Liquid phase sintering of silicon carbide
AssigneeCeramatec, Inc.
InventorsRaymond A. Cutler, Anil V. Virkar, Andrew C. Hurford
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Abstract
Liquid phase sintering is used to densify silicon carbide based ceramics using a compound comprising a rare earth oxide and aluminum oxide to form liquids at temperatures in excess of 1600.degree. C. The resulting sintered ceramic body has a density greater than 95% of its theoretical density and hardness in excess of 23 GPa. Boron and carbon are not needed to promote densification and silicon carbide powder with an average particle size of greater than one micron can be densified via the liquid phase process. The sintered ceramic bodies made by the present invention are fine grained and have secondary phases resulting from the liquid phase.
Claims17
A process for liquid phase sintering of silicon carbide comprising:
- forming a mixture consisting essentially of silicon carbide particles having a size of from about 2 to about 5 microns and from about 0.5 percent to about 19.5 percent by weight of a rare earth oxide and from about 0.5 percent to about 19.5 percent by weight alumina;
- forming a shape with said mixture;
- and
- sintering said mixture at a temperature of from about 1700.degree. to about 2200.degree. centrigrade for about 1 minute to about 30 minutes to form a liuqid phase and a resultant sintered ceramic body having a hardness exceeding about 22 GPa comprising 2% to 20% by weight of a compound wherein the molar ratio of rare earth oxide to alumina in said compound is at least three to five and from about 80% to about 98% by weight silicon carbide.
A sintered ceramic body comprising a uniform mixture of:
- from about 80% to about 98% by weight silicon carbide, and from about 2% to about 23% by weight of a compound, said compound comprising:
- alumina, and a rare earth oxide, wherein the molar ratio of rare earth oxide to alumina in said compound is at least three to five, and wherein said sintered ceramic body has a density greater than 95% of theoretical, and a hardness greater than 20 GPa.
Dependencies are inferred from the claim text.