Effect of Cr₂O₃ on Crystallization of Diopside Glass–Ceramics

Abstract

CaO–MgO–Al2O3–SiO2–Cr2O3 diopside glass–ceramics were prepared from blast furnace slag, low-carbon ferrochromium alloy slag, and quartz sand by the melting method. The prepared glass–ceramics were characterized by differential thermal analysis (DTA), X-ray diffraction (XRD),scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The effect of Cr2O3, a nucleating agent, in the crystallization process of diopside glass–ceramics was studied. The results show that chromium is present in glass–ceramics as Cr3+ and Cr6+, and Cr3+ accounts for more than 80% of the chromium contents. When the mass percentage of Cr2O3 in glass–ceramics is less than 1.60%, a small amount of diopside phase is precipitated during heat treatment, and Cr3+ is dispersed in the diopside phase. When the mass percentage of Cr2O3 reaches or exceeds 1.60%, Cr3+ preferentially forms the magnesia chrome spinel phase, which further induces the in situ growth of diopside. The leaching concentration of chromium meets the Chinese national standard, indicating that diopside glass–ceramics can effectively solidify the heavy metal chromium, and this fact makes the application of glass–ceramics feasible.

Keywords

• Cr₂O₃
• diopside
• magnesia chrome spinel
• glass–ceramics
• in situ growth