Effects of equimolar substitution of BaO for CaO and Al2O3 for SiO2 on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO slag

This study investigated the effects of equimolar substitution of BaO for CaO and Al2O3 for SiO2 on the viscosity and structure of CaO-SiO2-MgO-Al2O3-BaO slag. In slags containing 2 mol.% Al2O3, introducing BaO disrupted the bridging oxygen bonds, leading to an increase in non-bridging oxygen and the depolymerization of the tetrahedral structure. Consequently, viscosity decreased with increased BaO substitution. However, for slags with 5 mol.% Al2O3, the synergistic effects of preferential charge compensation by Ba2+ for Al3+ and structural depolymerization by BaO led to the initial stabilization of tetrahedral structures, followed by destabilization. This resulted in the viscosity first increasing and then decreasing with higher BaO substitution levels. With the gradual replacement of SiO2 by Al2O3, a significant increase in [AlO4] tetrahedra relative to the decrease in [SiO4] tetrahedra could be observed. Concurrently, a reduction in free oxygen and non-bridging oxygen content was observed, ultimately leading to an increase in viscosity.