Coupled experimental and thermodynamic study of the Zn-Fe-Si-O system
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INTRODUCTION
THE present experimental study and thermodynamic modeling of the Zn-Fe-Si-O system is part of a wider research program described in previous publications by the present authors.[1–10] The overall research program combines experimental investigations with computer-aided thermodynamic modeling to develop a self-consistent thermodynamic database for the PbO-ZnO-SiO2-CaO-FeO-Fe2O3 system using the F*A*C*T computer package.[11] Phase relations, liquidus temperatures, proportions of liquid and solids, and many other slag properties including activities and partial pressures will be predicted over a wide range of compositions relevant to industrial zinc and lead smelting processes. In a thermodynamic “optimization” of a system, all available thermodynamic and phase-equilibrium data are evaluated simultaneously in order to obtain one set of model equations for the Gibbs energies of all phases as functions of temperature and composition. From these equations, all of the thermodynamic properties and the phase diagrams can be back-calculated. In this way, all the data are rendered self-consistent and consistent with thermodynamic principles. Thermodynamic property data, such as activity data, can aid in the evaluation of the phase diagram, and phasediagram measurements can be used to deduce thermodynamic properties. Discrepancies in the available data can often be resolved, and interpolations and extrapolations can be made in a thermodynamically correct manner. For the molten slag phase, a modified quasi-chemical model has been used.[12–15] The model has been described in several publications.[9,10,12–15] Parameters for the computer model of the slag system are obtained from thermodynamic and phaseequilibrium information on binary and ternary systems. Limited experimental information was found in the literature on the phase equilibria in the Zn-Fe-Si-O system. The EVGUENI JAK, Director Research, and PETER C. HAYES, Associate Professor/Director, are with PYROSEARCH (Pyrometallurgy Research Centre), Department of Mining, Minerals and Materials Engineering, The University of Queensland, St Lucia, Queensland, 4072 Australia. SERGEI DEGTEROV, Research Professor, and ARTHUR D. PELTON, Professor, are with the Centre for Research in Computational Thermochemistry, Ecole Polytechnique de Montreal, Montreal, PQ H3C 3A7, Canada. Manuscript submitted May 17, 2000. METALLURGICAL AND MATERIALS TRANSACTIONS B
liquidus in the ZnO-FeT O-SiO2 system under reducing conditions was studied by Dobrotsvetov et al.[16] using differential thermal analysis and by Umetsu et al.[17] using a quenching technique. Fayalite ((Fe,Zn)2SiO4) and willemite ((Zn,Fe)2SiO4) solid solubilities were investigated Umetsu et al.[17] using a quenching technique. The exact experimental techniques used by Dobrotsvetov et al.[16] for fayalite-willemite solid solubilities could not be clearly established from the article. In both studies,[16,17] samples were treated in a neutral atmosphere. No data were found in the literature for this system at high oxygen par
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