Abstract: A large-format fireclay refractory brick for use as bottom block in a tin bath and a method for its manufacture, said brick formed of material of the Al2O3—SiO2 system filling material and opening material. The preferred embodiment of the brick has an upper and a lower layer with the filling and/or opening material contained only in the lower layer. The brick has an open porosity of 20 to 25 percent by volume, a gas permeability of less than 3 nPm and an H2-diffusion of less than 150 mm H2O, resulting in a brick with improved resistance to alkali attack and decreased caloric conductivity.

Abstract: A method of making a whisker-reinforced ceramic body by hot pressing a preform to a disc, cutting the disc into blanks and grinding the blanks to bodies of desired shape and dimension is disclosed. The preform is prepared by dispersing 10-60% by volume of a ceramic powder mixture containing conventional sintering aids and/or grain growth inhibitors in water or an organic solvent adding 1-15 wt-% starch to the dispersion; pouring the dispersion into a mold with desired shape; heating the suspension to 50°-100° C. for 2-4 hours while covering the mold to avoid water evaporation to form a preform; removing the preform from the mold; and presintering the preform in air for 10 h at a maximum temperature of about 600° C.

Abstract: A castable refractory composition comprising: (a) 50-90 vol. % coarse particulates having a particle size between about 1 and 60 mm; and (b) 10-40 vol. % fine filler materials having a particle size distribution of between 0.0001 to 3 mm.

Abstract: A homogeneous alumina-based sintered material having excellent grindability, low porosity and high flexural strength, and which is free of color unevenness and fluctuations in density. Predetermined amounts of Al.sub.2 O.sub.3 powder, MgO powder, CaCO.sub.3 powder and SiO.sub.2 powder are measured out, and then mixed with stirring in a ball mill. The mixture is granulated using a spray dryer, and then hydrostatically pressed to obtain a molded product having a predetermined shape. Subsequently, the molded product is stored and sintered at a temperature of 1,550.degree. C. to 1,650.degree. C., particularly 1,600.degree. C. to 1,650.degree. C. under atmospheric pressure for 2 hours. As a result, an alumina-based sintered material having a 50 percent cumulative grain size distribution in diameter of from 4 to 15 .mu.m, a 90 percent grain diameter of two to three times the 50 percent grain diameter, and a porosity of not more than 5% can be obtained.

Abstract: A repairing material for the bricks of the carbonizing chamber in a coke oven is obtained by compounding mortar as a main component with a powder comprising 70-100 wt. % of a Co compound, Ni compound, and/or Al compound and 0-30 wt. % of at least one compound selected from among the compounds of Ca, Mg, Zn, Sr, Ba, Fe, V, Pb, Cu, and Ti, and a liquid formed of water, B, P, and at least one member selected from among Si, Na, and K. A method for repairing includes hot applying the repairing material to portions of the bricks of the carbonizing chamber in the coke oven which are in need of repair.

Abstract: Alumina-based ceramics are thermally stable because of their high melting point and excellent materials in wear resistant properties and chemical stability. However, they contradictly have such a problem that fracture toughness is low, and its improvement is desired. The present invention provides such sintered alumina-based ceramics and their production process that have rendered to grow alumina grains anisotropically and can simultaneously attain high flexural strength and fracture toughness by sintering the formed mixture comprising Al.sub.2 O.sub.3, 0.05-2.5 mol % of VA metal oxide and 0.01-4 mol % SiO.sub.2, relative to Al.sub.2 O.sub.3, respectively.

Abstract: An insulation material which is substantially free of fibers and which has a density of less than about 2.5 g/cc and a thermal conductivity of less than about 5 W/Km is formed from a composition comprising at least about 2%, by weight, carbon. The insulation material is resistant to thermal shock and is easily machined.

Abstract: A process for strengthening aluminum based ceramics is provided. A gaseous atmosphere consisting essentially of silicon monoxide gas is formed by exposing a source of silicon to an atmosphere consisting essentially of hydrogen and a sufficient amount of water vapor. The aluminum based ceramic is exposed to the gaseous silicon monoxide atmosphere for a period of time and at a temperature sufficient to produce a continuous, stable silicon-containing film on the surface of the aluminum based ceramic that increases the strength of the ceramic.

Abstract: This invention is directed to ceramic metal composite useful as a refractory and having improved abrasion, corrosion, and oxidation resistance. The ceramic metal composite of the present invention is comprised of ceramic refractory aggregate, metal particulate, and a nonaqueous binder wherein the ceramic refractory aggregate, metal particulate, and binder residuals react to form a three-dimensional ceramic-metal matrix. The ceramic-metal matrix is further stabilized by bonds between the metal particulate, reaction products of the metal particulate, and the ceramic refractory aggregate.

Abstract: The present invention provides a ceramic sintered body excellent in oxidation resistance under high temperatures and markedly superior to the conventional ceramic sintered body in the mechanical strength over a wide temperature range of between room temperature and 1,500.degree. C. The ceramic sintered body of the present invention comprises at least one ceramic crystal grain selected from the group consisting essentially of a monosilicate represented by the general formula RE.sub.2 SiO.sub.5, where RE denotes a IIIa group element including yttrium, and a disilicate represented by the general formula RE.sub.2 Si.sub.2 O.sub.7, where RE denotes a IIIa group element including yttrium, and at least one additional element selected from the group consisting of Al, Cr, Hf, Nb, Zr, Ti, V, Ta, Ca and Mg which is segregated in the boundaries of the ceramic crystal grains in an amount of 0.1 to 15% by weight of the sintered body in terms of the oxide thereof.

Abstract: A semiconductive ceramic composition having negative resistance-temperature characteristics, wherein the composition comprises lanthanum cobalt oxide as the primary component, and, as secondary components, at least one oxide of an element selected from B, Fe and Al and at least one oxide of an element selected from Si, Zr, Hf, Ta, Sn, Sb, W, Mo, Te, Ce, Nb, Mn, Th and P. A semiconductive ceramic composition having a resistivity of approximately 10 .OMEGA..multidot.cm to 100 .OMEGA..multidot.cm at room temperature is obtained by controlling the amount of additives. Since the resistivity at room temperature can be enhanced to several times or more that of the conventional compositions while characteristics of the conventional compositions are maintained, the composition may be widely applied to control heavy current.

Abstract: Reaction Bonded Ceramics for Ceramic Composite Materials Comprising Mullite as the Main Component and Corundum and Thortveitite or Cerianite as Minor ComponentsThe present invention pertains to reaction bonded mullite-containing ceramic molded parts, a process for their preparation and their use.A particular embodiment of the present invention consists in reaction bonded mullite-containing ceramic molded parts, obtainable by the heat-treatment of a finely dispersed mixture of an aluminum-containing material, a silicon-containing material, and a rare earth metal-containing material in an oxygen-containing atmosphere.

Abstract: The invention covers a fused cast refractory material essentially consisting of .beta. alumina and having the following chemical analysis expressed as molar percentages:11.25% to 15.45% of at least one alkaline metal oxide selected from the group comprising Na.sub.2 O, Li.sub.2 O and K.sub.2 O provided that Na.sub.2 O represents at least 9.3%,0 to 2.97% SiO.sub.2,81.38% to 88.75% Al.sub.2 O.sub.3, andat most 0.2% impuritiesand in which .beta. alumina represents at least 98% of the crystallized phases.

Abstract: Disclosed is an alumina-based sintered material comprising a magnesium component, a calcium component, a silicon component, and a lithium component, wherein the content of the lithium component in terms of oxide amount is from 0.002 to 0.04% by weight based on the alumina-based sintered material.

Abstract: The invention relates to the field of ceramics and concerns sintered Al.s2 O.sub.3 compositions produced from corundum powder and also methods for the use of the invented compositions as medical implants or tool material. To produce such materials, an initially unsintered precursor having a relative density of .rho..gtoreq.55% is produced from .alpha.-Al.sub.2 O.sub.3 powder having defined properties using at least two different dispersing methods, this precursor is subsequently subjected to heat treatment and sintering.

Abstract: A ceramic material in the lithium aluminosilicate (LAS) system, having a negative coefficient of thermal expansion and improved mechanical properties, the material having a stoichiometric composition of Li.sub.1+X AlSiO.sub.4+X/2, where 0.ltoreq.x.ltoreq.0.1. The ceramic material can be made by mixing silicon and aluminum oxides (SiO.sub.2 and Al.sub.2 O.sub.5) with lithium carbonate (Li.sub.2 CO.sub.3) and calcining the mixture. Alternatively, the ceramic material can be made by mixing silicon oxide (SiO.sub.2), lithium aluminate (LiAlO.sub.2), and, if desired, lithium carbonate (Li.sub.2 CO.sub.3), and calcining the mixture. Alternatively, the ceramic material can be made by mixing spodumene (an inexpensive mineral with a nominal composition of LiAlSi.sub.2 O.sub.6), lithium aluminate (LiAlO.sub.2), and the required amounts of other constituents (Li.sub.2 CO.sub.3, Al.sub.2 O.sub.3, or SiO.sub.2), and calcining the mixture.

Abstract: An improvement in a thermally insulating component for an engine part, made by sintering from ceramic materials, comprises, the thermally insulating component having a composition, consisting of a mixture of zirconium oxide in the range of about 5% to about 25% by volume and mullite in the range of about 75% to about 95% by volume. Further, the mixture of zirconium oxide and mullite is obtained by chemically mixing the zirconium oxide and mullite in their molecular states, rather than mechanically mixing them. Another feature of this invention includes, forming said thermally insulating component by slip casting and pressureless sintering the mixture of zirconium oxide and mullite at a temperature no greater than 1700.degree. C. This improvement in a thermally insulating component for an engine part, made from a mullite-zirconia ceramic composite, embodying the present invention, is particularly useful in making flame decks for cylinder heads, and insulating coverings for pistons and exhaust ports.

Abstract: A process for preparing far-infrared radiating material. More particularly, this invention relates to a process for preparing far-infrared radiating material which makes maximum use of thermal radiation with a higher specific surface area. The present invention comprises the steps of preparing ultra-fine aluminum silicate salt for nucleus material, adding a silicate gel to said nucleus material, and then adding AlCl.sub.3, FeCl.sub.2, and MnCl.sub.2 to resulting mixture and neutralizing the resulting mixture with an ammonia solution. The present invention can be applied to vinyl films for agricultural use, wrappers, paint for cars, drying, heating, facilitation of fermentation, maturation of liquors, medical treatment, etc.

Abstract: A method is now disclosed for the making of compressed refractory fiber shapes, e.g., compressed ceramic fiber shapes, having a textured surface and an aggregate body. The shapes can be obtained by molding and therefore may be simple or complex. For the process, small discrete fragments of refractory fiber in accumulated form are suspended in a colloidal dispersion, such as the colloidal dispersion provided by colloidal silica. Colloidal mixtures, as of colloidal silica with colloidal alumina are also most serviceable. The fragments and the dispersion are mildly mixed so as not to thoroughly disperse the fiber fragments, but rather to form globules of the fiber in the resulting blend. The resulting material is shaped, e.g., molded under pressure, and usually dried while under pressure, which drying can be at elevated temperature.

Abstract: A process for producing monoclinic celsian comprising the steps of forming a mixture of an alkoxide of silica, an alkoxide of aluminum, and a salt of barium; adding a catalyst of a fluorine containing compound to the mixture; calcining the catalyzed mixture; and, heat treating the calcined mixture. This process uses a sol-gel process to progressively increase the amount of monoclinic phase in relation to the hexagonal celsian. Additionally, a process for producing monoclinic strontium aluminosilicate is disclosed.

Abstract: In the ceramics having a low heat conductivity, silicon nitride is contained as a main component, a composite oxide or a separate phase thereof and transition metal elements having 66 to 75 of atomic number are dispersed into a substrate, and a minute layer grown continuous to the substrate is formed on the surface of the substrate. The composite oxide is at least one of 3Al.sub.2 O.sub.3. 2SiO.sub.2, 2MgO.2Al.sub.2 O.sub.3.5SiO.sub.2, 2MgO.SiO.sub.2 and 4MgO.5Al.sub.2 O.sub.3.2SiO.sub.2. The adding quantity of the composite oxide and the separate phase thereof is 15 to 60 wt. % in terms of the composite oxide. The adding component of transition metal elements having 66 to 75 of atomic number is less 10 wt. % in terms of oxide of the transition metal elements.

Abstract: A ceramic composition is provided to insulate ceramic matrix composites under high temperature, high heat flux environments. The composite comprises a plurality of hollow oxide-based spheres of varios dimentions, a phosphate binder, and at least one oxide filler powder, whereby the phosphate binder partially fills gaps between the spheres and the filler powders. The spheres are situated in the phosphate binder and the filler powders such that each sphere is in contact with at least one other sphere. The spheres may be any combination of Mullite spheres, Alumina spheres, or stabilized Zirconia spheres. The filler powder may be any combination of Alumina, Mullite, Ceria, or Hafnia. Preferably, the phosphate binder is Aluminum Ortho-Phosphate. A method of manufacturing the ceramic insulating composition and its application to CMC substates are also provided.

Abstract: Herein disclosed is a filter medium for molten metals which consists of a sintered body of a mixture comprising 100 parts by weight of at least one refractory grain selected from the group consisting of alumina particles and Al.sub.2 O.sub.3.MgO spinel crystal particles; and 5 to 25 parts by weight of an inorganic binder which comprises 60 to 90% by weight of Al.sub.2 O.sub.3.MgO spinel crystal powder, 5 to 12% by weight of B.sub.2 O.sub.3, and not more than 30% by weight of at least one oxide selected from the group consisting of Al.sub.2 O.sub.3, MgO and TiO.sub.2. The filter medium is used for filtering off solid impurities mixed in molten metals, in particular, molten aluminums.

Abstract: Inorganic fibers are disclosed, vacuum preforms of which have a shrinkage of 3.5% or less when exposed to 1260.degree. C. for 24 hours. The fibers have a composition comprising SrO, Al.sub.2 O.sub.3, and sufficient fiber forming additive to allow fiber formation but not so much as to increase shrinkage beyond 3.5%. A preferred range of fibers has a shrinkage of 3.5% or less when exposed to 1500.degree. C. for 24 hours and may comprise (in weight percent): SrO 53.2%-57.6%, Al.sub.2 O.sub.3 30.4-40.1%, SiO.sub.2 5.06-10.1%.

Abstract: There is a process for producing spherical metal-oxide powder particles. They are used as finely ground raw and filler materials in mineral, ceramic and refractory construction, technical and auxiliary materials, as well as for polishing and grinding agents.

Abstract: A cement composition for use in acidic environments containing an acid resistant particulate aggregate of fused mullite aggregate or other aggregate material, with quartz, and microsilica in combination with a colloidal silica sol binder and being substantially free of Na compounds and K compounds which react in the presence of sulfuric acid to form alkali sulfates in service, thus reducing the durability or the service life.

Abstract: Insulating sleeve mixes that contain hollow aluminosilicate microspheres, an organic binder, and boric acid and/or a phosphate, and their uses.

Abstract: A ceramic particulate material which comprises particles having an irregular three dimensional surface profile having jagged projections and a median particle diameter of 200 micrometers or less, the particles being fractals produced by comminution of foamed ceramic material. The material may be such that in a sphere of rotation of the particle, from 30% to 80% of the volume of the sphere is void, the remainder being continuous solid material. The material may be produced by a process which includes providing a suspension of ceramic forming particles e.g., of an aluminosilicate such as clay, in a liquid medium; incorporating a gas in the liquid medium before or after formation of the suspension therein to produce a foamed suspension; extruding the foamed suspension; optionally drying the extrudate formed thereby; calcining the extrudate; and comminuting the calcined material, e.g. by crushing. The material may be used as a substitute for diatomite.

Abstract: There is disclosed a bioceramic matter as small in size as 300-475 mesh, comprising about 60.5-70.5% by weight of silica (SiO.sub.2), about 10.7-13.7% by weight of alumina (Al.sub.2 O.sub.3) and about 10.8-20.8% by weight of an effective-ingredient mix. The effecitive ingredient mix comprises about 1.4-3.4% by weight of ferric oxide (Fe.sub.2 O.sub.3), about 0.3-0.7% by weight of magnesium oxide (MgO), about 0.8-1.6% by weight of calcium oxide (CaO), about 1.5-3.5% by weight of sodium oxide (Na.sub.2 O), about 0.4-2.4% by weight of potassium oxide (K.sub.2 O), about 0.09-0.1% by weight of phosphorous pentoxide (P.sub.2 O.sub.5), about 0.02-0.2% by weight of titanium (Ti), about 0.02-0.2% by weight of manganese (Mn), about 0.02-0.2% by weight of selenium (Se), about 15-25 ppm of germanium (Ge), and about 2.5-3.5% by weight of silver (Ag).

Abstract: Methods of making substantially phase-pure and thermally stable crystalline alumina compositions stabilized with an oxide of silicon, germanium, phosphorus, arsenic or a mixture thereof. Also provided are crystalline alumina compositions and catalyst supports made using these methods.

Abstract: Beta-spodumene bodies and method of preparing the bodies that involves providing a uniform plastic batch of inorganic raw materials, organic binder, and vehicle, wherein the inorganic raw materials are composed of, in percent by weight, about 75% to 95% minerals, and about 5% to 25% glass. The batch is formed into a green body that is fired to produce a body composed substantially of beta-spodumene, and having a thermal expansion coefficient of <10.times.10.sup.-7 /.degree.C.(0-800.degree. C.), and a strength of .gtoreq.4 Ksi.

Abstract: A composite and monolithic refractory structure, particularly adapted for making furnaces for glassmaking or the like, constituted by a block-shaped component made of electro-cast refractory material based on oxides of aluminum, zirconium, silicon, and the like, having shapes and dimensions that are adapted for its uses, inside which at least one protective element is monolithically inserted; the protective element is highly resistant to the attack of molten glass baths or the like and is chosen among metals, noble metals, refractory metals, refractory materials, conventional and non-conventional ceramic materials, such as carbides, nitrides, borides, and the like, or graphite-based materials, alloys and/or compounds and/or composites thereof; the element is provided substantially in the shape of a plate that is shaped and sized so as to have a profile that is similar to the peripheral profile of the refractory block and is arranged, inside the block, so that its surfaces are located at, and proximate to, the

Abstract: The present invention is directed to an insulating coating for refractory articles, adapted to be applied by spraying or gunning, which is easy to apply, cost effective, eliminates the potential health hazards associated with ceramic fiber paper, and which imparts sufficient insulating properties to the refractory article in high temperature environments. More particularly, the present invention is directed to an insulating coating and a method of preparing the insulating coating wherein the coating composition is comprised of about 25% to about 75% by weight of lightweight aggregate, up to about 25% to about 75% by weight of binder, up to 0.5% by weight of organic fiber, up to about 15% by weight of an additive to improve green strength, and up to about 5% by weight of a foaming agent.

Abstract: A ceramic filter for filtering molten metals includes aggregate particles consisting of fused alumina and/or sintered alumina, and a binder material, wherein the binder is present in an amount of 10 to 22 parts, by weight, per 100 parts of the aggregate particles. The binder material consists of 15 to 25%, by weight, of Al.sub.2 O.sub.3, 35 to 52% of B.sub.2 O.sub.3, not less than 7% and less than 15% of Sio.sub.2, and the balance of MgO. The ceramic filter may be prepared by kneading 100 parts of aggregate particles consisting essentially of either or both of fused alumina and sintered alumina, 10 to 22 parts of the foregoing binder material, an appropriate amount of an organic binder and an appropriate amount of water; molding the resulting mixture; drying the molded mixture; and then firing the same at a temperature ranging from 1150 to 1300.degree. C.

Abstract: A refractory castable comprised of:about 45% to about 75% by weight high alumina grain;about 2% to about 35% by weight silicon carbide;about 1% to about 8% by weight carbon;about 1% to about 8% by weight calcium aluminate cement; andabout 1% to about 10% by weight fine magnesium aluminate spinel,the spinel having a grain size of less than about 150 .mu.m (100 Tyler mesh) and being comprised of about 10% to about 33% by weight magnesium oxide (MgO) and about 67% to about 90% by weight alumina (Al.sub.2 O.sub.3).

Abstract: This invention relates to novel ecologically compatible water-based stable mullite precursor sols, mullite composites, and methods for making the same. The mullite precursor sols are synthesized using tetraethoxysilane and aluminum nitrate in water. The tetraethoxysilane is hydrolyzed with water and ammonium hydroxide catalyst to make a silica sol, which is then quenched with an aqueous solution of aluminum nitrate. The mullite precursor sols of the invention may be used to make highly densified ceramic composites.

Abstract: The present invention relates to ceramics and a method for making ceramics having very little dimensional change after sintering and high dimensional accuracies, so that the characteristics of inorganic functional material are fully maintained and utilized. The ceramics of the present invention comprise grains of inorganic functional material and grains of complex oxide. The pores existing between said grains of inorganic functional material are filled with said grains of complex oxide produced by a sintering reaction between an oxidized metal and an inorganic compound.

Abstract: A shaped ceramic article capable of being cut manually into selected sizes and process is based on a mixture of high-temperature resistant ceramic fibers and fibers which soften at temperatures below 2000.degree. F., particles of a ceramic material stable to temperatures exceeding 2000.degree. F., particles of a ceramic material which sinter at temperatures below 2000.degree. F., and a binder which provides green strength to shapes formed by vacuum formation from a slurry. The vacuum formed shape is dried at about 400.degree. F., thereby dried to form a shape which is preferably dipped in colloidal alumina or silica and dried again. The shape is sinterable by contact with flowing molten metal or by being sujected to radiant heat to form a hardened shape-stable ceramic form.

Abstract: The present invention relates to a refractory binder that comprises a mixture of aqueous phosphate and silica sol. The silica sol has been found to gel and set in a surprisingly effective and useful way. Preferably, the refractory binder further incorporates a small amount of magnesia as an accelerator. The present invention also provides a method of binding a refractory material such, for example, as alumina, zirconia mullite or aluminium silicate by using a refractory binder according to the invention.

Abstract: A portable device for carrying with the human body includes a far infrared ray generating composition plate, a magnetic radiating unit, an electronic circuit unit, and a mercury battery disposed on the far infrared ray generating composition plate for self-radiating bioenergy so as to eliminate and reduce human fatigue and stress. The composition of the plate including 24-27 parts by weight of SiO.sub.2, 53-55 parts by weight of Al.sub.2 O.sub.3, 13-15 parts by weight of CaO, 1-4 parts by weight of MnO, 1-3 parts by weight of TiO.sub.2, and 1-2 parts by weight of Ag, the sum of the SiO.sub.2, Al.sub.2 O.sub.3, CaO, MnO, TiO.sub.2, and Ag equalling 100 parts by weight.

Abstract: A granular ceramic is prepared by firing a powder of a natural zeolite mineral, a pre-fired powder composed of shell fragments, a pre-fired powder of a silica-alumina mineral, and a copper oxide powder. When used as a fuel additive, the ceramic makes it possible to improve the combustion efficiency of hydrocarbon oils, especially of petroleum products such as gasoline, gas oil kerosene, and heavy oil, as well as to reduce CO.sub.2 and NO.sub.x emissions in exhaust gases discharged during combustion.

Abstract: A ceramic and method of producing the same are disclosed, the ceramic having as principal ingredients natural zeolite and shells, wherein silver nitrate, magnesium oxide, potassium oxide, sodium oxide selenium oxide and ferric oxide are added thereto, and the resultant mixture fired to produce a granular ceramic. The granular ceramic enables the production of deoxidized water having an appropriately low oxidation reduction potential, for use as drinking water and the like.

Abstract: New thermally- and hydrothermally-stable .delta.-alumina compositions stabilized with an oxide of silicon, germanium, phosphorus, arsenic or a mixture thereof and methods of preparation of same are provided. Also provided are catalyst supports and catalysts made using these stabilized .delta.-alumina compositions, methods for making same, and methods for treating the exhaust gas from an internal combustion engine using such catalysts.

Abstract: A composition suitable for admixture with refractory grains to make a refractory monolithic formulation, consisting essentially of:2 to 10 parts by weight of activated alumina;0.25 to 1.0 parts by weight of an additive material which comprises at least one of an alumino-silicate-phosphate compound; a resin derived from an aldehyde and either an amine or an aromatic hydroxy compound; cellulose; polyethylene glycol(s); and methoxy polyethylene glycols;0 to 50 parts by weight of fine alumina;0 to 10 parts by weight of fine silica;0 to 1 parts by weight of a dispersant; and0 to 1 part by weight calcium aluminate cement.

Abstract: An aluminum oxide based sintered body and a method for manufacturing the same are disclosed. The aluminum oxide based sintered body is composed of silicon compounds in particulate form of from about 5 to about 40 mole %, calculated as a carbide, which is present along grain boundaries as a silicon-containing glass, at least one metal or metal compound of from 0.5 to about 20 mole %, calculated as metals, selected from Ti, Nb, Ta, Cr and Mo, and the remainder of Al.sub.2 O.sub.3, and the molar ratio of the metals with respect to the silicon compounds, calculated as a carbide, is about 4 or less.

Abstract: Spherical metal-oxide powder particles are used as finely ground raw and filler materials in mineral, ceramic and refractory construction, technical and auxiliary materials, as well as for polishing and grinding agents. There is a process for producing the powder particles, and there is a process for treating ceramic and refractory residual materials.

Abstract: Castable refractory for a slide gate plate is mainly formed of alumina raw material and amorphous carbon raw material of 2 to 15 wt %, and contains silicon carbide and/or boron carbide, the total content thereof being equal to 0.5 to 10 wt % (the content of boron carbide is equal to or less than 3 wt %, and when the content of boron carbide is less than 0.5 wt %, silicon carbide is set to 3 wt % or more), 2 to 10 wt % magnesia of 1 mm or less in particle size, 0.2 to 3 wt % silica fine powder of 5 micrometers or less in particle size, and 0.1 to 5 wt % salt of condensate of formalin and aromatic sulfonate.

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 alumina sintered body containing, as impurities, sodium oxide, potassium oxide, silicon oxide, calcium oxide, ferric oxide and titanium oxide in a total amount in the range from 100 to 10000 ppm, in which a total amount of the sodium oxide and potassium oxide based on the total amount of the impurities is not more than 4 wt. %. In the manufacture of the sintered body, its starting powder is admixed with at least an acid compound to produce metal salts by a reaction of the acid compound with metals contained in the starting powder and the resulting metal salts are removed.

Abstract: Composition for a coating protecting the surfaces of carbon-containing products exposed to a hot, oxidizing environment such as the parts of anodes not immersed in the molten salt bath and the liners of the aluminum electrolysis cells and more generally the non-immersed parts of carbon-containing refractory elements used in electrolysis conducted below 950.degree. C. in a molten salt bath, comprising a geopolymer, preferably in the fluoropoly(sialate-disiloxo) family, the other components possibly being water as well as alumina and/or a refractory other than silica. Coating protecting the surfaces of carbon-containing products exposed to a hot, oxidizing environment such as the non-immersed parts of carbon-containing refractory elements used in electrolysis conducted below 950.degree. C. in a molten salt bath, including polysilicates and at least one inorganic polymer in the poly(sialate) family, preferably fluoropoly(sialate-disiloxo), also possibly with alumina or another refractory other than silica.