Microstructure of copper/graphene composite obtained by high-pressure torsion

Abstract

Copper/graphene matrix composites are promising for a wide range of applications due to their good thermal and electrical conductivity. However, there are important problems in the synthesis of copper/graphene composites due to poor dispersion of graphene in the matrix and weak interfacial bonding. Intense plastic deformation by high-pressure torsion makes it possible to obtain bulk samples with nanocrystalline structure, free from pores and impurities. This method was successfully used to fabricate Cu/graphene composite from thin copper foils obtained by electrodeposition and coated with a monolayer of graphene. The initial foils contained a high proportion of twin boundaries, which provides both high strength and enhanced conductivity of such foils. The microstructure of the composites obtained from the foils was found to be homogeneous with an equiaxed grain size of about 300 nm. Despite the decrease in the proportion of coherent twin boundaries in the process of high-pressure torsion, the mechanical properties of the composite increased, which is apparently due to dynamic recrystallisation and the formation of a homogeneous fine-grained structure.