Kinetics of Fe-oxidation/deprotonation process in Fe-rich phlogopite under isothermal conditions

Zema, Michele; Ventruti, Gennaro; Lacalamita, Maria; Scordari, Fernando

doi:10.2138/am.2010.3523

Cited by 17 publications

(13 citation statements)

References 44 publications

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“…But for solidstate reactions it is rather improbable. However, recently published data about the kinetics of Fe-oxidation/deprotonation in iron-rich phlogopites suggest a single rate-determining step for a narrow temperature range (Zema et al, 2010).…”

Section: Data Extractionmentioning

confidence: 99%

Dehydroxylation kinetics of lizardite

Trittschack¹,

Grobéty²

2012

ejm

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Abstract:The thermally induced dehydroxylation of lizardite and its phase transformation to forsterite were studied by hightemperature X-ray diffraction (HT-XRD), thermogravimetry (TGA) and Fourier-transformed infrared spectroscopy (FTIR). Primary sample characteristics like chemical composition and crystallographical structure were determined by combined (HR)TEM-EDX, electron-microprobe analyses (EMPA) as well as conventional X-ray diffraction (XRD). Isothermal HT-XRD and non-isothermal TGA data were treated with the classical Avrami-Erofe'ev method and more advanced isoconversional methods in order to obtain kinetic data of a multi-step decomposition reaction. A highly precise activation energy E a versus reaction progress (a) dependency based on non-isothermal TGA data of lizardite is provided and associated mechanisms are discussed. Here, the main focus is on recently published ab initio calculations from the phase transformation of other phyllosilicates. Moreover, the calculated overall apparent activation energy is compared with discrepant data from the literature and discussed. Especially, the usability of overall activation energies of multi-step decomposition reactions is critically discussed. The presented and discussed reaction steps of water formation from different hydroxyl species in lizardite can be used to improve ab initio calculations, especially the pre-selection of reacting hydroxyl species in hydrous sheet like minerals.

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Section: Data Extractionmentioning

confidence: 99%

Dehydroxylation kinetics of lizardite

Trittschack¹,

Grobéty²

2012

ejm

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“…In the present study, we compare phlogopite with muscovite, a dioctahedral mica whose O-K motions and OH librations show strong variation at temperatures far below dehydroxylation (Zhang et al 2010a) so as to gain better insights into the characteristics of phonon vibrations and OH absorption in micas on approaching dehydroxylation and the dehydroxylation mechanism. For phlogopite, it was proposed that dehydroxylation is associated with Fe oxidation (e.g., Vedder and Wilkins 1969;Zema et al 2010). Second, the present study aims to investigate the possible formation and diffusion of H 2 O during dehydroxylation, which has long been assumed or proposed as the mechanism of dehydroxylation in phyllosilicates (please see Zhang et al 2010b for more details and reviews).…”

Section: Introductionmentioning

confidence: 97%

Optical phonons, OH vibrations, and structural modifications of phlogopite at high temperatures: An in-situ infrared spectroscopic study

Zhang

Tarantino

et al. 2016

American Mineralogist

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The thermal behavior of optical phonons and OH vibrations of phlogopite (a trioctahedral mica) was examined at temperatures up to 1000 K using in situ infrared spectroscopy. The results showed that with increasing temperature, O-K bands in phlogopite exhibited a relatively strong variation in frequency in a manner similar to those in muscovite. The work revealed that different types of OH bands (fundamentals and combinations) have very different thermal behavior or temperature dependence, and their absorption coefficients are commonly not constant on heating. OH combination bands that are associated with summation processes of multi-phonon interactions commonly show a decrease in their intensities on heating, but in contrast combination bands due to difference processes generally exhibit an increase. This means that temperature dependencies of their absorption coefficients need to be considered when using the Beer-Lambert law to determine or estimate OH contents or hydrogen concentrations at high temperatures. The results showed a structural anomaly associated with a discontinuity in the temperature derivative of the wavenumber of Al-O and Si-O vibrations and O-H stretching near 600 K. However, framework-related phonon modes in the FIR and MIR regions do not suggest a break of the original monoclinic structural symmetry in the investigated temperature region. The complex changes are attributed to temperature-induced alteration of local configuration involving TO 4 tetrahedra and a possible change of the orientation of OH dipoles, in addition to a previously reported distortion of MO 6 octahedra. Increasing temperature to 1000 K also causes partial dehydroxylation, as evidenced by the disappearance of the OH band near 3623 cm -1 and the decrease in OH band height and area of other OH bands. The study did not record the formation of H 2 O inside phlogopite as a result of partial dehydroxylation. The work offers new data and findings that have important implications in understanding the complex structural modifications and the behavior of phonon modes and the thermal stability of hydroxyls on approaching the dehydroxylation, as well as the way hydrogen is released from micas at high temperatures. Our data also show that phologpite becomes less transparent with increasing temperature suggesting a change of radiative properties and ability to transmit heat, which could be of interest for modeling thermal-transmission in crustal rocks.

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“…Micas (phyllosilicates) are another group for which iron oxidation-dehydroxylation is widely registered at elevated temperatures, for example: Fe-rich phlogopite (Russell & Guggenheim, 1999;Chon et al, 2006;Ventruti et al, 2008;Zema et al, 2010), illite (Murad & Wagner, 1996), biotite (Gü ttler et al, 1989) and vermiculite (Veith, 1974). However, the cation migration in octahedral sheets was scarcely described either due to the experimental difficulties or its rarity.…”

Section: Brief Comparison With Micas Amphiboles and Tourmalinesmentioning

confidence: 99%

High-temperature Fe oxidation coupled with redistribution of framework cations in lobanovite, K₂Na(Fe²⁺₄Mg₂Na)Ti₂(Si₄O₁₂)₂O₂(OH)₄– the first titanosilicate case

Zhitova

Zolotarev

Hawthorne

et al. 2019

Acta Crystallogr B Struct Sci Cryst Eng Mater

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OH) 4 , was studied using in situ powder X-ray diffraction in the temperature range 25-1000 C and ex situ single-crystal X-ray diffraction of 17 crystals quenched from different temperatures. HT iron oxidation associated with dehydroxylation starts at 450 C, similar to other ferrous-hydroxy-rich heterophyllosilicates such as astrophyllite and bafertisite. A prominent feature of lobanovite HT crystal chemistry is the redistribution of Fe and Mg+Mn cations over the M(2), M(3), M(4) sites of the octahedral (O) layer that accompanies iron oxidation and dehydroxylation. This HT redistribution of cations has not been observed in titanosilicates until now, and seems to be triggered by the need to maintain bond strengths at the apical oxygen atom of the TiO 5 pyramid in the heteropolyhedral (H) layer during oxidationdehydroxylation. Comparison of the HT behaviour of lobanovite with fivecoordinated Ti and astrophyllite with six-coordinated Ti shows that the geometry of the Ti polyhedron plays a key role in the HT behaviour of heterophyllosilicates. The thermal expansion, geometrical changes and redistribution of site occupancies which occur in lobanovite under increasing temperature are reported. A brief discussion is given of minerals in which the cation ordering (usually for Fe and Mg) occurs together with iron oxidationdehydroxylation at elevated temperatures: micas, amphiboles and tourmalines. Now this list is expanded by the inclusion of titanosilicate minerals.

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Kinetics of Fe-oxidation/deprotonation process in Fe-rich phlogopite under isothermal conditions

Cited by 17 publications

References 44 publications

Dehydroxylation kinetics of lizardite

Dehydroxylation kinetics of lizardite

Optical phonons, OH vibrations, and structural modifications of phlogopite at high temperatures: An in-situ infrared spectroscopic study

High-temperature Fe oxidation coupled with redistribution of framework cations in lobanovite, K₂Na(Fe²⁺₄Mg₂Na)Ti₂(Si₄O₁₂)₂O₂(OH)₄– the first titanosilicate case

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Kinetics of Fe-oxidation/deprotonation process in Fe-rich phlogopite under isothermal conditions

Cited by 17 publications

References 44 publications

Dehydroxylation kinetics of lizardite

Dehydroxylation kinetics of lizardite

Optical phonons, OH vibrations, and structural modifications of phlogopite at high temperatures: An in-situ infrared spectroscopic study

High-temperature Fe oxidation coupled with redistribution of framework cations in lobanovite, K2Na(Fe2+4Mg2Na)Ti2(Si4O12)2O2(OH)4– the first titanosilicate case

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High-temperature Fe oxidation coupled with redistribution of framework cations in lobanovite, K₂Na(Fe²⁺₄Mg₂Na)Ti₂(Si₄O₁₂)₂O₂(OH)₄– the first titanosilicate case