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Formation of nanocrystalline magnetite by thermal decomposition of iron choline citrate

Thermal decomposition of iron choline citrate (C33H57Fe2N3O24) has been investigated using differential thermal analysis, X-ray powder diffraction, Fourier transform infrared and 57Fe Mössbauer spectroscopies. The starting compound was heated in a furnace at selected temperatures between room temperature and 460 oC, and cooled down afterwards either by quenching in bidistilled water or by cooling in air. Final decomposition products were iron oxides Fe3O4 (magnetite) and  -Fe2O3 (hematite). In all samples quenched in bidistilled water magnetite was found to be a dominant crystalline phase. Self-propagating burning of iron choline citrate in air was observed. The unit-cell parameter of obtained magnetite decreased gradually with the increase in temperature of thermal treatment of the starting compound regardless of the cooling procedure. Crystallite size of magnetite varied from 10(1) to 21(2) nm, whereas the crystallite size of hematite varied between 25(2) and 39(3) nm. FT-IR spectra showed a significant amount of organic fraction in the samples containing magnetite as a dominant crystalline phase. In absence (or presence of a small quantity) of organic phase, a transformation of magnetite to hematite occurred. Mössbauer spectrum of iron choline citrate at RT showed a single line with pronounced broadening. On heating the starting compound at 270 oC and quenching in bidistilled water the quadrupole doublet was recorded at RT. This quadrupole doublet was ascribed to amorphous iron(III)-(hydrous) oxide. For samples thermaly treated at higher temperatures Mössbauer spectroscopy showed magnetite and hematite. Mössbauer spectra also showed substoichiometric magnetite, Fe3-xO4, which was very pronounced in samples produced at the highest temperatures, and this was in agreement with XRD investigations.

Oxide materials; Chemical synthesis; X-ray diffraction; Mossbauer spectroscopy; FT-IR spectroscopy; DTA

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