Three-dimensional interconnected graphene microsphere as fillers for enhancing thermal conductivity of polymer

Owing to distinguished thermal transfer property, graphene has attracted much attention as filler to enhance the heat transfer effect of polymers. However, the actual enhancement efficiency of thermal conductivity for graphene filled polymers is lower than that predicted value. One available solution would be to integrate two-dimensional graphene into three-dimensional interconnected graphene that can fully utilize graphene's performance. Herein, we report a three-dimensional interconnected graphene microsphere by liquid nitrogen driven assembly approach. When used as thermally conductive fillers for epoxy resin, the graphene microspheres exhibit high enhancement efficiency (437%) of thermal conductivity per 1 wt% loading, leading to the maximum out of-plane thermal conductivity of 0.96 Wm(-1) K-1. This increase is attributed to the well-organized three-dimensional network in graphene microspheres, which establish an effective heat conduction path inside the epoxy resin. These methods and results have laid a new foundation for the continued development of highly thermally conductive polymer materials.