Strengthening effect of graphene derivatives in copper matrix composites

Graphene is highly efficient in reinforcing metal matrix composites due to its intrinsic ultrahigh mechanical properties. Several synthesis methods have been developed to produce graphene. Consequently, the selection of graphene materials with various structures, such as layer number, lateral dimension and chemical modification, is a key issue to synthesize graphene-related composites. In the present study, two kinds of graphene derivatives, namely graphene nanoplatelets (GNPs) and reduced graphene oxide (RGO), were adopted to fabricate copper matrix composites through a modified molecular-level mixing process. Microstructure studies showed that GNPs exhibited flake shape, and RGO exhibited irregular strip or sheet shape in the composites powders. Some spherical-shape nanosized GNPs or RGO dispersed within Cu grain interiors were also observed under the transmission electron microscope. Both of the GNPs and RGO were well bonded with the copper matrix after sintering. GNPs showed an obvious aggregative trend when the volume fraction was above 0.5%, but 1.0 vol.% RGO was still uniformly dispersed in the matrix. Tensile tests indicated that GNPs showed good strengthening efficiency at content below 0.5 vol.% while RGO performed better when the content increased from 0.5 to 1.0 vol.%. The difference of relevant strengthening effect and mechanisms involved in the two composites were systematically discussed by combining with theory consideration and experimentation. [Display omitted] •Two graphene derivatives (GNPs, RGO) were used to fabricate Cu matrix composites.•A modified molecular-level mixing process was adopted to make composite powders.•GNPs and RGO showed different strengthening effect on Cu matrix composites.•The different strengthening effect and mechanisms were theoretically discussed.