Mirror-like and large grain graphite film: Synthesis and properties

Graphite films with large grain sizes have been reportedly obtained by using metal as catalysts, but the obtained graphite is mostly heavily wrinkled, thus containing defects that degrade its properties. We report the synthesis of mirror-like and large-grained graphite films with only a few nano kinks and controllable dimensions, achieved by using flat Ni-Mo alloy melts of the same lateral dimensions as the metal foils used to make this alloy melt. After formation of the graphite film, we deliberately evaporated out (much of the) Ni to produce a porous metallic substrate to dramatically weaken the substrate-graphite film interaction prior to cooling down to room temperature; with this step, the graphite film then had only a few nano kinks and a mirror-like appearance. The mirror-like graphite appears to be 100% AB-stacked with millimeter-sized grains that are much larger than the multi-micron grain size of highly oriented pyrolytic graphite and rivaled in size only by a small percentage of natural graphite. Our graphite films have an electrical conductivity of 5.59 × 10 ⁶ S/m at 4 K and 7.75×10 ⁵ S/m at 300 K. Tensile loading of macroscale samples showed an average Young’s modulus of 969 ± 69 GPa and average fracture strength of 1.29 ± 0.203 GPa, which are, to the best of our knowledge, the highest values reported for macroscale artificial graphite materials.