The United States of America As Represented by the Administrator of the

Hc Chem Research and Service Corp.

United States of America As Represented by the Administrator of Nasa

The United States of America As Represented by the United States

Ming-ta S Hsu

Timothy S Chen

Salvatore R Riccitiello

John A Parker

Alvin H Heimbuch

Daniel B Leiser

Daniel J Rasky

Huy K Tran

Domenick E Cagliostro

William D Henline

Demetrius A Kourtides

Joseph A Carroll

Christine E Szalai

A low density organic polymer impregnated preformed fibrous ceramic article includes a plurality of layers. A front layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one organic polymer. A middle layer includes polymer impregnated ceramic fibers. A back layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one low temperature pyrolyzing organic polymer capable of decomposing without depositing residues.

Secondary polymer layered impregnated tile

Ultra-high temperature, light-weight, black ceramic insulation having a density ranging from about 0.12 g/cc. to 0.6 g/cc. such as ceramic tile is obtained by pyrolyzing siloxane gels derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes also may contain an effective amount of a mono- or trialkoxy silane to obtain the siloxane gels. The siloxane gels are dried at ambient temperatures and pressures to form siloxane ceramic precursors without significant shrinkage. The siloxane ceramic precursors are subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700&deg; C., and particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

Light-weight black ceramic insulation

Non-flammable, fibrous-siloxane cured composites derived from the polymerization of dialkoxysilanes, trialkoxysilanes and tetraalkoxysilanes, in an aqueous medium, to obtain viscous polysiloxane resins. These siloxane resins are used to impregnate or coat various fibrous materials such as carbon fibers or glass cloth which are subsequently subjected to heat and pressure to form cured, non-flammable siloxane-impregnated composites e.g. panels having a density of about 1 to 3 g/cc. and a limited oxygen index above 30. These non-flammable, fibrous-siloxane composites are particularly useful in the manufacture of fire-proof materials for various transportation vehicles and for building materials e.g. panels as a fire barrier.

Non-flammable polymer composite panels

Ultra-high temperature, light-weight, ceramic insulation such as ceramic tile is obtained by pyrolyzing a siloxane gel derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes may contain also an effective amount of a mono- or trialkoxy silane to obtain the siloxane gel. The siloxane gel is dried at ambient pressures to form a siloxane ceramic precursor without significant shrinkage. The siloxane ceramic precursor is subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation, can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700&deg; C. and is particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

Light-weight ceramic insulation

High-temperature, lightweight, ceramic carbon insulation is prepared by coating or impregnating a porous carbon substrate with a siloxane gel derived from the reaction of an organodialkoxy silane and an organotrialkoxy silane in an acid or base medium in the presence of the carbon substrate. The siloxane gel is subsequently dried on the carbon substrate to form a ceramic carbon precursor. The carbon precursor is pyrolyzed, in an inert atmosphere, to form the ceramic insulation containing carbon, silicon, and oxygen. The carbon insulation is characterized as a porous, fibrous, carbon ceramic tile which is particularly useful as lightweight tiles for spacecraft.

Refractory oxidative-resistant ceramic carbon insulation

Ceramics are or protected from high temperature degradation, including high temperature, oxidative, aeroconvective degradation by a high temperature and oxidation resistant coating of a room temperature curing, hydrolyzed and partially condensed liquid polyorganosiloxane applied to the surface of the ceramic. The liquid polyorganosiloxane is formed by the hydrolysis and partial condensation of an alkyltrialkoxysilane with water or a mixture of an alkyltrialkoxysilane and a dialkyldialkoxysilane with water. The liquid polyorganosiloxane cures at room temperature on the surface of the ceramic to form a hard, protective, solid coating which forms a high temperature, oxidation resistant ceramic upon exposure to a high temperature environment, and is also used as an adhesive for adhering a repair plug in major damage to the ceramic. This has been found useful for protecting and repairing porous, rigid ceramics of a type used on reentry space vehicles.

High temperature resistant organopolysiloxane coating for protecting and

Hygroscopic ceramic materials which are difficult to waterproof with a silane, substituted silane or silazane waterproofing agent, such as an alumina containing, fibrous, flexible and porous, fibrous ceramic insulation used on a reentry space vehicle, are rendered easy to waterproof if the interior, porous surface of the ceramic is first coated with a thin coating of silica. The silica coating is achieved by coating the interior surface of the ceramic with a silica precursor, converting the precursor to silica either in-situ or by oxidative pyrolysis and then applying the waterproofing agent to the silica coated ceramic. The silica precursor comprises almost any suitable silicon containing material such as a silane, silicone, siloxane, silazane and the like applied by solution, vapor deposition and the like. If the waterproofing is removed by, e.g., burning, the silica remains and the ceramic is easily rewaterproofed. An alumina containing TABI insulation which absorbs more that five timed its weight of water, absorbs less than 10 wt. % water after being waterproofed according to the method of the invention.

Method for waterproofing ceramic materials

Rigid and flexible porous ceramics, including thermal insulation of a type used on space vehicles, are waterproofed by a treatment which comprises applying an aqueous solution of an organopolysiloxane waterproofing agent having reactive silanol groups to the surface of the ceramic and then heating the treated ceramic to form a waterproofed ceramic. The organopolysiloxane is formed by the hydrolysis and partial condensation of di- and trialkoxyfunctional alkylalkoxysilanes having 1-10 carbon atom hydrocarbyl groups.

Organopolysiloxane waterproofing treatment for porous ceramics

A low-density resin impregnated ceramic article advantageously employed as a structural ceramic ablator comprising a matrix of ceramic fibers. The fibers of the ceramic matrix are coated with an organic resin film. The organic resin can be a thermoplastic resin or a cured thermosetting resin. In one embodiment, the resin is uniformly distributed within the ceramic article. In a second embodiment, the resin is distributed so as to provide a density gradient along at least one direction of the ceramic article. The resin impregnated ceramic article is prepared by providing a matrix of ceramic fibers; immersing the matrix of ceramic fibers in a solution of a solvent and an organic resin infiltrant; and removing the solvent to form a resin film on the ceramic fibers.

Low-density resin impregnated ceramic article and method for making the

A low-density resin impregnated ceramic article advantageously employed as a structural ceramic ablator comprising a fired preform of ceramic fibers. The fibers of the ceramic preform are coated with an organic resin film. The organic resin can be a thermoplastic resin or a cured thermosetting resin. In one embodiment, the resin is uniformly distributed within the ceramic article. In a second embodiment, the resin is distributed so as to provide a density gradient along at least one direction of the ceramic article. The resin impregnated ceramic article is prepared by providing a fired preform of ceramic fibers; immersing the preform of ceramic fibers in a solution of a solvent and an organic resin infiltrant; and removing the solvent to form a resin film on the ceramic fibers.

Low-density resin impregnated ceramic article having an average density

The present invention concerns novel high strength ceramic fibers derived from boron, silicon, and carbon organic precursor polymers. The ceramic fibers are thermally stable at and above 1200.degree. C. in air. The method for preparation of the boron-silicon-carbon fibers from a low oxygen content organosilicon boron precursor polymers of the general formula Si(R.sub.2)BR.sup.1 by melt-spinning, crosslinking and pyrolysis. Specifically, the crosslinked (or cured) precursor organic polymer fibers do not melt or deform during pyrolysis to form the silicon-boron-carbon ceramic fiber. These novel silicon-boron-carbon ceramic fibers are useful in high temperature applications because they retain tensile and other properties up to 1200.degree. C., from 1200.degree. to 1300.degree. C., and in some cases higher than 1300.degree. C.

Ceramic silicon-boron-carhon fibers from organic silicon-boron-polymers

The present invention relates to a process for the production of an organoborosilicon preceramic polymer of the structure: ##STR1## wherein R.sup.1 is selected from alkyl having from 1 to 10 carbon atoms or phenyl, and x is selected from 0, 1, 2 or 3;

Boron-carbon-silicon polymers and the ceramic thereof

The present invention relates to a polyorganoborosilane ceramic precursor polymer comprising a plurality of repeating units of the formula: ##STR1## with the segments being linked together by second units of the formula: --[(R.sup.2)--Si--R.sup.3)--q, where R.sup.1 is lower alkyl, cycloalkyl, phenyl, or ##STR2## and R.sup.2 and R.sup.3 are each independently selected from hydrogen, lower alkyl, vinyl, cycloalkyl, or aryl, n is an integer between 1 and 100; p is an integer between 1 and 100; and q is an integer between 1 and 100. These materials are prepared by combining an organoborohalide of the formula R.sup.4 --B--(X.sup.1).sub.2 where R.sup.4 is selected from halogen, lower alkyl, cycloalkyl, or aryl, and an organohalosilane of the formula: R.sup.2 (R.sup.3) Si(X.sup.2).sub.2 where R.sup.2 and R.sup.3 are each independently selected from lower alkyl, cycloalkyl, or aryl, and X.sup.1 and X.sup.2 are each independently selected from halogen, in an anhydrous aprotic solvent having a boiling point at ambient pressure of not greater than 160.degree. C. with in excess of four equivalents of an alkali metal, heating the reaction mixture and recovering the polyorganoborosilane. These silicon boron polymers are useful to generate high-temperature ceramic materials, such as SiC, SiB.sub.4, and B.sub.4 C, upon thermal degradation above 600.degree. C.

Boron-containing organosilane polymers and ceramic materials thereof

The present invention relates to a polyorganoborosilane ceramic precursor polymer comprising a plurality of repeating units of the formula: ##STR1## with the segments being linked together by second units of the formula: --(R.sup.2)--Si--R.sup.3)--q, where R.sup.1 is lower alkyl, cycloalkyl, phenyl, or ##STR2## and R.sup.2 and R.sup.3 are each independently selected from hydrogen, lower alkyl, vinyl, cycloalkyl, or aryl, n is an integer between 1 and 100; p is an integer between 1 and 100; and q is an integer between 1 and 100. These materials are prepared by combining an organoborohalide of the formula R.sup.4 -B-(X.sup.1).sub.2 where R.sup.4 is selected from halogen, lower alkyl, cycloalkyl, or aryl, and an organohalosilane of the formula : R.sup.2 (R.sup.3) Si(X.sup.2).sub.2 where R.sup.2 and R.sup.3 are each independently selected from lower alkyl, cycloalkyl, or aryl, and X.sup.1 and X.sup.2 are each independently selected from halogen, in an anhydrous aprotic solvent having a boiling point at ambient pressure of not greater than 160.degree. C. with in excess of four equivalents of an alkali metal, heating the reaction mixture and recovering the polyorganoborosilane. These silicon boron polymers are useful to generate high-temperature ceramic materials, such as SiC, SiB.sub.4, and B.sub.4 C, upon thermal degradation above 600.degree. C.

The present invention relates to a method of preparing B-trichloroborazine, B.sub.3 N.sub.3 Cl.sub.3 H.sub.3. Generally, the method includes the combination of gaseous boron trichloride in an anhydrous aprotic organic solvent followed by addition of excess gaseous ammonia at ambient temperature or below. The reaction mixture is heated to between about 100.degree. to 140.degree. C. followed by cooling, removal of the solid ammonium chloride at ambient temperature, distillation of the solvent under vacuum if necessary at a temperature of up to about 112.degree. C., and recovery of the B-trichloroborazine. Solvents include, toluene, benzene, xylene, chlorinated hydrocarbons, chlorinated aromatic compounds, or mixtures thereof. Toluene is a preferred solvent. The process provides a convenient synthesis of a material which often decomposes on standing. B-trichloroborazine is useful in a number of chemical reactions, and particularly in the formation of high temperature inorganic polymers and polymer precursors.

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San Jose, CA, United States of America

Ming-ta S Hsu