PLASMA-CHEMICAL SYNTHESIS OF ULTRAFINE SILICON-NITRIDE (SI3N4) POWDERIN A REACTOR WITH AN ELECTRIC-ARC PLASMATRON

The main elements are presented of a theoretical approach for thermody namic calculation and for calculations of two-phase flow in a plasmatr on together with the main design decision for a plasma unit, including both the method of feed of the starting materials, freezing of the st ream, and recovery of the powder product, as well as results of an inv estigation of the properties of the obtained powder. Ultrafine (approx imately 20-nm) silicon nitride (Si3N4) particles were synthesized in a reactor with an electric-arc plasmatron with a linear circuit with ed dy arc stabilization. Metallic silicon and a nitrogen-ammonia gas atmo sphere were used for preparation of the silicon nitride. The powder pa rticles were collected on a bag filter and on the wall of the plasma-c hemical reactor. The powder samples consisted mainly of an amorphous p hase with a smaller fraction of alpha and beta phases and traces of si licon.