Architecting graphene nanowalls on diamond powder surface

Graphene nanowalls (GNWs) have been synthesized on diamond particle surface by a simple heat-treatment process in vacuum induction furnace. The thickness of the as-grown GNWs is in the range of 20-40 nm, and most of the nanowalls are smooth and flat. The growth of GNWs is affected by the type of catalyst and treatment temperature, and the mixed catalytic effect of Fe and Ni is better than Fe or Ni respectively. High-density GNWs was grown on the diamond particle entire surface, when the heat treatment process is performed at 1473 K. Al/diamond composites with high thermal conductivity of 423 W/(m K) was obtained, which was achieved by the formation of large number of GNWs on the diamond particle surface. Systematic analyses reveal that the growth models such as classic precipitation upon cooling (PUC) model are not applicable to explain this kind of GNW's growth mechanism. Hereby, an extended PUC model is proposed to interpret the GNW's growth process on diamond surface.