Production method of high-content alpha-crystal form silicon nitride powders

Abstract

The invention discloses a production method of silicon nitride powders, in particular relates to a novel production method of silicon nitride powders with high content of alpha-Si3N4, and belongs to the technical field of inorganic chemistry. The method comprises the following steps: firstly pre-treating powdery raw materials by mechanical activation, and feeding a mixed diluting agent of alpha-Si3N4 and non-crystalline Si3N4 during the direct nitridation of silicon powders at a high temperature under normal pressure. By controlling the addition ratio of the diluting agent and the nitridation time and temperature, the silicon nitride powders with high content of alpha-Si3N4 are synthesized. The process improves the activity of solid-phase reactants, promotes the reaction between Si and N2, does not need high-temperature and high-pressure conditions, is easy to operate, adopts easily-available raw materials, increases the purity of products, has a low coat and a high efficiency, and is environment-friendly and energy-saving. The process is economical and highly-efficient and suitable for large-scale production.

Description

technical field [0001] The invention relates to a method for producing silicon nitride powder, in particular to an α-Si 3 N 4 The invention relates to a new production method with relatively high content, which belongs to the technical field of inorganic chemistry. Background technique [0002] Silicon nitride (Si 3 N 4 ) is an important structural material, known as the "all-around champion" in ceramic materials. It is a superhard substance, which is not only an excellent high-temperature structural material, but also a new type of functional material. It has lubricity and wear resistance. It does not react with other inorganic acids except hydrofluoric acid. It has strong corrosion resistance and oxidation resistance at high temperatures. It can also resist cold and heat shocks and can be heated to 1000°C in the air. Above, rapid cooling and rapid heating will not shatter. In terms of physical properties, silicon nitride materials have high hardness, wear resistance,...

AI Technical Summary

Problems solved by technology

The quality of silicon nitride powder depends on its preparation method. At present, the commonly used preparation methods are: direct silicon powder nitriding method, carbothermal reduction method, silicon halide ammonium solution method, preparation of precursor method, chemical double decomposition method, in-situ synthesis method , silicon alloy ammonolysis method, etc., generally have the following disadvantages: it is prepared by sintering of large-particle silicon nitride and multi-phase powder, with high brittleness, poor uniformity, low reliability, poor toughness and strength, which greatly restricts its application.

The high-pressure synthesis process not only increases the production cost due to high equipment investment, but also brings safety hazards to production

Judging from the index test and test firing results of silicon nitride powder at home and abroad, the Si produced by the most representative domestic enterprises 3 N 4 The average particle is about 3 microns, and the content of metal impurities is high, which makes it difficult to meet the requirements of qualified products, while the imported powder is less than 0.7 microns

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