Chemical and microstructural properties of oxide phases obtained by forced hydrolysis of Fe3+ ions (CROSBI ID 85861)
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Podaci o odgovornosti
Musić, Svetozar ; Šarić, Ankica ; Nomura, Kiyoshi ; Popović, Stanko
engleski
Chemical and microstructural properties of oxide phases obtained by forced hydrolysis of Fe3+ ions
The chemical and microstructural properties of oxide phases obtained by forced hydrolysis of Fe ions at 90°C, were investigated using X-ray powder diffraction, Fourier transform infrared spectroscopy, 57Fe Mössbauer spectroscopy and transmission electron microscopy. Urotropin (hexamethylenetetramine) was used as a generator of OH ions. After 5 hours of the hydrolysis of 0.1 M Fe(NO3)3 solution in an acidic medium the RT Mössbauer spectrum showed a broad size distribution of a-FeOOH particles, while XRD showed the presence of an amorphous fraction and a-FeOOH. With a prolonged heating time a-FeOOH was transformed to a-Fe2O3 by a dissolution/reprecipitation mechanism. At the beginning of precipitation process the amorphous fraction increased with an increase of urotropin concentration and for 0.25 M urotropin the sample was completely amorphous, as shown by XRD. For the same sample RT Mössbauer spectrum showed a quadrupole doublet. After 3 and 5 hours of aging of the precipitation system in the presence of 0.1 M urotropin, traces of a-FeOOH were observed in the FT-IR spectra, while for 0.25 M urotropin FT- IR spectroscopy did not show any a-FeOOH content. For longer ageing times (7 and 21 days) of the precipitation systems mixtures of a-Fe2O3 and a- FeOOH were found and tendency of the a-FeOOH fraction to increase with an increase in the urotropin concentration was observed. A possible mechanism of crystallization of a-Fe2O3 and a- FeOOH from an amorphous phase in the near neutral pH region is discussed. The size and morphology of oxide particles depended strongly on the experimental conditions of their formation.
hydrolysis ; Fe3+ ions
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