Toward Effective Synergetic Effects from Graphene Nanoplatelets and Carbon Nanotubes on Thermal Conductivity of Ultrahigh Volume Fraction Nanocarbon Epoxy Composites

Utilizing synergetic effects of different fillers is an important strategy to design and develop high-performance nanocomposites. However, owing to the well-known problems such as dispersion, solution viscosity control, and so on, synergetic enhancement effects are usually offset by the defects induced by fillers in highly loaded nanocomposites. In this work, remarkable synergetic efficiency was realized in graphene nanoplatelet (GNP) and multiwalled carbon nanotube (CNT) highly loaded epoxy composites through a well-designed fabrication method. Dramatic thermal conductivity enhancement was observed in the epoxy composites with 10-50 vol% nanocarbon filler due to synergetic effects. For example, the composite with 20 vol% CNTs and 20 vol% GNPs possess a thermal conductivity up to 6.31 W/mK. This is even much higher than that of the composites with individual 50 vol % CNTs or 50 vol% GNPs. A maximum thermal conductivity 7.30 W/mK was obtained, which is 38-fold of that of the pure epoxy resin. Thermal transport channels in the composites were thoroughly analyzed, and the mechanism of high synergetic effects achieved in thermal conductivity enhancement was discussed from the viewpoints of intrinsic properties, dispersion, contact, and matrix interaction of the fillers.