TRANSFORMATION, MICROSTRUCTURE DEVELOPMENT, AND DENSIFICATION IN ALPHA-FE2O3-SEEDED BOEHMITE-DERIVED ALUMINA

Addition of alpha-Fe2O3 seed particles to alkoxide-derived boehmite sols resulted in a 10-fold increase in isothermal rate constants for the transformatiou of gamma- to alpha-Al2O3. Changes in porosity and surface area with sintering temperature showed no effect of seeding on coarsening of the transition alumina gels, but the 200-fold decrease in surface area associated with transformation to alpha-Al2O3 occurred almost-equal-to 100-degrees-C lower in seeded gels compared with unseeded materials. As a result of high nucleation frequency and reduced microstructure coarsening, fully transformed seeded alumina retained specific surface areas >22 m2/g and exhibited narrow pore size distributions, permitting development of fully dense, submicrometer alpha-Al2O3 at almost-equal-to 1200-degrees-C.