SIZE CONTROL OF ALPHA-ALUMINA PARTICLES SYNTHESIZED IN 1,4-BUTANEDIOLSOLUTION BY ALPHA-ALUMINA AND ALPHA-HEMATITE SEEDING

The effects of seed particles and shear rate on the size and shape of alpha-Al2O3 particles synthesized in glycothermal conditions are descr ibed. It is proposed that seed particles provide a low-energy, epitaxi al surface in solution to lower the overall surface energy contributio n to the nucleation barrier, thus increasing nucleation frequency and subsequently reducing the particle size of hexagonal alpha-Al2O3 plate lets or polyhedra. depending on synthesis conditions, in 1,4-butanedio l solution. Seeds have a significant effect on the size of hexagonal a lpha-Al2O3 platelets in samples with high seed concentration, The part icle size of alpha-Al2O3 platelets decreases from 3 to 4 mu m to 100 t o 200 nm by increasing the number concentration of seeds. In the case of alpha-Fe2O3 seeding, the effect of seeding on the size of alpha-Al2 O3 particles closely resembles the effects obtained with alpha-Al2O3 s eeding. Regardless of seed concentration, high stirring rate promotes the formation of hexagonal platelets with high aspect ratio, whereas m edium and low stirring rates promote the formation of elongated platel ets and polyhedra with 14 faces, respectively.