Effect of Si-coated diamond on the relative density and thermal conductivity of diamond/W composites prepared by SPS

In order to improve the thermal conductivity of tungsten, diamonds coated with thin coating of pure Si and W matrix were mixed to fabricate composites with SPS process. The effects of Si coating and volume fraction of diamonds on microstructure including interfacial structure, relative density and thermal conductivity of the composites were investigated with scanning electron microscopy, X-ray diffraction, transmission electron microscopy and laser thermal conductivity instrument. The results showed that the interface bonding, relative density and thermal conductivity of coated-diamond/W composites were improved compared with uncoateddiamond/W composites under the same volume fraction of diamonds. Increasing in volume fraction of coated diamonds from 30% to 60%, the relative density and thermal conductivity of coated-diamond/W composite increased. Under the combined action of reaction diffusion and inter-diffusion at the interfaces of diamond-Si and diamond-W, the 60 vol% coated-diamond/W composite achieved the maximum thermal conductivity of 193 +/- 2.12 W m-1 K-1, which was expected to be used for a longer time than that of W under 20 MW/m2 heat load. Its thermal conductivity was increased with the addition of Si-coated diamond compared with pure W sample (121 +/- 1.06 W m-1 K-1) prepared via SPS.