Electric field distribution around asymmetric agglomerate model reconstructed from FIB–SEM images of epoxy nanocomposite

This study focussed on determining the electric field distribution formed by asymmetric agglomerates in order to elucidate the mechanism by which large agglomerates reduce the dielectric breakdown strength of nanocomposites. Epoxy nanocomposite sample was prepared by adding 2.5 vol% of TiO₂ nanoparticles with a primary particle size ranging from 30 to 50 nm. The three-dimensional (3D) structure of the epoxy nanocomposites with a thickness of 5 μm was analysed via focussed ion beam and scanning electron microscopy. The 3D reconstruction was performed using 250 observation images, and a 3D model of the particle in the observational range was obtained. The electric field distribution for the 3D model of the agglomerate with the largest size was determined using the finite element method. In addition, we constructed a calculation model that effectively accommodate changes in the direction of the applied electric field. Subsequently, we examined the changes in the maximum electric field intensity around the agglomerate.