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Title
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Mössbauer characterisation of the products resulting from hydrothermal treatments of nanosized goethite
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Author
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Abstract
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| Batches of poorly crystalline (GPC) and relatively well crystalline (GNL) goethite, alpha-FeOOH, powders have been suspended in a neutral aqueous medium and heated for three days in a pressure bomb at various temperatures between 100 and 300 degrees C. The parent acid resulting products have been characterised by thermogravimetric analyses, X-ray diffraction, BET surface-area measurements, transmission electron microscopy and Fe-57 Mossbauer spectroscopy. While the goethite particles of GNL are not affected by the treatments at up to 275 degrees C, those of GPC initially grow with increasing heating temperature up to similar to 200 degrees C and subsequently become smaller with further increase of the temperature. Above 250 degrees C, GPC produces a mixture of hematite, alpha-Fe2O3, and maghemite, gamma-Fe2O3. The presence of the latter phase is particularly obvious from the external-field Mossbauer spectrum. After being treated at 300 degrees C, both goethites have completely converted to hematite. The morphology of the parent goethite has no marked effect on the final hematite phase. (C)1999 Acta Metallurgica Inc. |
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Language
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English
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Source (journal)
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Nanostructured materials. - New York
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Publication
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New York
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1999
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ISSN
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0965-9773
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DOI
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10.1016/S0965-9773(99)00334-7
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Volume/pages
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11
:4
(1999)
, p. 493-504
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ISI
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000082298400008
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Full text (Publisher's DOI)
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Full text (publisher's version - intranet only)
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