Viscosity of Iron Oxide Aluminosilicate Melts

A structure-based viscosity model has been developed for the CaO-MgO-FeO-SiO₂-Al₂O₃ system and its subsystems. A critical analysis of the experimental data for iron oxide aluminosilicate systems has been conducted and used in the optimization of a model, which provides a link between the viscosity and the structures of the melts. The structural characteristics of aluminosilicate melt can be described by four types of oxygen: bridging oxygen \( {\text{O}}_{i}^{0} \), non-bridging oxygen \( {\text{O}}_{j}^{ - } \), free oxygen O²⁻, and excess bridging oxygen O^*. The present model is capable of predicting the viscosities in the CaO-MgO-FeO-SiO₂-Al₂O₃ system and its subsystems over wide ranges of composition and temperature above the liquidus within experimental uncertainties, and the average of relative errors for this model was found to be 19.94 pct. This model includes FeO-SiO₂, CaO-SiO₂-FeO, Al₂O₃-SiO₂-FeO, MgO-SiO₂-FeO, CaO-SiO₂-MgO-FeO, CaO-SiO₂-Al₂O₃-FeO, and CaO-MgO-SiO₂-Al₂O₃-FeO. It was found that the effects of different metal cations on the viscosity can be determined, and the ability to reduce viscosity in the silicate melts follows the order: FeO > CaO > MgO. In the present model, the predicted viscosity decreased when CaO was initially initial added to the Al₂O₃-MgO-FeO-SiO₂ system at a fixed SiO₂ content because Ca²⁺ has the highest priority for charge compensation and FeO is the strongest modifier for this slag.