Effect of MgO/CaO on structure and Young's modulus of CMAS glasses: Experiments and molecular dynamics simulations

Abstract The development of high‐performance glass fibers for applications such as wind turbine blades demands materials with superior mechanical properties, particularly a high Young's modulus. To this end, the structure and Young's modulus of CaO‒MgO‒Al 2 O 3 ‒SiO 2 glasses with varying MgO/CaO ratios were investigated by experiments and molecular dynamics simulations in this study. It was observed that as the MgO/CaO ratio increased, the density of the glass samples gradually decreased, while the Young's modulus significantly increased. The trends of structural and performance changes derived from MD simulations were found to be in good agreement with experiments, revealing the underlying structural origin. Owing to the weaker charge‐balancing capacity of Mg 2+ compared to Ca 2+ , the formation of high coordinated aluminium ([AlO 5 ]) and tri‐coordinated oxygen (O[3]) is promoted with the replacement of CaO by MgO. This process strengthens the glass network by converting bridging oxygen (O[2]) into a combination of O[3] and non‐bridging oxygen (O[1]). Furthermore, the distribution of O[3] among the five oxygen atoms within [AlO 5 ] was examined. The [AlO 5 ] unit containing two O[3] is the most possible form of existence. Most importantly, a strong linear correlation ( R 2 = 0.93) was identified between the concentration of [AlO 5 ] and Young's modulus, establishing [AlO 5 ] as a key structural descriptor for stiffness in these glasses.