Mechanochemical-molten salt synthesis of α-Al2O3 platelets

The polyaluminium chloride (PACl) precursor was used for a simple and scaled-up mechanochemical-molten salt synthesis of α-Al2O3 platelets. PACl, as a low temperature α-Al2O3 precursor, was firstly mechanically activated by high-energy ball milling for 5 min, followed by a next 5 min ball milling in the presence of a NaCl-KCl salt mixture. The starting formation temperature of the α-Al2O3 phase was 600 °C. In the subsequent annealing in the temperature range of 660-1000 °C, the α-Al2O3 phase with a well developed plate-like morphology was obtained. The products were characterized by X-ray powder diffractometry, scanning electron microscopy (SEM), and thermal analysis (DTA, TG) and solution 27Al NMR spectroscopy.