Power electronic devices fabricated from epoxy composites have good electrical insulation properties. Facing the problem of severe heat generation due to the increased integration of devices, it is important to improve the thermal conductivity of epoxy composites for practical applications. In order to reduce the interfacial thermal resistance between filler and epoxy resin, we report a method to improve the compatibility between filler and resin matrix and reduce the scattering of phonons at the interface between filler and resin by coating SiO2 on the surface of Fe3O4. Also, since the potential barrier between SiO2 and resin matrix is smaller than that between Fe3O4 and resin, the electrons is less likely to accumulate at the interface leading to local electric field distortion, and the breakdown voltage of the composite is thus enhanced. The results show that the thermal conductivity is increased by up to 320% at low filler load (30 wt%) compared with the pure epoxy resin without filler, and the breakdown voltage of the thickest SiO2-coated sample is increased by 203% compared with the thinnest sample, which effectively reduces the interfacial thermal resistance between Fe3O4 and resin and increases the breakdown voltage of the composite.

epoxy;thermal conductivity;breakdown strength;core-shell structure nanoparticles