Structure and Crystallization of High-Calcium, CMAS Glass Ceramics Synthesized with a High Content of Slag

In this work, more than 70 wt % of ferromanganese slag (containing 40 wt % CaO) was used to synthesize high-calcium, CaO-MgO-Al₂O₃-SiO₂ (CMAS) glass ceramics. The effect of SiO₂/CaO on the structure, crystallization behavior and microstructure of high-calcium, CMAS, slag glass ceramics was studied by IR, NMR, DSC, XRD and SEM. The results showed that in the high-calcium, CMAS glass ceramics, the main existing forms of silicon-oxygen tetrahedra (Qⁿ) were Q⁰ and Q¹. With the increase in the SiO₂/CaO, Qⁿ changed from Q⁰ and Q¹ (main units) to Q¹ (main units) and Q², and then to Q¹ and Q² (main units). The polymerization degree of Qⁿ changed from low to high, making the glass more stable, which led to the increase in crystallization temperature and the decrease in crystallization kinetic constant (k) and frequency factor (υ). At the same time, the change in the Qⁿ structure resulted in a gradual change to the main crystal, from akermanite to diopside-wollastonite.