Preparation of glass-ceramics from red mud in the aluminium industries

The feasibility of recycling red mud and fly ash in the aluminium industries by producing glasses and glass-ceramics has been investigated. The crystallization behavior of glass-ceramics mostly produced from red mud and fly ash was studied by DTA, XRD, optical microscopy techniques. According to DTA curve, nucleation experiments were carried out at various nucleation temperatures at the same crystallization temperature of 900 °C for 2 h, and crystallization experiments were performed at the same nucleation temperature of 697 °C for 2 h followed by crystallization at various temperatures. The nucleation results show that optimum nucleation temperature is near 697 °C, and the crystallization experiments show that the crystallization at a high temperature of over 900 °C results in denser grain size. The major crystallized phases were gehlenite (Ca2Al2SiO7), and augite (Ca(Fe,Mg)Si2O6). The XRD results show that with the increase of crystallization temperature, the amount of gehlenite increases, and augite decreases, which is the result of augite transformation into gehlenite.