PREPARATION OF COLLOIDAL BOEHMITE NEEDLES BY HYDROTHERMAL TREATMENT OF ALUMINUM ALKOXIDE PRECURSORS

Fairly monodisperse colloidal boehmite fibrils with a high aspect ratio were synthesized by hydrothermal treatment at 150-degrees-C of an acidified aqueous alkoxide solution, prepared by adding an aqueous HCl solution to an aluminum alkoxide precursor. The average particle length could be controlled between about 100 and 500 nm by varying the initial amounts of alkoxide and acid. Using two different alkoxides in a 1:1 molar ratio yielded the most needlelike product, having a particle length standard deviation of 40%. The boehmite particles were polycrystalline and contained 0.14 mol of excess H2O per mol of AlOOH, bound to the particle surface.