Plasma Assisted Preparation Of Carbon/Copper Powder And Its Composites

With the continuous improvement of the comprehensive performance of materials in important industrial fields such as aerospace,rail transit and electronic information,the shortcomings of pure copper in terms of strength and wear resistance seriously limit its development and application.The addition of carbon can not only enhance the mechanical properties of the copper matrix,but also exert its unique lubricity,which is regarded as an effective means to prepare high-strength and high-wear-resistant copper matrix composites.At present,how to effectively solve the problem of uneven dispersion of carbon in the copper matrix has become the main challenge for its large-scale industrial application.In this study,plasma-assisted chemical vapor deposition technology was used to realize the in-situ growth and coating of carbon on the surface of copper powder,and the C/Cu composite powder was formed by powder metallurgy.The effects of plasma process parameters on the properties of multi-scale copper powder and the carbon in-situ growth coating process were systematically studied,and the evolution of microstructure and properties of composites during rolling and annealing were also discussed.The in-situ growth mechanism of carbon on the surface of copper powder and the reinforcement mechanism of the composite were revealed.The main work and conclusions are as follows:（1）Multi-scale spherical copper powders were prepared by plasma technology,and the effects of process parameters on the properties of the powders were investigated.The optimal plasma process parameters are as follows:powder feed rate is 5.5 g/min,carrier gas flow rate is 5-6 L/min and reaction chamber pressure is 15 Psia.The formation mechanism of multi-scale spherical copper powder is as follows:when the copper powder passes through the plasma,a part of the copper powder is instantly vaporized at high temperature and grows into nano-scale powder through uniform nucleation;the other part undergoes rapid melting and surface vaporization.Then the molten droplets become spherical under the action of surface tension,and form micron-sized powder after solidification.（2）The carbon-coated copper composite powder was prepared by plasma.The effects of carbon source,particle size of raw copper powder and plasma process parameters on the properties of the composite powder were studied.CH₄ was selected as the carbon source,copper powder with a diameter of 400 mesh was selected as the substrate.The optimal plasma processing parameters are as follows:powder feed rate is 5.5 g/min,carrier gas flow rate is 6 L/min,reaction chamber pressure is 9 Psia.The formation mechanism of carbon-coated copper composite powder is as follows:the carbon source dehydrogenates into active carbon atoms,which are adsorbed on the substrate surface by copper matrix and agglomerate to form carbon clusters,and further form carbon nuclei and grow under the catalysis of copper.（3）C/Cu composites were prepared by powder metallurgy method.The effects of hot pressing,sintering,cold rolling and annealing on the microstructure and properties of the composites were investigated.The sintered composite material is equiaxed,and the carbon is uniformly intercalated at the copper grain boundary;the cold-rolled composite material has thin strip-like grains,and the carbon is thinned;the composite material has different degrees of recrystallization and growth at different annealing temperatures.The yield strength of the cold-rolled C/Cu composite is 400.5 MPa,the friction coefficient is 0.38,and the electrical conductivity is 98.3%IACS.Compared with pure copper under the same process,its strength is increased by 49.5%,the friction coefficient is reduced by 44.9%,and the conductivity is equivalent.The enhancement effect of fine grain reinforcement accounts for 58%of the total,which is the main strengthening mechanism.