Topotactic conversions of γ-FeOOH and comparative transformation methods of iron oxides in magnetic spinels |
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Authors: | E Mendelovici R Villalba A Sagarzazu |
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Affiliation: | Laboratorio Físicoquimicca de Materiales, CIC, IVIC, Apartado 1827, Caracas 1010-A, Venezuela |
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Abstract: | The DTA of a natural, well crystallized lepidocrocite sample containing small amounts of goethite, quartz and manganese shows that the conversion of γ-FeOOH to -Fe2O3 (through the γ-Fe2O3 metastable phase) occurs at 440°C, whereas in pure, synthetic γ-FeOOH the exothermic peak appears at ˜ 500°. Quartz (1.4% SiO2) is not affected, nor does it hamper the transformation of FeOOH into magnetic spinels, when the sample is reacted with glycerol at reflux temperature followed by hydrolysis of the resulting solid (iron alkoxide) by boiling H2O. Starting γ-FeOOH and final solid products are characterized by XRD and IR spectroscopy. This reaction is also discussed comparatively with the solid state transformations of iron oxides into magnetic materials by a combination of heating and grinding-pressing cycles of disks containing alkali halides as diluting agents. |
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