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

Abstract

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 (λ_⊥) and in-plane (λ_‖) directions were controlled by the consolidating pressure and growth time of the CNCs. The remarkable increase in λ_⊥ and the resilience of the CNC–GT blocks were further optimized using microstructures of CNCs at the interface. The maximum λ_⊥ of the CNC–GT blocks (∅ 3 cm × 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 λ_⊥, good resilience properties and dimensional stability could be developed to be highly thermally conductive and resilient interface materials for heat sealing.