Initial stages of the transformation of single-crystal anatase particles during high-energy ball milling

The initial steps of the phase transformation of anatase by high-energy bal l milling have been followed as a function of milling time by X-ray diffrac tion and transmission electron microscopy (TEM). The metastable TiO2 II pha se appears after several minutes of grinding. The anatase-TiO2 II transform ation occurs without particle fracture. TEM shows the simultaneous strain h ardening of anatase particle cores and the formation of TiO2 II crystallite s at the surface of anatase particles. The TiO2 II crystallites have an ave rage diameter of about 10 nm. The possible mechanisms of the transformation are commented upon.