Abstract:
The aim of this study is to determine the effect of changes in the phase composition of
Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding
on their resistance to the process of long-term thermal exposure, accompanied by the processes of
oxidation and softening. The relevance of this research consists of determining the influence of
the phase composition of ceramics on the change in their strength and thermophysical parameters,
on the basis of which, we can draw a conclusion about the optimal composition of composite
ceramics that have great prospects in the field of fire-resistant, heat-resistant, or radiation-resistant
structural materials. During this study, the dynamics of the changes in the phase transformations
of the xAl2O3–(1−x)Si3N4 ceramics, with variations in the ratio of the components, initiated by
the thermal annealing of the samples, was established. According to the assessment of the phase
transformations with variations in the ratio of the components, it was found that thermal annealing
in an air environment at an Al2O3 concentration in the order of 0.3–0.5 M leads to the formation of an
orthorhombic Al2
(SiO4
)O phase and an elevation in its contribution at concentrations above 0.5 M,
which causes a rise in the thermophysical parameters and resistance to high-temperature degradation.
During the heat resistance tests, it was found that the formation of the composite ceramics with
the Si3N4
(SiO2
)/Al2
(SiO4
)O/Al2O3 phase composition results in an increase in the stability of their
strength properties when exposed to thermally induced oxidation, which has a negative impact on
their resistance to softening and a decrease in hardness. Moreover, the presence of the Al2
(SiO4
)O
phase in the composition of the ceramics causes a slowdown in the processes of thermal oxidation of
the Si3N4 phase under prolonged temperature exposure, alongside an increase in the degradation
resistance of strength properties by more than 4–7 times, in comparison with the softening data
established for single-component ceramics.
