Quantitative control of interfacial structure and thermal conductivity between diamond and copper via thermal diffusion of alloying element

The thermal property of diamond/metal composites mainly depends on the chemical bonding and structure of interfacial layers between two heterogeneous materials. To improve the thermal property of the diamond/metal composites, a metallic carbide layer that bridging both crystal structure and thermal transport of heterogeneous interfaces is required, though the formation mechanism of such carbide interfaces during powder sintering remains under debate, particularly for the scenario of varying thermal diffusion. Here, systematic experiments of diamond/Cu-Cr composites have been conducted to unravel the effects of two important variables for thermal diffusion, temperature (800-1025 degrees C) and holding time (5-60 min), on the growth of chromium carbide interfaces and the resulting thermal conductivity. It is found that the main characteristics of chromium carbide layer is more related to the holding time, that is, prolonged thermal diffusion. The extraction of diamonds in assintered composites allows a detailed quantification of coating efficiency and crystallographic-facet-dependence of chromium carbide interfaces during diamond/metal reaction at varying temperature and holding times. It is found that the prolonged thermal diffusion is not as expected to deteriorate the thermal conductivity, and leads to a more densified structure with highest thermal conductivity instead (similar to 577 W/(m.K)). Furthermore, thermal diffusion of diamond/metal reaction is discussed based on theoretical models. We theoretically demonstrate that long thermal diffusion could enhance the thermal diffusivity for the composites and achieve similar to 90.8% of theoretical thermal conductivity predicted by the Maxwell-Eucken model.