Abstract: Aqueous precursor solutions are described that comprise at least one monazite-based material precursor, at least one xenotime-based material precursor or a combination thereof; and a plurality of fine suspended particles of an oxide material. Contemplated oxide composites, as described herein, comprise a plurality of fibers surrounded by at least one monazite or xenotime-based material, wherein the oxide composite has nearly a fully dense matrix. Contemplated embodiments disclosed herein provides a method for producing an oxide composite with nearly fully dense matrix and with all fibers surrounded by a monazite- or xenotime-based material that prevents embrittlement at temperatures at least as high as 1200° C.

Abstract: Monazites and xenotimes are rare-earth phosphates showing a combination of properties expected to be suitable for thermal barrier coatings. For example, lanthanum phosphate (La-monazite) can be used to form thermal barrier coatings to protect superalloy and ceramic parts exposed to high temperature and damage by sulfur, vanadium, phosphorus and other contaminants. The monazite or xenotime coatings can be applied using any of the common application methods including EB-PVD, laser ablation and plasma spraying. The stoichiometry of the coatings can be modulated according to the stoichiometry of specially prepared starting target (source) material. The most effective coatings appear to be largely crystalline and show a columnar structure with feather-like microstructure. For La-monazite, effective coatings between 10 and 500 micrometers in thickness can be deposited on substrates having temperatures between about 750° C. and about 950° C.

Abstract: The present invention relates to porous calcium zirconate/magnesia composites having a thermally and chemically stable porous structure, which consist of sintered compacts having a fine composite structure stable under high temperatures due to uniformly dispersed equimolar amounts of calcium zirconate [CazrO3] and magnesia [MgO] and controlled grain growth, and a method of producing the same, and the present porous composites are useful as, for instance, a functional material for filtering highly corrosion resistant materials, lightening members used at super-high temperatures, catalyst carriers, insulation or sound-absorbing materials, and the like.

Abstract: Thermodynamically stable ceramic composites are provided for use in high temperature reactive environments. A phosphate selected from monazites and xenotimes functions as a weak bond material in the composite. Monazite comprises a family of minerals having the form MPO.sub.4, where M is selected from the larger trivalent rare earth elements of the lanthanide series (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb) and coupled substituted divalents and tetravalents such as Ca or Sr with Zr or Th. Xenotimes are phosphates similar to monazite where M is selected from Sc, Y, and the smaller trivalent rare earth elements of the lanthanide series (Dy, Ho, Er, Tm, Yb, and Lu).

Abstract: Thermodynamically stable ceramic composites are provided for use in high temperature oxidizing environments. A phosphate selected from monazites and xenotimes functions as a weak bond interphase material between the constituents of the composites. Monazite comprises a family of minerals having the form MPO.sub.4, where M is selected from the larger trivalent rare earth elements of the lanthanide series (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, and Tb) and coupled substituted divalents and tetravalents such as Ca or Sr with Zr or Th. Xenotimes are phosphates similar to monazite where M is selected from Sc, Y, and the smaller trivalent rare earth elements of the lanthanide series (Dy, Ho, Er, Tm, Yb, and Lu).

Abstract: Molten salt process for destruction of fluorine-containing waste in a molten salt such as molten sodium carbonate, and forming fluoride salts in the molten salt bath. The destructive phase change of conventional alpha-alumina refractory of the molten salt retaining vessel in the presence of such fluoride salts is avoided according to the invention by employing phase change resistant beta-alumina refractory bricks.

Abstract: A magnetic switch for recording the change in position of a magnetic field includes a first object on which is positioned a source of magnetic force for creating a magnetic field and a second object on which is positioned at least one type II superconducting medium. The type II superconducting medium exhibits a permanent magnetic component after exposure to a magnetic field, such that relative motion between the first object and the second object causes the magnetic field to induce a residual magnetization in the superconducting medium.

Abstract: Thermodynamically stable ceramic composites are provided for use in high temperature oxidizing environments. The composites comprise high strength alumina fibers (Al.sub.2 O.sub.3) in a ceramic matrix. The ceramic matrix comprises material similar to the fibers to improve compatibility of the composite materials. A material selected from the .beta.-alumina and magnetoplumbite family of materials is used to provide a weakly bonded interface between the fibers and the ceramic matrix. .beta.-aluminas and magnetoplumbites have weak layers as an intrinsic characteristic of their crystal structure, which comprise spinel layers (basically Al.sub.2 O.sub.3) separated by very weakly bonded planes containing the .beta.-forming ions. The weak planes of these materials allow preferential debonding and sliding, and thus inhibit crack growth across the interface between the fibers and the ceramic matrix. The alumina fibers can be coated with .beta.

Abstract: A tunable electromagnetic filter includes a type II superconducting medium which exhibits a permanent ferromagnetic component after exposure to a magnetic field. A magnetic field passes through the medium in a first direction, while an input conductor wound around the medium in a second direction perpendicular to the first direction receives an input signal, and an output conductor is wound around the medium in a third direction perpendicular to the first and second directions. At resonance of the medium, an alternating field magnetic component perpendicular to both the incoming signal and the magnetic field is created to induce a current of the resonant frequency in the output conductor.

Abstract: A process is disclosed for producing, at a low temperature, a high purity reaction product consisting essentially of silicon, nitrogen, and hydrogen which can then be heated to produce a high purity alpha silicon nitride. The process comprises: reacting together a particulate elemental high purity silicon with a high purity nitrogen-hydrogen reactant in its liquid state (such as ammonia or hydrazine) having the formula: N.sub.n H.sub.(n+m) wherein: n=1-4 and m=2 when the nitrogen-hydrogen reactant is straight chain, and 0 when the nitrogen-hydrogen reactant is cyclic. High purity silicon nitride can be formed from this intermediate product by heating the intermediate product at a temperature of from about 1200.degree.-1700.degree. C. for a period from about 15 minutes up to about 2 hours to form a high purity alpha silicon nitride product.

Abstract: A process is disclosed for producing, at a low temperature, a high purity organic reaction product consisting essentially of silicon, hydrogen, nitrogen, and carbon. The process comprises reacting together a particulate elemental high purity silicon with a high purity reactive amine reactant in a liquid state at a temperature of from about 0.degree. C. up to about 300.degree. C. A high purity silicon carbide/silicon nitride ceramic product can be formed from this intermediate product, if desired, by heating the intermediate product at a temperature of from about 1200.degree.-1700.degree. C. for a period from about 15 minutes up to about 2 hours or the organic reaction product may be employed in other chemical uses.

Abstract: A device is provided for suspending an external load by means of a magnetic field and a superconductor. The superconductor is supported in a magnetic field which penetrates the superconductor. A magnet is suspended below the superconductor and oriented so that its magnetic moment is aligned parallel to the magnetic field. The magnet is provided with a coupling means so that it can be coupled to an external load. Either a vertical or a horizontal magnetic field can be used. In one embodiment, the load-carrying member is a composite material suspended from a supported magnet. The composite consists of a superconducting phase and an attractive phase comprising either a magnet, a ferromagnetic material, or a paramagnetic material. In another embodiment, a device for concentrating flux is provided by placing a superconductor between the source of the magnetic field and the position in which the concentrated flux is desired.

Abstract: A method for growing crystals of sodium beta" alumina is described. The crystals are grown by Czochralski type processes or analogous methods wherein single crystals are formed from a flux or melt. The melt is a eutectic type liquid primarily containing Na or K, (Li, Mg or other divalent element, e.g. Ni.sup.2+, Co.sup.2+, Cr.sup.2+, Fe.sup.2+, etc.) Al, in proportions to produce beta" alumina. To lower the melt temperature to where e.g. Na.sub.2 MgAl.sub.10 O.sub.17 beta" or Na.sub.2 Li.sub.1/2 Al.sub.11/2.degree.17 beta" can crystallize in its stability region (approximately less than 1700.degree. C. for the Mg version and approximately less than 1600.degree. C. for the Li version) high valent ions, which do not enter the structure, particularly V.sup.5+, Nb.sup.5+, Ta.sup.5+, Zr.sup.4+ and/or Hf.sup.4+ are added to the melt. The method has allowed the growth of single crystals of the Li-stabilized sodium and potassium varieties for the first time.

Abstract: A process for producing novel oxy-metallo-organic, e.g. oxy-alkoxy, polymers is disclosed which comprises heating a metallo-organic compound, e.g. an alkoxide of a metal selected from the group consisting of aluminum, titanium and zirconium, and mixtures thereof, such as aluminum butoxide, under reflux in inert atmosphere and in the absence of any solvent, and polymerizing the metallo-organic compound. The resulting polymer can be in the form of a viscous liquid, a glass or an amorphous powder, and can function as intermediates or precursors for production of ceramics, ceramic composites, fibers and films.

Abstract: A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of "whiskers" or needles is heated at temperature ranging from about 900.degree. C. to about 1200.degree. C. to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900.degree. C.

Abstract: At least 1 mole % SiO.sub.2 and 1/2 mole % Sc.sub.2 O.sub.3 are used as a densification aid to provide a polyphase silicon nitride ceramic having high creep strength. The composition is within the Si.sub.3 N.sub.4 - Si.sub.2 N.sub.2 O tie line, the Si.sub.3 N.sub.4 - Sc.sub.2 Si.sub.2 O.sub.7 tie line, and the Sc.sub.2 Si.sub.2 O.sub.7 - Si.sub.2 N.sub.2 O tie line in the ternary phase diagram for the Si.sub.3 N.sub.4, SiO.sub.2, Sc.sub.2 O.sub.3 system. The phases in the sintered ceramic are Sc.sub.2 Si.sub.2 O.sub.7, and Si.sub.3 N.sub.2 O, and at least 50 mole % Si.sub.3 N.sub.4.

Abstract: A process for forming a precursor powder which, when suitably pressed and sintered forms highly pure, densified .beta.- or .beta."-alumina, comprising the steps of:(1) forming a suspension (or slurry) of Bayer-derived Al(OH).sub.3 in a water-miscible solvent;(2) adding an aqueous solution of a Mg compound, a Li compound, a Na compound or mixtures thereof to the Bayer-derived Al(OH).sub.3 suspension while agitating the mixture formed thereby, to produce a gel;(3) drying the gel at a temperature above the normal boiling point of water to produce a powder material;(4) lightly ball milling and sieving said powder material; and(5) heating the ball-milled and sieved powder material at a temperature of between 350.degree. to 900.degree. C. to form the .beta.- or .beta."-alumina precursor powder. The precursor powder, thus formed, may be subsequently isopressed at a high pressure and sintered at an elevated temperature to produce .beta.- or .beta."-alumina.

Abstract: A technique of forming electrodes for magneto-hydrodynamic generators having the composition (La.sub.1.sub.-x Y.sbsb.x ) CrO.sub.3 where Y is strontium, calcium or magnesium and having densities of as high as 97% of theoretical or even higher is provided. Electrodes of such densities offer superior mechanical and electrical properties when employed in magneto-hydrodynamic generators.