The Role of Ca and Na Ions in the Effect of F Ion on Silicate Polymerization in Molten Silicate System

For CaO–CaF2–SiO2 and CaO–CaF2–Na2O–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–CaF2–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.