Iron oxide and jadeite nucleation in high alumina glass-ceramics prepared from secondary aluminum dross

Secondary aluminum dross (SAD) is a solid waste of aluminum dross after it is extracted aluminum. Soda-limealuminosilicate (SLAS) glass-ceramics with high alumina contents (over 30 wt%) were successfully manufactured from SAD using pyrometallurgy without additional nucleation agents. The nucleation process of SLAS glass was studied, and 670 degrees C was selected as the nucleation temperature according to differential scanning calorimetry and X-ray diffraction results. Field-emission transmission electron microscopy was applied to study the microstructure of the specimens thermally treated at 670 degrees C for 3 and 12 h. Nucleation consisted of two parts: iron oxide nucleation and jadeite nucleation. During iron oxide nucleation, when the thermal treatment time increased from 3 to 12 h, the iron oxides first congregated in an amorphous phase and a small amount of metastable crystal; then, the congregated iron oxides crystallized into hematite and magnetite, which acted as crystal nuclei. During jadeite nucleation, the jadeite spontaneously crystallized from the glass matrix after thermal treatment at 670 degrees C. When the thermal treatment time increased from 3 to 12 h, the size of the jadeite crystals increased from approximately 6 to 12 nm. Jadeite crystals with a diameter of 12 nm acted as crystal nuclei. For glass-ceramics with a high content of aluminum and sodium, jadeite crystals can act as crystal nuclei without additional nucleation agents.

Automated summary

Secondary aluminum dross (SAD) was successfully used to manufacture high-alumina-content SLAS glass-ceramics without additional nucleation agents, with a nucleation temperature of 670 degrees C. Iron oxide and jadeite nucleation processes were studied, revealing that jadeite crystals can act as crystal nuclei in glass-ceramics with high aluminum and sodium contents.