Study On Preparation And Properties Of Carbon Nanotubes Reinforced Copper Matrix Composites

With the rapid development of modern science and technology, traditional metalmaterials have failed to meet people’s requirements on material properties. Comparedwith other materials, carbon nanotubes (CNTs) have been considered as an excellentcomposite reinforcement due to their good mechanical properties, electricalconductivity, chemical and thermal stability. However, the practical application ofCNTs in composite materials has been limited because of thier drawbacks, such asagglomeration, poor wettability with meatl matrix, and high price.In this paper, two methods including electroless plating and molecular levelmixing were used to improve the dispersion and wettability of CNTs with coppermatrix. CNTs reinforced copper matrix composites (CNTs/Cu) were prepared bypowder metallurgy technology. Scanning electron microscopy (SEM), transmissionelectron microscopy (TEM), optical microscopy (OM) and X-ray diffraction (XRD)were used to analyze the morphology, dispersion, and phase composition of thecomposites.(1) Copper nanoparticles were electroless plated on the surface of CNTs in orderto disperse CNTs homogeneously within the matrix powders. A series of treatments ofCNTs including purification, oxidization, sensitization and activation were used to addactivated sites before electroless plating. A contiunous layer of copper nanoparticles onCNTs can be deposited at the temperature of the plating bath of80oC and the pH valueof12.(2) The composites of CNTs and copper powders were prepared by mechanicalball milling method.The CNTs can be well dispersed among the copper powders at theball milling speed of300r/min, the milling time of1h, and the CNTs content of1.0 wt.%. The hardness of CNTs/Cu composites containing1.0wt.%CNTs was enhancedup to61.4%compared to pure copper. The density and electrical conductivity ofCNTs/Cu composites were decreased by increasing the CNTs weight fraction. Theelectrical conductivity of CNTs/Cu composites containing0.5wt.%CNTs is44.43S/m, which reaches94%of the conductivity of pure copper. Moreover, the electricalconductivity of the composites prepared with CNTs coated copper is much higher thanthat of composites prepared with CNTs without treatment.(3) The molecular level mixing method was employed to disperse CNTs in copperpowders homogeneously through using hydrazine hydrate as a reducing agent. Theresultant mixture was mixed with pure copper by ball milling method and the CNTs/Cucomposites were fabricated by powder metallurgy. The results show that copperparticles with several hundreds of nanometers can be obtained among the CNTs. Whenthe mass fraction of CNTs is5.84%, the relative density of composite material is88%;the mass fraction of carbon nanotubes is5.52%, the hardness can be achieved at5.756HBS, conductivity is33.42Ms/m.