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The efficient recycling of vanadium from converter vanadium-bearing slag is highly significant for sustainable development and circular economy. The key to developing novel processes and improving traditional routes lies in the thermodynamic data. In this study, the equilibrium phase relations for the Fe2O3-TiO2-V2O5 system at 1200°C in air were investigated using a high-temperature equilibrium-quenching technique, followed by analysis using scanning electron microscopy-energy dispersive X-ray spectrometer and X-ray photoelectron spectroscopy. One liquid-phase region, two two-phase regions (liquid-rutile and liquid-ferropseudobrookite), and one three-phase region (liquid-rutile-ferropseudobrookite) were determined. The variation in the TiO2 and V2O5 contents with the Fe2O3 content was examined for rutile and ferropseudobrookite solid solutions. However, on further comparison with the predictions of FactSage 8.1, significant discrepancies were identified, highlighting that greater attention must be paid to updating the current thermodynamic database related to vanadium-bearing slag systems. [ABSTRACT FROM AUTHOR]

The recovery of rare-earth elements (REEs) from rare-earth blast furnace slag (RE-BFS) is crucial for advancing the circular economy. However, the development of related processes is significantly hindered by the severe lack of fundamental thermodynamic data on REE systems, underscoring the urgent need for detailed studies in this area. In the present work, the equilibrium phase relations of CaO-SiO2-CeO2-10.0 wt.% Al2O3-5.0 wt.% MgO system at 1300°C and 1400°C were experimentally carried out using the high-temperature equilibration-quenching technique followed by X-ray diffraction (XRD), scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray photoelectron spectroscopy (XPS), as well as thermodynamic calculation. One liquidus region, a liquid–CeO2 two-phase coexisting region, and a liquid–CeO2–akermanite three-phase coexisting region were confirmed within the investigated composition ranges. Based on the experimental data and phase compositions, the phase diagram of the CaO-SiO2-CeO2-10.0 wt.% Al2O3-5.0 wt.% MgO system was constructed at 1300°C and 1400°C. There were great discrepancies between the experimental results and calculated results by FactSage 8.2. The phase equilibria data obtained from this study provide fundamental thermodynamic information for the development of innovative processes aimed at extracting REEs from RE-BFS, as well as enriching the existing REEs database. [ABSTRACT FROM AUTHOR]

The spinel and pseudobrookite type ceramic materials have been widely used in different industries including ceramics, refractory and metallurgy. Therefore, their physicochemical properties are important for the development of related processes. In this regard, it is important to understand the formation principles of the spinel and pseudobrookite solid solutions. In the present work, the equilibrium phase relations for the MgO-Al2O3-TiO2 system at 1700°C in air were experimentally determined by high-temperature equilibration-quenching technique followed by XRD and SEM–EDS analyses. The pseudobrookite solid solution was found to be coexisting with spinel solid solution and rutile phase, respectively. The composition evolution and formation principles of the pseudobrookite and spinel solid solutions were further elucidated from the corresponding crystal structures and composition relations. Furthermore, great discrepancies were observed when the 1700°C isotherm from the present work was compared with the isotherm simulated by FactSage 8.1. The evolution of the solid solution existing area was intuitively presented with reference to the experimental data from the literature. The results from present work are important for the development of spinel and pseudobrookite solid solution ceramics as well as the optimization of the thermodynamic database for oxide systems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A long-term fundamental study for the construction of the thermodynamic database of a metallurgical slag system has been proposed. In the present work, the equilibrium phase relations for the key ternary SiO2-Al2O3-FeOx system at 1300 °C and 1400 °C in air were experimentally determined by the equilibrium-quenching technique, followed by X-ray Photoelectron Spectroscopy and Scanning Electron Microscope equipped with an Energy Dispersive X-ray Spectrometer analysis. The oxidation states of Fe2O3 and Fe3O4 were confirmed at 1300 °C and 1400 °C, respectively, from both XPS detection and FactSage calculation. Within the high-SiO2 composition range, the solid phases of silica, mullite, magnetite and ferric oxide were confirmed as the equilibrium phases. Based on the equilibrium compositions, the 1300 °C and 1400 °C isotherms were projected onto a SiO2-Al2O3-FeOx quasi-ternary phase diagram; however, obvious discrepancies with about a 20 °C difference were confirmed from further comparison with the predictions given by FactSage, indicating that more efforts are needed for the updating of the current thermodynamic database relating to metallurgical slag oxide systems. [ABSTRACT FROM AUTHOR]

The phase relations of TiOx containing systems in reducing atmospheres are extremely important for understanding the smelting process for vanadium titano-magnetite. In the present work, the equilibrium phase relations for the core CaO-SiO2-Ti3O5 system at 1400 °C and oxygen partial pressure of 10−16 atm were determined. Ti3O5 was confirmed as the stable Ti oxide in CO(g)-C equilibrium, and the solid phases Ti3O5, 3CaO·Ti3O5, SiO2, and CaO·SiO2 were found to coexist with the liquid oxide within the composition range investigated. The 1400 °C isothermal phase diagram of the CaO-SiO2-Ti3O5 system was constructed to demonstrate the areas of single liquid, as well as the two-phase and three-phase domains. Furthermore, a comparison with results in the literature indicated that the single liquid domain at 1400 °C greatly shrinks when the oxygen partial pressure decreases from air to 10−16 atm, and the corresponding liquid coexisting phases of TiO2 and CaO·TiO2 transform to Ti3O5 and 3CaO·Ti3O5. [ABSTRACT FROM AUTHOR]

The continuous basalt fibers have been regarded as one of the most promising green materials in modern society; however, key thermodynamic equilibrium data are insufficient for a better understanding of the crystallization mechanism during the fiber forming process. In the present study, the equilibrium phase relations of the core SiO 2 -Al 2 O 3 -FeO x subsystem with fixed 10 wt % CaO were experimentally determined using the classic equilibrium-quenching technique with the scanning electron microscopy-energy-dispersive X-ray spectroscopy analysis. All samples were presented as liquid-silica coexisting within the basalt composition range. The 1300 and 1400 °C isotherms were constructed based on the experimental results. However, significant discrepancies were confirmed with further comparison of the experimental results with FactSage predictions, indicating that more efforts are needed for the optimization of the basalt oxide-related thermodynamic databases., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)