Abstract: The present invention relates to ceramic bodies suitable for use in high temperature applications such as molten metal filters and kiln furniture. The ceramic bodies are formed from partially stabilized zirconia and are characterized by the presence of from about 12% to about 80% by weight zirconia in a monoclinic phase and the balance essentially in a cubic phase at room temperature. The ceramic bodies possess an excellent combination of physical properties including high temperature strength and thermal shock resistance. The invention also relates to the process for forming the ceramic bodies and the thixotropic ceramic slurry used therein.

Abstract: Ultra-fine hollow glass spheres suitable as a filler in light-weight composite materials for building use and the like can be prepared from a fine powder of volcanic glass even when the starting powder has a particle size as fine as 20 .mu.m or smaller. The inventive method comprises an acid-leaching treatment of the starting powder using hydrochloric or sulfuric acid under hydrothermal conditions at 150.degree.-200.degree. C. to modify the chemical composition in the surface layer of the particles and a subsequent heat treatment of the acid-treated particles at a specified high temperature to effect expansion by the water vapor produced from the structural water in the softened particles. By virtue of the modified composition in the surface layer and in contrast to the prior art method without the acid treatment, a good balance can be obtained between the rate of water vapor release and softening of the particles even when the particle size is extremely small to facilitate expansion of the particles.

Abstract: A process for producing calcium phosphate ceramics having a porous surface is described, which comprise the steps of:a) preparing untreated calcium phosphate ceramics, which comprises a mixture of hydroxyapatite and tricalcium phosphate, andb) treating said untreated ceramics with an acidic solution to selectively dissolve the tricalcium phosphate in the surface of the ceramics.

Abstract: There is disclosed a porous inorganic material suitable for use as a support for immobilizing biological macromolecules and which comprises a 3-dimensional network of defect aluminium-silicon spinel, said network defining an interconnecting array of pores predominantly in the size range of from 100 to 1000 .ANG..A process for preparing the porous inorganic material is also disclosed.

Abstract: A method of physically and chemically altering asbestos which comprises mixing the asbestos with a selected metal and reacting the mixture to form an end product including slag, in which the asbestos has been altered allowing its safe disposal or its formation into useful products.

Abstract: Alkali metal source comprises a powder of silicon or germanium grains having a shell of a compound of silicon or germanium and the alkali metal.

Abstract: Shaped refractory products, particularly in the form of hollow spheres, and a process for their formation. The process involves dispersing particles of silica or a metal oxide, e.g. Al.sub.2 O.sub.3, in an organic polymer, shaping the dispersion into a desired shape, heating the shaped dispersion in a non-oxidizing atmosphere to carbonize the polymer, and heating the carbonized product at high temperature in a non-oxidizing atmosphere containing nitrogen so that some of the oxide is converted to the corresponding nitride and the particles of unreacted oxide sinter together. The ratio of oxide to carbon should be high so that some but not all of the oxide is converted to the nitride and, preferably, only a relatively small amount should be converted. The resulting refractory material is strong and can be used for a variety of uses, e.g. catalyst supports, packing materials and insulating materials.

Abstract: A method for producing shaped heat-insulating bodies based on water-insoluble oxidic metal compounds particularly of the elements silicon and aluminum, clouding agents and other additives, whereby the bodies are thermally hardened and have a heat conductivity of 0.02 to 0.1 W/K.m at temperatures of approximately 300.degree. to 500.degree. C. and are comprised of (a) 100 parts by weight of water-insoluble oxidic metal compounds having a BET-surface of 10 to 700 m.sup.2 /g, with the provision that at least 5% by weight of these compounds have a BET-surface of at least 50m.sup.2 /g; (b) 0 to 100 parts by weight of mineral clouding agents having at least one absorption maximum in the wave length range of 1.5 to 10 .mu.m; and (c) 0.1 to 30 parts by weight of elements capable of forming a solid oxide having a standard formation enthalpy of less than minus 900 kJ/Mol. In addition, 0-100 parts by weight of mineral fibers can be added.

Abstract: Cellular glass structures are made by foaming select silicone resins. A foaming agent is reacted together with the silicone resin to form a foam that carries the resin as a continuous separate phase distributed throughout the foam. The foaming agent is removed by decomposition, and the remaining silicone resin is crosslinked to retain the foamed structure. The silicone resin is then heated in a non-oxidizing atmosphere at a temperature that will pyrolize the resin. During pyrolysis, the resin densifies to foam a unique glass composition comprised of silicon, oxygen and carbon, where carbon is chemically bonded to silicon, but there are essentially no chemical bonds between carbon and oxygen.

Abstract: An improved ceramic foam filter for use in filtering molten metal prepared from a ceramic slurry containing silicon carbide and a colloidal silica binder. The filter has a solids content of at least 50% silicon carbide and at least 3% of silica.

Abstract: An alumina porous body which comprises coarse alumina particles as a filler and SiO.sub.2, said alumina and SiO.sub.2 forming an Al.sub.2 O.sub.3 -SiO.sub.2 compound (mullite) on the surface of the coarse alumina particles through the reaction between them that takes place at the time of firing, said compound binding said coarse alumina particles, forming pores between them. The invention also relates to a process for producing an alumina porous body which comprises mixing coarse alumina particles with SiO.sub.2, molding the mixture, and firing the molding at a temperature not higher than 1700.degree. C., thereby sintering the coarse alumina particles.

Abstract: A porous ceramic material composed of a sintered porous body of a calcium phosphate compound is described. A multiplicity of capillary void paths having a diameter of 1 to 30 .mu.m and a multiplicity of pores having a diameter of 1 to 600 .mu.m are formed in the sintered porous body. At least part of the pores are connected to the exterior space of the sintered porous body through at least a part of the capillary voids. The porous ceramic material is valuable as a medical material, e.g., a substitute or prosthesis for bone or dental root, and also an electronic material and a genetic engineering material.When the porous ceramic material is embedded in a bone defect of human or animals, osteolytic cells, osteoblasts, erythrocytes and body fluid are selectively allowed to intrude through the porous ceramic material while almost no intrusion of osteoclasts and collagen fibers is allowed.

Abstract: An osteofiller is characterized by using columnar sintered hydroxy-apatite having at least one capillary tube passed therethrough in the vertical direction.

Abstract: A water-permeable ceramic material is made of a porcelain particulate material as the principle component, one or more primary binders selected from starch adhesives, organic binders, clay and water glass, and one or more secondary binders selected from frit, glaze and glass powder. The principal component is selected from one or more porcelain materials including a fired mixture of pottery stone, kaolin and feldspar; porcelain wastes, and other porcelain materials such as road-surfacing porcelain color aggregates, and is classified to have a particles are of relatively high bulk density and very low porosity. The mix is shaped by a pressing machine to a tabular or tubular form suited to the specific use of the final product. The pressure of the pressing machine is adjusted to an amount of 30-200 kg/cm.sup.2. After shaping, the resultant compact is sintered at a temperature up to the melting point of the porcelain particles to produce the ceramic material.

Abstract: There is provided a porous cellular material comprising a plurality of cavities each defined by a substantially spherical wall formed of a rigid intermeshing matrix of ceramic needles said wall being pierced by at least one aperture to provide access to the cavity, and the or each aperture having a diameter such that the ratio of the diameter of the aperture to the diameter of the cavity into which the aperture opens is in the range of from 0.1:1 to 1:1.

Abstract: There is disclosed a process for preparing a porous inorganic material. The process comprises preparing a cellular aluminosilicate material by foaming or spray drying an aqueous suspension of the material. The cellular material is calcined, leached with hydroxide to remove silica, dewatered and dried to leave a porous, cellular ceramic material.

Abstract: A composite structure including fibers embedded in a silica glass matrix is made by first forming a precursor of the structure by embedding the fibers in a matrix of a silica-based glass material which further includes a glass-forming additive that lowers the working temperature range of the material below that of pure silica glass, and by leaching the additive out of the glass matrix material. The thus obtained porous glass matrix may then be consoidated at an elevated temperature that is considerably lower than that which would be needed for manufacturing the glass matrix directly from a material having substantially the same composition as the material of the leached-out glass matrix.

Abstract: The present invention relates to ceramic bodies suitable for use in high temperature applications such as molten metal filters and kiln furniture. The ceramic bodies are formed from partially stabilized zirconia and are characterized by the presence of from about 12% to about 80% by weight zirconia in a monoclinic phase and the balance essentially in a cubic phase at room temperature. The ceramic bodies possess an excellent combination of physical properties including high temperature strength and thermal shock resistance. The invention also relates to the process for forming the ceramic bodies and the thixotropic ceramic slurry used therein.

Abstract: A method for producing a porous sintered apatite material comprising the steps of:sintering a calcium-excess apatite at 800.degree. C. or more so as to form a sintered apatite material having a calcium oxide content of from 0.5 to 60 wt % by phase separation of calcium oxide; andremoving the calcium oxide from the sintered apatite material so as to form a porous sintered apatite material.

Abstract: Porous ceramic greenware comprising finely divided ceramic filler, finely divided metal, and polyolefin controls shrinkage in fired shape. In a preferred embodiment the metal and ceramic filler are bound together with the clean burning polyolefin and a plasticizer. After molding the mixture into the final shape, the plasticizer is removed to introduce porosity into the shaped article. Next the article is heated to decompose the polyolefin which can exit as a gas through the pore openings. Finally, the article is fired to a high temperature to oxidize the metal to metal oxide which becomes sintered with the ceramic filler particles to form a sintered porous article where the oxidized metal bonds the filler particles together in the desired shape.

Abstract: The method of making a foamed, low density shaped refractory product consisting of TiB.sub.2 and Al.sub.2 O.sub.3 which comprises the steps of foaming an exothermic reaction mixture consisting of TiO.sub.2, B.sub.2 O.sub.3 and Al, loading the reaction mixture into a self sustaining shape, locally igniting the shaped reaction mixture in air at ambient conditions and recovering the foamed, low density, shaped refractory product.

Abstract: Porous green ceramic parts may be prepared by componding 90 to 60 weight percent of a particulate ceramic material with 10 to 40 weight percent, on a dry basis, of a latex of a polymer. The compound is frothed, shaped and set. The green part may then be sintered. The process avoids the expense of preparing solid ceramic compounds containing waxes or sawdust which burn out to create voids. The process is useful to prepare ceramic filters, catalysts, or light weight metal ceramic foams.

Abstract: The invention relates to a method of manufacturing permeable mineral membranes.The method of the invention is characterized in that a thin layer of gel of peptised hydroxide of at least aluminum is deposited on a permeable perous substrate and the resulting membrane is dried and fired at a temperature between 500.degree. and 1100.degree. C.The resulting membranes can be used for isotopic separation of gases or for filtration and ultrafiltration.

Abstract: Three dimensional hydrophobic substantially inorganic porous structure comprises a myriad of cavities interconnected by holes in which the diameters of the cavities are in the range of from 0.5 to 100 .mu.m and the diameters of the holes are in the range of from 0.1 to 20 .mu.m the porosity of the structure having a narrow pore size distribution with the cavities having a pore volume of at least 2 cc/g for a predetermined 10 .mu.m range of sizes. The structure is preferably an inorganic oxide selected from the group comprising alumina, silica, titania, zirconia and mixtures thereof. The structure is preferably made from an oil-in-water emulsion with a silylating agent in the internal phase so as to render the structure hydrophobic.

Abstract: An improved ceramic foam filter for use in filtering molten metal prepared from a ceramic slurry containing silicon carbide and a colloidal silica binder. The filter has a solids content of at least 50% silicon carbide and at least 3% of silica.

Abstract: The alkali metal content of unfired porous ceramic shapes is substantially reduced by treatment with water to remove excess alkali and treatment with a dilute aqueous solution of an ammonium salt, preferably ammonium chloride, to exchange ammonium ion for remaining alkali metal ion, such that, upon firing, porous ceramic articles are produced having improved stability in high temperature and/or temperature-cycled environments.

Abstract: A ceramic aggregate for concrete is made from a mixture of clay and dried organic garbage in a ratio of about three parts by volume of organic garbage to about one part by volume clay. The mixture is shaped into pancake-shaped pellets and fired at a temperature in excess of the vitrification point of the clay to cause the surface of the pellets to melt and harden the pellets.

Abstract: New type porous cordierite ceramics having a new characteristic interconnecting open cellular structure and a hollow microspherical cordierite glass powder with a shell devoid of any pores or provided with a few or an abundance of open pores which is used as a starting material for the porous cordierite ceramics. The porous cordierite ceramics are produced by subjecting a starting solution containing an alkyl silicate, an aluminum salt and an magnesium salt optionally with other compounds in an organic or aqueous organic solvent to spray thermal decomposition to prepare the hollow microspherical cordierite glass powder, and then processing the cordierite glass powder to a shaped body after or before an optional heat treatment and firing the shaped body at a temperature below the melting point of cordierite. The porous cordierite ceramics are useful as a carrier for gas chromatography or various chemical reactions.

Abstract: The present invention relates to a ceramic foam material, preferably a ceramic foam filter, prepared by providing an open cell flexible foam having a plurality of interconnected voids surrounded by a web of the flexible foam, applying an adhesion promoting material to at least one surface of the flexible foam, impregnating the flexible foam after applying the adhesion promoting material with a ceramic slurry, drying and heating the impregnated material to remove the organic component therefrom, and firing at an elevated temperature to form the filter. In a preferred embodiment, a flocked coating is formed on at least one surface of the flexible foam prior to impregnation. The flocked coating may be formed either by first applying a solution containing an adhesive to the surface(s) and thereafter applying fibers to the surface or by applying a solution containing the adhesive and the fibers.

Abstract: This invention relates to the high temperature stabilization of aluminum titanate and aluminum titanate-mullite compositions by the addition of iron oxide. It has been found that iron oxide concentrations greater than 5 weight percent and as high as approximately 25 weight percent have a stabilization effect at high temperatures on aluminum titanates. The resultant ceramic body is further enhanced by the addition of from 0.1 to 5 weight percent rare earth oxide.

Abstract: A ceramic core for use in the investment casting of metals includes, prior to sintering, about 80 w/o to about 86 w/o of a ceramic filler material and about 14 w/o to about 20 w/o of a binder material. The ceramic filler material includes about 66 w/o to about 95 w/o Al.sub.2 O.sub.3 particles, about 1 w/o to about 20 w/o Y.sub.2 O.sub.3 particles, about 1 w/o to about 5 w/o of a grain growth inhibiting agent, and the balance a carbon-bearing fugitive filler material. Subsequent to sintering, the ceramic core has a microstructure characterized by the presence of substantially unreacted Al.sub.2 O.sub.3 particles having a polycrystalline composition consisting essentially of 3Y.sub.2 O.sub.3.5Al.sub.2 O.sub.3 on the surfaces of the Al.sub.2 O.sub.3 particles.

Abstract: A fluid-permeable article which permits fluid to pass therethrough includes a porous ceramic structure having a multiplicity of hollow members made of ceramic material which are concatenated with each other to form a framework having a continuous capillary passageway system. A continuous space is formed outside of the framework and is defined by the outer surfaces of the hollow members. A continuous matrix material fills the continuous space outside of the framework and cooperates with the porous ceramic structure to provide an integral composite structure consisting of the ceramic material and the matrix material. The continuous passageway system is open in at least a portion of the exposed surfaces of the article and permits fluids to pass therethrough.

Abstract: A refractory mix for forming low thermal conductivity refractory shapes comprising about 50 to 90% by weight of magnesite, about 10 to 50% by weight spinel or about 7 to 35% by weight of an alumina-bearing material, and about 1 to 10% by weight of a nonsiliceous void-forming material.

Abstract: A particulate porous material suitable for use as a high surface area column packing material comprises particles substantially all of which are not smaller than 5 micrometers and not larger than 1 millimeter in diameter, and each particle is in the form of a substantially cellular body and consists predominantly of an open, three-dimensional matrix of crystals of mullite which define between them interconnecting pores having a width in the range of from 5 nanometers to about 2 micrometers. The particles can be coated with a reactive layer. There is also disclosed a process for producing the particulate porous material wherein a particulate product comprising particles substantially all of which are between 5 micrometers and 1 millimeter in diameter and consisting predominantly of a mixture of mullite crystals and silica is treated with a concentrated aqueous solution of an alkali metal hydroxide at a temperature of at least 50.degree. C.

Abstract: A particulate porous material suitable for use as a high surface area column packing material comprises particles substantially all of which are not smaller than 5 micrometers and not larger than 1 millimeter in diameter, and each particle is in the form of a substantially cellular body and consists predominantly of an open, three-dimensional matrix of crystals of mullite which define between them interconnecting pores having a width in the range of from 5 nanometers to about 2 micrometers. The particles can be coated with a reactive layer. There is also disclosed a process for producing the particulate porous material wherein a particulate product comprising particles substantially all of which are between 5 micrometers and 1 millimeter in diameter and consisting predominantly of a mixture of mullite crystals and silica is treated with a concentrated aqueous solution of an alkali metal hydroxide at a temperature of at least 50.degree. C.

Abstract: Ceramic foams in which the open cells are connected by a three-dimensional, substantially continuous ceramic matrix formed of interconnected hollow ligaments, are made from an open-cell, reticulated precursor metal, i.e. a metal foam. The precursor metal first is treated so as to allow a support coating to form thereon, and thereafter the coated precursor is heated above the melting point of the metal in the presence of an oxidant to form an oxidation reaction product.

Abstract: Disclosed herein are a highly strong implant material having continuous passages in the two-dimensional direction, which is a ceramic material of hydroxyapatite and is useful as the substitutive material for bones in the fields of surgery and orthopedics or the filling material in the cavities of bones in the fields of dentistry and oral surgery, and a process for producing the implant material.

Abstract: A novel process for producing clay derivatives having porous structure comprises hydrolyzing a metal alkoxide such as Al(OR).sub.3, Ti(OR).sub.4 and Si(OR).sub.4 in which each R represents a linear or branched hydrocarbon group having from 1 to 6 carbon atoms, deflocculating the resulting hydrolyzate with an acid to obtain a hydrous metal oxide sol, and reacting the sol with smectite.The thus obtained porous clay derivatives have larger interlaminar interstices and a larger surface area than conventional ones. The interstices can be arbitrarily controlled by the acid amount. In addition, the derivatives are thermally stable so that they can be widely utilized in various fields as pigments, encapsulating agents, adsorbents, catalysts, carriers for catalysts and the like.

Abstract: A ceramic composition to make cement with insulating properties is a mixture of cement, ceramic grog and ceramic aggregate beads, the ceramic grog and aggregate being a mixture of clay and dried organic mulch. After firing, the resulting ceramic product is porous. When added to the cement, the porous ceramic grog and aggregate greatly enhance the insulation qualities of the resultant cement structure. The dried organic mulch is formed from pellets produced from commercially reclaimed garbage.

Abstract: A porous silicon carbide sinter and its production process, the sinter consisting mainly of silicon carbide and having a three-dimensional network structure composed mainly of silicon carbide plate crystals having an average aspect ratio of 3 to 50 and an average length along the direction of the major axis of 0.5 to 1,000 .mu.m, wherein the open pores in the network structure have an average sectional area of 0.01 to 250,000 .mu.m.sup.2.

Abstract: A hybrid fiber-reinforced plastic composite material comprising a matrix of a plastic and hybrid fibers consisting of inorganic fibers and at least one kind of fibers selected from the group consisting of carbon fibers, glass fibers, boron fibers, aramide fibers and silicon carbide fibers having a carbon core, wherein(a) the inorganic fibers are inorganic fibers containing silicon, either titanium or zirconium, carbon and oxygen and being composed of(i) an amorphous material consisting substantially of Si, M, C and O where M represents Ti or Zr, or(ii) an aggregate consisting substantially of ultrafine crystalline particles with a particle diameter of not more than 500 .ANG. of .beta.-SiC, MC, a solid solution of .beta.-SiC and MC and MC.sub.1-x, and amorphous SiO.sub.2 and MO.sub.2, where M is as defined and x is a number represented by 0<x<1, or(iii) a mixture of the amorphous material (i) and the aggregate (ii),(b) the composite material has an interlayer shear strength of at least about 9 kg/mm.sup.

Abstract: A process for fabrication of refractory insulating materials wherein essentially pure silica shells are mixed with a polymeric graphite precursor dissolved in a solvent. The resulting slurry is placed in a forming mold, and the solvent is evaporated to form a polymeric matrix containing the shells as a dispersion. This matrix is pyrolized under an inert or reducing atmosphere to decompose the polymer and form a first product consisting essentially of a carbon matrix containing a dispersion of silica shells. To enhance refractory characteristics, such first product is fired at high temperature in an inert or reducing atmosphere to form a second product consisting of a carbon matrix containing a dispersion of SiC-lined voids, or in a nitrogen atmosphere to form a third product consisting of the carbon matrix containing a dispersion of Si.sub.3 N.sub.4 -lined voids.

Abstract: A foamed ceramic body comprising at least 90% by weight of a ceramic composed of 60 to 80% by weight of SiO.sub.2, 5 to 15% by weight of Al.sub.2 O.sub.3, 8 to 14% by weight of an alkali metal oxide, and 1 to 10% by weight of CaO; and a process for producing the said foamed ceramic body, which comprises mixing 100 parts by weight of a powdery mixture composed of 75 to 90% by weight of a volcanic material, 5 to 15% by weight of an alkali metal oxide or compound which forms an alkali metal oxide on heating and 2 to 10% by weight of CaO or a compound which forms CaO on heating, uniformly with 0.1 to 1 part by weight of a blowing agent, and heating the mixture to a temperature of 800.degree. to 1100.degree. C.

Abstract: A porous ceramic filter consisting of a planar porous support formed of a ceramic material, and a filtering layer formed of a fired mass of a ceramic powder integrally deposited on an upper surface of the porous ceramic support. A particle size of the ceramic powder, and a size of macro pores formed in the fired mass of said ceramic powder, decrease substantially continuously in a direction from the upper surface of the ceramic support toward an exposed surface of the filtering layer.

Abstract: A porous refractory hard metal composition is disclosed which is formed by removing the metal compound from a substantially interwoven matrix composition comprising one or more refractory hard metals and a metal compound. The interwoven matrix composition, in a preferred embodiment, may comprise Al.sub.2 O.sub.3 and TiB.sub.2, ZrB.sub.2, or a mixture of the two refractory hard metals.

Abstract: A porous material made from sintered inorganic particles. It has an open pososity of 30% to 40% by volume, a permeability to water at 20.degree. ranging from 0.6 to 60 m.sup.3 /h.m.sup.2.bar for a wall thickness of 2 cm as the average pore diameter varies from 2 to 20 microns and a crushing resistance, measured under conditions of isostatic compression, of 4.times.10.sup.8 to 5.times.10.sup.8 N/m.sup.2.

Abstract: A high porosity silicocalcareous mass is obtained by using in at least partial replacement of the usual silica, amorphous ultrafine synthetic silica particles having a specific surface between 150 and 300 m.sup.2 per gram, and a high absorption capacity, and optionally adding nonreactive synthetic fiber of either inorganic or organic origin to the mixture containing the particles. The high-porosity silicocalcareous mass can be used as a lining material for containers, which are intended for storing liquified or dissolved gases and also as an insulation material, such as sound insulation in building construction.

Abstract: The present invention relates to a technique for forming silicon carbide coated porous filters for use in filtering molten metal, especially copper and copper alloy melts. The technique comprises preparing a silicon carbide containing slurry having a viscosity in the range of about 1 to about 50, preferably from about 5 to about 30, centipoise and impregnating a rigid porous substrate material with the slurry. In a preferred embodiment, the slurry contains mono-aluminum phosphate as a binding agent, ethylene glycol as a wetting agent, powdered silicon carbide having a maximum settling rate of about 0.1 mm./min. and the balance essentially water. After draining of the excess slurry, the coated substrate material is heated to substantially prevent foaming of the coating during firing and fired to bond the silicon carbide coating to the substrate material.

Abstract: A two-phase ceramic particulate useful as a proppant in hydraulic fracturing operations is provided which comprises a vitreous matrix phase containing a crystalline alumina phase. The new ceramic particles are characterized by:(i) a concentration gradient of alumina which increases from very low in the center to relatively high near the surface of the particles;(ii) a fired density less than about 2.9 g/cc; and(iii) closed cell microporosity.Certain embodiments of the inventive ceramic particulate are also characterized by a Krumbein roundness of at least 0.8 and are chemically stable.The ceramic is made by a process comprising the steps of:a. mixing and pelletizing, with the aid of water, the dry raw materials including a mineral particulate such as nepheline syenite and a binder such as bentonite;b. drying the wet pelletizer product;c. mixing the dried pellets with a parting agent; andd.

Abstract: Ceramic, porous filter body in the designed to overcome the lack of high temperature resistant thermoshock resistant and mechanical stable bodies for the filtration of metals, preferentially of iron and ferrous alloys. This filter body has a temperature resistance of 1600.degree. C., a linear thermal coefficient of expansion of 3-7.times.10.sup.-6 /.degree.C. and consists of hollow spheres based on minimum one homogeneous distributed refractory material and another refractory material, which at high temperature by chemical reaction forms with the hollow spheres a solid refractory binding phase. A process for the production of such a filter body is described such, that the spheres of the refractory materials are mixed with a powderous binding phase, then formed to a porous body and then, by retention of the porous homogeneous structure under formation of new refractory compositions by heat treatment are chemically reacted, at least in the contact areas of the spheres.