Crystallization kinetic of glass particles prepared from a mixture of coal ash and soda-lime cullet glass

The crystallization capability of a parent glass made from a mixture of coal ash (40 wt%) and soda-lime glass was investigated using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy. Different glass particle size distributions were considered in the range 20-500 mum. Two crystallization exotherms in DTA were attributed to the formation of both pyroxenes (diopside Ca(Mg,Al)(Si,Al)(2)O-6 and augite Ca(Mg,Fe)Si2O6) and plagioclase (Na,Ca)(Si,Al)(4)O-8. These phases were confirmed by XRD analyses. Analysis of non-isothermal DTA data yielded values of 545 kJ/mol and 1.8 for the activation energy of crystallization and the Avrami exponent, respectively. This value for the Avrami exponent was consistent with a decreasing nucleation rate and the observed dendritic morphology. The data on crystallization kinetics obtained in this study are relevant for the production of glass-ceramic materials by a sintering/crystallization method from powder compacts made of this parent glass. (C) 2003 Elsevier B.V. All rights reserved.