Mirco-level Insight into the Surface Tension-structure Relationship of Molten CaO–MgO–SiO₂–Fe_xO–P₂O₅ Slags

Abstract

For comprehensive understanding and control of the properties of CaO–MgO–SiO₂–Fe_xO–P₂O₅ slags, thorough investigation of the surface tension-structure relationship is required. In this study, the structural behaviors of components were analyzed by Raman spectroscopy, and the transformation mechanism of surface tension as a function of composition was clarified. The results showed that with CaO/SiO₂ increasing from 0.5 to 2.0, O^2– resulted in the progressive breaking of bridging oxygen bonds in [SiO₄]- and [PO₄]-tetrahedrons, and Ca²⁺ contributed to the stabilization of [FeO₄]-tetrahedrons, thereby promoting the transformation from [FeO₆]-octahedrons to [FeO₄]-tetrahedrons. Although the network-forming ability of Fe³⁺ was enhanced, the overall non-bridging oxygen number still showed a gradual increase and thus the non-bridging oxygen bonds with higher unsatisfied energy in the surface layer led to an increase in surface tension. Nonetheless, the increasing P=O bonds effectively reduced surface tension due to its stable configuration in the range of CaO/SiO₂ = 0.5–1.0, diminishing the increasing magnitude of surface tension. Furthermore, a strong linear relationship between surface tension and the logarithm of structural parameters was found. On this basis, a surface tension estimation equation applied to the CaO–MgO–SiO₂–Fe_xO–P₂O₅-based system was established in terms of the deconvolution results of the melt structures.