Nanocrystalline gamma-alumina synthesized by sonohydrolysis of alkoxide precursor in the presence of organic acids: Structure and morphological properties

gamma-Al2O3 nanoparticles with an average size of 5 nm were synthesized by the hydrolysis of aluminum triisopropoxide under the influence of power ult rasound (100 W/cm(2)) and in the presence of formic or oxalic acids as pept izers, followed by calcination. The structural and morphological properties of the as-prepared precursor hydroxides and calcined nanocrystalline powde rs were characterized by XRD, SEM, TEM, TGA, IR, and BET. The ultrasound-dr iven cavitation process has been shown to affect the agglomeration of the p recursor nanoparticles by condensation of interparticle hydroxyls. The oxal ate anions were strongly adsorbed on the surface of the precursor nanoparti cles and thus retarded the ultrasound-driven condensation of interparticle hydroxyls, Formic acid showed a lesser degree of adsorption on the surface of the precursor particles. The ultrasound-driven agglomeration of the prim ary particles as well as the role of organic modifiers on the microstructur al properties of the precursor and the target alumina phases have been disc ussed.