Abstract: A re-usable alumina-magnesia graphite refractory suitably used for a refractory for continuous casting, such as a long nozzle used for pouring a molten metal from a ladle capable of re-use or intermittent use to a tundish, an immersion nozzle used for charging a molten metal from a tundish to a mold and a long stopper for controlling the flow rate of the molten steel; and produced by blending 3 to 60 wt % of magnesia having a particle size of 0.02 to 1.0 mm to a compound comprising mainly alumina and graphite, and kneading, molding, and baking the compound. The raw material compound comprising mainly alumina and graphite can contain spinel or zirconia.

Abstract: A dry refractory composition having superior insulating value. The dry refractory composition also may have excellent resistance to molten metals and slags. The composition includes filler lightweight material, which may be selected from perlite, vermiculite, expanded shale, expanded fireclay, expanded alumina silica hollow spheres, bubble alumina, sintered porous alumina, alumina spinel insulating aggregate, calcium alumina insulating aggregate, expanded mulllite, cordierite, and anorthite, and matrix material, which may be selected from calcined alumina, fused alumina, sintered magnesia, fused magnesia, silica fume, fused silica, silicon carbide, boron carbide, titanium diboride, zirconium boride, boron nitride, aluminum nitride, silicon nitride, Sialon, titanium oxide, barium sulfate, zircon, a sillimanite group mineral, pyrophyllite, fireclay, carbon, and calcium fluoride.

Abstract: A low-temperature sinterable ceramic composition which can be simultaneously sintered with a low melting point metal, such as silver or copper, and which has a preferable combination of high strength and superior electrical characteristics. The low-temperature sinterable ceramic composition is formed by mixing a ceramic component comprising an MgO crystal phase and an MgAl2O4 crystal phase and a glass component composed of 13 to 50 wt % silicon oxide, 3 to 30 wt % boron oxide, and 40 to 80 wt % alkaline earth oxide.

Abstract: A continuous process for the synthesis of anionic clays with carbonate and/or hydroxide anions as the charge-balancing interlayer species is disclosed. The process involves reacting a slurry comprising aluminum trihydrate and/or its calcined form, with a magnesium source. There is no necessity to wash or filter the product. It can be spray dried directly to form microspheres or it can be extruded to form shaped bodies. The product can be combined with other ingredients in the manufacture of catalysts, absorbents, pharmaceuticals, cosmetics, detergents, and other commodity products.

Abstract: A sintered ceramic honeycomb article that exhibits an average linear coefficient of thermal expansion (25-800° C.) below about 5.0×10−7° C.−1, a total porosity between the range of 20% to about 30%, and a pore size distribution such that at least about 86% of pores are of a pore size of less than about 2 &mgr;m with the pores exhibiting a generally elongated shape oriented with their long axis in the plane of the webs, the article being made from a cordierite-forming inorganic powder batch comprising a platy talc having median particle of size less than about 2 &mgr;m, at least 4% by weight of a dispersible Al2O3-forming source having a specific surface area in excess of 50 m2/g, and one or more of the components of kaolin, calcined kaolin, silica, and corundum, each having a median particle sizes less than 5 &mgr;m.

Abstract: There is provided a method for producing a beta-alumina solid electrolyte without calcination of starting materials, according to which the step of synthesizing a magnesium-aluminum spinel starting material is not needed and a beta-alumina solid electrolyte of low resistance can be produced at lower cost. According to this method, the beta-alumina solid electrolyte is produced without carrying out calcination of the starting materials by granulating a slurry obtained by milling and mixing starting materials of an aluminum source, a magnesium source and a sodium source in water, molding the granulated product and then firing the molded product. In this method, magnesium hydroxide is used as the magnesium source and an active spinel high in reactivity is synthesized in the course of firing, and citric acid is added to the slurry as a dispersing agent.

Abstract: The present invention relates to methods of producing synthetic crystals (typically minerals) or comparable inorganic compounds by reactions of metal salts and metal oxyhydroxides under near-critical, critical or supercritical solvent conditions, avoiding thereby many of the difficulties associated with conventional solid state or wet chemistry synthesis. The metal oxyhydroxides are typically divalent or trivalent metals and the preferred solvent is typically (but not exclusively) water under near-critical, critical or supercritical conditions. The crystals so produced have a controlled particle size distribution. The crystals produced by the present invention also have morphologies with favorable properties for compaction into green bodies for subsequent sintering into near-net-shapes, approaching maximum theoretical densities. Avoidance of noxious by-products is another advantage of the present synthetic methods.

Abstract: The low thermal expansion and high rigidity ceramic sintered body of this invention is characterized by assuming as a crystal structure a hexagonal close-packed structure and substantially comprising solid solution crystal grains represented by the formula: MgaLibFecAldSieOf (wherein a is in the range of 1.8 to 1.9, b is in the range of 0.1 to 0.3, c is in the range of 0 to 0.2, d is in the range of 3.9 to 4.1, e is in the range of 6.0 to 7.0, and f is in the range of 19 to 23). It is further characterized by the solid solution crystal grains having lattice constants in the ranges, a0 in the range of 9.774 to 9.804 Å and c0 in the range of 9.286 to 9.330 Å, the relative density of the sintered body being of not less than 98%.

Abstract: A light-transmitting (fluorescent) sintered body formed of specific substances different from the prior art materials, solving problems that the performance or efficiency, uses and manufacturing methods are limited which have not been solved with the prior art light-transmitting sintered body and which provides a light-emitting tube and an electric discharge lamp using a light-transmitting (fluorescent) sintered body formed of the specific substance.

Abstract: A method for producing a barium-containing composite metal oxide, comprising calcining a mixture of a barium compound and a metal compound comprising at least one metal selected from the group consisting of magnesium, aluminum, europium, manganese, strontium, calcium, terbium, zinc and titanium, or calcining a barium-containing composite metal salt comprising barium and at least one metal selected from the group consisting of magnesium, aluminum, europium, manganese, strontium, calcium, terbium, zinc and titanium, in a gas comprising a hydrogen halide and water vapor.

Abstract: The present invention is directed at sintered ceramic articles exhibiting a crystalline phase assemblage comprising, by weight, of 65-95% cordierite and 5-35% of a secondary phase selected from the group consisting of mullite, magnesium-aluminate spinel, and sapphirine and having a bulk analytical composition consisting essentially of about, by weight, 32-51% SiO2, 35-49% Al2O3, 7-16% MgO. Furthermore, the ceramic articles exhibit an effective strength of greater than about 3000, a CTE of less than about 15×10−7/° C., over the temperature range of 25° C., to 1000° C., and a total intrusion porosity, as measured by a Hg intrusion method, of at least 20%. This invention also relates to a method for producing a sintered ceramic article having the aforementioned cordierite and secondary minor phase mixture.

Abstract: Ceramics comprising filler crystal particles having an average particle diameter of not smaller than 2.5 &mgr;m and a matrix crystal phase present on the grain boundaries of the filler crystal particles, the filler crystal particles being Al2O3 and the matrix crystal phase being diopside-type oxide crystals precipitated from the crystallized glass. The ceramics has a dielectric loss tangent at 60 to 77 GHz of not higher than 50×10−4, and can be effectively used as an insulating substrate in a wiring board for transmitting high-frequency signals.

Abstract: A graphite-containing monolithic refractory material comprises at least one component selected from alumina and alumina-magnesia spinel, which are divided into selected particle size regions, artificial graphite having a selected average particle size, and pitch powder. The refractory material may optionally comprise a selected amount of silicon carbide having a selected average particle size. The graphite-containing monolithic refractory material exhibits excellent casting workability at a low moisture content, and both excellent corrosion resistance and spalling resistance. The refractory material is suitable as a casting monolithic refractory material for lining a topedo ladle car.

Abstract: Disclosed is sintered ceramic article that exhibits a primary crystalline phase of cordierite and analytical oxide composition, in weight percent, of 49-53% SiO2, 33-38% Al2O3, 12-16% MgO and exhibits a coefficient of thermal expansion no greater than about 4.0×10−7/° C. over the temperature range of about 25° C. to about 800° C. and a transverse-I ratio of not less than about 0.92. Also disclosed is a method for producing a sintered cordierite ceramic article involving preparing a plasticizable raw material, comprising a magnesium source, a SiO2-forming source and an additional component of either: (a) a clay-free, Al2O3-forming source having a surface area of greater than about 5 m2/g; or, (b) a clay and Al2O3-forming source combination wherein the clay comprises no greater than about 30%, by weight, of the total inorganic mixture, and the Al2O3-forming source exhibits a surface area of greater than about 40 m2/g.

Abstract: Disclosed is a high-efficiency stress-luminescent material capable of emitting luminescence by receiving a mechanical stress such as compression, shearing and rubbing. The stress-luminescent material is an alkaline earth aluminate of a non-stoichiometric composition deficient in the content of the alkaline earth element by 0.01 to 20% by moles from stoichiometry. The efficiency of stress-luminescence emission can be further enhanced when the non-stoichiometric alkaline earth aluminate contains 0.01 to 10% by moles of rare earth metal ions or transition metal ions. The stress-luminescent material is prepared by subjecting a non-stoichiometric composite oxide of aluminum oxide and an alkaline earth oxide to a calcination treatment at 800 to 1700° C. in a reducing atmosphere.

Abstract: The process for making the high temperature-resistant ceramic material from the MgO—Al2O3 system includes burning a mixture containing a predetermined amount of magnesium oxide (MgO) of a predetermined grain size distribution in an amount range of from 30 to 99 parts by weight and a predetermined amount of magnesium aluminate (MgAl2O4) of another different predetermined grain size distribution in a range of from 1 to 70 parts by weight to obtain a ceramic product having a thermal expansion coefficient and selecting the amounts of magnesium oxide and magnesium aluminate as well as the predetermined grain size distributions so that the thermal expansion coefficient of the ceramic product is substantially equal to that of platinum and platinum alloys and in a range of from 9×10−6 K−1 to 15×10−6 K−1.

Abstract: The present invention discloses novel magnesia-spinel refractory compositions and bricks formed thereof that exhibit longer lining life, greater hot strength and reduced tendency to spall under high thermal loading conditions. The invention is designed to slow or retard the reaction between spinel and lime through the addition of zirconia in the form of an alumina-zirconia grain to the refractory mix. Zirconia reacts more readily with the lime in the refractory composition and surrounding environment to form calcium zirconate.

Abstract: The present invention provides a magnesia-spinel refractory in which corrosion resistance and slag penetration resistance are significantly improved. The magnesia-spinel refractory is obtained by mixing magnesia granulated powder having a particle diameter of 10 to 150 &mgr;m and alumina powder having a particle diameter of 0.1 to 5 &mgr;m, molding the resultant mixture, and then burning the molded product to form a dense and strong combined structure of periclase and spinel. The mixture of magnesia and alumina contains powders of both components, or a powder of one of the components and a granulated powder of the other component. It is preferable to use a spray dryer method as granulating means, and a hydrostatic pressing method as molding means. These mixtures are used for producing magnesia-spinel protecting tube and crucible, bricks for copper smelting and converting furnaces, and magnesia-spinel protecting tube and crucible for copper smelting and converting furnace slag.

Abstract: A porous spinel type oxide shows a large surface area and a uniform micro-porous structure. The oxide is expressed by general formula MO—Al2O3 and shows a surface area per unit weight of not less than 80 m2/g. Such a porous spinel type compound oxide is obtained by impregnating a specific &ggr;-alumina carrier with a solution of a compound of metal element M capable of taking a valence of 2, drying the impregnated carrier and calcining it at a temperature of 600° C. or higher. The specific &ggr;-alumina carrier shows a surface area per unit weight of not less than 150 m2/g, a micro-pore volume per unit weight of not less than 0.55 cm3/g and an average micro-pore diameter between 90 and 200 angstroms. The micro-pores with a diameter between 90 and 200 angstroms occupy not less than 60% of the total micro-pore volume of the carrier.

Abstract: Ceramic composites containing weak interfacial boundaries included for the purposes of providing avenues for crack deflection with a resulting toughening of a ceramic body. Weak interfacial boundaries are created between constituents of the composite, such as matrix phases and any continuous and/or particulate reinforcements, and tungstate, molybdate, tantalate, and niobate compounds of the general formula ABO4. For tungstate and molybdate compounds of the general formula ABO4, B represents tungsten or molybdenum, and A represents a divalent cation. For tantalate and niobate compounds of the general formula ABO4, B represents tantalum or niobium, and A represents a trivalent lanthanide series cation. The ABO4 tungstate, molybdate, tantalate, and niobate compounds may exist as barrier phases between the matrix and the reinforcements of the composite, or the ceramic body may contain discrete particulates, laminae, fibers, or whiskers of the ABO4 tungstate, molybdate, tantalate, and niobate compounds.

Abstract: A ceramic compound which undergoes martensitic transformation comprises a compound represented by compositional formula Ln1-xSixAlO3+0.5x obtained by substituting a part of LnO1.5 in LnAlO3-type compounds with SiO2, where Ln represents at least one element selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, and x=0.01 to 0.3.

Abstract: There is provided a jig for use in firing of ferrite-made member (e.g. deflection yoke). The jig contains MgO.Al.sub.2 O.sub.3 spinnel as the main component. In the jig, the molar ratio of total MgO and total Al.sub.2 O.sub.3 is 25:75 to 75:25; and RO, which is at least one kind of oxide selected from the group consisting of ZnO, CuO, MnO, NiO, CaO, SrO, BaO, PbO and CdO, is contained in an amount of 0 to 25 mole % per 100 mole % of the sum of total MgO and total Al.sub.2 O.sub.3. This jig is unreactive to a material (e.g. deflection yoke) to be fired and consequently gives rise to no dimensional change of the material to be fired.

Abstract: The present invention relates to a protection tube for protecting heaters and sensors used in melting furnace for reprocessing of incinerator ash, other melting furnace, and various other furnaces, the protection tube being excellent in resistance to heat and resistance to corrosion so as to be usable favorably for a long period. The heat- and corrosion-resisting protection tube is formed in a tubular body closed at an end, being composed of ceramics, and the ceramics have a softening point over 1700.degree. C. in the air atmosphere, a three-point bending strength of 150 MPa or more at 1450.degree. C., a resistance to heat shock of .DELTA.T of 150.degree. C. or more by water quenching method, and a mean grain size of 2 .mu.m or more, having a composition of 50 mol % or more of Al.sub.2 O.sub.3 and 50 mol % or less of MgO.

Abstract: Carbon-containing components of cells for the production of aluminium by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte are protected from attack by liquid and/or gaseous components of the electrolyte in the form of elements, ions or compounds, by a refractory boride coating applied from a slurry composed of pre-formed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

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: A powdered mixture of chemicals for forming a refractory composition, including a filler consisting of refractory particles, metal particles and metal peroxide containing particles, wherein the metal peroxide containing particles have a calcium peroxide content of at most 75 wt %, a magnesium peroxide content of at most 30 wt %, a barium peroxide content of at most 92 wt %, and/or a strontium peroxide content of at most 90 wt %. A refractory composition prepared from said mixture, a method for forming said composition and a method for using same are also disclosed.

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: 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 porous lithium aluminate carrier for catalyst has a spinel structure which has a mean pore diameter in the range of 40 to 1,000 angstroms and a total pore volume in the range of 0.2 to 1.5 mL/g. The porous lithium aluminate carrier can be used for supporting a catalyst compound containing a platinum group metal. The catalyst on the carrier can be favorably employed for promoting catalytic reaction of a nitrite ester and carbon monoxide to prepare a carbonate diester such as dimethyl carbonate.

Abstract: An object of the present invention is to provide a novel ceramic composite that has not only excellent dynamic characteristics, but also good electromagnetic characteristics, typified by dielectric characteristics, and the present invention relates to a ceramic composite, characterized in that an oxide having a perovskite structure which includes as raw materials lead and/or an alkaline earth metal is dispersed in a ceramic matrix, and in the above-mentioned ceramic composite, preferably the ceramic matrix is MgO, MgAl.sub.2 O.sub.4, or ZrO.sub.2, and also, preferably in the above-mentioned ceramic composite, the perovskite structure oxide particles are covered with MgO, MgAl.sub.2 O.sub.4, or ZrO.sub.2, and the ceramic matrix is Al.sub.2 O.sub.3.

Abstract: The present invention pertains to a refractory ceramic mass, consisting of 50 to 97 wt. % of sintered MgO as well as 3 to 50 wt. % of a spinel of the hercynite type.

Abstract: An object of the present invention is to provide an alumina-magnesia oxide which can be fine pulverulent bodies by pulverizing. In the alumina-magnesia oxide of the present invention includes: 70-73 WT % of alumina component, which is converted into alumina (Al.sub.2 O.sub.3); and 27-30 WT % of magnesia component, which is converted into magnesia (MgO). The alumina-magnesia oxide is formed into a pulverulent body, which is a hollow grain having loosed bulk density of 0.15 g/cm.sup.3 or less and average grain diameter of 10 .mu.m or more.

Abstract: A beta-alumina solid electrolyte for use in a sodium-sulfur battery is composed of beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and an aspect ratio of 4.0 or less. The beta-alumina solid electrolyte is composed of the beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and has such a particle diameter distribution that the average particle diameter is 3 .mu.m or less, the proportion of the particles having a particle diameter of 5 .mu.m or less is 90% or more, and the maximum particle diameter is 300 .mu.m or less. A process for producing a beta-alumina solid electrolyte using an alumina source material, a magnesium source material and a sodium source material, uses a magnesium-aluminum spinel as the magnesium source material and subjects all materials to mixing, granulation, molding and firing to obtain a beta-alumina solid electrolyte without subjecting the materials to calcination.

Abstract: A castable refractory which comprises a matrix, making up 100 wt % in total, composed of 3-20 wt % of magnesia clinker having a particle diameter smaller than 0.21 mm and containing more than 95 wt % of MgO and 0.5-3.0 wt % of alumina cement in terms of CaO, with the remainder being alumina, and 0.1-3 wt % of ultrafine powder of amorphous silica and 41-100 wt % of alumina coarse grains having a particle diameter of 10-50 mm, both in terms of outer percentage of the amount of the matrix.

Abstract: A castable refractory which comprises a matrix, making up 100 wt % in total, composed of 3-20 wt % of magnesia clinker having a particle diameter smaller than 0.21 mm and containing more than 95 wt % of MgO and 0.5-3.0 wt % of alumina cement in terms of CaO, with the remainder being alumina, and 0.1-3 wt % of ultrafine powder of amorphous silica and 3-9 wt % of alumina coarse grains having a particle diameter of 8-20 mm, both in terms of outer percentage of the amount of the matrix.

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: Ceramic ferroelectric composite material-BSTO-Magnesia based compounds hag a low dielectric constant, low loss tangent and high tunability are disclosed. The composite material comprises Barium Strontium Titanate (BSTO) and a magnesia compound selected from the group consisting, MgZrO.sub.3, MgAl.sub.2 O.sub.4, and MgTiO.sub.3. The preferred composite is represented by Ba.sub.1-x Sr.sub.x TiO.sub.3 -magnesia compound, wherein x is greater than 0.00, but less than or equal to 0.75, and wherein the percent weight ratio between BSTO and magnesia compound ranges from approximately 99%-40% and 1%-60%, respectively. The novel materials possess superior electronic properties, and they may be employed in various antenna systems.

Abstract: Fused alumina particles are covered with a coating of aluminum titanate which is formed by applying a Ti-containing compound to the surface of the fused alumina particles and firing the same to cause a reaction between the Ti-containing compound and the alumina.

Abstract: A ceramic coating-forming agent of an Mg-M.sup.3+ -O based two-component oxide solid solution capable of forming a ceramic coating excellent in heat resistance, adhesion to a substrate metal, electric insulation and the properties of low thermal expansion, at a low temperature, the agent containing an Mg-M.sup.3+ -O based two-component oxide solid solution of the formula (1),(Mg.sub.1-x M.sup.2+.sub.x).sub.1-y M.sup.3+.sub.y O (1)wherein M.sup.2+ is at least one divalent metal selected from the group consisting of Ca.sup.2+, Mn.sup.2+, Fe.sup.2+, Co.sup.2+, Ni.sup.2+, Cu.sup.2+ and Zn.sup.2+, M.sup.3+ is at least one trivalent metal selected from the group consisting of Al.sup.3+, Mn.sup.3+, Fe.sup.3+, Co.sup.3+, Ni.sup.3+, Ti.sup.3+, Bi.sup.3+ and Cr.sup.3+, x is a number in the range of 0.ltoreq.x<0.5 and y is a number in the range of 0<y<0.5, or an anionic oxide-dispersed Mg-M.sup.3+ -O based two-component oxide solid solution of the formula (2),(Mg.sub.1-x M.sup.2+.sub.x).sub.1-y M.sup.3+.sub.

Abstract: A spout-filling composition has from about 50% to about 70% by weight magnesium-aluminate spinel aggregate, from about 50% to about 30% by weight quartz sand, and lampblack in an additional amount of from about 0.25% to about 5.00% by weight of the magnesium-aluminate spinel aggregate and quartz sand admixture.

Abstract: A beta-alumina solid electrolyte for use in a sodium-sulfur battery is composed of beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and an aspect ratio of 4.0 or less. The beta-alumina solid electrolyte is composed of the beta-alumina crystals having a degree of orientation toward the C axis thereof, of 0.2-0.4 and has such a particle diameter distribution that the average particle diameter is 3 .mu.m or less, the proportion of the particles having a particle diameter of 5 .mu.m or less is 90% or more, and the maximum particle diameter is 300 .mu.m or less. A process for producing a beta-alumina solid electrolyte using an alumina source material, a magnesium source material and a sodium source material, uses a magnesium-aluminum spinel as the magnesium source material and subjects all materials to mixing, granulation, molding and firing to obtain a beta-alumina solid electrolyte without subjecting the materials to calcination.

Abstract: The invention relates to a densely sintered tabular ceramic part of aluminum oxide having improved thermal shock resistance, which possesses a fine porosity of at most 10% by volume, does not contain inclusions having a diameter of .gtoreq.70 .mu.m within the ceramic microstructure and is not destroyed on immersion in a molten metal bath having a temperature of at least 350.degree. C. The invention also relates to a process for producing such a shaped part.

Abstract: The present invention pertains to a refractory ceramic mass, consisting of a pure magnesia component A and a component B, which consists of granules of pure magnesia, wherein the magnesia granules of component B have a ceating consisting of a refractory material whose granule size is fine compared with that of the magnesia granules and is chemically extensively inert with respect to the magnesia granule or reacts with the magnesia granule and/or itself consists of a plurality of components that are chemically reactive with one another.

Abstract: The present invention pertains to a refractory ceramic mass, consisting of 50 to 97 wt. % of sintered MgO as well as 3 to 50 wt. % of a spinel of the hercynite type.

Abstract: The present invention pertains to the use of a refractory ceramic brick based on MgO containing 3% to 23% of a pre-synthesized MgO.times.Al.sub.2 O.sub.3 (MA spinel) with an Al.sub.2 O.sub.3 content of 75 to 95 wt. % for lining cement rotary kilns.

Abstract: Chrome-free bricks which exhibit excellent resistance to corrosion, penetration, and thermal spalling. The bricks are mainly made from a magnesia material and/or a magnesia-alumina spinel material and comprise 1 to 10 wt % titania and 1 to 15 wt % alumina. They may contain 0.5 to 10 wt % iron oxide. Further, they may contain at least one material of the group consisting of 1 to 10 wt % metal powder, 1 to 20 wt % carbon and 1 to 20 wt % one of oxide materials except for iron oxide.

Abstract: The present invention pertains to a refractory brick based on at least one refractory metal oxide in a particle fraction of <8 mm containing 4 to 30 wt. % of a very fine refractory fraction, prepared by firing below a temperature at which the particles of the very fine refractory fraction sinter by recrystallization with grain growth.

Abstract: A magnesia-based beta alumina sintered body having the following features:(1) the average crystalline particle diameter of beta alumina crystals as calculated assuming that the beta alumina crystals are of a circular section is in a range of 1-4 .mu.m;(2) the amount of the beta alumina crystals having particle diameters not more than 5 .mu.m is 85% to 98% when measured in a plane;(3) the maximum crystalline particle diameter is not more than 300 .mu.m, and the number of coarse particles having diameters falling in a range of 100 .mu.m to 300 .mu.m is not more than 1 as counted in an area of 10 mm.times.10 mm; and(4) the content of crystals of sodium aluminate is 0.5 wt % to 6.0 wt %. A process for producing such a magnesia-based beta alumina sintered body is also disclosed.

Abstract: The invention provides a method of making a magnesium/aluminium spinel compound having the formula Mg.sub.(1+x) Al.sub.(2+y) O.sub.4 in which 0.ltoreq.x.ltoreq.0.2 and 0.ltoreq.y.ltoreq.0.35. Particulate aluminium metal and a magnesium-containing component selected from magnesium oxide and precursors thereof are mixed together and heated to 800.degree.-1150.degree. C. in an oxidising environment to cause oxidation of at least part of the aluminium. Further heating then takes place to a temperature of 1150.degree.-1350.degree. C. in the oxidizing environment to cause aluminium oxide and magnesium oxide in the admixture to react together.

Abstract: A method of making a .beta.-alumina compound which is a polyaluminate of the general formula M.sub.y O.multidot.xAl.sub.2 O.sub.3 in which M is a metal selected from monovalent metals and divalent metals, y=2 when M is a monovalent metal, y=1 when M is a divalent metal and x=4-12 comprises forming a green precursor of the 62 -alumina compound by mixing together particulate aluminium metal and a reagent compound comprising an oxide of the metal M or a precursor thereof. The mixture is heated to 800.degree.-1150.degree. C. in an oxidizing environment to cause oxidation of at least part of the aluminium. Further heating then takes place to 1150.degree.-1350.degree. C. in said environment to cause the oxidized aluminium and oxide of the metal M to react to form the .beta.-alumina compound.