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Calcined alumina, its production process and produced fine alpha-alumina powder

A kind of bauxite, calcination technology, applied in the field of fine α-alumina powder, can solve the problems of uneven particle size, inability to provide mechanical strength and corrosion resistance, and the passage of viscosity time

Inactive Publication Date: 2007-08-22
SUMITOMO CHEM CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] However, in the method of calcination at low temperature, the θ phase, which is different from the α phase, tends to remain, so this method is difficult to prepare alumina powder with a single α phase
In general, if the α-alumina powder containing the θ phase is molded and calcined, a sintered body with a high density cannot be obtained sometimes
Furthermore, in some cases, if the α-alumina powder is dispersed into water to prepare a slurry, the viscosity of the slurry will change with the passage of time, and some defects will occur during the molding process.
In the method of adding a silicon compound and calcining the mixture, in some cases, alumina powder with a certain degree of fineness can be obtained, but the sintered body obtained after molding and sintering has a particle size that is not Uneven, unable to provide sufficient mechanical strength and corrosion resistance

Method used

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  • Calcined alumina, its production process and produced fine alpha-alumina powder
  • Calcined alumina, its production process and produced fine alpha-alumina powder
  • Calcined alumina, its production process and produced fine alpha-alumina powder

Examples

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example

[0035] The present invention is described in more detail with the following examples, but it is not intended to limit the scope of the present invention. The BET specific surface area, crystal phase, and contents of silicon, iron, titanium, sodium, and calcium were determined in the following manner.

[0036] BET specific surface area (m 2 / g): This is judged by the nitrogen adsorption method.

[0037] Crystal phase: The sample is analyzed with an X-ray winding instrument (commercial name: "Rint-200", manufactured by Rigaku Denki K.K.), and the crystal phase is defined by the peak signal in the XRD spectrum, showing the highest The crystal phase with relative peak intensity is the main crystal phase.

[0038] The content of silicon, iron, titanium, sodium and calcium (ppm): it is determined by radioactive spectrochemical analysis.

example 1

[0040] [Preparation of transitional alumina powder]

[0041] Aluminum hydroxide is obtained by hydrolyzing aluminum isopropoxide, and then the aluminum hydroxide is calcined to obtain transitional alumina, the main crystal phase of which is θ phase and contains 3% by weight of α-alumina. Regarding the content of α-alumina in the transitional bauxite, the transitional bauxite is analyzed with an X-ray detector (XRD), and the results of the XRD spectrum are compared with the standard spectrum to calculate the content of the α-alumina, Wherein the standard spectrum is obtained by adding a fixed amount of α-alumina to transition alumina. The above-mentioned transitional alumina is pulverized by a jet mill, and the obtained transitional alumina has an integral density of 0.21g / cm 3 .

[0042] [Manufacturing calcined bauxite]

[0043] 100 g of transitional alumina powder was charged into a tubular electric furnace (manufactured by Motoyama K.K) with a volume of 8 liters, and dry ...

example 2

[0048] α-alumina powder having an average particle size of 0.1 μm is added to aluminum isopropoxide, and then the mixture is hydrolyzed to obtain aluminum hydroxide, wherein the main crystal phase of this aluminum hydroxide is pseudo-boehmite and contains 1 % by weight of α-alumina.

[0049] 100 g of the above aluminum hydroxide was calcined under the same conditions as in Example 1 [production of calcined alumina] to obtain calcined alumina. The BET specific surface area of ​​this calcined bauxite is 14m 2 / g, and its main crystal phase is α phase without θ phase, and its average particle size is 0.1 micron.

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Abstract

Calcined alumina with a BET (Brunauer Emmett Teller) surface area of 10-20 m2 / g and an average particle size of 0.5 microns or less, in which the principal crystalline phase is an alpha phase with no theta phase, is new. Independent claims are also included for the following: (1) production of calcined alumina by calcining a substance containing alumina and no other metal in an atmosphere with a steam partial pressure of 600 Pa or less; (2) fine alpha-alumina powder which has a purity of at least 99.99% and a BET surface area of at least 15 square m / g, is free of transitional alumina, and produces a fritted product with a relative density of at least 95% when calcined at 1250 degrees C and atmospheric pressure.

Description

technical field [0001] The present invention relates to a calcined alumina, its production method and fine α-alumina powder prepared from the calcined alumina. Background technique [0002] α-alumina powder is a raw material widely used in the manufacture of various ceramic products such as sintered bodies and translucent pipes, and abrasives or the like. The α-alumina powder can be obtained by calcining an aluminum compound in air, such as aluminum hydroxide, transition alumina, alumamine, aluminum chloride, and aluminum carbonate amine. [0003] The fine powder of α-alumina contributes to the sintering properties. When fine α-alumina powder is used for the sintered body, dense results can be obtained even though the sintering temperature is rather low. Since the particle size of the sintered body can be kept relatively small, a sintered body having high mechanical strength can be produced. Therefore, fine α-alumina powders are in demand. [0004] Among the known method...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C01F7/02C01F7/38C22B1/02C01F7/441
CPCC04B2235/5409C04B2235/5445C01F7/02C04B35/6268C04B2235/3217C01P2006/12C01F7/441C04B2235/5454C04B35/62645C04B2235/72C04B2235/77C01P2002/72C04B2235/604C04B35/111C01P2004/04C01P2004/62B82Y30/00
Inventor 梶原和久竹内美明
Owner SUMITOMO CHEM CO LTD