Investigation of glassy phase silica in low calcium content fly ash by X‐ray photoelectron spectroscopy

Abstract

The present study investigates the glassy and crystalline phases of silica content in different fly ash sources by X‐ray photoelectron spectroscopy (XPS). The X‐ray diffraction (XRD) patterns of fly ash show the existence of crystalline quartz, aluminosilicate, and hematite phases. Other minor phases viz., CaO, TiO2, and K2O have also been identified in the fly ash samples. The signature of glassy phase (amorphous content) of silica is identified by a hump over the 2θ range of 20–30° in X‐ray diffraction pattern. A detailed study of amorphous and crystalline silica, aluminosilicate, ferric oxide, and calcium oxide is done by XPS. Quantitative analysis of Si 2p spectra of both fly ash samples shows amorphous content of SiO2 in the range of 10–40 atomic percent. Other phases, namely, mullite (24–65 at.%), alumina (35–75 at.%), and crystalline SiO2 (60–90 at.%) have also been found in both the fly ash samples.