Method for the purification of alpha-alumina fibers

An oxide and oxygen separation technology, applied in chemical instruments and methods, alumina/aluminum hydroxide, aluminate/alumina/aluminum hydroxide purification, etc., can solve problems such as incomplete removal of metal impurities

Inactive Publication Date: 2014-09-03
NEOKER
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0012] However, these methods cannot completely remove metal impurities and can only remove metals located in the droplet at the end of the fiber rather than at the fiber surface

Method used

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  • Method for the purification of alpha-alumina fibers
  • Method for the purification of alpha-alumina fibers
  • Method for the purification of alpha-alumina fibers

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0067] Example 1: α-Al 2 O 3 Preparation of whiskers

[0068] α-Al was prepared by placing 99.9 wt% pure aluminum wires (diameter 4 mm, length 1 cm) on a powder bed 2 o 3 whiskers. The powder on the powder bed comprises quartz sand, with additional metals (or metal oxides) of various percentages of transition metals (eg, Ni, Fe, or Co). The metals used are in powder form or in the form of small flakes (spheres, etc.), while the metal oxides used are generally fine powders (<63 μm). The programmed temperature cycle used consisted of an initial ramp rate of 10 °C / min to plateau temperature, a hold of 2 hours to 4 hours, and then cooling of the system to room temperature at a rate of 10 °C / min. The platform temperature was maintained at 1300°C to 1600°C, but a temperature of 1550°C was used most of the time. A furnace with an inner atmosphere of argon was used and an argon flux of 0.2 L / min was maintained during the ramp up and ramp down steps. During the constant...

Embodiment 2

[0069] Example 2: α-Al 2 O 3 Purification of whiskers

[0070] Fibers with an average size of 0.5 μm in diameter and 100 μm to 1 mm in length were placed on 4 alumina ceramic discs measuring 15 x 15 x 1 cm. They are then introduced into the interior of the oven chamber and stacked on top of each other with the aid of aluminum oxide supports. Next, close the furnace and make it airtight by vacuum to achieve 6×10 -2 oxygen partial pressure atm. Then, a programmed temperature cycle was started with an initial heating rate of 5 °C / min to a plateau temperature of 1650 °C for 2 hours, after which the system was cooled to room temperature.

[0071] The purified alumina whiskers were characterized by X-ray diffraction, and this analysis revealed that the only crystalline phase present was the corundum or α-alumina phase ( figure 1 ). Analysis by chemical analysis ICP showed alumina fibers with a purity higher than 99.97%, due to the almost complete removal of transition...

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Abstract

The present invention relates to a method for the purification of alpha-Alpha12O3 whiskers previously obtained by vapor-liquid-solid deposition, under metal vapors-containing atmospheres. Said method involves the volatilization of metal impurities in controlled-atmosphere furnaces at the surface of the fibers and in the drops at the end of the fibers. The invention also relates to purified alpha-Alpha12O3 whiskers obtainable by a process as defined above and substantially free from metal impurities at the surface and at the end part of the fibers, as well as the use of the purified alpha-Alpha12O3 whiskers as defined above as fillers or reinforcement agents for the preparation of ceramic, metallic or polymeric composites.

Description

technical field [0001] The present invention relates to a method for depositing α-Al previously obtained by vapor-liquid-solid deposition (VLS) in an atmosphere containing metal vapor. 2 o 3 Methods of whisker purification. The method includes volatilizing metal and oxide impurities in a controlled atmosphere furnace. Background technique [0002] Fiber-reinforced composites can withstand higher loads than an unreinforced equivalent matrix and have excellent mechanical properties. Composite materials reinforced with continuous fibers provide significant specific strength and stiffness along the fiber direction when compared to composite materials containing specific reinforcements with higher isotropy. [0003] However, fiber-reinforced composites have limited use at elevated temperatures due to oxidation; therefore, stabilized oxide fibers (mainly α-alumina (α-Al 2 o 3 , corundum)) is the best candidate. Their light weight, high stiffness, high fatigue strength and we...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F7/02C01F7/46C30B33/02C30B25/00C01F7/027
CPCC01F7/46C01F7/027C30B29/20C01P2004/03C30B33/02C01P2004/10C01F7/02C30B11/12C01P2002/85C30B29/62
Inventor 卡门·塞雷塞多费尔南德斯维克托·瓦尔卡塞尔华雷斯弗朗西斯科·吉蒂安里韦拉乔斯·米格尔·卡马诺卡斯特罗阿尔弗雷多·罗德里格斯卡雷拉
Owner NEOKER
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