Process for producing dense ceramic product
AssigneeCommonwealth Scientific and Industrial Research Organisation
InventorsMark Brian Trigg, Chull Hee Oh, Nick Rigopoulos
Life of this patent
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Abstract
A process for the production of dense polycrystalline silicon carbide shaped articles, includes the steps: (a) heating a powder compact containing silicon carbide and alumina or a precursor thereof together with a secondary sintering assist, to an intermediate temperature for an extended dwell, and then (b) heating the product of step (a) to a higher temperature for sufficient time to produce a dense polycrystalline silicon carbide product. The secondary sintering assist includes one or more rare earths or their precursors, for example scandia, yttria or dysprosia.
Claims29
A process for the production of a dense polycrystalline silicon carbide shaped article, characterized in that the process includes the following steps:
- (a)(i) forming a powder compact containing silicon carbide, a secondary sintering assist and alumina or a precursor of alumina but excluding boron or boron containing compounds;
- (a)(ii) heating the powder compact containing a secondary sintering assist, in an inert atmosphere, to a temperature ranging between 1400.degree. and 1650.degree. C.;
- (b) maintaining the powder compact in the temperature range between 1400.degree. and 1650.degree. C. in an inert atmosphere for at least 30 minutes and thereafter for a time sufficient to remove unstable species which adversely affect the densification of the compact;
- and
- (c) heating the product of step (b) to a temperature above 1900.degree. C. in an atmosphere comprising carbon monoxide for at least 60 minutes, and thereafter for a time sufficient to produce a dense polycrystalline silicon carbide product
- wherein the secondary sintering assist comprises at least one of scandium or an oxide thereof, yttrium or an oxide thereof, rare earths, zirconium or an oxide thereof, hafnium or an oxide thereof, thorium or an oxide thereof.
A process for the production of a dense polycrystalline silicon carbide shaped article, characterized in that the process includes the following steps:
- (a)(i) forming a powder compact containing silicon carbide, alumina or a precursor of alumina and a sintering assist;
- (a)(ii) heating the powder compact, in an inert atmosphere, to a temperature ranging between 1600.degree. and 1900.degree. C.;
- (b) maintaining the powder compact in the temperature range between 1600.degree. and 1900.degree. C. in an atmosphere comprising carbon monoxide, the powder compact being maintained in the temperature range for at least 30 minutes and thereafter for a time sufficient to remove unstable species which adversely affect the densification of the compact;
- and
- (c) heating the product of step (b) to a temperature above 1900.degree. C. in an atmosphere comprising carbon monoxide for at least 60 minutes, and thereafter for a time sufficient to produce a dense polycrystalline silicon carbide product
- wherein the sintering assist comprises at least one of scandium or an oxide thereof, yttrium or an oxide thereof, rare earths, zirconium or an oxide thereof, hafnium or an oxide thereof, thorium or an oxide thereof.
A process for the production of a dense polycrystalline silicon carbide shaped article, characterized in that the process includes the following steps:
- (a)(i) forming a powder compact containing silicon carbide, alumina or a precursor of alumina and a sintering assist;
- (a)(ii) heating the powder compact to a temperature between 1400.degree. and 1650.degree. C.;
- (b) maintaining the powder compact in the temperature range between 1400.degree. and 1650.degree. C. in a vacuum, the powder compact being maintained in the temperature range for at least 30 minutes and thereafter for a time sufficient to remove unstable species which adversely affect the densification of the compact;
- and
- (c) heating the product of step (b) to a temperature above 1900.degree. C. in an atmosphere comprising carbon monoxide for at least 60 minutes, and thereafter for a time sufficient to produce a dense polycrystalline silicon carbide product
- wherein the sintering assist comprises at least one of scandium or an oxide thereof, yttrium or an oxide thereof, rare earths, zirconium or an oxide thereof, hafnium or an oxide thereof, thorium or an oxide thereof.
Dependencies are inferred from the claim text.