Preparation and Thermal Stability of SiOC Ceramics by Flash Sintering

By taking the cross-linked polysiloxane as precursor, SiOC ceramics were prepared by flash sintering at different temperatures (730-780℃), applied electric field intensities (20-60 V·mm^-1) and limiting currents (0.5-2.0 A), and the suitable process parameters were obtained. The microstructure, physical properties and thermal stability of the ceramics were studied. The results show that the temperature range for successfully preparing SiOC ceramics was 740-780℃, the limiting current range was 1.0-2.0 A, and the applied electric field intensity range was 30-60 V·mm^-1; the test temperature was 660-620℃ lower than the traditional pyrolysis temperature (1 400℃), and the pyrolysis time was greatly shortened. As the applied electric field intensity, test temperature or limiting current increased, the SiC content in the ceramics increased, the SiO₂ content decreased, the ceramic yield and bulk density decreased, and the linear change rate and apparent porosity increased. Compared with that of the traditional pyrolyzed SiOC ceramics at 1 400℃, the thermal stability temperature of flash-sintered SiOC ceramics increased by about 112℃, and with increasing applied electric field intensity, test temperature or limiting current, the thermal stability improved.