Development of the properties of magnesia alumina spinel-based refractory composites with modifying oxides

The present study investigates the synthesis of MgAl 2 O 4 spinel via one-step sintering, producing a reference sample without additives and four additional samples containing 5 wt% ZrO 2 , Fe 2 O 3 , SiO 2 , or TiO 2 , respectively.The MA sample along with the four types of modified spinel-based composites [MA_5T, MA_5Z, MA_5F, MA_5S] were characterized in terms of their phase composition, microstructure, bulk and true densities, as well as open and true porosities of the sintered materials.High-temperature microscopy was employed to evaluate dimensional changes of the samples during their heat treatment process.The presence of phases and the firing behavior of the resulting composite materials were evaluated using thermodynamic simulation (FactSage 8.3).The study demonstrated that the incorporation of specific oxide additives significantly influences the synthesis and properties of MgAlO spinel.Iron (Fe) and titanium (Ti) ions were found to induce structural modifications within the spinel lattice, suggesting partial substitution or incorporation into the crystal framework.XRD analysis showed that the addition of the SiO modifier leads to the formation of MgSiO, which can partially dissolve into the spinel phase, while ZrO promoted the extraction of Al ions from the spinel structure, as corroborated by the thermochemical simulations using FactSage.The highest microstructural densification was achieved in the samples with TiO and SiO, indicating their positive role in enhancing sintering efficiency.Conversely, the addition of FeO did not significantly affect the densification behavior, despite the formation of an Fe-rich spinel phase.