Electrical and mechanical properties of poly(dopamine)-modified copper/reduced graphene oxide composites

Surface oxidation is frequently encountered in powder metallurgy of metals and alloys, and it leads to a reduction in their electrical conductivities. Therefore, it is highly desired to remove the naturally occurring oxide layer from the particles surface and to prevent its subsequent formation. A new approach was proposed in this study, where copper particles were mixed with graphene oxide (GO) sheets in an aqueous solution containing dopamine (DA) molecules. It was expected that polymerization of the DA molecules on the surface of the copper particle could promote both a reduction of surface oxide layer and the adhesion of GO sheets to the particles surface. The powder system was then washed, heat-treated in inert atmosphere and compressed at room temperature to form compacts. Electron microscopy revealed nearly ideal dispersion of GO sheets within the copper matrix. X-ray photoelectron spectroscopy showed a shift from Cu²⁺ to Cu⁺ and metallic copper in the coated and heat-treated samples, and Raman spectroscopy pointed to the increased amount of sp ² carbon as a result of the heat treatment. All DA/GO-coated and heat-treated compacts exhibited significantly higher electrical conductivity than those that have been made from pure copper powder or were not been heat-treated. Also, indentation measurements showed an increase in microhardness in samples with the shortest, 10 min, coating time and heat-treated at the highest, 600 °C, temperature.