Compositions: ceramic – Ceramic compositions – Carbide or oxycarbide containing
Patent
1989-12-01
1991-02-19
Group, Karl
Compositions: ceramic
Ceramic compositions
Carbide or oxycarbide containing
501 89, 501 91, 501 92, 501 95, 427215, 427227, 427228, 427229, 264 65, C04B 3556
Patent
active
049944169
ABSTRACT:
Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.
REFERENCES:
patent: Re32843 (1989-01-01), Wei
patent: 4194914 (1980-03-01), Moriya et al.
patent: 4340636 (1982-07-01), De Bolt et al.
patent: 4543345 (1985-09-01), Wei
patent: 4642271 (1987-02-01), Rice
patent: 4652413 (1987-03-01), Tiegs
patent: 4657877 (1987-04-01), Becher et al.
Lindemer Terrence B.
Tiegs Terry N.
Griffin J. D.
Group Karl
Martin Marietta Energy Systems Inc.
Winchell Bruce M.
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