Rockwell International Corporation

The United States of America as Represented by the United States

The Boeing Company

University of California

The United States of America as Represented by the Department of Energy

Peter E Morgan

David Bruce Marshall

Roger E De Wames

Joseph J Ratto

Eloise A Pugar

Ira B Goldberg

William F Hall

Gary D Schnittgrund

Bruce S Dunn

Janet B Davis

Olivier H Sudre

Brian Nelson Cox

Julia Jeannine Mack

A self-transpiring hot skin for a hypersonic or reusable space vehicle that can provide protection to the vehicle during short periods of abnormally high heat flux (either planned in the flight profile or an off-nominal event). The hot skin includes a ceramic composite structure having an internal cavity that is coupled either to the insulating layer or directly to the support structure of the hypersonic vehicle. The internal cavity includes a material system that vaporizes, sublimes or decomposes into a gas when the temperature exceeds the upper temperature capability of the composite material. The gas transpires through the outer layer of the composite material to provide cooling to the outer layer below the upper temperature capability. Cooling may occur both by conduction of heat from the composite material to the transpiring gas and by the interaction of the transpiring gas with the boundary layer of hypersonic flow over the outer surface, leading to a reduction of the heat flux entering the surface.

Materials for self-transpiring hot skins for hypersonic vehicles or reusable space vehicles

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). High temperature ceramic composites that include monazite or xenotime and exhibit damage tolerant behavior or non-catastrophic fracture may be fabricated in a variety of material systems and reinforcement morphologies, including multilayered laminar composites; fiber, whisker, and particulate reinforced composites; hybrid laminar composites; and fabric or fiber preform composites. In preferred embodiments, the ceramic matrix comprises a material similar to the reinforcement to improve compatibility of the composite materials. The weak bond material allows debonding and 'frictional' sliding between the constituents of the composite and inhibits crack growth across the interface.

Fibrous composites including monazites and xenotimes

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). High temperature ceramic composites that include monazite or xenotime and exhibit damage tolerant behavior or non-catastrophic fracture may be fabricated in a variety of material systems and reinforcement morphologies, including multilayered laminar composites; fiber, whisker, and particulate reinforced composites; and hybrid laminar composites. Alumina fibers may be used in single crystal or polycrystalline form as a reinforcement material. In preferred embodiments, the ceramic matrix comprises a material similar to the reinforcement to improve compatibility of the composite materials. The interphase material allows debonding and 'frictional' sliding between the constituents of the composite and inhibits crack growth across the interface.

Ceramic composites having a weak bond material selected from monazites

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.

Refractory for containment of fluoride-rich salt melts

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. A device for sensing the direction of a magnetic field includes a first type II superconducting medium adapted to exhibit a permanent magnetic component after exposure to a magnetic field having a first direction, a second type II superconducting medium adapted to exhibit a permanent magnetic component after exposure to a magnetic field having a second direction orthogonal to the first direction, and a third type II superconducting medium adapted to exhibit a permanent magnetic component after exposure to a magnetic field having a third direction orthogonal to the first and second directions.

High temperature superconductor magnetic-switch

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.-alumina by any of several methods such as heat treating the fibers in an atmosphere containing the desired .beta.-forming ions. Composite structures can be fabricated by placing the coated fibers in powdered matrix material and hot pressing. .beta.-alumina can also be formed in situ within a preformed composite by providing the .beta.-forming ions in a compound that is phase compatible with the ceramic matrix material and then heat treating the composite to form .beta.-alumina at the fiber-matrix interface.

High temperature ceramic composites

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.

Superconductors with switchable magnetic domains

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. The discovery of the existence of a soluble Si-N-H intermediate enables chemical pathways to be explored previously unavailable in conventional solid state approaches to silicon-nitrogen ceramics.

Process for producing high purity silicon nitride by the direct reaction

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.

Process for producing organic products containing silicon, hydrogen,

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.

Magnetic suspension and magnetic field concentration using

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.

Flux growth of sodium beta' alumina

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.

Production of oxy-metallo-organic polymer

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.

Process for producing amorphous and crystalline silicon nitride

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.

Si.sub.3 N.sub.4 Ceramic densified using Sc.sub.2 O.sub.3 and SiO.sub.2

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:

Growing community of inventors

Thousand Oaks, CA, United States of America

Peter E Morgan