In-situ synthesis of graphene nanosheets coated copper for preparing reinforced aluminum matrix composites

Graphene nanosheets (GNS) have attracted lots of attention as an ideal reinforcement in Al matrix composites. However, there are still challenges limiting the performance of the composites, sueh as the homogenous distribution of GNS in Al matrices, the structural integrity of GNS after ball-milling, and the interfacial bonding between GNS and Al matrices. This work presents a new approach to grow GNS on Al powders at 600 degrees C by in situ chemical vapor deposition (CVD) process, using methane as the carbon source, and Cu as the catalyst. The GNS coated Cu reinforced Al matrix bulk composites (Cu@GNS/Al) from the composite powders was fabricated by powder metallurgy (PM) technique. It was found that Cu2+ from CuCl2 can easily anchor onto the surfaces of Al particles uniformly though a nanoscale-disperse-method in alcohol, enabling the homogenously dispersion of Cu particles in Al matrices after being reduced from Cu2+ in hydrogen. With the assistance of Cu particles, network-liked GNS was successfully synthesized in-situ and strongly bonded with Al, resulting in a good mechanical performance of the composites. It is indicated that the tensile strength of the composites was improved by 200% compared to the unreinforced pure Al. The strengthening mechanism was mainly ascribed to the load transfer of GNS, precipitation strengthening of Al2Cu compounds after 400 degrees C annealing and dislocation strengthening.