Structure and properties of in situ synthesized FeSi2-diopside glass ceramic composites from Bayan Obo tailings, blast furnace slag, and fly ash

FeSi₂ -glass ceramic composites are successfully synthesized in situ from Bayan Obo tailings, blast furnace slag, and fly ash by a melting method. The effects of Fe₂O₃ on the crystallization behavior, microstructure, and performance of the composites have been investigated by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, transmission electron microscopy, and mechanical performance tests. The results show that the glass ceramics are composed of a diopside dendritic crystal matrix (primary phase) in which FeSi₂ metal particles with diameter ∼5 μm are dispersed (dispersed phase). With increase in the amount of Fe₂O₃, the crystallization activation energy of the composites decreases from 343.20 to 309.71 kJ/mol and the Avrami parameter increases from 2.12 to 3.17. The composites exhibit the maximum density of 3.04 g/cm³, microhardness of 8.37 GPa, bending strength of 210.27 MPa, impact toughness of 3.68 kJ/m², acid resistance of 97.91%, and alkali resistance of 98.85%, proving their high potential for various industrial applications.