Porous xerogel systems B2O3-Al2O3 obtained by the sol-gel method

A series of binary oxide systems B2O3/Al2O3 with the B/Al molar ratios of 0.05, 0.1, 0.2, 0.30, 0.4 and 1.0 have been synthesized by the sol-gel technique from aluminium isopropoxide (Al[OCH(CH3)2]3) and boric acid (H3BO3). The proper choice of drying conditions permits obtaining uniform monoliths up to a molar ratio of B/Al = 0.3. In the synthesis of B2O3/Al2O3 system, boric acid acts both as a precursor of boron and a catalyst for the esterification extending between acetic acid and isopropyl alcohol, leading to much easier removal of organic residues from the sol-gel synthesis. The systems were characterized by X-ray diffraction, transmission and scanning electron microscopy (TEM and SEM), thermogravimetric analysis (TGA), and TGA coupled with mass spectrometer and ultraviolet-visible spectroscopy (UV-VIS).