Study On The Process Of Electroless Copper-plated Reinforced Copper Matrix Composites

Carbon nanotubes have a characteristic of low density,high strength,large specific surface area,good conductivity and thermal conductivity,low thermal expansion coefficient and strong acid and strong alkali resistance.But it also has the defects of easy reunite and poor wettability.In this paper,CNTs were surface modification treatment by electroless copper plating.CNTs/Cu composites were prepared by powder metallurgy method,and the effects of electroless copper plating CNTs and original CNTs on the properties of CNTs/Cu composites were compared.(1)The pretreatment process of CNTs was investigated.The effects of CNTs purification,activation and sensitization on the surface properties of carbon nano tubes were investigated.The characterization of TEM,XRD,EDS and IR spectra showed that the activated layer was composed of a layer of Pd and SnO particles on the pretreated CNTs surface.(2)The process parameters of electroless copper plating in CNTs were studied.The chemical plating solution was composed of reducing agent NaBH4,CuSO4·5H2O,complexing agent,stabilizer and dispersant.Single factor method was used to study the influence of bath pH value,plating time,plating temperature and CNTs concentration on electroless copper plating on CNTs.The uniformity and continuity of the copper layer on the surface of CNTs were analyzed by TEM,XRD,SEM and EDS,and the optimum process conditions were as follows:pH=11,t=30min,T=50,CNTs concentration:0.08g/L.(3)The interface structure of electroless copper plating on CNTs has been studied.It is observed by TEM that the CNTs/Cu(Interface)regions is copper(110)and the carbon layer infiltrates into a transition layer with an angle of less than 90;It is found by electron probe that electroless copper plating increases the wettability of CNTs and copper,and improves the agglomeration of CNTs;The mechanism of electroless copper plating on CNTs surface is discussed,which is caused by the mechanism of atomic hydrogen and the mechanism of electron reduction.(4)The mechanical and electrical properties of CNTs/Cu composites were investigated.The electroless plating copper CNTs and CNTs were added into the pure copper powder to obtain CNTs/Cu composite powders by high energy ball milling and the median diameter D50 and apparent density of CNTs/Cu composite powder were detected.Through experimental analysis,the median diameter D50 and apparent density of CNTs/Cu composite powder(0.25wt%CNTs after electroless copper)decrease from 50.91?m and 2.67g/cm3 to 39.12?m and 2.24g/cm3,respectively.By vacuum hot pressing,it is found that the conductivity,tensile strength and hardness of electroless copper plating CNTs/Cu composite are higher than those of without electroless copper plating CNTs/Cu composite.When the content of CNTs was 0.25wt%,the conductivity of CNTs/Cu composite powder without electroless copper plating and electroless copper plating of CNTs/Cu composite powder were 62.5%IACS and 77.21%IACS,the tensile strength were 212.50MPa and 272.174MPa,the hardness of 34.6Hv and 40.9Hv,respectively.