PREPARATION OF UNIFORM SPHERICAL ALUMINUM HYDROUS OXIDE PARTICLES FROM ACETYLACETONATO-ALUMINUM SOLUTIONS

Uniform spherical particles of amorphous aluminum hydrous oxide (0.45-mu-m in diameter with a relative standard deviation of 0.09) were produced under a limited set of conditions in an aluminum sulfate/acetylacetone system at 100-degrees-C aged for 24 h. Grain-like crystalline alpha-AlOOH particles (2.6-mu-m in length with a relative standard deviation of 0.10) were also prepared in the absence of sulfate ions at 100-degrees-C for 42 h. Their morphology and size were sensitive to the total aluminum concentration, even though the initial pH was kept the same. The temperature dependence of the absorption spectra of acetylacetonato-aluminum complexes indicated their exothermic formation. These complexes release free aluminum ions at elevated temperatures, which subsequently hydrolyzed. The resulting polymerized hydroxo-aluminum species complexed with the sulfate ion act as precursors to particle formation.