Thermal properties of epoxy resin based thermal interfacial materials by filling Ag nanoparticle-decorated graphene nanosheets

Epoxy resin based thermal interfacial materials (TIMs) with high thermal conductivity have been obtained by filling Ag nanoparticle-decorated graphene nanosheets (GNSs) as thermal conductive fillers. The thermal conductivity (k) enhancement of epoxy resin based TIMs increases with the thermal filler loading. The more decoration of Ag nanoparticles on the GNS surfaces, the higher thermal conductivity enhancement of epoxy resin based TIM is. It is proposed that the bigger Ag nanoparticles acting as “spacers” increase the distance between the graphene sheets more than the smaller ones. It is not easy for graphene sheets to form stacked graphitic structures and the high specific surface area as well as other unique properties exhibited by 2D graphene are retained. Furthermore, the larger particle size is desired to minimize the scattering of phonons because of low interfacial thermal barrier. The obvious enhancement of thermal properties should be also attributed to the high intrinsic k of graphene and the effective thermal conductive networks forming by graphene and Ag nanoparticles. The synergistic effects including the stronger phonon Umklapp scattering, better phonon transmission trough the interfaces, decreasing Kapitza resistance, and decreasing ability of heat transfer by electrons result in the slight variation of k with the temperature. The weak temperature dependence of k is beneficial for TIM applications and can be obtained by controlling the addition of hybrid thermal fillers and quantity of decorated silver nanoparticles.