Influence of different preparation methods on crystallisation and morphology of Fe2O3 nanoparticles

Iron oxide nanoparticles were prepared by adsorption phase synthesis (APS), impregnation method (IM) and precipitation synthesis (PS). The grain sizes of Fe₂O₃ prepared by APS and IM were much smaller than that by PS. In the APS process, when the reaction took place in the adsorption layer, strong chemical bonds between Fe₂O₃ particles and silica could be built, which inhibited the phase transformation from γ-Fe₂O₃ to α-Fe₂O₃ during the calcination process. The physical interaction did not restrain the crystal transformation although the restriction on the aggregation of Fe₂O₃ particles was obvious.