Unveiling interfacial structure and improving thermal conductivity of Cu/diamond composites reinforced with Zr-coated diamond particles

To overcome the drawback of weak interface bonding in diamond particles reinforced Cu matrix (Cu/diamond) composites, we prepared the Cu/Zr-diamond composites via a gas pressure infiltration method with Zr coatings with thicknesses from 47 nm to 430 nm on diamond surfaces. The scanning transmission electron microscopy (STEM) and X-ray diffraction (XRD) analyses reveal that during preparation the gradual transformation of metallic Zr to ZrC occurs through the diffusion of C atoms, and the crystallographic orientation relationship between diamond and ZrC is characterized as (1¯11)diamond//(1¯11)ZrC and [110]diamond//[110]ZrC. The formed ZrC layer between diamond and Cu can bridge the large gap of acoustic impedance and greatly strengthen the interface bonding, and a maximal thermal conductivity of 735 W m−1 K−1 is achieved with the thickness of the interfacial ZrC layer of 50 nm (corresponding to Zr-coating thickness of 47 nm). However, with increasing the thickness of the interfacial ZrC layer, the composite thermal conductivity decreases attributed to the intrinsic low thermal conductivity of ZrC and the interface de-bonding with the large ZrC layer thickness. This study accurately establishes the relationship between interfacial structure and thermal conductivity and provides guidance for the interface design in Cu/diamond composites.