Carbon hybrid fillers composed of carbon nanotubes directly grown on graphene nanoplatelets for effective thermal conductivity in epoxy composites

Carbon nanomaterials are generally used to promote the thermal conductivity of polymer composites. However, individual graphene nanoplatelets (GNPs) or carbon nanotubes (CNTs) limit the realization of the desirable thermal conductivity of the composite in both through- and in-plane directions. In this work, we present the thermal conductivity enhancement of the epoxy composite with carbon hybrid fillers composed of CNTs directly grown on the GNP support. The composite with 20 wt% hybrid filler loading showed 300% and 50% through-plane thermal conductivity improvements in comparison with the individual CNTs and GNPs, respectively. Moreover, it showed an enhanced thermal conductivity of up to 12% higher than that of the simply mixed GNP and CNT fillers. In more detail, hybrid fillers, whose CNTs were synthesized on the GNP support (Support C, Fe/Mo–MgO:GNP=1:0.456) for 60 min via chemical vapor deposition process, presented the highest through-plane thermal conductivity of 2.41 W m−1 K−1 in an epoxy composite. (paper)