Thermal decomposition of grinding activated bayerite

Abstract

Bayerite [α-Al(OH) 3] was ground for 2 h and its structure change was characterized. Soft grinding reduces the grain size of bayerite, causes a lattice distortion in bayerite, and accelerates the phase transition from bayerite to the stable phases. With addition of α-Al 2O 3 seeds, calcining the ground bayerite at 300 °C leads to the onset of the α-Al 2O 3 formation. The onset temperature and the completion temperature of the transformation to α-Al 2O 3 in the ground bayerite are about 800 and 150 °C lower than the onset temperature and the completion temperature of the transformation to α-Al 2O 3 in the unground bayerite, respectively. The thermal decomposition of the ground bayerite undergoes the α-Al(OH) 3 → γ-AlOOH → γ-Al 2O 3 → α-Al 2O 3 path without the formation of the θ-Al 2O 3 transition phase. The effect of soft grinding on the structure of bayerite and the final thermal decomposition product of bayerite will be discussed.