Photo-stability of TiO2 particles coated with several transition metal oxides and its measurement by rhodamine-B degradation

Titanium dioxide is the best white pigment, but it does not have good photo-stability if it is not properly coated. As a change from the conventional coating with silicon or aluminum oxide, its photo-stability after coating with zirconium, cerium as well as some other transition metal oxides was investigated. The function of the coated film was to capture electrons and holes of the TiO2 particles produced by the ultraviolet irradiation that otherwise could produce free radicals on the TiO2 surface. A new more efficient, easier and more accurate method that used rhodamine-B degradation was used to evaluate the photo-stability of the coated TiO2 particles. TiO2 particles coated with the oxides of zirconium, cerium, cobalt or nickel had excellent weather durability, even with only a small amount of coating. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.