Abstract: Transparent methyl-modified silica gel is produced by reacting methyltrialkoxysilane or a mixture thereof with a tetraalkoxy-, trialkoxy- or dialkoxysilane other than the methyltrialkoxysilane with a defined quantity of water at a neutral or acidic pH in the presence of a catalytically effective amount of a metal complex soluble in the methyltrialkoxysilane, and aging the resulting hydrolysate sol to form a gel. Self-sustained films of the transparent gel are produced by spreading the hydrolysate sol onto a nonadherent substrate followed by aging or drying. The gel finds use as a host material for doping optically functional molecules.

Abstract: Damage-tolerant, continuous fiber ceramic matrix composites are fabricated to fill the space between the fibers with a powder. The powder particles are heat treated to form a porous framework without shrinkage, which is then strengthened with an inorganic synthesized from a precursor in solution. High particle packing densities is achieved within the fiber preform using a small particle-to-fiber diameter ratio. Filling the interstices with a powder increases the composite density and also limits the size of the crack-like voids within the matrix. The ceramic matrix composite (CMC) has mechanical characteristics similar to those found in wood. It is also affordable and inherently oxidation resistant. The composite is characterized by a heterogeneous distribution of fibers within a porous matrix having a homogeneous, fine porosity. A residual stress from thermal expansion mismatch of the matrix and fibers is created in the composite. The illustrated embodiment uses Al.sub.2 O.sub.

Abstract: An oxide ceramic composite suitable for fabricating components of combustion turbines and similar high temperature environments. The composite is fabricated by dispersing metal particles in a fiber preform and infiltrating the fiber preform with sol-gel matrix precursor material. Alternatively, the metal particles are mixed into the sol-gel matrix precursor material and the preform is infiltrated with the mixture. Later in the fabrication process, the metal particles oxidize and become oxidized metal when the sol-gel matrix precursor material is sintered. The oxidized metal has more volume and mass than the metal particles. As a result, the oxidized metal contributes to increasing the density of the composite so that it is suitable for use in combustion turbines and similar high temperature environments.

Abstract: A process for preparing a stabilized alumina wherein an aqueous slurry of a precursor boehmite alumina is admixed with an effective amount of a stabilizer such as a water-soluble salt of a polyvalent metal cation of Groups IIA and IIIB of the periodic table, the slurry containing the alumina and the stabilizer being aged at a pH of from about 3 to about 9 and a temperature greater than about 70.degree. C. for a period of time sufficient to convert the greater portion of said alumina to a colloidal sol, the colloidal sol being recovered and calcined to produce a stabilized alumina.

Abstract: The invention is directed to a method for producing low sintering fine-particle multicomponent glass powder having a particle size of the primary particle in the nanometer range. The method utilizes microemulsion techniques with subsequent separation of the particles out of the emulsion and calcination for utilization as glass flow having a sintering temperature <900.degree. C. or in a glass flow, for generating thin transparent layers or for generating color decorations on glass, glass ceramic or ceramic substrates after adding a coloring pigment to the glass flow. The microemulsion for producing the nanoscale glass powder particles is generated from a nonionic ambiphilic emulsifier with a component of 10 to 15 percent by weight on the emulsion, from an oil phase having a portion of 50 to 70 percent by weight and a glass precursor-containing aqueous salt solution having a portion of up to 31.3 percent by weight with salt contents of up to 45 percent by weight.

Abstract: An oriented ferroelectric thin film element, which comprises a single-crystal substrate having thereon (a) a first epitaxial or oriented ferroelectric thin film prepared by a gas phase growth method and (b) a second epitaxial or oriented ferroelectric thin film prepared by application of a coating solution of an organic metal compound to the first ferroelectric thin film followed by heating the coated material. The oriented ferroelectric thin film element has a smooth surface and is useful as an optical guide element, light modulation element, etc. The second ferroelectric thin film can be formed by repeating the process of application of a coating solution of an organic metal compound followed by heating the coated material several times. The present invention also discloses a process for preparing the oriented ferroelectric thin film element.

Abstract: A sol-gel glass doped with one or more reagent that provides chemical interactions with diffusible solutes or components in an adjacent liquid or gas phase. The reagent(s), the solutes or the components can be any organic or inorganic compounds or materials of biological origin, including enzymes. The doped sol-gel glass in various forms is useful as an analytical test, chromatographic medium, sensor, catalyst or biocatalyst, electrode or enzyme electrode, and other detection devices.

Abstract: The present invention are methods for preparing hydrous titanium oxide spherules, hydrous titanium oxide gels such as gel slabs, films, capillary and electrophoresis gels, titanium monohydrogen phosphate spherules, hydrous titanium oxide spherules having suspendible particles homogeneously embedded within to form a composite sorbent, titanium monohydrogen phosphate spherules having suspendible particles of at least one different sorbent homogeneously embedded within to form a composite sorbent having a desired crystallinity, titanium oxide spherules in the form of anatase, brookite or rutile, titanium oxide spherules having suspendible particles homogeneously embedded within to form a composite, hydrous titanium oxide fiber materials, titanium oxide fiber materials, hydrous titanium oxide fiber materials having suspendible particles homogeneously embedded within to form a composite, titanium oxide fiber materials having suspendible particles homogeneously embedded within to form a composite and spherules of b

Abstract: A surface treatment, especially for titanium and aluminum alloys, forms a sol-gel film covalently bonded on the metal surface to produce strong, durable adhesive bonds between the metal and an organic adhesive without using toxic chemicals and while significantly reducing or eliminating rinse water requirements of traditional anodizing or etching processes. An aqueous sol containing an zirconium and an organosilane with an organic acid catalyst and alkoxyzirconium stabilizer is applied to etched or grit blasted substrates by dipping, spraying, or drenching, to produce bonds in a single application comparable in strength and performance to standard anodize controls. Parameters affecting performance include the sol composition, the Si/Zr ratio, the ratio of sol ingredients, the concentration of the sol, the carrier solvent, solution age, catalysts, surface pretreatment, application method, curing process, and primer used.

Abstract: A glass with no stria form of defects induced therein is produced by a sol-gel technique. At a sol gelation step, the gelation temperature is maintained constant within the range of .+-.7.degree. C. with respect to the temperature of a sol as charged in a gelation vessel, and the sol is gelated at a constant colloidal particle diameter with no vibrations applied thereto.

Abstract: A precursor, in gel form, of an oxide having the formula (I), BaO.n(Al.sub.2x Cr.sub.2y O.sub.3), where 1.ltoreq.n.ltoreq.6.6, (x+y)=1, and 0.ltoreq.y.ltoreq.0.5, said oxide being derivable from the precursor gel by the application of heat, is prepared by mixing a solution of a barium salt with a solution of an aluminium salt or a solution of an aluminium salt and a solution of a chromium salt, and polymerising the mixture to produce said precursor gel. A mixture suitable for firing to an oxide of the formula (II), BaO.m(Al.sub.2x Cr.sub.2y O.sub.3), where 4.6.ltoreq.m.ltoreq.6.6; (x+y)=1; and 0.ltoreq.y.ltoreq.0.5, comprises at least one of:(a) barium oxide;(b) a clean thermal precursor of barium oxide; and(c) barium mono-aluminate, BaO.Al.sub.2 O.sub.3 ; with at least one of:(A) alumina, Al.sub.2 O.sub.3 ;(B) hydrated forms of alumina, such as boehmite, Al.sub.2 O.sub.3.H.sub.2 O; and(C) a clean thermal precursor of aluminium oxide; and, where y is not zero, with at least one of(D) chromium(III) oxide, Cr.

Abstract: The present invention is neutral-aged hydrophobic organosilicate-modified silica gels and a method for their preparation. The method comprises three steps, where in the first step an organosilicate-modified silica hydrosol is contacted with a strong mineral acid at a pH less than about 1 to form an organosilicate-modified silica hydrogel. In the second step the organosilicate-modified silica hydrogel is aged at a pH within a range of about pH 3.5 to pH 8. In the third step the neutral-aged organosilicate-modified silica hydrogel is contacted with an organosilicon compound in the presence of a catalytic amount of a strong acid to effect hydrophobing of the organosilicate-modified silica hydrogel to form a hydrophobic organosilicate-modified silica hydrogel having a surface area within a range of about 100 m.sup.2 /g to 750 m.sup.2 /g in the dry state.

Abstract: Colloidal compositions based on fillers, sol oxides, poly silicates, and, optionally, pigmenting agents, and their method of production the solid disperse phase not only operates to cross-link but also as an overmatrix incorporating macroparticles therein. The dispersant is finally chemically set with excess setting agent so that the preliminary product can be finalized to the desired material. For this purpose a matrix-like substance of filler-like macroparticles and sol oxide (crosslinling substance) and a buffer are brought together for assisting the formation of the overmatrix and are processed. This substance is pigmentable by introducing a variation mixture into the substance, so that a wide range of characteristics can be obtained. The substance directed at the desired material, namely a hydration and balancing process stage and a subsequent setting and stabilizing process stage.

Abstract: The present invention relates to mat-shaped composites having porosities above 60% and densities below 0.6 g/cm.sup.3, comprising an aerogel and fibers dispersed therein, the aerogel having cracks and the aerogel fragments enclosed by the cracks, whose average volume is 0.001 mm.sup.3 to 1 cm.sup.3, being held together by the fibers. The present invention further relates to processes for producing the composites of the invention and to their use.

Abstract: A bioactive ceramic material for dental fillings and crowns on the basis of calcium phosphate compounds contains crystallites of sparingly water-soluble calcium phosphate compounds in an amorphous, vitreous or polycrystalline matrix of readily water-soluble calcium phosphate compounds, the Ca/P-atomic ratio of the calcium phosphate compounds being altogether <1.65.

Abstract: Supported inorganic membranes capable of molecular sieving, and methods for their production, are provided. The subject membranes exhibit high flux and high selectivity. The subject membranes are substantially defect free and less than about 100 nm thick. The pores of the subject membranes have an average critical pore radius of less than about 5 .ANG., and have a narrow pore size distribution. The subject membranes are prepared by coating a porous substrate with a polymeric sol, preferably under conditions of low relative pressure of the liquid constituents of the sol. The coated substrate is dried and calcined to produce the subject supported membrane. Also provided are methods of derivatizing the surface of supported inorganic membranes with metal alkoxides. The subject membranes find use in a variety of applications, such as the separation of constituents of gaseous streams, as catalysts and catalyst supports, and the like.

Abstract: An organically modified sol-gel method of preparing substantially crack-free aluminosilicates films is provided. Chelated aluminum alkoxide and polydimethylsiloxane are mixed in a 1:1 ratio by weight in a solvent and refluxed at approximately the boiling temperature of the solvent to produce a sol-gel liquid including polymerized aluminosilicates. The sol-gel liquid is cooled to room temperature. Additional solvent is added to the sol-gel liquid to reduce its viscosity. A substrate is coated with the reduced viscosity sol-gel liquid. The coating of sol-gel liquid on the substrate is dried to produce an organically modified aluminosilicates sol-gel film. The sol-gel film is heated, to enhance polymerization of the sol-gel film and to evaporate residual solvent, and then cooled.

Abstract: This invention relates to a process for obtaining pure or mixed oxide zirconia spheres, microspheres or washcoats consisting of:preparing a zirconium solution in water at a concentration, formally expressed as ZrO.sub.2, equal or lower than 400 g/l, starting from a basic zirconium carbonate additioned of conc. nitric acid up to a molar ratio ?NO.sub.3.sup.- !/?Zr.sup.4+ ! between 0.8 and 1.1, and eventually preparing one or more solutions of the other oxides when necessary;preparing a sol of zirconium, eventually mixed to other metals, by a thickening agent and, in the case of spheres and microspheres, of a surface active agent too;dripping the sol into an alkaline gelation bath for obtaining gel spheres or microspheres, or sucking the sol into the honeycomb channels in order to obtain the washcoats, with subsequent gelation with gaseous ammonia;ageing the so obtained gel;rinsing with water down to pH=9-10, only in the case of gel spheres or microspheres;drying and calcining.

Abstract: An improved method is proposed for the preparation of a semiconductor silicon single crystal of N-type by the Czochralski process, which is free from the problem of occurrence of delayed OSFs as defects in the single crystal even after prolonged storage at room temperature based on the discovery that presence of a certain amount of aluminum in the melt of silicon contained in a fused silica glass crucible acts to suppress occurrence of delayed OSFs as a type of defects in the single crystal while copper as an impurity acts adversely in this regard. With a known fact that an about 30 .mu.m thick inner surface layer of the crucible is melted down into the silicon melt during the single crystal pulling-up process, namely, the invention proposes use of a crucible of which the inner surface layer of 30 .mu.m thickness contains aluminum in an average concentration of 40 to 500 ppm by weight while the content of copper is as low as possible not to exceed 0.5 ppb by weight.

Abstract: To produce functional vitrous, preferably colored or colloid-dyed layers, a composition produced by hydrolysis and polycondensation of(A) at least on hydrolyzable silane of general formula (I)SiX.sub.4 (I)wherein the radicals X are the same or different and represent hydrolyzable groups or hydroxy groups, or an oligomer derived therefrom, and(B) at least one organosilane of general formula (II)R.sup.1.sub.a R.sup.2.sub.b SiX.sub.(4-a-b) (II)wherein R.sup.1 is a non-hydrolyzable radical, R.sup.

Abstract: There are disclosed stabilized Ti-Sn-O nanoclusters formed by complexing Ti-Sn-O nanoclusters with a salt of an alpha-hydroxy acid and also complexed nanoclusters with increased charge transfer interaction formed by annealing the complexed nanoclusters. Also disclosed are compositions for protection against ultraviolet radiation in which the nanoclusters are utilized with the usual topical carriers in an amount to give the level of sun protection factor (SPF) desired. Further disclosed is the method of making the nanoclusters involving acid hydrolyzing a titanium alkoxide and then reacting the hydrolyzed alkoxide with a tin halide.

Abstract: A method for producing high surface area, thermally stable, microporous porous ceramic materials involves replacing a portion of the silicon in a sol or gel comprising silica (silicon dioxide) with cations of another metal. The metal-substituted silica sols are dried and fired to yield porous ceramic materials. Similarly, metal-substituted gels are fired to yield porous ceramic materials. When compared with unsubstituted silica materials, the materials thus produced offer advantageous benefits including improved stability in a basic environment, enhanced thermal stability, and advantageous surface properties such as intrinsic negative charge.

Abstract: A silica glass has a structure determination temperature of 1200 K or lower and a hydrogen molecule concentration of 1.times.10.sup.17 molecules/cm.sup.3 or more. The silica glass is used together with light in a wavelength region of 400 nm or shorter.

Abstract: A storage phosphor material comprising a storage phosphor of the kind in which electrons excited by incident ionizing radiation may be trapped in stable trap sites and subsequently released by stimulation such as photostimulation, wherein the phosphor is contained within a host matrix which comprises a sol-gel glass in which the storage phosphor is incorporated as a dopant.

Abstract: A paste for manufacturing ferrite is produced by dissolving the following materials: organometallic compound comprising a metal element Fe (A); organometallic compound comprising a metal element Me (Me herein denotes at least one element selected from the group consisting of Mn, Li, Mg, Ni, Zn, Y and Gd) (B); and at least one material selected from terpenoid carboxylic acid and resins containing the composition of the terpenoid carboxylic acid (C) in organic solvent (D). The paste permits providing a dense and homogeneous ferrite with a good property. Moreover, the use of such ferrite permits producing ferrite thin films. Furthermore, the ferrite with an excellent high-frequency property can be provided by coating and firing the paste of the present invention. The temperature properties of YIG thin film and Gd-substituted YIG thin film of the present invention are shown.

Abstract: A process for producing nano size powders comprising the steps of mixing an aqueous continuous phase comprising at least one metal cation salt with a hydrophilic organic polymeric disperse phase, forming a metal cation salt/polymer gel, and heat treating the gel at a temperature sufficient to drive off water and organics within the gel, leaving as a residue a nanometer particle-size powder.

Abstract: A method for dissolving silica-rich fibers such as borosilicate fibers, fiberglass and asbestos to stabilize them for disposal. The method comprises (1) immersing the fibers in hot, five-weight-percent sodium hydroxide solution until the concentration of dissolved silica reaches equilibrium and a only a residue is left (about 48 hours), then immersing the residue in hot, five-weight-percent nitric acid until the residue dissolves (about 96 hours). After adjusting the pH of the dissolved fibers to be caustic, the solution can then be added to a waste vitrification stream for safe disposal. The method is useful in disposing contaminated HEME and HEPA filters.

Abstract: An active silica gel honeycomb adsorbing body capable of adsorbing humidity and odorous components in a process air having 100% relative humidity. A single-faced corrugated sheet having a wave length of approximately 2.5-6.5 mm and a wave height of approximately 1.3-4.0 mm, a quantity of active silica gel approximately 0.5-3.0 times the weight of inorganic fiber papers and a thickness of approximately 0.1-0.3 mm is laminated to form a honeycomb structure laminated body. The honeycomb structure laminated body is impregnated with an aqueous water glass solution, and is then impregnated with acid and dried to form active silica gel having micropores and mesopores. The micropores and the mesopores have a diameter distributed in the range of not more than 200 .ANG. and a surface area of approximately 300-600 m.sup.2 /g. The active silica gel is adhered in fiber gaps and on the surface of the inorganic fiber paper.

Abstract: A method for forming a low temperature cofired ceramic package which is made using a multi-layered densified spherical powder formed via a sol-gel process. This densified powder is formed from layers of SiO.sub.2 reacted with trimethyl borate. The spherical powder has a preselected particle size and boron content sufficient to render the low temperature cofired ceramic package fully dense, even in the presence of a second phase filler ceramic, at a sintering temperature below 1000.degree. C. Binder material is added to the spherical powder and ceramic filler to form a plurality of tapes. A ceramic assembly is then formed by layering the plurality of tapes upon one another and firing the ceramic assembly at a temperature below 1025.degree. C. to form a fully dense cofired ceramic package. In order to form the multi-layered densified spherical powder, a silica core, which is formed using a sol-gel process, is reacted with trimethyl borate.

Abstract: A method of forming a layered-perovskite bismuth-strontium-tantalum oxide (SBT) ferroelectric material is performed by dissolving a bismuth compound in a first solvent to form a first solution, mixing a strontium compound and a tantalum compound to form a binary mixture, dissolving the binary mixture in a second solvent to form a second solution, mixing the first solution with the second solution to form a SBT precursor solution, evaporating the first and second solvents to form a SBT precursor material and subsequently sintering said SBT precursor material in the presence of oxygen.

Abstract: A fluorescent substance of which main component is comprised from 32 mol % to 35 mol % of silicon element and from 68 mol % to 65 mol % of oxygen element, and in which includes from 10 ppm to 1 wt % of silicon carbide and silicon nitride as an activator. And, a manufacturing method of the fluorescent substance by hydrolyzing silicon alkoxide by using alkali or acid catalyzer under the presence of carbon, and by heat treating the obtained precursor at the temperature of 500.degree. C. to 900.degree. C.

Abstract: Disclosed is a highly light-transmitting dust protective film composed of at least one member selected from the group consisting of transparent gels of oxides, hydroxides, organic group-containing oxides and organic group-containing hydroxides of polyvalent metals, formed by the sol-gel process.

Abstract: A method of making ceramic fibers from a water soluble pre-ceramic polymer solution by forming fibers from a water soluble pre-ceramic polymer solution, drying the formed fibers at a first temperature ranging between 600.degree. C.-750.degree. C. at a temperature heating rate of about 1.degree. C. per minute. Next, raising the first temperature to a second temperature ranging from 800.degree. C.-1000.degree. C. at about 5.degree. C. per minute, and increasing the second temperature to still a third temperature of about 1200.degree. C. at about 10.degree. C. per minute and holding at the third temperature for about 1 hour. Finally, the fibers are cooled to room temperature at a rate of about 5.degree. C. to 30.degree. C. per minute.

Abstract: Disclosed is a highly light-transmitting dust protective film composed of at least one member selected from the group consisting of transparent gels of oxides, hydroxides, organic group-containing oxides and organic group-containing hydroxides of polyvalent metals, formed by the sol-gel process.

Abstract: Magnetically attractable particles comprise a core of magnetic material encapsulated in a metal oxide coating. They may be made by emulsifying an aqueous solution or dispersion of the magnetic material or precursor, and an aqueous solution or sol of a coating inorganic oxide or precursor, in an inert water-immiscible liquid. The aqueous droplets are gelled, e.g. by ammonia or an amine, recovered, and heated at 250.degree.-2000.degree. C. The resulting particles are generally smooth spheres below 100 microns in diameter and often of sub-micron size.

Abstract: An optical element comprising (i) a matrix having an Si--O covalent bond unit, wherein at least part of the silicon atoms of said Si--O covalent bond unit is covalently bonded to an aliphatic hydrocarbon group containing not more than 4 carbon atoms, and (ii) at least one functional material selected from the group consisting of an organic material showing a nonlinear optical effect, a material showing a refractive index-regulating action, and an organic dye for laser oscillation, said functional material being present within said matrix. A functional group is stably held in the matrix and fully manifests its function in the matrix.

Abstract: Gels based on a network of oxygen-bridged metal and/or semi-metal atoms and produced using a hydrolytic sol-gel process are often not homogeneous. Known non-hydrolytic sol-gel processes give rise to gels containing halogen.A novel non-hydrolytic sol-gel process has been found which gives rise to halogen-free and homogeneous gels and to xerogels obtainable therefrom.In this process, one or more compounds (I) from the series of metal or semi-metal alkoxides, oxoalkoxides, amides or oxoamides are condensed, with elimination of carboxylic acid esters or carboxylic acid amides, until gelation occurs with one or more compounds (II) from the series of metal or semi-metal carboxylates or oxocarboxylates in an anhydrous organic solvent containing no hydroxyl groups.Preferred gels and xerogels contain in the network metal or semi-metal atoms from main group and subgroup III to V and from the rare-earth elements.

Abstract: A metod is proposed of obtaining a chemical interaction between at least one reagent trapped in sol-gel glass by doping it with the reagent(s), and diffusible solutes or components in an adjacent liquid or gas phase. The reagents, the solutes or the components can be any organic or inorganic compounds or materials of biological origins including enzymes. The doped sol-gel glass in various forms may be useful as analytical test, chromatographic medium, sensor, catalyst or biocatalyst, electrode or enzyme electrode, or other detection device.

Abstract: A method for producing high surface area, thermally stable, microporous porous ceramic materials involves replacing a portion of the silicon in a sol or gel comprising silica (silicon dioxide) with cations of another metal. The metal-substituted silica sols are dried and fired to yield porous ceramic materials. Similarly, metal-substituted gels are fired to yield porous ceramic materials. When compared with unsubstituted silica materials, the materials thus produced offer advantageous benefits including improved stability in a basic environment, enhanced thermal stability, and advantageous surface properties such as intrinsic negative charge.

Abstract: A tetraethyl orthosilicate-based, sol-gel glass composition with additives selected for various applications. The composition is made by mixing ethanol, water, and tetraethyl orthosilicate, adjusting the pH into the acid range, and aging the mixture at room temperature. The additives, such as an optical indicator, filler, or catalyst, are then added to the mixture to form the composition which can be applied to a substrate before curing. If the additive is an indicator, the light-absorbing characteristics of which vary upon contact with a particular analyte, the indicator can be applied to a lens, optical fiber, reagant strip, or flow cell for use in chemical analysis. Alternatively, an additive such as alumina particles is blended into the mixture to form a filler composition for patching cracks in metal, glass, or ceramic piping.

Abstract: A process for producing inorganic porous materials is disclosed. The materials prepared by this process are favorably applied to producing columns for chromatography, porous filters for separating blood, porous catalysts, or enzyme supports. These materials have interconnected continuous macropores with a median diameter larger than 0.1 .mu.m. A preferred embodiment of said materials contains additionally mesopores in the walls of said macropores, said mesopores having a median diameter between 2 and 100 nm.

Abstract: A slurry is molded from ceramic fibers and/or microparticles to form a soft felt mat which is impregnated with a sol prior to drying the mat. A catalyst for the sol is caused to diffuse into the mat by exposing the mat to the catalyst and subjecting the mat to a soak time during which the catalyst diffuses into the mat and causes the sol to gel. The sol-gel binder forms bonds so that the mat is dimensionally stabilized. The mat is dried to produce ceramic insulation, ceramic insulation having a consistent microstructure and a fully gelled sol-gel binder through its entire thickness.

Abstract: Chemically derived leucite is claimed. The chemically derived leucite is obtained from a stable dispersion of a potassia precursor, an alumina precursor and a silica precursor having a specified dry weight solids content. Chemically derived tetragonal leucite is particularly useful as a component of a dental porcelain.

Abstract: Lightweight, monolithic ceramics resistant to oxidation in air at high temperatures are made by impregnating a porous carbon preform with a sol which contains a mixture of tetraethoxysilane, dimethyldiethoxysilane and trimethyl borate. The sol is gelled and dried on the carbon preform to form a ceramic precursor. The precursor is pyrolyzed in an inert atmosphere to form the ceramic which is made of carbon, silicon, oxygen and boron. The carbon of the preform reacts with the dried gel during the pyrolysis to form a component of the resulting ceramic. The ceramic is of the same size, shape and form as the carbon precursor. Thus, using a porous, fibrous carbon precursor, such as a carbon felt, results in a porous, fibrous ceramic. Ceramics of the invention are useful as lightweight tiles for a reentry spacecraft.

Abstract: The single-layer high temperature coating according to the invention, which is applied in particular on a porous substrate, comprises a high silica glaze gel frit, alumina and an emissivity agent consisting of MoSi.sub.2 or Cr.sub.2 O.sub.3, and has the following composition by weight:gel frit: 45 to 55%;MoSi.sub.2 or Cr.sub.2 O.sub.3 : 25 to 50%;Al.sub.2 O.sub.3 : 5 to 20%.

Abstract: A method for producing high surface area, thermally stable, microporous porous ceramic materials involves replacing a portion of the silicon in a sol or gel comprising silica (silicon dioxide) with cations of another metal. The metal-substituted silica sols are dried and fired to yield porous ceramic materials. Similarly, metal-substituted gels are fired to yield porous ceramic materials. When compared with unsubstituted silica materials, the materials thus produced offer advantageous benefits including improved stability in a basic environment, enhanced thermal stability, and advantageous surface properties such as intrinsic negative charge.

Abstract: A synthetic silica glass powder obtained by calcining a silica gel powder obtained by hydrolysis of a tetraalkoxysilane, said synthetic silica glass powder containing from 1.times.10.sup.-1 to 1.times.10.sup.-4 ppm of boron and having an internal silanol group concentration of at most 150 ppm and an isolated silanol group concentration of at most 5 ppm.

Abstract: The present invention concerns a process for obtaining metal halides, in particular rare earth and/or alkali earth halides. This process consists of forming a homogeneous solution by mixing one or more rare earth and/or alkali earth halogenoalkoxides in an anhydrous organic solvent, and hydrolyzing this solution. The novel materials are obtained at room temperature and are in powder, fibre, film or bulk material form.

Abstract: A thin, room-temperature-curing, ceramic composite for coating and patching etal substrates comprises a sol gel silica glass matrix filled with finely ground particles or fibers, preferably alumina. The sol gel glass is made by adding ethanol to water to form a first mixture, then separately adding ethanol to tetraethyl orthosilicate to form a second mixture, then slowly adding the first to the second mixture to make a third mixture, and making a slurry by adding the finely ground particles or fibers to the third mixture. The composite can be applied by spraying, brushing or trowelling. If applied to patch fine cracks, densification of the ceramic composite may be obtained to enhance sealing by applying heat during curing.

Abstract: In the method described, the degree of agglomeration of the nanometer-size particles can be readily checked, thus enabling dispersions of particles of this kind to be produced with high solids contents. The method calls for the unmodified powder to be dispersed in water and/or an organic solvent in the presence of a low-molecular organic compound including a functional group which can react and/or interact with groups present on the surface of the powder particles. The dispersant may subsequently be wholly or partly removed.