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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  • Abstract
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  • Claims
  • Application Information

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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 prepared by pyrolysis of imine-based silicon 3 N 4 Powder (represented by the products of Ube Corporation in Japan), no one in the world has prepared a water-based concentrated suspension with a solid phase content of 50vol%.
[0004] To sum up, people still don't know the key factors to control the dispersibility of silicon nitride powder in water, and haven't found a simple and easy treatment method to make silicon nitride powder of different manufacturers and brands have similar Good dispersion performance, making its water-based suspension reach the highest possible solid content required by the in-situ solidification molding process

Method used

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Experimental program
Comparison scheme
Effect test

Embodiment 1

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

Embodiment 2

[0020] Domestic commercially available silicon nitride powder has an α-phase content greater than 90%, a volume average moment diameter of 2.69 μm, a wide particle size distribution range, and very irregular particle shapes, with many long columnar particles. The preparation process of the powder is the direct nitriding method of silicon powder, and the nitrided product is obtained by ball milling and drying with ethanol as the medium. There are a lot of hydrophobic Si-O-C on the surface of the powder particles 2 h 5 group, which 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 modification process of the powder 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 24 hours. 2) The...

Embodiment 3

[0022] Imported commercial silicon nitride powder has an α phase content of 91.7%, a volume average moment diameter of 0.51 μm, a nearly spherical particle shape, and a narrow particle size distribution. The preparation process of the powder is also the direct nitriding method of silicon powder, and the product after silicon powder nitriding is crushed and then free silicon, oxygen and other impurities are removed 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 particle surface. The water-based suspension of the initial powder at a shear rate of 60s -1 , when the apparent viscosity is 1Pa·s, its solid phase volume fraction is 42vol%. The modification process of the powder is as follows: 1) the 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, and the...

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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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