Kinetic study of the thermal transformation of limonite to hematite by X-ray diffraction, μ-Raman and Mössbauer spectroscopy
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A kinetic study about the phase limonite (FeO(OH)-nH2O) was performed through X-ray diffraction, μ-Raman spectroscopy and Mössbauer spectroscopy. The oxide powder sample was extracted from Taraco district, Huancané province of Puno (Peru). X-ray diffraction identified the phase goethite as the main mineralogical component, and then the sample was subjected to in-situ heat treatment in the temperature range: 100 to 500°C in oxidizing (air) and inert (nitrogen) atmospheres. The goethite phase remains stable in this range: room temperature to 200°C. Between 200°C to 250°C there is a phase transition: α-Fe3 + O(OH) → α-Fe2O3, i.e., from goethite to hematite phase, taking as evidence the evolution of the diffraction profiles. At 200°C spectra shows the start of broadened magnetic component and it was adjusted through of a magnetic distribution giving a mean field of 38.6T and a relative area of 52.9%, which is a characteristic of goethite. Also, it is noticed the presence of a small amount of hematite with a mean field of 49.0T linked with a superparamagnetic broadened doublet of relative area of 47.1% where the domains of the particles have sizes smaller than 100 Å and it is evidence the superparamagnetic limit; i.e., the superparamagnetic effect tends toward a distribution of magnetic fields. Moreover, the Raman spectra of the in-situ thermal treatment, support the transition at 290°C through the transformation of characteristic bands of goethite to hematite phase at the frequency range from 200 to 1,800 cm − 1.
KeywordsLimonite X-ray diffraction μ-Raman spectroscopy Mössbauer spectroscopy
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- 1.Hurlbut, C.S., Cornelis, K.: Manual of Mineralogy, 20th edn. Wiley, ISBN 0-471-80580-7 (1985)Google Scholar
- 2.Palache, C., Berman, H., Frondel, C.: Dana‘s system of mineralogy, 7th edn., vol. I, pp. 527–534 (1944)Google Scholar
- 4.Bosio, V., Pogliani, C., Donati, E.: VI southern hemisphere on minerals technology. Río de Janeiro (Brasil) 2, 405–409 (2001)Google Scholar
- 6.Palacios, P.R., Bustamante, A.B., Gonzáles, J.C.: Rev. Investig. Fís. 13, 1–6. ISBN 1605–7744 (2010)Google Scholar