Recycling of High Ferrous Bauxite Reducing Slag for Synthesis of CaAl2 Si2 O8-Al2 O3-CaAl12 O19 Composite

CaAl2Si2O8-Al2 O3-CaAl12O19 (CAS2-Al2 O3-CA6) composite was synthesized through reaction sintering alumina and bauxite reducing slag. The CAS2-Al2O3-CA6 composite was mainly composed of α-Al2O3, CAS2, and CA6. Gehlenite (Ca2 Al2SiO7, C2AS) phase was effectively transformed to CAS2 and CA6 through high-temperature reaction sintering under weak oxidizing atmosphere at 1400 °C for 4 h. SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy) analysis indicated that black and needle-shaped Al2 O3, rhombic or irregular polygonal-shaped FeAl2 O4, and glassy phase Ca2 Al2SiO7 disappeared after the reaction sintering. The light gray and flaky hexagon crystals of CaAl12 O19 (10 μm) and the grainy particles of Al2O3 (2-7 μm) were observed in the CAS2-Al2O3-CA6 composite. The gray crystals of CAS2 act as the binding phase and are distributed around CA6 and Al2O3. CAS2-Al2 O3-CA6 composite exhibits high refractoriness and service temperature, which are 1650 °C and 1450 °C, respectively. Reaction sintering of alumina and bauxite reducing slag is a feasible method for the synthesis of CAS2-Al2 O3-CA6 composite.