Gradient interface formation in Cu–Cr/diamond(Ti) composites prepared by gas pressure infiltration

Interface design is critical to enhance thermal properties of Cu/diamond composite as a promising thermal management material. Herein we combine Cr alloying in Cu matrix with Ti coating on diamond particles to prepare a Cu-0.5 wt%Cr/diamond(Ti) composite in an attempt to construct a TiC/Cr3C2 gradient interface to improve phonon transfer at the interface. The Ti-coating on diamond particles transforms to a TiC layer during deposition. As the TiC layer is 20 nm thick, a part of Cr atoms in the Cu matrix diffuse through the TiC layer to react with the C atoms on diamond particles to form a 30 nm-thick Cr3C2 layer, and a 28 nm-thick graphite layer is generated on diamond particle surface. With increasing the TiC layer thickness to 80 nm, a small part of Cr atoms can still pass through the TiC layer to form discrete chromium carbide particles and a 20 nm-thick graphite layer is generated. The interfacial structure of the Cu-0.5 wt%Cr/diamond(Ti) composite is characterized as diamond/graphite/TiC/Cr3C2/Cu, and the thermal conductivity for the Cu-0.5 wt%Cr/diamond(Ti) composite has a 549 W m−1 K−1 value lower than the 735 W m−1 K−1 value for the Cu/diamond(Ti) composite. The lowered thermal conductivity is attributed to the formed graphite layer and the thick Cr3C2 layer in the Cu–Cr/diamond(Ti) composite. This study provides guidance for designing and tailoring gradient interface for efficient phonon transport in Cu/diamond composites.