Yang Xiong, Sun Guangyu, Guo Guangzhi, Zou Fangzheng, Li Wenrui, Lian Ruhui, Liu Haoyan, Wang Chao, Zhao Haoxiang, Li Wendong, Song Baipeng, Zhang Guanjun
State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland.
ACS Appl Mater Interfaces. 2023 Aug 30;15(34):40963-40974. doi: 10.1021/acsami.3c07998. Epub 2023 Aug 20.
High-voltage and high-power devices are indispensable in spacecraft for outer space explorations, whose operations require aerospace materials with adequate vacuum surface insulation performance. Despite persistent attempts to fabricate such materials, current efforts are restricted to trial-and-error methods and a universal design guideline is missing. The present work proposes to improve the vacuum surface insulation by tailoring the surface trap state density and energy level of the metal oxides with varied bandgaps, using coating on a polyimide (PI) substrate, aiming for a more systematical workflow for the insulation material design. First-principle calculations and trap diagnostics are employed to evaluate the material properties and reveal the interplay between trap states and the flashover threshold, supported by dedicated analyses of the flashover voltage, secondary electron emission (SEE) from insulators, and surface charging behaviors. Experimental results suggest that the coated PI (i.e., CuO@PI, SrO@PI, MgO@PI, and AlO@PI) can effectively increase the trap density and alter the trap energy levels. Elevated trap density is demonstrated to always yield lower SEE. In addition, increasing shallow trap density accelerates surface charge dissipation, which is favorable for improving surface insulation. CuO@PI exhibits the most remarkable increase in shallow trap density, and accordingly, the highest flashover voltage is 42.5% higher than that of pristine PI. This study reveals the critical role played by surface trap states in flashover mitigation and offers a novel strategy to optimize the surface insulation of materials.
高压和高功率器件在用于外层空间探索的航天器中不可或缺，其运行需要具有足够真空表面绝缘性能的航空航天材料。尽管人们不断尝试制造此类材料，但目前的努力仅限于试错法，且缺少通用的设计指南。本研究提出通过在聚酰亚胺（PI）基板上进行涂层，调整具有不同带隙的金属氧化物的表面陷阱态密度和能级，来改善真空表面绝缘性能，旨在为绝缘材料设计提供更系统的工作流程。采用第一性原理计算和陷阱诊断来评估材料性能，并揭示陷阱态与闪络阈值之间的相互作用，同时对闪络电压、绝缘体的二次电子发射（SEE）和表面充电行为进行专门分析。实验结果表明，涂覆后的PI（即CuO@PI、SrO@PI、MgO@PI和AlO@PI）能够有效提高陷阱密度并改变陷阱能级。较高的陷阱密度总是会导致较低的二次电子发射。此外，增加浅陷阱密度可加速表面电荷耗散，这有利于改善表面绝缘性能。CuO@PI的浅陷阱密度增加最为显著，因此，其最高闪络电压比原始PI高42.5%。本研究揭示了表面陷阱态在减轻闪络方面所起的关键作用，并提供了一种优化材料表面绝缘性能的新策略。
