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

Abstract: Oxide-based ceramic cutting inserts for chipforming machining of steel, comprising a ceramic oxide-based matrix of alumina and less than 10% by volume zirconia and 5-40% by volume of homogeneously dispersed whiskers based upon (Ta.sub.x Hf.sub.y Ti.sub.1-x-y)C.sub.1-z N.sub.z where 0<x<0.75 and 0<y<0.75, x+y>0.25 and 0.ltoreq.z<1.

Abstract: The purpose of the present invention is to provide a cubic boron nitride based sintered material having excellent durability and capable of cutting at least spheroidal graphite cast iron at high speed and usable in a cutting tool having a long life, and a production method of this cubic boron nitride based sintered material. The present invention resides in a production method of a cubic boron nitride based sintered material characterized in that a mixing raw material is produced by mixing powder of Ti.sub.(1-x) Al.sub.x N(x=0.05.about.0.70) and the powder of a cubic boron nitride, and is next sintered. A compounding ratio of the above mixing raw material is preferably set such that this mixing raw material includes 10 to 90% of the above Ti.sub.(1-x) Al.sub.x N(x=0.05.about.0.70) by volume and 10 to 90% of the above cubic boron nitride by volume.

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

Abstract: A large-format fireclay refractory brick (1), in particular bottom block in a tin bath, made of a material from the system Al.sub.2 O.sub.3--SiO.sub.2, consists of a block (2) having a top surface (3) contacting the tin bath when in use. The top surface (3) of the block (2) is covered with a coating (13) containing alkali silicate in order to form a separating layer on the top surface (3) of the block (2). The separating layer is adapted for glazing and acts as a capturing material for the sodium from the tin bath due to the decreased offer of Al.sub.2 O.sub.3 and the increased offer of alkali and silica in the coating (13) compared with the material of the block (2).

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

Abstract: Hydrofluoric acid-resistant ceramic mortar compositions containing a hydrofluoric acid-resistant grog having a particle size distribution imparting a high particle packing fraction to the mortar composition and a binding phase containing a metal salt having a particle size distribution imparting plasticity to the mortar composition selected from hydrofluoric acid-insoluble fluoride salts, metal salts capable of forming hydrofluoric acid-insoluble fluoride salts upon reaction with a fluorinating reagent and mixtures thereof. Methods for forming hydrofluoric acid-resistant ceramic mortar compositions from non-fluoride metal salts are also disclosed as well as methods for bonding refractory bricks into a brickwork unit with the ceramic mortars of the invention. Brickwork units prepared using the ceramic mortar compositions of the invention by the methods of the invention are also described.

Abstract: A ceramic body having a surface region containing tetragonal zirconia is sintered to at least 95% theoretical density at a temperature below about 1550 .degree. C. The surface region is then heat treated to reverse local stresses therein. Low temperature degradation in tetragonal zirconia, and materials containing tetragonal zirconia, is significantly inhibited. The heat treated ceramic is especially suited for use in structural components such as valves, engine housings, pistons (chambers) and the like which, during operation, are frequently exposed to temperatures ranging from room temperature to 500.degree. C. for prolonged periods of time.

Abstract: Low or negative thermal expansion compounds are described having a formula of A.sub.2-x.sup.3+ A.sub.y.sup.4+ M.sub.z.sup.3+ M.sub.3-y.sup.6+ P.sub.y O.sub.12. It currently is believed that y can vary from about 0 to about 2, x equals the sum of y and z and varies from about 0.1 to about 1.9. Without limitation, novel compounds satisfying the formula A.sub.2-x.sup.3+ A.sub.y.sup.4+ M.sub.z.sup.3+ M.sub.3-y.sup.6+ P.sub.y O.sub.12 where y=0 may be selected from the group consisting of Al.sub.1.5 In.sub.0.5 W.sub.3 O.sub.12, Al.sub.1.6 In.sub.0.4 W.sub.3 O.sub.12, Al.sub.1.7 In.sub.0.3 W.sub.3 O.sub.12, Al.sub.1.8 In.sub.0.2 W.sub.3 O.sub.12, YAlW.sub.3 O.sub.12, ScAlW.sub.3 O.sub.12, ScGaW.sub.3 O.sub.12, ScInW.sub.3 O.sub.12, ScHoW.sub.3 O.sub.12, ScYbMo.sub.3 O.sub.12 and ErInW.sub.3 O.sub.12. Without limitation, novel compounds satisfying the formula A.sub.2-x.sup.3+ A.sub.y.sup.4+ M.sub.z.sup.3+ M.sub.3-y.sup.6+ P.sub.y O.sub.12 where y=2 may be selected from the group consisting of Hf.sub.2 WP.sub.2 O.

Abstract: The invention concerns a process for the production of alumina for ceramics by calcining alumina trihydrate in the presence of a mineralizer such as a halogenated compound and/or a boron compound, the calcined alumina being constituted by friable agglomerates of elementary particles, or crystallites, of alpha alumina, the average size of which can be fixed as required, with a unimodal narrow distribution of crystallite sizes, characterized in that calcining of the alumina trihydrate is carried out in an industrial kiln in a renewed oxidising atmosphere at a temperature in the range 800.degree. C. to 1300.degree. C. for a period of 0.5 hour to 4 hours in the simultaneous presence of a halogenated compound acting as a mineralizer and a silica based alumina recrystallisation modifier which is uniformly and intimately distributed in the alumina trihydrate charge.

Abstract: A sintered ceramic body which can be worked by electrical discharge machining, has high mechanical strength, and can be worked into sintered ceramic tools which have long life is disclosed. Further, sintered ceramic tools which have long life and scarcely cause flaws in work pieces are provided. The sintered ceramic body comprises ceramic particles having specific particle diameter and particle distribution.

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

Abstract: A continuous hydrothermal synthesis method which comprises pressurizing and heating a material slurry below a saturated vapor temperature or pressurizing a material slurry at normal temperature, pressurizing and heating an aqueous liquid above the saturated vapor temperature, atomizing and mixing the slurry and the aqueous liquid, effecting hydrothermal synthesis in a reaction section above the saturated vapor temperature, cooling the reaction product and taking out the product while retaining the pressurized state in the system by alternately opening and closing shut-off valves provided above and below a product discharging section or through a thin pipe provided in the product discharging section. The method is performed using an apparatus comprising heating-pressurizing sections respectively connected to a material slurry feeding section and an aqueous liquid feeding section, an atomizing-mixing section and a reaction section provided after these feeding sections, and a product discharging section.

Abstract: To provide a high-temperature stable transition-type alumina that does not undergo transformation into .alpha.-alumina even at high-temperature exceeding 1300.degree. C., and a method for producing the transition-type alumina.A metal aluminum block is placed on a block of .alpha.-alumina composed of Al.sub.2 O.sub.3. Portions of the .alpha.-alumina block and the metal aluminum block close to their boundary was strongly heated by contacting the flame of burning gas with the portions. Alumina and a relatively small amount of magnesium are thereby vaporized, and allowed to react with oxygen in the atmosphere, thereby obtaining a transition-type alumina that contains a small amount of magnesium in the crystal structure. The transition-type alumina obtained by this method is substantially of single crystal type, and does not undergo transformation into .alpha.-alumina even at high temperatures exceeding 1300.degree. C.

Abstract: A novel ceramic composite of a solidified body consisting of at least two crystal phases of oxides selected from metal oxides and complex metal oxides, except for the Al.sub.2 O.sub.3 /Y.sub.3 Al.sub.5 O.sub.12 combination.

Abstract: A red brick comprising waste foundry sand of 30.about.50 wt %, dusts of 5.about.10 wt %, and a remainder of clay. The waste foundry sand and dusts can be efficiently recycled, and the quantity of the sand used, the supply of which sand which is nearly exhausted, can be reduced. The heating temperature in the red brick manufacturing process is remarkably lowered, and the economical efficiency of the manufacturing process is improved greatly by using iron oxide included in dusts, instead of a chemical compound to obtain desired color.

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

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

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

Abstract: An alumina-zirconia sintered body comprising 92 to 35% by weight of aluminum oxide and 8 to 65% by weight of zirconium oxide having mainly tetragonal system, and 0.2 to 5 parts by weight of silicon oxide per 100 parts by weight of the total of aluminum oxide and zirconium oxide, and having a relative density of 95% or more, has improved wear resistance and suitable for use in an impact grinder.

Abstract: A low frictional ceramic material for sliding member, consists essentially of oxide of aluminum (Al) and oxide of zirconium (Zr) and contains oxide of cerium (Ce). Aluminum (Al) content is 50 to 75 wt. % in terms of alumina (Al.sub.2 O.sub.3), zirconium (Zr) content is 20 to 45 wt. % in terms of zirconia (ZrO.sub.2), and cerium (Ce) content is 3 to 20 wt. % in terms of ceria (CeO.sub.2)in said low frictional ceramic material for sliding member.Instead of oxide of aluminum (Al) and oxide of zirconium (Zr), it is capable to use a .alpha.-sialon.

Abstract: A low dielectric insulation layer for an integrated circuit structure material, and a method of making same, are disclosed. The low dielectric constant insulation layer comprises a porous insulation layer, preferably sandwiched between non-porous upper and lower insulation layers. The presence of some gases such as air or an inert gas, or a vacuum, in the porous insulation material reduces the overall dielectric constant of the insulation material, thereby effectively reducing the capacitance of the structure. The porous insulation layer is formed by a chemical vapor deposition of a mixture of the insulation material and a second extractable material; and then subsequently selectively removing the second extractable material, thereby leaving behind a porous matrix of the insulation material, comprising the low dielectric constant insulation layer.

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

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

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

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

Abstract: A shaped, high-strength dental ceramic prosthesis is made by pressing a molding composition including from about 1 to 50 percent by weight glass particles and from about 99 to about 50 percent by weight inorganic oxide particles at a pressure of from about 10 to about 40 MPa and a temperature of from about 1000.degree. to about 1200.degree. C. Dental prostheses prepared in accordance with the invention include crowns, bridges, inlays and onlays.

Abstract: A thermal shock-resistant alumina-mullite composite material and a preparation method thereof which are capable of concurrently obtaining the compactness of the material and a mullite formation. The material is comprised of 4.about.30 weight % of one aluminum silicate selected from the group consisting of kaolinite, silimanite, and kyanite, 75.about.94 weight % of Al.sub.2 O.sub.3 based on the total amount of Al.sub.2 O.sub.3, and 0.5.about.6 weight % of an alkaline earth metal oxide, wherein the weight ratio of the alkaline earth metal oxide to SiO.sub.2 is 1:2.about.1:3. The composition is first sintered at a temperature of 1450.degree..about.1650.degree. C. for 1.about.5 hours, then cooled down to 1000.degree. C., and then crystallized at a temperature of 1200.degree..about.1500.degree. C. for 1.about.20 hours. This composition is usable to a maximum temperature 300.degree. C.

Abstract: A process for preparing a stabilized alumina wherein an aqueous slurry of a precursor boehmite alumina is admixed with an effective amount of a stabilizer such as a water-soluble salt of a polyvalent metal cation of Groups IIA and IIIB of the periodic table, the slurry containing the alumina and the stabilizer being aged at a pH of from about 3 to about 9 and a temperature greater than about 70.degree. C. for a period of time sufficient to convert the greater portion of said alumina to a colloidal sol, the colloidal sol being recovered and calcined to produce a stabilized alumina.

Abstract: A method for optimizing the performance characteristics of a combustion synthesized ceramic or metal ceramic product, including the steps of initially applying sufficient current to the product so as to raise the temperature of the product to a minimum of 50% of the melting point in degrees Kelvin, of the lowest melting phase in the product and thereby densifying the product. A method for enhancing the adherence of a ceramic or metal ceramic electrical heating element to an electrical terminal, and for improving the electrical properties of the resulting product is included.

Abstract: An aluminous sintered product comprising 70 to 96% by weight of an alumina component and 4 to 30% by weight of additives, said additives including at least the one selected from oxides of elements of the Group 5a of periodic table and at least the one selected from oxides of metals of the iron family and oxides of manganese, titanium, calcium, magnesium, chromium and silica, and said aluminous sintered product exhibiting a volume resistivity of from 1.times.10.sup.7 to 1.times.10.sup.13 .OMEGA.-cm over a temperature range of from 25.degree. to 75.degree. C. and an absolute value of the temperature coefficient of volume resistivity of not larger than 1.8%/.degree.C. under the application of high voltages.

Abstract: Plasticized inorganic powder batches comprising a cellulosic binder, water, and at least one inorganic powder exhibiting relatively high water affinity are compounded by combining the inorganic powder, prior to any contact with the water or cellulosic binder, with an organic surface treatment agent to decrease the water affinity thereof; subsequent mixing of the treated powder with the water and the cellulosic binder forms a plasticized inorganic powder batch with improved extrusion, molding, or other shaping characteristics.

Abstract: Ceramic preforms comprising monocrystalline hexagonal platelets of .alpha.-alumina, well adopted for conversion into refractory bricks or ceramic composites, are prepared by crystallizing a settled fine powder of amorphous alumina, transition alumina or alumina hydrate, advantageously in the presence of a fluoro-compound flux, into a coherent mass of such hexagonal platelets of .alpha.-alumina.

Abstract: The present invention provides an anti-bacterial and anti-fungal glaze composition for ceramic products formed by incorporating a silver-containing substance; and a refractory and/or glass composition. The present invention can be used in the manufacture of ceramic products requiring sanitary properties such as tile, sanitary earthenware, commodes, bath tubs and the like, and according to the present invention, anti-bacterial and anti-fungal properties can be effectively exhibited therein. In particular, the present invention can be used in sink basins, tile, commodes, bath tubs, and the like of hospitals, hotels and public facilities.

Abstract: The disclosure refers to the art of remarkably increasing the hardness of alumina materials, such as alumina abrasives, alumina ceramics or aluminum oxide single crystal (sapphire), containing aluminum oxide (Al.sub.2 O.sub.3) as the main component, or the hardness of products using the same.The alumina material is partially or wholly hardened to have a micro-Vickers hardness of no less than 2600 kgf/mm2 (under a test load of 300.times.9.807 mN) by inclusion of an oxide or fluoride additive which is solid-soluble in aluminum oxide. Preferable examples of the additive include TiO.sub.2 and/or Y.sub.2 O.sub.3.

Abstract: The present invention provides a process for preparing a molybdenum, molybdenum silicide or molybdenum carbide/ceramic admixture, comprising dissolving molybdenum trioxide powder with an alkaline solvent to obtain an aqueous solution of molybdate; incorporating ceramic powder with or without silicon and/or carbon powder into the aqueous solution of molybdate to obtain a slurry; and subjecting the slurry to spray drying and reduction to obtain the admixture. The obtained admixture can be formed and sintered into a nanometer-sized and uniformly dispersed molybdenum, molybdenum silicide or molybdenum carbide/ceramic sintered composites.

Abstract: A monolithic refractory composition, which can be rapidly dried after being mixed with water and applied to a desired portion by casting or spraying to form a furnace wall, and which comprises refractory aggregates, a refractory powder, an aluminum alloy powder and a dispersant, wherein the aluminum alloy powder is contained in an amount of from 0.04 to 5 parts by weight per 100 parts by weight of the total amount of the refractory aggregates and the refractory powder.

Abstract: An alumina-based sintered material for ceramic heater having a resistance heater embedded in its ceramic material. With the total amount of Al.sub.2 O.sub.3, SiO.sub.2, MgO and CaO being 100 wt %, the sintered material contains 91 to 97 wt % of Al.sub.2 O.sub.3, 1 to 8 wt % of SiO.sub.2, 0.2 to 1.2 wt % of MgO and 0.2 to 1.2 wt % of CaO, the total amount of MgO and CaO being 0.4 to 1.8 wt %, whereas, for the total amount of Al.sub.2 O.sub.3, MgO and CaO of 100 wt %, 0.1 to 15 wt % of (a) at least one of rare earth elements and groups IVa excluding Ti, Va and VIa of the Periodic Table are contained in the sintered material. In place of (a), 0.2 wt % or less of other elements (Na, K, Fe, Ti etc.) may also be contained in an amount not more than 0.2 wt %, calculated in terms of oxides.

Abstract: Ceramic abrasive grits are formed by an impregnation process that involves preparing an alumina hydrate sol, drying the sol to form a porous solid, crushing the solid to produce particles, calcining the dried particles, preparing a mixture of an additive metal oxide or its precursor in a liquid vehicle, impregnating the mixture into the calcined particles, drying the impregnated particles, calcining the dried impregnated particles, and firing the particles to produce ceramic abrasive grits. The concentration of the modifying additive metal is greater at or near the surface of the grit than at the interior of the grit.

Abstract: A colored refractory material for lining an instrument/apparatus used at a high temperature is formed by mixing a powder of a raw material containing ceramics with a coloring agent and kneading with a liquid using a binder. The refractory material is put in lining for a portion being in contact with a high temperature molten substance or being exposed to a high temperature atmosphere, and is dried by heating while adjusting a temperature and a heating time on the basis of color change on the surface of the refractory material.

Abstract: A composition and process for making an insulating refractory material. The composition includes calcined alumina powder, flash activated alumina powder, an organic polymeric binder and a liquid vehicle which is preferably water. Starch or modified starch may also be added. A preferred insulating refractory material made with the composition has a density of about 2.4-2.6 g/cm.sup.3 with reduced thermal conductivity, compared with tabular alumina. Of importance, the formulation has good abrasion resistance and crush strength during intermediate processing (commercial sintering) to attain full strength and refractoriness, good abrasion resistance and crush strength.

Abstract: A .beta.-alumina electrocast refractory formed of a composition of 91-95 wt. % of Al.sub.2 O.sub.3, 2.0 wt. % or less of K.sub.2 O, 4.0-7.0 wt. % of Na.sub.2 O and K.sub.2 O in total, 0.15-2.0 wt. % of BaO, SrO and CaO in total, and 0.1 wt. % or less of Fe.sub.2 O.sub.3 and TiO.sub.2 in total.

Abstract: Alumina composites of unusually high hardness and toughness are formed by combining alumina and diamond in nanocrystalline form, followed by sintering at high pressure.

Abstract: The invention is directed to a non-vapor phase process for forming a metal/ceramic composite containing a relatively inert metal such as silver, copper, or nickel by the reaction of a reactive metal or metal alloy containing the inert metal, and a sacrificial ceramic preform. The resulting metal/ceramic composite is essentially the same shape and dimensions as the sacrificial ceramic preform, and exhibits improved physical and mechanical properties, including improved corrosion and wear resistance.

Abstract: Method for making alpha alumina-based ceramic material (e.g., abrasive grain and fibers) from a hydrothermally treated boehmite dispersion comprising colloidal silica.

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: Novel aluminum phosphates, in particular amorphous aluminum phosphate powders having a BET specific surface no greater than 25 m.sup.2 /g, well suited as binders/hardeners or for the production of ceramic shaped articles, are prepared by reacting at least one aluminum compound, e.g., an aluminum oxide, hydroxide or oxyhydroxide, with phosphoric acid or an aluminum phosphate, e.g., an acid aluminum orthophosphate, in a liquid reaction medium devoid of inorganic acid anions other than of phosphoric acid, and then spray- or freeze-drying the suspension thus obtained.

Abstract: A process for densifying a porous structure with boron nitride includes placing the porous structure in a borazene precursor of the formula RBNH wherein R is a halogen or hydrogen, heating by induction at a pressure of at least 1.2.times.10.sup.5 Pa and thereby decomposing the precursor to form boron nitride that is deposited within the pores of the porous structure.