Silicon nitride ceramics containing crystallized grain boundary phases
OwnerRoger L. K. Matsumotoinventor
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Abstract
A silicon nitride ceramic having crystalline grain boundary phases is prepared by heating a composition comprising silicon nitride, a silicate glass-forming sintering aid and a high metal content transition metal silicide, to a temperature of 1300.degree. to 1800.degree. C. under vacuum until a glass forms, oxygen is removed from the glass, and the glass crystallizes. Alternatively, the grain boundaries of a sintered composition comprising silicon nitride, a silicate glass and a high metal content transition metal silicide can be crystallized by heating to at least 1300.degree. C. under a vacuum.
Claims21
A product prepared by the process comprising heating a composition comprising (1) from about 20% to about 98% silicon nitride, (2) from about 0.5% to about 20% of a silicate glass-forming sintering aid, and (3) from about 0.001% to about 80% of a high metal content transition metal silicide, all percentages being by weight based on the total weight of the composition, to a temperature of about 1300.degree. C. to about 1800.degree. C. under vacuum until silicate glass forms, oxygen is removed from the silicate glass as SiO gas, and the glass crystallizes.
A product prepared by the process comprising heating a composition comprising (1) from about 20% to about 98% silicon nitride, (2) from about 0.5% to about 20% of a silicate glass-forming sintering aid, and (3) from about 0.001% to about 80% of a high metal content transition metal silicide, all percentages being by weight based on the total weight of the composition, to a temperature of about 1300.degree. C. to about 1800.degree. C. under vacuum until silicate glass forms, oxygen is removed from the silicate glass as SiO gas, the composition densifies, and the glass crystallizes.
A product produced by the process comprising heating a sintered composition comprising (1) from about 20% to about 98% silicon nitride, (2) from about 0.5% to about 20% of a silicate glass, and (3) from about 0.001% to about 80% of a high metal content transition metal silicide, all percentages being by weight based on the total weight of the composition, to a temperature of at least about 1300.degree. C. under vacuum until oxygen is removed from the silicate glass as SiO gas and the glass crystallizes.
A product produced by the process comprising heating a sintered composition comprising (1) from about 20% to about 98% silicon nitride, (2) from about 0.5% to about 20% of a silicate glass, and (3) from about 0.001% to about 80% of a high metal content transition metal silicide, all percentages being by weight based on the total weight of the composition, to a temperature of between about 1300.degree. C. to about 1800.degree. C. in a non-oxidizing atmosphere until the sintered ceramic densifies, and then further heating at a temperature of at least about 1300.degree. C. under vacuum until oxygen is removed from the silicate glass as SiO gas and the glass crystallizes.
A product prepared by the process comprising heating a composition comprising (1) from about 20% to about 98% silicon nitride, (2) from about 0.5% to about 60% of a silicate glass-forming sintering aid, and (3) from about 0.001% to about 40% of a transition metal, all percentages being by weight based on the total weight of the composition, to a temperature of 1300.degree. C. to 1800.degree. C. under vacuum until silicate glass forms, oxygen is removed from the silicate glass as SiO gas, and the glass crystallizes.
Dependencies are inferred from the claim text.