Abstract: Inventive manufacture of CrB2—Al2O3 composites is based on pressureless sintering. According to typical inventive practice, CrB2 powder and Al2O3 powder are mixed together in selected volumetric proportions so that the volume of the CrB2 does not exceed 50% of the overall volume of the CrB2—Al2O3 mixture. The CrB2—Al2O3 mixture is shaped into a green body. The green body is pressureless sintered in a non-oxidizing atmosphere at a firing temperature in the approximate range between 1600° C. and 2050° C. The present invention succeeds in preparing, via pressureless sintering, a proportionality-associated range of compositions in the CrB2—Al2O3 system, which is a potentially “advanced” ceramic system. A typical inventively fabricated CrB2—Al2O3 composite is inventively configured in a complex shape, and has “advanced” material (e.g., mechanical) properties that are favorable for a contemplated application.

Abstract: The crystal structure of three compositions of matter has been determined to be iso-structural with FeB ortho-rhombic (space group Pnma). The crystalline structures are: Ti0.5Ta0.5B, Zr0.5Ta0.5B and Hf0.5Ta0.5B. A process for preparing ceramics is disclosed. Molded ceramics including the compositions of matter are useful for applications such as rocket nozzles, leading edges on hypersonic missiles, engine parts and other applications requiring a structural component to operate at temperatures of 1600° C. to 2400° C.

Abstract: There is provided a ceramic coating of zirconium diboride, silicon carbide, zirconium phosphate and silicon phosphate, that protects carbon-based materials from oxidation in high temperature oxidizing environments. The coating is applied at room temperature with a brush, roller, squeegee, doctor blade, spray gun, etc., and cured at room temperature. The cured material forms a hard, protective ceramic shell. The coating can be applied to various carbon based materials including, but not limited to, amorphous carbon foam, graphitic foam, monolithic graphite, and carbon-carbon composites. Alternative compositions of the coating can be the partial or complete substitution of hafnium diboride for zirconium diboride. Additional modifications of the coating can be accomplished by partial substitution of the borides or silicides of Ti, Ta, Cr, Nb, Ti, V, Re, for zirconium diboride.

Abstract: Ceramic composites of silicon carbide (SiC) grains and boron carbide (B.s4 C) grains which are uniformly coated with SiC are produced by reacting stoichiometric mixtures of silicon boride (SiB.sub.4, SiB.sub.6) and carbon (graphite or carbon black) in situ.

Abstract: A method of preventing thermite reactions during the high temperature incineration (slag temperature greater than 1200.degree. C.) of waste material streams containing aluminum and iron (steel) by mixing a low melting SiO.sub.2 containing material such as water glass or a mixture of sand with NaHCO.sub.3 or Na.sub.2 CO.sub.3 with the waste material.

Abstract: Ceramic composites of silicon carbide (SiC) grains and boron carbide (B.s4 C) grains which are uniformly coated with SiC are produced by reacting stoichiometric mixtures of silicon boride (SiB.sub.4, SiB.sub.6) and carbon (graphite or carbon black) in situ.

Abstract: Monoclinic celsian (BaO.Al.sub.2 O.sub.3.2SiO.sub.2) is produced by heating a stoichiometric, powder mixture of BaCO.sub.3 (or BaC.sub.2 O.sub.4), Al.sub.2 O.sub.3, and SiO.sub.2 (preferably SiO.sub.2 gel) with monoclinic celsian seeds at from 1250.degree. C. to 1500.degree. C.

Abstract: A ceramic material which is (1) ceramics based on monoclinic BaO.multidot.sub.2 O.sub.3 .multidot.2SiO.sub.2 ; (2) ceramics based on monoclinic SrO.multidot.Al.sub.2 O.sub.3 .multidot.2SiO.sub.2 ; or (3) ceramics based on monoclinic solid solution of BaO.multidot.Al.sub.2 O.sub.3 .multidot.2SiO.sub.2 and SrO.multidot.Al.sub.2 O.sub.3 .multidot.2SiO.sub.2.

Abstract: A glass which contains (1) an alkaline earth oxide that is BaO, SrO, or mures thereof, (2) Al.sub.2 O.sub.3, and (3) SiO.sub.2. The glass is useful as a sintering aid in the preparation of monoclinic BaO.Al.sub.2 O.sub.3.2SiO.sub.2 or monoclinic SrO.Al.sub.2 O.sub.3.2SiO.sub.2 ceramic structures.

Abstract: A composite with a reinforcing material that is Al.sub.2 O.sub.3, SiC, or xtures thereof in a matrix that is a ceramic material based on a solid solution of CrB.sub.2 and NbB.sub.2.

Abstract: A Si.sub.3 N.sub.4 reinforced aluminosilicate ceramic composite made ofA. from about 5 to about 40 weight percent of Si.sub.3 N.sub.4 reinforcem material;B. from about 15 to about 35 weight percent of the recrystalization products formed from a molten glass composed of(1) from about 8 to about 16 weight percent of Al.sub.2 O.sub.3,(2) from about 14 to about 45 mole percent of an alkaline earth oxide selected form the group consisting of BaO, SrO, and mixtures thereof, and(3) SiO.sub.2 being the remainder of the molten glass,wherein the recrystallization products are formed from the molten glass when the ceramic composite is cooled down after firing;C. the remainder of the composite being monoclinic BaO.Al.sub.2 O.sub.3.2SiO.sub.2 (BAS), monoclinic SrO.Al.sub.2 O.sub.3.2SiO.sub.2 (SAS), or a monoclinic solid solution of BAS and SAS.

Abstract: A ceramic electromagnetic window made of Si.sub.3 N.sub.4 particles which are bonded together by a metal phosphate binder that is an AlPO.sub.4 binder, a ZrP.sub.2 O.sub.7 binder, or mixtures thereof, wherein the Si.sub.3 N.sub.4 particles comprise from 55 to 85 volume percent of the ceramic material of the electromagnetic window with the metal phosphate binder comprising the remainder. By substituting Si.sub.3 N.sub.4 whiskers for some of the Si.sub.3 N.sub.4 particles a discontinuous fiber composite ceramic electromagnetic window is produced. The electromagnetic window may be a simple shape such as a flat or slightly curved sheet or a more complex shape such as a conical or spherical radome.

Abstract: Ceramic materials based on solid solutions of chromium diboride (CrB.sub.2) nd niobium diboride (NbB.sub.2).

Abstract: A Si.sub.3 N.sub.4 reinforced aluminosilicate ceramic composite made ofA. from about 5 to about 40 weight percent of Si.sub.3 N.sub.4 reinforcem material;B. from about 15 to about 35 weight percent of the recrystalization products formed from a molten glass composed of(1) from about 8 to about 16 weight percent of Al.sub.2 O.sub.3,(2) from about 14 to about 45 mole percent of an alkaline earth oxide selected form the group consisting of BaO, SrO, and mixtures thereof, and(3) SiO.sub.2 being the remainder of the molten glass,wherein the recrystallization products are formed from the molten glass when the ceramic composite is cooled down after firing;C. the remainder of the composite being monoclinic BaO.Al.sub.2 O.sub.3.2SiO.sub.2 (BAS), monoclinic SrO.Al.sub.2 O.sub.3.2SiO.sub.2 (SAS), or a monoclinic solid solution of BAS and SAS.

Abstract: A ceramic material made from raw coal fly ash or raw municipal solid waste fly ash and (1) sodium tetraborate or (2) a mixture of sodium tetraborate and a calcium containing material that is triple superphosphate, lime, dolomitic lime, or mixtures thereof.

Abstract: There is disclosed herein an invention for beneficiation of powered material having superconducting characteristics and processes for carrying it out. The invention involves introducing powdered superconducting material into the vertical field of a magnet wherein particles thereof are levitated according to the Meissner Effect. Particles which are more superconducting levitate at higher elevations or states above the magnet than do particles containing phases that are non-superconducting. Particles that are non-superconducting do not react at all in the magnetic field. Levitated particles are selectively harvested from whatever states desired.

Abstract: A process for preparing monoclinic celsian from AlF.sub.3, Al.sub.2 O.sub.3, BaCO.sub.3, and fused SiO.sub.2 powders by heating an intimate mixture of the powders (1) at from about 700.degree. to 900.degree. C. to form topaz and then (2) at a temperature as low as 900.degree. C. to produce monoclinic celsian. The reactions take place in an atmosphere of the gases generated by the reactions.

Abstract: A process for preparing monoclinic celsian from topaz and BaCO.sub.3, pows by heating an intimate mixture of the powders at a temperature of from 900.degree. C. to less than 1590.degree. C. in an atmosphere of the gases generated by the monoclinic celsian formation reaction itself.

Abstract: A process in which (1) AlF.sub.3 and SiO.sub.2 or AlF.sub.3, SiO.sub.2, and Al.sub.2 O.sub.3 powders are formed into a green body of a desired shape and size; (2) the green body is heated at 700.degree. C. to 950.degree. C. in an anhydrous SiF.sub.4 atmosphere to form barlike topaz crystals; and then (3) heated in an anhydrous SiF.sub.4 atmosphere at about 1150.degree. C. to 1700.degree. C. to convert the barlike topaz crystals to needlelike single crystal mullite whiskers which form a porous, rigid felt structure. The felt has the same shape as the green body with about 1.5 or less percent change in linear dimensions. The felt can be used as preforms for ceramic-matrix or metal-matrix composites or by itself as thermal insulation.

Abstract: A process for preparing mullite, 3Al.sub.2 O.sub.3.2SiO.sub.2, whiskers by(1) forming an intimate, anhydrous mixture of AlF.sub.3 and SiO.sub.2 powders in about a 12:13 molar ratio;(2) heating the mixture in an anhydrous, SiF.sub.4 atmosphere at about 700.degree. C. to about 950.degree. C. to form barlike crystalline topaz, Al.sub.2 (SiO.sub.4)F.sub.2 ; and(3) heating the barlike crystalline topaz under anhydrous conditions in a SiF.sub.4 atmosphere at a temperature of from about 1150.degree. C. to about 1400.degree. C. to produce mullite whiskers.The mullite whiskers produced can be used in ceramic and metal matrices without further chemical treatment.