Pressure influenced combustion synthesis of  - and  -Al2O3nanocrystalline powders

Aluminium oxide nanocrystals have been prepared via a straightforward reaction, initiated at low temperatures (<300 ◦C), 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 sub-microcrystalline) and for the resulting crystalline phase (γ- or α-Al2O3) of these powders. The fibre-like morphology obtained for the as-synthesized γ-Al2O3 permits the synthesis of nanocrystalline α-Al2O3 (∼55 nm) even after a high temperature treatment at 1200 ◦C. The findings suggest a promising approach for controlling the size and crystal phase of the particles. 1.