Influence of existence state of Fe³⁺/Ti⁴⁺ on structure of Al₂TiO₅ss/3Al₂O₃ · 2SiO₂ss composite

The structural stability of Al₂TiO₅ss/3Al₂O₃·2SiO₂ss composite based on middle-low grade bauxite calcined at 1 600℃ and held subsequently at 1 200℃ for 12 h was studied by XRD, SEM and energy dispersive spectroscope (EDS). The results show that after middle-low grade bauxite being calcined at 1 600℃, its crystal phase composition consists of 3Al₂O₃·2SiO₂ss, Al₂TiO₅ss and a little cristobalite, in which Fe³⁺/Ti⁴⁺ cations exsit in crystalline phases (3Al₂O₃·2SiO₂ss and Al₂TiO₅ss) and amorphous phase (silicate) in different forms. Al₂TiO₅ss is separated and huddled by 3Al₂O₃·2SiO₂ss containing Fe³⁺/Ti⁴⁺ cations, restraining its decomposition; in addition, both 3Al₂O₃·2SiO₂ss and Al₂TiO₅ss build compact skeleton structure of Al₂TiO₅ss/3Al₂O₃·2SiO₂ss synthesis system based on middle-low grade bauxite due to their near element composition, which avoids appearance of silicate phases with low melting point and further endows good structural stability.