Composites of epoxy/graphene-modified-diamond filler show enhanced thermal conductivity and high electrical insulation

In this work, we developed a single-step process to cast epoxy composites having a high thermal conductivity but a low electric conductivity. Performance of the epoxy was improved by incorporating diamond microparticles that were covered with few-layer graphene sheets on surfaces. We found not only did this modified filler improve the dispersion of diamond in the polymer matrix but it also decreased the interfacial thermal resistance between the diamond and epoxy while preserving an excellent electrical insulation. Graphene on diamond particle surfaces was synthesized by a vacuum-based heating procedure. After 70 wt% of diamond fillers were added, we obtained a composite having a thermal conductivity of 2.85 W m(-1) k(-1), which is 101% better than that of the composite with 70 wt% pure diamond as the filler, and 1190% better than that of a neat epoxy, with electrical resistivity maintained at 2.2 x 10(10) Omega m.