Study On Preparation And Properties Of Few-layer Graphene Reinforced Copper Matrix Composites

Graphene has extremely high physical and mechanical properties,is regarded as an ideal reinforcement to develop high performance metal matrix composites.Besides,graphene can be used in lubricating oil and anticorrosive coatings,showing good lubrication and corrosion resistance.In the present study,the copper matrix composites reinforced with few-layer graphene?GNPs/Cu composites?were prepared by ultrasonic dispersion,self-assembly method and vacuum hot-pressed sintering process.Density,Vickers hardness,electrical conductivity,wear resistance and corrosion resistance of the GNPs/Cu composites were systematically tested.Microstructures,wear and corrosion morphologies of the composites were observed and analyzed.The influence mechanism of graphene on microstructure and properties of the composites were deeply discussed.The dispersion techique of graphene in ethanol was developed.Polyvinylpyrrolidone?PVP?was proved to be an effective surfactant with 4 mg/mL to contribute the uniformly dispersion of graphene.The optimal ultrasonic time was selected for 3 h.The thickness of the dispersed graphene is about 1.56 nm with 4-5 layers.Theoretical calculation showed that there is a critical value about 0.5%of the volume fraction of graphene uniformly dispersed in copper.Graphene was uniformly dispersed in the 0.5%GNPs/Cu composite with small grain size of copper matrix.With increasing in the addition content,graphene was apt to agglomerate and some clusters of graphene could be observed in the GNPs/Cu composites.In the other hand,the density and electrical conductivity decreased with the increase of graphene volume fraction.The hardness of 0.5%GNPs/Cu composite significantly improved,which was 20.3%higher than that of pure copper.Meanwhile,this composites exhibited high density?98.5%?and electrical conductivity?53.7 mS/m?,which were only 0.7%and 6.3%lower than those of pure copper.The wear rate of the GNPs/Cu composites decreased with increasing in the volume fraction of graphene to 0.5%.The wear rate of 0.5%GNPs/Cu composites was 63.9%lower than that of pure copper being weared for 0.5h at applied load 2N and sliding speed 500r/min.However,the wear rate remarkably increased with further increasing in the volume fraction of graphene to 1%.Graphene contributed to change the wear mechanism of the composites from adhesive wear to oxidative wear earlier at low graphene content.At high volume fraction,graphene could act as a lubricant due to agglomeration of graphene with more layers.Compared with pure copper,the GNPs/Cu composites exhibited more stable wear performance under different sliding speeds and loads.Graphene could improve the corrosion resistance of the composite.The protective effect of graphene on corrosion resistance improved with the increase of graphene volume.Compared with pure copper,the self-corrosion current density of 2.0%GNPs/Cu composite decreased by 13.5%and its corrosion rate decreased by 40.9%.Graphene hindered the contact between soaking solution and composites as a physical barrier.In addition,the OH^-distributed more uniformly with increasing in the volume fraction of graphene,which was beneficial to convert the harmful corrosion product CuCl into the protective film of Cu₂O.Consequently,further corrosion could be inhibited and the corrosion resistance was improved.In this paper,few-layer graphene reinforced copper composites have been successfully developed.The 0.5%GNPs/Cu composite exhibited excellent comprehensive properties of high electrical conductivity,hardness,wear resistance and corrosion resistance.The results obtained in the present study can provide theoretical and experimental evidences to develop novel copper-based material with high properties.