Although graphene-based thermal interface materials (TIMs) have great potentials in removing excess heat generated during highly efficient running of electronic devices, their practical applications are usually limited by their unsatisfactory thermal conductions, which are mainly caused by unsatisfactory dispersion and distribution, low loading, and low quality of graphene sheets, as well as the thermal interfacial resistance between graphene sheets and polymer matrix. Herein, we develop vertically aligned graphene hybrid foams (GHFs) with high densities by hydrothermal reduction of graphene oxide in the presence of high-quality graphene nanoplatelets (GNPs) followed by air-drying. The reduced graphene oxide sheets play an important role in constructing a vertically aligned interconnection network for accommodating GNPs during the hydrothermal reduction process, while the incorporated GNPs not only make the thermal conductance network denser but also prevent excessive shrinkage of the foams during air-drying. More critically, graphitization of GHF at 2800 °C removes the residual oxygen-containing groups and heals the defects of their reduced graphene oxide component, leading to high-quality graphene foams. The resultant vertically aligned high-quality graphene porous architecture with high density as an ideal thermal conductance network of TIMs is highly efficient in improving the thermal conductivity of its epoxy composite, which exhibits an ultrahigh through-plane thermal conductivity of 35.5 W m-1 K-1 at a graphene loading of 19.0 vol %. The excellent thermally conductive performance makes the annealed GHF/epoxy composites suitable for the thermal management.
Keywords: composites; graphene foams; graphitization; thermal conductivity; vertical alignment.