Hydrothermal synthesis and characterization of nano-particles γ-Al₂O₃

Abstract

The study of hydrothermal treatment on the phase formation and the crystallites of gamma-alumina (γ-Al2O3) was performed. Different reaction time and temperature of hydrothermal treatment were investigated. The preparation of γ-Al2O3 includes precipitation of aluminum nitrate nonahydrate by ammonia, aging, washing, transferred the gel into the hydrothermal reactor, drying, and calcination at 600 °C. The precipitation was stopped at pH equals 7.5. The reaction times of hydrothermal treatment were 1 – 2 hours, and the temperatures were 140 – 200 °C. X-Ray Diffraction analysis was used to investigate the phase formation and the particle size. The results show all the samples represented pure nano γ-Al2O3. The examination of hydrothermal treatment of y-Al2O3 reveals as the reaction time longer, the crystallite grows bigger, as well as the higher temperature applied. The smallest γ-Al2O3 obtained based on the Scherrer equation is 4 nm and the biggest is 6.5 nm. Interestingly, the peaks of the γ-Al2O3 prepared by hydrothermal treatment at the longest time and the highest temperature have shifted into a higher diffraction angle. In the case of this sample, the peaks shifted into a higher diffraction angle. That is means there is a change in the lattice structure of γ-Al2O3 probably was affected by the lattice of hydroxyl content.