Toyo Soda Manufacturing Co., Ltd.

Tosoh Corporation

Takaaki Tsukidate

Kiyoshi Kasai

Koji Tsukuma

Toshihiko Arakawa

Kuniyoshi Ueda

Naomichi Sakai

Yoshitaka Kubota

Junji Arika

Hiroya Nagata

Tomoyuki Oikawa

Hiroshi Yamamura

Kenji Uchino

Tadaaki Mori

Kohji Tsukuma

Shinji Nagata

Yoshihiro Matsumoto

Hiroshi Asakura

An actuator of the present invention is composed of a monomorph-type piezoelectric ceramic. The monomorph-type piezoelectric ceramic is a BaTiO.sub.3 -based ceramic, a PZT based ceramic having Nb, Sb, La, Mn, Nd and Bi, BaTiO.sub.3 --SrTiO.sub.3 -based ceramic containing SrTiO.sub.3 by 20 to 35 mole %, K(Nb, Ta)O.sub.3 -based ceramic, or a ceramic represented by a general formula: [Pb, (A.sub.1/2 B.sub.1/2)](Zr.sub.1-n, Cn)O.sub.3 where A is a monovalent element such as Li, Na, K, Rb, Cs or the like, B is a trivalent element such as Bi, La, Y, Sb, Ga or the like, A and B being both replaceable solid-meltable elements for Pb, C is an element such as Ti, Sn or the like that is a replaceable solid-meltable element for Zr, and n is from 0 to 0.8.

Actuator

A zirconia type sintered body consisting essentially of 50 to 98% by weight of zirconia (ZrO.sub.2) containing 1.5 to 5 mole % of yttria (Y.sub.2 O.sub.3) and 50 to 2% by weight of alumina (Al.sub.2 O.sub.3), spinal (MgAl.sub.2 O.sub.4) or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2), and having a three-point bending strength of at least 1700 MPa is provided. This sintered body is prepared by a process wherein a powdery composition consisting essentially of 50 to 98% by weight of (a1) a powder of zirconia containing 1.5 to 5 mole % of yttria or (a2) a mixture comprising 1.5 to 5 mole % of yttria powder and 95 to 98.5 mole % of a zirconia powder and 2 to 50% by weight of (b) a powder of an alumina type oxide selected from alumina, and alumina-magnesia type oxide, an alumina-silica type oxide, a mixture of alumina and magnesia and a mixture of alumina and silica is subjected to a hot isotactic pressing treatment under a pressure of at least 50 MPa at temperature of 1300.degree. C. to 1700.degree. C. or a monoaxially compression-sintering treatment under a pressure of at least 20 MPa at a temperature of 1400.degree. C. to 1700.degree. C.

High-strength zirconia type sintered body and process for preparation

Disclosed is a process for the preparation of high .alpha.-type silicon nitride powder, wherein a nitrogen-containing silane compound and/or amorphous silicon nitride is crystallized to form crystalline silicon nitride. In this process, crystalline silicon nitride having a particle size not larger than 0.05 .mu.m is incorporated in an amount of at least 0.1% by weight into the nitrogen-containing silane compound and/or amorphous silicon nitride, the mixture is formed into a power or molded body having a powder bulk density of at least 0.1 g/cm.sup.3 as silicon, and the powder or molded body is heated to 1,350.degree. to 1,700.degree. C. while controlling the temperature-elevating rate to at least 15.degree. C./min throughout the temperature range of from 1,200.degree. to 1,350.degree. C. The resulting high .alpha.-type silicon nitride is composed of a fine granular crystal and the does not contain a needle crystal or columnar crystal.

Process for preparation of high .alpha.-type silicon nitride powder

A high .alpha.-type silicon nitride powder is prepared by thermally decomposing a mixture of a crystalline silicon nitride powder having an oxygen content of at least 1.0% by weight and a nitrogen-containing silane compound.

Process for preparation of high-type silicon nitride powder

A sintered product of zirconia comprising ZrO.sub.2 and CeO.sub.2 in a molar ratio of CeO.sub.2 /ZrO.sub.2 of 8/92-30/70, and consisting of a crystal phase which is a mixed phase consisting essentially of a tetragonal phase and a cubic phase, or which is a phase consisting essentially of a tetragonal phase, has a high mechanical strength and a high rupture toughness, and is applicable as the constituting materials of tools for machining and cutting, various kinds of dies and nozzles, parts for sliding and other industrial materials.

Sintered product of zirconia and method of producing the same

A high strength metal working tool such as cutting tools and dies made of a zirconia-base sintered material comprising 50 to 98 weight percent of zirconia (ZrO.sub.2) containing 1.5 to 5 mol percent of yttira (Y.sub.2 O.sub.3) and 50 to 2 weight percent of alumina (Al.sub.2 O.sub.3) and/or spinel (MgAl.sub.2 O.sub.4) and having a three point bending strength of not less than 1700 MPa.

High-strength metal working tool made of a zirconia-type sintered

A silicon nitride powder having an enhanced sintering activity is prepared by heating a mixture of a nitrogen-containing silane compound and a sintering aid in a non-oxidizing atmosphere.

Process for preparation of silicon nitride powder of good sintering

A zirconia type sintered body consisting essentially of 50 to 98% by weight of zirconia (ZrO.sub.2) containing 1.5 to 5 mole % of yttria (Y.sub.2 O.sub.3) and 50 to 2% by weight of alumina (Al.sub.2 O.sub.3), spinal (MgAl.sub.2 O.sub.4) or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2), and having a three-point bending strength of at least 1700 MPa is provided. This sintered body is prepared by a process wherein a powdery composition consisting essentially of 50 to 98% by weight of (a1) a powder of zirconia containing 1.5 to 5 mole % of yttria or (a2) a mixture comprising 1.5 to 5 mole % of a yttria powder and 95 to 98.5 mole % of a zirconia powder and 2 to 50% by weight of (b) a powder of an alumina type oxide selected from alumina, an alumina-magnesia type oxide, an alumina-silica type oxide, a mixture of alumina and magnesia and a mixture of alumina and silica is subjected to a hot isotactic pressing treatment under a pressure of at lesast 50 MPa at temperature of 1300.degree. C. to 1700.degree. C. or a monoazially compression-sintering treatment under a pressure of at least 20 MPa at a temperature of 1400.degree. C. to 1700.degree. C.

High-strength zirconia type sintered body

A method of manufacturing highly purified silicon nitride including the steps of preparing a nitrogen-containing silane selected from the group consisting of tetra-amide-monosilane and silicon imide, and heat-treating the prepared nitrogen-containing silane in the presence of ammonia in an inner atmosphere at a temperature above 400.degree. C. for a period of at least two hours to obtain silicon nitride, and cooling and collecting the silicon nitride thus formed. The step of preparing the nitrogen-containing silane comprises continuously reacting gaseous silicon tetra-chloride with gaseous ammonia in an inner atmosphere at a temperature of from -30.degree. to 70.degree. C. to produce the nitrogen-containing silane as a product and collecting the product. The resultant silicon nitride so produced has a chlorine content of less than 0.05 weight percent and a nitrogen content of over 38 weight percent.

Method of manufacturing high-purity silicon nitride powder

High-purity .alpha.-type silicon nitride comprised of a granular crystal having an .alpha.-phase content of at least 95%, a nitrogen content of at least 38% by weight and an average particle size of not larger than 3 .mu.m is provided. This high-purity .alpha.-type silicon nitride is prepared by heating a nitrogen-containing silane compound at a temperature of at least about 1,300.degree. C. in a heating furnace comprised of a material containing a metal having a melting point exceeding 1,600.degree. C. and capable of being bonded with oxygen at the heating temperature.

Process for preparing high-purity .alpha.-type silicon nitride

Titanium carbonitride of a high purity and in a fine powder form can be produced by maintaining a mixture of titanium halide and carbon at a temperature of from 700.degree. C. to 1,800.degree. C. in the presence of a reducing substance, such as aluminum or an aluminum-titanium alloy, in a nitrogen-containing gaseous atmosphere.

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Hino, Japan

Takaaki Tsukidate