Process for improving strength of SiC ceramics

Details Process for improving strength of SiC ceramics Process for improving strength of SiC ceramics

1988-03-04

1989-07-04

Dixon, Jr., William R.

Compositions: ceramic

Ceramic compositions

Carbide or oxycarbide containing

264 63, 264 65, C04B 3556

Patent

active

048450588

ABSTRACT:
The strength of SiC ceramic parts derived from certain preceramic compositions is improved by (A) cooling the parts in an inert atmosphere to a temperature at least as low as about 800.degree. C. after preparing them by molding and pyrolyzing the preceramic compositions, (B) then heating them in air to about 1200.degree.-1300.degree. C., and (C) keeping them in air at that temperature for at least about one hour before allowing them to cool. The preceramic compositions from which the ceramics are derived are mixtures of SiC powders and polysilazanes having an alkali metal content of 0-100 ppm and prepared by reacting an organodihalosilane with ammonia, treating the ammonolysis product with a basic catalyst which is capable of deprotonating an NH group that is adjacent to an SiH group, and quenching the resultant product with an electrophilic quenching reagent.

REFERENCES:
patent: 4117507 (1978-09-01), Yajima et al.
patent: 4482669 (1984-11-01), Seyferth et al.
patent: 4560526 (1985-12-01), Okumura
patent: 4645807 (1987-02-01), Seyferth et al.
patent: 4650837 (1987-03-01), Seyferth et al.
patent: 4659850 (1987-04-01), Arai et al.
Wiseman, "The Developement and Application of Polysilazane Precursors to Ceramics", M.I.T. Thesis, Aug. 1984.
Shin Nisso Kako Co., "SiC Products by PPMC Process", Specification Sheet.

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