Three-dimensional graphene network is a promising structure for improving both the mechanical properties and functional capabilities of reinforced polymer and ceramic matrix composites. However, direct application in a metal matrix remains difficult due to the reason that wetting is usually unfavorable in the carbon/metal system. Here we report a powder-metallurgy based strategy to construct a three-dimensional continuous graphene network architecture in a copper matrix through thermal-stress-induced welding between graphene-like nanosheets grown on the surface of copper powders. The interpenetrating structural feature of the as-obtained composites not only promotes the interfacial shear stress to a high level and thus results in significantly enhanced load transfer strengthening and crack-bridging toughening simultaneously, but also constructs additional three-dimensional hyperchannels for electrical and thermal conductivity. Our approach offers a general way for manufacturing metal matrix composites with high overall performance.

Cu and Ag nanoparticle (NP) paste has emerged as a promising choice for high-power devices because of its excellent thermal and electrical properties. However, easy oxidation, high sintering temperature of Cu NPs, high cost, and high porosity of Ag NPs restrict the practical application. Although Cu–Ag composite paste can improve bonding reliability, there have been no reports of fabricating stable and reliable Cu–Ag composite paste joints. In this work, we reported a novel method for fabricating a nano Cu–Ag composite paste with excellent dispersibility and relatively uniform particle size distribution via polyol one-step reduction. These composite NPs exhibit outstanding antioxidant capacity. The sintering behavior of the composite NPs at different temperatures was analyzed. The electrical and mechanical reliability of nano Cu–Ag composite paste joints with different ratios were investigated. With the increase in Ag content, the porosity and resistivity of the joint decrease, and the shear strength increases. The bonding joint presents a low porosity of 1.92% and a high shear strength of 32.6 MPa under a 1:3 ratio of Cu to Ag. The molecular dynamics (MDs) simulation results imply that Ag-rich composite system can achieve low-temperature sintering and maintain the stability of the sintering process.