Experimental study of phase equilibria in the systems Fe-Zn-O and Fe-Zn-Si-O at metallic iron saturation
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I. INTRODUCTION
THE overall research program combines experimental investigations with computer-aided thermodynamic modeling to develop a self-consistent thermodynamic database. The database is a part of the computer system FACT,[1] which will be used to predict phase relations and other thermodynamic properties in the six-component system PbO-ZnO-SiO2-CaO-FeO-Fe2O3 over a wide range of compositions for zinc/lead industrial smelting processes. Some other subsystems studied within this overall research program have already been described in previous publications by the present authors.[2–13] The experimental work on the systems Fe-Zn-O and Fe-Zn-Si-O in equilibrium with metallic iron is part of this wider research program. Only a limited number of experimental measurements were found in the literature on phase equilibria in the systems Fe-Zn-O and Fe-Zn-Si-O in equilibrium with metallic iron. Claude et al.[14] studied wustite in equilibrium with iron and zincite at 900 8C (1173 K). The solubilities of ZnO and FeO in the wustite and zincite, respectively, for temperatures between 827 8C and 1000 8C (1100 and 1273 K) were reported by Itoh et al.[15, 16, 17] and Lykasov et al.[18, 19, 20] Electromotive force measurements of the equilibrium oxygen partial pressures over single-phase wustite and twophase regions, (wustite 1 zincite) and (wustite 1 iron), were performed by Lykasov et al. at 850 8C to 1000 8C (1123 to 1273 K). These authors also measured the oxygen potentials for the univariant equilibria, (Fe 1 wustite 1 zincite) and (spinel 1 wustite 1 zincite).[19] Itoh et al.[15, 16, 17] reported the oxygen partial pressures for all the two- and three-phase fields at 827 8C (1100K). Lykasov et al.[18, 19, 20] suggested that their powder X-ray diffraction results indicated the phase EVGUENI JAK, Senior Research Fellow, BAOJUN ZHAO, Postdoctoral Research Fellow, and PETER C. HAYES, Associate Professor, are with the Department of Mining, Minerals and Materials Engineering, The University of Queensland, St Lucia, Queensland, 4072, Australia. Manuscript submitted October 28, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS B
separation of wustite into two phases. This has not, however, been observed in any other studies. The liquidus in the system ZnO-FeOx-SiO2 was studied by Dobrotsvetov et al.[21] using a differential thermal analysis (DTA). The application of DTA to the liquidus measurements in a silicate slag system[21] introduces uncertainties associated with slow crystallization and with changing bulk composition due to the slag/crucible interaction. Umetsu et al.[22] investigated this system using the quenching technique. In this study, master slags were initially prepared in contact with metallic iron: the samples, however, were finally equilibrated in a neutral atmosphere. Continuous contact with metallic iron was not maintained during the entire experiment in the preceding study.[22] Itoh et al.[16, 17] reported an isothermal section at 827 8C (1100 K) for the system “FeO”-ZnO-SiO2 in equilibrium with metallic iro
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