Preparation And Properties Of Aligned Carbon Nanotubes Reinforced Copper Matrix Composites

Because of the excellent thermal conductivity and electrical conductivity,Copper and its alloys had a wide range of applications in various industries.But the strength of copper was low,which limited to its application and development.Carbon nanotubes had a unique one-dimensional tubular structure,high strength,low coefficient of thermal expansion and excellent thermal conductivity along the axial direction.It gradually becomed the ideal material for strengthening and toughening.In this paper,the green body of carbon nanotubes reinforced copper matrix composites was prepared by mixing powder at different magnetic field strengths.The electroless plating of carbon nanotubes had a specific orientation in the copper matrix.Then the CNTs/Cu composites were prepared by different hot-pressing sintering process.Based on the mechanical properties,conductive and thermal conductivity of the sample,the optimized sintering process and the magnetic field parameters were obtained.Meanwhile the microstructure of CNTs/Cu composites was analyzed by optical microscope,X-ray diffraction,field emission scanning electron microscope and transmission electron microscope.At the same time,the ImageJ2 x software was used to analyze the orientation of CNTs in CNTs/Cu composites,and the influence of the orientation of CNTs on the properties of the composites was also studied.The experimental results showed that when the sintering pressure was 40 MPa,the sintering temperature is 650 oC,the holding time was 20 min and CNTs content was 0.5wt.%,the CNTs/Cu composites with better properties could be obtained.The relative density of the composites is more than 99%.Its tensile strength was 234 MPa and the conductivity reached 93%IACS.When the magnetic field intensity was 1.5T,the CNTs orientation of CNTs/Cu composites was the best.Compared with the longitudinal samples,the radial samples had higher tensile strength and thermal expansion coefficient.At 1.5T,the tensile strength of the radial sample is up to 262 MPa,and the coefficient of thermal expansion is 9.12×10^-6K^-1,which is much better than the longitudinal sample under the same magnetic field.The conductivity and thermal conductivity of the longitudinal samples were better than the radial samples.The conductivity of the sample was 91%IACS,which was significantly better than that of the radial sample 85%IACS at 1.5T.The thermal conductivity of the longitudinal sample was 256.7W/mK at 1.5T,which was higher than the thermal conductivity of the radial sample.Through SEM and TEM analysis,it was showed that the CNTs in the CNTs/Cu composite had a specific orientation in the magnetic field.The strip CNTs were arranged in parallel with each other in the radial samples.In the longitudinal samples the end of CNTs was uniformly dispersed in the copper matrix.