Abstract: The present invention broadly relates to novel aluminum nitride matrix ceramic composite bodies for use as refractory materials and methods for making the same. The refractory materials are useful in environments which are corrosive, erosive, abrasive and/or which generate thermal shock. Such environments include furnaces, and associated apparatus which house or contact molten masses including, for example, molten metals, molten glasses, etc. The preferred method for making the aluminum nitride matrix ceramic composites comprises a directed oxidation of molten metal.

Abstract: A refractory of the invention is used in casting operation, which has good spalling resistance and corrosion resistance. The refractory includes: 0.0357-2.6548 wt % of amorphous silica particles having a specific surface area within a range of 15-30 m.sup.2 /g; 8.8495-28.5612 wt % of alumina particles having a particle diameter within a range of 10-50 mm; 1.3986-18.1715 wt % of at least one of fused magnesia and sintered magnesia, which contains 0.6993-10.9041 wt % of magnesia having a maximum particle diameter under 44 .mu.m; 0.6993-13.630 wt % of alumina cement; and 45.4545-88.1417 wt % of alumina. When the refractory is used, at lease one of fused magnesia and sintered magnesia surrounds the alumina particles, which react together to generate spinel to thereby form micro-crack layer around the alumina particles for preventing propagation of cracks in a refractory structure.

Abstract: A superstoichiometric MgAl.sub.2 0.sub.4 spinel, which can be used, for example, as material for a high temperature crucible, is synthesized by, producing a precursor mixture comprising intimately mixed oxides of the corresponding metals in the spinel. Magnesium is added in a superstoichiometric amount to the precursor mixture. Prior to spinel formation, from one to five percent by weight of a reactive salt containing fluorine and/or boron, based on the metal oxides of the spinel, are added to the precursor mixture, and the doped precursor mixture is mixed for from 0.5 to 3 hours. Finally, the mixed precursor mixture is heated for between 0.5 and 4 hours at a temperature between 1150.degree. C. and 1400.degree. C. to synthesize the Mg.sub.(1+x) Al.sub.2 0.sub.4 spinel which is superstoichiometric with respect to magnesium.

Abstract: A ceramic composite contains one spinel phase and one or more than one oxides phases. The composite is derived from the mixtures of two oxides, A.sub.2 O.sub.3 and BO, with different molar ratio, in which A and B are metallic ions of three and two valences respectively. The oxides are heated at a high temperature to form a composite containing a spinel and residual oxides. The formed spinel and residual oxides also undergo densification under high temperature. After the treatment at high temperature, not only the spinel is formed but also the composite is densified. The performance of the composite is superior in its strength, toughness and high-temperature stability.

Abstract: A method of manufacturing a refractory object which comprises setting basic refractory grains and a polyphosphate into a green shape characterised by the inclusion of minerals which, when the slurry is set and fired, develop spinel linkages.

Abstract: The present invention pertains to the use of a finely divided magnesium oxide micropowder for preparing ceramic masses and moldings.

Abstract: A refractory mix made comprising magnesite having an MgO content of at least about 95 wt. % and fused spinel-zirconia grain comprising 1 to 40 wt. % zirconia and refractory shapes, particularly brick, made therefrom.

Abstract: A process for age-hardening alumina-rich magnesium aluminum spinel to obtain the desired combination of characteristics of hardness, clarity, flexural strength and toughness comprises selection of the time-temperature pair for isothermal heating followed by quenching. The time-temperature pair is selected from the region wherein the precipitate groups have the characteristics sought. The single crystal spinel is isothermally heated and will, if heated long enough pass from its single phase through two pre-precipitates and two metastable precipitates to a stable secondary phase precipitate within the spinel matrix. Quenching is done slowly at first to avoid thermal shock, then rapidly.

Abstract: A sintered alumina abrasive grain comprised of alpha-alumina crystals and a spinel crystalline phase which does not form a continuous phase but is in the form of discrete crystals which are deposited on triple points in alumina crystal boundaries and are substantially uniformly distributed over the abrasive grain. Preferably, the alpha-alumina crystals have an average particle diameter not larger than 1 micron, and the spinel crystalline phase is composed of alumina and an oxide of a metal selected from Ni, Mg and Zn.

Abstract: A composite substrate is provided, which comprises a cordierite-anorthite-boron base composite material and has a microstructure with anorthite included in the cordierite phase. This substrate can be used in the form of a circuit substrate, because it has high-enough mechanical strength, a coefficient of thermal expansion close to that of silicon and a decreased dielectric constant and, moreover, can be sintered at a low temperature.

Abstract: A body of carbonaceous or other material for use in corrosive environments such as oxidizing media or gaseous or liquid corrosive agents at elevated temperatures, in particular in molten salts such as cryolite, is coated with a protective surface coating which improves the resistance of the body to oxidation or corrosion and which may also enhance the bodies electrical conductivity and/or its electrochemical activity. The protective coating is applied in one or more layers from a colloidal slurry containing reactant or non-reactant substances, or a mixture of reactant and non-reactant substances, in particular mixtures containing silicon carbide and molybdenum silicide or silicon carbide and silicon nitride, which when the body is heated to a sufficient elevated temperature reaction sinter as a result of micropyretic reaction and/or sinter without reaction to form the protective coating.

Abstract: A plastically deformable mixture and method for making a body from the mixture are disclosed. The mixture is composed of powder materials, which when fired form as predominant phases: ceramic, glass-ceramic, glass, and combinations thereof, 0 to an effective amount of burnout agent, water, organic binder which can be cellulose ether, cellulose ether derivatives or combinations thereof, and hydrophilic and hydrophobic additives, to increase the wettability and/or lubricity of the mixture. One advantageous composition for ram extrusion is composed of ceramic-forming powders, water, and in percent by weight based on the powders, about 2% to 8% organic binder which can be methylcellulose, methylcellulose derivatives, and combinations thereof, about 0.3% to 1.0% sodium stearate, and about 0.5% to 2.0% oleic acid.

Abstract: A refractory mix and resultant shapes formed by burning the mix, the mix comprising a magnesia-alumina spinel grain containing at least 27% MgO by weight, a fused magnesite grain, and up to 10% by weight alumina, it being possible to substitute a sintered magnesite grain for up to 50% by weight of the fused magnesite grain.

Abstract: A known relatively dense composite refractory material has a matrix of a refractory material and a dispersed phase in the form of particles of a ceramic material, each dispersed particle comprising an agglomerate of strongly bonded microcrystals, which exhibit strong thermal expansion anisotropy and do not crack spontaneously on cooling from about 1600.degree. C. to ambient temperature. The thermal shock resistance of this composite refractory material is improved by (a) ensuring that the matrix material comprises from 5 to 90 percent by volume of grains having a diameter in the range of from 15 micrometers to about 80 micrometers, and/or (b) including at least one thermal down-quench of from 50.degree. C. to 1500.degree. C. in the final cooling step in the production of the composite refractory material. Alumina is a typical matrix material, with monoclinic zirconia as the dispersed phase.

Abstract: Ceramic products consisting principally of cordierite and a method for making them are provided, the method employing batches comprising a mineral component and a chemical component, the mineral component comprising clay and talc and the chemical component consisting essentially of a combination of the powdered oxides, hydroxides, or hydrous oxides of magnesium, aluminum and silicon. Ceramics made by extrusion and firing of the batches can exhibit low porosity, high strength and low thermal expansion coefficients.

Abstract: Alumina-spinel monolithic refractory having excellent spalling resistance, corrosion resistance and slag penetration resistance. The alumina-spinel refractory contains an alumina-spinel clinker having a MgO:Al.sub.2 O.sub.3 molar ratio ranging from 0.14:1.86 to 0.6:1.4 which can be simultaneously used with a spinel clinker having a close to theoretical composition with the balance consisting of an alumina material and alumina cement. Also, in order to inhibit the elongation of cracks an alumina crushed grain having a grain size ranging from 10 to 50 mm can be added to the alumina-spinel monolithic refractory.

Abstract: The present invention relates to a refractory for casting process composed mainly of 0.3 to 10 wt % light burned magnesia, 3 to 30 wt % micro fine calcined alumina, and the remainder of either sintered alumina, fused alumina and MgO-Al.sub.2 O.sub.3 spinel or sintered alumina and MgO-Al.sub.2 O.sub.3 spinel or fused alumina and MgO-Al.sub.2 O.sub.3 spinel.

Abstract: The invention concerns a fired magnesia-carbon shape having a combination of properties making it especially suitable for slide gate plates, inserts for such plates and for pouring nozzles useful in casting aggressive steels. The fired refractory shape is formed from a batch consisting essentially of, by weight percent,2 to 8 finely divided graphite (natural or synthetic);3 to 8 aluminum metal powder;1 to 5 of finely divided silica and/or a silicon yielding powder;an effective amount of carbon bond forming resins;and the balance coarse and fine magnesia grains.The magnesia grains should contain less than about 0.02 weight percent boron oxide. After firing, the shape is characterized by a carbon bonding system including a spinel (magnesia-alumina) phase plus aluminum carbide bonding the magnesia-carbon matrix. The refractory shape is preferably carbon impregnated after firing to further enhance its properties.

Abstract: A method for producing a transparent polycrystalline magnesia-alumina spinel body having high ultraviolet transmissivity and high strength and hardness characteristics is provided. A closed porosity body is formed from a spinel powder preferably having at least minimum purity characteristics. The closed porosity body can be formed by techniques including hot pressing and pressureless sintering. The closed porosity body is subjected to a hot isostatic pressure treatment to reduce residual porosity. The resulting body has high transmissivity of electro-magnetic radiation in the range between about 0.2 microns and about 6 microns and is resistant to abrasion or erosion, has high strength, and does not substantially deteriorate after exposure to ultraviolet light.

Abstract: A method for the synthesis of mixed metal oxide crystalline powders comprises the steps of preparing a raw material mixture containing at least two different metal cations; adding a template material to the mixture and blending it therewith; initiating formation of a mixed metal oxide by calcination of the mixture and the template material, whereby particles of the mixed metal oxides are formed; and thereafter recovering the mixed metal oxide particles. Mixed metal oxide crystalline powders comprise a template material; and metal oxides which form pigment classes of material containing the template material, the pigment classes being selected from the group consisting of borate, garnet, olivine, phenacite, phosphate, priderite, pyrochlore, sphene, spinel and zircon, as well as perovskite crystal classes of material containing the template, all of which have a uniform particle morphology and particle size ranging between about 0.2 to 100.mu. with minimal comminution.

Abstract: The present invention relates to methods for producing self-supporting ceramic and ceramic composite bodies having a protective surface region on at least a portion of the surface of the formed bodies, and bodies produced thereby.

Abstract: A high density, shock resistant ceramic comprising from 1 to about 4 mols of a a dense spinel ceramic matrix having dispersed therein, 1.5 to 1, respectively, of a metal oxide derived from a decomposable salt of said metal and having a thermal expansion characteristic different from said dense spinel ceramic matrix and at the decomposition temperature a volume less than that exhibited by its salt form and a process for preparing same.

Abstract: A process for producing structures from synthetic single-crystal pieces having identical major component and crystal systems by chemically bonding to produce integration and simulation. The process of the present invention makes structures of synthetic single-crystals that are placed together like non-crystals. Therefore, with the process of the present invention, new synthetic single-crystal structures of larger or smaller complicated precise shapes having applications in optical, chemical, and physical fields may be produced. The structures from synthetic single-crystal pieces are comprised of a plurality of colorless synthetic single-crystals or colored synthetic single-crystals having the same prime component and either no color or color impurities contained therein.

Abstract: Hard crystalline sintered ceramic products, and a method for making them at substantially reduced sintering temperatures, are disclosed, the products being manufactured by the sintering of mixtures comprising one or more ceramic powders selected from among zirconia, stabilized zirconia, partially stabilized zirconia, alumina, mullite, cordierite, and MgAl.sub.2 O.sub.4 spinal together with a combination sintering aide including TiO.sub.2 and at least one transition metal oxide selected from the group consisting of copper oxide, manganese oxide, cobalt oxide and zinc oxide, the mixture comprising at least about 3.5 mole percent TiO.sub.2, at least about 1.3 percent of transition metal oxides, about 4.8-50 mole percent total of TiO.sub.2 +transition metal oxides, and the remainder ceramic powder. Sintering of these mixtures at temperatures typically 200.degree.-350.degree. C.

Abstract: A magnesia-alumina type spinel clinker contains Fe.sub.2 O.sub.3 and TiO.sub.2 at boundaries between crystal grains, and a refractory produced by using the clinker has excellent corrosion resistance and cement coating properties. The refractory can thus be applied to the fields of cement rotary kiln refractories, refractories for iron making, steel making and nonferrous refining and the like.

Abstract: The present invention relates to methods for producing self-supporting ceramic and ceramic composite bodies having a protective surface region on at least a portion of the surface of the formed bodies, and bodies produced thereby.

Abstract: A Group IIA metal-Group IIIA metal-silicon substantially homogeneous liquid alkoxide is prepared from a reaction mixture of a Group IIA metal, a Group IIIA metal, a silicon tetraalkoxide, and a liquid defined by the formula ROR' where R is an alkyl group and R' is hydrogen or an alkyl group. The alkoxide can then be hydrolyzed, azeotropically distilled, dried, milled, and calcined to produce a ceramic powder. Advantageously, the ceramic powder can be compacted and sintered at relatively low temperatures which enable it to be used in electrical applications where high sintering temperatures would be deleterious.

Abstract: A high alumina ceramic composition has controlled small amounts of MgO and CaO. When refractories made from the composition are fired, the alumina and MgO react to form spinel. The CaO promotes such reaction while minimizing undesirable expansion, and results in a refractory having significantly improved hot strength and other desirable physical properties.

Abstract: The process of the invention consists in co-sintering a fine-grain alumina (8,9,10) with a metallizable alumina (11,12). The component obtained has dielectric properties which are homogeneous in its useful part (8,9,10) and its metallizable parts (11,12) permitting the assembly thereof very solidly with metallic components (1).

Abstract: A composition containing MgAl.sub.2 O.sub.4, SiC, and B.sub.4 C is produced by the method comprising:(a) combining sources of magnesium silicate, B.sub.2 O.sub.3, Al and C to form a mixture, and(b) heating the mixture whereby the sources react to form MgAl.sub.2 O.sub.4, SiC, and B.sub.4 C.A sintered material containing MgAl.sub.2 O.sub.4, SiC, and B.sub.4 C, may be produced by the method comprising:(a) combining sources of magnesium silicate, B.sub.2 O.sub.3, Al and C to form a mixture,(b) compacting the mixture into a shape,(c) heating the shape, whereby the sources react to form MgAl.sub.2 O.sub.4, SiC, and B.sub.4 C, and(d) sintering the reacted shape.Possible sources of magnesium silicate are talc, vermiculite and mica.

Abstract: A body is disclosed which is at least about 90% by weight cordierite, and has a coefficient of thermal expansion of less than about 16.times.10.sup.-7 /.degree.C. from about 25.degree. C. to about 1000.degree. C. Also disclosed is a method of fabricating the body. Raw materials are selected to form a nominal composition consisting essentially of in percent by weight about 11.5 to about 16.5 MgO, about 33.0 to about 41.0 Al.sub.2 O.sub.3, and about 46.5 to about 53 SiO.sub.2. The raw materials can be a combination of silica and magnesium aluminate spinel, a combination of silica, magnesium aluminate spinel, and a MgO yielding component, or a combination of silica, magnesium aluminate spinel, and a Al.sub.2 O.sub.3 yielding components. The raw materials are provided absent of clay and talc. The raw materials are blended with an effective amount of vehicle and forming aids to impart plastic formability and green strength thereto form a plastic mixture.

Abstract: A method to produce an article of commerce comprising a self-supporting ceramic body by oxidation of a molten parent metal with a vapor-phase oxidant, includes applying to a surface of the parent metal a layer having at least one dopant material therein. The layer is thin relative to the thickness of the ceramic body. Upon heating the parent metal to a molten state in the presence of the oxidant, e.g., air, an oxidation reaction product is formed on the molten metal which, because of the effect of the dopant material, migrates through the growing oxidation reaction product so as to be exposed to the oxidant to form additional oxidation reaction product to and beyond the depth of the applied dopant material layer. Suitable temperature and oxidizing conditions are maintained for a time sufficient to produce a self-supporting ceramic body.

Abstract: For producing moldings composed of cordierite, a batch, which gives the composition of cordierite and contains clay and/or kaolin as well as soapstone and/or talc and also water and an organic aid, is subjected to shear mixing. For this purpose, the batch is placed between 2 bodies, which are at a small distance and move relative to one another, and at the same time the batch is subjected to a shear stress. Preferably, the batch is filled into the gap formed by 2 almost touching cylindrical shear rollers which rotate at different speeds or run in opposite directions. The batch is then deformed to give a molding, and the molding is fired until the cordierite phase is formed.Cordierite bodies of very low coefficients of thermal expansion (for example at most 1.1.times.10.sup.-6 /.degree.C. in all three spatial directions) can be obtained.

Abstract: A surface-strengthened composite ceramic material has a ceramic matrix and a refractory phase dispersed at least in and close to the surface of the matrix. The refractory phase includes beta-alumina particles in which larger cations producing a larger molar volume replace sufficient smaller cations in beta-alumina particles in and close to the surface of the composite ceramic material to cause compressive surface stresses which increase the surface strength of the composite ceramic material. The smaller cations are replaced by the larger cations after firing of the composite ceramic material.

Abstract: Compositionally triphasic nanocomposite gel is made by mixing two or more sols of ceramic precursor oxides. Such gel is then dried and ground to a fine powder which is pressed into compact bodies. The compact bodies are thereafter fired in a sintering oven at from 1100.degree. C. to 1400.degree. C. and, aided by the heat of reaction of the two or more nono gel powders, the (heterogeneous) mixture of such powders crystallizes into a homogeneous crystalline ceramic of .alpha.-cordierite at up to 100% of theoretical density. Thus, novel method of manufacture and novel ceramic end-product are provided.

Abstract: Fused cast refractory moldings having a random microstructure, which are near in size and configuration to the desired final shape, and process and apparatus used in their manufacture are described. The process includes rapid melting of the refractory material followed by controlled rapid cooling. Laminated composite fused cast refractories may be produced.

Abstract: A method of fine-tuning the dielectric constant value of an insulating ceramic alloy, and the resulting alloy, and uses thereof, are disclosed. The alloy has the general formula:Mg.sub.x Al.sub.y Ti.sub.z 04whereinx+y+z=3x=1-2y=0.1-1.9z=0.1-0.9and can be made from 10 to 90 mol percent of magnesium titanate and 90 to 10 mol percent of magnesium aluminate. The mol ratio of the titanate to the aluminate in the alloy is varied in order to vary the value of the dielectric constant of the alloy.The alloy can be used in applications such as a dielectric plate for ceramic filters for cellular telephones.

Abstract: A refractory composition for forming shaped refractories comprising from about 60 to 85% by weight of a dead-burned magnesite and, correspondingly, about 15 to 40% by weight of a magnesia-alumina spinel grain; said refractory having a total lime and silica content of about 2 to 4% by weight and a lime-to-silica ratio (CaO:SiO.sub.2) greater than about 1.

Abstract: A transparent polycrystalline body having high ultraviolet transmissivity is provided. The body is preferably a sintered magnesia-alumina spinel body having a transmittance of at least 85 percent in the wavelength range from 0.3 microns to 0.8 microns and a transmittance at some wavelength in the wave length range between about 0.2 and about 0.4 microns of at least about 86 percent and a porosity of less than about 0.001 percent. The sintered body is produced by a two-step method comprising forming a closed porosity body from a spinel powder and subjecting the closed porosity body to a hot isostatic pressure treatment. The resulting body has high transmissivity of electromagnetic radiation in the range between about 0.2 microns and about 6 microns, is resistant to abrasion or erosion, does not substantially deteriorate after exposure to ultraviolet light, and has high strength.

Abstract: An alumina-spinel monolithic refractory consists essentially of 50-90 percent by weight of alumina clinker, 5-40 percent by weight of MgO--Al.sub.2 O.sub.3 spinel clinker not larger than 1 mm in size and 1-25 percent by weight of alumina cement. Another alumina-spinel monolithic refractory consists essentially of 50-90 percent by weight of alumina clinker, 5-40 percent by weight of MgO--Al.sub.2 O.sub.3 spinel clinker, 1-25 percent by weight of alumina cement and not more than 5 percent by weight of magnesia clinker. The alumina-spinel monolithic refractories are used for lining the inner walls of ladles, vacuum degassing vessels, hot-metal mixers, blast-furnace troughs and their covers, not-metal mixer cars, tundishes and the like.

Abstract: A transparent polycrystalline body having high ultraviolet transmissivity is provided. The body is preferably a sintered magnesia-alumina spinel body having a transmittance of at least 85 percent in the wavelength range from 0.4 microns to 0.8 microns and a transmittance at some wavelength in the wavelength range between about 0.2 and about 0.4 microns of at least about 86 percent and a porosity of less than about 0.001 percent. The sintered body is produced by a two-step method comprising forming a closed porosity body from a spinel powder and subjecting the closed porosity body to a hot isostatic pressure treatment. The resulting body has high transmissivity of electromagnetic radiation in the range between about 0.2 microns and about 6 microns, is resistant to abrasion or erosion, does not substantially deteriorate after exposure to ultraviolet light, and has high strength. A number of applications of the magnesia-alumina spinel body are disclosed for which the material is advantageous.

Abstract: The present invention is in a sintered molding of partially stabilized zirconium oxide having a microstructure of 40 to 70 volume percent cubic phase, 30 to 70 volume percent tetragonal phase, and up to 10 volume percent monoclinic phase wherein the tetragonal phase is present in the form of precipitates less than 200 nm. A mixture of magnesia and yttria is used to stabilize the zirconia. Optionally, the sintered molding may further contain up to 20 wt. % spinel.

Abstract: A refractory brick for use in rotary cement kilns has improved properties by the addition of small quantities of MnO.sub.2 to the composition used to form the brick.

Abstract: A refractory mix for forming an in situ magnesium aluminate spinel brick consisting essentially of about 65 to 95 wt. % magnesite having an MgO content of at least about 92 wt. % and, correspondingly, about 35 to 1 wt. % calcined bauxite having an alumina content of at least about 83 wt. % and a silica content of no more than about 7 wt. %, the total silica content of the mix being no more than about 4 wt. % and a magnesium aluminate spinel refractory shape prepared by pressing and firing the above refractory mixture. The invention also comprises the process of forming the refractory.

Abstract: A method of fine-tuning the dielectric constant value of an insulating ceramic alloy, and the resulting alloy, and uses thereof, are disclosed. The alloy has the general formula:Mg.sub.x Al.sub.y Ti.sub.z O.sub.4whereinx+y+z=3x=1-2y=0.1-1.9z=0.1-0.9and is preferably made from 10 to 90 mol percent of magnesium titanate and 90 to 10 mol percent of magnesium aluminate. The mole ratio of the titanate to the aluminate in the alloy is varied in order to vary the value of the dielectric constant of the alloy. The alloy has a density which is at least 98% of the theoretical density of the alloy, and a dielectric constant of 8.5 to 13.8.The alloy can be used in applications wherein dielectric materials have previously been utilized, such as a substrate for an electrical circuit.

Abstract: A dome and window for missiles and launch tubes is provided having high ultraviolet transmittance and high strength properties. The domes and windows have, in their uncoated state, and with a thickness of about 1.88 mm, a transmittance greater than about 80%, preferably greater than about 82%, and more preferably greater than about 85%, at a wavelength of 0.4 microns to 0.5 microns. The domes and windows preferably have a transmittance per 1.88 mm thickness at all wavelengths in the wavelength range between 3.0 microns and 4.0 microns of at least about 81%. The domes and windows have a flexural strength of at least about 20,000 psi and a knoop hardness of at least about 1350 kg mm.sup.-2. The domes and windows are formed of a transparent, sintered polycrystalline magnesia-alumina spinel.

Abstract: A multilayer printed circuit board comprises plural insulating layers integrated into one body, and internal wiring conductor layers located on the internal insulating layers, characterized in that conductor paths in each internal conductor layer are locally separated from the insulating layer by a cavity or porous layer provided at the boundaries between the path and insulating layer adjacent thereto. At least one insulating layer between internal conductor layers may be provided with a layered space or porous layer therein.

Abstract: In processes of forming a refractory mass on a surface, a mixture of refractory particles and oxidizable particles which react exothermically with oxygen to generate sufficient heat to soften or melt at least the surfaces of the refractory particles are sprayed against that surface to bring about formation of said refractory mass. To promote the reliable and consistent formation of a durable refractory mass, the granulometry of the particles which are sprayed in the mixture is such that the 80% and 20% grain sizes of the refractory particles (that is, the screen mesh sizes G.sub.80 and G.sub.20 through which respectively 80% and 20% by weight of the particles will pass) have a mean greater than the mean of the 80% and 20% grain sizes of the oxidizable particles and the size range spread factor f(G) of the refractory particles is at least 1.

Abstract: A method for producing a self-supporting ceramic composite structure comprising a ceramic matrix embedding a filler, includes oxidizing a parent metal to form a polycrystalline material comprising the oxidation reaction product of the parent metal and, optionally, one or more metallic constituents. The method includes heating the parent metal to provide a source of molten parent metal and a reservoir of molten metal which is in communication with the parent metal having a chemical composition which is different from the parent metal and contacting the molten parent metal with a permeable bedding of filler. The molten parent metal reacts with the oxidant to form the oxidation reaction product and is replenished by the reservoir as the reacting continues for a time sufficient to grow the oxidation reaction product to a desired extent and thereby embed at least a portion of the bedding of filler within the oxidation reaction product to form the ceramic composite structure.

Abstract: A refractory composition comprising a fused silica composition comprising a silica compound and a binder and for each 100 parts by weight of said fused silica composition from about 3 to 15 parts by weight of alumina-silica based hollow microspheres.