Abstract: A fiber is coated with boron carbide by contacting the fiber with a reaction mixture of a boron source and a carbon source at a temperature of at least about 1050.degree. C. such that the boron source and carbon source react with each other to produce a boron carbide coating on the fiber. The fiber comprises aluminum oxide, SiC, or Si.sub.3 N.sub.4 and the boron carbide coating comprises up to about 40 atomic percent boron.

Abstract: A metal nitride powder can be made by heating a reactant powder that includes an oxide or hydroxide of Al, Ti, or Zr to a reaction temperature in a nonreactive atmosphere. The heated reactant powder is contacted with a gaseous reactant mixture comprising a nitrogen source and a carbon source. The molar ratio of nitrogen to carbon in the gaseous reactant mixture is at least about 15. The reactant powder is maintained at the reaction temperature for a sufficient time to convert a portion of it to metal nitride powder.

Abstract: A metal nitride powder can be made by heating a reactant powder that includes an oxide or hydroxide of Al, Ti, or Zr to a reaction temperature in a nonreactive atmosphere. The heated reactant powder is contacted with a gaseous reactant mixture comprising a nitrogen source and a carbon source. The molar ratio of nitrogen to carbon in the gaseous reactant mixture is at least about 15. The reactant powder is maintained at the reaction temperature for a sufficient time to convert a portion of it to metal nitride powder.

Abstract: A method for making a high critical current density Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor includes mixing suitable solid state reactants in amounts sufficient to create a reactant mixture having a ratio of approximately 4 Bi atoms:3 Ca atoms:3 Sr atoms:4 Cu atoms and oxygen. The reactant mixture is heated to a sufficient temperature for a sufficient time to sinter the reactant mixture and form a Bi.sub.2 CaSr.sub.2 Cu.sub.2 O.sub.8 superconductor.

Abstract: An oriented superconducting material may be made by cold pressing a nonoriented superconducting material selected from the group consisting of Bi.sub.1, Bi.sub.2, Tl.sub.1, Tl.sub.2, Pb substituted Bi.sub.1, Pb substituted Bi.sub.2, Pb substituted Tl.sub.1, and Pb substituted Tl.sub.2 superconductor materials at a pressure sufficient to form an oriented superconducting material.

Abstract: Chemical vapor deposition (CVD) techniques for forming tough silicon carbide (SiC) matrix composites. The introduction of methyldichlorosilane (MDS) to a reactor containing a fiber preform which been flushed with a noble gas, causes the formation of a carbon layer around the fibers. The carbon interlayer improves the fracture toughness of the composite.

Abstract: Gas turbine engine carbon-carbon composite components having multilayer coatings resulting in components resistant to oxidation at temperatures greater than 2500.degree. F. A first multilayer coating comprises a pack derived silicon carbide coating covered with a chemical vapor deposition layer of silicon nitride. A second multilayer coating comprises a layer of pyrolytic graphite covered with a pack derived silicon carbide coating covered with a chemical vapor deposition layer of silicon nitride. The third multilayer coating comprises a layer of chemical vapor deposition applied silicon carbide covered with a pack derived silicon carbide coating covered with a chemical vapor deposition layer of silicon nitride.

Abstract: Amorphous boron-carbon alloy cutting tool bits and methods of making them are described. The tool bits can be composites of conventional hard alloys containing the amorphous boron carbon alloy in a first layer over a conventional hard alloy layer such as cobalt bonded tungsten carbide. The amorphous boron carbon alloy used is preferably produced in bulk with a grain size less than 30 .ANG. and ground into a powder. The tool bits are produced by cold compressing, in a tool bit die, the lower layer material at about 2000 psi followed by hot compressing the composite containing the added amorphous boron carbon alloy powder at about 1350.degree.-1500.degree. C. The resultant cutting tool bit has a cutting lifetime at least four times that of conventional carbide cutting tool bits even when cutting such things as nickel superalloys at speeds in excess of 125 surface feet per minute (SFM).

Abstract: Amorphous boron-carbon alloy cutting tool bits and methods of making them are described. The tool bits can be composites of conventional hard alloys containing the amorphous boron carbon alloy in a first layer over a conventional hard alloy layer such as cobalt bonded tungsten carbide. The amorphous boron carbon alloy used is preferably produced in bulk with a grain size less than 30 .ANG. and ground into a powder. The tool bits are produced by cold compressing, in a tool bit die, the lower layer material at about 2000 psi followed by hot compressing the composite containing the added amorphous boron carbon alloy powder at about 1350.degree.-1500.degree. C. The resultant cutting tool bit has a cutting lifetime at least four times that of conventional carbide cutting tool bits even when cutting such things as nickel superalloys at speeds in excess of 125 surface feet per minute (SFM).

Abstract: An improved mirror substrate, that is particularly adapted for use as a laser mirror, has significantly improved transverse strength and polishability and a method of making the same. The composite comprises graphite fibers coated with an oxidized silicon carbide layer. The coated fibers alternate with layers of glass to form a composite, preferably having a central plane of symmetry across its central plane.

Abstract: A method for repairing a multilayer coating on a carbon-carbon composite having a CVD silicon nitride outercoating by applying a coating of CVD silicon nitride. It has been found that if a multilayer coating containing CVD silicon nitride on a carbon-carbon composite is broken the entire composite will fail to survive at elevated temperatures due to oxidation. However, the deposition of silicon nitride on such a composite will affect repair such that the newly coated composite will substantially resist oxidation at temperatures up to 1750.degree. C. and above. Preferably the coated composite is maintained at a temperature of about 1500.degree. C. and a gaseous mixture containing silicon tetrafluoride and anhydrous ammonia is passed over the composite at a partial pressure of the reactant gases less than about 10 millimeters mercury.

Abstract: Articles and method for containing molten nickel and methods for making the former. The material used is a high density silicon nitride that is very resistant to the corrosive properties of molten nickel alloys. The composition needed to produce such a containing article comprises polycrystalline silicon nitride containing (by weight) about 0.6% to about 8% alumina, about 15% yttria and about 2% to about 5% silica or amorphous silicon nitride containing about 2% to about 6% alumina, and about 15% yttria and about 2% to about 5% silica. The articles are formed by cold pressing and sintering methods. These articles are particularly useful in processes for molding and (RSR.TM.) spinning molten nickel alloys.

Abstract: An erosion resistant composite material is described comprising silicon nitride rod reinforced nickel alloy, where the silicon nitride is cold pressed and sintered and substantially nonreactive with the alloy at high temperatures. The silicon nitride can either be polycrystalline or amorphous containing alumina, 15% yttria and about 2% to about 5% silica. Three to 8% alumina is used in the case of polycrystalline silicon nitride and 2% to 6% alumina is used in the case of amorphous silicon nitride.

Abstract: Carbon-carbon composite materials are provided with significantly enhanced oxidation resistance by the formation of a SiC coating. The coating is produced from a pack containing a small but effective amount of boron. The balance of the pack is preferably based on Al.sub.2 O.sub.3, SiO.sub.2, and Si. The composite to be coated is embedded in the pack and heated to an elevated temperature. The boron addition provides a conversion SiC coating having enhanced resistance to oxidation.

Abstract: The process of making an article of chemically vapor deposited silicon nitride on a pattern at high temperature including the use of methane to reduce the grain size of the deposited compound.

Abstract: Carbon-carbon composites are prepared to receive a subsequent protective coating by having a thin layer (1 to 5 mils) of pyrolytic graphite applied to its surface. The graphite layer improves the performance of subsequent protective coatings and is especially useful on carbon-carbon composites having a positive coefficient of thermal expansion.

Abstract: Carbon-carbon composite materials are provided with significantly enhanced oxidation resistance by the formation of a SiC coating. The coating is produced from a pack containing a small but effective amount of boron. The balance of the pack is preferably based on Al.sub.2 O.sub.3, SiO.sub.2, and Si. The composite to be coated is embedded in the pack and heated to an elevated temperature. The boron addition provides a conversion SiC coating having enhanced resistance to oxidation.

Abstract: A multilayer coating system for the protection of carbon-carbon composites is described. The coating includes an inner layer of SiC produced by diffusing Si into the carbon substrate (0.5 to 30 mils thick), and at an outer layer of CVD (chemically vapor deposited) SiC (5 to 30 mils thick). Such a coating successfully protects carbon-carbon materials from oxidation at temperatures up to 2500.degree. F. (1371.degree. C.) and above.

Abstract: A multilayer coating system for the protection of carbon-carbon composites is described. The coating includes an inner layer of SiC (produced by a conversion process in which Si is diffused into the carbon substrate) and an outer layer of CVD (chemically vapor deposited) Si.sub.3 N.sub.4. Such a coating provides exceptional oxidation resistance, to 2500.degree. F. (1371.degree. C.) and above, for carbon-carbon materials. Optionally, preliminary coatings of CVD SiC or pyrolytic graphite can be applied prior to application of the inner layer of SiC.

Abstract: The impact resistance of hot pressed silicon carbide articles is improved by providing thereon a layer of material resulting from the reaction of silicon in a dilute hydrocarbon gas atmosphere. To form the impact absorbing layer of porous silicon carbide, a silicon powder compact is heated at about 1400.degree. C. in a gas stream comprised predominantly of a carrier gas such as hydrogen, with a reactive hydrocarbon gas such as methane. Unitary articles may also be formed.