Structural and dynamic properties of MgO-Al2O3-SiO2 glasses from molecular dynamics simulations and NMR

Magnesium aluminosilicate glasses have a wide range of applications in composite fiber reinforcements, aircraft windshields, due to their excellent chemical stability and mechanical properties. In this work, molecular dynamics simulations were used to obtain the short-and medium-range structural evolution of MgO/Al2O3 in MgO-Al2O3-SiO2 glass. The structural information was verified using a combination of combining Raman and Nuclear Magnetic Resonance (NMR) spectroscopy. The composition-structure-property relationship of the MgO-Al2O3-SiO2 glasses was constructed, using high-temperature viscosity results calculated by the Einstein Stoke equation. The results showed that with the increase of MgO/Al(2)O(3)ratio, Mg2+ changed from charge compensator to network modifier, which led to the gradual depolymerization of the glass network. Moreover, with the gradual replacement of Si by Al in the glass network, the disorder of the glass system increases, evidenced by the high-frequency Raman bands and the average chemical shifts of [AlOn] (n = 4, 5) shift linearly. In addition, we found that the de-polymerization led to a decrease in viscosity and an increase in fragility. The viscosity is negatively correlated with both the fragility and the atomic diffusion coefficient. It provides a theoretical basis for improving the preparation process of MgO-Al2O3-SiO2 glass and optimizing the glass properties.