Low-temperature preparation of spherical nano α-Al2O3 particles by chelating the structure of anhydrous aluminium sols.

α-Al 2 O 3 exhibits excellent physical and chemical stabilities and thus has a wide range of applications in various fields, however the potential application are often called off because of the grains coarsening and vermiculite structures originated from the high-temperature calcination process. In this paper, the calcination temperature has been significantly reduced by selecting the chelating anhydrous aluminium sols as the precursor. It was found that when the chelating agent was malic acid and the addition amount was 0.06 mol, the chelated structure had the highest content of [AlO 6 ] octahedra, which was more favourable for the low-temperature synthesis of α-Al 2 O 3. Kinetic analysis showed that the activation energy for the conversion of γ-Al 2 O 3 to α-Al 2 O 3 in this work was 398.09 kJ mol−1, which has been reduced by nearly 100 kJ mol−1 and thus the complete conversion of γ-Al 2 O 3 to α-Al 2 O 3 was achieved by holding at 900 °C for 2 h. The obtained spherical α-Al 2 O 3 nanoparticles, with a particle size of about 67.2 nm and a uniform morphology. After further extending the holding time to 30 h, the complete conversion of α-Al 2 O 3 was achieved at 825 °C, while the initial nucleation temperature was lower than 760 °C. [ABSTRACT FROM AUTHOR]