Abstract: A silicon-containing composite body that would otherwise be brittle can be engineered to exhibit enhanced fracture toughness. Specifically, a silicon-ceramic composite body is produced, preferably by a reactive infiltration technique. The ceramic is selected such that it has a higher coefficient of thermal expansion (CTE) than does the silicon phase. At least at some point during processing, the silicon phase is at a temperature above its normal ductile/brittle transition temperature of about 500° C., and preferably above its melting point. The formed composite body containing the silicon phase is then cooled below its ductile/brittle transition. During cooling, the ceramic phase shrinks more than does the silicon phase, thereby placing the latter in a state of compressive stress. By the time the composite body has cooled to substantially ambient temperature, the induced compressive stress in the silicon phase is sufficient as to impart a measurable degree of semi-ductile character to the silicon phase.

Abstract: An electrical resistance heating element operable at extremely high temperature, up 2300° C. when used in a vacuum or in a reducing atmosphere, and up to bout 1200° C. when used in an oxidizing atmosphere. The element is formed substantially from titanium silicon carbide (Ti3SiC2), which is readily workable to enable it to be produced in different forms. It also has a higher mechanical strength than that of graphite heating elements.

Abstract: The invention relates to the field of ceramics and open-celled silicon carbide foam ceramics, which can find application, for example, as high temperature- and thermal shock-resistant silicon carbide foam. The aim of the invention is to disclose an open-celled silicon carbide foam ceramic with improved thermal shock resistance, which may be produced by a simple method. Said aim is achieved with an open-celled silicon carbide foam ceramic, the structure of which is made up of sintered silicon carbide with a 5 to 30% pore volume of closed pores with an average diameter of <20 ?m. The invention further relates to a method for the production of an open-celled silicon carbide foam ceramic, whereby coarse and fine silicon carbide powder in the ratio 20:80 to 80:20 parts are mixed and a suspension produced therefrom. An open-celled foam or open-celled network is then coated with said suspension, the foam or network material removed and sintering carried out at a temperature of >1800° C.

Abstract: A preform for use in a metal matrix composite, particularly for a magnesium metal composite. In the preform the reinforcing material typically is silicon carbide, boron nitride, titanium nitride, carbon or graphite. The binder used in the preform is sintered magnesium fluoride, which avoids the known problems which result from the high reactivity of molten magnesium metal with other binders, such as silica and alumina, which results in the formation of magnesium oxide in the reinforced composite. The presence of magnesium oxide crystals in the metal matrix adversely affects the properties of the composite. The preform generally has a void volume of from about 50% to about 95%.

Abstract: Metal-ceramic composite materials made by an infiltration technique have now been prepared using microwave energy as the heat source for thermal processing. Specifically, microwave energy has been used to heat and melt a source of silicon metal, which in turn has infiltrated carbon-containing preforms to make reaction-bonded silicon carbide composites, respectively. Both the time-at-temperature as well as the overall thermal cycle time have been greatly reduced, implying a large cost savings.

Abstract: A transition metal-containing ceramic made by the process comprising the step of pyrolyzing an organometallic linear polymer containing at least one metallocenylene unit, at least one silyl or siloxyl unit, and at least one acetylene unit to form a ceramic; where the ceramic has a ceramic yield of at least about 75% by weight. A transition metal-containing ceramic made by the process comprising the steps of: forming an organometallic linear polymer containing at least one metallocenylene, at least one silyl or siloxyl unit, and at least one acetylene unit; crosslinking said linear polymer through the acetylene units, thereby forming a thermoset; and pyrolyzing said thermoset to form a ceramic; where the ceramic has a ceramic yield of at least about 75% by weight.

Abstract: The present application is directed to ceramic compositions and, more specifically, to a silicon carbide composition and method of making it through liquid phase sintering. In one embodiment, the present invention is directed to an unsintered ceramic body including at least one liquid phase sintering aid. The unsintered ceramic body further includes a boron containing compound, a free carbon containing compound, and silicon carbide. In another embodiment, the present invention is directed to a method of making a sintered ceramic body. The method includes combining at least one liquid phase sintering aid, a boron containing compound, a free carbon containing compound, and silicon carbide to form a green ceramic, shaping the green ceramic into a ceramic body, and sintering the ceramic body.

Abstract: The present application is directed to ceramic compositions and, more specifically, to a silicon carbide composition and method of making it through liquid phase sintering. In one embodiment, the present invention is directed to an unsintered ceramic body including a rare earth metal oxide, one of a glass phase metal oxide and a glass phase metal nitride, a boron containing compound, a free carbon containing compound and silicon carbide. In another embodiment, the present invention is directed to a method of making a sintered ceramic body. The method includes combining a rare earth metal oxide, one of a glass phase metal oxide and a glass phase metal nitride, a boron containing compound, a free carbon containing compound, and silicon carbide to form a green ceramic. The method further includes shaping the green ceramic into a ceramic body and sintering the ceramic body.

Abstract: Corrosion-resistive ceramic materials include a silicon based ceramic, wherein a percentage of respective metal elements other than metal elements constituting sintering agents and silicon is not more than 10 weight ppm. The corrosion-resistive ceramic materials show a high corrosion resistance with respect to corrosive substances and suppress particle generation due to an exposure to corrosive substances. Therefore, chippings and cracks do not occur easily during machining work.

Abstract: In order to reduce wear on refractory linings due to corrosion and the infiltration of slags and molten metals, particulate materials containing TiO2 are added to the refractory products consisting of a mixture of aggregates and binding agents.

Abstract: The present application is directed to ceramic compositions and, more specifically, to a silicon carbide composition and method of making it through liquid phase sintering. In one embodiment, the present invention is directed to an unsintered ceramic body including at least one liquid phase sintering aid. The unsintered ceramic body further includes a boron containing compound, a free carbon containing compound, and silicon carbide. In another embodiment, the present invention is directed to a method of making a sintered ceramic body. The method includes combining at least one liquid phase sintering aid, a boron containing compound, a free carbon containing compound, and silicon carbide to form a green ceramic, shaping the green ceramic into a ceramic body, and sintering the ceramic body.

Abstract: A silicon-containing composite body that would otherwise be brittle can be engineered to exhibit enhanced fracture toughness. Specifically, a silicon-ceramic composite body is produced, preferably by a reactive infiltration technique. The ceramic is selected such that it has a higher coefficient of thermal expansion (CTE) than does the silicon phase. At least at some point during processing, the silicon phase is at a temperature above its normal ductile/brittle transition temperature of about 500° C., and preferably above its melting point. The formed composite body containing the silicon phase is then cooled below its ductile/brittle transition. During cooling, the ceramic phase shrinks more than does the silicon phase, thereby placing the latter in a state of compressive stress. By the time the composite body has cooled to substantially ambient temperature, the induced compressive stress in the silicon phase is sufficient as to impart a measurable degree of semi-ductile character to the silicon phase.

Abstract: A method of producing a silicon carbide powder comprising sintering a mixture containing at least a silicon source and a carbon source wherein the carbon source is a xylene-based resin. Preferable are an embodiment in which the above-mentioned silicon source is an alkoxysilane compound, an embodiment in which the above-mentioned alkoxysilane compound is selected from an ethoxysilane oligomer and an ethoxysilane polymer, an embodiment in which the above-mentioned mixture is obtained by adding an acid to a silicon source, then, by adding a carbon source, and other embodiments. A silicon carbide powder produced by the above-mentioned method of producing a silicon carbide powder wherein the nitrogen content is 100 ppm or less is preferable. A sintered silicon carbide obtained by sintering the above-mentioned silicon carbide powder wherein the volume resistivity is 1×100 &OHgr;· cm or more.

Abstract: A process is provided for forming a material comprising an M3X1Z2 phase comprising the steps of: (a) providing a mixture of (i) at least one transition metal species, (ii) at least one co-metal species selected from the group consisting of aluminum species, germanium species and silicon species, and (iii) at least one non-metal species selected from the group consisting of boron species, carbon species and nitrogen species; (b) heating said mixture to a temperature of about 1000° C. to about 1800° C., in an atmosphere within a substantially enclosed heating zone, for a time sufficient to form said M3X1Z2 phase; wherein the atmosphere has an O2 partial pressure of no greater than about 1×10−6 atm. The process provides a substantially single phase material comprising very little MZx-phase.

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: This invention relates to a corrosion-resistant member used in a region in which a gas or a plasma of a halogen-containing compound is used, in a process for producing semiconductors, especially a member used as jigs such as a supporter for supporting a material to be treated, or as an inner wall member in an apparatus for producing semiconductors, which has a high corrosion resistance to a fluorine type or a chlorine type corrosive gas, or a fluorine type or a chlorine type plasma. According to this invention, there are provided a corrosion-resistant member to be used ina region in which a gas or plasma of a halogen compound is used in a process of producing a semiconductor, wherein at least surface exposed to the gas or plasma is formed of a boron carbide sintered body having a relative density of at least 96% and containing 300 ppm or below, in a total amount, of an alkali metal, an alkalin earth metal and a transition metal, and a process for producing the same.

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: Ceramic composites of silicon carbide (SiC) grains and boron carbide (B.s4 C) grains which are uniformly coated with SiC are produced by reacting stoichiometric mixtures of silicon boride (SiB.sub.4, SiB.sub.6) and carbon (graphite or carbon black) in situ.

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: A reinforcement for composite materials is disclosed, which comprises a number of filaments of inorganic long fiber and glass and/or glass ceramic present in the gaps among the filaments and having a wire or tape form. Also disclosed is a metallic or ceramic composite material composed of a plurality of the reinforcements and a metal or intermetallic compound or ceramic which is present in the gaps among the individual reinforcements.

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: Products having single phases or solid solutions of the formula M.sub.3 X.sub.1 Z.sub.2 wherein M is a transition metal, X is Si, Al or Ge and Z is B, C or N can be prepared by taking a powdered mixture containing M, X and Z to a temperature of about 1000.degree. C. to about 1800.degree. C., optionally simultaneously under a pressure of about 5 MPa to about 200 MPa. The products so formed have excellent shock resistance, oxidation resistance and machinability. The products may also be present as composites, preferably composites which are in thermal equilibrium with the single phase or solid solutions of the formula M.sub.3 X.sub.1 Z.sub.2.

Abstract: Ceramic composites of silicon carbide (SiC) grains and boron carbide (B.s4 C) grains which are uniformly coated with SiC are produced by reacting stoichiometric mixtures of silicon boride (SiB.sub.4, SiB.sub.6) and carbon (graphite or carbon black) in situ.

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: 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: 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: 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: 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: 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: A ceramic igniter comprising: a) a lead wire, b) a ceramic substrate, and c) a braze pad having a thickness of less than about 150 microns, wherein the lead wire and ceramic substrate are placed in electrical connection by the braze pad.

Abstract: A dense, self-sintered silicon carbide/carbon-graphite composite material and a process for producing the composite material is disclosed. The composite material comprises a silicon carbide matrix, between 2 and 30 percent by weight carbon-graphite, and small amounts of sintering aids such as boron and free carbon. The silicon carbide has an average grain size between 2 and 15 .mu.m, and the carbon-graphite has an average grain size between 10 and 75 .mu.m, the average grain size of the carbon-graphite being greater than the average grain size of the silicon-carbide. The composite material has a density of at least 80 percent of theoretical density as determined by the rule of mixtures for a composite material. This density is achieved with minimal microcracking at a high graphite loading with large graphite particles. The composite material exhibits good lubricity and wear characteristics, resulting in improved tribological performance.

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: This invention relates to a black glass fiber which is resistant to oxidation at a temperature of about 1350.degree. C. and has the empirical formula SiC.sub.x O.sub.y where x ranges from about 0.5 to about 2.0 and y ranges from about 0.5 to about 2.0. This invention also relates to a process for preparing a black glass fiber comprising reacting a silicon hydride group with a silicon olefinic group in the presence of a hydrosilylation catalyst to give a cyclosiloxane polymer. The polymer is then spun into fiber, hardened and then pyrolyzed to give a black glass fiber.

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 ceramic cutting tool of a TiC-based sintered body containing 40 wt % or more of TiC, and 5 to 40 wt % of SiC whisker uniformly dispersed in the sintered body, said SiC whisker having a diameter of 0.2-1.5 .mu.m and a length of 1-20 .mu.m. The sintered body may include up to 40 wt % of Al.sub.2 O.sub.3, and may further contain sintering aid.Up to 40% by weight of TiC may be substituted with at least one of Ti, nitrides, oxides and borides of Ti, and solid-solution of said nitrides, oxides and borides of Ti to form a TiC-base composition.The TiC-base composition may be represented by (Ti.sub.a M.sub.b) (C.sub.c N.sub.d O.sub.e B.sub.f).sub.g where: M denotes at least one of transition metal elements of Groups IVa, Va and VIa, except Ti, according to the International Periodic Table; and a+b=1, 0<b.ltoreq.0.5, c+d+e+f=1, 0.5 .ltoreq.c.ltoreq.1.0, 0.ltoreq.d.ltoreq.0.5, 0.ltoreq.e.ltoreq.0.3, 0.ltoreq.f.ltoreq.0.5, 0.6.ltoreq.g.ltoreq.1.1.

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: A porous membrane produced by preparing a slurry made from at least one micropyretic substance and at least one liquid carrier. The slurry is dried into a green form having a desired geometric configuration. Combustion of the green form produces the porous membrane.

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 of from about 5 to about 40 mole %, calculated as a carbide, at least one metal or metal compound of from 0.5 to about 25 mole %, calculated as metals, selected from Ti, Nb, Ta, Cr and Mo, and the remainder of Al.sub.2 O.sub.3, and a molar ratio of the metals with respect to the silicon compounds, calculated as a carbide is about 4 or less.

Abstract: Disclosed are high density, sintered titanium carbide bodies comprising 2-10 wt % silicon carbide, up to 2 wt % free carbon and 88 to 98 wt % titanium carbide.

Abstract: A ceramic material comprising:(a) between about 50 and about 80 v/o of an electrically insulating ceramic having a resistivity of at least about 10 E+10 ohm-cm;(b) between about 10 and about 45 v/o of a semiconductive material having a resistivity of between about 1 and about 10 E+8 ohm-cm;(c) between about 5 and about 25 v/o of a metallic conductor having a resistivity of less than about 10 E-2 ohm-cm; and(d) between about 0.5 and about 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: The invention provides a ceramic composite material which includes 60-85% silicon carbide, 4-15% titanium carbide, 4-20% titanium boride, 4-13% aluminum oxide, and 1-8% titanium oxide. All constituents are in powder form, and have a particle size of between 1 and 40 microns, and a purity of at least 97%. The powdered constituents are blended and consolidated by sintering, although either hot isostatic pressing (HIPing) or by hot pressing can be used to improve certain properties such as impact resistance.

Abstract: Pressureless sintering is used to densify silicon carbide based ceramics using a compound comprising transition metal oxides and aluminum oxide at temperatures in excess of 1850.degree. C. The resulting sintered body has a density greater than 95% of its theoretical density, flexural strength in excess of 560 MPa and fracture toughness of 7.2 MPa.m.sup.1/2. The method consists of sintering and conversion of transition metal oxides into carbides in one step operation. Practically any transition metal oxide can be used. The sintered ceramic bodies made by the present invention consist of silicon carbide matrix phase and Al.sub.2 O.sub.3 and transition metal carbide phases.

Abstract: A method for producing alumina-silicon carbide ceramic powders by in situ production of silicon carbide particles by introducing a pyrolyzable carbon source, preferably a gaseous hydrocarbon, into a reactor containing an alumino-silicate, pyrolyzing the pyrolyzable carbon source to form carbon particles in situ, wherein the carbon particles are capable of reacting with a silicate in the alumino-silicate to form carbide products, and then reacting the silicate and the carbon particles in situ at an effective temperature, preferably at least 1450.degree. C. and more preferably at least 1500.degree. C., for a sufficient time to transform the alumino-silicate and the pyrolyzable carbon source into the composite ceramic powder having alumina (Al.sub.2 O.sub.3) and silicon carbide (SiC) as major phases.

Abstract: Disclosed is a method for preparing high density titanium carbide ceramic bodies. The method entails mixing titanium carbide powder with a preceramic organosilicon polymer. The mixture is then molded and sintered under pressure or by a pressureless process.

Abstract: A ceramic cutting tool formed of a TiC-based sintered body contains 40 wt % or more of TiC, and 5 to 40 wt % of SiC whisker uniformly dispersed in the sintered body. The SiC whisker has a diameter of 0.2-1.5 .mu.m and a length of 1-20 .mu.m. The sintered body may contain up to 40 wt % of Al.sub.2 O.sub.3, and further sintering aids. Up to 40% by weight of the TiC may be substituted with at least one of Ti, nitrides, oxides and borides of Ti, and solid-solutions of these nitrides, oxides and borides of Ti to form a TiC-base composition. The TiC base composition may be represented by the formula (Ti.sub.a M.sub.b) (C.sub.c N.sub.d O.sub.e B.sub.f).sub.g, in which M denotes at least one transition metal element of Groups IVa, Va and VIa according to the International Periodic Table, except Ti; and a+b=1, 0<b.ltoreq.0.5, c+d+e+f=1; 0.5 c.ltoreq.1.0; 0.ltoreq.d.ltoreq.0.5; 0.ltoreq.e.ltoreq.0.3; 0.ltoreq.f.ltoreq.0.5; and 0.6.ltoreq.g.ltoreq.1.1.

Abstract: A sintered composite boron carbide body with SiC and/or TiB.sub.2 having a grain size of the order of nanometers and distributed among B.sub.4 C crystal grains and/or within the B.sub.4 C crystal grains is produced by hot-pressing a powder mix, which is composed of 44-99.5 vol. % B.sub.4 C, 0.5-60 vol. % SiC and/or 0.5-60 vol. % TiC, at 1,800-2,300.degree. C. for 5-600 minutes.

Abstract: The present invention relates to a ceramic cutting insert containing whiskers for chip forming machining of steel and having improved mechanical, thermal and wear properties. The insert comprises besides the oxide-based matrix 5-50% by volume, preferably 10-40% by volume, of homogeneously dispersed whiskers of carbides, nitrides and/or borides of titanium and/or zirconium and, where applicable, solid solutions thereof. A part of the whiskers may be replaced by whiskers of silicon carbide. The properties of the composite material can be further modified by coating the whisker material with thin layers. The whiskers reinforced cutting material shows an improved toughness behaviour and resistance to thermal crack formation without having a negative influence on the wear resistance to any appreciable extent.