Optimization of the calcination temperature for the solvent-deficient synthesis of nanocrystalline gamma-alumina
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Nano-sized alumina is prepared using a cost-effective solvent-free method with aluminum nitrate and ammonium bicarbonate precursors. Combined investigations by thermal analysis (TG/DTA), X-ray diffraction (XRD), specific surface area (BET), scanning electronic microscopy (SEM), infrared emission spectroscopy (FTIR), dynamic light scattering (DLS) and dilatometry were used to examine the effects of calcination temperature on the formation of Al2O3. XRD analysis shows that the γ-Al2O3 phase forms already at 300 °C and slowly continues to form with increasing temperature indicating a diffusion-controlled reaction as shown by FTIR. The size of the γ-Al2O3 nanocrystalline, as determined by XRD, is between 1.5 and 1.9 nm and slowly increased with the reaction temperature. DLS results revealed that a particle size of γ-Al2O3 dispersed in water grows with increasing reaction temperature due to nanocrystalline particle aggregation, which was additionally confirmed by SEM. The densification behavior of the boehmite and γ-Al2O3 phases was investigated using dilatometry.
KeywordsAl2O3 Solvent-free method Phase transformation Densification
The authors are grateful for the financial support of the Ministry of Science and Technology of Republic of Srpska (Project 19/6-020/961-49/12).
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