Synthesis of Si3N4-ZrN composite powder without subsequent milling

Abstract

The behavior of a Si₃N₄ + 4 Zr reaction mixture during the heat treatment in vacuum in the temperature interval 750•1450 °С and the subsequent nitriding of a product of the vacuum treatment at temperatures 1000•1200 °С has been studied. It has been established from to XRD data that the beginning of the dissociation of Si3N4 in vacuum is noted at 750 °С and is accompanied by the formation of zirconium nitrides. Silicon diffusion at 1000 °С is accompanied by the formation of Zr₂Si and ZrSi lower silicide phases. The nitriding process of the highly active product of the vacuum treatment (precursor) with the aim to obtain the Si₃N₄–ZrN composite material has been investigated. It has been established that the optimal regime of synthesis of the Si₃N₄—ZrN composite material in a single technological cycle is the heat treatment in vacuum at 1000 °С (stage 1) and the nitriding at 1200 °С for 1 h (stage 2). The finished product contains only the nitride phases of zirconium and silicon. In the established synthesis regime, composite powders have been obtained in the wide concentration interval 10•40 vol. % ZrN. The synthesis product is a disperse powder of the composite material, not requiring milling, in the form of agglomerates, the particle size of which after the dispersion is in the inetrval 0.2•3.0 µm.