Effect of CaF2 Addition on the Viscosity and Structure of CaO-SiO2MnO Slags

The viscosity of the CaO-SiO2-MnO(-CaF2) slags (CaO/SiO2 = 1.0, MnO = 10, 40 mass%) was measured to clarify the effect of CaF2 on the viscous flow of molten slags at high temperatures. Furthermore, the Raman spectra of the quenched glass samples were quantitatively analyzed to investigate the structural role of CaF2 in a depolymerization of silicate networks. The critical temperature of the slags abruptly increased at 15 mass% CaF2, which was confirmed to originate from a crystallization of cuspidine using XRD analysis. The viscosity of the slags continuously decreased by CaF2 addition in the 10 mass% MnO system, whereas the viscosity of the 40 mass% MnO system was not significantly affected by CaF2 addition. The activation energy for the viscous flow of silicate melts decreased by CaF2 addition and its tendency became less significant in the more basic composition, i.e. in the 40 mass% MnO system. The effect of CaF2 on the viscosity of the slags was quantitatively analyzed using micro-Raman spectra of quenched glass samples accompanying with a concept of silicate polymerization index, Q(3)/Q(2) ratio. A polymerization index continuously decreased with increasing content of CaF2 in the 10 mass% MnO system, whereas it was not affected by CaF2 in the 40 mass% MnO system. Consequently, the bulk thermophysical property of the CaO-SiO2-MnO-CaF2 slags was quantitatively correlated to the structural information.