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 in the charge distribution of the composite on the macroscale are well studied. However, the effects of the interface on the nanoscale are not clear. In this work, first, we have demonstrated a method to modify the dielectric constant of composites by introduced air into the core−shell-structured M-SiO 2 @Al 2 O 3 particles. To clarify the electric interfacial region, we use Kelvin probe force microscopy (KPFM) to image with high spatial resolution of the surface charge distribution around an individual M-SiO 2 @Al 2 O 3 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 in the presence of the M-SiO 2 @Al 2 O 3 particles because of the increasing concentration of traps. This work provides significant insight into understanding the intrinsic interfacial behavior in insulating polymeric composites.

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