Effect of diamond content on microstructure and properties of diamond/SiC composites prepared by tape-casting and CVI process

Diamond particles enhanced SiC composites (diamond/SiC) have been prepared by tape-casting and chemical vapor infiltration (CVI) process. The effect of diamond content (ranging from 50.0 to 63.4 vol.%) on microstructure, density, flexural strength, fracture toughness, hardness, thermal conductivity (TC) and coefficient of thermal expansion (CTE) of diamond/SiC composites is discussed. With the increasing diamond content in composites, the flexural strength, fracture toughness, surface hardness, and TC all increased, which of sample S4 (with diamond content 63.4 vol.%) could reach up to 431 MPa, 4.8 MPa m1/2, HRA 98.6 (high than HV 50 GPa), and 116 W/(m K), respectively. The TEM images present a close interfacial combination between diamond and CVI-SiC matrix, and the diamond particle is confirmed to be under compress stress via Raman microspectroscopy technique. Besides, the TC of CVI diamond/SiC composites could be more accurately estimated by a modified model, which is Maxwell 2-EMT (effective medium theory).