The role of Ca and Na ions in the effect of F ion on silicate polymerization in molten silicate system

Abstract

For CaO-CaF2-SiO2 and CaO-CaF2-Na 2O-SiO2 systems, the effect of Na and Ca cation ions on the polymerization of silicate slags containing F ions and their structures are investigated by using molecular dynamics simulation. The substitution of F for O in the CaO-SiO2 melts enhances the polymerization of the melt due to the formation of loosely bonded Ca-2F complexes. The substitution of Na ions for Ca ions without changing the total number of F, O and Si ions in the CaO-CaF2-Na2O-SiO2 melts has a negligible effect on the distribution of silicate complex anions. For the CaO-CaF 2-Na2O-SiO2 system, the existence of the loosely bonded Ca-2F and Na-F complex are confirmed from the running coordination number variation. The relative amounts of the loosely bonded Ca-2F and Na-F complex in the CaO-CaF2-Na2O-SiO2 system are depended on Na/Ca ratio. It is found that the loosely bonded Ca-2F and Na-F complexes in the CaO-CaF2-Na2O-SiO2 melts are not randomly distributed but are clustered. © 2007 ISIJ.