Abstract: A low-temperature firing ceramic composition contains Sr2MgSi2O7 crystals forming a major crystal phase of the composition. This composition can be produced, for example, by a process including the steps of (a) mixing together a silica powder, a magnesia powder and a strontium oxide powder to obtain a powder mixture; (b) subjecting the powder mixture to a calcination at a temperature of 1,000-1,200° C. to obtain a calcination product containing Sr2MgSi2O7 crystals; (c) mixing the calcination product with alumina powder, boron oxide powder, lithium oxide powder, binder and ethanol to obtain a powder mixture; (d) granulating the powder mixture; (e) shaping the resulting granules into a green body; (f) compacting the green body by a hydrostatic pressing (CIP); and (g) firing the resulting compact in an atmosphere of air, thereby obtaining the composition.

Abstract: A cutting tool coated with diamond in which diamond is coated as a film on a substrate having a step 15 to 500 &mgr;m in height in the vicinity of a cutting edge on the rake surface and/or the flank surface. Only the diamond film in the vicinity of the cutting edge can be polished first, without polishing the film of the diamond formed centrally of the rake surface and/or the flank surface. This enables the maximum effect (sharpening of the cutting edge and prevention of welding formation at cutting edge) to be realized with the necessary minimum polishing (with a decreased polishing removal), without setting special conditions and which is suited as a finishing tool.

Abstract: An translucent polycrystalline ceramic capable of transmitting a visible light and excellent in strength, hardness, abrasion resistance, light transmittance, transparency and high-temperature characteristics and usable as a material, for instance, for cutting tools, outer tubes for high pressure sodium lamps and high temperature furnace window plates. The translucent polycrystalline ceramic has at least one characteristic features that (1) a mean particle size of crystal particles formed inside the ceramic is not larger than 1.0 &mgr;m, (2) a mean aspect ratio thereof is from 1.0 to 1.5, (3) a density thereof is substantially a theoretical density, (4) a light transmittance through its thickness of 1 mm is at least 50%, (5) a mean facet length of crystal particles formed inside the ceramic is not longer than a maximum wave length of the light. One of the embodiments is a translucent polycrystalline Al2O3 ceramic containing 0.02-2.

Abstract: A temperature sensor including a thermosensitive element and a ceramic body having a hollow section which surrounds the thermosensitive element airtightly. The thermosensitive element is formed on a heat-sensing surface side of the ceramic body having the hollow section. The hollow section is formed at a position which is shifted to the heat-sensing surface side with respect to the center of the temperature sensor. The ceramic body includes a heat-sensing surface side ceramic layer (1) having the thermosensitive element (4) disposed thereon, a spacer ceramic layer (3) having an aperture, and a substrate ceramic layer (2) serving as a substrate.

Abstract: A diamond-coated hard metal member comprising a WC-based hard metal substrate having a roughened surface formed by electrolytic etching and a diamond coat layer coating the roughened surface with an interlayer provided interposed therebetween. The interlayer coats the substrate, and is a W layer having a roughened surface corresponding to the roughened surface of the substrate. The unetched substrate comprises disperse phases dispersed therein in an amount of from 2 to 5 mol-%, and has disperse phases having an average longest diameter of from not less than 0.5 &mgr;m to less than 2 &mgr;m on the surface thereof in a density of from not less than 0.1/&mgr;m2 to not more than 0.2/&mgr;m2.

Abstract: Alumina-based ceramics are thermally stable because of their high melting point and excellent materials in wear resistant properties and chemical stability. However, they contradictly have such a problem that fracture toughness is low, and its improvement is desired. The present invention provides such sintered alumina-based ceramics and their production process that have rendered to grow alumina grains anisotropically and fracture simultaneously attain high flexural strength and fracture toughness by sintering the formed mixture comprising Al2O3, 0.05-2.5 mol % of VA metal oxide and 0.01-4 mol % SiO2, relative to Al2O3, respectively.

Abstract: Alumina-based ceramics are thermally stable because of their high melting point and excellent materials in wear resistant properties and chemical stability. However, they contradictly have such a problem that fracture toughness is low, and its improvement is desired. The present invention provides such sintered alumina-based ceramics and their production process that have rendered to grow alumina grains anisotropically and can simultaneously attain high flexural strength and fracture toughness by sintering the formed mixture comprising Al.sub.2 O.sub.3, 0.05-2.5 mol % of VA metal oxide and 0.01-4 mol % SiO.sub.2, relative to Al.sub.2 O.sub.3, respectively.

Abstract: The present invention provides a method of manufacturing a superhard article with diamond coat having an excellent resistance against breakaway or peeling off of its coat, in particular, a cutting tool. A carbide base material formed to a desired shape containing tungsten carbide (WC) as a main component is soaked in a solution of alkali chloride and undergoes electrolytic etching on the surface of the base material at a maximum removal speed of 0.2 to 1.5 .mu.m/min for 3 to 30 minutes and, after the surface of the base material is washed, a diamond coat is developed on the surface of the base material by vapor deposition.

Abstract: A CVD method of forming a diamond coated article is disclosed, which consists essentially of a substrate and a plurality of polycrystalline diamond film layers accumulatively coated thereon in a total thickness of at least 20 .mu.m, wherein each of the polycrystalline diamond film layers (i) has a thickness of 6 to 13 .mu.m, (ii) has an average crystallite size in the surface direction thereof of 3 to 7 .mu.m, (iii) has (111) oriented diamond crystallites exposed on the surface thereof, and (iv) satisfies the relationship: I(N)/I(D)<0.2, wherein I(D) represents an intensity of diamond Raman peak in counts/sec appearing around 1333 cm.sup.-1 and I(N) represents a maximum intensity among non-diamond Raman peaks appearing between 1200 cm.sup.-1 and 1600 cm.sup.-1.

Abstract: Diamond coating member is produced by a method comprising a first coating step in which the first diamond coating layer is closely formed on fine irregularity parts of a substrate having fine irregularities substantially without void left between them and the fine irregularities is engaged with the above first layer to coat the above substrate, and a second coating step in which the surface of the first coating layer is coated with a second diamond coating layer comprising diamond having a higher wear resistance than that of the first coating layer. The diamond coating member is excellent in adhesion between the diamond coating layer and the substrate and has high durability without having the diamond coating layer scaled off by mechanical shocks. It has high wear resistance and enables mass production without fluctuation in product quality.

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: Ceramic-based substrate for coating, e.g., diamond has a basic irregularities surface having a surface roughness Rz of 2 to 20 .mu.m, with Rz at angle regions of 40% or more of that for other than the angle regions. The basic irregularities surface has micro-sized irregularities on an order of crystal grains constituting the uppermost surface (0.5 to 10 .mu.m), forming dual irregularities surface structure. Coating layer engages with surface irregularities to secure firm adhesion at the cutting edge. WC-based cemented carbide is used as substrate and N-containing surface layer is formed by heat treatment to form the surface irregularities.

Abstract: A diamond coated article is disclosed which consists essentially of a substrate and a plurality of polycrystalline diamond film layers accumulatively coated thereon in a total thickness of at least 20 .mu.m, wherein each of the polycrystalline diamond film layers (i) has a thickness of 6 to 13 .mu.m, (ii) has an average crystallite size in the surface direction thereof of 3 to 7 .mu.m, (iii) has (111) oriented diamond crystallites exposed on the surface thereof, and (iv) satisfies the relationship: I(N)I(D)<0.2, wherein I(D) represents an intensity of diamond Raman peak in counts/sec appearing around 1333 cm.sup.-1 and I(N) represents a maximum intensity among non-diamond Raman peaks appearing between 1200 cm.sup.-1 and 1600 cm.sup.-1.

Abstract: Ceramic-based substrate for coating, e.g., diamond has a basic irregularities surface having a surface roughness Rz of 2 to 20 .mu.m, with Rz at angle regions of 40% or more of that for other than the angle regions. The basic irregularities surface has micro-sized irregularities on an order of crystal grains constituting the uppermost surface (0.5 to 10 .mu.m), forming dual irregularities surface structure. Coating layer engages with surface irregularities to secure firm adhesion at the cutting edge. WC-based cemented carbide is used as substrate and N-containing surface layer is formed by heat treatment to form the surface irregularities.

Abstract: Diamond coating member is produced by a method comprising a first coating step in which the first diamond coating layer is closely formed on fine irregularity parts of a substrate having fine irregularities substantially without void left between them and the fine irregularities is engaged with the above first layer to coat the above substrate, and a second coating step in which the surface of the first coating layer is coated with a second diamond coating layer comprising diamond having a higher wear resistance than that of the first coating layer. The diamond coating member is excellent in adhesion between the diamond coating layer and the substrate and has high durability without having the diamond coating layer scaled off by mechanical shocks. It has high wear resistance and enables mass production without fluctuation in product quality.

Abstract: Method for coating a substrate formed of a sintered silicon nitride based material with a film of diamond by a gas phase synthesis technique including a first step of applying a film having a thickness of 0.5 to 2.0 .mu.m at a temperature not higher than a temperature at which grain boundary components of the substrate volatilize, and a second step of synthesizing the film of diamond-and-the-like to a thickness of 5 to 100 .mu.at a temperature which expedites synthesis of the film of diamond.

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: A diamond-coated body is prepared by coating a diamond film on the surface of a sintered body by means of vapor phase synthesis, the sintered body being so prepared by subjecting a sintered body prepared from ceramics based on silicon nitride to heat treatment at the temperature of 1,400.degree. C. to 1,700.degree. C. as to give a crystalline intergranular phase. The resulting diamond-coated body has excellent adhesion between the diamond film and the substrate and it is appropriately employed for cutting tools and so on because, when applied to the cutting tools, they can be used for cutting for a long period of time.

Abstract: The present invention is directed to a diamond-coated body having a diamond coat film formed on the surface of a ceramic substrate containing acicular grains having a thickness of 0.2 .mu.m to 1 .mu.m and an aspect ratio of 2 or higher at the two-dimensional density of 30% or higher, and the diamond coat film has good adhesion to the ceramic substrate. Thus the diamond-coated body is superior in durability and can be appropriately utilized as cutting tools and so on.

Abstract: An aluminum oxide-based sintered object having excellent abrasion resistance includes .alpha.-aluminum oxide, a silicon compound and a tungsten compound, wherein the silicon compound and the tungsten compound are present in amounts based on starting amounts of SiC and W metal of from 5 to 40 mole % and from 0.5 to 25 mole %, respectively, based on the sintered object overall, with a W/SiC molar ratio of 4 or less, and in which particles of at least one of tungsten carbide and tungsten silicide having an average particle diameter of 0.5 .mu.m or less are dispersed as a crystalline phase.