Investigation On Preparation And Properties Of Copper Matrix Composites Reinforced With Graphene

Ni-doped graphene powders were synthesized by chemical reduction,and the morphology and valence state were characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).Subsequently,copper matrix composites reinforced with Ni-doped graphene were prepared by ultrasonic treatment,three-dimensional vibration blending and spark plasma sintering(SPS),and the effect of spherical copper powder on the properties of copper matrix composites prepared with the same method were comparatively studied as well.In addition,graphene oxide and dendritic copper powders were mixed directly,and then the copper matrix composites reinforced with reduced graphene oxide were prepared by hot pressing sintering in different atmospheres.The phase constituents and microstructure of the graphene reinforced copper matrix bulk composites were characterized by X-ray diffraction(XRD)and scanning electron microscopy(SEM),and the hardness and electrical conductivity were tested as well.The following conclusions can be drawn from above investigations.The Ni-doped graphene compound powders are synthesized using hydrazine hydrate as reducing agent at 90℃ in water bath for 3h,followed by vacuum drying and vacuum freeze-drying,respectively.The results show that the desired compound powders can be obtained by vacuum freeze-drying.Graphene presents transparent thin sheet,and nickel ions are reduced into nickel particles,which are uniformly distributed on the interlayer of graphene.Most of the oxygen-containing functional groups of graphene oxide can be removed effectively,and the oxygen content is decreased from 28.98at.%to 12.35at.%.Ni-doped graphene is wrapped on dendritic copper powder after ultrasonic treatment and three-dimensional vibration blending.The hardness of copper matrix composites prepared with the dendritic copper powder increases and then decreases with increase of Ni-doped graphene,while the relative density and electrical conductivity decrease.The optimal comprehensive properties of the copper matrix composite can be obtained at 0.5wt.%Ni-doped graphene,and the hardness and electrical conductivity are 81.62HV and 87.93%IACS,respectively.Compared with pure copper,the hardness is increased by 59.93%,while the electrical conductivity is decreased by 1.93%.Ni-doped graphene has poor bonding with spherical copper powder after powder mixing process.For the 0.5wt.%Ni-doped graphene reinforced copper matrix composite prepared with the spherical copper powders,the hardness and electrical conductivity are 71.23HV and 79.52%IACS,respectively.Compared with pure copper,the hardness is increased by 41.27%,while the electrical conductivity is decreased by 5.98%.The properties is worse than that of copper matrix composites prepared by dendritic copper powders.It suggests that the properties of copper matrix composites with the dendritic copper powders are beneficial for the improvement on the properties of copper matrix composites.The oxygen-containing functional groups of graphene oxide can be removed effectively and the reduced graphene oxide can be obtained in hydrogen and nitrogen atmospheres at 1000℃.The properties of copper matrix composites prepared in hydrogen atmosphere are better than those in nitrogen atmosphere.With increase of reduced graphene oxide,the hardness of copper matrix composites increases and then decreases,while the relative density and electrical conductivity decrease.The copper matrix composite has the optimal comprehensive performances at 0.5wt.%reduced graphene oxide,the hardness and electrical conductivity are 63.25HV and 91.40%IACS respectively.Compared with pure copper,the hardness is increased by 30.41%.