Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn $$_{2}$$
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INTRODUCTION
THE iron-manganese silicate has been of particular interest in steel industries. Reduction of ores in blast furnace results in forming silicate slags in which iron and manganese oxides dissolve. Deoxidation of liquid steel with FeSi alloy or MnSi alloy results in oxide inclusions in steel.[1,2] Understanding surface/internal oxidation of steel slab during reheating process requires thermodynamics of the iron-manganese silicate.[3,4] Therefore, knowledge of thermodynamics and phase equilibria on Fe-Mn-Si oxide systems should give valuable information in practical operation. In theoretical view, this system is also interesting to model, because Fe and Mn are both transition metals: stability of Fe-Mn oxides is sensitive to oxygen partial pressure exerted on the oxides. Therefore, it is required to understand thermodynamics and phase equilibria in this system, and thermodynamic modeling and database construction of this system should be very useful.
YOUN-BAE KANG is with the Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea. Contact e-mail: [email protected] IN-HO JUNG is with the Department of Mining and Materials Engineering, McGill University Montreal, Montreal, QC, H3A 2B2, Canada. Manuscript submitted September 18, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
Such thermodynamic database can be prepared by critical evaluation, thermodynamic modeling, and optimization. In a thermodynamic ‘‘optimization,’’ adjustable Gibbs energy model parameters are optimized in order to reproduce all available and reliable thermodynamic and phase equilibrium data. This gives one set of model equations as functions of temperature, pressure, and composition. Thermodynamic data, such as activities, can aid in the evaluation of the phase diagrams, and information on phase equilibria can be used to deduce thermodynamic properties. Thus, it is frequently possible to resolve discrepancies in the available data. From the model equations, all of the thermodynamic properties and phase diagrams can be back-calculated, and interpolations and extrapolations can be made in a thermodynamically correct manner. The data are, thereby, rendered self-consistent and compliant with thermodynamic principles, and the available data are distilled into a small set of model parameters, which is ideal for computer storage. Thermodynamic evaluations and optimizations for several sub-systems of the FeO-Fe2 O3 -MnO-Mn2 O3 -SiO2 system were previously carried out for the Fe-O system,[5] the Mn-O system,[6] the Fe-Mn-O system,[7–9] the FeO-Fe2 O3 -SiO2 system,[10] MnO-SiO2 system,[11] respectively. All these work employed the modified quasichemical model (MQM) in the pair approximation[12–14] in order to model liquid oxide. These previous works were taken in the present study directly without
any modification. The present study is a part of a complete database development of the Al2 O3 -CaOFeO-Fe2 O3 -MgO-MnO-Mn2 O3 -SiO2 systems for applications in the ferrous, non-ferrou
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