Study of phase formation mechanisms in composite xSi3N4 – (1-x)ZrO2 ceramics and their role in hardening of ceramics

Abstract

The paper presents the results of studies of the phase transformation dynamics in composite xSi₃N₄ – (1-x)ZrO₂ ceramics obtained using the mechanical activation method during thermal annealing of the obtained mixtures of components with different component ratios, leading to the initialization of phase formation processes. Using the X-ray phase analysis method, the dynamics of phase transformations in xSi₃N₄ – (1-x)ZrO₂ ceramics, the general form of which can be written as ZrO₂/ZrSiO₄ → ZrSiO₄/finely dispersed fraction of SiO₂, was established. It was found that addition of Si₃N₄ to ZrO₂ ceramics allows for the initiation of polymorphic transformations of the m-ZrO₂ → t-ZrSiO₄ type, the formation of which in combination with the finely dispersed fraction of SiO₂ leads to hardening of the ceramics and an enhabcement in their resistance to external influences. During the experimental work carried out, aimed at study of the influence of the phase polymorphic transformation processes in composite ceramics, caused by a change in the ratio of components, on resistance to mechanical loads, it was established that the formation of a finely dispersed fraction of SiO₂ in the structure of ceramics increases resistance to cracking by more than 1.5 times compared to single-component ceramics, the stability of which decreases in the case of the compression rate growth.

Keywords: composite ceramics, phase transformations, dispersion hardening, nanosized grains, finely dispersed fraction.