Glass-ceramic from fly ash with added MgO and TiO2

The effects of the addition of MgO and TiO2 to fly ash on the nucleation and crystal growth mechanisms of the derived glass are investigated with the aid of differential thermal analysis, dilatometry, X-ray diffraction and scanning electron microscopy (SEM). Phase separation occurs on heating the investigated glass. The glass-ceramic materials obtained contain anorthite (CaOAl2O32SiO2) and cordierite (2MgO2Al2O35SiO2) as the main crystalline phases. The morphology of the glass-ceramic material was investigated by SEM and it was consistent with the double-framework structure of the phase-separated glass and it was constituted by a low viscosity phase almost completely crystallised and high viscosity phase scarcely or not crystallised, depending on the heat-treatment.