Abstract: CVD Si.sub.3 N.sub.4 can be made by placing a substrate (2) inside a CVD reactor (4) having an interior and interior walls (6). The interior walls of the reactor are include a high temperature metal selected from the group consisting of Mo, Nb, Rh, Hf, Ta, W, Re, and Ir. An inert gas is flowed through the reactor (4) and the pressure inside the reactor is reduced to less than about 40 kPa. The substrate (2) and interior of the reactor (4) are heated to a temperature between about 1200.degree. C. and about 1700.degree. C. A reactant gas mixture of a silicon halide and an excess of a nitrogen-containing compound is flowed into the reactor such that the silicon halide reacts with the nitrogen-containing compound to form Si.sub.3 N.sub.4. The high temperature metal on the interior walls (6) of the reactor (4) inhibits the formation of Si.sub.3 N.sub.4 on the interior walls of the reactor so the majority of the Si.sub.3 N.sub.4 forms on the substrate (2).

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: A process for recovering oxygen from carbon dioxide is disclosed which is an improvement over the conventional process of utilizing an iron carbide catalyst in such reclamation process. As with the conventional processes the carbon dioxide is reacted with hydrogen to form a mixture of methane and water. The methane produced is then passed over a high temperature stable glass surface heated to about 1000.degree. C.-1200.degree. C. to produce hydrogen gas and a high density carbon, i.e. having a density greater than about 2 grams per cubic centimeter. This results in lessening of the storage problem for the carbon material because of its high density. The hydrogen gas produced is also recycled back to the incoming carbon dioxide for reaction.

Abstract: Carbon-carbon composites are prepared to receive a subsequent protective coating by having a thin coating (0.1 to 5 mils) of chemically vapor deposited (CVD) SiC applied to its surface. The SiC layer improves the performance of subsequent protective coatings (especially pack produced SiC conversion coatings), especially in the case of carbon-carbon composites having a negative coefficient of thermal expansion.

Abstract: A spar for use in a helicopter is produced by a three step process including first a low temperature low pressure step, second a high pressure high temperature step for a short time and third a low pressure (atmospheric) medium temperature step for a relatively long time.

Abstract: A method of producing high density carbon at relatively low temperatures is described. By flowing methane gas over glass rods or tubes at flow rates of 10 to 1300 cc per minute and temperatures of 1000.degree. to 1200.degree. C., carbon having a density greater than 2 grams per cubic centimeter and hydrogen gas are produced. An inert gas such as argon can be intermittently pulsed through the system to sweep the system free of low density carbon deposits and heating preferably takes place by means of induction coil heated graphite susceptors or resistance heaters.

Abstract: Silicon carbide coated carbon fibers and composite materials incorporating these fibers are disclosed. The silicon carbide coating provides electrical insulation and improved resistance to environmental degradation. The coated fibers may be embedded in organic, metal or glass matrices to form useful composite materials.