Title
Kinetic study of the thermal transformation of limonite to hematite by X-ray diffraction, μ-Raman and Mössbauer spectroscopy
Date Issued
01 November 2011
Access level
metadata only access
Resource Type
journal article
Author(s)
Instituto de Ciencia de Materiales de Sevilla
Abstract
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. © 2011 Springer Science+Business Media B.V.
Start page
113
End page
118
Volume
203
Issue
March 1
Language
English
OCDE Knowledge area
Física atómica, molecular y química
Física de partículas, Campos de la Física
Subjects
Scopus EID
2-s2.0-81555198429
Source
Hyperfine Interactions
ISSN of the container
03043843
Sponsor(s)
Acknowledgements The authors thank to the Academic Vice Rectorate and Faculty of Physical Sciences at San Marcos University in Peru for its economical support to the work. To Materials Science Institute of Sevilla – CSIC – Univ. Sevilla by the in-situ measurments of XRD and μ-Raman. Finally, JC González thanks to the Spanish Scientific Research Council (CSIC) for his JAE-Doc contract (2009-2012) at the ICMSE-CSIC-US. (Spain).
Sources of information:
Directorio de Producción Científica
Scopus