Effect of processing parameters on the microstructure and thermal conductivity of diamond/Ag composites fabricated by spark plasma sintering

摘要

Diamond/metal composites with 50 vol.% diamond have been produced by spark plasma sintering(SPS) using pure Ag as a matrix and diamond particles as reinforcement.Three kinds of powder mixing processes were used to prepare the mixture of diamond/Ag powders:dry mixing without milling medium,wet mixing and magnetic blending.Subsequently,they were all consolidated by SPS at various processing parameters to produce bulk diamond/Ag composites.Then samples were heat treated in order to obtain a higher thermal conductivity.The effect of processing parameters on the morphologies of the mixed powders,the microstructure and the thermal conductivity of the composites were investigated by comparing the experimental data.It reveals that particles were easy to agglomerate and the distribution of mixed powders was inhomogeneous by dry mixing method,and wet mixing method is too complex.The most favorable mixing process is magnetic blending by which the powders can be homogenously mixed and the composites prepared by optimized SPS processing parameters can obtain the highest relative density and the best thermal conductivity among the composites prepared by different processes.The magnetic blending diamond/Ag composites even have a 23% increase in thermal conductivity compared with pure silver sintered by SPS.