通量的影响,结果表明:表面活性剂的加入,使陶瓷膜表面的负电性以及亲水性得到提高,膜渗透通量从100L/(m2·h)提高到200L/(m2·h);碱式氯化铝中Al3+在膜表面的吸附,导致膜表面呈现正电位,相应的膜渗透通量只有50L/(m2·h);吸附剂对渗透通量的影响主要体现其在乳化废水中表面电位的不同,呈负电性的二氧化硅有利于渗透通量的提高,而呈正电性的氧化铝会导致膜通量的下降.     

高纯氧化铝陶瓷材料真空出气性能测试

通过一系列实验测试了致密型高纯氧化铝陶瓷(99瓷)的出气速率．考察了材质、不同预处理方法等因素对其出气性能的影响，并分析了不同温度下出气的主要成分及分压强。     

表面粗糙度对PS-PVD YSZ陶瓷层性能的影响EI北大核心CSCD

采用PS-PVD工艺在预制有NiCoCrAlYTa黏结层的K417G高温合金上制备YSZ陶瓷层;采用万能拉伸试验机、粒子冲刷仪、静态氧化炉等设备测试PS-PVD YSZ陶瓷涂层的结合强度、抗粒子冲刷和抗高温氧化性能;采用SEM和EDS分析涂层表面、截面形貌和元素分布等。结果表明:表面粗糙度对YSZ陶瓷层拉伸结合强度、抗粒子冲刷和抗高温氧化性能的影响很大。随着粗糙度的增大,结合强度先增大而后减小。Ra=0.40μm表面上沉积的YSZ涂层,其结合强度最高,达到23.5 MPa。拉伸断裂发生在涂层内部,并距离黏结层40~70μm的位置。随着表面粗糙度的增大,冲刷速率先减小而后增大,Ra=0.40μm涂层的抗粒子冲刷性能最好,冲刷速率仅为2.8×10^-3 g/g,表面起伏小和孔隙率低是涂层具有良好抗粒子冲刷性能的重要原因。不同表面粗糙度制备的YSZ涂层均能生成致密连续的热生长氧化物(TGO)层。粗糙度大则生长的TGO起伏大,更容易导致局部增厚和应力集中而失效。