Flexible thermal interface materials based on diamond–graphene composite films prepared at different temperatures

Diamond and graphene, which have extremely high thermal conductivity, are considered ideal candidates for the preparation of high-performance thermal interface materials (TIMs). However, the development of flexible TIMs with efficient heat transfer paths still hampers their thermal management applications. Herein, a highly oriented diamond–graphene composite film (DGCF) was prepared by one-step microwave plasma chemical vapor deposition on carbon cloth (CC) using N-butylamine as a single liquid carbon source. The hybridized composition of sp3/sp2 and the heat transfer path length of DGCF are regulated by the deposition temperature and the thermal conductivity of CC/DGCF at 30 °C is 2.71 W m−1 K−1, which is 15 times higher than that of CC. Further flexible TIMs of CC/DGCF are achieved using thermal silicone grease (TG) as filler, and the thermal conductivity of the final flexible compound of CC/DGCF/TG is 6.97 W m−1 K−1 at 30 °C, which is 39 times higher than that of pure CC and 2 times higher than that of TG, respectively. In the actual TIMs performance test, the cooling efficiency is 1.4 times higher than that of the commercial thermal conductive silicone pad. Furthermore, finite element simulations demonstrated that the film at 800 °C has the optimal sp3/sp2 ratio for thermal response and the best thermal conductivity path structure. This finding provides a method for the design of highly flexible TIMs and increases the possibility of their practical application in electronic thermal management.