Critical evaluation and thermodynamic modeling of phase equilibria in multicomponent oxide systems

The prediction of thermodynamic properties and phase equilibria related to liquid and solid oxides can play an important role in the development and understanding of metallurgical, ceramic and geological processes. The importance of numerical simulation of these processes is increasing, and the thermodynamic models must keep pace and be able to calculate and predict phase equilibria and thermodynamic properties of complex mixtures. The goal of this thesis is a critical evaluation and optimization of thermodynamic properties of solid and liquid oxides in order to construct accurate and extensive thermodynamic databases for the systems of industrial interest. The constructed databases can aid in understanding various industrial processes more clearly and in developing new technology in various industries.; All solid and liquid phases of 5 binary, 9 ternary and 5 multicomponent sub-systems in the CaO-MgO-Al2O3-SiO2-FeO-Fe 2O3-MnO-CrO-Cr2O3-CoO system were critically evaluated and optimized in the course of the present study. The optimization of all systems in this study are self-consistent, and moreover are consistent with all alloy and salt databases of the FACT system (developed at Ecole Polytechnique de Montreal). From the database of model parameters of lower order (binary + ternary) subsystems, the thermodynamic properties of multicomponent solutions can be predicted with good accuracy.; All thermodynamic models for solutions used in this study were developed on the basis of their structure. In this way, the configurational entropy of solution could be properly taken into account. Thus, the number of model parameters for each solution can be minimized using physically correct thermodynamic models. The predictive ability of all models was found to be excellent.; The molten oxide was modeled by the Modified Quasichemical Model, which takes into account second-nearest-neighbor cation ordering. Extensive solid solutions such as spinel, olivine and pyroxene were modeled within the framework of the Compound Energy Formalism with consideration of their two- or three-sublattice crystal structure. Other solid solutions such as monoxide, wollastonite and so on were modeled using polynomial expansions of the excess Gibbs energy. Deoxidation equilibria in liquid Fe were also modeled using a new Associate Model developed in the present study, which takes into account the strong affinity of deoxidants to oxygen. (Abstract shortened by UMI.)...