Anisotropic Enhancement in Thermal Conductivity of Graphene Foam/Polymer Composites Based on Uniaxial Compression

High-performance thermal interface materials are in increasing demand because of the problems of dissipating heat from high-power computing devices. To solve this problem, this study proposes a method of microstructural design through uniaxial compression of graphene foam along the out-of-plane direction. The thermal conductivity of the composites with graphene foam shows an anisotropic growth along the direction of the compressive strain. The in-plane thermal conductivity increases significantly from 0.189 to 1.669 W m⁻¹ K⁻¹ at an extremely low filler content of 2.24 vol%, whereas the out-of-plane thermal conductivity increases slightly to 0.303 W m⁻¹ K⁻¹. Moreover, the samples exhibit outstanding in-plane thermal conductivity enhanced efficiency, which reaches 415.19% at a 1.29 vol% graphene content. The mechanism of anisotropic thermal conductivity enhancement is revealed by constructing a theoretical model based on a geometrical unit cell simplified from the morphology of graphene foam. This uniaxial compression method of a 3 structure provides a novel direction for improving the thermal conductivity of polymeric matrix composites more controllably.