Enhanced thermal conductivity of copper/diamond composites by fine-regulating microstructure of interfacial tungsten buffer layer

In this paper, tungsten (W) coatings were deposited on surface of diamond particles by magnetron sputtering for fabricating copper/diamond composites with high thermal conductivity. To reveal the influence of interfacial microstructure on performance of the composites, the W coated diamond particles subjected different annealing process before the composites were fabricated via pressure-assisted infiltration. The evolution of interfacial microstructure and composition of the coating layer were studied. Thermal conductivity of the composites exhibited increasing firstly and decreasing subsequently with the interfacial phase transformed from metallic W to corresponding carbides. Compared with diamond/WC/Cu interfacial microstructure, constructing diamond/WC/W2C/Cu interfacial microstructure via fine regulation is a critical factor for the optimized thermal conductivity of the composites. When the interfacial coating layer was composed of WC phase (97.6 wt.%) and W2C phase (2.4 wt.%), the highest thermal conductivity of the composite reached to 836 W⋅m−1⋅K−1. Based on the theoretical calculation, the W2C sublayer in diamond/WC/W2C/Cu interfacial microstructure reduces the acoustic impedance mismatch between Cu and the carbide buffer layer, resulting in higher interfacial thermal conductance.