Phase equilibria of precursor-derived Si-(B-)C-N ceramics

Phase equilibria and phase reactions of precursor-derived ceramics of the Si-C-N and the Si-B-C-N systems at temperatures higher than 1700 K are described. CALPHAD (CALculation of PHAse Diagrams) results confirm quantitatively the data from thermogravimetry and differential thermal analysis of precursor-derived Si-C-N ceramics. A model for explanation of the thermal stability of specific Si-B-C-N precursor ceramics was developed. Phase reactions of polymeric precursors of the Si-C-N-H system were calculated and compared with analyses concerning the composition of the solid ceramic and gaseous products from thermolysis at a temperature of 1323 K. The results show that a semi-quantitative description of the thermolysis process is possible. Copyright (C) 2001 John Wiley & Sons, Ltd.