Investigation On Preparation Of Copper Matrix Composites Reinforced By Modified Graphene

Firstly,Cu doped grapheme and Cr doped grapheme composite powders were synthesized by in situ chemical reduction method.The effects of copper nitrate concentration and reduction time in water bath on the synthesis of doped copper graphene composite powders were investigated.The effect of chromium sulfate concentration and reductant on the synthesis of doped chromium graphene composite powder was investigated.On this basis,two kinds of modified graphene/copper composite powders were obtained by mixing two kinds of modified graphene powders with copper powders by ultrasonic vibration and magnetic stirring.Finally,two kinds of modified graphene reinforced copper matrix composites were prepared by cold pressing and high temperature sintering.The effects of the amount of two kinds of modified graphene composite powders on the microstructure and properties of copper matrix composites were also analyzed.The strengthening mechanism of two kinds of modified graphene/copper matrix composites was further discussed.The main results are as follows:(1)When the concentration of Cu(NO3)2 is 0.05mol/L,the effect of the Cu doped graphene composite powder synthesized by hydrazine hydrate reduction in water bath for 3 hours is the best.SEM observation showed that graphene oxide is reduced to form a typical graphene fold structure.Graphene lamellae are translucent flocculent and disorderly stacked.The doped copper particles were evenly dispersed on the transparent and thin graphene lamellae,which rectively prevented the agglomeration of graphene.(2)When the concentration of Cr2(SO4)3 is 0.05mol/L,the effect of Cr doped graphene composite powders synthesized by water bath reduction with glucose for 3 hours is the best.SEM observation showed that graphene oxide is reduced to form a typical graphene fold structure.The graphene lamellae are translucent and light.(3)After high-power ultrasonic vibration and magnetic stirring,SEM observation showed that Cu-doped graphene powder and copper powder mixed evenly.The structure of Cu-doped graphene is complete.Copper particles doped between graphene sheets did not fall off.Copper particles doped with graphene bonded firmly.When 0.5wt.%Cu doped graphene was added,copper matrix composites obtained better comprehensive properties.The density of copper matrix composites is 96.86%,and the electrical conductivity was 93.96%IACS,and the hardness value was 81.6HV,which was 69%higher than that of pure copper.(4)When 0.5wt.%Cu doped graphene was added,the tensile strength of copper matrix composites reaches 221 MPa,which is 23%higher than that of pure copper.SEM fracture morphology analysis showed that the fracture mode was ductile fracture,and the interface between graphene and copper matrix was well bonded.In the process of fracture,graphene with high strength can bear part of the load transferred by copper matrix,thus improving the mechanical properties of copper matrix composites.(5)Adding a small amount of Cr doped graphene significantly improves the properties of copper matrix composites.When 0.5wt.%Cr doped graphene was added,the graphene distribution in copper matrix was the most uniform.During sintering of chromium particles doped between graphene lamellae and copper matrix,the solid solution phase of copper and chromium was formed.Chromium particles doped between graphene lamellae connect graphene to copper matrix.Graphene/copper interfacial bonding mode has changed from simple mechanical bonding to stronger metallurgical bonding.At this time,the density of copper matrix composites is 96.81%,and the electrical conductivity was 91.29%IACS.The hardness of copper matrix composites reaches 85.6HV,77.6%higher than that of pure copper.The tensile strength of copper matrix composites reaches 245 MPa,which is 36%higher than that of pure copper.(6)Fracture morphology analysis by SEM showed that the fracture mode of doped chromium graphene reinforced copper matrix composites was ductile fracture.The copper-chromium solid solution phase formed during sintering exists in dimples.Cr doped graphene mainly distributes at the edge of dimples.In the process of fracture,graphene with high strength can bear part of the load transferred by copper matrix,thus improving the mechanical properties of the composites.