Achieving excellent thermal transport in diamond/Cu composites by breaking bonding strength-heat transfer trade-off dilemma at the interface

The heat transport enhancement of diamond/Cu composites, a new generation of thermal management materials, is trapped in the bonding strength-heat transfer trade-off dilemma at the interface due to the noticeable difference in physical and chemical properties between Cu and diamond. Herein, we propose a new strategy combining ultrathin interface modification and low-temperature high-pressure (LTHP) sintering process to prepare the diamond/Cu composites. With a suitable coefficient of thermal expansion (CTE) of <10 ppm/K, the obtained diamond/Cu composites exhibit an outstanding thermal conductivity (k) value of 763 W/m K, over 90 % of the theoretical prediction of the differential effective medium (DEM) model. Meanwhile, using a lower diamond volume fraction (45 % vs. 50%–70 %), the k value is higher than those by conventional powder metallurgy, meaning a substantial reduction in the cost by reducing diamond filler content. For such a highly mismatched diamond/Cu interface, we maintain a high bonding strength by lowering the thermal stress damage while achieve a high thermal conductance (G) of 93.5 MW/m² K by minimizing the heat transfer obstacles. The prepared interface structure is a diamond/TiC/CuTi₂/Cu configuration, where the two possible heat transfer bottlenecks (the diamond/TiC interface and the TiC/CuTi₂ interlayer) are no longer limiting factors on the overall interface. The successful resolution to the interfacial heat transfer problem is responsible for the superior thermal transport performance of the composites. This work deals with the critical challenge for the diamond/Cu composites and offers deep insight into the improvement mechanisms of thermal transfer. The proposed strategy can be generalized to the integration of highly mismatched interfaces widely present in other composites or thermal management systems.