Abstract: Provided is a hydrodynamic gas bearing structure which can prevent occurrence of whirl not only in high-speed rotation but also in low-speed rotation, reduces such frequency that a floating rotational frequency in starting or stoppage of rotation increases, and is capable of shifting the floating rotational frequency to a low rotational frequency side. The hydrodynamic gas bearing structure comprises a shaft body (1) and a bearing body (2). A groove (11) is formed on the outer peripheral surface of the shaft body (1). The groove (11) consists of at least two concave parts, whose depths substantially differ from each other, which are formed serially in the circumferential direction, and has a circumferentially asymmetrical shape in a cross section perpendicular to the axis.

Abstract: A cross-sectional shape of a shaft body 1 perpendicular to its axis O has a shape defined by a closed curve having a plurality of maximal points M.sub.1, M.sub.2 and M.sub.3 whose distances from the axis are maximized about the axis O and a plurality of minimal points N.sub.1, N.sub.2 and N.sub.3 whose distances from the axis are minimized. This cross-sectional shape has a groove forming region provided with one groove 1b.sub.1 at least between the maximal points M.sub.1 and M.sub.2. When a bearing body 2 rotates on a CCW side with respect to the shaft body 1, the groove 1b.sub.1 is so arranged that an outer peripheral length a.sub.1 in the forward rotational direction exceeds an outer peripheral length b.sub.1 in the reverse rotational direction.

Abstract: A joint body in which aluminum and silicon nitride are strongly joined with each other is provided at a low cost, thereby providing a lightweight part which is excellent in sliding property as a mechanical part of an internal combustion engine of an automobile or the like. The joint body includes a base material which is mainly composed of aluminum, and a member consisting of a silicon nitride sintered body which is substantially directly joined to the base material. A powdery or bulky base material (2) mainly composed of aluminum, and a member (1) consisting of a silicon nitride sintered body are charged in a mold and heated under pressurization, thereby joining the same with each other.

Abstract: The present invention is intended to provide a sliding member that can prevent abnormal wear and partial wear of the mating metal sliding component even when an oil contaminated with exhaust gas components is used.A ceramic sliding component is manufactured as followed. A silicon nitride-based material for the sliding face member is joined to a metal body having a higher thermal expansion coefficient than the sliding face member. A crowned portion is formed on the sliding face of the sliding face member in such a way that the difference between the amounts of crowning (da, db) at two arbitrary points axially symmetric with respect to the center line of the crowned portion is 10% or more and 50% or less of the average of the crowning amounts at the two points.

Abstract: This invention aims at providing a sliding component having a crowning shape formed by applying surface quenching treatment to a portion made of a steel, and a production method thereof. The shape and the quantity of crowning can be controlled by heat-treatment or machining after the surface quenching. The sliding component may be made of a steel alone, or may be formed in such a manner that at least one portion of members forming the crowning-shaped sliding face by the surface quenching is joined or fitted to a sliding component main body made of the steel, and its material is a ceramic.

Abstract: To provide sliding components each comprising a base metal and, joined thereto, a sliding face member having a sliding face of crowning profile, in particular, sliding components such as valve train parts, a cam follower and a rocker arm of an automobile engine. A sliding component having a structure comprising (1) a ceramic forming a sliding face and (2) a base metal joined together, in which the extent of crowning of the sliding face is at least 0.1 to 0.4% of the maximum length of the junction face of the ceramic. The ceramic has a four-point flexural strength of at least 50 Kg/mm as measured in accordance with the Japanese Industrial Standard R1601. The base metal is mainly steel at least the surface of which has preferably a martensite texture and has a hardness of higher than 45 in terms of H.sub.RC. The structure may have an intermediate layer of a metal or cermet.

Abstract: The invention reduces the time required for nitriding in the process of reaction sintering for production of a sintered body of silicon nitride, thereby improving productivity, and provides a sintered body of silicon nitride having sufficient compactness and high strength which can be produced by reaction sintering. The sintered body is Si.sub.3 N.sub.4 having an unpaired electron density of 10.sup.15 /cm.sup.3 to 10.sup.21 /cm.sup.3. The sintered body is produced through reaction sintering by using a Si powder having an unpaired electron density of 10.sup.15 -10.sup.20 /cm.sup.3, which is obtained by annealing a commercially available Si powder at temperatures of 300.degree. to 800.degree. C. in other than nitrogen atmosphere for 3-5 hours.

Abstract: A ceramics porous body having high porosity as well as high strength is especially suitable for use as a filter for removing foreign matter from a fluid or as a catalytic carrier. The porous body has a porosity of at least 30% and comprises columnar ceramic grains having an aspect ratio of at least 3. In particular, the porous body comprises Si.sub.3 N.sub.4 grains, of which at least 60% are hexagonal columnar .beta.-Si.sub.3 N.sub.4 grains. The porous body further comprises at least one compound of a rare earth element in an amount of at least 1 volume % and not more than 20 volume % in terms of an oxide of the rare earth element, and optionally at least one compound of elements of the groups IIa and IIIb of the periodic table and transition metal elements in an amount of not more than 5 volume % in terms of an oxide of each element.

Abstract: A ceramics porous body having a high porosity as well as high strength is especially suitable for use as a filter for removing foreign matter from a fluid or as a catalytic carrier. The porous body has a porosity of at least 30% and comprises columnar ceramic grains having an aspect ratio of at least 3. In particular, the porous body comprises Si.sub.3 N.sub.4 grains, of which at least 60% are hexagonal columnar beta-Si.sub.3 N.sub.4 grains. The porous body further comprises at least one compound of a rare earth element in an amount of at least 1 vol.% and not more than 20 vol.% of an oxide of the rare earth element, and optionally at least one compound of elements of the groups IIa and IIIb of the periodic table and transition metal elements in an amount of not more than 5 vol.% of an oxide of each element. A compact of mixed powder obtained by adding the compound powder of the rare earth element to silicon nitride powder is heat treated in a nitrogen atmosphere at a temperature of at least 1500.degree. C.

Abstract: A vacuum vessel is provided in which the majority of a vessel wall including an annular wall portion (1) and a plate-wall portion (2) is formed of ceramic material such as silicon nitride, for example. To bond the plural wall members together, bonding faces having a surface flatness of not more than 1 .mu.m are prepared thereon, and then a ceramic powder bonding substance with an average particle diameter of not more than 1 .mu.m is interposed between adjacent bonding faces and subjected to heating. Because the generation of gas, such as hydrogen, from the wall of the ceramic vessel is reduced, extremely high vacuum can be generated and maintained in the interior of the vacuum vessel. Also, because the wall of the vacuum vessel has a high permeability with respect to a magnetic field and an electric field, the vacuum vessel can be used as a vessel in a particle accelerator that allows the high precision control of charged particles therein by means of an electromagnetic field.

Abstract: An aluminum nitride sintered body is mainly composed of aluminum nitride, contains 0.01 to 1.0 percent by weight of a rare earth element and 0.001 to 0.5 percent by weight of oxygen, and has thermal conductivity of at least 180 W/mK. According to a method of manufacturing such an aluminum nitride sintered body, aluminum nitride powder (201) is first prepared. At least one compound (203) containing a rare earth element is added to the aluminum nitride powder (201) to contain 0.01 to 1.0 percent by weight, in rare earth element conversion, of the compound, to be homogeneously mixed with each other. A formed body obtained by forming such mixed powder is sintered in a non-oxidizing atmosphere containing nitrogen at a temperature of 1500 to 2200.degree. C.

Abstract: A sintered body of aluminum nitride having a density of not smaller than 3.1 g/cm.sup.3, a coefficient of thermal conductivity of not smaller than 100 W/mk and preferably an average particle size of not larger than 5 .mu.m, which comprises aluminum nitride as a main component, 0.01 to 10.0% by weight of at least one oxide selected from oxides of the IIa and IIIa elements of the Periodic Table, 2.0% by weight or less of oxygen which is not contained in the oxide of the IIa and IIIa element and 1.0% by weight or less of at least one impurity metal which is not the IIa or IIIa element which has good thermal conductivity.

Abstract: An aluminum nitride sintered body mainly composed of aluminum nitride, contains 0.01 to 1.0 percent by weight of a rare earth element and 0.001 to 0.5 percent by weight of oxygen. Such a body has a thermal conductivity of at least 180 W/mK. For manufacturing such an aluminum nitride sintered body, aluminum nitride powder (201) is first prepared. At least one compound (203) containing a rare earth element is added to the aluminum nitride powder (201) to contain 0.01 to 1.0 percent by weight, in rare earth element conversion, of the compound. The ingredients are homogeneously mixed with each other. A green body is formed of the mixed powder and sintered at a temperature of 1500.degree. to 2200.degree. C. in a non-oxidizing atmosphere containing nitrogen.

Abstract: A connection structure between lead frames and a base plate of aluminum nitride, to be applied as a connection structure between components of a semiconductor apparatus, has a base plate made of a sintered body of aluminum nitride on which a semiconductor device is to be mounted. The lead frames are made of iron alloy containing nickel in 29 wt. % and cobalt in 17 wt. %. A silver solder is used for joining the base plate and the lead frames. A surface of the lead frame to be joined to the base plate is clad with a stress relief layer of oxygen-free copper of a high plastic deformability to relieve, by its plastic deformation, a thermal stress caused by a difference between a thermal expansion coefficient of the aluminum nitride base plate and that of the lead frame in a cooling process at the time of soldering. Preferably, only a portion of each lead frame to be joined to the base plate comprises an inner layer of an iron alloy containing 29 wt. % of nickel and 17 wt.

Abstract: A member for a semiconductor apparatus for carrying or holding a semiconductor device, obtained by joining an aluminum nitride substrate and a radiating substrate, comprises an insulating member formed by an aluminum nitride sintered body to be provided thereon with the semiconductor device, a radiating member to be joined to the insulating member, which radiating member is mainly formed of a copper-tungsten alloy or a copper-molybdenum alloy, a stress relieving member interposed between the insulating member and the radiating member and a silver solder member for joining the insulating member, the stress relieving member and the radiating member with each other.

Abstract: Herein disclosed is a transverse resonance measurement device for measuring the Young's modulus and/or internal friction of the plate specimen of a material over a wide temperature range even if the material is nonconductive, e.g., ceramics, wood or plastics. Platinum paste is applied to one side of a plate specimen to be measured, and is baked into a platinum electrode.

Abstract: An electrically-conductive sintered compact of silicon nitride which is machinable by electrical discharge machining and a process to produce the same. TiN and/or TiC powder is added to a powder of silicon nitride in an amount 15-40% by volume to act as a conductivity-supplying agent while 0.01-3.0% by volume MgO and/or Al.sub.2 O.sub.3 powder is added as a sintering assistant. The mixed powders are then preformed in a desired shape and sintered in a nonoxidizing environment at 1,600.degree. C.-2,000.degree. C. to obtain a compact of silicon-nitride machinable by electrical discharge machining due to its electrical conductivity being at least 1 S.multidot.cm.sup.-1.