Effect of (BaO+CaO)/Al2O3 ratio (1.7∼2.0) on the structure and Al-Li association of BaO-CaO-Al2O3-CaF2-Li2O mold flux

Al2O3 possess properties of amphoteric oxide, so it plays different network roles in the traditional CaO-Al2O3- based melts, while, its influence mechanism in atomic scale has not yet been fully understood. Molecular dynamics (MD) simulation and MAS NMR Spectrum was conducted to gain a clear understanding about the variation of network structure and Al-Li association on the non-reactive melts structure in different (BaO+CaO)/Al2O3 ratio and temperature. The results show that [AlO4]- tetrahedra serves as the network framework of BaOCaO-Al(2)O3-CaF2-Li2O non-reactive melt, and forms the chain and layered spatial network. As the (BaO+CaO)/Al2O3 ratio decreases from 2.0 to 1.7, Al2O3 converts to alkaline first and then to acidic, and the polymerization degree and viscosity of melt increase first and then decrease. In addition, the strength of Al-Li association decreases with the increase of (BaO+CaO)/Al2O3 ratio and temperature, which is conducive to the hop of Li+ between non-bridging oxygen sites and increases the diffusion rate of Li+ in the spatial network.

Automated summary

This study used molecular dynamics simulation and MAS NMR spectrum to investigate the non-reactive melt structure at different (BaO+CaO)/Al2O3 ratios and temperatures. The results revealed that [AlO4]- tetrahedra serve as the network framework, forming chain and layered spatial networks. Additionally, the alkalinity and acidity of Al2O3 change with the ratio, affecting the polymerization degree and viscosity of the melt.