Tuned Local Surface potential of Epoxy Resin Composites by Inorganic Core-Shell Microspheres: The key roles of interface.

Designing and controlling the interface interaction between polymer and filler is a challenge for nanocomposite insulation materials with the enhanced insulating and thermal conductive properties simultaneously. Meanwhile, the roles of the interface on the charge distribution of composite at the macro scale are well studied. However, the effects of the interface in the nanoscale are not clear. In this work, firstly, we have demonstrated a method to modify the dielectric constant of composites by introduced air in the core-shell structured M-SiO2@Al2O3 particles. To clarify the electric interfacial region, we use a Kelvin probe force microscopy (KPFM) to image with high spatial resolution on surface charge distribution around an individual M-SiO2@Al2O3 particle embedded in the epoxy matrix. We find that the KPFM results of the distinct electric interfacial region are consistent with the finite element simulation. Moreover, the charge accumulation is much easier after the presence of the M-SiO2@Al2O3 particles due to an increasing concentration of traps. This work provides a significant insight to understand the intrinsic interfacial behaviour in insulating polymeric composites.