Enhanced cross-plane thermal conductivity and high resilience of three-dimensional hierarchical carbon nanocoil-graphite nanocomposites

Three-dimensional hierarchical carbon nanocoil-graphite (CNC-GT) nanocomposite blocks were prepared by the growth of CNCs at the interlayer of expanded GT using chemical vapor deposition followed by hot-pressing. The distribution and density of the CNCs were tuned by vacuum impregnation for catalyst loading and growth time, respectively. Helical CNCs with spring-like structures were observed by scanning electron microscopy and transmission electron microscopy. The CNC-GT blocks showed a higher density and lower porosity than GT due to the intercalation of CNC fillers. The thermal conductivities of the CNC-GT blocks in the cross-plane (lambda(perpendicular to)) and in-plane (lambda(parallel to)) directions were controlled by the consolidating pressure and growth time of the CNCs. The remarkable increase in lambda(perpendicular to) and the resilience of the CNC-GT blocks were further optimized using microstructures of CNCs at the interface. The maximum lambda(perpendicular to) of the CNC-GT blocks (empty set 3 cm x 2 mm) of up to 23.6 W m(-1) K-1 was about five-fold higher than that of GT at 4.9 W m(-1) K-1. This feature arose from improved phonon transfer in the cross-plane through intercalated CNCs at the interlayer. Moreover, a high resilience ratio of 84.1% and a low compressibility (17%) were also obtained for the CNC-GT blocks due to the excellent elasticity of CNCs. The CNC-GT blocks with high lambda(perpendicular to), good resilience properties and dimensional stability could be developed to be highly thermally conductive and resilient interface materials for heat sealing.