Temperature dependent thermal transport in graphene paper above room temperature

Graphene paper (GP) is more feasible to be integrated as a heat spreader than monolayer graphene due to its controllable size and moderate reduction in thermal transport properties. In this work, we fabricated and characterized GP to understand its thermal transport properties based on thermal bridge method combined with transient electro-thermal technique. The thermal conductivity of GP exhibits a highly temperature dependent property from 637 W/mK at room temperature to 757 W/mK at 80 degrees C, which is contrary to the trend of monolayer graphene. The increasing thermal property can be partially ascribed to the morphological and inner structural change of the composite at elevated temperatures. Surface roughness is found to be reduced by 30% from atomic force microscope imaging. This feature is beneficial for many industrial applications such as the cooling film in smartphones. The implementation of GP is further verified in a smartphone to simulate the heat dissipation performance. The results show that GP with temperature dependent properties exhibits much better cooling performance than conventional cooling films such as copper film.