The mechanochemical treatment of a-Fe2O3 (hematite) powder in air and in ethanol at different times using a planetary ball mill was
performed. X-ray diffraction (XRD) using Rietveld analysis and Mo¨ ssbauer spectrometry showed partial transformation from a-Fe2O3
to a spinel phase for prolonged milling times in air, while only the a-Fe2O3 phase was obtained at all milling times using ethanol. Best
XRD and Mo¨ ssbauer fits were obtained by introducing two hematite components, one of them assigned to the precursor sample, and the
other one to a nanoestructured hematite. Superparamagnetic hematites were only detected in the samples milled in air. An expansion of
both a and c lattice parameters for the samples milled at all times in both environments were observed. Average grain sizes for the
nanostructured hematites milled in air were always lower than those for the samples milled in ethanol at all times, reaching a minimum of
about 11 nm. |
