Effect of basicity on density, surface tension and structure of CaO-SiO2-FexO molten slag

Combined with the pendant drop method and infrared and Raman spectroscopic detection, the effect of the basicity on the density and surface tension properties and the structure of CaO-SiO₂–10 % Fe_xO slag was investigated. With increasing basicity from 0.5 to 1, it is found that the density and surface tension values increase at the same temperature. Meanwhile, the complex structures of Si-O groups in the slag depolymerize, the area proportion of [FeO₆]^9- units decreases from 13.0 % to 8.3 % and that of [FeO₄]^5- units increases significantly from 2.9 % to 18.6 %. The key factor determining the area proportion and structural evolution of [FeO₆]^9- and [FeO₄]^5- units is the basicity rather than the relative contents of Fe²⁺ and Fe³⁺ ions. Overall, the slag polymerization degree depends on the structures of Si-O groups rather than on those of Fe-O groups, which leads to increases in the density and surface tension with increasing basicity.