Abstract: This invention relates to the preparation of polycrystalline silicon carbide fibers from ceramic fiber. The process involves heating the ceramic fiber in an environment containing a volatile sintering aid to a temperature sufficient to convert the ceramic fiber to the polycrystalline silicon carbide fiber.

Abstract: A new silicon carbide material is made following a procedure including hot pressing to provide a finished product having a microstructure with an optimal grain size of less than 7 micrometers. The material exhibits a dominant failure mode of intergranular fracture requiring significant energy for crack propagation. The method of manufacturing is cost-effective by allowing the use of "dirty" raw materials since the process causes impurities to segregate at multi-grain boundary junctions to form isolated pockets of impurities which do not affect the structural integrity of the material. End uses include use as optical and electronic substrate materials.

Abstract: This invention provides composite ceramic powder comprising matrix ceramic powder and fine particles of ceramic, metal or metal compound which are different from the matrix ceramic powder and dispersed in the matrix ceramic powder. The composite ceramic powder is produced by mixing matrix ceramic powder or its precursor with fine particles to be dispersed therein and then heating the resulting mixture. The composite ceramic powder is also produced by dispersing matrix ceramic particles or precursor thereof in an organic solvent with an organic compound as a dispersoid particle precursor and separating and recovering the organic solvent. The composite ceramic powder is suitable for producing sintered bodies having excellent properties, especially with respect to thermal conductivity, flexural strength and light transmittance, by a conventional ceramic fabrication process.

Abstract: A coating composition for use with ceramic composites to reduce gas permeability of the composites as well as provide an adhesive force to the composites. The coating composition comprises an aqueous dispersion of an aluminum phosphate precursor, silicon carbide, and aluminoborosilicate.

Abstract: The present invention relates to whisker reinforced ceramic bodies with new and improved properties. By replacing the tool pressing with injection molding, surprisingly a more homogeneous structure and more advantageous whisker orientation has been obtained. By choosing the conditions of the molding, it is possible to control the whisker orientation to get optimal material properties. Bodies according to the invention are particularly suitable for chip forming machining of heat resistant materials.

Abstract: In the present invention, there is provided a method for producing a self-supporting ceramic or ceramic composite body by the oxidation of a parent metal to form a polycrystalline ceramic material comprising the oxidation reaction product of said parent metal with an oxidant, including a vapor-phase oxidant, and optionally one or more metallic constituents dispersed throughout the polycrystalline ceramic material. The method comprises the steps of providing at least a portion of said parent metal with a barrier means at least partially spaced from said parent metal for establishing at least one surface of the ceramic body, and heating said parent metal to a temperature above its melting point but below the melting point of the oxidation reaction product to form a body of molten metal. At that temperature, the molten metal is reacted with the oxidant, thus forming the oxidation reaction product.

Abstract: A silicon-carbide sintered article prepared by permeating molten silicon into a carbon compact of elemental carbon, wherein Lc(002), which indicates a length of a domain in the direction perpendicular to the C(002) surface of elemental carbon in the carbon compact, is up to 1000 angstrom. The resulting article includes silicon carbide, silicon, and up to about 1 percent by weight of residual elemental carbon based on the sum of the silicon carbide and the silicon.

Abstract: Mixes for forming high alumina refractory shapes with high resistance to aluminum penetration comprising at least about 60% by weight aluminum oxide, about 1 to 5% by weight boron phosphate, and about 5 to 15% by weight silicon carbide. A phosphorous-containing binder is added and the mix can be formed into brick which when cured or burned to a temperature below the oxidation temperature of silicon carbide can be used to minimize aluminum penetration and dross when the brick are employed in a metallurgical vessel in contact with molten aluminum.

Abstract: A ceramic cutting insert for high speed machining of materials is provided having an integral chip control surface thereon.

Abstract: The ceramic composites consisting of sintered alumina comprising a polycrystalline alumina matrix having a grain size of from 0.5 to 10 .mu.m, and fine particles of TiB.sub.2 2 .mu.m or less in diameter being dispersed in the alumina grains, the composite alumina ceramic containing from 15 to 40% by volume of TiB.sub.2 ; or a ceramic composites comprising a polycrystalline alumina matrix as above, fine particles of TiB.sub.2, and fine particles of SiC, the fine particles of TiB.sub.2 and SiC being each 2 .mu.m or less in diameter and being dispersed in the alumina grains, the ceramic composites containing from 5 to 30% by volume of TiB.sub.2 and from 5 to 30% by volume of SiC.

Abstract: A ceramics composites prepared by dispersing any one of the following materials (i) to (viii) in Al.sub.2 O.sub.3 which as a matrix-containing crystalline grains having a grain size of 0.5 to 100 .mu.m. (i) 3 to 40% by volume of fine TiN particles having a particle size of not more than 2 .mu.m and 3 to 40% by volume of fine SiC particles having a particle size of not more than 2 .mu.m. (ii) 3 to 40% by volume of fine TiN particles having a particle size of not more than 2 .mu.m and 3 to 40% by volume of fine Si.sub.3 N.sub.4 particles having a particle size of not more than 2 .mu.m. (iii) 2 to 35% by volume of fine TiC particles having a particle size of not more than 2 .mu.m and 5 to 40% by volume of SiC whiskers having a diameter of 0.05 to 2 .mu.m. (iv) 2 to 35% by volume of fine TiC particles having a particle size of not more than 2 .mu.m and 5 to 40% by volume of Si.sub.3 N.sub.4 whiskers having a diameter of 0.1 to 2 .mu.m.

Abstract: A low cost pressureless sintered silicon carbide ceramic composite having relatively high electrical conductivity, relatively high density and relatively great mechanical strength, in comparison to those known to persons skilled in the art, and a process for making such composites.

Abstract: A plastic refractory composition in which the constituents are silicon carbide grain having a SiC content of at least 92% SiC, a calcined or reactive alumina, up to 10% bentonite, and 0.5 to 5% boron phosphate. A phosphorous-containing liquid is used to bind the composition when used.Also disclosed are pressed shapes, particularly tiles, made from such compositions in which ball clay is substituted for the bentonite.

Abstract: A sintered material for recording/reading (particularly magnetic) head slider is produced by:preparing a powdery mixture which comprises 0.5 to 6.0% by weight of at least one component selected from the component group A consisting of the following elements and compounds thereof, a garnet type compound consisting essentially of erbium oxide and aluminum oxide in amounts of 2 to 12% by weight and 0 (exclusive) to 2 (inclusive) % by weight based on the total composition, respectively, and expressed by the formula Er.sub.3 (Al,Er).sub.2 (AlO.sub.4).sub.3 through (Er, Al).sub.3 Al.sub.2 (AlO.sub.4).sub.3, and the balance being silicon carbide powder:the elements for the component group A being Ti, V, Cr, Mn, Mg, Y, Zr, Nb, Mo, Ba, La, Ce, Gd, Hf, Ta, W, Th, and Cs; andsintering the resultant mass under the application of a high pressure.Further sintering aids of Be, BeO, B and B.sub.4 C may be present. For the garnet type compound, erbium oxide may be used, preferably in combination with alumina.

Abstract: The present invention is a process for producing .beta.-sialon based sintered bodies having a fracture toughness (K.sub.IC) of at least 6.5 MPam.sup.1/2.The process comprises preparing a feed that consists of 0.5-20 wt % of a sintering aid (e.g. MgO) with an average particle size of no more than 5.0 .mu.m, 3-40 wt % of an additive (e.g. SiC) with an average particle size of no more than 5.0 .mu.m, with the remainder being a .beta.-sialon powder having an average particle size of no more than 2.0 .mu.m, wet mixing the individual feeds to form a slurry, drying the slurry and sintering the dried slurry.

Abstract: A new silicon carbide material is made following a procedure including hot pressing to provide a finished product having a microstructure with an optimal grain size of less than 7 micrometers. The material exhibits a dominant failure mode of intergranular fracture requiring significant energy for crack propagation. The method of manufacturing is cost-effective by allowing the use of "dirty" raw materials since the process causes impurities to segregate at multi-grain boundary junctions to form isolated pockets of impurities which do not affect the structural integrity of the material. End uses include use as optical and electronic substrate materials.

Abstract: A sintered silicon carbide ceramic body preferably produced from a uniform mixture comprising from about 82 percent to about 99.4 percent by weight silicon carbide, from about 0.5 percent to about 10 percent by weight of a nitrogen containing aluminum compound and from about 0.1 to about 8 percent of a rare earth oxide, both reacted with oxygen, wherein said sintered ceramic body has a density greater than 90% percent of theoretical and a fracture toughness, as measured by a single edge notched beam test, of more than 7 MPam.sup.1/2 and method of making the same.

Abstract: A method is taught for modifying the coefficient of thermal expansion of a molybdenum disilicide matrix material, so as to permit preparation of ceramic fiber reinforced matrices having improved high temperature strength, creep resistance, toughness, and resistance to matrix cracking during thermal cycling.

Abstract: A molybdenum disilicide composite comprising ceramic reinforcing fibers and sufficient particulate silicon carbide, silicon nitride, boron nitride or silica to modify the coefficient of thermal expansion of the matrix to match that of the fiber is found to have improved high temperature strength, creep resistance, toughness, and resistance to matrix cracking during thermal cycling.

Abstract: An aluminum oxide-based sintered object having excellent abrasion resistance includes .alpha.-aluminum oxide, a silicon compound and a tungsten compound, wherein the silicon compound and the tungsten compound are present in amounts based on starting amounts of SiC and W metal of from 5 to 40 mole % and from 0.5 to 25 mole %, respectively, based on the sintered object overall, with a W/SiC molar ratio of 4 or less, and in which particles of at least one of tungsten carbide and tungsten silicide having an average particle diameter of 0.5 .mu.m or less are dispersed as a crystalline phase.

Abstract: A method for producing dense aluminum nitride articles having enhanced thermal conductivity is disclosed. The method comprises the steps of forming a powder compact comprising AlN alone or in combination with other ceramic compounds, adding a densification aid, subsequently exposing the compact to an environment which serves to reduce the oxygen content of the compact, and then densifying the compact by sintering or hot-pressing to provide a dense article. The densified AlN article is found to have a high thermal conductivity.

Abstract: The preparation of porous ceramic bodies by sintering certain curable organopolysiloxanes filled with silicon carbide powders. This process is advantageous in that the green bodies have relative high strengths and thus can be easily handled and, if desired, machined before sintering.

Abstract: A silicon carbide ceramic having crystalline grain boundary phases is prepared by heating a composition comprising silicon carbide, a silicate glass and a high metal content transition metal silicide, to a temperature of 1300.degree. to 2100.degree. C. under vacuum until oxygen is removed from the glass as SiO gas, and the glass that remains within the silicon carbide ceramic crystallizes.

Abstract: Process for producing ceramic compositions by dispersing elemental silicon powder in a ceramic precursor polymer containing Al, N, and C, shaping the resultant composition, and heating the shaped product to cause a reaction between the elemental silicon and the polymer to result in an intermediate composition and further heating the intermediate composition to a temperature sufficient to consolidate the char to a dense SiC--AlN solid-solution or microscopic ceramic.

Abstract: A coating composition for use with ceramic composites to reduce gas permeability of the composites as well as provide an adhesive force to the composites. The composite contains a base fabric of aluminoborosilicate fibers coated with first a carbonaceous layer, followed by a layer of silicon carbide, and a layer of a mixture of silicon carbide, aluminum phosphate, and aluminoborosilicate particles.

Abstract: The properties of silicon carbide whisker reinforced aluminum oxide, at present used for cutting tools when machining nickel based alloys, are in a very complex way related to processing and microstructure. Important parameters that have been recognized include whisker/platelet distribution, diameter, aspect ratio, surface chemistry and surface morphology. One parameter that has not been discussed is the crystal structure of the silicon carbide phase. Silicon carbide exist in a number of different polytypes, the most common with cubic or hexagonal structure. Available commercial silicon carbide contains mixed hexagonal and cubic silicon carbide-phases or single phase cubic. During sintering it is possible to transform cubic to hexagonal phase by special processing. It is shown that the hexagonal to cubic ratio strongly affects the performance in metal cutting operations and especially toughness behavior is related to a high hexagonal to cubic ratio.

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 filter material, reacts with an oxidant to form an oxidation reaction product which infiltrates the adjacent mass of filler, thereby forming the ceramic composite.

Abstract: A silicon carbide reinforced composite material comrpising a base material and, dispersed therein, a reinforcement comprising a silicon carbide whisker and an elliptical silicon carbide particle.

Abstract: The present invention discloses a ceramic cutting tool insert for chip-cutting machining. It comprises a body of generally polygonal or round shape having an upper face, an opposite face and at least one clearance face intersecting upper and lower faces to define cutting edges. The ceramic material is alumina based and comprises at least 10-40 volume % single crystal whiskers and/or platelets of carbides, nitrides and/or borides of Si, Ti, Zr, Hf, Ta and/or Nb or solid solutions thereof. The non-plane chip-forming surfaces of the insert comprise recessions and elevations that are formed in an uniaxial cold pressing operation.

Abstract: A process for the liquid phase sintering of silicon carbide, comprising forming a shaped, consolidated powder body which, not allowing for binder, comprises a powder mixture containing at least 75 wt % silicon carbide and from 1 to 25 wt % (calculated as Al.sub.2 O.sub.3) of a powder comprising a source of aluminum selected from alumina, precursors for alumina and mixtures thereof. The body is heated in a non-oxidising atmosphere to a sintering temperature of from 1500.degree. C. to 2300.degree. C. to form a liquid phase and a resultant liquid phase sintered body. In said heating step, the body is heated in the presence of a source of magnesium which is distinct from the source of aluminum and comprises at least one of magnesia, precursors for magnesia, magnesium vapour and combinations thereof, whereby said liquid phase produces secondary oxide constituent.

Abstract: A block copolymer is prepared by reacting an aluminum-nitrogen polymer and a silazane polymer at a temperature not greater than 400.degree. C. Block copolymers containing alkenyl or alkynyl groups can be crosslinked by supplying energy to generate free radicals. An AlN/SiC containing ceramic is formed by pyrolyzing the crosslinked block copolymer in a nonoxidizing atmosphere.

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 sintered ceramic composite body is manufactured by preparing a powdery mixture composed of a base material composed of either one of oxide ceramic such as alumina, mullite, magnesia, or the like, and nonoxide ceramic such as silicon nitride, sialon, or the like, and a reinforcement material composed of particles or platelet particles of silicon carbide which have a size ranging from 5 to 20 .mu.m, the particles of silicon carbide being contained at a volume ratio ranging from 3 to 50%. The platelet particles have a maximum diameter ranging from 5 to 50 .mu.m and a thickness which is 1/3 or less of the maximum diameter. The powdery mixture is molded into a shaped product, which is then sintered in a temperature range from 1,400.degree. to 1,900.degree. C. for the base material which is composed of oxide ceramic or in a temperature range from 1,500.degree. to 2,000.degree. C. for the base material which is composed of nonoxide ceramic.

Abstract: A slurry of BSAS glass powders is cast into tapes which are cut to predetermined sizes. Mats of continuous CVD-SiC fibers are alternately stacked with these matrix tapes. This tape-mat stack is warm-pressed to produce a "green" composite which is heated to burn out organic constituents The remaining interim material is then hot-pressed to form a BSAS glass-ceramic fiber-reinforced composite.

Abstract: A refractory composition consisting essentially of, for each 100 wt. % thereof, about 40 to 80 wt. % of an alumina, about 5 to 30 wt. % of a zirconia-containing grain, about 2 to 10 wt. % of a carbon, and about 1 to 12 wt. % of an oxidation and erosion resistance additive, the method of making refractory shapes utilizing such composition, and the resultant shapes.

Abstract: A lime-free silicon carbide based refractory containing about 87 wt.% silicon carbide sized -10 mesh, about 5 wt.% alumina sized -325 mesh, about 3 wt.% silica sub-micron size, and about 5 wt.% alkaliphosphate modified alumino-silicate binder. This material finds particular applicability in the construction of cast shapes and troughs for non-ferrous metal production and as a refractory lining for boiler tubes.

Abstract: A pressureless sintering method is disclosed for use in the production of whisker-toughened ceramic composites wherein the sintered density of composites containing up to about 20 vol. % SiC whiskers is improved by reducing the average aspect ratio of the whiskers to from about 10 to about 20. Sintering aids further improve the density, permitting the production of composites containing 20 vol. % SiC with sintered densities of 94% or better of theoretical density by a pressureless sintering method.

Abstract: A method for producing a sintered silicon carbide and sialon composite includes the following steps in the sequence: sintering a mixture including .alpha.-sialon powder, .alpha.-silicon nitride powder and .beta.-silicon carbide powder by hot pressing at a first predetermined temperature; and resintering the sintered mixture at a pressure of nitrogen gas ranging from 100 to 2000 atmosphere and at a second predetermined temperature 100.degree. to 200.degree. C. higher than the first predetermined temperature.

Abstract: A novel ceramic composition having high strength at high temperatures and needing no degreasing step before its sintering step, and a process for producing the same are provided,which composition is obtained by calcining a molded body composed of alumina powder and a polysilazane in an inert gas such as nitrogen, argon, etc. and/or ammonia, or under pressure and at 800.degree.-1950.degree. C.

Abstract: A ceramic fiber-ceramic composite filter having a support composed of ceramic fibers, preferably texturized, a carbonaceous layer thereover, and a silicon carbide coating over the carbonaceous layer and coated on substantially all of the fibers. A strong, tough, light weight filter is achieved which is especially useful in high temperature gas environments.

Abstract: A sintered ceramic composite body is manufactured by preparing a powdery mixture composed of a base material composed of either one of oxide ceramic such as alumina, mullite, magnesia, or the like, and nonoxide ceramic such as silicon nitride, sialon, or the like, and a reinforcement material composed of particles of silicon carbide which have a size of 1 .mu.m or less and a size ranging from 5 to 20 .mu.m, or have a size of 1 .mu.m or less and platelet silicon carbide particles having a maximum diameter ranging from 5 to 50 .mu.m and a thickness which is 1/3 or less of the maximum diameter, the particles of silicon carbide being contained at a volume ratio ranging from 10 to 50%. The powdery mixture is molded into a shaped product, which is then sintered in a temperature range from 1,400.degree. to 1,900.degree. C. for the base material which is composed of oxide ceramic or in a temperature range from 1,500.degree. to 2,000.degree. C. for the base material which is composed of nonoxide ceramic.

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: An electro-conductive ceramic comprising a non-electroconductive matrix ceramic, an electro-conductive ceramic in relatively large proportion to permit efficient electro-discharge machining (EDM) of the ceramic and ceramic whiskers of low aspect ratio and short length dispersed in the ceramic body to provide high fracture toughness, stength and hardness despite the relatively large proportion of electro-conductive ceramic. Complex geometries and features such as holes, chamfers, slots, angles, changing radii an complex curves can be electro-discharge machined into the ceramic body after hot processing or hot-isostatic pressing to achieve maximum density and mechanical properties. A particularly advantageous high temperature extrusion die, powder metal compacting die hardware and cutting tools formed of Al.sub.2 O.sub.3, TiC and SiC whiskers have been produced and tested.

Abstract: A refractory immersion nozzle which can be used for processing metal melts, and a process for producing the nozzle by providing a mixture containing alumina having a maximum grain size of 250 microns, an aggregate having less tendency than alumina to form incrustations during use of the nozzle, boron nitride, a fluxing agent, a bonding agent and a mixing liquid, molding the mixture to form a shaped body, and drying the shaped body. The nozzle inhibits accretion of slag constituents from the metal melts, and has sufficiently good spalling resistance.

Abstract: A method of producing a self-supporting ceramic composite body having therein at least one cavity which inversely replicates the geometry of a positive mold of parent metal. The method includes embedding the mold of parent metal within a conformable bed of filler to provide therein a cavity shaped and filled by the mold. The assembly is heated to melt the parent metal mold, e.g., an aluminum parent metal mold, and contacted with an oxidant to oxidize the molten parent metal to form a polycrystalline material which grows through the surrounding bed of filler, the molten metal being drawn through the growing polycrystalline material to be oxidized at the interface between the oxidant and previously formed oxidation reaction product whereby the cavity formerly filled by the mold of parent metal is eventually evacuated of the metal. There remains behind a cavity whose shape inversely replicates the original shape of the mold.

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: Self-supporting ceramic composite bodies of desired shape are produced by infiltrating a permeable self-supporting preform with polycrystalline matrix material comprising an oxidation reaction product obtained by oxidation of a parent metal precursor, such as aluminum, and optionally containing therein metallic constituents. The composite body is formed by contacting a zone of a permeable self-supporting preform, having at least one defined surface boundary spaced from said contacting zone, with a body of molten metal which is reacted with a suitable vapor-phase oxidant to form an oxidation reaction product.

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: A fiber-organic composition includes from about 5% to 50% by volume of uniformly dispersed, non-planar or three dimensionally random oriented inorganic fibers or whiskers, and a thermoplastic material such as paraffin wax. The composition also includes surfactants to promote wetting and dispersion of the inorganic fibers or whiskers. These materials are subjected to high shear mixing to form a uniform randomly oriented three-dimensional dispersion of the inorganic fibers or whiskers. After molding the mixture in such a manner so as not to disrupt the uniform, three-dimensional orientation of the fibers or whiskers, a majority of the thermoplastic material is removed leaving a shaped body or preform having sufficient strength for handling. The shaped body or preform can then be infiltrated with molten metal or the like to form a metal matrix composite.

Abstract: The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.