School of Materials Science and Engineering, State Key Lab of New Ceramics and Fine Processing, Tsinghua University, Beijing, 100084, China.
Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA, 16802, USA.
Adv Mater. 2018 Jan;30(2). doi: 10.1002/adma.201704380. Epub 2017 Nov 22.
Understanding the dielectric breakdown behavior of polymer nanocomposites is crucial to the design of high-energy-density dielectric materials with reliable performances. It is however challenging to predict the breakdown behavior due to the complicated factors involved in this highly nonequilibrium process. In this work, a comprehensive phase-field model is developed to investigate the breakdown behavior of polymer nanocomposites under electrostatic stimuli. It is found that the breakdown strength and path significantly depend on the microstructure of the nanocomposite. The predicted breakdown strengths for polymer nanocomposites with specific microstructures agree with existing experimental measurements. Using this phase-field model, a high throughput calculation is performed to seek the optimal microstructure. Based on the high-throughput calculation, a sandwich microstructure for PVDF-BaTiO nanocomposite is designed, where the upper and lower layers are filled with parallel nanosheets and the middle layer is filled with vertical nanofibers. It has an enhanced energy density of 2.44 times that of the pure PVDF polymer. The present work provides a computational approach for understanding the electrostatic breakdown, and it is expected to stimulate future experimental efforts on synthesizing polymer nanocomposites with novel microstructures to achieve high performances.
理解聚合物纳米复合材料的介电击穿行为对于设计具有可靠性能的高储能介电材料至关重要。然而，由于这个高度非平衡过程中涉及的复杂因素，预测击穿行为具有挑战性。在这项工作中，开发了一个综合的相场模型来研究静电刺激下聚合物纳米复合材料的击穿行为。结果表明，击穿强度和路径显著依赖于纳米复合材料的微观结构。对于具有特定微观结构的聚合物纳米复合材料，预测的击穿强度与现有的实验测量结果一致。利用这个相场模型，进行了高通量计算以寻找最佳的微观结构。基于高通量计算，设计了一种 PVDF-BaTiO 纳米复合材料的三明治结构，其中上下层填充平行纳米片，中间层填充垂直纳米纤维。与纯 PVDF 聚合物相比，它的能量密度提高了 2.44 倍。本工作为理解静电击穿提供了一种计算方法，预计将激发未来在合成具有新颖微观结构的聚合物纳米复合材料以实现高性能方面的实验努力。
