Recycling of High Ferrous Bauxite Reducing Slag for Synthesis of CaAl2Si2O8-Al2O3-CaAl12O19 Composite

CaAl2Si2O8-Al2O3-CaAl12O19 (CAS(2)-Al2O3-CA(6)) composite was synthesized through reaction sintering alumina and bauxite reducing slag. The CAS(2)-Al2O3-CA(6) composite was mainly composed of alpha-Al2O3, CAS(2) and CA(6). Gehlenite (Ca2Al2SiO7, C(2)AS) phase was effectively transformed to CAS(2) and CA(6) through high-temperature reaction sintering under weak oxidizing atmosphere at 1400 degrees C for 4 h. SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy) analysis indicated that black and needle-shaped Al2O3, rhombic or irregular polygonal-shaped FeAl2O4, and glassy phase Ca2Al2SiO7 disappeared after the reaction sintering. The light gray and flaky hexagon crystals of CaAl12O19 (10 mu m) and the grainy particles of Al2O3 (2 7 mu m) were observed in the CAS(2)-Al2O3-CA(6) composite. The gray crystals of CAS(2) act as the binding phase and arc distributed around CA(6) and Al2O3. CAS(2)-Al2O3-CA(6) composite exhibits high refractoriness and service temperature, which are 1650 degrees C and 1450 degrees C, respectively. Reaction sintering of alumina and bauxite reducing slag is a feasible method for the synthesis of CAS(2)-Al2O3-CA(6) composite.