Synthesis of α-Fe2O3 Templates via Hydrothermal Route and Fe3O4 Particles Through Subsequent Chemical Reduction

FeCl3-NH4H2PO4 system was employed to fabricate alpha-Fe2O3 nanoparticles by a hydrothermal method. The results showed that the most important factors affecting the size and morphology of as-prepared alpha-Fe2O3 particles were the reactant concentration and the molar ratio of iron precursor to additives, i.e., [Fe3+]/[H2PO4-]. Besides alpha-Fe2O3 rings and tubes, single-crystalline alpha-Fe2O3 rods with controllable size were successfully fabricated by adjusting the [Fe3+]/[H2PO4-] ratio. The formation mechanism for alpha-Fe2O3 nanocrystals with different shapes was studied. In order to produce Fe3O4 particles (in ring, tube or rod shapes), the as-prepared alpha-Fe2O3 particles were employed as templates. Phase conversion from hematite to magnetite was achieved via a chemical reduction method. In this reduction process, both surfactants (oleic acid) and protective gas (5% H-2/95% Ar gas mixture) were used as reduction agents. The effect of oleic acid and H-2 gas on the reduction process of alpha-Fe2O3 particles was studied through a series of experiments. The results indicated that the chemical reduction method was convenient and feasible to reduce various hematite templates to corresponding magnetite nanostructures.