SYNTHESIS OF COMPOSITE OF SILICON NITRIDE, ALUMINIUM NITRIDE, ZIRCONIUM NITRIDE FROM COMPLEX FERROALLOY - FERRO-ALUMINIUM-SILICON-ZIRCONIUM BY NITRIDING IN COMBUSTION MODE

In this paper a composite material consisting of silicon nitride, zirconium nitride and aluminum nitride is obtained from a complex ferro-aluminum-silicon-zirconium (FASZ) alloy by self-propagating high-temperature synthesis. The effect of the sample diameter, nitrogen pressure, the dispersity and density of the initial ferro-aluminum-silicon-zirconium powder on the amount of absorbed nitrogen, rate and temperature characteristics of combustion under the nitrogen atmosphere is investigated. It is shown that with increasing pressure the amount of absorbed nitrogen and the rate and temperature of combustion increase. Increasing the density of the initial powder leads to decreasing the amount of absorbed nitrogen and the rate and temperature of combustion. Increasing the diameter of the initial samples, consisting of ferroalloy powder, does not lead to a significant change in the amount of absorbed nitrogen, but decreases the rate of combustion and increases the temperature of synthesis. Changes in the dispersity of the initial ferro-aluminumsilicon-zirconium do not significantly affect the amount of absorbed nitrogen and the rate and temperature of combustion. It has been revealed that the combustion wave front propagates along the sample under the nitrogen atmosphere in a nonstationary mode, and the obtained composites have a macro-heterogeneous structure. The optimal conditions of nitriding ferro-aluminum-silicon-zirconium are found: nitrogen pressure, diameter of the initial sample, dispersity and density of the initial powder. The critical parameters of nitriding ferro-aluminum-silicon-zirconium by self-propagating high-temperature synthesis, at which the combustion wave front forms and propagates in the initial ferroalloy, are revealed. The probable reactions of nitriding the initial material in the combustion wave are given. The phase composition of the products obtained by nitriding ferro-aluminum-silicon-zirconium is determined by X-ray diffraction analysis. A composite material containing silicon nitride, aluminum nitride and zirconium nitride is obtained.