Effect of defects on thermal conductivity of graphene/epoxy nanocomposites

Abstract

Owing to the super thermal conductivity of graphene, graphene/polymer nanocomposites have the potential as thermal management materials in many applications. Previous studies have proved that the defects in the graphene sheets can greatly reduce the thermal conductivity of suspended graphene. However, the effects of defects on the interfacial thermal conductance and thermal conductivity of graphene/epoxy nanocomposites have not been well understood. In this paper, the effect of four common types of defects, i.e., single-vacancy, double-vacancy, Stone-Wales and Multi-vacancy, on the interfacial thermal transport between the epoxy and graphene was systematically investigated by using molecular dynamic simulations. The simulation results showed that the interfacial thermal conductance between graphene-epoxy could be considerably enhanced with the existence of Stone-Wales and Multi-vacancy defects. The underlying mechanism was explicated by using the phonon vibration power spectrum. Additionally, based on the effective medium theory and the simulation results, the effect of defects on the thermal conductivity of graphene/epoxy nanocomposites was investigated concerning different graphene filler sizes and volume fractions. Although the inherent thermal conductivity of embedded graphene may be decreased by its defects, it was possible to increase the thermal conductivity of the nanocomposites when the graphene filler size was smaller than a critical value.