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A method for in-situ synthesis of mullite whisker self-toughened mullite ceramics

A technology of mullite whisker and in-situ synthesis, which is applied in the field of silicon-alumina composite ceramics, can solve the problems of not using the mechanical properties of the matrix, improvement, and high energy consumption, and achieve the effect of avoiding cracking and uneven shrinkage

Active Publication Date: 2020-03-17
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method can successfully prepare mullite whiskers evenly in the fired ceramics, but if the uniformly distributed whiskers in the ceramics do not control the aspect ratio, they will not take advantage of the enhancement of the mechanical properties of the matrix; Xu Xiaohong et al. [2] With kaolin and industrial Al(OH) 3 As raw material, add V 2 o 5 and AlF 3 In situ synthesis of mullite whiskers
The preparation is simple, but the use of minerals as raw materials is not conducive to the improvement of material purity and may introduce other impurities; T.S.Zhang et al. [3] The mullite precursor synthesized by the sol-gel method was used as the matrix, and the industrial mullite powder after high-energy ball milling was added as the seed crystal to prepare dense mullite ceramics with an interlocking structure.
This method proposes the use of high-energy ball milling to prepare seed crystals, but the ball milling takes a long time and consumes a lot of energy

Method used

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  • A method for in-situ synthesis of mullite whisker self-toughened mullite ceramics
  • A method for in-situ synthesis of mullite whisker self-toughened mullite ceramics
  • A method for in-situ synthesis of mullite whisker self-toughened mullite ceramics

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Experimental program
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Effect test

Embodiment 1

[0091] Step (a): Seed crystal preparation:

[0092] According to the composition formula Al 2 o 3 : SiO 2 =3:2. The mullite precursor was synthesized by the sol-gel method, using tetraethyl orthosilicate as the silicon source (0.1mol; 20.833g), Al(NO 3 ) 3 9H 2 O is the aluminum source, take X=2.4, dissolve the aluminum source and the silicon source in a molar ratio of (3-2.4):1 in 100mL of absolute ethanol, add 25g of glacial acetic acid, and Heat and reflux in a water bath at 60°C for 4 hours; then add the remaining aluminum nitrate so that the total Al / Si ratio conforms to the mullite stoichiometric ratio Al / Si=3:1, and add 1600 μL of hydrofluoric acid dropwise, and heat up to 85°C Heated in a water bath to reflux for 12 hours and then cooled to room temperature to obtain a precursor gel. Then the gel was dried, ball-milled for 2 hours, and heated at 10°C / min to 1000°C for calcining to obtain a mullite precursor powder (mullite whisker seed crystal), which was used a...

Embodiment 2

[0098] Step (a): Seed crystal preparation:

[0099] According to the composition formula Al 2 o 3 : SiO 2 =3:2. The mullite precursor was synthesized by the sol-gel method, using tetraethyl orthosilicate as the silicon source (0.1mol; 20.833g), Al(NO 3 ) 3 9H 2 O is the aluminum source, take X=2.4, dissolve the aluminum source and the silicon source in a molar ratio of (3-2.4):1 in 100mL of absolute ethanol, add 25g of glacial acetic acid, and Heat and reflux in a water bath at 60°C for 4 hours; then add the remaining aluminum nitrate so that the total Al / Si ratio conforms to the mullite stoichiometric ratio Al / Si=3:1, and add 1600 μL of hydrofluoric acid dropwise, and heat up to 85°C Heated in a water bath to reflux for 12 hours and then cooled to room temperature to obtain a precursor gel. Then the gel was dried, ball-milled for 2 hours, and heated at 10°C / min to 1000°C for calcination to obtain a mullite precursor powder, which was used as a seed crystal for whisker ...

Embodiment 3

[0105] Step (a): Seed crystal preparation:

[0106] According to the composition formula Al 2 o 3 : SiO 2 =3:2. The mullite precursor was synthesized by the sol-gel method, using tetraethyl orthosilicate as the silicon source (0.1mol; 20.833g), Al(NO 3 ) 3 9H 2 O is the aluminum source, take X=2.4, dissolve the aluminum source and the silicon source in a molar ratio of (3-2.4):1 in 100mL of absolute ethanol, add 25g of glacial acetic acid, and Heat and reflux in a water bath at 60°C for 4 hours; then add the remaining aluminum nitrate so that the total Al / Si ratio conforms to the mullite stoichiometric ratio Al / Si=3:1, and add 1600 μL of hydrofluoric acid dropwise, and heat up to 85°C Heated in a water bath to reflux for 12 hours and then cooled to room temperature to obtain a precursor gel. Then the gel was dried, ball-milled for 2 hours, and heated at 10°C / min to 1000°C for calcination to obtain a mullite precursor powder, which was used as a seed crystal for whisker ...

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Abstract

The invention discloses a method for in-situ synthesizing mullite whisker self-toughened mullite ceramics. The method comprises the following steps: mixing 55-70 parts by weight of aluminum oxide, 20-30 parts by weight of silicon dioxide, 5-18 parts by weight of mullite whisker seed crystal, and 2-5 parts by weight of aluminum fluoride in a manner of wet grinding; pouring and curing to obtain a green body; sintering the green body at the temperature of 500 to 600 DEG C for the first time; sintering at the temperature of 900 to 1000 DEG C for the second time; sintering at the temperature of 1350-1550 DEG C for the third time so as to obtain the mullite ceramics. In addition, the invention also discloses the mullite ceramics prepared by the abovementioned method. According to the method, the raw materials, namely, aluminum oxide and silicon dioxide based on the ratio, conduct reaction under the synergistic effect of mullite whisker seed crystal and aluminum fluoride in parts by weight through the sectional sintering technology under the abovementioned temperature to obtain the high-toughness in-situ self-growth mullite whisker mullite ceramics; the high-activity seed crystal is added, so that the in-site uniform and dispersed distribution of the mullite whiskers in a substance can be realized, and thus the toughness of the ceramics can be effectively improved.

Description

technical field [0001] The invention belongs to the technical field of silicon-aluminum composite phase ceramics, and specifically relates to a method for in-situ synthesis of mullite whisker self-toughening mullite ceramics. The ceramic material can be mainly used in high-temperature thermal structural components. Background technique [0002] Mullite has the advantages of high melting point, low thermal expansion coefficient, good thermal shock resistance and creep resistance. The high-temperature mechanical properties of dense mullite ceramics are particularly prominent. Usually, the high-temperature strength is higher than the room temperature strength. The strength at 1300 ° C is 1.7 times that at room temperature, and the strength retention rate at 1500 ° C can reach more than 90%. The use of high-purity and ultra-fine alumina and silica powder is expected to improve the purity of mullite products while controlling costs and achieve more ideal performance. [0003] Al...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C04B35/80C04B35/185C04B35/626C04B35/64
CPCC04B35/185C04B35/62605C04B35/64C04B2235/661C04B2235/6562C04B2235/6567C04B2235/6023C04B2235/445C04B2235/96
Inventor 肖鹏俞晓宇李专
Owner CENT SOUTH UNIV