Diamond/SiC composites were prepared by vacuum silica vapor-phase infiltration of in situ silicon–carbon reaction, and the thermophysical properties of the composites were modulated by controlling diamond graphitizing. The effects of diamond surface state and vacuum silicon infiltration temperature on diamond graphitization were investigated, and the micromorphology, phase composition, and properties of the composites were observed and characterized. The results show that diamond pretreatment can reduce the probability of graphitizing; when the penetration temperature is greater than 1600 °C, the diamond undergoes a graphitizing phase transition and the micro-morphology presents a lamellar shape. The thermal conductivity, density, and flexural strength of the composites increased and then decreased with the increase of penetration temperature in the experimentally designed range of penetration temperature. The variation of thermal expansion coefficients of composites prepared with different penetration temperatures ranged from 0.8 to 3.0 ppm/K when the temperature was between 50 and 400 °C.

This article reported a simple method for preparing diamond/SiC composites by polymer impregnation and pyrolysis (PIP) process, and the advantages of this method were discussed. Only diamond and SiC were contained in the diamond/SiC composite prepared by PIP process, and the diamond particles remained thermally stable up until the pyrolysis temperature was increased to 1600 °C. The pyrolysis temperature has a significant impact on the thermal conductivity and dielectric properties of composites. The thermal conductivity of the composite reaches a maximum value of 63.9 W/mK when the pyrolysis temperature is 1600 °C, and the minimum values of the real and imaginary part of the complex permittivity are 19.5 and 0.77, respectively. The PIP process is a quick and easy method to prepare diamond/SiC composites without needing expensive equipment, and it is of importance for promoting its application in the field of electric packaging substrate.

Diamond reinforced silicon carbide matrix composites (diamond/SiC) with high thermal conductivity were prepared by tape casting combined with Si vapor infiltration for thermal management application. The effects of the mixing mode of bimodal diamond particles on the microstructure, thermal and mechanical properties of the composites were analyzed. The results reveal that the thermal conductivity of composites is affected significantly by mixing mode of diamond. In general, when the content of large diamond remains constant, adding a slight amount of small diamond was found to be effective in improving the thermal conductivity of the composite. However, excess small diamonds added will decrease thermal conductivity due to its high interfacial thermal resistance. The maximum thermal conductivity of obtained diamond/SiC is 469 W/(m K) when 38 vol% large diamond and 4 vol% small diamond were added. Such a result can be attributed to the formation of efficient heat transfer channels within the composite and sound interfacial bonding between diamond and SiC phase. Diamond/SiC with high thermal conductivity are expected to be the next generation of electronic packaging substrate.