Abstract: A silicon nitride powder with which a highly reliable silicon nitride with high strength and small strength and dimensional variances is obtainable is disclosed. By setting the amount of their surface acidic groups per B.E.T. surface area to not less than 0.2 .mu.eq/m.sup.2, their dispersibility in a mixing solvent is drastically improved. By using them, moldings with high density and homogeneity can be obtained, thereby enabling in turn a highly reliable sintered product of silicon nitride with high strength and small strength and dimensional variances to be easily manufactured. Besides, in the silicon nitride powder, the proportion of the silicon [Si*] belonging to SiO.sub.2, of the surface silicon [Si], which is determined by the X-ray photoelectron spectroscopy (XPS), should be not less than 0.07 in its atomic ratio [Si*/Si] and that to silicon of the surface carbon [C] which is determined by XPS in the same way should be not more than 0.20 in its atomic ratio [C/Si].

Abstract: Provided is an apparatus for producing a silicon nitride sintering body made of a furnace including a heater source. The furnace includes a furnace core chamber defined by at least one partition inside the furnace to prevent an atmosphere containing more than about 30 ppm of carbon monoxide from contacting said silicon nitride sintered body. At least an inner surface of the partition is made of a carbon-free heat-proof material which prevents formation of carbon monoxide gas in an atmosphere in contact with the silicon nitride sintered body during sintering. The furnace also includes a gas supply pipe for supplying an N.sub.2 gas or an inactive gas including an N.sub.2 gas into the furnace core. Also provided is a sintering case made of a vessel defining a sintering atmosphere. The vessel has an opening for loading an object to be sintered into the vessel.

Abstract: An aluminum nitride sintered body comprising aluminum nitride crystals belonging to a Wurtzite hexagonal crystal system wherein the 3 axes a, b and c of the unit lattice of the crystal are defined such that the ratio b/a of the lengths of the axes b and a is 1,000 near the center of the crystal grain and lies within the range 0.997-1.003 in the vicinity of the grain boundary phase. Aluminum nitride sintered body is produced by sintering a molded body of a raw material powder having aluminum and nitrogen as its principal components at a temperature of 1700.degree.-1900.degree. C. in a non-oxidizing atmosphere having a partial pressure of carbon monoxide or carbon of not more than 200 ppm and then cooling the sintered body to 1500.degree. C. or a lower temperature at a rate of 5.degree. C./min or less. The aluminum nitride sintered body has a greatly improved thermal conductivity and, therefore, is suitable for heat slingers, substrates or the like for semiconductor devices.

Abstract: A zirconia vane used in a rotary compressor, the zirconia vane being formed of a partially stabilized zirconia sintered body containing 92 through 98 molar percent of ZrO.sub.2 and being stabilized with Y.sub.2 O.sub.3, zirconia crystals constituting the zirconia sintered body having a mean grain diameter of 0.1 to 0.6 .mu.m and a maximum grain diameter of not greater than 2 .mu.m, the zirconia sintered body having a mean three-point flexural strength of not less than 120 kg/mm.sup.2 measured in conformity with JIS R1601, a surface of the zirconia sintered body in contact with a rotor of the rotary compressor having a first surface roughness in a direction of rotations of the rotor, specified by a ten-point mean roughness Rz, of not greater than 1 .mu.m and a second surface roughness in a direction perpendicular to the direction of rotation of the rotor, specified by the ten-point mean roughness Rz, of not greater than 0.6 .mu.m.

Abstract: A silicon nitride sintered body characterized by comprising crystal grains having a linear density of 60 to 120 per 50 .mu.m length as measured in an arbitrary two-dimensional section of the sintered body. The silicon nitride sintered body has a shock compressive elasticity limit (Hugoniot-elastic limit) of 15 GPa or more and is substantially composed of crystal phases of .alpha.-silicon nitride and .beta.'-sialon. The percentages of the .alpha.-silicon nitride and .beta.'-sialon are not more than 30% and not less than 70%, respectively. The silicon nitride sintered body is particularly excellent in mechanical strengths at room temperature as well as in productivity and cost efficiency and is useful for applications as the material of parts where a particularly high impact strength is required, such as a valve train mechanism for automobile parts.

Abstract: An aluminum nitride sintered body comprising aluminum nitride crystals belonging to a Wurtzite hexagonal crystal system wherein the 3 axes a, b and c of the unit lattice of the crystal are defined such that the ratio b/a of the lengths of the axes b and a is 1.000 near the center of the crystal grain and lies within the range 0.997-1.003 in the vicinity of the grain boundary phase. Aluminum nitride sintered body is produced by sintering a molded body of a raw material powder having aluminum and nitrogen as its principal components at a temperature of 1700.degree.-1900.degree. C. in a non-oxidizing atmosphere having a partial pressure of carbon monoxide or carbon of not more than 200 ppm and then cooling the sintered body to 1500.degree. C. or a lower temperature at a rate of 5.degree. C./min or less. The aluminum nitride sintered body has a greatly improved thermal conductivity and, therefore, is suitable for heat slingers, substrates or the like for semiconductor devices.

Abstract: The invention relates to material silicon nitride powder used for production of silicon nitride ceramics products. Provided herein is a material powder which can offer a compact having a homogeneous packing structure of the powder with good reproducibility and also to provide a method for producing the same. According to the method, a silicon nitride powder is heat treated in two-stage processing, one stage in an inert gas or reducing atmosphere at 100.degree. C.-1000.degree. C. for 5-600 min., and another stage in an oxidizing atmosphere at 300.degree. C.-1200.degree. C. for 5-600 min. As a result of this treatment, a silicon nitride powder is obtained in which its powder particles are crystalline in their interior and are coated with an amorphous layer having a 1-10 nm surface thickness and composed mainly of Si, N, O, and H, an atomic number ratio of oxygen to nitrogen (O/N) of the surface layer being within a range of 0.1-2.0.

Abstract: An aluminum nitride sintered body has a high breakdown voltage for serving as a substrate material particularly suited to highly integrated circuits. The aluminum nitride sintered body contains titanium, which is included as a solid solute in the aluminum nitride crystal lattice in a weight ratio of at least 50 ppm and not more than 1000 ppm. The unpaired electron concentration in the sintered body as determined from an absorption spectrum of electron spin resonance is at least 1.times.10.sup.13 /g. At least 0.1 percent by weight and not more than 5.0 percent by weight, in terms of TiO.sub.2, of an oxy-nitride of titanium and aluminum exists in the aluminum nitride sintered body. The aluminum nitride sintered body has a breakdown voltage of 20 kV/mm. The sintered body is obtained by nitriding aluminum nitride raw material powder in a nitrogen atmosphere at a temperature of 800 to 1400.degree. C., adding an oxy-nitride of titanium thereto with a sintering assistant, and sintering the mixture.

Abstract: Silicon nitride sintered bodies consisting of prismatic crystal grains of Si.sub.3 N.sub.4 and/or sialon, equi-axed crystal grains of Si.sub.3 N.sub.4 and/or sialon, a grain boundary phase existing among the prismatic and equi-axed crystal grains and dispersed particles in the grain boundary phase, in which the prismatic crystal grains have an average grain size of 0.3 .mu.m or less in minor axis and an average grain size of 5 .mu.m or less in major axis, the equi-axed crystal grains have an average grain size of 0.5 .mu.m or less and the dispersed particles have an average size of 0.1 .mu.m or less, the volume of the dispersed particles being 0.05% by volume or more based on the total volume of the rest of the sintered body. The silicon nitride sintered bodies have a strength sufficient for use as structural materials of machine parts or members, with a minimized scattering of the strength as well as high reliability, superior productivity and advantageous production cost.

Abstract: A silicon nitride sintered body comprising 3.5% by weight or less of aluminum, 3.5% by weight or less of oxygen and the balance of silicon nitride; and a silicon nitride sintered body comprising 90% by weight or more of silicon nitride, 3.5% by weight or less of aluminum, 3.5% by weight or less of oxygen and from 0.01 to 10% by weight of at least one metallic element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Fin, Fe, Co, Ni, Nd, and Ho. These sintered bodies have a density of 3.15 g/cm.sup.3 or more and a thermal conductivity of 40 W/mK or more.

Abstract: An aluminum nitride powder having a surface layer containing an oxynitride characterized in that the surface layer of the aluminum nitride particle contains an aluminum oxynitride which has an oxygen content of 5 to 75 mol % in terms of Al.sub.2 O.sub.3 /(Al.sub.2 O.sub.3 +AlN). The surface layer of the aluminum nitride powder may contain, besides the aluminum oxynitride, at least one other oxynitride selected from among oxynitrides of Mg, Ca, Ba, Ti, V, Cr, Co, Ni, Cu, Ga, Ge, Zr, Nb, Mo, Ru, Hf, Ta, W, Li, B, Si, Y, Sc and rare metal elements and the aluminum oxynitride and at least one other oxynitride have a total oxygen content in the range of 10 to 75 mol % in terms of (3.times.oxygen amount)/(3.times.oxygen amount+nitrogen amount).

Abstract: The invention provides a method of producing sintered silicon nitrides having such strength characteristics as are sufficient to insure satisfactory reliability of the sintered silicon nitride for use in applications such as automotive engine parts and bearings. The method comprises preparing a sintering aid by blending yttrium oxide, spinel, and aluminum oxide and/or aluminum nitride together in such proportions in terms of molar ratios of metal elements that Y/(Al+Mg) is 0.23 to 0.85 and Al/Mg is 2.1 to 5.2, mixing 5.0 to 13.0% by weight of the sintering aid with 87.0 to 95.0% by weight of a silicon nitride powder having an .alpha. crystallinity of not less than 60%, and, after the resulting powder mixture is molded into shape, sintering the molded piece at temperatures of 1400 to 1650.degree. C. in a nitrogen gas atmosphere or in an inert gas atmosphere containing nitrogen gas.

Abstract: An aluminum nitride sintered body has a high breakdown voltage for serving as a substrate material particularly suited to highly integrated circuits. The aluminum nitride sintered body contains titanium, which is included as a solid solute in the aluminum nitride crystal lattice in a weight ratio of at least 50 ppm and not more than 1000 ppm. The unpaired electron concentration in the sintered body as determined from an absorption spectrum of electron spin resonance is at least 1.times.10.sup.13 /g. At least 0.1 percent by weight and not more than 5.0 percent by weight, in terms of TiO.sub.2, of an oxy-nitride of titanium and aluminum exists in the aluminum nitride sintered body. The aluminum nitride sintered body has a breakdown voltage of 20 kV/mm. The sintered body is obtained by nitriding aluminum nitride raw material powder in a nitrogen atmosphere at a temperature of 800.degree. to 1400.degree. C., adding an oxy-nitride of titanium thereto with a sintering assistant, and sintering the mixture.

Abstract: Disclosed herein are a method for molding a high density and homogeneous silicon nitride ceramics within a short time and an apparatus used for the method. A gel-like slurry mixture which is a mixture of ceramic powders consisting mainly of Si.sub.3 N.sub.4 and a liquid and has a powder content of from 45 vol % to 60 vol % is fluidized by imparting thereto a strain by vibration, and the mixture under the fluidized state is filled into, and molded by, a mold. Preferably, the entire part or a part of the mold is made of a liquid permeable material. The vibration preferably has an acceleration of from 0.1 G to 150 G and an amplitude of 1 .mu.m to 1 cm. Furthermore, the viscosity of the slurry filled into the mold is preferably from 2,000 to 20,000 cps.

Abstract: A silicon nitride composite sintered which comprises crystal grains of silicon nitride and/or sialon having an average minor axis length of 0.05 to 3 .mu.m and an aspect ratio of 10 or less and foreign particles dispersed in the crystal grains and/or the grain boundary phase, said particles having a thermal expansion coefficient of 5.times.10.sup.-6 /.degree.C. or more and an average particle size of 1 to 500 nm. The sintered body is produced by wet mixing silicon nitride powder, at least two sintering aids selected from among Y.sub.2 O.sub.3, Al.sub.2 O.sub.3, AlN and MgO and at least one compound selected from among the oxides, nitrides, carbides and silicides of the elements, excluding Si and C, of the groups IIa, IIIa, IVa, Va, VIa, IIb, IIIb and IVb of the Periodic Table to form a molding; and heat treating under the specified conditions.

Abstract: The present invention relates to improvement of a quadrupole electrode for use in a mass spectrometer or the like, in which two pairs of electrode rods 1, 2, 3 and 4 formed in such a manner that the section of the opposed face of each rod is hyperbolic or circular, and each electrode rod is made of a ceramic and the surface of the electrode is coated with a coating layer 5 of a conductive metal. Further, the present invention relates to a production process, characterized by incorporating such four electrodes at predetermined intervals. Since the electrodes are mainly made of a ceramic which is easily formable with a high dimensional accuracy, the adjustment of the positional relationship between the electrodes during assembling can be made without much effort, which enables a quadrupole electrode having a high performance to be provided with a good reproducibility at a low cost.

Abstract: The preset invention provides a ceramic adjusting shim capable of minimizing the abrasion of parts contacting the adjusting shim, for example, a cam and a tappet. The ceramic adjusting shim is produced from a ceramic material and has a surface roughness of 0.05 to 0.2 .mu.m in ten-point average roughness Rz.

Abstract: A metallized layer is to be formed on a surface of an aluminum nitride base material, which may be a sintered body or a nonsintered compact. A mixture is prepared from an oxide component consisting of at least one of Al.sub.2 O.sub.3, SiO.sub.2, CaO, and Y.sub.2 O.sub.3, an iron family component consisting of at least one of Fe, Co and Ni and high melting temperature metal consisting of W and Mo. The content of each component is within a specified range. A paste is prepared by adding an organic binder substance to the mixture. The paste is applied to the surface of the base material and heated under specified conditions to form a metallized layer having a high adhesive peel strength on the surface of the base material.

Abstract: A silicon sintered body comprising a matrix phase consisting of silicon nitride and a grain boundary phase in which the silicon nitride consists of 66 to 99% by volume of .beta.-Si.sub.3 N.sub.4 and/or .beta.'-sialon with the balance being .alpha.-Si.sub.3 N.sub.4 and/or .alpha.'-sialon, the .beta.-Si.sub.3 N.sub.4 and/or .beta.'-sialon consisting of hexagonal rod-like grains having a diameter of 500 nm or less in the minor axis and an aspect ratio 5 to 25, the .alpha.-Si.sub.3 N.sub.4 and/or .alpha.'-sialon consisting of equi-axed grains having an average diameter of 300 nm or less, and titanium compounds are contained within the grains of the matrix phase and in the grain boundary phase. The sintered body is produced by mixing (1) 100 parts by weight of .alpha.-Si.sub.3 N.sub.4 powder, (2) 0.

Abstract: The present invention provides an improved adjusting shim used in a valve train for an internal combustion engine for an automobile. The adjusting shim produced from a base material consisting of a ceramic material containing 80 to 98 wt. % of silicon nitride and/or sialon and has a porosity of not more than 3%, a bending strength of not less than 1.0 GPa and an impact compressive elastic limit (Hugoniot elastic limit) of not less than 15 GPa, wherein the base material is provided on the surface thereof which contacts a cam with a ceramic surface layer having a composition different from that of the base material and a hardness lower than that of the base material. The adjusting shim of the present invention enables a power loss of a valve train to be minimized; the abrasion resistance thereof to be improved; and the fuel economy, the performance and durability of an internal combustion engine to be improved.