Basicity Contributions to Interfacial Structure and Oxygen Potential of CaO-MnO-SiO2 slag

In the field of chemical engineering, metallurgy and materials, the boundary layer is of great significance for element transport or removal. In the current work, the gas-slag interface has been investigated. The fresh interface between molten slag and reduction atmosphere has been obtained by gas-slag equilibrium technique. We used XPS etching technology and Raman spectroscopy to characterize the interfacial structure and bulk structure, respectively. First, the depth of the boundary layer is increasing with the decrease of the basicity, and in the boundary layer, the content of Ca is increasing while the amount of Si and O decreases. It is interesting to note that Mn is aggregated as Mn2+ at the bottom of the boundary layer (close to bulk slag). The elemental distribution of the z-axis based on ab initio molecular dynamics (AIMD) calculations also demonstrates the aggregation of manganese and sulfur elements at the gas-slag interface. Regardless of the basicity, the XPS results showed that the main form of oxygen changed from bridged oxygen (BO) to non-bridged oxygen (NBO) with increasing depth. However, with the same etching time, as the basicity increases, the proportion of BO is decreasing and that of NBO is increasing. Comparison of XPS results with Raman results shows that as the etching depth increases, the interfacial structure approaches the bulk structure, but when Ca/Si = 0.5, the structure at 360 seconds is still different from the bulk structure, indicating that the thickness of the boundary layer is thicker and the boundary layer of Ca/Si = 0.8 and 1 is thinner. By calculation, the interfacial oxygen potential at the gas-slag interface was determined to be of the order 10(-19) to 10(.)(-18) Interfacial structure and interfacial oxygen potential have a great influence on the boundary layer thickness. Therefore, the interface phenomenon has guiding significance for the metallurgical process.