Phase transition control of nanostructured TiO_2 powders with additions of various metal-chlorides

摘要

Formation behavior and photo-oxidation abilities of nanostructured TiO_2 powders were investigated through a direct crystallization from aqueous TiOCl_2 solutions containing various metal-chlorides at 100℃. The obtained TiO_2 powders without any additives and those added with Ni~(2+), Fe~(3+) and Nb~(5+) ions, which have a similar positive ionic radius to Ti~(4+), were mainly crystallized with rutile phase, whereas those added with Al~(3+) and Zr~(4+) ions, which have a quite different positive ionic radius, were mainly crystallized with anatase phase. On the other hand, the secondary particles in the TiO_2 powder consisted of acicular and spherical primary particles corresponding to rutile and anatase phases, respectively. From these results, it seems that the positive ionic radius of the additives would affect phase formation as well as morphology of TiO_2 precipitates. Among the TiO_2 powders prepared, Ni-added powder, which consisted mainly of rutile phase with a small amount of anatase phase, showed excellent photocatalytic ability in decomposition of 4-chlorophenol.