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

Abstract: A method for manufacturing silicon carbide whisker which has a cross-sectional diameter of greater than about 1 .mu.m by mixing a source of silicon atom in the form of grains having a mean grain diameter of at least 50 .mu.m with a carbon atom source in the presence of an element or compound of the element, the element being yttrium, calcium, manganese, aluminum, indium, or rare earth elements in an amount from about 100 to 2,000 ppm and growing the silicon carbide whisker therefrom.

Abstract: The preparation of highly densified ceramic bodies by the sintering of certain preceramic polysilazanes filled with silicon carbide powders, metal-containing sintering aids, and, optionally, polysilazane curing agents is described. Such highly densified ceramic bodies can be prepared by either a pressureless sintering process or a hot press sintering process. The compositions of this invention can be formed into desired shapes and then sintered to form ceramic, shaped bodies with high densities. One advantage of the present invention is that the green bodies have relative high strengths and thus can be easily handled and, if desired, machined before sintering. The preceramic polysilazanes useful in this invention must yield ceramic chars which contains free or excess carbon in addition to carbon in the form of silicon carbide upon pyrolysis to elevated temperatures.

Abstract: A metallizing composition essentially consists of given amounts of Ni, Nb, Cr, C, Si, Zr, SiC and W and is used for metallizing the surface of ceramics such as Si.sub.3 N.sub.4, SIALON, A1N, high purity alumina and so on. This composition forms a metallized layer having an excellent bonding strength to the ceramic surface.

Abstract: Silicon carbide whiskers such as those used in reinforcing ceramic composites are deagglomerated by dispersing the whiskers in an aqueous silane dispersant comprising a silane containing nonreactive hydrocarbon groups and reactive hydrolyzable groups, a cationic lubricant and an acid to provide a dispersant pH of about 3.5 to about 6.0. The whiskers can be deagglomerated prior to mixing with the ceramic powder used to form the composite or the whiskers, ceramic powder and aqueous silane dispersant can be mixed simultaneously. Dispersal permits classification and selection of specific aspect ratio distributions for the ceramic composite. Deagglomeration permits use of higher vol. % SiC whiskers while still attaining greater than 99% density.

Abstract: A bonding composition for silicon carbide ceramics, comprising: silicon carbide powder having a particle size of 1 to 50 .mu.m, powder carbon having a particle size of up to 15 .mu.m, silicon powder having a particle size of up to 10 .mu.m, a thermosetting resin, and a catalytically curable resin and a curing agent therefor. The composition is effective in bonding sintered silicon carbide ceramic pieces.

Abstract: A process for the production of a refractory compound, e.g. a carbide or nitride, of a metallic or non-metallic element, by reacting a mixture of a compound of the metallic or non-metallic element having at least two groups reactive with hydroxyl groups and an organic compound having at least two hydroxyl groups to produce an oxygen-containing polymeric product, and pyrolysing the polymeric product, e.g. in an inert atmosphere to produce a carbide or in an atmosphere of reactive nitrogen compound to produce a nitride, in which the reaction mixture contains an aluminium compound containing at least one group reactive with hydroxyl groups.The presence of the aluminium compound in the reaction mixture leads to an increase in the proportion of carbon in the product initially produced by pyrolysis, and to a higher purity in the refractory compound which is ultimately produced.

Abstract: A process for forming carbides of silicon or metals in fine powder or whisker form. The process comprises forming a substantially uniform and non-agglomerated dispersion of a microfine powder of an oxide of silicon or a carbide-forming metal within a matrix of a polymer, carbonizing the oxide-containing polymer in an inert atmosphere and heating the carbonized product at high temperature to cause the oxide to react with carbon to form a carbide. The polymer must have a molecular weight of at least 10,000, a high carbon yield of at least 30% by weight, and a chemical structure which is infusible or capable of being rendered infusible. The preferred polymers are polyacrylonitrile, cellulose and polyvinyl alcohol, but other polymers with similar characteristics can be employed. The process is relatively inexpensive and gives an extremely finely divided product of high purity.

Abstract: Carbides, nitrides or carbonitrides of elements from the main groups III and IV and sub-groups III, IV, V and VI of the periodic system of elements are prepared by(i) reacting compounds of the formula MX.sub.m or R.sub.n MX.sub.m-n with a reactive hydrocarbon-containing compound or a mixture of compounds which is polymerizable and which contains a reactive compound with one C--OH-group in whichM is an element of the main group III or IV or sub-group of III, IV, V or VI of the periodic system of elements,X is a halogen,R is hydrogen or alkyl or aryl,m is an integer corresponding to the valency stage of M,n is an integer from 1 to one less than the velency stage of M, and(ii) thermally decomposing the resulting product from (i) to the corresponding carbide or to the corresponding nitrides or carbonitrides with further nitridation.

Abstract: Oxidizable metallic particles having a grain size of 60 microns or less of the combination of zinc and magnesium used as heat sources in the flame spraying of refractory masses wherein the zinc magnesium form 5% or less by weight of the total mixture of oxidizable particles and refractory particles, and are used with oxidizable metallic silicon in an amount between 8 and 20% by weight, wherein one or more of silica, alumina, magnesite, chromia and/or zirconia, or silicon carbide form the incombustible refractory particles.

Abstract: A process for the preparation of preceramic metallopolysilanes is described. The process consists of reacting polysilanes with metallic compounds from which can be generated open coordination sites associated with the metallic element. Such open coordination sites can be generated by the reduction of the metallic compound with an alkali metal reducing agent, or by heating a metallic compound which has thermally labile ligands, or by the UV irradiation of a carbonyl-containing metallic compound. The metals which can be incorporated into the polysilane include aluminum, boron, chromium, molybdenum, tungsten, titanium, zirconium, hafnium, vanadium, niobium, and tantalum. These metallopolysilanes are useful, when fired at high temperatures, to form metal-containing ceramic materials.

Abstract: A refractory composition is disclosed which possesses low porosity, high density, exceptional strength and high abrasion resistance and is useful for lining fluid catalytic converter units, e.g., catalyst transfer lines, riser lines, J-bends, cyclones and all other areas where hot abrasion resistance and low thermal conductivity are desired. The composition consists essentially of by weight: (a) 44 to 89% of an abrasion-resistant refractory grain; (b) 10 to 50% of a hydraulically setting cement; (c) 1 to 6% of a filler consisting of very fine, substantially spherical particles of a metal oxide selected from the group consisting of Al.sub.2 O.sub.3, Cr.sub.2 O.sub.3, ZrO.sub.2, TiO.sub.2, clay minerals, carbon and fume SiO.sub.2 ; and (d) 0.01 to 1%, based on the total weight of the constituents (a), (b) and (c), of additives selected from deflocculants and wetting agents.

Abstract: Preceramic molding compositions capable of forming low density ceramics having acceptable strength and improved wear resistance are compositions having a particle size not larger than about 105 micrometers and comprising an intimate mixture of (A) about 50-90 parts by weight of powder ingredients comprising about 2-50% by weight of graphite powder and about 98-50% by weight of a second powder selected from silicon carbide, silicon nitride, and mixtures thereof and (B) correspondingly, about 50-10 parts by weight of a preceramic polysilazane binder.

Abstract: A ceramic sintered body comprising TiB.sub.2 as the principal component, 0.5 to 30 wt. % of SiC and 2 to 40 wt. % of ZrO.sub.2. In some cases ZrO.sub.2 includes stabilizers for tetragonal crystal, such as Y.sub.2 O.sub.3, MgO or CeO.sub.2. The sintered body has a dense structure where TiB.sub.2, ZrO.sub.2 and SiC uniformly disperse. ZrO.sub.2 is located at the grain boundary of TiB.sub.2, and inhibits the grain growth of TiB.sub.2 as well as improves the strength of the sintered body by binding it to TiB.sub.2 strongly. SiC is located not only at the grain boundary but also on the inside of both grains. Since the contract of SiC during cooling process of the sintered body is less than TiB.sub.2 and ZrO.sub.2, compressive stress is produced in SiC and around thereof. The sintered body is remarkably strengthened by the residual compressive stress, and simultaneously, the high fracture toughness is also achieved.

Abstract: The preparation of highly densified ceramic bodies by the sintering of certain organopolysiloxanes filled with silicon carbide powders, and metal-containing sintering aids is described. Such highly densified ceramic bodies can be prepared by either a pressureless sintering process or a hot press sintering process. The compositions of this invention can be formed into desired shapes and then sintered to form ceramic, shaped bodies with high densities. One advantage of the present invention is that the green bodies have relative high strengths and thus can be easily handles and, if desired, machined before sintered. The organopolysiloxanes useful in this invention must yield a ceramic char which contains free or excess carbon in addition to carbon in the form of silicon carbide upon pyrolysis to elevated temperatures.

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: In processes of forming a refractory mass on a surface, a mixture of refractory particles and oxidizable particles which react exothermically with oxygen to generate sufficient heat to soften or melt at least the surfaces of the refractory particles are sprayed against that surface to bring about formation of said refractory mass. To promote the reliable and consistent formation of a durable refractory mass, the granulometry of the particles which are sprayed in the mixture is such that the 80% and 20% grain sizes of the refractory particles (that is, the screen mesh sizes G.sub.80 and G.sub.20 through which respectively 80% and 20% by weight of the particles will pass) have a mean greater than the mean of the 80% and 20% grain sizes of the oxidizable particles and the size range spread factor f(G) of the refractory particles is at least 1.

Abstract: A method for producing a self-supporting ceramic composite structure comprising a ceramic matrix embedding a filler, includes oxidizing a parent metal to form a polycrystalline material comprising the oxidation reaction product of the parent metal and, optionally, one or more metallic constituents. The method includes heating the parent metal to provide a source of molten parent metal and a reservoir of molten metal which is in communication with the parent metal having a chemical composition which is different from the parent metal and contacting the molten parent metal with a permeable bedding of filler. The molten parent metal reacts with the oxidant to form the oxidation reaction product and is replenished by the reservoir as the reacting continues for a time sufficient to grow the oxidation reaction product to a desired extent and thereby embed at least a portion of the bedding of filler within the oxidation reaction product to form the ceramic composite structure.

Abstract: Polysilacyclobutasilazanes are reacted with chlorosilanes and/or chlorodisilanes and ammonia to provide silane-modified polysilacyclobutasilazanes having silacycles incorporated in the polymer, which silacycles are subsequently used to cross-link the silazanes.

Abstract: Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures.

Abstract: A process is disclosed for producing, at a low temperature, a high purity organic reaction product consisting essentially of silicon, hydrogen, nitrogen, and carbon. The process comprises reacting together a particulate elemental high purity silicon with a high purity reactive amine reactant in a liquid state at a temperature of from about 0.degree. C. up to about 300.degree. C. A high purity silicon carbide/silicon nitride ceramic product can be formed from this intermediate product, if desired, by heating the intermediate product at a temperature of from about 1200.degree.-1700.degree. C. for a period from about 15 minutes up to about 2 hours or the organic reaction product may be employed in other chemical uses.

Abstract: Preceramic compositions which have particular utility in providing protective ceramic coatings having low moisture sensitivity on carbon/carbon composites, graphite, carbon fibers, and other normally oxidizable materials are prepared by dispersing about 0.1-1.0 part by weight of a Group IIA metal salt with an organoborosilazane polymer solution obtained by reacting about 0.25-20 parts by weight of a trialkoxy-, triaryloxy-, or tri(arylalkoxy)boroxine with one part by weight of a polysilazane in an organic solvent and, if desired, heating the dispersion to convert it to a solution.

Abstract: A high temperature, preferably polycrystalline, ceramic fiber having a selectable diameter of between 1 and 200 microns. The fiber is stable in an inert atmosphere at a temperature above about 1700.degree. C. and is often stable even in air at a temperature above 1500.degree. C. The fiber comprises a sintered ceramic powder having a maximum particle size less than the diameter of the fiber and an average particle size less than 0.2 times the diameter of the fiber. The ceramic powder is also stable in an inert atmosphere at a temperature above about 1700.degree. C. At least 90% of the ceramic is selected from borides, nitrides, carbides, and silicides. The fiber is characterized by a smooth surface and is preferably out of round.The invention further comprises a textilable sinterable filament, comprising a flexible polymer matrix containing high temperature sinterable ceramic powder particles. The ceramic powder particles are selected from ceramic borides, nitrides, carbides, and silicides.

Abstract: The invention relates to a process for the preparation of silicon carbide whiskers by the reaction, in a non-oxidizing atmosphere, at a temperature of at least 1300.degree. C., of a charge composed of a mixture of carbon black and a source of silicon oxide, in which process the carbon black has an oxidability rate (measured by heating in air for 30 minutes at 600.degree. C.) of at least 85%, the silicon oxide source has a grain size of less than 100 .mu.m and the rate of rise in temperature between 1300.degree. and 1600.degree. C. is less than 30.degree. C.min.sup.-1 per minute if a static atmosphere prevails and at most 25.degree. C.min.sup.-1 if gas percolated. A stage of from 5 min to 5 h at 1600.degree. C. is optionally carried out.The carbon is preferably introduced into the reaction mixture in an over-stoichiometric quantity relative to the silica.The excess carbon is removed at the end of the reaction by oxidation in air at about 600.degree. C.

Abstract: Ceramic alloys or solid solutions are formed by dispersing a powdery metal alloy or intimate mixture of two alloying metals in a precarbonaceous polymer such as polyacrylonitrile, forming the mixture into a molded article such as fibers, and heating the molded articles at a temperature and in a pyrolyzation atmosphere sufficient to carbonize the polymer and cause reaction of the metals with carbon and/or the pyrolyzation gas.

Abstract: A method for producing a self-supporting ceramic composite structure, which includes a ceramic matrix embedding a filler, includes oxidizing a parent metal to form a polycrystalline material comprising the oxidation reaction product of the parent metal with an oxidant and, optionally, one or more metallic constituents, and the filler embedded by the matrix. The method includes heating a first source of molten parent metal and a reservoir source of molten parent metal and contacting the first source of molten parent metal with a permeable bedding of filler. The first source of molten parent metal is reacted with the oxidant to form the oxidation reaction product and is replenished from the reservoir as the reacting continues for a time sufficient to grow the oxidation reaction product to a desired extent and thereby embed at least a portion of the bedding of filler within the oxidation reaction product to form the ceramic composite structure.

Abstract: High surface area, submicron ceramic powders are synthesized by reducing an oxide in the presence of another metal (i.e., Mg, Al, Ca, and the like) and a source of carbon, nitrogen or boron to form a new oxide and a carbide, nitride (or carbonitride). or boride. The oxide phase can be leached out to leave submicron carbides, nitrides or borides. Alternatively milling of reacted powders allows intimate mixtures of uniform, fine grained ceramic powders to be prepared inexpensively. These multiple-phase composite powders can be formed into a body and densified using conventional techniques to form dense, fine-grained ceramic bodies. Alternatively, containment of unreacted powders and subsequent heating results in multiple-phase dense ceramics with unique microstures. Transformation toughening of composites is possible by adding zirconia or hafnia either before or after the powder synthesis step.

Abstract: There is disclosed a novel process and apparatus for continuously producing very fine, ultrapure ceramic powders from ceramic precursor reactants in a self-sustaining reaction system in the form of a stabilized flame thereof to form ceramic particles and wherein the thus formed ceramic particles are collected in the absence of oxygen.

Abstract: Low density SiC ceramics having improved bending and specific strengths are prepared by (A) intimately mixing about 50-85% by weight of SiC powder with about 15-50% by weight of a preceramic polysilazane binder, (B) pulverizing the mixture to form particles having a particle size smaller than 105 micrometers, (C) separating from those particles any particles having a particle size larger than about 105 micrometers, (D) molding the resultant composition having a particle size not larger than about 105 micrometers, and (E) pyrolyzing the molded composition in an inert atmosphere to a temperature of about 1200.degree.-1450.degree. C.In a preferred embodiment of the invention, the preceramic binder is at least one polysilazane prepared by reacting an organodihalosilane with ammonia, treating the ammonolysis product with a basic catalyst which is capable of deprotonating an NH group that is adjacent to an SiH group, and quenching the resultant product with an electrophilic quenching reagent.

Abstract: A process for the preparation of a methylpolysilane having a controlled carbon content is provided which includes the steps of heating together to form a reaction mixture at leasdt one alkoxy-functional disilane selected from the group consisting of disilanes having two, three, and four alkoxy groups bonded to the silicon atoms, and mixtures thereof, with either an alkoxy-functional silane having at least one unsaturated substituent or an unsaturated hydrocarbon compound in an amount effective to increase the carbon content of the resulting polymer. The reaction is carried out in the presence of a catalyst which is a source of alkoxide ions. The methylpolysilane polymers produced may be pyrolyzed to form ceramic compositions having increased carbon contents. The ceramics may find use as films, fibers, and coatings, as well as the many other uses to which silicon carbide ceramics have heretofore been put.

Abstract: A composite substance made of conjugated polymers that contain an inorganic moiety and an organic moiety in their molecule is provided. The conjugated polymers are produced from metal alkoxides and silane coupling agents, or else from metal alkoxides, silane coupling agents, and organic monomers. The conjugated polymers may be fired to give another composite substrate of this invention. These composite substances have both inorganic and organic characteristics, thereby attaining the excellent heat-stability, mechanical strength, resistance to chemicals, and workability.

Abstract: The preparation of highly densified ceramic bodies by sintering certain curable organopolysiloxanes filled with silicon carbide powders, metal-containing sintering aids, and organopolysiloxane curing agents described. Such highly densified ceramic bodies can be prepared by either a pressure-less or a hot press sintering process. The compositions of this invention can be formed into desired shapes and then sintered to form ceramic, shaped bodies with high densities. One advantage of the present invention is that the green bodies have relative high strengths and thus can be easily handled and, if desired, machined before sintering. The curable organopolysiloxanes useful in this invention must yield a ceramic char which contains free or excess carbon in addition to carbon in the form of silicon carbide upon pyrolysis to elevated temperatures.

Abstract: Reinforcing Si.sub.3 N.sub.4 ceramics with preoxidized SiC whiskers improves flexural strength and WEIBULL modulus over that of comparable bulk Si.sub.3 N.sub.4 ceramics or Si.sub.3 N.sub.4 ceramics reinforced with neat SiC whiskers. Hot isostatic pressing further improves the physical properties of said ceramics.

Abstract: Production of carbide shapes of silicon, titanium or vanadium by reaction of carbon with the metal in liquid phase such being carried out by heating a mixture of particles of carbon and particles of the metal rapidly to the melting point of the metal, thereby minimizing solid state reaction, and holding at a temperature and for a time sufficient to cause reaction. The metal and carbon particles are about 0.05 to 10 mm in diameter. An organic binder is used which volatilizes or dissociates upon heating.

Abstract: A method is provided for producing a self-supporting ceramic composite body having a plurality of spaced apart wall members, each wall member having a bounded cross-section for defining substantially continuous, fluid passageways. The wall members generally inversely replicate in opposed directions the geometry of a positive pattern. Each of the wall members, which are axially aligned, comprises a ceramic matrix having a filler embedded therein, and is obtained by the oxdiation reaction of a parent metal to form a polycrystalline material which comprises the oxidation reaction product of the parent metal with an oxidant and, optionally, one or more metals, e.g. nonoxidized constituents of the parent metal.

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

Abstract: A shaped article comprises a ceramic matrix and dispersed therein in the range of 5 to 30 weight percent mechanically added silicon carbide, said article having a modulus of elasticity (E) value of at least 10 percent greater than the inherent elastic modulus value of the fully dense host matrix. The articles are useful as high temperature stable reinforcement materials in composites requiring a high modulus of elasticity.

Abstract: A method is provided for producing a self-supporting ceramic or ceramic composite body by oxidation of a parent metal, the self-supporting body having a graded microstructure characterized by a plurality of zones differing from each other in one or more properties. The zones in the body are attained by altering the process conditions during formation of the body such that a zone of the oxidation reaction product formed posterior to said altering has at least one property different from a zone of the oxidation reaction product formed anterior to said altering.

Abstract: A highly loaded, uniform ceramic composite can be made by first preparing a highly loaded suspension. Due to the particle-particle interactions of a highly concentrated system, virtually any dopant can be added, including other suspensions, fibers, and whiskers. The process is particularly useful for making composites of materials which coagulate when mixed at low concentration.

Abstract: The invention relates to an organopolyarylsilane which comprises aromatic ring segments having a skelton mainly comprising an aromatic condensed ring structure derived from an organic solvent soluble pitch and organosilane segments randomly bonded thereto with an Si--C linkage intervening therebetween and is soluble in an organic solvent, and further relates to an SiC--C based continuous inorganic fiber exhibiting excellent heat resistant strength, oxidation resistance and electro-conductivity, which is obtained by spinning the above organopolyarylsilane into fiber, and after infusibilizing, heat-treating said fiber under a nonreactive atmosphere at a high temperature. The above organopolyarylsilane can be efficiently obtained in extremely high yields, by a process wherein low boiling substances produced by pyrolysis of the starting material, i.e.

Abstract: A sintered article of silicon carbide containing 2 to 12% by weight of erbium oxide, not more than 2% by weight of aluminum oxide, existing in the form of a composite oxide exhibits remarkable characteristics in resisting to oxidation, thermal shock and corrosion, and shows increased strength at elevated temperatures due to their effect to compaction of resulting structure of the sintered article due to retaining fineness of crystal grains. Those meritorious effects can be enhanced by adding to the aforementioned composition 0.5 to 6.0% by weight of at least one element selected from among titanium, vanadium, chromium, manganese, magnesium, yttrium, zirconium, niobium, molybdenum, barium, lanthanum, cerium, gadolinium, hafnium, tantalum, tungsten, thorium, and cesium or a compound of this element.

Abstract: The invention relates to a process for reducing the halogen content of polysilanes and/or polycarbosilanes having halogen bonded directly to silicon atoms in which the halogen-containing polysilanes and/or polycarbosilanes are contacted with compounds of the general formula ##STR1## where R represents hydrogen or an alkyl radical having 1 or 2 carbon atoms and R' represents hydrogen, an alkali metal or an acetyl radical.

Abstract: A process for manufacturing an organic silazane polymer which comprises reacting ammonia with a mixture of methyldichlorosilane, methyltrichlorosilane and dimethyldichlorosilane to obtain an ammonolysis product. The ammonolysis product is polymerized in the presence of a basic catalyst capable of deprotonation to obtain an organic silazane polymer. The silazane polymer may be further melted, shaped and infusibilized. The thus infusibilized product is finally sintered to obtain a ceramic material.

Abstract: Silica brick with a quartz grain structure that can be detected in the matrix and is converted to cristobalite and/or tridymite, where the quartz grain structures are surrounded by a thin layer of tridymite formed from a silica gel and/or silica sol and consisting of fine tridymite crystals matted together.

Abstract: Ceramic fibers are prepared from improved preceramic fibers having a core comprising an organosilicon preceramic polymer and at least one co-spun sheath layer comprising a synthetic film-forming polymer.

Abstract: A sintered silicon carbide matrix component for a semi-conductor diffusion furnace results from sintering a mixture of three types of silicon carbide powder. The mixture includes fine silicon carbide having an average particle size of 0.1-10 microns, intermediate silicon carbide having an average particle size of 12-30 microns and coarse silicon carbide having an average particle size of 40-200 microns. The difference between the average particle sizes of the three types of powder is at least 10 microns.

Abstract: A method for making a component for a semi-conductor diffusion furnace by blending two types of silicon carbide powders, that is, 10 parts by weight of intermediate silicon carbide having an average particle size of 10-30 microns and 10-25 parts by weight of coarse silicon carbide having an average particle size of 80-200 microns, thereby to make a mixture, admixing an organic binder with the mixture, thereafter granulating the mixture thereby to produce pellets, preforming the pellets by a rubber press thereby to produce a formed body, presintering the formed body thereby to produce a presintered body, and impregnating the presintered body with silicon and simultaneously sintering it.

Abstract: A silicon carbide sintered body containing given amounts of Mg, B and free carbon and having a density of not less than 2.80 g/cm.sup.3 is produced by adding given amounts of magnesium boride and carbon to silicon carbide powder having an average grain size of not more than 5 .mu.m, shaping and firing at 1,900.degree..about.2,300.degree. C. under vacuum or in an inert gas atmosphere.

Abstract: Reinforcing Si.sub.3 N.sub.4 ceramics with preoxidized SiC whiskers improves flexural strength and WEIBULL modulus over that of comparable bulk Si.sub.3 N.sub.4 ceramics or Si.sub.3 N.sub.4 ceramics reinforced with neat SiC whiskers. Hot isostatic pressing further improves the physical properties of said ceramics.

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 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.