A kind of method for preparing silicon oxynitride powder under air atmosphere

Abstract

The invention discloses a method for preparing silicon oxynitride powder in an air atmosphere. According to the method, silicon powder is used as a raw material, silicon powder accumulation bodies with different particle sizes and thicknesses are subjected to nitrogen oxidation synthesis under the conditions of normal pressure and high temperature, and then an upper-layer micro-sintering state anda small amount of edge products are removed to obtain a silicon oxynitride powder finished product. Compared with the prior art, the invention has the advantages that: silicon oxide, silicon nitrideand other impurity phases generated by the nitrogen oxidation reaction can be easily separated from silicon oxynitride, so that the product purity is greatly improved, the yield is very high, normal-pressure air is used as a nitrogen source and an oxygen source, the cost is saved, and the preparation method is simple in process, easy to operate, low in cost and suitable for industrial large-scaleproduction.

Description

technical field [0001] The invention relates to the technical field of preparation of inorganic non-metallic powder materials, in particular to a method for preparing silicon oxynitride powder in an air atmosphere. Background technique [0002] Silicon oxynitride (Si 2 N 2 O) Because of its very good thermal shock resistance, high temperature resistance strength, high temperature oxidation resistance and low thermal expansion coefficient, it is widely used in high temperature structural materials and refractory materials. In the prior art, there are many methods for preparing silicon oxynitride powder. Among them, the direct nitriding reaction of silicon powder in a nitrogen-oxygen mixed gas or the direct nitriding reaction of silicon powder is used. Because the direct nitrogen oxidation of silicon powder is not only low cost It can also avoid impurity pollution, which is also one of the more commonly used methods. [0003] However, as documented in Liangliang et al. Cond...

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Problems solved by technology

[0003] However, as documented in Liangliang et al. Conditions for gas-phase nitriding and nitrogen oxidation of crystalline silicon powder (Journal of Materials Science and Engineering, 2010, 28(3): 416-420), this process is due to silicon and N 2 and O 2 There is a kinetic competition relationship between the reactions, and there is an obvious gradient in the oxynitride product, that is, the generated product includes silicon oxide, silicon oxide and silicon oxynitride mixed layer, silicon oxynitride layer, silicon oxynitride layer from top to bottom. With the gradient phenomenon of the silicon nitride mixed layer, silicon nitride layer, residual silicon, etc., if the ratio of oxygen to nitrogen and the partial pressure of oxygen are not well controlled, it is easy to cause the gradient distance of the pure silicon oxynitride phase along the reaction gas flow direction to be small , so that the prepared oxynitride finished product usually contains cristobalite, silicon nitride by-product phase or residual silicon, and it is difficult to obtain a pure phase silicon oxynitride product sample, resulting in a low yield of silicon oxynitride powder

In addition, the literature uses the mixed gas of nitrogen and oxygen in a slightly positive pressure flow state as the source of oxygen and nitrogen. When the upper layer of the silicon material accumulation body consumes most of the oxygen, the oxygen can still be quickly replenished into the inside of the accumulation body, resulting in the consumption of the upper layer of silicon. The amount of powder has increased significantly

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