Study On Microwave - Assisted Preparation Of CNT - Cu Composites And Its Properties

Carbon nanotubes(CNTs) are a kind of tubulous graphitic layers which have many excellent properties, and it is widely used in metal matrix composite as an ideal reinforcement materials. Meanwhile, copper-based composites reinforced with CNTs are extensively applied in wire and cable, wear-resisting bearing and microchip. Microwave is a kind of electromagnetic wave whose frequency ranges from 300MHz to 300GHz and microwave heating is a new type of heating methods, with the quick heat, the selective heating and higher thermal efficiency.In this paper, microwave heating was applied in the purification and surface modification(electroless copper plating) of CNTs, and the mechanism and effect of microwave heating was explored. What’s more, CNT-Cu composite samples were prepared by microwave sintering, the density, hardness, mechanical property were tesed and the microscopic structure was observed. The main results are: (1) The feasibility and high efficiency of microwave purification process in gas phase was proved, the analysis results of Raman、XRD、TGA、AFS、SEM、TEM revealed that the impurities were removed efficiently, the purification process does nearly no damage to the structure of MWNTs and the dispersity becomes better. The best purification result is achieved when microwave roasting temperature and time is 500℃ and 20min respectively. Furthermore, by contrast to normal oxidation method, microwave gas method achieves a higher purification efficiency and better purification results. (2) Compared with normal electroless copper plating, the rate of electroless copper plating treated with microwave was increased about 12 times. The uniform clad layer was obtained after microwave assisted treatment and did almost no damage to the structure of CNTs. The plating temperature was controled to be same in order to exclude the influence of thermal effect. So, the different plating rate is caused by the non-thermal effect. (3) The CNT-Cu composite materials prepared by microwave sintering have many outstanding properties. The sample containing 1wt.% CNTs sintered at 1000℃ for 30 min got a density and relative density for 8.3405g/cm3 and 96.95% respectively, the highest density was obtained for 98.09% when changing the content of CNTs for 2wt.%. The sample containing 2wt.% CNTs sintered at 1000℃ for 10min reached the highest hardness for 395.18HV. The 2wt.% CNTs dispersed in copper matrix homogeneously, acting as a superior reinforcement. The yield strength and strength of extension of CNT-Cu composite reached 254.14MPa and 346.85MPa respectively, which is enhanced up to about 40% and 20% compared to pure copper. However, the percentage elongation of composite are under 8% and the reduction of area are about 30%.