Influence of Al2O3 Contents on the Progression of Electrical Tree in Polyetherimide Films

Dielectric nanocomposites are considered to be the most promising energy storage material due to their fast charging and discharging capabilities and high-power density. Pre-breakdown degradation mechanisms for dielectric nanocomposites have become one of the current research hotspots to further improve the energy storage performance. Herein, the Weismann–Zeller (WZ) model is used to simulate the transmission path of the electric tree and the evolution of breakdown damage morphology for polyetherimide (PEI) polymers with the addition of 1-D Al2O3 platelets. Simultaneously, the distribution of electric displacement and electric potential is analyzed using COMSOL Multiphysics. From the simulation results, the electrical tree tends to be more bifurcated, the fractal dimension of the electric tree increases first and then decreases with the continuous addition of Al2O3 platelets. Appropriate quantities of Al2O3 platelets can effectively inhibit the progression of electric tree, delay the damage speed, and finally improve the breakdown strength of nanocomposites. An electric potential can be concentrated on the interface between platelets and polymer matrix due to their large permittivity difference. The above research can provide guidance for designing dielectric nanocomposites with high breakdown strength and high energy storage density in the application of power electronic devices.

I. Introduction

In recent years, dielectric nanocomposites have attracted great attention in high-frequency, high-voltage, and high-temperature environments due to their ultrahigh power density and superior response time [1], [2], [3]. According to the calculation formula of energy storage density () of dielectrics: (where , , , and E denote discharge energy density, maximum/remnant electric displacement, and the applied electric field), both large breakdown strength () and strong electrical displacement (or high permittivity) can promote large of polymer nanocomposite. Thus, polymer/ceramics nanocomposites are promising choices due to the advantages of high resistance to penetration of polymer matrix combined with high electrical displacement of ceramic nanofillers [4], [5], [6].