Akira Ookubo

New types of hydrous titanium oxides obtained by homogeneous precipitation from (titanium (III) chloride + urea) solutions

Four kinds of hydrous titanium oxide (HTiO) were prepared by refluxing 1 mol dm−3 titanium (III) chloride (TiCl3) solutions containing urea (urea to titanium mole ratio=2.0, 3.0, 4.5, and 6.0; the (TiCl3 + urea) system) at 371 K. Their physicochemical properties were investigated by means of X-ray diffraction (XRD), differential thermal analysis (DTA-TG), electronmicroscopy, colour measurement, and nitrogen adsorption-desorption at 77K. A rod-like sample 0.2 µ wide and 1.0 µm long was obtained in the case of urea to titanium mole ratio of 2.0. The transmission electronmicrograph showed that the rods were aggregates of acicular crystals in a parallel arrangement. Blue samples of microcrystalline rutile were obtained in the case of an urea to titanium mole ratio above 3.0. The electron spin resonance (ESR) measurement showed that the blue colouration was ascribed to the presence of stable paramagnetic titanium (III) ions.A chemical mechanism for the formation of rod-like and blue-coloured HTiOs is proposed.