Novel synthesis of α-alumina hexagonal nanoplatelets using electrostatic spray assisted chemical vapour deposition

Electrostatic spray assisted chemical vapour deposition was used to synthesize well-defined hexagonal alpha-alumina nanoplatelets. Aluminium 2,4-pentanedionate was used as a precursor; it was dissolved in butanol to form a solution with a concentration of 0.01-0.05 M. The precursor solution was atomized and sprayed onto a heated glass substrate through an electrostatic nozzle with an electric potential between 5 and 20 kV. The decomposition of the chemical precursor was controlled by monitoring both the substrate temperature and the temperature gradient between the substrate and nozzle. Both as-deposited and annealed powders were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The as-deposited powders were found to be amorphous aluminas. The hexagonal alpha-alumina platelets, with an average diameter less than a micron and an average thickness of 20-80 nm, were formed after annealing at 700 degrees C. The single crystalline nature of these nanoplatelets was confirmed by selected area electron diffraction and high resolution transmission electron microscopy.