Kinetics and mechanism of dehydroxylation of crocidolite

Clark, Miles; Freeman, A. G.

doi:10.1039/tf9676302051

Cited by 14 publications

(5 citation statements)

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“…1. Similar curves were observed by Clark and Freeman (1967) who studied the thermal decomposition of crocidolite, an Fe-bearing amphibole known as blue asbestos. Figure 2 shows the fraction of tremolite reacted plotted versus time normalized to the time required for 50% decomposition of the tremolite (i.e., t/t 0.5 ).…”

Section: Tremolite Decomposition Experimentssupporting

confidence: 73%

Water on Venus: New Insights from Tremolite Decomposition

Johnson¹

2000

Icarus

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Section: Tremolite Decomposition Experimentssupporting

confidence: 73%

Water on Venus: New Insights from Tremolite Decomposition

Johnson¹

2000

Icarus

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“…Hence, the following diffusion controlled models (Clark andFreeman 1967 andBrindley andLemaitre 1987) were considered for analysis: One-dimensional diffusion:…”

Section: Dehydroxylation Kinetics Mechanismmentioning

confidence: 99%

FTIR spectra of hydroxyls and dehydroxylation kinetics mechanism in montmorillonite

Malhotra

Ogloza

1989

Phys Chem Minerals

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Abstract. The application of Fourier transform infrared (FTIR) spectroscopy to the analysis of the hydroxyl groups bands' intensities of montmorillonite from Texas shows four regions of intensity loss rate for thermally shocked samples at 290 < T< 1100 K for 24 h. The first three regions are associated with the dehydroxylation process; while the fourth region suggests the loss of the remaining (~ 10%) hydroxyls via thermal dissociation into hydrogen atoms and oxygen centers. The dehydroxylation process appears to be homogeneous with adjacent trans OH ions interacting to form H20 molecules below the hexagonal hole or cavity. The vibrational analysis of the stretching and bending modes of water and hydroxyl groups at 290< T<553 K indicates not only that water is desorbed in this range, resulting in the perturbation of the octahedral hydroxyl structure due to the close approach of exchangeable cations to the hexagonal holes, but also that surface hydroxyls and A1Fe3+-OH groups are dehydroxylated. AT 553 673 K. However, what is surprising is the persistence of very weak water stretching (~3470 cm -1) and bending (~1628 cm -1) vibrations at 553

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“…A particularly important issue in the crystal chemistry of these minerals is the stability of Fe-bearing species, because their oxidation processes have a paramount importance in a wide spectrum of fields, including geology and geophysics, but also materials science and toxicology 6,7 . Early ex situ work 8,9 have revealed that oxidation of C Fe is intrinsically coupled with a loss of hydrogen from the hydroxyl group, in the presence of external oxygen ( ex O 2 ), according to the reaction:…”

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confidence: 99%

Atomistic insight into lithospheric conductivity revealed by phonon–electron excitations in hydrous iron-bearing silicates

et al. 2021

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Amphiboles are essential components of the continental crust and subduction zones showing anomalous anisotropic conductivity. Rock properties depend on the physical properties of their constituent minerals, which in turn depend on the crystal phonon and electron density of states. Here, to address the atomic-scale mechanism of the peculiar rock conductivity, we applied in situ temperature-dependent Raman spectroscopy, sensitive to both phonon and electron states, to Fe2+-rich amphiboles. The observed anisotropic resonance Raman scattering at elevated temperatures, in combination with density-functional-theory modelling, reveals a direction-dependent formation of mobile polarons associated with coupled FeO6 phonons and electron transitions. Hence, temperature-activated electron-phonon excitations in hydrous iron-bearing chain and layered silicates are the atomistic source of anisotropic lithospheric conductivity. Furthermore, reversible delocalization of H+ occurs at similar temperatures even in a reducing atmosphere. The occurrence of either type of charge carriers does not require initial mixed-valence state of iron or high oxygen fugacity in the system.

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Kinetics and mechanism of dehydroxylation of crocidolite

Abstract: The kinetics of dehydroxylation of crocidolite have been studied in Z)CICUO. The kinetic data may be interpreted in terms of a diffusion-controlled reaction based on radial diffusion out of a cylinder. The activation energy for the process is 49 kcal/mole.

Cited by 14 publications

References 0 publications

Water on Venus: New Insights from Tremolite Decomposition

Water on Venus: New Insights from Tremolite Decomposition

FTIR spectra of hydroxyls and dehydroxylation kinetics mechanism in montmorillonite

Atomistic insight into lithospheric conductivity revealed by phonon–electron excitations in hydrous iron-bearing silicates

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