Nanogibbsite: synthesis and characterization.

Nanogibbsite was synthesized using a supersaturated Al(OH)(3) solution which was prepared by titration of AlCl(3) with NaOH at pH 4.6. Excess chloride ions in the system were stripped off by dialyzing the Al(OH)(3) suspension against distilled water. The dialysis step is critical for initiation of gibbsite crystallization or the Al(OH)(3) suspension would remain amorphous. Chloride ions seem to mask the seeding sites and so retard the overall process of gibbsite formation. When subjected to heat treatment, gibbsite→alumina conversion occurred by two mechanisms. Nanogibbsite→α-alumina phase transition occurred forming χ- and κ-alumina polymorphs.