Micro insight into foaming behavior of CaO-SiO2-FexO-MgO-based slag induced by slag/metal reaction

Understanding the micro mechanism of foaming behavior is urgently required for regulating metallurgical processes and preparing porous ceramics. In this study, we performed high-temperature simulation experiments on the foaming of CaO-SiO2-FexO-MgO-based slag induced by a slag/metal reaction. The evolution of the melt structure with changes in the chemical composition of the molten slag was analyzed using Raman spectroscopy. The micro mechanism of slag foaming was interpreted using the melt structure characteristics. As the w(CaO)/w (SiO2) and P2O5 content varied, the maximum foaming height exhibited a positive relationship with the degree of polymerization of the experimental slag. In the bulk phase of the liquid film, an increase in the degree of polymerization of the experimental slag hindered the drainage of slag from the liquid film and reduced the solubility of the liquid film for CO gas in the bubble, leading to an increase in the maximum foaming height of the molten slag. Moreover, the increase in the degree of polymerization of the structural units at the liquid film/CO interface improved the elasticity of the liquid film and decreased the permeability of the liquid film for CO in the bubble, resulting in an increase in the maximum foaming height of the molten slag. The new perspective of ''chemical composition-melt structure-slag foaming'' also inspired studies on industrial processes that readily form foam, including glass manufacturing, oil recovery, and froth flotation.