Mössbauer study of transformation mechanism of Fe cations in olivine after thermal treatments in air (original) (raw)
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Fe3+ distribution in oxidized olivine: A synchrotron micro-XANES study
2000
Synchrotron micro-XANES spectroscopy (SmX) is used to examine the amount and distribution of Fe 2+ and Fe 3+ in five samples of fayalite previously studied by Mössbauer spectroscopy. Rockport fayalite is homogeneous and the Fe in it is completely reduced. Olivine from Qianan is almost completely oxidized, and probably contains finely intergrown silica, laihunite, and hematite with hematite predominating. Pantelleria
Mössbauer Spectroscopy of Synthetic Olivine across the Mg-Fe Solid Solution
2011
My undying gratitude to Darby Dyar for her experience and support (emotional and financial) throughout this project. She introduced me to the fascinating world of Mössbauer spectroscopy and has taught me absolute necessity for unbiased scientific integrity. She is a true scientist and an amazing woman. Thank you to my family for supporting my scholastic whims. Thank you to Yarrow Rothstein, Claire Bendersky, Kylie Hanify, and Jerry Marchand for helping me change what seemed like an unending line of samples. I thank Catrina Hamilton-Drager and Mike Jercinovic for reviewing my thesis and hearing my defense. I am very grateful to Eddy De Grave, Toon Van Alboom, and David Agresti for their constant coaching on the underlying physics of this technique. And I am incredibly grateful to Donald Lindsley and Olwyn Menzies for the synthetic olivine samples that I was able to study.
Journal of Metastable and Nanocrystalline Materials, 2004
57 Fe Mössbauer spectroscopy is demonstrated as an effective tool in the identification, magnetic and structural characterization of iron(III) oxides formed by thermally induced oxidative decomposition of FeC 2 O 4 ⋅2H 2 O and by the secondary crystallization of amorphous Fe 2 O 3 nanopowder. AFM measurements revealed that the primary amorphous nanoparticles are between 1 and 3 nm, in accordance with the large surface area of 250 m 2 /g as determined by BET analysis. The temperature depended Mössbauer measurements of amorphous Fe 2 O 3 showed the magnetic transition temperature lower than 70 K with the sharp evolution of the spectral lines between 53 and 76 K as typical for ultrafine and strongly interacted particles. As the primary crystallization product at low temperatures, γ-Fe 2 O 3 (maghemite) was identified by XRD. The broad distribution of magnetic fields in Mössbauer spectra illustrates the broad size distribution of maghemite nanoparticles. The thermally stable α-Fe 2 O 3 (hematite) can be produced by the direct crystallization of amorphous phase at higher temperatures or by the structural transformation of the primarily formed maghemite at lower temperatures. Particles of hematite formed at 200 °C reveal the Morin transition temperature suppressed below 20 K corresponding to the size about 20 nm.
Mossbauer Study of Transformation of Fe Cations during Thermal Treatment of Glauconite in Air
Mossbauer Spectroscopy in Materials Science - 2012, 2012
Thermal decomposition of glauconite in air was studied by optical microscopy, thermal analysis, X-ray diffraction, and Mössbauer spectroscopy. The glauconite structure keeps preserved during thermal treatment up to 800 °C; however, simultaneously, a progressive transformation of Fe 2+ and Fe 3+ ions in glauconite structure and water leaving the crystal structure are both observed inducing the symmetry lowering of the iron octahedral positions. The destruction of glauconite structure begins after heating at 900 °C and becomes more intensive with an increase in the treatment temperature. Simultaneously, with the glauconite structure destruction, iron leaving the glauconite structure oxidizes to γ-Fe 2 O 3 , which transforms to α-Fe 2 O 3 .
Phase transformation characterization of olivine subjected to high temperature in air
Ceramics International, 2013
Olivine is one of the well-suited materials for fluidized bed reactor technology. After calcination at high temperature, olivine undergoes phase transformations resulting in dehydration and oxidation of fayalite to hematite and magnetite. The transformation mechanisms of olivine subjected to a calcination process at 1400 1C for 4 h are studied. Calcined olivine is characterized by X-Ray Diffraction (XRD), in situ XRD at varying temperatures and Raman spectroscopy. This paper explains the contribution of Raman spectroscopy to the study of iron oxide with regard to XRD. The heterogeneous distribution of hematite, magnetite and forsterite in the calcined material is exhibited by Raman mapping.
Characterization of structure of Fe-species in Fe-ferrierite using Mössbauer spectroscopy
Czechoslovak Journal of Physics, 2006
The aim of this article is to describe the structure of Fe species of catalysts of Feferrierite using Mössbauer spectroscopy in situ measurements. It was possible to describe the dehydration procedure and the redox behaviour of the studied catalysts in the redox cycles, where O2 and N2O were used for the oxidation. The results showed that the experimental arrangement is suitable for the description of Fe-species of the Fe-zeolites structures.
The effect of oxidation on the mineralogy and magnetic properties of olivine
American Mineralogist, 2019
Although nucleation of magnetite and/or hematite along dislocations upon oxidation of olivine has been observed by many workers, the effect of oxidation on the magnetic properties of the sample with specific mineralogical alterations has not been studied. Therefore, we investigate this problem using a set of time series 1 bar oxidation experiments at °C and 900 °C. Results show rapid olivine oxidation and alteration at both 600 and 900 °C, forming magnetite and hematite associated with a change from paramagnetic to ferromagnetic behavior after oxidation. Magnetite and hematite nucleate along dislocations and impurities in the crystal structure, along with surface coatings and within cracks in the crystals. Fresh, unaltered mantle xenoliths containing magnetite have been interpreted as having formed in cold tectonic regimes in the mantle, rather than through oxidation during or after ascent. Mantle xenoliths rapidly ascend through the mantle with estimates of ascent of up to 90 km/hour (3 GPa/hour) based on the diffusion profile of water in mantle olivine. The rates correspond to xenoliths ascending through the mantle over hours and not days or weeks. Our results show that olivine oxidation and alteration can occur in days to weeks at 600 °C and within minutes at 900 °C. Therefore, if the xenolithic material is transported to the surface in a cold magma (at temperatures ≤600 °C), then the time scale of ascent is likely not long enough for oxidation to cause magnetite formation or a ferromagnetic signature to occur. However, if the material is transported in a hot oxidized basaltic magma (with temperatures ≥900 °C), then oxidation can cause magnetite formation and a ferromagnetic signature.
ChemInform, 2002
Structural and magnetic properties, methods of synthesis, and applications of seven iron-(III) oxide polymorphs, including rare beta, epsilon, amorphous, and high-pressure forms, are reviewed. Thermal transformations resulting in the formation of iron oxides are classified according to different parameters, and their mechanisms are discussed. 57 Fe Mössbauer spectroscopy is presented as a powerful tool for the identification, distinction, and characterization of individual polymorphs. The advantages of Mössbauer spectroscopy are demonstrated with two examples related to the study of the thermally induced solid-state reactions of Fe 2 (SO 4 ) 3 .