PREPARATION OF FE3O4 AND GAMMA-FE2O3 POWDERS BY MAGNETOMECHANICAL ACTIVATION OF HEMATITE

Total phase transformation of hematite to magnetite was accomplished a t room temperature by wet magnetomechanical activation of hematite. Lo w energy mechanical activation of the oxide surface is sufficient to e ffect the transformation. Oxygen bonds on alpha-Fe2O3 oxide surface ar e apparently broken during the mechanical activation process and oxyge n is released (removed) to the dispersing polar liquid. The oxygen pre ssure during the process as well the nature or the dispersing liquid h ave a critical influence on successful and fast phase transformation. Thus, all preparations performed in air, dry conditions or with nonpol ar hydrocarbons (benzene, anthracene) show that the process of hematit e reduction is non existent or very slow. Normal air pressure and/or a pplication of hydrocarbons suppress the transformation.