环氧复合材料快脉冲真空闪络特性研究.doc

附件2
论文中英文摘要
作者姓名：陈玉
论文题目：环氧复合材料快脉冲真空闪络特性研究
作者简介：陈玉，男，1977年9月出生，2003年9月师从于西安交通大学成永红教授，于2008年12月获博士学位。

中 文 摘 要
在高功率脉冲技术领域，由于固体绝缘材料的沿面闪络电压远远低于同等绝缘距离的体击穿电压，脉冲功率装置的真空绝缘支撑部件由于沿面闪络引起的绝缘破坏最为常见，因此成为限制脉冲功率传输的一个重要难点。随着脉冲功率装置向更高功率、更高容量、更小型化方向的发展，对真空绝缘材料的沿面闪络特性提出了更高的要求。针对脉冲功率装置中真空绝缘支撑材料介电性能提高这一重要需求背景，从环氧复合材料的介电性能、尺寸影响、外施电场等微观、介观、宏观效应研究入手，以电荷的产生、输运、分布为主线，着重研究了环氧复合材料真空闪络规律和闪络机理，建立了可以更好表征环氧复合材料真空闪络特性的“深浅陷阱模型”和“多层结构深浅陷阱模型”，提出了基于场致电子发射效应的不同陡度下的闪络电压关系方程。主要成果如下：
本文从Al2O3·3H2O、Al2O3、BaTiO3、TiO2等不同填料的环氧复合材料介电性能的角度研究了真空快脉冲闪络机理，通过对不同电极材料的电子发射特性、填料对复合材料体系电荷注入影响以及填料介电性能对三结合点电场强度影响的研究，认识环氧复合材料在快脉冲作用下电荷产生的基本规律；通过对不同填料的环氧复合材料的二次电子发射系数、热刺激电流的研究，认识电荷输运的基本特性与快脉冲作用下的闪络特性之间的关系；通过对不同介电性能填料对闪络前后电荷分布规律影响的研究，分析表面电荷分布与环氧复合材料真空快脉冲闪络电压之间的关系，从电荷产生、输运、分布的角度，认识了环氧复合材料介电性能的对快脉冲作用下真空闪络特性的影响规律，进而提出了一种环氧复合材料真空快脉冲闪络的深浅陷阱模型，该模型给出了闪络起始、闪络发展、闪络贯穿等不同阶段复合体系中电荷的深陷阱和浅陷阱对闪络过程电荷产生、输运的作用，及对闪络的影响作用规律。
针对不同粒径微米复合材料及微纳米复合材料表现出来的不同闪络特性，本文从复合材料体系中填料介观尺寸影响的角度研究了其对环氧复合材料闪络特性的影响机制。首先分析了填料的介观界面结构的基本特征，以及偶联剂对界面的修饰作用，及其对闪络电压的影响规律；建立了复合材料体系中填料的空间分布的简立方计算模型，计算了环氧复合材料体系中微米或纳米粒子的界面体积分数、比表面积等粒子分布参数，发现了复合材料体系中的填料粒子尺度、填料体积分数等对界面结构、界面分布、界面体积分数的影响规律，以及填料粒子的尺寸影响对其界面表现出不同的陷阱能级分布的影响规律，结合填料粒子在添加到一定比例时发生的逾渗现象，发现了填料粒子的尺寸影响与环氧复合材料闪络电压的内在联系。在此基础上，建立了Al2O3·3H2O复合材料深浅陷阱分布随填料比例变化的模型，在上一章深浅陷阱模型的基础上，进一步考虑了填料粒子的尺寸影响及其对电荷产生、输运、分布的影响，能够更好地解释环氧复合材料闪络特性曲线的变化规律。
针对试验中发现的不同快脉冲上升沿的陡度对闪络电压的影响，发现一般意义上的数学方程因难以清晰表达闪络的物理本质过程，本文从电荷产生与输运的角度入手，研究电子发射过程在闪络过程中的作用，讨论进行闪络时延、闪络电压、脉冲陡度之间的关系，建立了一种基于肖特基效应和场致发射效应的脉冲陡度与闪络电压关系的拟合公式，可以从闪络的物理本质角度反映外施电压对电荷的驱动及对闪络发生发展过程影响。
关键词：环氧复合材料；快脉冲；真空闪络；深浅陷阱；尺寸影响；多层模型；脉冲陡度；闪络电压；电子发射效应

Study on Pulsed Flashover characteristic of Epoxy Composites in Vacuum
Chen Yu
ABSTRACT
In the field of high power pulse technique, surface flashover typically takes place on the surface region of solid insulating materials at applied electric stress much lower than the bulk breakdown strength of the material. Due to the requirement of higher power, higher capacity and miniaturization for the pulse power devices in future, surface flashover in vacuum insulation material becomes an important problem in the development of pulse power technology. Therefore, the vacuum insulation material needs to be improved for the pulse power equipment, and the effects of dielectric property, filler scale and applied electric field on the flashover characteristic of epoxy composites need to be investigated. From different microscopic and macroscopic views, the behaviors of charge injection, transportaion and distribution of epoxy-based material for pulsed flashover were investigated. The deep and shallow trap model based on the multi-layer structure of interface was proposed to explain the vacuum flashover properties of epoxy-based material. The formula describing the relationship between flashover voltage and pulse steepess base on the electron emission effect was also proposed. The main results are shown as follow:

Different flashover characteristics of epoxy composite filled different micro fillers, such as Al2O3·3H2O, Al2O3, BaTiO3 and TiO2 micro particles, are studied, and the flashover mechanism was investigated. Considering to the electron emission process of electrode material, the influence of filler type on the charge injection and the influence of fillers’ dielectric property on the triple-joint electrical field, the rule of charge generation was understood. Charge transportation process was studied by the measurements of secondary electron emission coefficients and thermal stimulated depolarization current. The surface charge distribution on different materials after flashover was measured, and the influence on the flashover voltage due to surface charge distribution was analyzed. Furthermore, a deep and shallow trap model was proposed, which was able to explain the charge generation and transportation process during the different stages of flashover.

The microcomposites, nanocomposites and nano-mico-composites loaded with the filler of Al2O3·3H2O particles show different flashover performance, and the effect of filler size on the flashover performance of epoxy-based material was discussed based on the size influnence. Firstly, the typical interface structure was described, and the coupling agent effect was emphasized. Secondly, the parameters of interface volume proportion and specific surface area were calculated based on the simplified cubic model. The influence of filler size and content on the interface structure, interface layer distribution and interface volume proportion was discussed. The distribution of trap energy level in the interface of particles was analyzed. The relationship between particle size influnence and flashover voltage was analyzed. At last, the deep and shallow trap model based on the multi-layer model is proposed. Considering the size influnence of fillers, the flashover characteristic was able to be explained.

Considering the effect of different pulse steepness, the flashover characteristic of pure epoxy under different pulse steepness is investigated. The relationship of flashover voltage and pulse steepness could hardly to explain the physical process based on the simple math fitting equation. When the electron emission process, charge generation and charge transportation were considered, the flashover time delay, flashover voltage and pulse steepness were discussed, and then a new fitting formula based on the electron emission equation was proposed to describe the relationship between the pulse steepnees and flashover voltage. The formula was able to reflect the change with the applied voltage and the real physical process. Finally, the flashover voltage can be evaluated approximately.
Key words: Epoxy composite material; Fast pulse; Vacuum flashover; Deep and shallow trap; Size influnence; Multi-layer model; Pulse steepness; Flashover voltage; Electron emission effect