Prepn of dense water-base silicon nitride suspension

A silicon nitride water-based and suspension technology, applied in the field of ceramic materials, can solve problems such as differences in dispersion performance, failure to find, and differences in dispersion characteristics, so as to achieve good application prospects, realize industrialization, and expand the application range.

Inactive Publication Date: 2002-05-15
TSINGHUA UNIV
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Problems solved by technology

The limitations of this method are: 1) With the different production processes, the dispersion characteristics of ceramic powder are very different for the same dispersant; and, 2) even if the same brand of powder provided by the same manufacturer, different batch numbers, the dispersion performance may also have a large difference
For Si powder produced by direct nitriding method 3 N 4 Powder, currently only a few researchers have prepared a water-based concentrated suspension with a solid phase content higher than 50vol% for powder with good initial dispersion performance, but the method is not universal
And for the Si prepare

Method used

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Examples

Experimental program
Comparison scheme
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Example Embodiment

[0017] Example 1:

[0018] Si 3 N 4 The powder is a domestic commercial powder, the content of α phase is greater than 90%, the average diameter of the volume moment of the particles is 1.14 μm, and the shape of the particles is irregular. The preparation process is a silicon powder direct nitridation method, and the product after silicon powder nitridation is obtained by vibrating and pulverizing with tap water as a medium and directly dried without further impurity removal treatment. The initial dispersion performance of this kind of powder is very poor, at a shear rate of 60s -1 When the apparent viscosity is 1Pa·s, the volume fraction of the suspension is 37vol%. The limiting factor of the powder dispersion performance is the soluble high-valent counter ion Ca in the powder 2+ And Mg 2+The content is very high. The powder modification treatment process is as follows: 1) Silicon nitride powder and high-purity deionized water are mixed to form a 12 vol% suspension, and tetrameth...

Example Embodiment

[0019] Example 2:

[0020] The domestic commercial silicon nitride powder has an alpha phase content of more than 90%, a volume average moment diameter of 2.69 μm, a wide range of particle size distribution, very irregular particle shapes, and many long columnar particles. The preparation process of the powder is a direct nitridation method of silicon powder, and the nitrided product is obtained by pulverizing and drying by ball milling with ethanol as the medium. There is a lot of hydrophobic Si-O-C on the surface of the powder particles 2 H 5 The group limits its dispersibility in water. At a shear rate of 60s -1 When the apparent viscosity is 1Pa·s, the volume fraction of the suspension is 33vol%. The powder modification treatment process is as follows: 1) Silicon nitride powder and high-purity deionized water are mixed to form a 20vol% suspension, and tetramethylammonium hydroxide is added to adjust the pH to 13, and the material-to-ball ratio is 1: 1. Ball mill at 400 rpm for...

Example Embodiment

[0021] Example 3:

[0022] Imported commercial silicon nitride powder has an alpha phase content of 91.7%, a volume average moment diameter of 0.51μm, a nearly spherical particle shape, and a narrow particle size distribution. The preparation process of the powder is also the direct nitridation of silicon powder, and the nitrided product of the silicon powder is crushed to remove free silicon, oxygen and other impurities with hydrochloric acid and hydrofluoric acid. Soluble NH in the powder 4 + The ion concentration is very high, and there are a large number of amine groups on the surface of the particles. The water-based suspension of the initial powder is at a shear rate of 60s -1 When the apparent viscosity is 1Pa·s, the solid phase volume fraction is 42vol%. The powder modification treatment process is as follows: 1) Silicon nitride powder and high-purity deionized water are mixed to form a 30vol% suspension, and tetramethylammonium hydroxide is added to adjust the pH to 13.5...

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Abstract

This invention relates to a preparation method for aqueous concentrated suspension of silicon nitride. Firstly, silicon nitride powder is compounded into a slurry, its pH value is regulated with tetramethyl ammonium hydroxide, then the slurry is ground in ball mill, the above-mentioned powder is washed several times with deionized water as medium to remove solubable matter and high-valency counterion, it is thermo-insulated in air atmosphere, and finally the modified silicon nitride powder is added to high-purity deionized water, the suspension is regulated for pH value with tetramethyl ammonium hydroxide and is further ground in ball mill so to prepare the aqueous concentrated suspension of silicon nitride with low viscosity and high solid-phase content. By use of silicon nitride powder from different sources with similar good dispersivity, the aqueous concentrated suspension with solid-phase content higher than 50 vol.% can be prepared.

Description

technical field [0001] The invention relates to a method for preparing a silicon nitride water-based concentrated suspension, belonging to the technical field of ceramic materials. Background technique [0002] Silicon nitride-based ceramics have excellent properties such as high strength, high hardness, oxidation resistance, corrosion resistance and thermal shock resistance, and are a promising high-temperature structural material. However, silicon nitride ceramics manufactured by conventional processes limit their application range due to reasons such as high cost and low reliability, which are also two major problems facing the application of all high-performance ceramics. The molding process is an important link in the preparation of ceramic materials, and it is also a key link in improving the uniformity of ceramic bodies and solving the reliability of ceramic materials. The in-situ solidification colloidal molding process proposed in recent years, such as Gel-casting ...

Claims

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Application Information

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IPC IPC(8): C04B35/584
Inventor 黄勇代建清谢志鹏杨金龙马天
Owner TSINGHUA UNIV
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