The process of carbothermal reduction of SiO2 in a nitrogen flow at te
mperatures of 1673-1723 K was investigated. It was established that mi
xtures obtained by the sol-gel technique are not microhomogeneous and
consist of silica and carbon aggregates, inside which the processes of
structure and phase ordering occur during heat treatment. The contact
region of these aggregates is the place where SiO2 reduction occurs.
In this region the following transformation takes place: partial SiO2
reduction, appearance of a film of melt of the composition SiOx, where
x < 2, enveloping of the carbon particles by this melt, destruction-a
ctivation of the carbon particles, implantation of nitrogen in the hig
hly oxygen-defective melt, formation of silicon oxynitride and, subseq
uently, silicon nitride. alpha-Si3N4 forms in the presence of a large
carbon nucleus, beta-Si3N4 forms in its absence (or on two-dimensional
particles).