Abstract: The present invention provides a dense SiC-infiltrated composite material or a dense carbon-fiber-reinforced SiC-infiltrated composite material and a dense SiC-infiltrated composite material with granular carbon dispersed therein that are unlikely to bond to a carbon crucible and that have excellent heat and oxidation resistance. This composite material can be obtained by infiltrating molten carbon-silicide of Mo that is approximately expressed as Mo.sub.3 Si.sub.2 C or a eutectic mixture of carbon-silicide and silicon carbide into a silicon-carbide-based preform having 10 to 60 vol. % of continuous voids and then cooling and solidifying the melt.

Abstract: The present invention relates to a method for the formation of amorphous boron silicon oxycarbide fibers and crystalline boron-doped silicon carbide fibers wherein the method comprises preparing a blend of a siloxane resin and a carborane-siloxane oligomer, forming the blend into green fibers, and then curing and pyrolyzing the fibers.

Abstract: High emissivity molybdenum silicide-containing ceramic and metal-ceramic products are provided, especially for use as heaters in rapid solidification processing (RSP) and rapid thermal processing (RTP). Novel designs incorporating such heaters are also provided.

Abstract: A sintered silicon carbide containing nitrogen is obtained by sintering a mixture of a powder of silicon carbide and a nonmetallic auxiliary sintering agent. The sintered silicon carbide has a density of 2.9 g/cm.sup.3 or more and contains 150 ppm or more of nitrogen. The sintered silicon carbide preferably has a volume resistivity of 1 .OMEGA..multidot.cm or less and contains .beta.-silicon carbide in an amount of 70% or more of total silicon carbide components. Nitrogen can be introduced into the sintered silicon carbide by adding a nitrogen source, for example, an amine such as hexamethylenetetramine, ammonia, and triethylamine in the production of the powder of silicon carbide which is used as the material powder for producing the sintered silicon carbide or by adding the nitrogen source in combination with the nonmetallic auxiliary sintering agent in the production of the sintered silicon carbide.

Abstract: A method for forming dense ceramics, particularly a ceramic coating by a low temperature treatment is provided. The method for forming ceramics according to the invention is characterized in that a polysilazane having a number-average molecular weight of 100 to 50,000 or a modified polysilazane thereof is subjected to a heat treatment, then exposed to an atmosphere containing water vapor or immersed in distilled water containing a catalyst, or both, or is brought into contact with Pd.sup.2+ ions and water, the polysilazane having a skeleton comprising the unit represented by the following general formula (I): ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, a group other than the above and having a carbon atom directly attached to the silicon atom, an alkylsilyl group, an alkylamino group and an alkoxy group; with the proviso that at least one of R.sup.1, R.sup.2 and R.sup.3 is a hydrogen atom.

Abstract: Simulated diamond gemstones are produced by faceting and polishing bulk single crystals of colorless synthetic aluminum nitride or aluminum nitride:silicon carbide alloys.

Abstract: A sintered hard material according to the invention comprises 0.02 to 0.10 wt % of one or more metals selected from the group consisting of Fe, Co and Ni, 0.3 to 3.0 wt % of one or more compounds selected from the group consisting of carbides, nitrides and carbonitrides of transition metals of the IVa, Va and VIa groups of the periodic table and a residue of tungsten carbide component having an average particle size of 0.5 .mu.m or less, the tungsten carbide component containing WC and W.sub.2 C in a proportion W.sub.2 C/(WC+W.sub.2 C) of between 0.01 and 0.15, the W.sub.2 C in the tungsten carbide component having a lattice constant reduced by 0.3 to 1.5 %.

Abstract: Novel methods for the preparation of polymers useful as precursors to ceramic materials by catalytic activation of Si--H bonds are disclosed. The methods comprise reacting, in the presence of a catalyst effective to activate Si--H bonds, Si--N bonds, or both, and/or a reactive solvent, a polymer in the form of a polysilane, polysilazane, polysiloxane or polycarbosilane with a reactant having the structural formula R--X--H, wherein X is NR' or O, R is H, organic, silyl, siloxyl, silazanyl or carbosilyl and may contain at least one additional X--H group, and R' is H, amino, silyl or silazanyl, to produce a modified polymer containing at least one Si--X bond. Polymers produced by these methods are also disclosed.

Abstract: There is provided a ceramic matrix composite whose strength is less degraded even in a high-temperature range at, especially, 1,400.degree. C. or higher, and a method of manufacturing the ceramic matrix composite. The ceramic matrix composite in which reinforcements are arranged in a ceramic matrix to be combined to the ceramic matrix is characterized in that the main component of the ceramic matrix consists of silicon carbide and molybdenum silicide based compound, the density ratio of the matrix is 90% or higher.

Abstract: A method of manufacturing a semiconductor device is provided superior in planarization, crack resistance, and moisture resistance, and with no corrosion in wiring while the manufacturing cost is suppressed without increasing the number of manufacturing steps in forming an interlayer film therein. This method includes the step of forming a silicon oxide film on a substrate so as to cover a first wiring formed with a silicon oxide film therebetween. A thick-film inorganic SOG film is coated on the silicon oxide film, and then a thermal treatment is applied. Next, a silicon oxide film is formed, and a via hole is formed according to a predetermined mask. By carrying out a thermal treatment at the temperature of 150.about.550.degree. C. and at the pressure of not more than 10.sup.-3 Torr with a portion of the thick-film inorganic SOG film exposed at a side surface of the via hole, residual gas such as CO.sub.2, and H.sub.2 O adsorbed to the side surface of the via hole is released.

Abstract: The invention relates to new amorphous, high-strength SiBN(C) fibers which are at the same time resistant to high-temperature creep, their production and use. The fibers have a strength at room temperature of >2.5 GPa, a modulus of elasticity of >250 GPa and a creep value m of from 0.4 to 1 (in accordance with standard BSR test, 1 hour, 1400.degree. C.).

Abstract: The object of the present invention is to provide a taphole mix for use in a molten metal taphole which has improved resistance to both wear and corrosion and enables prolonged tapping of iron and reduces difficult drilling. The taphole mix of the present invention is characterized in that it comprises a refractory base material in an amount of 65 to 92 wt % and a binder in an amount of 8 to 35 wt %, the binder consisting of an anhydrous coal tar having a fixed carbon content of 32.5 wt % or above.

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 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 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: This invention pertains to a method for production of polycrystalline ceramic fibers from silicon oxycarbide (SiCO) ceramic fibers wherein the method comprises heating an amorphous ceramic fiber containing silicon and carbon in an inert environment comprising a boron oxide and carbon monoxide at a temperature sufficient to convert the amorphous ceramic fiber to a polycrystalline ceramic fiber. By having carbon monoxide present during the heating of the ceramic fiber, it is possible to achieve higher production rates on a continuous process.

Abstract: A composite powder having a specific surface area of 7 m.sup.2 /g or more is produced by mixing a silicon powder with a carbonaceous powder and a sintering aid powder, and heat-treating the resultant mixed powder in a nitrogen-containing atmosphere at a temperature of 1,450.degree. C. or lower thereby nitriding and carbonizing silicon in the mixed powder. The temperature elevation speed in the heat treatment for nitriding and carbonizing is less than 2.degree. C./minute at least in a range from a temperature at which the nitriding and carbonizing of silicon starts to take place to a temperature at which the composite powder is kept for nitriding and carbonizing of silicon. The composite sintered body is produced by sintering such a composite powder at a temperature of 1,600.degree. C. to 2,200.degree. C.

Abstract: A boron-nitride-containing material of multi-component system is obtained at a low cost by heating a mixed powder containing a boride and an oxide in a nitrifying atmosphere, whereby a part or the whole of the oxide is reduced with the element bonded to boron of the boride to convert the raw materials to one or more kinds of an oxide having less bonded oxygen, an acid nitride, a nitride, a carbide, and a boride and also boron nitride is formed. A sintered product of a boron-nitride-containing material is obtained by packing a mixed powder containing borides in a heat-resistant mold and heating the packed powders in a nitrifying atmosphere while restraining the packed powders by the mold. The sintered product is obtained in which neither expansion nor deformation occurred and no cracks formed.

Abstract: The present invention provides for microporous ceramic materials having a surface area in excess of 70 m.sup.2 /gm and an 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 finely divided silicon carbide or silicon nitride, whose pyrolysis product in inert atmosphere or in an ammonia atmosphere at temperatures of up to less than about 1100.degree. C. gives rise to the microporous ceramics of the invention. Also provided is a process for the preparation of the microporous ceramics of the invention involving pyrolysis of the ceramic intermediate under controlled conditions of heating up to temperatures of less than 1100.degree. C. to form a microporous ceramic product.

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

Abstract: A 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: The invention relates to a process for the preparation, by nitriding, of a refractory powder containing more than 40% of silicon nitride from spent contact masses issuing from chlorosilane synthesis. The process involves mixing with the copper-free spent mass, silicon or a silicon-rich alloy and optionally a refractory compound to adjust the non-oxidised silicon content to a predetermined value >30%, heating the mixture in a nitrogen atmosphere to trigger the exothermic nitriding reaction, then reducing the product obtained to powder. The refractory powder thus obtained can be mixed with an organic binder to produce taphole blocking masses for blast furnaces or electric furnaces for pyrometallurgy.

Abstract: An electron beam of more than 1.times.10.sup.19 e/cm.sup.2 .multidot.sec is irradiated to metastable metal oxide particles such as .theta.-Al.sub.2 O.sub.3 particles or the like disposed on an amorphous carbon film. A phase transformation or the like of the metastable metal oxide particles is occurred by the electron beam irradiation. Thus, stable metal oxide ultrafine particles such as an .alpha.-Al.sub.2 O.sub.3 ultrafine particle 2 whose diameter is more tiny than the metastable metal oxide particles used, and a metal ultrafine particle composed of an oxide such as Al ultrafine particles are produced.

Abstract: A composite sintered body of silicon nitride and silicon carbide is manufactured by sintering a composite powder or green body of silicon nitride and silicon carbide in a nitrogen gas atmosphere. The composite powder having a percentage of .alpha.-silicon nitride which is at least 30% based on all silicon nitride is produced by mixing a silicon powder with a carbonaceous powder and a sintering aid powder, and heat-treating the resultant mixed powder in a nitrogen-containing atmosphere at a temperature of 1,450.degree. C. or lower thereby nitriding and carbonizing silicon contained in the mixed powder to produce a composite powder, a temperature elevation speed being less than 2.degree. C./minute. The composite green body having a percentage of .alpha.

Abstract: A ceramic matrix composite material comprising a matrix containing silicon carbide as the primary component and silicon nitride as the secondary component is disclosed. The silicon nitride includes not more than 1% by weight of iron and reinforcements mixed and dispersed. The ceramic matrix composite material is manufactured, for example, by forming a matrix containing reaction sintered silicon carbide as the primary component and nitriding the free metal silicon produced in the sintering process so that the free metal silicon will be converted to fine silicon nitride particles. Said metal silicon used for reaction sintering already contains iron. These processes enable the containing of a comparatively large amount of reinforcements, as well as the improvement of heat resistance of the sintered compact and the suppression of the deterioration of reinforcements.

Abstract: A silicon nitride sintered body has a composition consisting essentially of 80 to 93% by weight .beta. silicon nitride, 7 to 20% by weight grain boundary phases consisting essentially of (i) at least two rare earth elements, wherein yttrium is considered a rare earth, and strontium which, calculated as SrO, is 0.5 to 5% by weight, and (ii) at least two of Si, N, O and C; and (c) silicon carbide particulate present in the amount of about 5 to 35 parts by weight per 100 parts by weight of components (a) and (b), said SiC being substantially homogeneously dispersed within said sintered body. Such a ceramic has high strength and long term durability, and is especially suited for industrial applications such as components for gas turbine and automotive engines.

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: High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium, along with silicon carbide.

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: In-situ Si.sub.3 N.sub.4 whisker growth mechanisms have enhanced the microstructure of ceramic materials such as SiC through controlled growth of elongated beta-type Silicon Nitride grains. During liquid phase sintering at temperatures not exceeding 1850.degree. C., alpha-type Silicon Nitride dissolves into the liquid phase and reprecipitates as an elongated or acicular beta modification. The Si.sub.3 N.sub.4 reinforced microstructures can be formed by the controlled recrystallization of beta-type Silicon Nitride. In-situ whisker growth is enhanced or optimized through the use of thermal treatments and/or additions of seed materials. Finely divided beta-type Silicon Nitride particles which are insoluble in the liquid phase during sintering, and therefore have been used to provide nucleation sites for whisker growth are employed. Thermal treatments have been designed to promote directional growth (elongation) as opposed to development of less elongated type grains.

Abstract: A method of crosslinking a silazane polymer having Si--H bonds in which the polymer is mixed with a crosslinker selected from alkenyl functional cyclosiloxanes and alkenyl functional cyclosilazanes and a crosslinking promoter and then heated to a temperature sufficient to crosslink the silazane polymer. The mixture of the silazane polymer, crosslinker and promoter is useful in the formation of ceramic matrix composites.

Abstract: The present invention provides for microporous ceramic materials having a surface area in excess of 100 m.sup.2 /gm and an 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 0.05 cm.sup.3 /gm of the ceramic. The pyrolysis product of ceramic precursor oligomers or polymers having a number average molecular weight in the range of from about 200 to about 100,000 g/mole in an ammonia atmosphere at temperatures of up to less than about 1200.degree. C. gives rise to the microporous ceramics of the invention. Also provided is a process for the preparation of the microporous ceramics of the invention involving pyrolysis of the ceramic precursor under controlled conditions of heating and with intermediate hold times, up to temperatures of less than 1200.degree. C., preferably less than 1000.degree. C., to form a microporous ceramic product.

Abstract: A ceramic porous body for a filter or a catalyst carrier, having a structure in which voids each having the same volume as that of a sphere of 10 .mu.m to 500 .mu.m in diameter are formed and the voids are communicated with each other through smaller fine pores, the ceramic porous body having a volume fraction of the voids and the fine pores of from 15% to 60% and being formed of components 70% or higher by volume of which is silicon nitride.

Abstract: A superplastic silicon nitride sintered body which is a sintered body of silicon nitride and which has superplasticity such that when a compression or tensile stress of from 30 to 2000 kg/cm.sup.2 is applied thereto at a temperature within a range of from 1350.degree. to 1650.degree. C., it deforms at a deformation rate of from 10.sup.-4 /sec to 10.sup.-1 /sec.

Abstract: A method for refined silicon carbide powder comprises attrition milling silicon carbide material in a liquid medium with a milling media to obtain refined silicon carbide particles having a specific surface area of at least 15 m.sup.2 /g, and preferably 20 m.sup.2 /g, with a median particle size of less than 0.5 microns, and preferably 0.25 microns. The invention includes the finished powder.

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. C. 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: Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

Abstract: The present invention provides for microporous ceramic materials having a surface area in excess of 70 m.sup.2 /gm and an 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 finely divided silicon carbide or silicon nitride, whose pyrolysis product in inert atmosphere or in an ammonia atmosphere at temperatures of up to less than about 1100.degree. C. gives rise to the microporous ceramics of the invention. Also provided is a process for the preparation of the microporous ceramics of the invention involving pyrolysis of the ceramic intermediate under controlled conditions of heating up to temperatures of less than 1100.degree. C. to form a microporous ceramic product.

Abstract: The present invention provides a low-friction ceramic having a lowered coefficient of friction and an enhanced strength. The ceramic comprises as the matrix phase a nonoxide ceramic containing silicon, such as Si.sub.3 N.sub.4 or SiC and an iron compound in an amount of about 5 to 40% by weight dispersed in the matrix phase. This ceramic is excellent in the ability to adsorb lubricating oil, has a low coefficient of friction, is almost free from pores, and has a strength equal to or higher than that of a ceramic containing no iron oxide.

Abstract: A method of producing a composite powder by providing particles of (I) tungsten, niobium, zirconium, titanium or mixtures thereof, (II) silicon and (III) carbon in a proportion relative to each other so as to possess an overall chemical composition in that segment of the ternary diagram of FIGS. 2(a), 2(b), 2(c) and 2(d) designated A, and subjecting the particles to a mechanical alloying process under conditions and for a time sufficient to produce the composite powder. Also disclosed is a method of forming a substantially oxygen-free composition of matter comprising a matrix substance of WSi.sub.2, NbSi.sub.2, ZrSi.sub.2, TiSi.sub.2 or alloys thereof having SiC dispersed therein, the method comprising consolidating the above-described composite powder. Also disclosed is a method of forming oxidation- and wear-resistant coatings by subjecting the composite powder whose composition lies in segment A to a metallurgical process such as plasma spraying.

Abstract: A silicon nitride sintered body has a composition consisting essentially of 85 to 94% by weight .beta. silicon nitride, 6 to 15% by weight grain boundary phase consisting essentially of (i) at least two rare earth elements, wherein yttrium is considered a rare earth, and, optionally, strontium which, calculated as SrO, is 02 percent by weight of the total body, and (ii) at least two of Si, N, O and C, and an additive consisting essentially of a metal carbon compound present in the amount of about 0.2 to 3.5% by volume. The additive is substantially homogeneously dispersed within the sintered body. The sintered body has a microstructure wherein (i) the .beta. silicon nitride grains are acicular and have an average grain width ranging from 0.5 to 1.5 .mu.m, (ii) at least 25% of the grains have width greater than 0.7 .mu.m, and at least 10% of the grains have width greater than 1 .mu.m, and (iii) no more than 5% of grains have width greater than 3.5 .mu.

Abstract: A silicon nitride-based sinter contains as component elements thereof magnesium in the range of from 0.1 to 1.5% by weight, aluminum in the range of from 0.1 to 3.5% by weight, carbon in the range of from 0.01 to 6% by weight, and oxygen in the range of from 0.2 to 5% by weight, the balance consisting essentially of silicon, nitrogen, and impurities. This sinter is obtained by sintering a ceramic mixture comprising 0.5 to 6% by weight of a MgO.Al.sub.2 O.sub.3 spinel structure, 0.1 to 20% by weight of silicon carbide, not more than 1% by weight of silicon oxide, and the balance substantially of silicon nitride and impurities. Owing to the incorporation of the MgO.Al.sub.2 O.sub.

Abstract: A boron-nitride-containing material of multi-component system is obtained at a low cost by heating a mixed powder containing a boride and an oxide in a nitrifying atmosphere, whereby a part or the whole of the oxide is reduced with the element bonded to boron of the boride to convert the raw materials to one or more kinds of an oxide having less bonded oxygen, an acid nitride, a nitride, a carbide, and a boride and also boron nitride is formed. A sintered product of a boron-nitride-containing material is obtained by packing a mixed powder containing borides in a heat-resistant mold and heating the packed powders in a nitrifying atmosphere while restraining the packed powders by the mold. The sintered product is obtained in which neither expansion nor deformation occurred and no cracks formed.