Direct current(DC)surface flashover characteristics of modification technology on polyimide(PI)in vacuum are investigated accompanied with the theoretical analysis. Two kinds of semi-conductive powders(nano scale and micro scale)are chosen as the modifier of raw PI
and the experiments for DC surface flashover characteristics of PI material in vacuum(10
-3
Pa)are carried out. Meanwhile
the surface flashover mechanism under DC voltage in high vacuum is analyzed following the test results of secondary electron emission(SEE)coefficient and the observed surfaces state of flashover experimented samples by scanning electron microscopy(SEM). The experimental results show(1)In vacuum
DC surface flashover voltage of nano modified PI which used
nonlinear conductivity filler is higher than pure PI
while that of micro modified PI is lower than pure PI;(2)The surface SEE coefficient of nano modified is reduced and the roughness of surface is increased;(3)Gas overflow phenomenon appears in the moment of prebreakdown. In combination with the results of SEM and physical analysis
it is considered that the nano modified composite sample has a lower electron-stimulated desorption coefficient
thus leading to gas desorption
is the key factor affecting DC surface flashover voltage in vacuum.
WANG Kai, XIAO Fei, ZHAN Maosheng. Preparation and atomic oxygen resistance of polyimide/inorganic oxide composite films [J]. Journal of Beijing University of Aeronautics and Astronautics, 2012, 38(5): 601-604.
ZHA Junwei, DANG Zhimin. Insulation properties of polyimide/nano-ZnO hybrid films with good corona resistance [J]. Proceedings of the CSEE, 2009, 29(34): 122-127.
OKUMURA T, NITTA K, TAKAHASHI M. Flashover plasma characteristics on 5 m2 solar array panels in a simulated plasma environment of geostationary orbit and low earth orbit [C]∥48th AIAA Aerospace Sciences Meeting. Orlando, USA: AIAA, 2010:AIAA 2010-1602.
ANDERSON R A, BRAINARD J P. Mechanism of pulsed surface flashover involving electron-stimulated desorption [J]. J Appl Phys, 1980, 51(3): 1414-1421.
PANITZ J A. Preflashover phenomena and electron-stimulated desorption in high electric fields [J]. J Appl Phys, 1974, 45(3): 1112-1114.
GRAY E W. Vacuum surface flashover: a high-pressure phenomenon [J]. J Appl Phys, 1985, 58(1): 132-141.
NEUBER A A, BUTCHER M, KROMPHOLZ H, et al. The role of outgassing in surface flashover under vacuum [J]. IEEE Transactions on Plasma Science, 2000, 28(5): 1593-1598.
BLAISE G, LEGRESSUS C. Charging and flashover induced by surface polarization relaxation process [J]. J Appl Phys, 1991, 69(9): 6334-6339.
BLAISE G. New approach to flashover in dielectrics based on a polarization energy relaxation mechanism [J]. IEEE Transactions on Electrical Insulation, 1993, 28(4): 437-443.
REN Chengyan, YUAN Weiqun, ZHANG Dongdong, et al. New development of microstack insulator technology [J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2011, 18(4): 1017-1021.
CHEN Yu, CHENG Yonghong, ZHOU Jiabin, et al. Surface charging and flashover of solid cross linked polystyrene excited by nanosecond pulse in vacuum [C]∥International Symposium on Electrical Insulating Materials. Piscataway, NJ, USA: IEEE, 2008: 420-423.
严璋, 朱德恒. 高电压绝缘技术 [M]. 北京: 中国电力出版社, 2007: 48-62.
SUHARYANTO, MICHIZONO S, YAMANO Y, et al. Secondary electron emission of dielectric materials under high temperature condition [C]∥International Symposium on Discharges and Electrical Insulation in Vacuum. Piscataway, NJ, USA: IEEE, 2004: 21-24.
金维芳. 电介质物理学 [M]. 北京: 机械工业出版社, 2006: 126-140.
MILLER H C, NEY R J. Gases released by surface flashover of insulators [J]. J Appl Phys, 1988, 63(3): 668-673.
PILLAI A S, HACKAM R. Surface flashover of solid dielectric in vacuum [J]. J Appl Phys, 1982, 53(4): 2983-2987.
ZHANG Tong, MAO Fuming. Theoretical study of low energy electrons induced desorption [J]. Journal of Electron Devices, 2000, 23(1): 60-66.
KIM E K, KIM J H, NOH H K, et al. Electrical properties of ZnO nano-particles embedded in polyimide [J]. Journal of Electronic Materials, 2006, 35(4): 512-515.
ZHENG Xiaoquan, LI Shengtao, WU Jiang, et al. Modification technology on anti-deep-change of polymer dielectric for spacecraft [J]. Aerospace Materials Technology, 2009(5): 44-47.
林志东. 纳米材料基础与应用 [M]. 北京: 北京大学出版社, 2010: 17-47.
YAMAMOTO O, TAKUMA T, FUKUDA M, et al. Improving withstand voltage by roughening the surface of an insulating spacer used in vacuum [J]. IEEE Transactions on Dielectrics and Electrical Insulation, 2003, 10(4): 550-556.