Microstructural characterisation of a glass and a glass-ceramic obtained from municipal incinerator fly ash

摘要

Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD)analyses were used to characterise the microstructure and chemicalcomposition of a glass and a glass-ceramic material obtained fromincinerator filter fly ash. Although the as-quenched material(vitrified fly ash) was amorphous under the detection limits ofXRD, a dispersion of droplets indicating glass-in-glass phaseseparation was observed. In the glass-ceramic material (crystallisedvitrified fly ash), crystals belonging to the pyroxene group andspinels were identified. The microstructure of the glass-ceramicconsisted of crystals embedded in an amorphous glassy phase. Thecrystalline phases contain a higher amount of metallic elements(e.g. Al, Cr, Fe, Ni and Zn and most probably also other heavymetals) than the residual glassy phase. A change of composition ofthe residual glass phase in the glass-ceramic product, incomparison with the parent glass, is considered to explain, incomparative terms, the higher toxic potential of the glass-ceramicover the glass.