Effect of BaO on the viscosity and structure of fluorine-free calcium silicate-based mold flux

The effect of BaO on the viscosity and structure of fluorine-free calcium silicate-based mold flux was studied using a rotary viscometer, molecular dynamics (MD) simulation, and Raman spectroscopy. The results demonstrated that the viscosity, activation energy, and break temperature of the samples decreased with the addition of BaO. The MD simulation revealed that the network breakers of BaO readily offered O2- to decrease the degree of polymerization of the network formers of SiO2 and Al2O3 in melts. The results of the Raman spectroscopy demonstrated that the complex network structure of [SiO3](2-) (chain) and [Si2O5](2-) (sheet) was depolymerized to the simple structure of [Si2O7](6-) (dimer) and [SiO4](4-) (monomer) with an increasing content of BaO. The results of the Raman spectroscopy were consistent with the MD simulation; thus, in conclusion, the complex network structure was depolymerized to the sample structure, resulting in a decrease in viscosity with the addition of BaO.