Preparation And Properties Of Graphene/Copper Composite Materials

Graphene reinforced copper matrix composites can theoretically possess both high conductivity and thermal conductivity of copper and high strength of graphene,which was expected to be widely used in aerospace,machinery industry,electronic packaging and other fields.However,graphene was difficult to disperse uniformly in copper matrix.The poor wettability and interface bonding between graphene and copper matrix made the properties of graphene-copper matrix composites far from the theoretical values.Therefore,the main direction of improving the properties of graphene reinforced copper matrix composites was to find suitable process methods and improved the interfacial bonding properties of composites through the design of the interfacial structure of composites.In this paper,graphene/copper composite powders with uniform dispersion were prepared by ball milling and adsorption methods respectively.Graphene/copper composite materials were prepared by high temperature reduction and vacuum hot pressing sintering.The effects of process parameters on the microstructure,electrical conductivity,thermal conductivity and mechanical properties of graphene/copper composite were discussed.Graphene/copper composites were prepared by ball milling method,the effects of graphene content and milling time on the microstructure and properties of graphene/copper composites were studied.When graphene content was low,graphene could disperse uniformly in the copper matrix,but graphene would agglomerate while the graphene content reached 0.9 wt%,resulting in the decline of mechanical properties of the composite.With the increase of milling time,the composite powder particles were refined and the mechanical properties of the composite material were improved significantly.However,the interfacial wettability and interfacial bonding properties between graphene and copper in composites can not be improved by ball milling method,and the electrical conductivity and thermal conductivity of the composites decreased in varying degrees.The uniform dispersion of graphene in copper matrix were achieved by adsorption method,and the wettability and interfacial bonding properties were improved by forming Cu₂O on graphene,improving the comprehensive properties of composite materials.The effects of graphene content,reduction time and hot pressing temperature on the microstructures and comprehensive properties of graphene/copper composites were studied.Copper powders with positive charge were obtained by surface modified,and graphene oxide with negative charge was uniformly adsorbed on the surface of copper powder by charge adsorption,which achieved uniform mixing.Under the thermal reduction,graphene oxide was reduced and a thin Cu₂O layer were formed at the graphene,which improved the wettability and interfacial bonding between graphene and copper,and improved the thermal conductivity,electrical conductivity and mechanical properties of the composites.During the hot pressing sintering process,the increase of sintering temperature was conducive to improve the density of materials and the interaction between graphene and copper,which would improve the properties of composites.When the graphene content was 0.6 wt%,the reduction time was 3 h and the hot pressing temperature was 900℃,graphene/copper composites possessed the best comprehensive properties,the thermal conductivity,electrical conductivity,microhardness,yield strength and tensile strength were 413W·m^-1·K^-1、93%IACS、95.4 HV、107.4 MPa、226.7 MPa,respectively.By introducing Cu₂O on the graphene in the composite,which would improve the wettability and interfacial bonding strength and reduce the thermal resistance,and then improved the thermal conductivity of the composites.The method provided a new idea for the preparation of graphene/copper composites with excellent comprehensive properties.