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Title: From iron(III) precursor to magnetite and vice versa

Abstract

The syntheses of nanosize magnetite particles by wet-chemical oxidation of Fe{sup 2+} have been extensively investigated. In the present investigation the nanosize magnetite particles were synthesised without using the Fe(II) precursor. This was achieved by {gamma}-irradiation of water-in-oil microemulsion containing only the Fe(III) precursor. The corresponding phase transformations were monitored. Microemulsions (pH {approx} 12.5) were {gamma}-irradiated at a relatively high dose rate of {approx}22 kGy/h. Upon 1 h of {gamma}-irradiation the XRD pattern of the precipitate showed goethite and unidentified low-intensity peaks. Upon 6 h of {gamma}-irradiation, reductive conditions were achieved and substoichiometric magnetite ({approx}Fe{sub 2.71}O{sub 4}) particles with insignificant amount of goethite particles found in the precipitate. Hydrated electrons (e{sub aq}{sup -}), organic radicals and hydrogen gas as radiolytic products were responsible for the reductive dissolution of iron oxide in the microemulsion and the reduction Fe{sup 3+} {yields} Fe{sup 2+}. Upon 18 h of {gamma}-irradiation the precipitate exhibited dual behaviour, it was a more oxidised product than the precipitate obtained after 6 h of {gamma}-irradiation, but it contained magnetite particles in a more reduced form ({approx}Fe{sub 2.93}O{sub 4}). It was presumed that the reduction and oxidation processes existed as concurrent competitive processes in the microemulsion. After 18 h ofmore » {gamma}-irradiation the pH of the medium shifted from the alkaline to the acidic range. The high dose rate of {approx}22 kGy/h was directly responsible for this shift to the acidic range. At a slightly acidic pH a further reduction of Fe{sup 3+} {yields} Fe{sup 2+} resulted in the formation of more stoichiometric magnetite particles, whereas the oxidation conditions in the acidic medium permitted the oxidation Fe{sup 2+} {yields} Fe{sup 3+}. The Fe{sup 3+} was much less soluble in the acidic medium and it hydrolysed and recrystallised as goethite. The {gamma}-irradiation of the microemulsion for 25 h at a lower dose rate of 16 kGy/h produced pure substoichiometric nanosize magnetite particles of about 25 nm in size and with the stoichiometry of Fe{sub 2.83}O{sub 4}.« less

Authors:
 [1]; ;  [1]
  1. Division of Materials Chemistry, Ruder Boskovic Institute, P.O. Box 180, HR-10002 Zagreb (Croatia)
Publication Date:
OSTI Identifier:
22029752
Resource Type:
Journal Article
Journal Name:
Materials Research Bulletin
Additional Journal Information:
Journal Volume: 44; Journal Issue: 10; Other Information: Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0025-5408
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DOSE RATES; ELECTRON MICROSCOPY; GAMMA RADIATION; GOETHITE; IRON IONS; IRRADIATION; MAGNETITE; MICROEMULSIONS; MOESSBAUER EFFECT; NANOSTRUCTURES; OXIDATION; PARTICLES; RADIOLYSIS; SYNTHESIS; X-RAY DIFFRACTION

Citation Formats

Gotic, M, Jurkin, T, and Music, S. From iron(III) precursor to magnetite and vice versa. United States: N. p., 2009. Web. doi:10.1016/J.MATERRESBULL.2009.06.002.
Gotic, M, Jurkin, T, & Music, S. From iron(III) precursor to magnetite and vice versa. United States. https://doi.org/10.1016/J.MATERRESBULL.2009.06.002
Gotic, M, Jurkin, T, and Music, S. 2009. "From iron(III) precursor to magnetite and vice versa". United States. https://doi.org/10.1016/J.MATERRESBULL.2009.06.002.
@article{osti_22029752,
title = {From iron(III) precursor to magnetite and vice versa},
author = {Gotic, M and Jurkin, T and Music, S},
abstractNote = {The syntheses of nanosize magnetite particles by wet-chemical oxidation of Fe{sup 2+} have been extensively investigated. In the present investigation the nanosize magnetite particles were synthesised without using the Fe(II) precursor. This was achieved by {gamma}-irradiation of water-in-oil microemulsion containing only the Fe(III) precursor. The corresponding phase transformations were monitored. Microemulsions (pH {approx} 12.5) were {gamma}-irradiated at a relatively high dose rate of {approx}22 kGy/h. Upon 1 h of {gamma}-irradiation the XRD pattern of the precipitate showed goethite and unidentified low-intensity peaks. Upon 6 h of {gamma}-irradiation, reductive conditions were achieved and substoichiometric magnetite ({approx}Fe{sub 2.71}O{sub 4}) particles with insignificant amount of goethite particles found in the precipitate. Hydrated electrons (e{sub aq}{sup -}), organic radicals and hydrogen gas as radiolytic products were responsible for the reductive dissolution of iron oxide in the microemulsion and the reduction Fe{sup 3+} {yields} Fe{sup 2+}. Upon 18 h of {gamma}-irradiation the precipitate exhibited dual behaviour, it was a more oxidised product than the precipitate obtained after 6 h of {gamma}-irradiation, but it contained magnetite particles in a more reduced form ({approx}Fe{sub 2.93}O{sub 4}). It was presumed that the reduction and oxidation processes existed as concurrent competitive processes in the microemulsion. After 18 h of {gamma}-irradiation the pH of the medium shifted from the alkaline to the acidic range. The high dose rate of {approx}22 kGy/h was directly responsible for this shift to the acidic range. At a slightly acidic pH a further reduction of Fe{sup 3+} {yields} Fe{sup 2+} resulted in the formation of more stoichiometric magnetite particles, whereas the oxidation conditions in the acidic medium permitted the oxidation Fe{sup 2+} {yields} Fe{sup 3+}. The Fe{sup 3+} was much less soluble in the acidic medium and it hydrolysed and recrystallised as goethite. The {gamma}-irradiation of the microemulsion for 25 h at a lower dose rate of 16 kGy/h produced pure substoichiometric nanosize magnetite particles of about 25 nm in size and with the stoichiometry of Fe{sub 2.83}O{sub 4}.},
doi = {10.1016/J.MATERRESBULL.2009.06.002},
url = {https://www.osti.gov/biblio/22029752}, journal = {Materials Research Bulletin},
issn = {0025-5408},
number = 10,
volume = 44,
place = {United States},
year = {Thu Oct 15 00:00:00 EDT 2009},
month = {Thu Oct 15 00:00:00 EDT 2009}
}