Marvelous prolongation of lifetime of alumina sol from aluminum sec-butoxide with the presence of ethylacetoacetate in aqueous medium

A mol. ratio around 1-mol aluminum sec-butoxide(ASB) to 100-mol water has been generally used for the preparation of alumina sol by peptizing process. It was found that the lifetime of this alumina sol was only about half month. Due to its short lifetime, this alumina sol was sometimes limited to synthesize alumina sol-gel materials via such methods as spraying, moulding, electrophoresis deposition, spin- and dip-coating, etc which had much dependence on the viscosity condition of sols. On the industrial point of view, the short lifetime also limited this alumina sol to be a commercial product on market. In the present study with the addition of EAcAc the lifetime of this alumina sol was found to be prolonged for 24 times and reach about twelve months. The corresponding reaction mechanism was investigated by TEM and UV absorption spectra determinations of the sols. EAcAc was considered in this study to be reacted with the neighboring HO-Al groups exposed on the surface of the colloidal particles, but not as has been usually figured to be reacted directly with ASB precursor. Such a reaction results in the formation of an outside layer around the colloidal particle which contributed largely to decreasing the activity of Al₂O₃ colloidal particle. The present study would accelerate the full applications of this alumina sol both in lab and market scope.