Fabrication of Cu-CuG nanocomposites with enhanced mechanical strength and reduced electrical resistivity

Abstract

Graphene was ball-milled with copper powder to acquire copper-graphene (CuG) powder. One and two percent of CuG in weight were added to stacking layers of fully annealed copper sheets and processed using 2, 4 and 6 cycles of accumulative roll bonding (ARB), leading to 2 mm thick copper-graphene nanocomposites with 20, 80 and 320 layers. With respect to the initially annealed copper sheet, the strength of the nanocomposites increased to the cost of significant loss in ductility. Reduced ductility was attributed to the low bonding quality in the form of existence of voids and the graphene chemistry which resulted in delamination and decohesion of the stacking sheets forming the nanocomposite during tensile tests. After 2 and 4 cycles of ARB, the electrical resistivity was increased which was attributed to the high density of defects and dislocations in addition to poor bonding between the stacking layers of the nanocomposite. Reduced electrical resistivity was achieved after 6 cycles of ARB which can be an indication of the improvement of the bonding at the interface of the nanoparticles with the matrix in addition to the reduction in voids at the interfaces of the stacking layers of sheets. Comparison between the nanocomposites with similarly fabricated multilayer sheets with no graphene addition indicated reduction in resistivity which demonstrates the positive effects of graphene on reducing resistivity. Mechanical strength, ductility and electrical resistivity were found to improve in the nanocomposite with 2% of CuG addition which was followed by further reduction in resistivity by full annealing.