Synthesis of magnetite as a model corrosion product by oxidation of ferrous hydroxide precipitated from ferrous sulfate by nitrate is a classical protocol to obtain monodisperse pseudo-spherical particles. However, the thorough analysis of the product has not been published. We have determined the purity of this product, regarding maghemite and sulfate content. The use of several chemical and physical analysis methods (Mössbauer spectroscopy, high-resolution transmission microscopy with energy-dispersive x-ray analyzer,…) led to the detection of high contents of maghemite (17 mol% to 38 mol%) and sulfur (about 1 mass%). Calculations from thermodynamic data indicate that the oxidant used (nitrate ions) should lead to hematite. However, due to kinetics, magnetite appears as a transient product partially oxidized to maghemite through a topotactic transformation. Pure magnetite cannot be obtained by this method of synthesis.

Subject
Scanning electron microscopy, Circuits, X-ray diffraction, Hydroxides, Iron oxide, Sulfates, Transmission electron microscopy, Solids, Synthesis, Lead, Nitrates, Magnetite, Oxidation
Keywords:
maghemite, magnetite, Mössbauer spectroscopy, particles, scanning electron microscopy, synthesis, transmission electron microscopy, x-ray diffraction
NACE International
2007
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