Kureha Chemical Industry Company, Limited

Kureha Kagaku Kogyo Kabushiki Kaisha

Union Carbide Chemicals and Plastics Company, Inc.

Saburo Hori

Ryuichi Kurita

Toshikatsu Haga

Nobuhiro Watanabe

Cyril B Tellis

David Milks

Yukio Ito

Yoshio Ishii

A mullite-alumina composite sintered body composed of from 75 wt % to 85 wt % Al.sub.2 O.sub.3 balance SiO.sub.2, consisting of two crystalline phases, mullite and .alpha.-phase alumina, and being free from glass phase, wherein both of the average diameters of mullite grains and .alpha.-phase alumina grains are not more than 1.0 .mu.m, the content of grains having the longitudinal-length of not less than 2.5 .mu.m is 1% or less in the observation of a cross section of said sintered body, and the porosity of said sintered body is 1% or less. The sintered body of the present invention is produced by a process comprising the steps of preparing a starting powdery material composed of from 75 wt % to 85 wt % Al.sub.2 O.sub.3 balance SiO.sub.2 and containing amorphous phase from 65 wt % to 90 wt %, wherein each particle of said starting powdery material contains both Al.sub.2 O.sub.3 and SiO.sub.2, and sintering said starting powdery material at a temperature in the range from 1500.degree. C. to 1650.degree. C. The sintered body of the present invention has a high bending strength exceeding 500 MPa at room temperature.

Mullite-alumina composite sintered body and process for producing the

Improved operation of the ACR process is achieved by regulating the reactions within a small area in the combustion feedstock mixing zone, 'Scorch Zone', by the addition of steam or other fluid such as ethane at the point of feed injection.

Control ACR product yields by adjustment of severity variables

Proton conductive material comprising a compound of a monoclinic crystal structure which is in a reversibly reduced state from a compound of a similar monoclinic crystal structure represented by the general formula:

Proton conductive material and method of manufacturing thereof

A sintered body formed of corundum-alumina and rutile-titania which is prepared by adding an alkali metal to an alumina-titania composite powder produced by a vapor-phase reaction of AlCl.sub.3 and TiCl.sub.4, in the course of the oxidation reaction or by some treatment of the powder after the reaction; and sintering the powder at a temperature not lower than a minimum temperature at which a liquid phase is produced by a small amount of alkali metal oxide and titania and not higher than 1280.degree. C. has the characteristics which have never been obtained before. The sintered body of the present invention comprises alumina of corundum phase and titania of rutile phase, which contains alkali metal in an amount of 0.01 to 0.5 wt % and plate-shaped corundum particles whose cross sections having aspect ratios of 2.5 or more are observed to be 10 vol % or more by scanning electron micrography. This sintered body can have a high toughness by the compounding inexpensive oxides such as alumina and titania. The toughening mechanism of the present sintered body is due to a crack deflection effect by geometrically anisotropic particles which are dispersed in the material, and therefore the toughness is not expected to be deteriorated at high temperatures.

Tough corundum-rutile composite sintered body

Alumina-titania composite powder comprising spherical particles each of which contains about 30 to 80 wt % of .gamma.- phase or .delta.-phase alumina and about 70 to 20 wt % of titania comprising rutile-phase in the majority and is substantially free from X-phase (3Al.sub.2 O.sub.3 -TiO.sub.2) and aluminum titanate-phase. These alumina-titania composite powders are prepared by blowing a vapor mixture of AlCl.sub.3 and TiCl.sub.4 into a burning flame to effect oxidation, which is characterized in that a temperature of a mixing section, where a combustible gas, an oxidizing gas, AlCl.sub.3 gas, TiCl.sub.4 gas and a carrier gas are mixed and subjected to combustion, is kept at about 1450.degree. C. or higher and lower than a melting point of aluminum titanate; a temperature of an outlet portion of a reacting section connected to the mixing section is kept at about 800.degree. C. or higher; and an average total gas retention time in the mixing section and the reacting section are 20 to 500 msec.

Alumina-titania composite powder and process for preparing the same

Composite abrasive particles for use in magnetic abrasive polishing in which three phases of corundum-phase alumina, .alpha.-iron and iron-alumina spinel are detected by the powder X-ray diffractometry and which contains 48 wt % or more of iron and 11 wt % or more of aluminum. The composite abrasive particles are prepared by mixing starting materials of powders of aluminum and an iron oxide in such a ratio that three phases of corundum-phase alumina, .alpha.-iron and iron-alumina spinel may coexist and so that iron may be contained in an amount of 48 wt % or more and aluminum may be contained in an amount of 11 wt % or more, subjecting the materials to a solid-phase exothermic reaction, and breaking the resultant solid product.

Composite abrasive particles for magnetic abrasive polishing and process

Alumina-zirconia ceramic powders comprise from 10% to 25% by weight of zirconium oxide having specific crystalline phases and from 75% to 90% by weight of aluminum oxide having specific crystalline phases, and have an average particle size of no more than 1,000 .ANG.ngstroms and a two-phase structure wherein the zirconium oxide phase is dispersed in the aluminum oxide phase. A method of making such alumina-zirconia ceramic powders comprises the steps of suspending composite powders having a specific chemical composition and a specific average particle size in water to form a slurry, freeze-drying the slurry, and calcining the freeze-dried powder at atmospheric pressure in air at a temperature of from 800.degree. C. to 1,250.degree. C.

Alumina-zirconia ceramic powders and a method of making the same

A sinterable powdery material of minute composite ceramic particles having a dual structure, comprising the core formed of zirconium oxide and the outer shell formed of aluminum oxide,

Process and an apparatus for producing a sinterable powdery material of

Composite ceramic powders comprising tetragonal zirconium oxide dispersed in fine particles of aluminum oxide, and a method of making such composite ceramic powders.

Composite ceramic powders and a method of making the same

A powdery material of minute composite ceramic particles having a dual structure, comprising the core formed of zirconium oxide and the outer shell formed of aluminum oxide,

Powdery material of minute composite ceramic particles having a dual

This invention relates to a burning furnace of hot gas recirculation type for minimizing fuel cost. The furnace includes a cyclone which receives dust-containing exhaust gases. One or more secondary air-introducing nozzles are provided for the cyclone at top of or in close proximity to the upper end of the cyclone leading concentrically to a flue gas passage such as funnel. Upon introducing secondary air under pressure into the cyclone, a downwardly directing swirling air flow is formed therein for the separation of heavier dust together with part of the fed exhaust gases. The thus separated air-hot gas mixture including heavier dust particles is returned to initial stage of the furnace for the recirculation through the furnace. Lighter combustible soot or the like particles are burnt in a flame curtain formed in the cyclone and finally discharged together with main and substantially dust-free exhaust gas portion constituting an upwardly directing swirling core flow in the downwardly directing and swirling outer air flow, into the flue gas passage.

Hot gas recirculation type burning furnace

Hot gas is introduced into a heat treatment furnace 10 through a plurality of nozzles 11 on the furnace wall to form a conical, downwardly swirling gas flow which is convergent at the top and divergent at the bottom. Such a gas flow pattern both heats the bed below, and acts to contain and oxidize any particles blown or splashed up out of the bed. Exhaust gas is discharged up through the conical apex of the swirling flow. The downward angle .alpha. that each nozzle axis forms with the vertical furnace wall is defined by 0&lt;.alpha..ltoreq.30.degree., and the inclination angle .beta. of each nozzle axis with a horizontal line tangent to the furnace circumference is defined by 45.degree..ltoreq..beta..ltoreq.85.degree..

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Iwaki, Japan

Saburo Hori