Microstructure and Properties of Diamond/SiC Composites Via Hot Molding Forming and CVI Densifying

In order to improve the mechanical properties and thermal conductivity, diamond/SiC composites are fabricated using hot molding forming and chemical vapor infiltration (CVI) densifying. The effects of diamond particle size and grain gradation (maximum particle size of 50-500 mu m) on microstructure, mechanical properties, and thermophysical properties of diamond/SiC composites are investigated. The results indicate that the thermal conductivity of composites can be obviously enhanced and the maximum value is 257 W center dot m(-1) center dot K-1 using large diamond particle size and grain gradation. The value is 2.22 times higher than that of the diamond/SiC composites prepared using tape-casting and CVI process (116 W center dot m(-1) center dot K-1). The maximal density, flexural strength, and fracture toughness are found to be 3.16 g cm(-3), 248.33 MPa, and 4.65 MPa(.)m(1/2), respectively. The fracture mechanism of the composites is transferred from diamond particles' trans-granular fracture to interfacial debonding due to stronger combination between the diamond and the CVI-SiC matrix. Furthermore, JD50 sample has the highest flexural strength (248.33 MPa), fracture toughness (4.65 MPa center dot m(1/2)), and equivalent CTE (4.0 x 10(-6) K-1) compared with other samples. Additionally, its thermal conductivity is also relatively high, making it a suitable high thermal conductivity material.