2003 Volume 67 Issue 3 Pages 107-115
SiC matrix composites in which Si-M(=Ti, Zr)-C-O fiber is used as the reinforcing fiber are materials with superior heat capability and damage tolerance. It is known that the fiber’s oxidation and thermal decomposition characteristics have a significant influence on the durability of Si-M-C-O/SiC. We measured the weight change, oxide layer thickness, and crystallite size of Si-M-C-O fiber, and the X-ray absorption fine structure (XAFS) of Si-Zr-Cr-O fiber, when exposed in an ambient atmosphere and in a vacuum. We determined the thermal decomposition of the fiber exposed in an ambient atmosphere, and we analyzed the influence of the added metal elements (M=Ti, Zr) and the oxygen content on thermal decomposition based on the difference in thermal decomposition behavior due to the type of fiber and the exposure environment.
The results indicated that, when in a vacuum, the oxygen content of the fiber had a significant influence on the thermal decomposition of the Si-M-C-O fiber and the nucleation of ZrC in the Si-Zr-C-O fiber. On the other hand, when in the ambient atmosphere, in comparison with the behavior of ZrC in Si-Zr-C-O (1), TiC in Si-Ti-C-O (2) was formed at a lower temperature in a shorter time, indicating that resistance to thermal decomposition is greatly influenced by the type of metal added.
