Synthetic method of silicon nitride nanopowder

Abstract

The invention relates to a silicon nitride nano-powder synthesis method. Silica sol, urea and methenamine are evenly mixed to obtain solution, wherein the mol ratio of the urea to the methenamine is 4.7:3-5.6:3, the mol ratio of carbon to silicon is 2.5:1-4:1; the solution is added with cetyl trimethyl ammonium bromide and dilute sulfuric acid for addition reaction, and the acidity of a reaction medium is 6.5-7.5, and the reaction temperature is 50-60 DEG C; then condensation reaction is carried out for the mixture to generate a precursor, wherein the pH value is 3-4, the condensation temperature is 80-90 DEG C; the precursor is dried and ball-ground, and is positioned in a nitriding furnace for calcinations in 2-3L / min nitrogen flow at the temperature of 1480-1520 DEG C for 1.8-2.2 hours to synthesize Si3N4 powder; the silicon nitride nano-powder is prepared by decarbonizing the synthetic Si3N4 powder at the temperature of 570-630 DEG C for 3.7-4.2 hours. The silicon nitride nano-powder synthesis method takes organic carbon as a carbon source, organic nitrogen and nitrogen as a nitrogen source, and the silica sol as a silicon source, and has the advantages of high product quality, low production cost and large production scale. The average particle size of the prepared Si3N4 powder is 43-100nm, and the purity of the Si3N4 powder can be up to 100%.

Description

technical field [0001] The present invention relates to a kind of nano-Si used in the fields of automobile, machinery, metallurgy, chemical engineering, space technology, marine development, electronic technology, medical and health, non-destructive testing, automatic control, radio and television, etc. 3 N 4 Synthetic method of silicon nitride nanometer powder needed for base ceramics. Background technique [0002] Si 3 N 4 As a high-temperature structural material, base ceramics have the characteristics of high density, small thermal expansion coefficient, high hardness, high elastic modulus, thermal stability, chemical stability and electrical insulation. Silicon nitride is not only an excellent high-temperature structural material, but also a new type of functional material. As a high-temperature structural material, it has been applied to the fields of automobile, machinery, metallurgy and chemical engineering, and has gradually penetrated into many cutting-edge sci...

AI Technical Summary

Problems solved by technology

[0004] The above synthesis process is analyzed from several aspects such as product quality, production cost and production scale: the solid phase reaction method is a relatively mature process, but its product quality is limited to a certain extent and it is difficult to break through; the liquid phase reaction method has developed rapidly in recent years , foreign countries have established industrial-scale Si 3 N 4 Powder production line, but on the whole, there are still some technical problems and further cost reduction problems; various gas phase reaction methods can produce high-quality Si 3 N 4 powder, but their production cost is still relatively high, and the production scale is still relatively small

The carbothermal reduction nitriding method has two advantages of low cost and large production scale, but because the carbon thermal reduction nitriding method generally uses silicon dioxide powder as the silicon source, the particles are coarse, and it is difficult to mix with carbon black, which affects the powder quality. particle size and purity

The sol-gel method can produce high-purity ultrafine powder by fully and uniformly mixing the raw materials in the sol state, even at the molecular level (because the sol is made from a solution), but the production cost is high