The Fe-Zn-O phase diagram in air was studied over the temperature range from 900 ЊC to 1500 ЊC. The compositions of the phases in quenched samples were obtained by electron probe X-ray microanalysis (EPMA). This experimental technique is not affected by zinc losses resulting from vaporization of zinc at high temperatures. The model for the spinel solid solution was developed within the framework of the compound-energy formalism (CEF). The choice of parameters of the CEF and the sequence of their optimization can have a major influence on the predictions in multicomponent phases. These choices can only be made rationally by reference to the specific model being represented in the CEF. This is discussed for the case of the two-sublattice spinel model. In the limiting case, the proposed model reduces to the model by O'Neill and Navrotsky for spinels. When the CEF is used in combination with the equation of Hillert and Jarl to describe the magnetic contribution to thermodynamic functions of a solution, it is necessary to assign certain values of magnetic properties to all pseudocomponents and to magnetic interaction parameters to obtain the most reasonable approximation of the magnetic properties of a solution. It was shown how this can be done based on very limited experimental data. The same equations can be used when the Murnaghan or the Birch-Murnaghan equation is combined with the CEF to describe the pressure dependence of thermodynamic functions. The polynomial model was used to describe the properties of wustite and zincite, and the modified quasichemical model was used for the liquid slag. All thermodynamic and phase-equilibria data on the Fe-O and Fe-Zn-O systems were critically evaluated, and parameters of the models were optimized to give a selfconsistent set of thermodynamic functions of the phases in these systems. All experimental data are reproduced within experimental error limits. These include the thermodynamic properties of phases (such as specific heat, heat content, entropy, enthalpy, and Gibbs energy); the cation distribution between octahedral and tetrahedral sites in spinel; the oxygen partial pressure over single-phase, twophase, and three-phase regions; the phase boundaries (liquidus, solidus, and subsolidus); and the tie-lines.

Ferrous calcium silicate slags are used in primary and secondary metallurgical processes (described by the FeO-Fe 2 O 3 -CaO-SiO 2 system). Despite the industrial and scientific importance of this system, the phase equilibria have not been fully investigated. Characterization of this slag system is necessary to improve the design and optimization of new and existing metallurgical processes, particularly in relation to fluxing practice and operating temperatures. Experimental methods have been developed to investigate the phase equilibria of these slags involving the equilibration of samples at fixed oxygen partial pressures, rapid quenching, and the analysis of the compositions of solid and liquid phases using electron probe X-ray microanalysis (EPMA) with wavelength dispersive detectors. Liquidus and solidus data are reported for the primary phase fields of spinel, pseudo-wollastonite, and tridymite in the temperature range of 1200°C to 1350°C at an oxygen partial pressure of 10 -6 atm, and at 1250°C at an oxygen partial pressure of 10 -5 atm. The resulting data have been used to construct liquidus and solidus isotherms in the ''FeO''-CaO-SiO 2 system directly relevant to industrial processes.

No abstract

A general model based on the Urbain formalism has been developed, which enables the viscosities of liquid slags to be predicted for all compositions in the Al 2 O 3 -CaO-'FeO'-SiO 2 system in equilibrium with metallic iron. Available experimental viscosity data have been analyzed and critically reviewed. The Urbain formalism has been modified to include compositional dependent model parameters. Experimental data in unaries, binaries, ternaries, and the quaternary system have been described by the model over the whole compositional and temperature ranges using one set of model parameters. This viscosity model can now be applied to various industrial slag systems.

No abstract

No abstract

Liquidus-phase equilibrium data of the present authors for the PbO-ZnO-SiO 2 system, combined with phase equilibrium and thermodynamic data from the literature, were optimized to obtain a selfconsistent set of parameters of thermodynamic models for all phases. The modified quasichemical model was used for the liquid slag phase. From these model parameters, the optimized ternary-phase diagram was back-calculated.

No abstract