Abstract: The current invention provides a method to fabricate a crack-free continuous fiber-reinforced ceramic matrix composite by eliminating shrinkage stresses through a unique combination of freeze forming and a non-shrinking matrix composition. Cracks related to drying shrinkage are eliminated through freeze forming and cracks related to sintering shrinkage are eliminated by using a matrix that does not shrink at the given sintering temperature. After sintering, a crack-free ceramic composite is obtained.

Abstract: Lasing systems utilizing YAG and methods for producing a YAG suitable for lasing are provided. The lasing system comprises a laser activator and a laser host material is provided. The laser host material comprises a transparent polycrystalline yttrium aluminum garnet material defined by a low porosity of less than about 3 ppm.

Abstract: Coated alloys and methods of making coated alloy are provided. The coated alloy comprises a superalloy substrate, a bond coat comprising a metallic alloy disposed on the superalloy substrate, an oxidation barrier coating comprising yttrium aluminum garnet (YAG) disposed on the bond coat, and a top coat defining the outermost layer disposed on the oxidation barrier coating.

Abstract: Methods of producing doped and undoped yttrium aluminum garnet and yttrium aluminum perovskite containing powders and the powders produced thereby are provided. Additionally, methods of forming doped and undoped polycrystalline yttrium aluminum garnet having a mean grain size of between about 1 ?m to about 3 ?m and the yttrium aluminum garnet produced thereby are provided. The doped and undoped polycrystalline yttrium aluminum garnet may be formed by sintering a compact and subsequently hot isostatically pressing the compact.

Abstract: Lasing systems utilizing YAG and methods for producing a YAG suitable for lasing are provided. The lasing system comprises a laser activator and a laser host material is provided. The laser host material comprises a transparent polycrystalline yttrium aluminum garnet material defined by a low porosity of less than about 3 ppm.

Abstract: A reinforcing material is uniformly dispersed in a yttrium aluminum garnet matrix material for use as a machine tool material specially suited for machining Ti or a Ti alloy. The matrix material and the reinforcing material are present in proportions selected such that the machine tool material is substantially resistant to transfer of impurities to a Ti or Ti alloy by way of either chemical reaction with or diffusion into the Ti or Ti alloy material to be machined. The matrix material preferably comprises Y3Al5O12. The reinforcing material may comprise SiCw, TiC, TiN, TiB2, or combinations thereof and is preferably present in an amount sufficient to enable electrical discharge machining of the machine tool material. In addition, the machine tool material defines a thermodynamically stable phase at relatively high machining temperatures.

Abstract: Dense silicon nitride bodies are fabricated using conventional hot-pressing techniques using cerium oxide as a densification aid. The bodies are then further treated in a flowing inert atmosphere at a temperature of from 1400.degree.-1600.degree. C. for from several hours to 48 hours to remove all or substantially all of the densification aid from grain boundaries. Silicon nitride bodies so treated exhibit superior elevated temperature slow crack growth resistance and strength properties and are suitable for use as structural components in high temperature environments such as jet and internal combustion engines, rockets, atomic power generation, and the like.