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Mullite whisker-mullite composite coating and preparation process thereof

A mullite whisker and composite coating technology, applied in the field of non-metallic materials, can solve the problems of difficult to obtain a dense coating, low sol solid content, coating defects, etc., and achieve excellent high-temperature oxidation resistance and raw material source. Wide range of effects with low production costs

Inactive Publication Date: 2006-06-28
WUHAN UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The slurry impregnation method is mainly used to coat the ceramic surface with mullite coating. However, due to the large particle size of the coating, the impregnation of the micropores in the matrix is ​​not ideal, and the coating thickness is uneven, which is easy to cause cracking of the coating. In addition, the sintering temperature of mullite is very high, it is difficult to obtain a dense coating
Sol-gel can prepare a uniform coating, and the heat treatment temperature of the coating is low, but the solid content of the sol is very low, and it takes more than ten times of coating to obtain a coating with a thickness of micron, and the sol is easy to crack when it is dried and sintered. Causes coating defects; plasma spray and brush methods can only form coatings on the substrate surface
Although the vapor deposition method can obtain a coating deep in the substrate, the vapor deposition has high requirements on equipment, process parameters and working environment, and its industrial application is limited.

Method used

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  • Mullite whisker-mullite composite coating and preparation process thereof
  • Mullite whisker-mullite composite coating and preparation process thereof
  • Mullite whisker-mullite composite coating and preparation process thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0042] (1) Preparation of mullite slurry: using ultra-fine industrial α-Al 2 o 3 Micropowder (AL 2 o 3 ≥99.6%, d 50 ≤1.0μm) and industrial quartz powder (SiO 2 ≥99.1%, d 50 ≤1.0μm) as raw material, add 5% alumina sol (pH: 6.7~7.3, Al 2 o 3 Concentration: 10±0.5%) and silica sol (pH: 6.5~8.0, SiO 2 Concentration: 30±1%) so that the proportion of alumina and silica conforms to the stoichiometric ratio of mullite (Al 2 o 3 : SiO 2 The mass ratio is 3:1), adding 6% BaF 2 (chemically pure), adjust the pH value to 7.0 to 8.0, ball mill for 10 to 24 hours according to the ratio of material: ball: water of 1:1:0.5, cast the green body into a green body, and keep the green body at 1400 to 1550°C for 1 hour ~3 hours to synthesize mullite. Crush the synthesized mullite to less than 2mm, put it into a planetary ball mill for 2 hours according to the material: ball: water ratio of 1:1.5:0.4, and make the particle size d 50 ≤1.5μm slurry.

[0043] (2) Coating coating: put recr...

Embodiment 2

[0047] (1) Preparation of mullite slurry: using kaolin as the main raw material (SiO 2 : 52±0.5%, Al 2 o 3 : 45±0.5%, d 50 ≤2.0μm), add Al according to the clay composition 2 o 3 and SiO 2 (particle size, purity with embodiment 1), adjust the ratio of the two to make it meet the mullite proportioning (Al 2 o 3 : SiO 2 The mass ratio is 3:1), adding 8% BaF 2 Do mineralizers. The process of ball milling, molding, sintering and preparing mullite slurry is the same as in Example 1.

[0048] (2) Coating: Vacuum-coat recrystallized silicon carbide with SiO 2 Sol (pH: 6.5~8.0, SiO 2 Content: 10±1%) and Al 2 o 3 Sol (same as embodiment 1), repeat 3 times. Vacuum-coat mullite slurry and dry at 70-80°C. The two-step coating process can be repeated 3 times depending on the specific situation to ensure the thickness of the coating. The coated material is sintered in air at 1100-1400° C. (same as Example 1).

[0049] In this example, the steps of coating the sealing layer ...

Embodiment 3

[0051] (1) Preparation of mullite slurry: industrial fused mullite and its mass 5% BaF 2 , 5% AlF 3 In the planetary ball mill ball mill, prepared into mullite slurry (mullite particles d 50 = 1.5 μm).

[0052] (2) Coating coating: vacuum-coat SiO with a silicon nitride bonded silicon carbide material with a porosity of 11% 2 Sol, drying (same as embodiment 2). Vacuum coated Al 2 o 3 Sol, drying (with embodiment 1). Vacuum coating mullite slurry, drying (same as embodiment 2), ensures the compactness of coating. Sintering in air at 1100-1400°C (same as Example 1).

[0053] In this example, the steps of coating the sealing layer and densifying the coating are the same as in Example 1.

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Abstract

The invention relates to mullite crystal whisker mullite compounding coating layer that the manufacture method includes the following steps: coating the mixture slime of silica sol, aluminum sol and mullite slime in vacuum of the basal material, or coating orderly, under the catalyzing effect of metal fluoride mineralizer, sintering by high temperature. The invention is simple structure, low cost of raw material, acid proof, alkali proof, etc. it could improve the intension of the material and prolong the use life.

Description

technical field [0001] The invention relates to the field of non-metallic materials, in particular to a mullite whisker-mullite composite coating and a preparation method thereof. Background technique [0002] In recent years, with the wide application of high-temperature structural ceramics, especially non-oxide structural ceramics (such as sialon, silicon carbide, silicon nitride ceramics, etc.) . At present, the high-temperature anti-oxidation coatings used for non-oxide ceramics are mainly molybdenum disilicide, alumina, silicon oxide, spinel, mullite and other systems. Mullite has excellent mechanical properties, and its thermal expansion rate is similar to that of non-oxide ceramics such as silicon carbide in a wide range. Moreover, the preparation process of mullite coating is simple and inexpensive. The good stability of mullite coating in oxidizing atmosphere and acidic and alkaline conditions makes it have a good application prospect in the field of high-temperat...

Claims

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Application Information

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IPC IPC(8): C04B35/185C04B41/85
Inventor 武七德孙峰王浩吉晓莉田庭燕王友兵郭万里
Owner WUHAN UNIV OF TECH
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