Viscous behavior of high-Fe_tO-bearing slag systems in relation to their polymeric structural units

The effect of basicity (CaO/SiO₂ mass ratio) and Fe_tO on the viscous behavior of CaO–SiO₂–FeO–Al₂O₃–MgO–MnO slag was investigated via stepped-temperature viscometry (1873–1473 K) to predict the thermophysical properties of high-Fe_tO-bearing molten slag. The basicity and Fe_tO contents were varied to determine the constitutional effect of the slags on the physical properties and ionic structure. At low Fe_tO contents (below 15 wt%), the viscosity of high-Fe_tO-bearing slags exhibited a strong dependence on basicity. However, at high Fe_tO contents (above 15 wt%), the viscosity decreased as the Fe_tO content increased, indicating a strong Fe_tO dependency. This behavior was attributed to the change in activation energy as the dominant polymeric structural unit (T–O–T; T = Si, Al, and Fe) varied depending on the equilibrated primary phase. In addition, to understand the change in the dominant polymeric structural unit depending on the Fe_tO content, the relationship between the polymeric structural units and thermophysical properties of high-Fe_tO-bearing slags was studied by analyzing the Fe³⁺/Fe²⁺ and nonbridging oxygen fractions of the slag melts.