Expanded graphite (EG) was coated with an insulating ceramic shell (SiO2 or boron nitride (BN)/SiO2) using a simple sol-gel process, and epoxy composites were prepared with these hybrid fillers. The electrical and thermal properties of the epoxy composite were investigated. The surface resistivity of the EG-BN-epoxy composite decreased rapidly to 10 degrees Omega/sq. with filler contents greater than 5 wt%. However, the surface resistivity showed 10(13) Omega/sq. for epoxy composites with SiO2/EG or BN/SiO2/EG contents greater than 5 wt%. Furthermore, the breakdown strength of the ceramic/EG-BN-epoxy composite was greater than that of the EG-BN-epoxy composite. Although coating of SiO2 with low thermal conductivity, the thermal conductivity of epoxy composites with low SiO2/EG or BN/SiO2/EG filler content was greater than that of the BN-epoxy composite due to improved adhesion between SiO2 and polymer resin interface. (C) 2017 Published by Elsevier Ltd.