Synthesis and Consolidation of Powders Based on Si3N4–Zr

The behavior of a Si3N4 + 4 Zr reaction mixture during heat treatment in vacuum in the temperature range 750–1450 °C and subsequent nitriding of the product of vacuum treatment at temperatures 1000–1200 °C has been studied. It has been established by the XRD method that the dissociation of Si3N4 begins at 750 °C and is accompanied by the formation of zirconium nitrides, and silicon diffusion at 1000 °C is accompanied by the formation of the Zr2Si and ZrSi lower silicide phases. The nitriding process of the highly active product of vacuum treatment (precursor), aimed at obtaining a 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 a heat treatment in vacuum at 1000 °C (stage 1) and nitriding at 1200 °C for 1 h (stage 2). The finished product contains only nitride phases of zirconium and silicon. In the established synthesis regime, composite powders have been obtained in the wide concentration range 10–40 vol.% ZrN. The synthesis product is a disperse powder of the composite material in the form of agglomerates, the particle size of which after dispersion lies in the range 0.2–3.0 μm. The spark plasma sintering has made it possible to obtain specimens with a relative density above 97% at a temperature of 1750 °C. This is connected with the formation of a continuous conductive three-dimensional network of ZrN particles.