Spinel Phase Formation During the 980°C Exothermic Reaction in the Kaolinite‐to‐Mullite Reaction Series

Abstract

With the use of differential thermal analysis, X‐ray diffraction, and transmission electron microscopic techniques, we showed that γ‐Al 2 O 3 type spinel phase is solely responsible for the 980°C exotherm in the kaolinite‐to‐mullite reaction series. Transmission electron microscopic characterization indicated that the spinel formation is preceded by a phase separation in the amorphous dehydroxylated kaolinite matrix. Chemical analysis of the spinel phase by energy dispersive X‐ray spectroscopy revealed a nearly pure Al 3 O 2 composition.