The influence of carbon source and content on structure and mechanical properties of SiC processed via spark plasma sintering method

The effects of carbon sources and carbon content on the density, microstructure, hardness and elastic properties of dense SiC ceramics were investigated. The precursor powders were prepared by adding 1.5-4.5 wt.% C (carbon lamp black or phenolic resin) and 0.5 wt.% B4C to SiC and sintered at 1900 degrees C for 15min under 50MPa pressure in argon with an intermediate dwell at 1400 degrees C for 30min. The results showed that carbon lamp black provided better mixing than phenolic resin since carbon cluster was found in the samples made with phenolic resin. Increasing carbon content causes the decrease of 4H polytype amount in the samples. The presence of higher than 1.5wt.% carbon inhibits grain growth and the presence of the 4H polytype. SiC samples can be produced with relative density of more than 99%TD with 1.5 wt.% carbon lamp black addition which shows small average grain size, high elastic modulus and hardness of 2.28 mu m, 453GPa and 21.2GPa, respectively.