Abstract: A method of manufacturing a coated reinforcing fiber for use in Ceramic Matrix Composites, the method comprising pre-oxidizing a plurality of silicon-based fibers selected from the group consisting of silicon carbide (SiC) fibers, silicon nitride (Si3N4) fibers, SiCO fibers, SiCN fibers, SiCNO fibers, and SiBCN fibers at between 700 to 1300 degrees Celsius in an oxidizing atmosphere to form a silica surface layer on the plurality of silicon-based fibers, forming a plurality of pre-oxidized fibers; applying a rare earth orthophosphate (REPO4) coating to the plurality of pre-oxidized fibers; and heating the plurality of REPO4 coated pre-oxidized fibers at about 1000-1500 degrees Celsius in an inert atmosphere to react the REPO4 with the silica surface layer to form a rare earth silicate or disilicate. The pre-oxidizing step may be 0.5 hours to about 100 hours. The heating step may be about 5 minutes to about 100 hours.

Abstract: A method of manufacturing a coated reinforcing fiber for use in Ceramic Matrix Composites, the method comprising pre-oxidizing a plurality of silicon-based fibers selected from the group consisting of silicon carbide (SiC) fibers, silicon nitride (Si3N4) fibers, SiCO fibers, SiCN fibers, SiCNO fibers, and SiBCN fibers at between 700 to 1300 degrees Celsius in an oxidizing atmosphere to form a silica surface layer on the plurality of silicon-based fibers, forming a plurality of pre-oxidized fibers; applying a rare earth orthophosphate (REPO4) coating to the plurality of pre-oxidized fibers; and heating the plurality of REPO4 coated pre-oxidized fibers at about 1000-1500 degrees Celsius in an inert atmosphere to react the REPO4 with the silica surface layer to form a rare earth silicate or disilicate. The pre-oxidizing step may be 0.5 hours to about 100 hours. The heating step may be about 5 minutes to about 100 hours.

Abstract: The present invention provides a thermal history sensor having a plurality of substrates positioned adjacent to an item. The substrates include different compositions, such that the substrates respond to thermal exposures with different changes in electrical conductivity or magnetic permeability. By measuring the electrical or magnetic properties of the substrates following thermal exposure, information about the thermal history may be obtained.

Abstract: A planar two material structure comprising a first material having a coefficient of thermal expansion greater than zero and a second material having a second coefficient of thermal expansion greater than zero. The two materials structurally combined in a plurality of repetitive for or six sided unit cells having a combined coefficient of thermal expansion less than the coefficient of thermal expansion of either material alone.

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: An improved method for coating ceramic fibers and woven cloths of ceramic fibers is disclosed, wherein the ceramic fibers are thoroughly wetted with precursors in a solution before the precursors react to form a coating by heterogeneous nucleation and growth. The fibers are then rinsed and fired and, where desired, the process may be repeated in stages to increase the coating thickness as desired. This method is amenable to operation in both the batch and continuous modes. This flexible method reduces both the cost and time of producing ceramic matrix composites (CMCs).

Abstract: A fiber-reinforced metal-ceramic composite material having a hot ceramic side and a cool metal side and a graded ceramic-metal zone therebetween, wherein the ceramic content of said composite ranges from 100% at said hot ceramic side to 0% at said cool metal side and the metal content of said composite ranges from 0% at said hot ceramic side to 100% at said cool metal side, and wherein said fiber reinforcement is graded by coefficient of thermal expansion from the hot ceramic side to the cool metal side.

Abstract: An improved thermal history sensor having multiple polymeric substrates with unique compositions is disclosed. By positioning the sensor adjacent to an item subject to thermal stressors, each of the polymeric substrates react with a different rate of crystallization and thus yield a specific measure of infrared (IR) absorption spectra, for example. By comparing these measurements for each polymeric substrate, a thermal history fingerprint may be obtained. This thermal history fingerprint may then be compared to baseline data to yield information about the item, such as the expected remaining useful lifetime of the item.

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: An improved thermal history sensor having multiple glass ceramic substrates with unique compositions is disclosed. By positioning the sensor adjacent to a component subject to thermal stressors, each of the glass ceramic substrates react with a different rate of nucleation and crystal growth and thus yield a specific measure of opacity. By comparing these values representing the opacity for each glass ceramic substrate, or thermal history fingerprint, to baseline data, information about the expected remaining useful lifetime of the component may be obtained.

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 &mgr;m to about 3 &mgr;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: 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: 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: A method for enhancing the oxidation resistance of substrates fabricated from metallic molybdenum and alloys containing at least 50% molybdenum which comprises depositing silicon on the surface of the substrate under conditions which cause the formation of an outer layer of MoSi2. Also disclosed is a method for enhancing the oxidation resistance of other substrates, such as carbon-carbon and metals and alloys which show minimal reaction with molybdenum under the coating conditions, which comprises depositing a layer of molybdenum on the surface, then depositing silicon on the molybdenum layer under conditions which cause the formation of an outer layer of MoSi2.

Abstract: A thermal gradient resistant fiber-reinforced composite structure which has a hot operating side and an opposite cool operating side and a thickness &tgr; therebetween. In one embodiment, the composite has two regions: hot and cool. The hot region consists essentially of a fiber having a first coefficient of thermal expansion and a matrix material and the cool region consists essentially of a fiber having a second coefficient of thermal expansion and a matrix material. In this embodiment, the hot region has a thickness &tgr;H of about 10 to 90 percent of the total thickness &tgr; between the hot side and the cool side, and the cool region has a thickness &tgr;C of about 90 to 10 percent of the total thickness &tgr;. In a second embodiment, the composite has a hot operating side and an opposite cool operating side and a thickness &tgr;′ therebetween. In this embodiment, the composite has three regions: hot, intermediate and cool.

Abstract: A carbon-rich zirconia-silica sol is prepared by the steps of dissolving zirconyl nitrate hydrate in absolute ethanol, mixing the solution thus obtained with a silicon alkoxide, and mixing the latter solution with a polyelectrolyte. The resulting carbon-rich sol/polyelectrolyte mixture can be employed to coat continuous fiber tow or filaments, to make nanosized zircon powder and to make a porous zircon membrane material.