Comparison of the creep behavior of silicon carbide fibers
- Pennsylvania State Univ., University Park, PA (United States)
Silicon carbide based fibers have been developed for use in ceramic matrix composites at high temperatures (> 1300{degrees}C). The principal manufacturing routes for the SiC fibers are pyrolysis from polycarbosilane based precursors, sintering of submicron powders, and chemical vapor deposition. These fabrication routes lead to distinctly different microstructures. The pyrolysis of polycarbosilane route produces fibers with nanocrystalline {beta}-SiC grains embedded in a Si-O-C amorphous phase (Nicalon) or {beta}-SiC grains (2-15 nm) embedded in turbostratic carbon (Hi Nicalon). For the Hi Nicalon fiber, heat treatments at creep temperatures yield larger grain sizes and reorganization of the free carbon phase. The sintered material contains {alpha}-SiC grains of average diameter 1.7 {mu}m with carbon at some triple grain junctions and intragranular B{sub 4}C precipitates after heat treatment or creep testing at 1400{degrees}C. No change in grain size was apparent after heat treatment. The CVD fibers have a range of microstructures; the one of most interest for CMC reinforcement is a 50 {mu}m diameter fiber with columnar {beta}-SiC grains with width 170 nm and length 1800 nm. The grains grow during creep testing and transform to {alpha}-SiC grains much larger than the starting {beta}-SiC grain size.
- OSTI ID:
- 530668
- Report Number(s):
- CONF-9604124-; CNN: Grant NAGW-1381; TRN: 97:003389-0004
- Resource Relation:
- Conference: 98. annual meeting of the American Ceramic Society, Indianapolis, IN (United States), 14-17 Apr 1996; Other Information: PBD: 1996; Related Information: Is Part Of Ceramic transactions: Advances in ceramic-matrix composites III. Volume 74; Bansal, N.P.; Singh, J.P. [eds.]; PB: 667 p.
- Country of Publication:
- United States
- Language:
- English
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