Fabrication And Electrical Conductivity Of Reduced Graphene Oxide/Copper Composites

Copper materials are widely used in electrical,electronic,machinery manufacturing,aerospace and many other fields due to their excellent performance and lower cost.Modern applications show an increasing demand for copper,especially ultra-conductive copper and copper materials with both high strength and high conductivity.One of the most promising ways to coordinate the strength and conductivity inversion is adding the emerging two-dimensional nano-carbon graphene with excellent properties into copper matrix to form graphene/copper matrix composites.There are mainly three key points in fabricating graphene/copper matrix composites: a)Strong interfacial bonding between graphene and copper;b)Microstructure and graphene alignment in copper matrix;c)Structural integrity and homogeneous dispersion of graphene.This paper aimed at finding a novel method to fabricate graphene/copper matrix composites with high performance and in large scale.First,this paper proposed the suspension-slurry processing based on flake powder metallurgy to fabricate laminated rGO/Cu composites,which includes ball milling of copper powders,surface modification,GO dispersion,PVA removal,GO reduction,composite powders assemble,and densification.Then,this paper investigated the effect of different factors on electrical conductivity:(1)Balling milling time will influence the electrical conductivity,and RGO/Cu composite with thicker flakes and less ball milling time will have higher electrical conductivity.(2)Annealing process has no significant effect on electrical conductivity.(3)Both hot forging and hot rolling can significantly increase the electrical conductivity,but excessive process will causing electrical conductivity decreasing on the contrary.(4)Mixing rGO/Cu composite powders and pure copper powders can increase the electrical conductivity,but it will destroy the laminated structure of rGO/Cu composites.(5)Liquid phase sintering will result in the rGO/Cu bulk composites pulverization.The composite powder had good sphericity and graphene was uniformly dispersed on the surface of monocrystal Cu particle.A mechanism is proposed based on liquid/solid interface interaction combining the surface energy minimization of liquid Cu and low wettability of molten Cu on graphene.Next,this paper optimized the graphene reinforcements and copper matrix.For reinforcements,microwave reduction was used to obtain high quality graphene and its efficiency on quickly fabrication of high quality graphene was verified.And this paper also investigated the effect of different factors on the microwave reducing effectiveness.For copper matrix,the paper improved the electrical conductivity of copper matrix by replacing the stainless steel milling ball with agate milling ball.Finally,the rGO/Cu composite wire was prepared through wire drawing,and the rGO was uniformly distributed inside the wire.Comparing to the rGO/Cu bulk composite,the density and electrical conductivity of the wire greatly increased,and they further increased after the annealing process.The strength of the wire is not high because a hole appearing in the center,but the plasticity was greatly improved by annealing.Then,this paper analyzed the different microstructure before and after annealing.There is a tendency of grain orientation distribution inside and the grain size along the wire axial direction is larger than that along the wire radial direction.Annealing process can eliminate the crystal defects and improve the conductivity of the wire.