High strength and electrical conductivity of copper matrix composites reinforced by carbon nanotube-graphene oxide hybrids with hierarchical structure and nanoscale twins

Cu matrix composites reinforced with carbon nanotube (CNT)-reduced graphene oxide (RGO) hybrids were prepared by molecular-level mixing (MLM). Hierarchical structure consists of carbon-rich region and carbonpoor region are formed through the self-assemble process by controlling the pH value during MLM process, and nanoscale twins in the Cu matrix are also formed during reduction and sintering process. It was demonstrated that both the hierarchical structure and nanoscale twins contribute to the mechanical properties and electrical conductivity of the composites. The ultimate tensile strength of 2.5 vol% CNT-RGO/Cu composite is 601 MPa, much higher than that of 2.5 vol% RGO/Cu composite (450 MPa) and pure Cu (294 MPa). The obvious grain refinement effect and higher load-transfer efficiency of CNT-RGO hybrids were believed to contribute to the high strength of CNT-RGO/Cu composite. At the same time, satisfied electrical conductivity of 83% and 85% International Annealed Copper Standard (TAGS) are retained in 2.5 vol% CNT-RGO/Cu and RGO/Cu composites, respectively. This work provides a better understanding of the architecture design of Cu composites with hierarchical structure and contributes to optimize their mechanical and electrical properties.