Direct phase transformation from hematite to maghemite during high energy ball milling

Hematite alpha -Fe2O3 powder was milled with a dispersing liquid (ethanol) for different times using a conventional planetary ball mill equipped with a steel vial. Both high resolution transmission electron microscopy (HRTEM) , X-ray diffraction and zero- and in-field Mossbauer spectrometry measureme nts reveal that the nanostructured powders contain maghemite, suggesting th at our milling conditions favour the direct transformation from alpha -Fe2O , to gamma -Fe2O3. Both the origin and the kinetics of the transformation a re discussed in terms of mechanical aspects. (C) 2001 Elsevier Science B.V. All rights reserved.