Abstract: High-temperature-stable, fiber-reinforced beryllium metal matrix composite materials are fabricated using coating, infiltration and hot-pressing procedures. High-temperature-stable fibers of metal oxides, carbon or silicon carbide are coated with reaction barrier coatings which prevent chemical reactions from occurring at the interface with the surrounding metallic beryllium matrix at temperatures up to close to the melting point of beryllium. Coatings such as yttria, YAG and mixtures of yttria and YAG or of yttria and beryllia are employed exterior of metal oxide fibers, such as alumina or alumina-silica fibers. Suitable reaction barrier coatings are also employed over carbon fibers (or silicon carbide fibers) which preferably include an interior coating of elemental silicon upon the exterior surface of the carbon fibers. Oxide coatings are preferably applied by immersion in a liquid bath containing a suitable coating solution, preferably an alcohol solvent alkoxide sol-gel.

Abstract: Ceramic yttrium aluminate fibers are produced by processes that result in the formation of a microcrystalline ceramic oxide structure. In one process, a stoichiometric amount of a yttrium alkoxide is mixed with an aluminum alkoxide to produce a homogeneous mixture in an alcohol solvent. Following the addition of an alkoxide precursor of ZrO.sub.2 or of HfO.sub.2, the optional addition of an alkoxide precursor of MgO, and the subsequent addition of an organic acid, hydrolytic condensation to produce a suitable sol is accomplished by adding water. A slight excess of yttrium alkoxide can be used instead of the MgO precursor. The viscosity of the sol is adjusted to form a tractable gel that is spun into fibers which, after curing and firing, are shown to be microcrystalline in form, the resulting fibers having a submicron average grain size. Strength and stability result from the presence of solid particles of partially stabilized zirconia or hafnia at the grain boundaries and the triple points.

Abstract: The invention relates to the preparation of high purity, chloride- and alkali metal-free copper (II) alkoxides by means of the reaction of an alcoholic alkali metal alkoxide solution with copper (II) fluoride; ammoniating the resulting solution to render soluble the resulting copper (II) alkoxide; and filtering the resulting solution to obtain an alkali metal- and chloride-free alcoholic copper (II) alkoxide solution. The resulting solution is useful in the preparation of superconducting compound such as yttrium-barium-copper oxide superconductor.

Abstract: A method for the manufacture of superconducting polycrystalline ceramic materials by the decomposition of a mixture of isopropoxides.

Abstract: A method of making high T.sub.c 1-2-3 superconductors having perovskite structure using solution techniques is disclosed. The process uses two solvent systems to form a resinous preceramic material having a controlled viscosity for facilitating its formation into superconducting articles such as fibers, wires, ribbons, films and the like. The process yields a pre-ceramic which is flexible and which has sufficient structural integrity to withstand normal handling.

Abstract: A method of making high T.sub.c 1-2-3 superconductors having perovskite structure using solution techniques is disclosed. The process uses two solvent system to form a resinous pre-ceramic material having a controlled viscosity for facilitating its formation into superconducting articles such as fibers, wires, ribbons, films and the like. The process yields a pre-ceramic which is flexible and which has sufficient structural integrity to withstand normal handling.

Abstract: The invention relates to the preparation of high purity, chloride- and alkali metal-free copper (II) alkoxides by means of the reaction of an alcoholic alkali metal alkoxide solution with copper (II) fluoride; ammoniating the resulting solution to render soluble the resulting copper (II) alkoxide; and filtering the resulting solution to obtain an alkali metal- and chloride-free alcoholic copper (II) alkoxide solution. The resulting solution is useful in the preparation of superconducting compound such as yttrium-barium-copper oxide superconductor.

Abstract: Porous reaction sintered silicon nitride body is infiltrated with an organosilicon compound after which the body is heated at a temperature sufficient to decompose the infiltrated material, resulting in a silicon nitride body having an increased density and significantly improved room temperature strength.

Abstract: In a method for fabricating highly dense, polycrystalline silicon nitride bodies, a mixture of silicon nitride powder and an oxide, hydride or nitride of an element of the lanthanide series in powder form is hot pressed at a temperature ranging from 1600.degree. to 1750.degree. C for a period of 30 to 60 minutes. The method is particularly useful for fabricating structural components, such as stators, blades, airfoils and buckets in high performance gas turbine engines.

Abstract: In the casting of metal alloys to form hollow articles, a mold of a desired shape containing a core material fabricated to a desired configuration from a silicon yttrium or silicon lanthanide oxynitride is filled with a molten metal alloy while maintaining the mold under a vacuum or under a blanket of an inert gas after which the mold is allowed to cool slowly to room temperature. The casted metal alloy with the core material exposed at one end is removed from the mold and heated under ambient conditions, thereby causing the silicon yttrium or silicon lanthanide oxynitride to oxidize with a large volume expansion and a concomitant catastrophic failure of the core material. The broken pieces of core material are removed from the casting which has a smooth inner surface, an indication that no chemical reactions have occurred between the alloy and the core material.

Abstract: In a method for casting metal alloys, a molten metal alloy is introduced into a mold of a desired configuration containing a core material fabricated to a desired shape from titanium nitride while maintaining the mold under a vacuum. After allowing the mold to cool slowly to room temperature, the casted metal alloy with the core material exposed at one end is removed from the mold and immersed in a boiling caustic solution, thereby causing the titanium nitride core material to decompose. The casting so obtained has a smooth inner surface, an indication that no chemical reactions have occurred between the alloy and the core material.

Abstract: Yttrium and rare earth metal hexafluoroisopropoxide diammoniates are prepared by reacting yttrium and rare earth metal chlorides with 1,1,1,3,3,3-hexafluoroisopropanol in the presence of anhydrous ammonia. The compounds are useful as catalysts for organic and polymerization reactions, as dopants for semi-conductor devices, and in preparing thin film coatings.

Abstract: A method is provided for preparing alpha silicon nitride powder in which very high purity, liquid silicon tetrachloride is reacted with an excess of ammonia gas in dry deoxygenated benzene or normal hexane at about 0.degree.C, yielding a precipitate of silicon diimide and ammonium chloride. After removal of the benzene or n-hexane from the precipitate, the mixture of silicon diimide and ammonium chloride powder is heated under a vacuum from room temperature to a temperature in the range of 1200.degree. to 1350.degree.C and maintained at the latter temperature for a period of about 2 to 8 hours. The product obtained is a high purity, submicron, alpha phase silicon nitride powder which is eminently suitable for the fabrication of dense, high strength, creep resistant and thermal shock resistant bodies for use in high performance gas turbine engines and in radome applications.