Incorporating Ag Nanowires into Graphene Nanosheets for Enhanced Thermal Conductivity: Implications for Thermal Management

With the increasing integration of electronic devices, there are growing demands for excellent thermal conductivity of thermal management materials on account of severe heat accumulation in practical applications. Graphene has been widely used in thermal conductivity nanocomposites because of its high in-plane thermal conductivity; however, inadequate through-plane thermal conductivity has become a major obstacle for extensive application. To deal with this issue, in this study, the Ag nanowire (AgNW) decorated reduced graphene oxide (rGO/AgNW) filler was prepared by in situ growth of AgNW between the interspacing of graphene nanosheets. As a result, the through-plane thermal conductivity of the nanocomposites reached 2.51 W/(m K), which was 260% more than pure graphene and 200% as high as those with Ag nanoparticle (AgNP) decorated rGO (rGO/AgNP). The enhancement that was attributed to AgNW created a "highway" of heat transfer pathways between the graphene layers and generated the synergistic effect of heat transfer with graphene. The nonequilibrium molecular dynamics simulation further revealed that the synergistic effect of boosting through-plane thermal conductivity was originated from the stronger excitation effect of low-frequency phonon (LFP) mode of AgNW. It would activate the LFP mode of the interface carbon atoms by resonance with AgNW and thus improve the phonon vibrational density of states of rGO/AgNW to realize more thermal transmit across the interface. It was expected that our rGO/AgNW hybrid structure as a thermal conductivity filler is of great promise for the high-efficiency through-plane heat transfer.