Interface interaction and synergistic strengthening behavior in pure copper matrix composites reinforced with functionalized carbon nanotube-graphene hybrids

Abstract

Strong interface bonding and effective load-transfer are the guarantees for developing high strength metal matrix composites (MMCs). Herein, the effect of residual oxygen in functionalized carbon nanofillers (CNFs) on the interface structure and the synergistic strengthening behavior of carbon nanotube-reduced graphene oxide (CNT-RGO) hybrids were investigated in Cu matrix composites. It was demonstrated that disordered areas and Cu2O nanoparticles were in-situ formed at the CNFCu interface in the oxygen-poor and oxygen-rich areas through diffusion of oxygen, respectively. Cu2O was grown from the Cu matrix by means of cube-on-cube to obtain the minimum interfacial energy, under which equivalent planes and directions of Cu2O and Cu matrix are matched across the Cu2OCu interface. A possible formation/evolution mechanism of the disordered areas and Cu2O involving oxygen content and sintering temperature was proposed. The ultimate tensile strength of 412 MPa was achieved in 1.5 vol% CNT-RGO/Cu composite sintered at 1023 K, which is significantly higher than that of CNT/Cu and RGO/Cu composites (231 and 263 MPa, respectively). Synergistic strengthening effect of CNT-RGO hybrids was investigated and analyzed based on strengthening models, and the trade-off between Orowan strengthening and load-transfer effect in CNF/MMCs was discussed to understand the synergistic strengthening behavior of CNT-RGO hybrids.