A process for the production of sub-micron to millimetre sized thermally stable alpha-alumina spheres

The sol-emulsion-gel method has been employed to produce alumina gel sphere s from unseeded as well as seeded alumina sol. Controlled heating of the un seeded gel spheres leads to the formation of alpha-alumina phase at 1200 de grees C. Various seeds have been tried to determine the effect of seeding o n the formation of alpha-alumina and it is found that seeding with 0.5 wt.% Fe2O3 leads to the formation of alpha-alumina at a relatively low temperat ure of 950 degrees C. The sizes of the microspheres can be varied in the ra nge between 0.5 mu m and 1 mm by suitable choice of the process parameters. The resultant gel spheres on controlled heating transform into thermally s table alpha-alumina spheres. (C) 1999 Elsevier Science S.A. All rights rese rved.