METHOD OF OBTAINING ULTRADISPERSE SILICON NITRIDE POWDER Russian patent published in 2015 - IPC C01B21/68 C04B35/58 C04B35/628 

FIELD: chemistry.

SUBSTANCE: method is based on method of self-propagating high-temperature synthesis (SHS - process), in which as charge applied is mixture of powders of preliminarily activated nitride-forming component with average size of particles less than 5 mcm and silicon nitride as diluent with average size of particles less than 1 mcm and width of distribution not higher than 2 in quantity smaller than 25% of the total weight, as nitride-forming component applied is ferrosilicon, after sinter crushing the following milling (disaggregation) of powder is carried out in a jet of pressure gas, supplied in bulk layer, and powder-gas stream is recirculated both inside working volume, separating large particles from working gas by inertial and air-centrifugal separation, and outside it, ejecting separated from stream by cyclone separator small particles and returning them into working volume, and simultaneously above bulk layer and in zone of separation of particles of cyclone separator area of magnetic field is created, into which powder-gas stream is supplied and contact of particles with surface of magnet is realised, and during the entire process voltage, induced by iron particles in powder-gas stream, output from bulk layer, is measured, and, when it reaches minimal (specified) value, the process is continued for not less than three recirculations of material, remaining in working volume, then ejection is stopped, and product is classified into fractions.

EFFECT: obtaining of silicon nitride powders with ultradisperse composition from industrial grades of ferrosilicon with considerably reduced costs for chemical purification from iron admixtures.

12 dwg