Cordierite-based ceramics from stevensite clay and coal fly ash

ABSTRACT Cordierite-based ceramic is one of the most interesting engineering materials that has attractive and multidisciplinary assets, such as low thermal expansion coefficient, excellent thermal shock resistance, high refractoriness, good mechanical properties, and so on. In this work, cordierite-based ceramics were prepared mainly from stevensite-rich clay or coal fly ash (CFA) and stevensite-rich clay using a solid-state interaction process. The influence of heating temperature, in the range of 800–1250°C, and starting materials on the microstructure-temperature evolutions and mechanical strength were evaluated using TGA-DTA, XRD, FTIR, SEM, and dilatometric analysis. The results revealed, for both formulations heating in the temperature range 800–1100°C, the transformation of stevensite-rich clay into enstatite and its polymorphisms. Further heating induced the formation of the cordierite phase at 1200°C, for the formulation consisted mainly of stevensite-rich clay and CFA, and at 1250°C for that contained mainly stevensite-rich clay. The addition of CFA to stevensite-rich clay enhanced its reactivity and involved the increase in mechanical strength from 5 MPa to 15 MPa at 1200°C.