Abstract: The invention relates to a polycrystalline SiC shaped body, which consists of 96% by weight to 99.5% by weight of hard-material grains having a core/shell structure, 0 to 0.1% by weight free carbon, remainder a partially crystalline binder phase; having the following properties: density at least 99.5% of the theoretical density, dark green coloring of ground sections or polished surfaces through characteristic light absorption in the orange spectral region at 1.8 to 2.2 eV, resistivity of at least 107 ohm·cm, and fracture toughness of at least 4.0 MPa.m½, measured using the bridge method.

Abstract: An object of the invention is to integrate porous ceramics and dense ceramics with an adequately high bonding strength.

Abstract: The present invention provides a process for producing alumina matrix carbide and boride reinforced ceramic composites wherein for any particular composite, the relative density is about 97% or more of the theoretical density. The composites are prepared in a container wherein the interior surfaces of the container are graphite and have a protective coating consisting of a first layer comprising silicon carbide and boron carbide with a binder and a second layer comprising silicon carbide particles, wherein the protective coating prevents carbon bleed-through and the protective coating maintains a boride-containing equilibrium atmosphere during the process.

Abstract: A dry refractory composition having superior insulating value. The dry refractory composition also may have excellent resistance to molten metals and slags. The composition includes filler lightweight material, which may be selected from perlite, vermiculite, expanded shale, expanded fireclay, expanded alumina silica hollow spheres, bubble alumina, sintered porous alumina, alumina spinel insulating aggregate, calcium alumina insulating aggregate, expanded mulllite, cordierite, and anorthite, and matrix material, which may be selected from calcined alumina, fused alumina, sintered magnesia, fused magnesia, silica fume, fused silica, silicon carbide, boron carbide, titanium diboride, zirconium boride, boron nitride, aluminum nitride, silicon nitride, Sialon, titanium oxide, barium sulfate, zircon, a sillimanite group mineral, pyrophyllite, fireclay, carbon, and calcium fluoride.

Abstract: The invention relates to a batch, in particular for the production of refractory shaped bodies, which includes a refractory, metal oxide main component containing 40 to 60% by weight of Al2O3, a phosphate bond and finely particulate SiC with a grain size of <0.2 mm, and to a process for its production.

Abstract: The present invention provides a process for producing alumina matrix carbide and boride reinforced ceramic composites wherein for any particular composite, the relative density is about 97% or more of the theoretical density. The composites are prepared in a container wherein the interior surfaces of the container are graphite and have a protective coating consisting of a first layer comprising silicon carbide and boron carbide with a binder and a second layer comprising silicon carbide particles, wherein the protective coating prevents carbon bleed-through and the protective coating maintains a boride-containing equilibrium atmosphere during the process.

Abstract: Exemplary silicon carbide ceramic bodies having inclusions therein are produced according to the invention. An exemplary ceramic body includes silicon carbide in major amounts and unreacted particles of an additive in minor amounts which are bonded to the matrix. The particles are dispersed throughout the silicon carbide, and are preferably selected from one or more of the group consisting of boron nitride, aluminum nitride and titanium diboride.

Abstract: The present invention provides a process for producing alumina matrix carbide and boride reinforced ceramic composites wherein for any particular composite, the relative density is about 97% or more of the theoretical density. The composites are prepared in a container wherein the interior surfaces of the container are graphite and have a protective coating consisting of a first layer comprising silicon carbide and boron carbide with a binder and a second layer comprising silicon carbide particles, wherein the protective coating prevents carbon bleed-through and the protective coating maintains a boride-containing equilibrium atmosphere during the process.

Abstract: The present invention provides a process for producing alumina matrix carbide and boride reinforced ceramic composites wherein for any particular composite, the relative density is about 97% or more of the theoretical density. The composites are prepared in a container wherein the interior surfaces of the container are graphite and have a protective coating consisting of a first layer comprising silicon carbide and boron carbide with a binder and a second layer comprising silicon carbide particles, wherein the protective coating prevents carbon bleed-through and the protective coating maintains a boride-containing equilibrium atmosphere during the process.

Abstract: A sintered silicon carbide has a high density and only small amounts of organic and inorganic impurities on the surface and in the vicinity of the surface, i.e., a density of 2.9 g/cm2 or more and an amount of each impurity smaller than 1.0×1011 atoms/cm2 on the surface and in the vicinity of the surface. A method for cleaning sintered silicon carbide in a wet condition comprises treating sintered silicon carbide in a step of dipping into a quasi-aqueous organic solvent, a step of dipping into an aqueous solution of an ammonium compound, a step of dipping into an aqueous solution of an inorganic acid and a step of dipping into pure water. Organic and inorganic impurities present on the surface and in the vicinity of the surface of the sintered silicon carbide are removed easily in accordance with the method.

Abstract: A composite monolithic element for use as a hot surface ignitor or the like includes first and second regions or layers. The first region or layer comprises a low pressure ejection molded mixture of silicon carbide and silicon nitride particles or other compatible mix which will alter processing art as a resistor. This resistor includes two cold portions and a hot portion intermediate thereof. The second region or layer also includes an ejection molded mixture of silicon carbide and silicon nitride particles or other appropriate mixture, while the second layer contains the same or similar compounds as the first, the rations of the compound differ so that after processing it acts as an insulator and as a support for the first layer. These first and second layers are bonded together to form a joint free mechanically continuous structure and densified.

Abstract: This invention relates to an aging resistant SiC igniter having a second layer of recrystallized SiC within the body.

Abstract: The invention provides a refractory material for use in the manufacture of dental restorations, the refractory material comprising essentially of an admixture of Silica, Silicon Carbide, Magnesium Oxide, Mono Ammonium Phosphate, and Zircon or Aluminium Oxide in predetermined proportions by weight. The material is formed as an homogenous powder and mixed with a colloidal silica based solution to form a creamy mixture suitable for casting into a silicone based impression of a prepared tooth so as to form a refractory model of said tooth. The homogenous powder may be stored in moisture resistant material until required to be mixed with said colloidal silica based solution.

Abstract: The invention relates to a method of producing refractory compositions and more particularly to a method for producing castable refractory compositions which comprises combining appropriate quantities of bulk particulate refractory aggregates substantially without pre-mixing; separately adding to the aggregate system an appropriate quantity of a pre-blended binder composition; mixing the aggregate system and the pre-blended binder composition in a mixer; and discharging the refractory composition from the mixer.

Abstract: A graphite-containing monolithic refractory material comprises at least one component selected from alumina and alumina-magnesia spinel, which are divided into selected particle size regions, artificial graphite having a selected average particle size, and pitch powder. The refractory material may optionally comprise a selected amount of silicon carbide having a selected average particle size. The graphite-containing monolithic refractory material exhibits excellent casting workability at a low moisture content, and both excellent corrosion resistance and spalling resistance. The refractory material is suitable as a casting monolithic refractory material for lining a topedo ladle car.

Abstract: A silicon carbide based composite material includes as a first component, a metal mainly consisting of aluminum or copper, and as a second component, particles mainly consisting of silicon carbide having high purity and few defects. The material is obtained by heating a compact of the raw material powder containing the first and second components at a temperature not lower than the melting point of the metal mainly consisting of aluminum or copper, and by forging and solidifying under pressure. Preferably, the silicon carbide raw material powder is prepared to have high purity by carrying out a preliminary treatment, or the material after forging or a material obtained through a conventional infiltration process is further heated at a temperature lower than the melting point of the first component. In this manner, an improved superior thermal conductivity can be obtained.

Abstract: A matrix for high-performance ceramic matrix composite containing inorganic fiber for reinforcement, which comprises silicon carbide ceramic and an oxide phase having dispersed in the solicon carbide ceramic.

Abstract: Large single crystals of silicon carbide are grown in a furnace sublimation system. The crystals are grown with compensating levels of p-type and n-type dopants (i.e., roughly equal levels of the two dopants) in order to produce a crystal that is essentially colorless. The crystal may be cut and fashioned into synthetic gemstones having extraordinary toughness and hardness, and a brilliance meeting or exceeding that of diamond.

Abstract: A ceramics dress substrate of the present invention capable of both performances of cutting a cut material with a high accuracy and dressing a diamond cutting grindstone with an excellent cutting property and an reduced wearing amount of the grindstone. This ceramics dress substrate comprises sintering a mixture of ceramics grinding particles and a silicate mineral, The ceramics grinding particles are preferably uniformed and have a scratch hardness ranging from 6 to 10. Alumina grinding particles, silicon carbide and mullite are preferably used as the ceramics grinding particles, and a kaolin mineral, pyrophyllite, montmorillonite, sericite, talc and chlorite are preferably used as the silicate mineral. The ceramics dress substrate is preferably coated with glass.

Abstract: A method of making a whisker-reinforced ceramic body by hot pressing a preform to a disc, cutting the disc into blanks and grinding the blanks to bodies of desired shape and dimension is disclosed. The preform is prepared by dispersing 10-60% by volume of a ceramic powder mixture containing conventional sintering aids and/or grain growth inhibitors in water or an organic solvent adding 1-15 wt-% starch to the dispersion; pouring the dispersion into a mold with desired shape; heating the suspension to 50°-100° C. for 2-4 hours while covering the mold to avoid water evaporation to form a preform; removing the preform from the mold; and presintering the preform in air for 10 h at a maximum temperature of about 600° C.

Abstract: This invention relates to a siliconized silicon carbide-base composite comprising at least about 71 vol % converted-graphite SiC matrix having open porosity, wherein the open porosity of the matrix is essentially filled with silicon, and the composite has a total metallic impurity content of no more than 10 ppm.

Abstract: A ceramic composite particle having an average particle size of 0.1-120 .mu.m, which comprises uniformly dispersed fine ceramic particle phases and a binder phase. The fine ceramic particle phases, each having a particle size of 1 nm to 1 .mu.m and comprising a ceramic primary particle, are bound together through the binder phase which is formed by a reaction between a sintering aid and a ceramic particle. The ceramic composite particle may be produced by heat-treating a homogeneous mixture of the ceramic particle and the sintering aid until the binder phase appears. The ceramic composite particle has a good moldability and provides a highly densified sintered body with a high strength.

Abstract: A highly heat-resistant sintered SiC fiber bonded material free of a decrease in strength and less breakable at an ultra-high temperature over 1,400.degree. C., comprising inorganic fibers which are composed mainly of a sintered SiC crystal, contain at least one kind of metal atoms selected from the class consisting of metal atoms of the 2A, 3A and 3B groups of the periodic table and are bonded nearly in the close-packed structure and 1 to 50 nm boundary layers composed mainly of carbon which are present at the interface of fibers, the less breakable highly heat-resistant sintered SiC fiber-bonded material having a density of at least 2.7 g/cm.sup.3 and an elastic modulus of at least 200 GPa, and a process for the production thereof.

Abstract: Phosphates can be removed from a hydrocarbon stream by contacting said stream with a ceramic formed of a basic material which is insoluble in the hydrocarbon stream. A ceramic as used in this patent document is a solid solution formed by calcination of a compound. The removal of the organic acid is accomplished at temperatures ranging from 20.degree. C. to 400.degree. C., a preferred temperature is between 200.degree. C. and 370.degree. C. A hydrocarbon stream consists of C.sub.5 + hydrocarbons. The basic material can be made up of one or more alkaline earth oxides, alkaline earth compounds, alkaline metal compounds, group IIIA element compounds, group IVA element compounds, group VIA element compounds. Preferred alkaline earth oxides are sodium, magnesium, potassium, calcium, aluminum and silicon. The support for the basic material can be made from any inorganic oxide.

Abstract: A ceramic formed body containing a) 5 to 70 vol % of at least on intermetallic aluminide phase which additionally may contain aluminum or/and aluminum alloy, and b) 30 to 95 vol % of one or more ceramic phases which form a solid interconnecting skeleton and wherein the intermetallic phase or phases consist of predominantly interconnected areas with average sizes of 0.1 to 10 .mu.m, is obtained by sintering, in a non-oxidizing atmosphere, of a powder metallurgically green body which consists of a mixture of finely dispersed powder of aluminum, one or more ceramic substances and maybe further metals such that the mixture contains at least one oxide ceramic or/and metallic powder which, during sintering, reacts with aluminum thereby forming an aluminide and maybe Al.sub.2 O.sub.3.

Abstract: There is provided a sintered silicon carbide with graphite added thereto having excellent lubrication characteristics. The sintered silicon carbide with graphite added thereto contains 10-30 wt. % of natural graphite flakes having an average grain size of 8-100 .mu.m and the remainder silicon carbide and a sintering aid, and having a relative density of 80-92%.

Abstract: A ceramic composition produced by the consolidation of a blend of starting components. The composition comprises a matrix with one or more of the carbides, nitrides and carbonitrides of hafnium, molybdenum, zirconium, tantalum, niobium, vanadium and tungsten, titanium nitride, and titanium carbonitride in an amount that is greater than 50 volume percent of the matrix. The matrix comprises between 60 and 99.8 volume percent of the composition. Ceramic whiskers are uniformly dispersed throughout the matrix wherein the ceramic whiskers comprises between 0.2 and 40 volume percent of the composition.

Abstract: A silicon-carbide-based inorganic fiber not only excellent in mechanical properties but also excellent in alkali durability and heat resistance, containing at least 0.1% by weight of a metal atom which is at least one member selected from the group consisting of metals belonging to Groups 2A, 3A and 3B of the periodic table and whose oxide exhibits amphoterism or basicity, having an oxygen content of 17% by weight or less, having an atomic ratio of carbon to silicon (C/Si) in the range of from 1 to 1.7, and having a density of less than 2.7 g/cm.sup.3.

Abstract: A crystalline silicon carbide fiber excellent not only in mechanical properties but also in alkali durability at high temperatures, which has a density of at least 2.7 g/cm.sup.3, contains 55 to 70% by weight of Si, 30 to 45% by weight of C, 0.06 to 3.8% by weight of Al and 0.06 to 0.5% by weight of B, the total of these elements being 100% by weight, and has a sintered structure of SiC.

Abstract: A highly corrosion-resistant silicon carbide product consisting of a sintered body having a content of .alpha.-form silicon carbide of at least 90 wt %, wherein the content of iron is at most 1 ppm, the content of aluminum is at most 5 ppm, and the content of calcium is at most 3 ppm.

Abstract: A bearing material of silicon carbide particularly useful for application in the hot water field is provided having improved corrosion resistance under increased thermal stresses wherein the bearing material is characterized by a predominantly course-grained silicon carbide matrix of pressureless sintered silicon carbide having a biamodal grain sized distribution wherein the biomodal grain size distribution is formed by from 50 to 90% by volume of prismatic, tabular, silicon carbide crystallites having a length of from 100 to 1500 .mu.m and from 10 to 50% by volume of prismatic tabular silicon carbide crystallites having a length of from 5 to <100 .mu.m.

Abstract: A refractory castable comprised of:about 45% to about 75% by weight high alumina grain;about 2% to about 35% by weight silicon carbide;about 1% to about 8% by weight carbon;about 1% to about 8% by weight calcium aluminate cement; andabout 1% to about 10% by weight fine magnesium aluminate spinel,the spinel having a grain size of less than about 150 .mu.m (100 Tyler mesh) and being comprised of about 10% to about 33% by weight magnesium oxide (MgO) and about 67% to about 90% by weight alumina (Al.sub.2 O.sub.3).

Abstract: Dense sintered bodies are provided whicha) comprise from 45 to 99.5 wt % of SiC, the SiC being present in the sintered body as a crystalline first phase, andb) comprise from 0.5 to 55 wt % of a sintering aid, from 0.5 to 30 wt % of which is selected from the group consisting of reaction products of Al.sub.2 O.sub.3 with Y.sub.2 O.sub.3, mixtures of at least one nitrogen-containing aluminum compound with reaction products of Al.sub.2 O.sub.3 with Y.sub.2 O.sub.3, mixtures of at least one rare earth oxide with at least one nitrogen-containing aluminum compound and/or Al.sub.2 O.sub.3, and from 0 to 25 wt % of which is selected from the group of the nitridic silicon compounds, the sintering aid being present in the sintered body as a second phase and optionally further phases, wherein the second phase and optionally the further phases are either amorphous to an extent of more than 10% or are present in amorphous form at the interface to the first phase to a width of at least .gtoreq.5 .ANG.

Abstract: A dense ceramic workpiece is made by a process of combining a powdered 312 component, e.g., Ti.sub.3 SiC.sub.2, with a powdered component that is soluble in the 312 component, e.g., TiSi.sub.2 in Ti.sub.3 SiC.sub.2, forming the mixture into a green body, heating the green body under pressureless sintering conditions to a temperature above a point at which a liquid is formed but below the melting point of the 312 compound to yield a dense ceramic workpiece, and thereafter cooling the dense 312 ceramic workpiece.

Abstract: A nozzle for use in continuous casting of steel includes a refractory of at least the interior surface of the nozzle and/or the portions to come into contact with molten steel that is composed of an Al.sub.2 O.sub.3 -SiO.sub.2 refractory material.

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 method of joining similar or dissimilar ceramic and ceramic composite materials, such as SiC continuous fiber ceramic composites, at relatively low joining temperatures uses a solventless, three component bonding agent effective to promote mechanical bond toughness and elevated temperature strength to operating temperatures of approximately 1200 degrees C. The bonding agent comprises a preceramic precursor, an aluminum bearing powder, such as aluminum alloy powder, and mixtures of aluminum metal or alloy powders with another powder, and and boron powder in selected proportions. The bonding agent is disposed as an interlayer between similar or dissimilar ceramic or cermaic composite materials to be joined and is heated in ambient air or inert atmosphere to a temperature not exceeding about 1200 degrees C. to form a strong and tough bond joint between the materials.

Abstract: Castable refractory for a slide gate plate is mainly formed of alumina raw material and amorphous carbon raw material of 2 to 15 wt %, and contains silicon carbide and/or boron carbide, the total content thereof being equal to 0.5 to 10 wt % (the content of boron carbide is equal to or less than 3 wt %, and when the content of boron carbide is less than 0.5 wt %, silicon carbide is set to 3 wt % or more), 2 to 10 wt % magnesia of 1 mm or less in particle size, 0.2 to 3 wt % silica fine powder of 5 micrometers or less in particle size, and 0.1 to 5 wt % salt of condensate of formalin and aromatic sulfonate.

Abstract: The present invention provides for amorphous, nanoporous, catalytic metal-containing ceramic material having a surface area in excess of 70 m.sup.2 /gm and characterized by a high content of open microporous cell structure wherein the micropores have a mean width of less than 20 Angstroms and wherein said microporous structure comprises a volume of greater than about 0.03 cm.sup.3 /gm of the ceramic. The invention also provides for a preceramic composite intermediate composition comprising a mixture of a ceramic precursor and from about 0.5 up to about 65 wt % of an organometallic compound containing a metal of Group IB, II, III, IV, IV, V, VIB, VIIA or VIII of the Periodic Table, including rare earth metals, whose pyrolysis product in ammonia or an inert atmosphere at temperatures of up to less than about 1100.degree. C. gives rise to the nanoporous catalytic ceramics of the invention.

Abstract: The invention relates to a microporous carbon-bound molded SiC body with granular SiC, secondarily formed SiC and a secondarily formed silicon compound, for use as inwall brick for lining a blast furnace as well as for use as susceptor for heating ceramic, electrically non-conductive molded bodies, inorganic melts, glasses and slags.

Abstract: Silicon carbide sintered bodies having controlled porosity in the range of about 2 to 12 vol %, in which the pores are generally spherical and about 50 to 500 microns in diameter, are prepared from raw batches containing a polymer fugitive. Sintered bodies in the form of mechanical seal members exhibit lower power consumption at low PV and, in addition, lower wear rates at high PV in comparison to commercially available silicon carbide seal members.

Abstract: Zirconium dioxide containing 2 to 40 vol. % of stabilizing oxides is embedded in the matrix material of a sintered molding consisting of an aluminum oxide/chromium oxide mixed crystal. The quantity of stabilizing oxides added is chosen so that the zirconium dioxide is predominantly tetragonal. The molar ratio of the zirconium dioxide containing the stabilizing oxides to the chromium oxide is between 1000:1 and 20:1 and the zirconium dioxide has a maximum particle size of 2 .mu.m.

Abstract: A method of heating, comprising the step of providing a line voltage of between 120V and 230 V across a ceramic igniter having a hot zone composition comprising:(a) between 50 and 80 v/o of an electrically insulating ceramic having a resistivity of at least about 10.sup.10 ohm-cm;(b) between 10 and 45 v/o of a semiconductive material having a resistivity of between about 1 and about 10.sup.8 ohm-cm;(c) between 5 and 25 v/o of a metallic conductor having a resistivity of less than about 10.sup.-2 ohm-cm; and(d) between 2.0 and 20 v/o of a resistivity-enhancing compound selected from the group consisting of metallic oxides, metallic oxynitrides, rare earth oxides, rare earth oxynitrides, and mixtures thereof.

Abstract: A ceramic igniter comprisesa pair of conductive ends,a hot zone disposed between the conductive ends, the hot zone having a density of at least about 95% of theoretical density and a composition comprising:(a) between about 50 and about 80 vol % of an electrically insulating material selected from the group consisting of aluminum nitride, boron nitride, silicon nitride, and mixtures thereof.(b) between about 10 and about 45 vol % of a semiconductive material selected from the group consisting of silicon carbide and boron carbide, and(c) between about 5 and about 25 vol % of a metallic conductor selected from the group consisting of molybdenum disilicide, tungsten disilicide, titanium nitride, and mixtures thereof, anda support upon which the hot zone is disposed, wherein at least a portion of the hot zone has a thickness of no more than 0.019".

Abstract: A composite sintered body of silicon carbide and silicon nitride having a nano-composite structure in which fine SiC particles are dispersed in Si.sub.3 N.sub.4 particles and grain boundaries and fine Si.sub.3 N.sub.4 particles are dispersed in SiC particles is produced by (a) adding at least one sintering aid, boron and carbon to a mixed powder of silicon carbide and silicon nitride to form a green body, the sintering aid being (i) Al.sub.2 O.sub.3 or AlN and/or (ii) at least one oxide of an element selected from Groups 3A and 4A of the Periodic Table, and (b) sintering the green body by HIP or by a high-temperature normal sintering method.

Abstract: Abrasive grain with significantly improved toughness is obtained by pressureless sintering of .alpha.-silicon carbide powder with oxidic sinter additives, especially aluminum oxide/yttrium oxide, which is also suitable for those applications where an ordinary silicon carbide abrasive grain is too brittle.

Abstract: Mixes suitable for casting or gunning containing a heat-resistant aggregate blend containing at least about 50 wt. % high alumina grain, silicon carbide, and zircon sand, and to the method of utilizing the same to form alkali-resistant linings in high temperature vessels that have improved resistance to build-up.

Abstract: A ceramic porous body composed principally of silicon carbide or silicon nitride which has higher strength, higher heat resistance and higher thermal shock resistance and has a large number of fine pores, and a method of producing the same. The ceramic porous body, comprised principally of silicon carbide or silicon nitride, has a pore diameter of not more than 1 .mu.m, with a porosity of not less than 35%, and has a flexural strength of not less than 100 MPa. The ceramic porous body is produced by using a silicon oligomer which is capable of producing silicon carbide or silicon nitride when calcined, mixing the silicon oligomer with a silicon carbide powder or silicon nitride powder, and/or other ceramic powder which has a mean particle diameter of not more than 1.0 .mu.m, molding the mixture into shape, then sintering the molding in a suitable atmosphere at temperatures of not less than 1200.degree. C.

Abstract: There is now provided a ceramic material comprising of alumina, 10-50% by volume, preferably 20-35% by volume, silicon carbide whiskers, 1-25% by volume, preferably 5-20% by volume, most preferably 7-15% by volume, zirconia and 1-20% by volume, preferably 3-15% by volume, titanium compound-containing cubic phase. If this cubic phase has a lattice spacing of 4.29 to 4.40 .ANG. and a zirconium content of 3-65 weight %, a material with improved performance when turning heat resistant material such as aged Iconel 718, is obtained.

Abstract: A sintered silicon carbide (SiC) body prepared by a process which contains the steps of: (a) preparing a raw batch containing: (i) a raw silicon carbide mixture containing about 10 to about 90 weight percent of an .alpha.-phase SiC powder and about 90 to about 10 weight percent of a .beta.-phase SiC powder; (ii) aluminum oxide (Al.sub.2 O.sub.3) powder, about 3 to 15 weight percent of the raw silicon carbide mixture; (iii) yttrium oxide (Y.sub.2 O.sub.3) powder, about 2 to 10 weight percent of the raw silicon carbide mixture; (iv) an organic binding agent and a dispersing agent; and (v) deionized water; (b) drying the raw batch to form a green body; (c) heating the green body at temperatures between about 400.degree. and 800.degree. C. to remove the organic binding agent and the dispersing agent; and (d) subjecting the green body to a two-stage pressureless sintering process, first at a first sintering temperature between about 1,800.degree. and about 1,950.degree. C. for 0.5 to 8.