Ceramic fibers silicon oxynitride

Practical interest in nitrides is mainly focussed in their use as tough ceramics such as sialons and interstitial nitride coatings on metals [368,369]. Silicon oxynitride glasses are of importance in fiber optics as their refractive indices depend on the nitrogen content. There are surely other interesting properties awaiting exploration. 

SiC fibers were produced using polycarbosilanes by Yajima et al. in 1975 [1,2]. Besides SiC fibers, Si-Ti-C-O fibers prepared from a polytitanocarbosi-lane have been obtained by adding a titanium tetrabutoxide to polycarbosilane or polysilane [3]. SiC fibers (Nicalon) and Si-Ti-C-O fibers (Tyranno) are manufactured on an industrial scale. Colorless silicon oxynitride fibers and silicon nitride fibers [4] have been obtained by the nitridation of polycarbosilanes in the author s laboratory. Polymers used for ceramic precursor and the resulting ceramic fibers are listed in Table 1. 

Okamura, K., M. Sato, and Y. Hasegawa. 1987. Silicon nitride fibers and silicon oxynitride fibers obtained by the nitridation of polycarbosilane. Ceramic International 13(1) 55-61. ... 

But CMCs will be commercially successful only when they are produced cost-effectively. Polymer-derived ceramic (PDC) technology is one of the most promising low cost fabrication methods for ceramic matrix composites, particularly for large, complex shapes. In PDC technology, a silicon-based polymer (siloxane, carbosilane, silazane, etc) with fiber or particle reinforcement is shaped and cured in the polymer condition and then pyrolyzed in a controlled atmosphere to form a stable silicon-based ceramic, such as silicon carbide, sihcon nitride, silicon oxycarbide, or silicon oxynitride. 

Sakka S., Kamiya K. The sol-gel transition in the hydrolysis of metal alkoxides in relation to the formation of glass fibers and films. J. Non-Ciyst. Solids 1982 48 31 16 Sakka S., Kamiya K., Makita K., Yamamoto Y. Formation of sheets and coating films from alkoxide solutions. J. Non-Cryst. Solids 1984 63 223-235 Sakka S., Yoko T., Fibers from gels. J. Non-Cryst. Solids 1992 147/148 394-403 Scholtz H., Sporn A., Ullrich A., Schoenecker A., Martin W. Fabrication and properties of sol-gel-derived PZT-fibers for 1-3 composites. Ceram. Trans. 1995 51 751-755 Sekine M., Katayama S., Mitomo M. Preparation of silicon oxynitride glass fibers by ammonolysis of silica gels. J. Non-Cryst. Solids 1991 134 199-207 Sowman H.G. Alumina-boria-silica ceramic fibers from the sol-gel process. In Sol-Gel Technology for Thin Films, Fibers, Preforms, Electronics, and Specialty Shapes, L.C. Klein, ed. Noyes Publication, 1988... 

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