High temperature structure evolution of macroporous SiOC ceramics prepared by a sol-gel method

Macroporous SiOC ceramics have been prepared by the pyrolysis of the preceramic precursor obtained from methyltrimethoxysilane and dimethyldimethoxysilane. The structural evolution of the sol-gel derived SiOC ceramics at high temperatures was investigated using SEM, TG, FTIR, XRD and Raman spectra. The SiOC xerogel exhibited a porous structure consisting of cross-linked spherical gel particles. The structural rearrangement appeared and the SiOC ceramic particles changed from spherical to irregular shape after thermal pyrolysis. The ceramic yield was found to be approximately 70% until 1400 degrees C, and decreased to 38% at 1600 degrees C owing to carbothermal reduction. The SiC nanorods were in situ formed from macroporous SiOC ceramic wall at 1600 degrees C. The beta-SiC nanocrystals precipitated from the SiOC matrix at 1400 degrees C and grew up to 4.6 nm at 1600 degrees C. The graphitization degree of free carbon increased with the increase of pyrolysis temperature. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.