Effect of B2O3 Addition and CaO/Al2O3 Ratios on Melt Structure and Viscosity of CaO–Al2O3-Based Slags

The effect of the addition of B2O3 and the CaO/Al2O3 ratios on the CaO–Al2O3–B2O3 melts’ structure was fully analyzed by molecular dynamics (MD) simulations. The results show that, with the increase in CaO/Al2O3 ratios, the charge compensation for [AlO4]5− tetrahedron changed from the oxygen tricluster structure to the charge provided by Ca2+, and the structure of [AlO4]5− tetrahedron was stabilized. The addition of B2O3 reduced the degree of polymerization of the aluminate melt, which, in turn, lowered the melt viscosity; in the systems with CaO/Al2O3 mole ratio less than 1, the added B2O3 mainly existed in the form of [BO3]3−, which reduced the symmetry and the strength of the melt network structures; in the higher CaO/Al2O3 ratio systems, the depolymerization ability of the addition of B2O3 on aluminate network structures was enhanced with the increase in CaO/Al2O3 ratios, and the overall degree of polymerization of the melt decreased. The viscosity measurement shows that B2O3 lowers the viscosity of CaO–Al2O3 melts, which was consistent with the results predicted by MD simulations.