Thermodynamic assessment of ZnO-SiO2 system
(1. Thermodynamics and Modelling Research Group, Department of Materials Science and Engineering, School of Chemical Technology, Aalto University, P. O. Box 16200, FI-00076 Aalto, Finland;
2. Department of Materials Science, Royal Institute of Technology, Stockholm 11428, Sweden;
3. School of Metallurgy and Environment, Central South University, Changsha 410083, China)
2. Department of Materials Science, Royal Institute of Technology, Stockholm 11428, Sweden;
3. School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract: ZnO-containing slags are common in pyrometallurgical processing of the base metals and steel. This caused the interest to the thermodynamics of the ZnO-SiO2 system. A complete literature survey, critical evaluation of the available experimental data and a thermodynamic optimization of the phase equilibria and thermodynamic properties of the system ZnO-SiO2 at 1.013×105 Pa are presented. The molten oxide was described as an associate solution. The properties of liquid were reassessed and enthalpy term of the Gibbs energy of solid Zn2SiO4 was re-fitted to be compatible with the new data in the willemite primary phase field. The thermodynamic data set agrees well with the recent experimental observations. It can be used for predicting, e.g., the thermodynamic properties and the domains of the phase diagram, like critical point of the liquid miscibility gap, with a better accuracy than using the previous assessments. A set of optimized model parameters were obtained, reproducing the reliable thermodynamic and phase equilibrium data within their experimental errors from 298 K to liquidus temperatures, over the entire composition range. The created database can be used in a Gibbs energy minimization software to calculate the thermodynamic properties and the phase diagram sections of interest.
Key words: thermodynamic assessment; ZnO-SiO2 system; thermodynamic properties; phase diagram