Abstract: Ceramic sintered mass having a mean grain size of no more than 3 microns of high toughness even at high temperatures is obtainable, the mass comprising 30-99.5% by weight of a component A as defined below and the balance being a component B as defined below:Component A: zirconia having a tetragonal and/or cubic system content of no less than 90% by weight, with the proviso that the tetragonal/cubic system ratio by weight is no less than 0.25, said zirconia including a stabilizer of Y.sub.2 O.sub.3, CaO, MgO, etc.Component B: one or more of borides, carbides and nitrides of Al, Si and an element in the groups 4a, 5a and 6a of the periodic table, and Al.sub.2 O.sub.3.The balance may incorporate a further component C, such as SiO.sub.2, Fe.sub.2 O.sub.3 and TiO.sub.2 and the like of no more than 3% by weight in the sintered mass.

Abstract: A process for producing a silicon carbide heating element is disclosed comprising: adding boron or a boron compound in an amount corresponding to from 0.3 to 3.0% by weight as boron, and carbon or a carbon compound in an amount corresponding to from 0.1 to 6.0% by weight as carbon, to a SiC powder having an average particle size of 1.0.mu. or less; blending and molding the mixture; conducting a primary sintering in vacuum or in an inert atmosphere, except nitrogen; and thereafter conducting a secondary sintering at from 1500.degree. to 2300.degree. C. in a pressurized nitrogen atmosphere to produce a silicon carbide heating element having a density of at least 80% based on the theoretical density and an electrical resistivity of 1.0 .OMEGA.-cm or less.

Abstract: A high toughness sintered body is described, consisting essentially of from 40 to 99.5% by weight of Component A, and 0.5 to 60% by weight of Component B, wherein the mean grain size of the sintered body is 3 microns or less, and Components A and B are as follows:Component A: ZrO.sub.2 containing a stabilizer, such as Y.sub.2 O.sub.3, CaO, and MgO, in which the fraction of the tetragonal and cubic ZrO.sub.2 constitutes at least 90% by weight, and the ratio of the tetragonal ZrO.sub.2 to the cubic ZrO.sub.2 is at least 1/3; andComponent B: at least one of Al.sub.2 O.sub.3 and TiN, with impurities being 3% by weight or less of SiO.sub.2, 0.5% by weight or less of Fe.sub.2 O.sub.3, and 0.5% by weight or less of TiO.sub.2, provided that the total amount is 3% by weight or less.

Abstract: A method for manufacture of a high toughness sintered body, characterized by sintering a shaped body of a mixed powder consisting essentially of from 40 to 70% by weight of a first component of powdered ZrO.sub.2 containing at least one stabilizer selected from the group consisting of Y.sub.2 O.sub.3, CaO, and MgO and having an average particle diameter of not more than 1.mu. and from 30 to 60% by weight of a second component of powdered .alpha.-Al.sub.2 O.sub.3 having an average particle diameter of not more than 1 .mu.m, which mixed powder may also contain not more than 3% by weight of SiO.sub.2, not more than 0.5% by weight of Fe.sub.2 O.sub.3, or not more than 0.5% by weight of TiO.sub.2 in a combined proportion of not more than 3% by weight at a temperature in the range of from 1400.degree. C. to 1600.degree. C. under normal pressure thereby producing a sintered body wherein at least 90% by weight of ZrO.sub.

Abstract: Processes for the production of a silicon nitride sintered body are disclosed. One process comprises molding a mixed powder of 100 parts by weight of metallic silicon with a maximum particle size of 20 .mu.m or less and 0.2 to 2 parts by weight (calculated as chromium oxide) of a chromium component and, thereafter, reaction sintering the mold in a nitrogen gas or in a non-oxidizing atmosphere containing nitrogen gas at a temperature of 1,300.degree. to 1,500.degree. C. This invention provides further process which comprises molding a mixed powder of 100 parts by weight of metallic silicon with a maximum particle size of 20 .mu.m or less, 0.2 to 1 part by weight (calculated as chromium oxide) of a chromium component, and further 10 to 20 parts by weight of an oxide component of one or more of the oxides of yttrium, lanthanum, cerium, gadolinium, and erbium, reaction sintering the above-prepared mold, and thereafter, hot pressing the reaction sintered body.

Abstract: A sintered silicon nitride products and processes for the fabrication thereof are described, wherein the product comprises from 60 to 98.9% by weight of silicon nitride, from 0.1 to 15% by weight of one or more chromium components selected from metal chromium, chromium oxide, and chromium nitride, and from 1 to 25% by weight of one or more oxides selected from oxides of rare earth elements, scandium oxide, yttrium oxide, aluminum oxide, zirconium oxide and silicon dioxide.

Abstract: A silicon nitride sintered product and processes for the production thereof are described, wherein the product comprises from 75 to 97.9% by weight of silicon nitride, from 2 to 20% by weight of yttrium oxide and cerium oxide in a molar ratio of cerium oxide to yttrium oxide of 0.4/1 to 4/1, and from 0.1 to 8% by weight of aluminum oxide.

Abstract: A process for producing a silicon nitride sintered product having high toughness is described, comprising blending from 97 to 57% by weight of metallic silicon powder having a maximum particle size of 25 .mu.m or less with from 1 to 15% by weight, calculated as TiN, of a TiN powder having a maximum particle size of 20 .mu.m or less or a powder of titanium component capable of changing into TiN during reaction sintering, and from 2 to 28% by weight of one or more components selected from the group consisting of AlN, Al.sub.2 O.sub.3, SiO.sub.2 and oxides of rare earth elements, molding the resulting mixture, carrying out reaction sintering in a nonoxidizing atmosphere of a nitrogen gas or a nitrogen-containing mixed gas, and thereafter resintering in the same atmosphere at a temperature of from 1,600.degree. C. to 2,200.degree. C.

Abstract: Sintered cubic boron nitride consisting of 80 to 20% by volume of the following component (a), with the balance being essentially the following component (b), and a process for producing such nitride are disclosed:(a) cubic boron nitride;(b) a cermet containing the following sub-components (1), (2) and (3):(1) TiC and/or TiC-TiN, part of which may be replaced by a carbide, a nitride, a boride and/or a silicide of a transition metal of the group IVa, Va and VIa of the Periodic Table;(2) Fe, Co and/or Ni; and(3) Mo and/or Mo.sub.2 C.

Abstract: A process for producing silicon carbide heating elements is described comprising:a primary sintering wherein a mixture including SiC powder, boron or a boron compound, and carbon or a carbon compound in specific proportions, is molded and sintered to obtain a sintered product having from 70 to 95% of the theoretical density; anda secondary sintering wherein the sintered product obtained in the primary sintering is further sintered at each temperature from 1,600.degree. C. to 2,200.degree. C. to obtain a sintered product having a density of at least 80% of the theoretical density and a specific resistivity of not more than 1.0 .OMEGA.-cm.

Abstract: A silicon nitride based ceramic tool is disclosed which is prepared from the starting powder compositions surrounded by and including the lines defined by the points A, B, and C and preferably D, E, and F in the FIGURE.

Abstract: A process for producing high density sintered product which comprises molding a composite of an inorganic powder and an organic resin, burning off the organic resin, coating the surface of the molding with a rubber film, pressing said moldings under 2 ton/cm.sup.2 or more of isostatic pressure, and sintering.

Abstract: A high strength silicon nitride sintered material having a modulus of rupture of about 100 kg/mm.sup.2 or more, which is prepared by sintering a mixture of about 88.7 to 98% by weight of silicon nitride (Si.sub.3 N.sub.4) and the balance a sintering aid comprising Al.sub.2 O.sub.3, Y.sub.2 O.sub.