Surface modification of hard diamond particles with Cu-Mo2C double layer coating and its application in thermal conductive composites

Thermal conductive composites were fabricated with a unique method using Cu-Mo 2 C double layer coated diamond particles. Molybdenum carbide coating was prepared by the molten salt method to promote interfacial bonding in the composites. The reacting substance of MoO 3 and diamond surface was analyzed and the reacting process was clarified. With electroless plating, copper layer was deposited as the outer layer. The powder size distribution and pressing property of the synthetic particles were further analyzed, which confirmed that the copper layer was formable and thick enough to replace copper powders for the composite matrix. The Cu-Mo 2 C coated diamond particles were compacted by cold pressing and then sintered under vacuum. Thermal conductivity of 65 vol% diamond/Cu composite produced in this way reached 622 Wm −1 K −1 which was much higher than that of the composite using uncoated diamond. The coefficient of thermal expansion of 70 vol% diamond/Cu composite reached as low as 5.40 × 10 −6 /K which was more compatible with those of semiconductor materials. The significantly improved thermal physical properties can be ascribed to the perfect adhesion of Mo 2 C layer at the interface and the uniform distribution of diamond particles because of the coating copper layer. In addition, the nailing effect and grain refining mechanism of diamond particles during copper sintering were studied based on the phase field method. The results show that diamond can effectively inhibit the grain growth and promote the grain refining of copper matrix, which is a unique sintering phenomenon for double layer coated diamond powders. • Diamond particles were coated with Cu-Mo 2 C double layers using molten salt and electroless plating methods. • The powder size distribution and pressing property of the synthetic particles were further analyzed. • The outer copper layer was formable and thick enough to be compacted by cold pressing and then directly sintered under vacuum. • With the uniform distribution of diamond particles by double layer coating, thermal conductivity of 65 vol.% diamond/Cu composite reached 622 Wm -1 K -1 . • The sintering behaviors and nailing effect of the double layer coated diamond core-shell structure were studied using phase-field simulation.