Crystallization Behavior of CaO-SiO₂-Al₂O₃-MgO-TiO₂-FeO Slag with Different CaO/SiO₂ Ratios

Area of Science:

• Materials Science
• Geochemistry
• Ceramic Engineering

Background:

• Titanium-extracted tailing, a byproduct of titanium-bearing blast furnace slag treatment, requires understanding its crystallization behavior for effective glass-ceramics preparation.
• The CaO-SiO2-Al2O3-MgO-TiO2-FeO slag system is investigated for its potential in glass-ceramics.

Purpose of the Study:

• To explore the effect of varying CaO/SiO2 ratios on the crystallization behavior of titanium-extracted tailing.
• To investigate phase and microstructure evolution during slag cooling.

Main Methods:

• FactSage 8.2 calculations for thermodynamic analysis.
• Mineralogical characterizations for phase identification.
• Single hot thermocouple technique (SHTT) for in situ observation of crystallization.

Main Results:

• Specific CaO/SiO2 ratios (0.7-1.1) promote perovskite, melilite, spinel, diopside, and anorthite crystallization.
• Higher CaO/SiO2 ratios (1.3-1.5) favor olivine and merwinite but inhibit diopside and anorthite.
• Initial crystallization and liquidus temperatures increase with CaO/SiO2 ratio.
• Perovskite controls initial crystallization for ratios 0.7-1.3; spinel controls at 1.5.
• Incubation time for nucleation decreases, and critical cooling rate increases with higher CaO/SiO2 ratios.

Conclusions:

• The CaO/SiO2 ratio is a critical parameter controlling phase formation and crystallization kinetics in titanium-extracted tailing.
• Optimizing the CaO/SiO2 ratio can enhance the glass-ceramics preparation process by influencing crystal structures and cooling rates.
• Findings provide insights for utilizing titanium slag in advanced material applications.