Experiments and modeling of thermal conductivity of flake graphite/polymer composites affected by adding carbon-based nano-fillers

Enhancement of thermal conductivity of natural flake graphite/polymer (NFG/polymer) composite sheets, prepared with tape casting method, was studied by adding carbon-based nano-fillers including carbon black, carbon nanotube (CNT) and graphene. The in-plane thermal conductivities of the composites, i.e., the thermal conductivities along the tape casting plane, were measured. The improvement of thermal conductivities of the composites was observed to be up to 24% by adding CNT and 31% by adding graphene at 10 wt.%. Micro-structures of the NFG/polymer composites were revealed by X-ray diffraction patterns and field emission scanning electron microscopy images to delineate the mechanism of thermal conductance in the composites. From the observed structure, a new thermal conductivity model for the composites with CNT and graphene additives was constructed based on a bridging mechanism. The new model applies well to the measured thermal conductivities of the as-prepared samples. It is expected that the model could also be applied well to composites added with other homologous materials for bridging thermal contacts.