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

PF Xu and ZY Kang and WK Gao and L Liu and LL Zhang and Y Cao and J Li and JB Si and SF Shen and JF Kang, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 109, e70409 (2025).

DOI: 10.1111/jace.70409

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-Al2O3-SiO2 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 Mg2+ compared to Ca2+, the formation of high coordinated aluminium (AlO5) and tri- coordinated oxygen (O3) is promoted with the replacement of CaO by MgO. This process strengthens the glass network by converting bridging oxygen (O2) into a combination of O3 and non-bridging oxygen (O1). Furthermore, the distribution of O3 among the five oxygen atoms within AlO5 was examined. The AlO5 unit containing two O3 is the most possible form of existence. Most importantly, a strong linear correlation (R-2 = 0.93) was identified between the concentration of AlO5 and Young's modulus, establishing AlO5 as a key structural descriptor for stiffness in these glasses.

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