Synthesis, morphological and structural properties of bio-SiC ceramics

Biomorphic SiC ceramics prepared by forced infiltration with liquid silicon of carbon matrixes derived from hardwood precursors were investigated. Phase composition of obtained ceramics was found to depend on the mass ratio of the initial silicon and carbon components, synthesis temperature and duration. Raman spectroscopy investigation shows that 3C polytype is formed at synthesis temperature similar to 1550 degrees C, and both 3C and 6H SiC are formed at temperatures up to 1800 degrees C. Further temperature rise up to 2100 degrees C increases the fraction of 6H polytype. The study of Raman scattering also revealed the presence of residual silicon inside SiC pores. Analysis of the parameters of phonon peaks allowed us to assume that the residual silicon is under significant compressive strain. The use of surface enhancement effect of Raman scattering allowed to detect residual carbon clusters in bio-SiC.