Thermally conductive and electrically insulating epoxy nanocomposites with silica-coated graphene

Abstract

Graphene oxide was reduced and functionalized simultaneously by reacting with 3-aminopropyltriethoxysilane (APTES) without the use of conventional reducing agents. Silica was subsequently formed in situ on APTES functionalized graphene (A-graphene) sheets by a sol–gel approach using tetraethyl orthosilicate as the precursor of silica. The covalently bonded APTES on A-graphene enhances the compatibility between A-graphene and silica nanoparticles. The silica-coated A-graphene (S-graphene) sheets were incorporated to improve the thermal conductivity of epoxy. The presence of silica nanoparticles not only enhances the interfacial interaction between S-graphene and the epoxy matrix, but also alleviates the modulus mismatch between the fillers and the matrix and thus benefits the interfacial thermal conductance. The thermal conductivity of the epoxy nanocomposite with 8 wt% S-graphene is improved by 72% in comparison with that of neat epoxy, while the electrically insulating feature of the nanocomposite is retained.