Improvement of Si-Ti(Zir)-C-O Fiber and a Precursor Polymer for High Temperature CMC

Abstract

Sl-Ti-C-O fibers with 13 and 5-6 wt % oxygen content, which had double layer-gradient structures and a special gradient structure near the surface, respectively, TM-S6 and TE-S6, were developed for CMCs' application. SIC/SITIC or SiTiC matrix comosites using 3-D fabrics of TM-S6 or TE-S6 with no surface treatment were fabricated by the CVI and/or PIP (polymer impregnation and pyrolysis) methods. The obtained CMCs had higher mechanical properties and more excellent heat-resistance in air above 1473 Kthan ordinary Si-Ti-C-O fibers. Fiber-bonded ceramics (Tyrannohex, Vf:9096) obtained by hot-pressing UD sheets or 2-D fabrics of Si-Ti-C-O fibers with 13 wt % of the oxygen content, furthermore, kept their strength up to 1773 K in air and showed good creep characteristics at 1673 K in air. Si-Ti-C-O fibers with near-stoichiometric C/Si ratio and Si-Zr-C-O fiber with 3 wt % oxygen content were also synthesized by changing the pyrolysis process and the structure of the precursor polymer in order to still further improve oxidative heat-resistance and creep characteristics.