Thermal transport in stereo carbon framework using graphite nanospheres and graphene nanosheets

The influence of oxidized surface coverage and graphite nanosphere (GS) spacer on the thermal transport efficiency of graphene-based heat sinks within the 323-573 K temperature range has been investigated. A homogenizing method was adopted to intercalate GS into pristine graphene oxide (GO) and graphene nanosheet (GN), forming three-coordinated carbon framework for heat sink applications. The in-plane (k||) and through-plane (k⊥) thermal conductivity of graphene-based heat sinks are strongly dependent on the oxidation level of graphene and the presence of GS spacer in the stereo carbon framework. The presence of oxygen functionalities on basal planes or edges significantly reduces the phonon mean free path, unfavorable for the in-plane thermal diffusivity. At low oxidation level and with aid of GS spacer, the stereo GN-based heat sink delivers high equivalent k|| and k⊥ values up to 2250 and 95 W/m K, respectively. The k||/k⊥ ratios of the heat sinks can be reduced to the 14.1-23.9 range at 323 K, indicating that the carbon framework is capable of giving an integrated scaffold for the through-plane thermal transport. Because of its easy fabrication, the hierarchical carbon framework with low oxidation level delivers promising potentials in thermal management of electronic and photonic applications.