Performance and transition mechanism from acidity to basicity of amphoteric oxides (Al2O3 and B2O3) in SiO2–CaO–Al2O3–B2O3 system: A molecular dynamics study

Amphoteric oxides (AlO and BO) represent opposite effects on the structure and properties of silicate melts in different conditions, while the understanding about the transition from acidity to basicity is far from complete. Molecular dynamics simulation was adopted in the present study to investigate the performance and acidity-basicity transformation of AlO and BO in the SiO–CaO–AlO–BO system. The results showed that, different from Ca ions, excessive Al or B ions tend to destroy the bridge oxygen structures, showing the function of basic oxide. This is similar to the behavior of Ca ions and other basicity ions. It was found that, on the one hand, B ions tend to form [BO] planar triangular structures with the increase of B ions contents, on the other hand, B ions could reduce the stability of Si–O bonds. Therefore, B ions could make the system structure less stable, which is the reason why the BO is a kind of active agent. In addition, because of the significant differences in lattice energy and atomic structure between AlO and BO, the effects of AlO and BO on the thermodynamic properties of silicate melts are quite different.