Phase equilibria of MgO–Al₂O₃–TiO₂ system at 1600°C in air: Emphasis on pseudobrookite and spinel solid solution phases

Abstract

The recycling of titanium from titania‐bearing slag is an important part of the circular economy; however, the yield of titania is restricted due to the lack of fundamental thermodynamic data. In the present work, the equilibrium phase relations of MgO–Al2O3–TiO2 system in air at 1600°C have been determined using a high‐temperature equilibration‐quenching technique followed by X‐ray photoelectron spectroscopy, scanning electron microscopy‐energy‐dispersive X‐ray spectrometry, and X‐ray diffraction. Ti4+ was confirmed as the stable valence of titanium, and the rutile and spinel solid solution phases were detected to be coexisting with pseudobrookite solid solution phase, respectively. The formation principles of pseudobrookite and spinel solid solutions were confirmed in view of the corresponding crystal structure and the composition substitution relationship of the oxides at 1600°C. However, great discrepancies were found from the comparison of the present experimental results with the thermodynamic calculations and the literature results, and the present equilibrium phase relations are therefore significant for updating the present titania related thermodynamic database for a superior prediction of the thermodynamic behaviors of relevant process.

Study on High‐Temperature Reactions of MgO Refractory with Ti‐Bearing Al‐Killed Steel

“…It was reported that when the Ti content in steel is sufficiently high (e.g., w(Ti) > 0.1%), and/or the oxygen partial pressure is sufficiently low, Ti primarily exists in the form of Ti 2 O 3 . [28,29] In this study, due to the low oxygen potential, the oxide of TiO x in the reacted layer is treated as Ti 2 O 3 during the composition calculations of EDS results. In fact, this treatment cannot change the variation trend of the TiO x in the layers, and the valence of the Ti ions in the oxide may still need further confirmation.…”