Thermal conducting mechanisms in tungsten-coated diamond/copper composites

Diamond/copper composites are recently explored extensively for their exceptional thermal conductivity and low coefficient of thermal expansion. However, there are significant challenges because of poor interfacial wettability and phonon mismatch between diamond and copper matrix, which contribute to high interfacial thermal resistance and a significant discrepancy between the actual and theoretical thermal conductivity of these composites. To tackle these issues, this study employed a salt bath plating technique to deposit a tungsten layer on diamond surfaces, and then diamond/copper composites were fabricated using spark plasma sintering. Results showed that an in-situ reaction occurred at the interface between the tungsten coating and diamond, forming a tungsten carbide transition layer, which effectively reduces interfacial thermal resistance and suppresses diamond graphitization during high-temperature sintering. The synthesized diamond/copper composite achieved a maximum relative density of 97.7 %, a thermal conductivity of 611.92 W/(m·K), and a coefficient of thermal expansion of 7.24 × 10⁻⁶ K⁻¹. The good thermal conduction in the diamond/copper composites is attributed to the improved interfacial bonding, enhanced electron conduction in the copper matrix, minimized energy dissipation and enhanced phonon conduction, and improved interfacial heat transfer.