Kinetics and mechanisms of phase transformations induced by ball-milling in anatase TiO2

Ball-milling is a way of inducing phase transformations, chemical reactions , and changes in the reactivity of solids. It is a complex process for whic h several models have been developed to predict the evolution of systems an d to describe its physics. These models sometimes empirically need experime ntal data to be ascertained and to confirm general theories of system evolu tions. In this work, we investigate the effect of two milling parameters, t he powder to ball weight ratio R and the nature of the grinding media, on t he kinetics of phase transformations in anatase TiO2 powder. These experime nts established that R affects only the reaction rate. The kinetics are fas ter with alumina than with steel grinding tools for a given R, specific inj ected powers being similar. It has been demonstrated that the phase transfo rmations induced by grinding TiO2 occur without fracturing of particles and mechanisms are commented upon. (C) 2000 Academic Press.