Pressure influenced combustion synthesis of γ- and α-Al2O3 nanocrystalline powders

Aluminium oxide nanocrystals have been prepared via a straightforward reaction, initiated at low temperatures (<300 degreesC), between aluminium nitrate and hydrazine. The initial pressure parameter is found to be responsible for the variations of the particle size (ranging from nanocrystalline to submicrocrystalline) and for the resulting crystalline phase (gamma-or alpha-Al2O3) of these powders. The fibre-like morphology obtained for the as-synthesized gamma-Al2O3 permits the synthesis of nanocrystalline alpha-A(2)O(3) (similar to55 nm) even after a high temperature treatment at 1200degreesC. The findings suggest a promising approach for controlling the size and crystal phase of the particles.