MECHANOCHEMICAL TRANSFORMATION OF HEMATITE TO MAGNETITE

The transformation of alpha-Fe2O3 to Fe3O4 on wet-milling alpha-Fe2O3 under low energy conditions in vacuum has been investigated by Mossbau er effect spectroscopy. The structural transformation is discrete with no evidence of interdissolution of the 2 phases. The resultant simila r to 30 nm scale crystal blocks of magnetite exhibit hyperfine feature s characteristic of bulk Fe3O4 although evidence for structural distor tion of the octahedral (particularly) and tetrahedral iron sites is ob tained. The results are consistent with a primarily physical origin fo r the transformation in which oxygen bonds on the cleaved alpha-Fe2O3 surface are broken and oxygen released to the milling environment.