Preparation of alumina-coated graphite for thermally conductive and electrically insulating epoxy composites

Abstract

Herein, highly thermally conductive and insulating epoxy composites were reported. Firstly uniform alumina-coated graphite flakes were successfully prepared by a two-step coating method of chemical precipitation with the aid of a sodium dodecyl sulfonate (SDS) surfactant using an inorganic precursor (aluminum nitrate) as the starting material. Then the alumina-coated graphite particles were incorporated into the epoxy resin. The thermal conductivity value of epoxy/alumina-coated graphite composite shows a significant increase from 0.22 W mK⁻¹ (neat epoxy) to 0.64 W mK⁻¹ by a factor of approximately 3 at the filler loading of 18.4%. Moreover, due to the presence of the alumina nanolayers coating on the graphite surface, epoxy/alumina-coated graphite composites could retain high electrical volume resistivity of >10¹⁰ Ω cm up to high filler contents, which was much higher than that of epoxy/graphite composites (<10⁵ Ω cm) at the same filler loadings. And they still could be regarded as insulators.