Integrated phase equilibria experimental study and thermodynamic modeling of the Cr–Si–O, Fe–Cr–O and Fe–Cr–Si–O systems

Abstract

Complete characterization of the Fe–Cr–Si–O system at high temperatures (700–2600 °C) is performed using integrated experimental and thermodynamic modeling research methodology. Experimental technique includes high-temperature equilibration, quenching and electron probe X-ray microanalysis (EPMA). Main challenges in the experiments are the choice of holding materials (substrate), fixing the oxygen partial pressure in a wide range, using the secondary standards for EPMA correction, overcoming slow reactions to achieve solid state equilibria. Thermodynamic modeling involves critical assessment of literature data, development of the mathematical models for the Gibbs energies of all phases in the system, and optimization of model parameters. The main modeling challenge is to obtain a self-consistent database, which requires a re-assessment of the Cr–Si–O and Fe–Cr–O sub-systems, and an accurate simultaneous description of all experimental data from literature and from the present study. There are several outcomes of the present study: a critical review of earlier work; a set of diagrams representing phase equilibria and distribution of elements among phases within the system; a set of thermodynamic model parameters for liquid and solid phases in the system. The results of the work will be applied to solve chemical engineering problems in pyrometallurgical production of copper, nickel and steel, recycling of waste electronics and designing refractory materials.