SYNTHESIS OF NANOCRYSTALLINE α-ALUMINA POWDER THROUGH WET-CHEMICAL ROUTE

α-Al2O3 nanocrystalline powders were synthesized by calcining the dry Al(OH)3 gel prepared from aluminum nitrate and ammonia. Phase transformation sequence of dry Al(OH)3 gel during heating is Al(OH)3 →γ-AlOOH →γ-Al2O3 →δ-Al2O3 →θ-Al2O3 →α-Al2O3. NH4NO3 in the Al(OH)3 gel reduce the γ、 δ、θ and α-Al2O3 transformation temperature dramatically, where the temperature for the formation of α-Al2O3 decreases 50～100℃. θ-Al2O3 →α-A12O3 transformation temperature decreases 200℃ by adding 2% α-Al2O3 seeds. The θ→α-Al2O3 transformation temperature can be reduced to 900℃ by the combined effect of NH4NO3 and seeds, 300℃ lower than the normal transformation temperature. The obtained α-A12O3 powder has no obvious agglomeration, narrow particle size distribution, spherical shape, and a mean particle size of 10nm.