Preparation And Mechanical Properties Of MWCNTs/Cu Composites

The friction application under heavy load or high sliding speed requires higher strength,hardness and wear resistance of copper.How to give full play to the excellent performance of CNTs in copper matrix composites,the agglomeration of CNTs and the poor interface bonding between CNTs and copper matrix still need to be solved.This study first through electroless plating in the surface of multi-walled carbon nanotubes(MWCNTs)preparation of Ni,Cu,Ni/Cu three kinds of coating,and then use the sintering,hot extrusion and cold drawing process of the preparation of the MWCNTs bar reinforced copper matrix composites,and explored the process combination to improve its microstructure,mechanical properties and tribological properties of possibility.The results showed:(1)CNTs were dispersed in the copper matrix through ultrasonic wave and nitrogen-assisted powder mixing.The chemical coating deposited on the surface of MWCNTs improves the interface bonding between MWCNTs and copper matrix.(2)Hardness,tensile strength,yield strength and compressive strength are Ni-MWCNTs/Cu>Ni/Cu-MWCNTs/Cu>Cu-MWCNTs/Cu>Bare-MWCNTs/Cu from high to low.The reason is that among the three kinds of coatings on MWCNTs,the Ni coating is the most continuous and dense,and the interface bonding with Cu matrix is the strongest.The microhardness of nickel-plated MWCNTs/Cu composites along the parallel drawing direction reaches 146HV(50.1%higher than that of pure copper).The maximum tensile strength reached 392MPa(47.7%higher than that of pure copper).Compressive strength of 309.2MPa(20%higher than that of pure copper).That's better than most reported data.The main enhancement mechanisms are dislocation and load transfer effect.(3)Tribological performance from high to low in turn is Cu-MWCNTs/Cu>Bare-MWCNTs/Cu>Ni/Cu-MWCNTs/Cu>Ni-MWCNTs/Cu.The reason is that the interface bonding ability between copper-plated MWCNTs and copper matrix is the worst,so during the wear process,MWCNTs are most likely to fall off from the copper matrix and form carbon lubrication film,thus improving their frictional properties.The friction coefficient and wear rate of copper-plated MWCNTs/Cu composites are 0.32and0.45×10^-5mm^-3·N^-1·m^-1,respectively(reduced by 78%and 51%compared with pure copper).The main enhancement mechanism is that MWCNTs form load transfer,self-lubricating layer,and efficiently derive friction heat.(4)The MWCNTs/Cu composites exhibit obvious orthotropic anisotropy,and the mechanical and tribological properties of the materials in parallel drawing directions are significantly better than those in vertical drawing directions.The results show that Ni/Cu-MWCNTs/Cu composites are more suitable for friction applications under heavy loads or high sliding velocities.The results of this study can provide new insights for the preparation and application of carbon nanotube/copper composites with good mechanical and tribological properties.