Preparation And Electrical Contact Properties Of Cu-C Composites By Pyrolysis

Copper-carbon(Cu-C)composite material is an important electrical material.It has the advantages of wear resistance,welding resistance,and good chemical stability.It is used in high-speed train pantograph slides,electrical contacts for electrical switches,motor brushes,etc.It has a wide range of applications in important industrial fields.Such products are generally produced by powder metallurgy.However,due to the large difference in the density of Cu and C phases,it is difficult to uniformly disperse during the preparation process,causing the problems of agglomeration and segregation of C,which limits the Cu-C electrical contacts.Stability of service life and electrical contact performance.Some scholars use metal-plated carbon,resin-coated carbon and other means to improve the dispersion of C in the Cu matrix.Even though the above methods improve the bonding characteristics between Cu and C,the large density difference still makes C not dispersed.all.Other scholars use liquid phase polymer and copper powder to mix,through heat treatment to pyrolyze the polymer to obtain the target carbon residue,so as to obtain a uniformly dispersed carbon distribution.However,the carbon of polymer pyrolysis is amorphous carbon with many defects,and its conductivity is poor,which restricts its use as an electrical material.The low-temperature catalyzed graphitization of the polymer can significantly improve the graphitization degree of the resin pyrolytic carbon,which is combined with the preparation of the material,and the Cu-C composite material is prepared by the pyrolysis method.In this paper,phenolic resin with high carbon formation rate is selected as the carbon precursor,low-temperature graphitization catalyst(Ni)is introduced,the powder is mixed by the liquid coating method,and the pyrolysis method is used to prepare Cu-C with a dispersion of C and a high degree of graphitization.For composite materials,the structure,physical and mechanical properties and electrical contact properties of the composite materials are studied,and the effects of changes in carbon content,carbon graphitization degree and dispersibility on the structure and performance of Cu-C composite materials are analyzed.Using TG,FTIR,XRD and Raman to analyze the process of phenolic resin catalyzed pyrolytic graphitization,it was determined that the use of Ni catalyst can effectively improve the degree of graphitization and carbon formation rate of pyrolytic carbon,and it was found that the phenolic resin would release a large amount of phenolic resin during the pyrolysis process.Gas,developed 700 ℃ pyrolysis pretreatment,can effectively promote the material densification.Grind the mixed resin solution and copper powder to obtain a phenolic resin-coated copper composite powder,and then through the gradient initial pressure and recompression pressure research,the conventional process is optimized,and 80% dense Cu-C material is obtained;industrial By hot extrusion,a CuC composite material with a density of more than 94% was successfully prepared.By characterizing the C eluted from the Cu-2%C electrical contacts,it is proved that the liquid-phase coating pyrolysis method can realize the fine dispersion of C in the Cubased electrical contacts and improve the dispersibility of the Cu-C electrical contacts.And by comparing the conductivity test of the dissolved C,it is found that the dissolved C with added catalyst(Ni)has higher conductivity.The cyclic ablation performance test of Cu-C material is carried out.Compared with commercially available Cu-C,the electric contact made by liquid-phase coating pyrolysis method has a significant reduction in welding force due to the dispersion of carbon and the high degree of graphitization.Contact resistance and dynamic temperature rise are more stable.