柔性PDMS基介电复合材料的电场及击穿损伤形貌演变规律研究

Evolution of Electric Field and Breakdown Damage Morphology for Flexible PDMS Based Dielectric Composites

与其它储能设备相比,由介电复合材料制得的介质电容器在快速充放电能力与高功率密度方面极具优势,如何提高介电复合材料能量密度与优化其击穿性能已成为当前研究热点之一。为进一步调控并兼顾介电常数与击穿性能,本工作基于DBM(Dielectric Breakdown Model,介电击穿模型),采用有限元数值模拟,研究了无机填料的分布对柔性聚二甲硅氧烷(PDMS)基介电复合材料体系的电场与发生介电击穿时击穿损伤形貌演变的具体影响。研究结果表明:填料与基体边界处存在较大的介电差异,可以使用较大介电常数的聚合物基体或较小介电常数的无机填料来减小其界面处的高电场区域,继而提高复合材料的耐击穿能力;同时发现当无机填料分散更均匀时,其树状损伤通道更容易产生分支,此种情况将使介电击穿的树状损伤通道的损伤位点增多,延缓其损伤速度,继而提高复合材料的耐击穿性能。该研究结果将为开发高储能密度且具有优异击穿性能的有机-无机复合电介质材料提供坚实的理论依据。

Compared with other electric energy storage devices,dielectric capacitors made of dielectric composites have great advantages in fast charging and discharging capacity with high power density.A dilemma of improving the energy density of dielectric composites and synchronous optimizing their breakdown performance is becoming an intriguing research direction.To further adjust the contradiction between dielectric constant and dielectric breakdown performance,here a finite element numerical simulation based on dielectric breakdown model(DBM)was proposed to study the effect of the distribution of inorganic fillers on the electric field and breakdown damage morphology in flexible polydimethylsiloxane(PDMS)based dielectric composite system.The results show that a large dielectric difference is observed between filler and matrix,which indicates that polymer matrix with a large dielectric constant or inorganic filler with a small dielectric constant can realize reducing the size of the high electric field area at the interface and improving the breakdown resistance of the material. This study further reveals that the more dispersed structure of inorganic fillers, the more likely its dendritic damage channels tend to branch, indicating that this situation is conducive to the increase of damage sites of dielectric breakdown dendritic damage channels, the decrease of damage rate, and the improvement of breakdown resistance of materials. All above data demonstrate that this study provides certain guidance for the development of organic-inorganic dielectric composites with both high energy storage and excellent breakdown performance.