NUCLEATION AND CRYSTAL-GROWTH IN A FLY-ASH DERIVED GLASS

The devitrification behaviour of a fly ash derived glass, examined by differential thermal analysis (DTA), X-ray diffraction and scanning el ectron microscopy (SEM), is reported and discussed. The crystallized p hases were identified as mullite (3Al2O3.2SiO2) and anorthite (CaO.Al2 O3.2SiO2). Kinetic parameters for nucleation and crystal growth were e stimated from the DTA curves. The temperature of maximum nucleation ra te was 790-degrees-C and the activation energy for crystal growth E = 370 kJ mol-1. The crystal morphology was investigated by SEM and the c rystal shape found to be consistent with the morphological index n cal culated by DTA. The glass-ceramic obtained from a previously nucleated glass showed a fine-grained texture.