Method for preparing micrometer/nanometer spherical silicon nitride powder

Abstract

The invention discloses a method for preparing micrometer / nanometer spherical silicon nitride powder. The method comprises that liquid silicon tetrachloride is added into liquefied ammonia and an organic solution in a quartz glass reactor, the mixture undergoes a reaction to obtain a yoghourt-type mixture, after deposition, liquid ammonia in an upper layer is drawn, clean liquid ammonia is added into the mixture, the mixture is stirred and precipitated, impurity ammonium chloride is extracted, the reactor and silicam are transferred into a heating furnace, the organic solution is stirred and dried and then is heated to produce amorphous silicon nitride powder, and the amorphous silicon nitride powder is transferred into a silicon carbide or silicon nitride container and then is roasted to form crystalline silicon nitride powder. Silicam powder is prepared by a low temperature reaction, is washed and extracted by liquid ammonia, is purified by ammonium chloride and is subjected to multitime heat treatment to form high-purity micrometer / nanometer spherical silicon nitride powder. The method has a fast preparation rate, a high yield and a high recovery rate, easily controls and improves silicon nitride powder purity and realizes industrial large-scale production.

Description

technical field [0001] The present invention relates to a preparation method of high-purity micron nano-scale silicon nitride powder, in particular to the preparation of diimide silicon by reacting high-purity silicon tetrachloride in high-purity liquid ammonia and organic solution, and the preparation of diimide silicon Purification and heat treatment to prepare high-purity micron nanoscale spherical silicon nitride powder. Background technique [0002] As an important member of the family of high-temperature structural ceramics, silicon nitride ceramics have excellent mechanical properties, thermal properties and chemical stability, such as high room temperature strength and high temperature strength, high hardness, corrosion resistance, oxidation resistance and Good thermal shock resistance and mechanical shock performance, so it is considered by the material science community to be an excellent comprehensive performance, the most application potential and the most promis...

AI Technical Summary

Problems solved by technology

[0013] However, several methods mentioned above to prepare silicon nitride powder have several disadvantages: method (1) is currently the most important industrial production method, but the purity of the product depends on the purity of silicon powder and nitrogen, and in order to improve silicon nitride The silicon nitride powder produced by the powder fineness reaction needs to be broken or ground, and the grinding is easy to cause pollution and cause the particle shape of the silicon nitride powder to be unable to be spherical, and the content of α-Si3N4 is not more than 92%.

The weak point of this method is: 1 reaction adopts nitrogen to carry silicon tetrachloride and ammonia gas reaction yield is lower; 2 pairs of diimide silicon powders heat up and purify under ammonia gas atmosphere and easily make the blockage of by-product ammonium chloride, Corrosion reaction equipment; 3 Diimide silicon powder purified by liquid ammonia washing, filtration and heat treatment cannot control the content of impurity ammonium chloride to less than 0.05%

Images