Effect of aluminum source on the kinetics and mechanism of mullite preparation from kaolinite

[Display omitted] •Crystallization mechanism of kaolinite changed with addition of aluminum source.•Addition of γ-Al2O3 promotes the formation of secondary mullite from kaolin.•It is possible to prepare single-phase mullite by controlling the γ-Al2O3 amount. Addition of aluminum source was one of the effective methods to prepare single-phase mullite. The effect of different aluminum sources on phase transition kinetics and mechanism of mullite preparation from kaolinite were studied. The results showed that the addition of aluminum sources increased the phase transition activation energy (E) of kaolinite, among which the E of mixed γ-Al2O3 was increased least. The addition of γ-Al2O3 effectively reacted with the excess silicon species in kaolinite to form secondary mullite and thus increased the crystallinity of mullite. Therefore, single-phase mullite could be prepared from kaolinite by controlling the additional amount of γ-Al2O3.