Highly Ordered and Dense Thermally Conductive Graphitic Films from a Graphene Oxide/Reduced Graphene Oxide Mixture

We report a new approach to making highly dense, oriented, and crystalline graphite films from heat-treated and pressed graphene oxide (G-O). By introducing small-diameter reduced graphene oxide (rG-O) flakes into the graphene oxide starting material, we found that after heat treatment at 3,000°C, the sample density and atomic order substantially improved over a film composed, at the outset, only of pure G-O flakes. A subsequent mechanical press increased the density but reduced the atomic order. A second 3,000°C heat treatment restored the graphitic structure with graphitization metrics exceeding even those of the first heat treatment. The optimized graphitic film with an original concentration of 15 wt % reduced G-O in G-O gave well-oriented graphitic films with a density of 2.1 g cm−3, cross-plane thermal conductivity of 5.65 W m−1 K−1, and in-plane thermal conductivity of 2,025 ± 25 W m−1 K−1.