General Atomics, Inc.

Khodabakhsh S Mazdiyasni

Kuo-Chun Chen

Debra J Treacy

Holger H Streckert

Frederick H Elsner

Paul W Trester

Barry W McQuillan

James E Sheehan

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.

Stable fiber interfaces for beryllium matrix composites

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. The fibers exhibit good tensile strength at high temperatures and can be employed to make ceramic composites having excellent resistance to high-temperature creep.

Crystalline yttrium aluminate and process for making

Method for in-situ prevention of stable barium carbonate formation in

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.

High purity copper alkoxides

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

Manufacture of high purity superconducting ceramic

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.

Method for preparing rare earth-barium-cuprate pre-ceramic resins and

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.

A method for producing shapes utilizing carbon-based fiber cloth materials embedded in silicon carbide matrices. Boron compound is applied to a preform which may be a plurality of carbon fiber sheets in a stack or which may be a complex three dimensional structure, such as a braided tube or a woven fiber network with filaments running in a plurality of different directions. Alternatively, individual sheets can be treated and then stacked or otherwise formed into a preform. Boron is applied in a form in which it serves as a wetting/bonding agent. The preform or each of the sheets is then impregnated with a polysilane resin. If sheets are used, the sheets are then stacked in mating face-to-face relationships in a desired preform shape. Thereafter, the preform is heated in a first heating step to a temperature sufficient to cross-link the polysilane, and then heated in a second heating step to a temperature sufficient to transform the crosslinked resin into a silicon carbide matrix having the carbon fiber network embedded therein.

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Alpine, CA, United States of America

Khodabakhsh S Mazdiyasni