Preparation method of silicon nitride fiber filtration material

Abstract

The invention belongs to the field of filtration materials, and discloses a preparation method of a silicon nitride fiber filtration material. The preparation method of the silicon nitride fiber filtration material comprises the steps that polyurethane foam is soaked in metal silicon slurry containing nitrogen auxiliaries, the polyurethane foam soaked with the metal silicon slurry is dried and put in a nitrogen furnace to conduct nitridation sintering, metal silicon is converted into a silicon nitride material with an alpha phase fiber structure under the action of the nitrogen auxiliaries, and therefore the silicon nitride fiber filtration material is obtained. The silicon nitride fiber filtration material is high in gas permeability, high in strength, high in corrosion resistance and excellent in thermal shock resistance, and the preparation method of the silicon nitride fiber filtration material has the advantages of being cheap in raw material, simple in technology and low in cost.

Description

technical field [0001] The invention belongs to the technical field of filter material preparation, and in particular relates to a method for preparing a silicon nitride fiber filter material. Background technique [0002] In recent years, smog weather has appeared on a large scale in my country, which has had a huge impact on people's work, life and health, and has become a social problem that needs to be solved urgently; it is generally believed that fine particulate matter and The continuous increase of sulfur and nitrogen oxides is the main reason for the formation of micro-smog weather; therefore, the country has clearly required that various exhaust gases must be filtered to remove fine particles before they are discharged. [0003] When filtering high-temperature exhaust gas, due to the complex use environment, such as high gas temperature, gas corrosion, and the possibility of chemical reactions between soot particles and filter materials, high-temperature soot filter...

AI Technical Summary

Problems solved by technology

[0004] At present, silicon carbide porous ceramic filter material is generally used as the membrane support for high-temperature smoke and dust filtration. Its pore size is relatively large, and a layer of porous membrane with small pore size needs to be formed on its surface by spraying or impregnating; the membrane support is usually clay, cordierite, etc. Material-bonded silicon carbide porous ceramics; for example, the patent application number 201010234149.8 uses Suzhou soil as a binder to prepare a silicon carbide film support, and then sprays a silicon oxide film on its surface; this method prepares high-temperature smoke and dust filter materials. Low cost and other advantages, but in the process of use, due to oxides such as clay and cordierite are easily absorbed by Na in the exhaust gas + 、K + Corrosion will cause the filter material to fail; therefore, to improve the corrosion resistance of the silicon carbide film support, it is necessary to avoid using clay, cordierite and other easily corroded materials as binders to prepare a high-purity silicon carbide film support

[0005] The application number is 201210093466.1. The patent uses an organic polymer binder instead of clay and other oxide binders to prepare a silicon carbide filter tube with a purity of 99%. This method can significantly enhance the corrosion resistance of the filter material and improve its service life. It still cannot solve the problem that the surface film is easy to fall off due to two firings, and there are problems that are difficult to solve: the pure silicon carbide material is difficult to sinter, and its sintering temperature is very high; the sintering temperature of the pure silicon carbide filter material in this patent is at The temperature can reach up to 2400°C under vacuum or inert atmosphere, which is very demanding on the sintering kiln, and the production cost is very high; on this basis, the patent application number 201210094292.0 proposes a one-time firing preparation method, that is, on the silicon carbide film support After the body is formed, a porous film of the same material is sprayed on the surface, and then fired to shape; this method further solves the problem of surface film peeling off, but it still has the problems of difficult sintering and high cost, and has not yet been used in practice.

[0006] Silicon nitride and silicon carbide have similar excellent performance, but due to the high price of raw materials, the application of silicon nitride in this area is less; Japanese Asahi Glass Co., Ltd. proposed a Chinese patent with the application number of 200410069982.6. Raw material, add 5~40% ceramic hollow particles or organic burn-off agent and other pore-forming materials. The molding method is compression molding or extrusion molding or casting molding, and then first nitriding at 1200~1400 °C at low temperature, and then heating up to 1600~ Heat treatment at 1800°C to prepare silicon nitride filter; this method uses cheaper metal silicon as raw material, but the heat treatment needs to be carried out twice, the process is complicated and the cost is high, and the prepared silicon nitride filter belongs to porous ceramics, and its average Pore ​​diameter greater than 7μm

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