Improving thermal conductivity of graphene films with assistance of melamine

Due to the high degree of integration and high-power-density, excessive heat accumulation significantly endangers the performance of electronics. Therefore, developing high-performance thermal interface materials has become particularly vital for ensuring the regular operation of the electronics. Graphene-based materials attract great attention due to graphene's intrinsic excellent thermal conductivity. However, the internal defects in graphene and the lack of interlayer heat conduction pathways between graphene microsheets dramatically reduce the thermal conductivity of graphene-based materials. Herein, melamine is used to improve the thermal properties of graphene films prepared by thermal reduction of graphene oxide (GO) microsheets. With an addition of 3 wt% of melamine, the in-plane and through-plane thermal conductivities of the graphene films with a thickness of 35 mu m reach 1.32 x 103 and 5.09 W m-1 K-1, respectively. This is likely due to the covalent connection of graphene microsheets through amide structure formed by the chemical reaction between melamine and GOs, and the remedy of defects in graphene by nitrogen doping with the assistance of high-temperature annealing. The operation temperature of LED is greatly reduced, when the prepared graphene films is used as thermal interface material, compared to other commercial products. The results provide a promising way to improve the thermal properties of graphene films, which is of great significance for various applications, such as thermal management for high-power-density electronics.