The manufacturing and properties of a nano-laminate derived from graphene powder

Abstract The work presents a method of consolidation of graphene flakes (platelets) into a bulk material showing high anisotropy of thermal, electrical and mechanical properties. Such materials can be used as directional high-temperature thermal insulators similar to graphite foils, but due to much finer microstructure they may exhibit different, possibly enhanced properties. The graphene flakes were consolidated by a filter pressing of propanol suspension followed by a hot-pressing of produced green bodies at 2200 °C under 25 MPa in a protective atmosphere. The hot-pressing step was necessary to force orientation of the flakes and to densify the material. Microstructural observations, mechanical strength and elastic properties assessment, as well as thermal and electrical properties analysis were performed. Scanning electron microscopy revealed that microstructure of the material consisted of highly-oriented layers of the graphene flakes. It resulted in a distinct anisotropy of thermal conductivity (360 vs. 3 W/mK), coefficient of thermal expansion (25·10 −6 vs. −1·10 −6 1/K) and electrical resistivity (60·10 −6 vs. 850·10 −6  Ω m) of the material in the in-plane and through plane direction, respectively. The material showed brittle behavior, but it could be machined.