From High-Energy Ball-Milling to Surface Properties of TiO2 Powders

Abstract. TiO 2 -II, a high-pressure and high-temperature modification of TiO 2 , is an intermediate phase in the polymorphic transformation of anatase into rutile which is induced by room-temperature high-energy ball-milling. The kinetics and mechanisms of the phase transformation of ground anatase into TiO 2 -II were compared for two types of as-received titania powders. The main differences between both powders were the rutile content and the particle size. The ground powders were characterized by determining their composition and measuring the size evolution as a function of milling time. TiO 2 -II was transiently formed, the maximum fraction being reached at 25 minutes milling. TEM investigations showed that TiO 2 -II crystallites were formed at the particle surface for one powder and in the bulk for the other one (initial mean diameter resp.150 and 25 nm). The surface properties of the ground powders were characterized mainly by zeta potential measurements at different pHs and by volumetric experiments. Changes of the surface properties of the ground powders with respect to those of as-received powders are evidenced and discussed.