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

Abstract: A process for increasing the colorizing effect of known colorizing oxides in an alumina body. The process includes the steps of (a) forming a glass frit containing colorants; (b) mixing the frit and alumina to form a green mixture; and (c) firing the mixture to form a fired ceramic body.

Abstract: The invention relates to a refractory part for a device for regulation or interruption of a jet of steel, characterized in that it is formed from a refractory material essentially consisting ofa) 61 to 77% by weight of grains having an alumina content of more than 50% by weight and a melting point higher than 1800.degree. C., andb) 39 to 23% by weight of a binding phase having a X-ray diagram in which the most intense lines are the lines characteristic of a sialon of the formula Si.sub.6-z Al.sub.z N.sub.8-z where z ranges from 2.5 to 4.Application in particular as plate in a slide closing device.

Abstract: A process is presented for the fabrication of a metal/ceramic composite by a non-vapor phase oxidation of a molten metal by contacting said molten metal at an elevated temperature with a sacrificial ceramic preform. The shape of the preform is retained but the ceramic preform is reduced, oxidizing the molten metal. A preferred sacrificial ceramic preform is silica, but can also be, for example, mullite, titania or zirconia, and the preferred molten metal is aluminum or an aluminum alloy. Thus, for example, is produced from immersing a silica preform into molten aluminum alloy, an Al/Al.sub.2 O.sub.3 composite metal/ceramic article which does not contain silica or silicon and which is extremely tough.

Abstract: A method of producing a refractory material of the non-shaped type is disclosed. Refractory aggregates and a binder are mixed ensuring cohesion by chemical bonding. The mixture is shaped and fired. A charge comprising refractory particles of a polymodal granulometric distribution is mixed with a liquid binder consisting of a mixture in an aqueous medium of polysilicate-based mineral polymers and a mineral polymer comprising sialate groups. The paste obtained is shaped and after hardening of the mixture at a temperature between ambient temperature and 200.degree. C., the hardened mixture is brought to a temperature between 200.degree. and 1300.degree. in order to obtain a refractory material having high mechanical properties, high resistance to thermal shock and resistance to chemical corrosion.

Abstract: A method of producing self-supporting ceramic a ceramic composite structures comprising (i) a polycrystalline oxidation reaction product formed upon oxidation of a body of molten parent metal with an oxidant, and (ii) interconnected porosity at least partially accessible from one or more surfaces of the ceramic body. A second polycrystalline ceramic or ceramic composite material is incorporated into the porosity of the ceramic or ceramic composite body to modify or contribute to its properties.

Abstract: A method is provided for producing a self-supporting ceramic body comprising a polycrystalline material comprised of the oxidation reaction product of a parent metal and having therein one or more channels which inversely replicate the geometry of a configured fugative metal. The method includes providing an assembly of the configured fugitive metal and the parent metal, optionally including a bed of permeable filler, and heating the assembly to form a body of molten parent metal. The molten parent metal is oxidized under selected conditions to grow the polycrystalline material to engulf the configured fugitive metal (and to infiltrate the filler, if the filler is present) and to cause the fugitive metal to disperse into the engulfing polycrystalline material thereby leaving behind as the one or more channels the space formerly occupied by the configured fugitive metal.

Abstract: This invention relates to processes for preparing a ceramic article having as its principal crystalline phase a leucite/pollucite solid solution. The process involves the use of a zeolite to form the article. Zeolites which can be used are those that have a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of about 3.5 to about 7.5 such as zeolite Y. The zeolite is exchanged with potassium, rubidium and cesium, then calcined at a temperature of about 900.degree. to about 1100.degree. C. for a time to collapse the zeolite framework and provide an amorphous powder. Next, the amorphous powder is formed into a shaped article and the article is sintered at a temperature of about 1150.degree. to about 1400.degree. C. for a time of about 0.5 to about 12 hours to give a ceramic article whose principal crystalline phase is a leucite/pollucite solid solution, is substantially crack free, has less than 5% porosity, and a coefficient of thermal expansion of about 2.times.10.sup.-6 to about 27.times.10.sup.-60 C.sup.-1.

Abstract: Pourable molding compounds containing sinterable powders contain, based on the total compound,a) from 60 to 95% by weight of sinterable powders,b) from 0.1 to 10% by weight of a surfactant, obtainable by alkoxylation of an aliphatic alcohol, fatty acid, fatty acid amide, fatty acid ester or aliphatic amine,c) from 2 to 35% by weight of an organic solvent having a melting point <10.degree. C. and a boiling point of from 40.degree. to 180.degree. C., selected from the group comprising the alkanes, ethers, esters and ketones.

Abstract: A ceramic foam filter, particularly for filtering molten iron, is formed from a composition comprising silicon carbide, alumina, silica derived from colloidal silica sol and alumino-silicate fibres, which has been fired at such a temperature that the filter has a ceramic matrix in which the alumino-silicate fibres are substantially dissolved. The filter is fired at a minimum of 1150.degree. C. and preferably within the range from 1200.degree. to 1300.degree. C. Preferably the filter is formed from an aqueous slurry having a solids content comprising by weight 20-50% silicon alumina, 20-50% alumina, 1.5-5.0% silica derived from colloidal silica sol and 1-3% alumino-silicate fibres.

Abstract: Microcrystalline alpha-alumina based ceramic articles comprising at least 60% alumina by weight, and 0.1-7.0 percent by weight iron equivalence in which substantially all the alumina is in the alpha phase having a uniform grain structure comprising alpha alumina crystallites with an average crystallite size less than 0.5 micrometer and a density greater than 90% theoretical are disclosed. Ceramic articles particularly useful as high modulus refractory fibers, among other shaped bodies such as beads, flakes, coatings, and shaped or randomly-shaped abrasive particles, are produced from a unique sol-gel process wherein hydroxy iron polymers are utilized to nucleate the alpha alumina transformation. An inherent advantage of the unique process disclosed is the resulting fine grained microstructure, and a surface roughness height of less than 100.0 nm, which is essential if a ceramic article such as an alpha alumina fiber is to have reasonable strength.

Abstract: A self-supporting ceramic body produced by oxidation of a molten precursor metal with a vapor-phase oxidant to form an oxidation reaction product and inducing a molten flux comprising said molten precursor metal through said oxidation reaction product. A second metal is incorporated into said molten flux during the oxidation reaction. The resulting ceramic body includes sufficient second metal such that one or more properties of said ceramic body are at least partially affected by the presence and properties of said second metal in the metallic constituent.

Abstract: This invention relates to a process for preparing a lithium containing ceramic article. The process provides a ceramic article that is substantially crack free and has as its principal crystalline phase a beta-eucryptite phase, a beta-spodumene phase, or a mixture thereof. The process comprises calcining a powder of a lithium-exchanged zeolite up to its collapse temperature for a time sufficient to collapse the zeolite framework and provide an amorphous powder. The amorphous powder is now formed into a shaped article and sintered at a temperature of about 700.degree. to about 1150.degree. C. for a time of about 1 to about 12 hours. The zeolites which can be used are those having a SiO.sub.2 Al.sub.2 O.sub.3 ratio of about 2 to about 8.5 and include zeolite B, zeolite ZK-19, zeolite W, phillipsite, hormotome, gismondine and mixtures thereof and have a sodium content less than about 1 weight percent. It is preferred that the lithium-exchanged zeolite have an average particle size of less than about 10 microns.

Abstract: A ceramic composition for forming a ceramic dielectric body having a dielectric constant of less than about 4.5 and a TCE of less than about 4.0 ppm/c. The composition comprises a mixture of 20-50 wt. % borosilicate glass 40-75 wt. % of a glass selected from the group consisting of glass containing 95-98 wt. % silica, titanium silicate glass and combinations thereof and sufficient amounts of gallium to inhibit the formation of crystalline forms of silica. The composition can be combined with a polymeric binder to produce an unfired green tape which is co-fireable with high conductivity metallurgies such as gold, silver and silver/palladium.

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

Abstract: A calcined microsphere of ultrafine bauxite particles having a mean particle size in the range 0.01 to 0.3 micrometers, said microsphere having a particle size less than 30 micrometers and being characterized by a substantially solid form having a pycnometric density substantially falling in the range 3.2-3.9 g/cm.sup.3, a BET surface area substantially falling in the range 0.05 to 0.5 m.sup.2 /g and a crystal grain size less than 4 micrometers, the surface chemistry of the microsphere being modified to enhance the wettability of the microsphere and to improve its ability to bond strongly with matrix materials in use.

Abstract: A process for forming a shaped article comprised of mullite whiskers comprising the following steps:a. preparing a mixture of aluminum fluoride and silicon dioxide in a weight ratio of about 7:3;b. firing the mixture in air at a temperature above about 750.degree. C. until complete conversion to topaz takes place;c. mixing the topaz product of step (b) with silicon dioxide in a weight ratio of about 18:1 together with a binder and firing at a temperature of above about 1400.degree. C. until complete conversion to mullite occurs.

Abstract: Disclosed is a process for the preparation of an anorthite sintered body, which comprises preparing a formed body of at least one powder selected from the group consisting of (i) a calcium type zeolite having an SiO.sub.2 /Al.sub.2 O.sub.3 molar ratio lower than 3, (ii) an amorphous calcination product obtained by calcining said calcium type zeolite and (iii) a mixture of said calcium type zeolite or said amorphous calcination product and an alkaline earth metal compound, and sintering the formed body at a temperature lower than 1000.degree. C.

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

Abstract: The processes of the invention involve the formation of an initial reactant mixture by combining sources of SiO.sub.2, B.sub.2 O.sub.3, aluminum, and carbon. The mixture may then optionally be shaped or compacted. The reactant mixture is then heated to start a reaction which is described by the formula:4 C+3 SiO.sub.2 +2 B.sub.2 O.sub.3 +8 Al.fwdarw.4 Al.sub.2 O.sub.3 +B.sub.4 C+3 SiC.Depending on the actual reactant mixture compositions and reaction conditions, other reactions may also occur.

Abstract: A method of producing shaped, self-supporting ceramic bodies includes preparing a mold by applying a permeable, conformable material to a shape-defining surface of an expendable pattern. The permeable, conformable material, when set or stable, provides a mold with a shaped surface which is defined by, and is therefore substantially congruent to, the shape-defining surface. Upon heating, the material of the expendable pattern combusts or volatilizes and thus establishes the shaped cavity mold. A molten parent metal is then vaporized with a vapor-phase oxidant in such a manner as to form a ceramic body which grows into the mold cavity, and is shaped by it. The ceramic body is recovered from the mold having a shaped surface replicating the shape-defining surface of the expandable pattern.

Abstract: The instant invention is directed to the production of ceramic bodies of at least one disperse inorganic component embedded in a phase of aluminum oxide by producing a mixture of aluminum powder and optionally an alloying element, and a disperse inorganic component which contains at least 40 vol. % of aluminum oxide, attriting the mixture, forming a body, and sintering the body in an oxidizing atmosphere.

Abstract: An electrolyte composite is manufactured by pressurizing a mixture of sodium ion conductive glass and an ionically conductive compound at between 12,000 and 24,000 pounds per square inch to produce a pellet. The resulting pellet is then sintered at relatively lower temperatures (800.degree. C.-1200.degree. C.), for example 1000.degree. C., than are typically required (1400.degree. C.) when fabricating single constituent ceramic electrolytes. The resultant composite is 100 percent conductive at 250.degree. C. with conductivity values of 2.5 to 4.times.10.sup.-2 (ohm-cm).sup.-1. The matrix exhibits chemical stability against sodium for 100 hours at 250.degree. to 300.degree. C.

Abstract: Sintered ceramic material which comprises doped aluminum titanate and mullite having the composition:50-61.5% by weight Al.sub.2 O.sub.3,36-47.5% by weight titanium oxide, expressed as TiO.sub.2,2.5-5% by weight SiO.sub.2,with the sum total of the three components adding up to 100%, and which further comprises 0.3 to 1% by weight MgO and up to 1% by weight impurities, useful as, inter alia, filters, catalyst supports and internal combustion engine parts, are prepared by mixing and shaping materials of suitable composition and then sintering the shaped composition at temperatures of 1250.degree. to 1600.degree. C. over a holding time of 0.5 to 100 hours.

Abstract: The invention relates to the production of a new ceramic composite material containing molybdenum disilicide in the form of 20-60 .mu.m grains.The method involves preparation of an exothermic mixture containing silicon, molybdenum (VI) oxide, aluminium and molybdenum with the following ratio of the components (wt %):______________________________________ silicon 29-38 molybdenum (VI) oxide 7-42 aluminium 3-16 molybdenum 13-52 ______________________________________its heat treatment in a combustion mode, followed by compaction of the obtained combustion products by way of at least two-stage compression with a degree of deformation from 0.75 to 0.90 at each stage, at a temperature within 1500.degree. to 1900.degree. C.

Abstract: An improved gunning composition for use in the steel industry includes between 60-75% by weight of a refractory base material, 10-20% by weight of silicon carbide, 7-15% by weight of ball clay, 4-8% by weight of a silica binder material, and, optionally, 5-10% by weight of a graphite material. The silica binder replaces binders composed of petroleum pitch or clay. The silica binder causes the composition to have (1) better adhesion, (2) less cracking, (3) improved strength, and (4) increased resistance to oxidation, corrosion and erosion.

Abstract: An improved casting composition utilizes an aqueous finely dispersed silica binder to provide reduced drying times and reduced cracking and explosion of troughs, runners and other containment equipment designed for use by the iron and steel industry. The composition is prepared by mixing 8-14% by weight of the aqueous silica binder with 55-90% by weight of a refractory base material and up to 35% by weight of silicon carbide. Preferably, the composition will also include 5-10% by weight of calcined alumina, 1-10% by weight of microsilica, and 0.02-1% by weight of a setting agent. Troughs and runners manufactured from the composition also exhibit increased strength and improved resistance to oxidation, corrosion and erosion.

Abstract: A porous filter for metal hot melt comprises ceramic aggregate particles bound by an inorganic binder. The aggregate particles contain not less than 50 wt % of particles with a shape factor in the range of 100 to 130 and the binder has needle-shaped crystals deposited on the surface thereof. By employing this filter, debris catching ability and initial impregnation of metal hot melt are highly improved.

Abstract: Substantially dense, void-free ceramic-metal composites are prepared from components characterized by chemical incompatibility and non-wetting behavior. The composites have a final chemistry similar to the starting chemistry and microstructures characterized by ceamic grains similar in size to the starting powder and the presence of metal phase. A method for producing the composites requires forming a homogeneous mixture of ceramic-metal, heating the mixture to a temperature that approximates but is below the temperature at which the metal begins to flow and pressing the mixture at such pressure that compaction and densification of the mixture occurs and an induced temperature spike occurs that exceeds the flowing temperature of the metal such that the mixture is further compacted and densified. The temperature spike and duration thereof remains below that at which significant reaction between metal and ceramic occurs. The method requires pressures of 60-250 kpsi employed at a rate of 5-250 kpsi/second.

Abstract: There is disclosed a method for making a self-supporting ceramic composite article having a porous core bearing a dense surface layer formed integrally with said core. A preform comprises a filler material and parent metal distributed therethrough, wherein the volume percent of parent metal is sufficient to form a volume of oxidation reaction product exceeding the total volume available within said preform. The parent metal is melted and reacted with an oxidant to form an oxidation reaction product filling the spatial volume and leaving voids. The reaction is continued to further transport molten parent metal through the oxidation reaction product to at least one surface of the preform to form oxidation reaction product on said surface substantially free of voids thereby forming a relatively dense surface layer.

Abstract: A hot-pressed ceramic composite of mullite/yttria stabilized zirconia/boron nitride having good resistance to thermal shock and good erosion/corrosion resistance to molten alloys, and a method for producing said composite which comprises the blending of fused mullite with boron nitride.

Abstract: A metal oxide dielectric dense body, comprising (I) grains having a predominant crystalline phase (a) a primary metal oxide selected from the group consisting of silicon and magnesium oxide and (b) optionally a secondary metal oxide selected from the group consisting of aluminum and zinc oxide and (II) between about 1 and about 20 atom % bismuth, vanadium, or boron oxide or combinations thereof, discontinuously located at the boundaries of the crystalline grains or as inclusions in the crystalline grains, the atom %'s based on the total atoms of bismuth, vanadium, boron, silicon, magnesium, aluminum, and zinc. The dense body has a density which is at least 95% of theoretical.

Abstract: A hot-pressed ceramic composite of mullite/yttria stabilized zirconia/boron nitride having good resistance to thermal shock and good erosion/corrosion resistance to molten alloys, and a method for producing said composite which comprises the blending of fused mullite with boron nitride.

Abstract: A process for producing a refractory material and to the material so-produced. The process comprises calcining red mud obtained as a by-product of the Bayer process of producing alumina, grinding the calcined product to form particles of -4 Tyler mesh, mixing the ground product with a binder (e.g. colloidal silica, colloidal alumina, sodium silicate or sodium aluminate) and sufficient water to produce a formable mixture. The mixture is then formed into a desired shape and fired, preferably after curing and drying. The resulting fired products have good resistance to high temperatures and to corrosive chemicals such as cryolite. Consequently, the products can be used as refractory linings for aluminium production cells, and in similar applications.

Abstract: The invention relates to a method for producing ceramic composites obtained by oxidation of a parent metal to form a polycrystalline ceramic material by providing a filler having a coating of a silicon source on at least a portion of the filler different in composition from the primary composition of the filler, said silicon source possessing intrinsic doping properties. A body of molten parent metal, adjacent a mass of the filler material, reacts with an oxidant to form an oxidation reaction product which infiltrates the adjacent mass of filler, thereby forming the ceramic composite.

Abstract: The present invention relates to a method of forming ceramic matrix composite bodies comprising a parent metal reacting with an oxidant to produce an oxidation reaction product which infiltrates a loose unbonded mass or a preform comprising a filler material mixture. Specifically, the filler material mixture used in the method of the present invention comprises a material having varying compositions, sizes and/or shapes of filler material within the mass or preform. By utilizing a filler possessing varying compositions, sizes and/or shapes, enhanced packing of the filler material is achieved which may result in improved properties, such as erosion resistance, corrosion resistance, etc. Further, the use of filler material containing varying sizes and/or shapes may also enhance the growth rate of oxidation reaction product, thereby reducing processing times for formation of the resultant ceramic composite body.

Abstract: A low cement castable refractory comprising 85 to 96% by weight of a calcined ultrafine bauxite aggregate characterized by a particle size of less than 10 um, 2 to 10% by weight of a suitable cement material, 0 to 8% of weight of a thixotropic agent and 0 to 2% by weight of suitable deflocculants and plasticizers, the cement material comprising calcium aluminate cement having an alumina content of 40 to 85% and the thixotropic agents being selected from those containing microfine silica, and/or reactive alumina, the inorganic deflocculants and plasticizers being selected from alkali phosphates, lignosulphonates or naphthalene sulphonates. A method of making a low cement castable refractory and installing a low cement castable refractory are also described.

Abstract: This invention relates generally to a novel method of preparing self-supporting bodies and to the novel products made thereby. In its more specific aspects, this invention relates to a method of producing self-supporting bodies having controlled porosity and graded properties and comprising one or more boron-containing compounds, e.g., a boride or a boride and a carbide. The method comprises, in one embodiment, reacting a powdered parent metal, in molten form, with a bed or mass comprising a boron carbide material and, optionally, one or more inert fillers, to form the body. In another embodiment, both of a powdered parent metal and a body or pool of molten parent metal are induced to react with a bed or mass comprising a boron carbide material and, optionally, one or more inert fillers. in addition, combustible additives (e.g., gelatin, corn starch, wax, etc.) can be mixed with the bed or mass comprising a boron carbide material to aid in the porisity producing process.

Abstract: Disclosed is a method of forming an improved ceramic matrix composite wherein there is provided a slurry comprised of aluminum oxide, boron oxide and an organic binder suspended in a liquid, and combining the slurry with fibers. The aluminum oxide and boron oxide are capable of reacting to form aluminum borate. The improvement comprises providing the fibers with a coating which forms a stable interface between the fibers and the aluminum borate.

Abstract: A method of producing ceramic composites of Al.sub.2 O.sub.3 reinforced by shaped SiC particles preferably shaped as fine particles (random), platelets, whiskers or fibres by in situ production of SiC particles by heating a mixture of carbon particles of the desired shape with silicates of Al.sub.2 O.sub.3 to a temperature above 1500.degree. C., convert the silicates and carbon to Al.sub.2 O.sub.3 and SiC to produce in situ SiC particles of the desired shape and provide a ceramic powder that may be densified by techniques such as hot pressing, isostatic pressing or sintering.

Abstract: A process for preparing a cordierite, which includes dissolving a silicon compound, an aluminum compound and a magnesium compound in a molar ratio of 1:0.7 to 1:0.3 to 0.5 in a complexing agent represented by the formula R(OCH.sub.2 CH.sub.2).sub.n OH, wherein R is an alkyl group and n is an integer of 1 to 4; heating the resulting solution to bring about a ligand exchange reaction of the silicon compound, aluminum compound and magnesium compound with the complexing agent; conducting hydrolysis to form a gel; drying the gel and sintering the dried gel at 800.degree. to 1450.degree. C.

Abstract: This invention relates to a self-supporting ceramic strucutre comprising an oxidation reaction product of a parent metal and a vapor-phase oxidant characterized by an altered microstructure attributable to the addition of one or more process modifiers relative to substantially the same oxidation reaction product produced without a process modifier.

Abstract: A fiber-reinforced ceramic composite material reinforced by particle dispersion with improved fracture toughness comprised of a mullite matrix, and fibers and same or different kind of ceramic fine particles both dispersed within the mullite matrix is produced by a method comprising: dispersing mullite particles forming a matrix in a solution dissolving an organometallic macromolecular substance to prepare an impregnating solution, continuously passing fibers through said impregnating solution to uniformly impregnate the fibers with said impregnating solution, laminating said fibers to provide a laminated body, converting the organometallic macromolecular substance within said laminated body into a nonmeltable state, and performing sintering (or press sintering) of said laminated body in an inert gas and/or nitrogen gas. By press sintering K.sub.Ic of 10 MN/m.sub.3/2 or more is achieved.

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

Abstract: The present invention comprises rice hull ash which is pelletized subsequent to its admixture with a bentonite clay binder. A preferred product according to the present invention is pelletized rice hull ash which contains both bentonite clay and organic cornstarch binders. The bentonite clay contains approximately 58-68% SiO.sub.2, 18-21% Al.sub.2 O.sub.3, 2.5-2.8% Fe.sub.2 O.sub.3 /FeO, 2.5-3.2% MgO, 0.1-1.0% Cao, 1.5-2.7% Na.sub.2 O, 0.2-0.45% K.sub.2 O, and 4.5-9.0% free H.sub.2 O. Insulator pellets according to the present invention, when placed atop molten steel in ladles or tundishes, insulate well and do not smoke or generate unwanted dust.

Abstract: This invention relates to processes for preparing ceramic articles. One process involves taking a potassium exchanged zeolite, the zeolite characterized in that it has a SiO.sub.2 /Al.sub.2 O.sub.3 ratio of 3.5 to about 7.5, and calcining it at a temperature of about 900.degree. to about 1100.degree. C. for a time sufficient to collapse the zeolite framework and provide an amorphous powder. Next, the amorphous powder is formed into a shaped article and the article is sintered at a temperature of about 1150.degree. to about 1400.degree. C. for a time of about 0.5 to about 12 hours to give a ceramic article whose principal crystalline phase is tetragonal leucite, is substantially crack free, and has less than 5% porosity.

Abstract: A metal oxide dielectric dense body, comprising (I) grains having a predominant crystalline phase (a) a primary metal oxide selected from the group consisting of silicon and magnesium oxide and (b) optionally a secondary metal oxide selected from the group consisting of aluminum and zinc oxide and (II) between about 1 and about 20 atom % bismuth, vanadium, or boron oxide or combinations thereof, discontinuously located at the boundaries of the crystalline grains or as inclusions in the crystalline grains, the atom %'s based on the total atoms of bismuth, vanadium, boron, silicon, magnesium, aluminum, and zinc. The dense body has a density which is at least 95% of theoretical.

Abstract: A ceramic material for use in insert-casting, which contains not less than 65% by volume of aluminum titanate as a crystalline phase. The average particle diameter of crystals of the aluminum titanate is not less than 10 .mu.m, and not more than 20% by volume of a glass phase containing a rare earth element in an amount of 0.5 to 16% by weight when calculated in the form of an oxide is contained. Young's modulus is 50 to 2,000 kgf/mm.sup.2. A process for producing the same is also disclosed, which includes the steps of preparing a powder by mixing a material, as an Al.sub.2 O.sub.3 source material, containing not more than 96% by weight of Al.sub.2 O.sub.3 and having an average particle size of not less than 3 .mu.m, a material having an average particle diameter of not more than 3 .mu.m as a TiO.sub.2 source material, and a given rare earth element in an amount of 1.8% by weight when calculated in the form of an oxide, shaping the powder, and drying and firing the shaped body.

Abstract: An improved ramming composition for use in the iron and steel industry includes between 65-80% by weight mullite, 5-15% by weight silicon carbide, 2-5% by weight graphite, 2-6% by weight ball clay, and 5-10% by weight of a binder formed from a dispersion of 15-70% by weight silica in water. The silica binder replaces binders composed of petroleum pitch, clay, or other organic materials. The silica binder causes the ramming composition to have a longer use life, increased strength, and reduced tendency to crack, oxidize or smoke.

Abstract: A ceramic consisting essentially of from 1 to 15 percent of glass and 99 to 85 percent of a mixture of particulate Al.sub.2 O.sub.3 and particulate ZrO.sub.2 is disclosed. ZrO.sub.2 is present in a sufficient amount, usually from 1/4 to 6 percent based on the weight of the ZrO.sub.2 and Al.sub.2 O.sub.3, to strengthen the ceramic significantly, by comparison with an otherwise identical ceramic where the particulate ZrO.sub.2 is replaced either by the glass or by particulate Al.sub.2 O.sub.3. The glass constitutes a vitreous phase bonding the particulates into a dense, gas impervious structure, and can be a calcium magnesium silicate glass containing from 45 to 80 percent of SiO.sub.2, from 8 to 55 percent of CaO and MgO, and not more than 15 percent of Al.sub.2 O.sub.3.