Abstract: The observed highest electrical conductivity of graphene in copper matrix composites can exceed that of free-standing graphene or copper matrix by more than three orders of magnitude, because of the work function difference and corresponding electron doping effect between graphene and copper. In this work, the enhancement mechanisms of electrical conductivity of graphene are further clarified by regulating interfacial microstructures and atomic bonding states through a hot-pressed (HP) annealing process, along with analyzing corresponding variations in electrical conductivity. The effects introduced by the HP-annealing process can be directly observed through experimental characterizations, which mainly manifest as the orientation transformation of the copper matrix and an increase in the content of Cu-C bonds. This provides an effective method for regulating the key factors beneficial for electrical conductivity, and the coupling relationships among various effects have also been confirmed through calculation. The uniform orientation relationship of the matrix on both sides of graphene and the axial compressive strain introduced by HP-annealing can reduce the Cu-C layer distance, which can promote charge transfer and bonding trend, clarifying the mechanism for enhancing the electrical conductivity of graphene. This regulation is universal and applicable to various graphene with different layer numbers, and it is of significance for further enhancing the electrical conductivity of graphene-reinforced metal matrix composites.

Key words: Graphene/copper composite, Electrical property, Interface, Hot-pressed annealing, Ultrahigh electrical conductivity