Introducing deep trap states for high dielectric strength of aramid-based composite films

Abstract

Aramid nanofiber (ANF)-based composites have drawn tremendous interest in high-voltage electrical systems due to their superior insulation strength, thermal stability, and mechanical endurance. However, the filler agglomeration and interface compatibility have retarded further improvement of the dielectric performance. Herein, the nano-titanium dioxide (TiO₂) particles treated by aminopropyl triethoxysilane (APTES) serve as the inorganic fillers, which are doped in the ANF to prepare the composite nano-paper via the blade coating method. The electrostatic interaction between the ANF and fillers highly promotes their uniform distribution. Compared to the pure ANF paper, the composite paper has a denser structure with reduced pores and defects, which significantly improves its dielectric performance with inhibited partial discharge development. At a filler loading of 3 wt% (mass fraction), the breakdown strength is increased by 70.5% to a maximum value of 358.1 kV/mm, while the bulk conductivity is minimised to 5.2 × 10⁻¹⁷ S/m, representing an 88.1% decrease. By analysing the energy band structure of each component, energy barriers at the interface for electrons (1.48 eV) and holes (0.40 eV) are determined. These values indicate deepened trap energy levels, which greatly strengthen the carrier trapping effect for improved dielectric performance.