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 63.4vol.%) 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 63.4vol.%) could reach up to 431MPa, 4.8MPam^1/2, HRA 98.6 (high than HV 50GPa), and 116W/(mK), 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).