Structure investigation of CaO-SiO2-Al2O3-Li2O by molecular dynamics simulation and Raman spectroscopy

As a common flux, Li2O plays an important role in improving the physical and chemical properties of metallurgical slag. A variation of structural units and action mechanisms of Li in a CaO-SiO2-Al2O3-Li2O slag system is investigated using molecular dynamics (MD) simulation and Raman spectroscopy. We studied five glass compositions where the Li2O concentration varied from 0 to 16 mol%. Molecular dynamics simulation results show that Li2O plays the role of depolymerizing the microstructure of the melt. The Li+ takes precedence over Ca2+ to compensate for the excess negative charge in the [AlO4](5-) tetrahedral structure. The bond angles vary regularly with increasing Li2O content. Raman spectroscopy results show that the increase of Li2O promotes the transformation of Al-O-Si structural units to Al-O-Al structural units, which confirms that Li+ can better balance the charge of [AlO4](5-) structure in slag. Therefore, Li also plays a role in stabilizing the [AlO4](5-) tetrahedral structures.