Synthesis of nano-crystalline alumina powder by Sol-gel Process

Sol-gel synthesis of nano-crystalline alumina powder by an alkoxide route is investigated and several subsequent processing techniques, such as emulsification, seeding and spray drying techniques are used to improve the powder characteristics. It is noticed that the nano-structured gel undergoes coarsening after calcination at elevated temperature. Seeding of the sol with nano-crystalline a-Al2O, powder is observed not only lower the phase formation temperature but also control the sizc of the calcined powders. The emulsification process can also be used effectively to control the morphology and size of the particles. The spray drying of the sol is observed to yield micrometer sized alumina powder, which can be used dircctly for the spray coating after calcination. During calcination, the hollow sphcrc obtained in the spray drying forms ring shaped powder