Destruction of fayalite and formation of iron and iron hydride at high hydrogen pressures

Destruction of fayalite and formation of iron and iron hydride at high hydrogen pressures

Thermal stability of fayalite (Fe 2 SiO 4 ) is studied at hydrogen pressures up to 7.5 GPa and temperatures up to 400 °C. Powder samples of Fe 2 SiO 4 were exposed to a hydrogen or deuterium atmosphere for 24 h in the Toroid-type apparatus at pre-selected pressures and temperatures followed by quenc...

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Bibliographic Details
Published in:Physics and chemistry of minerals Vol. 46; no. 8; pp. 743 - 749
Main Authors: Efimchenko, Vadim S., Barkovskii, Nicolay V., Fedotov, Vladimir K., Meletov, Konstantin P., Chernyak, Vladimir M., Khryapin, Kirill I.
Format: Journal Article
Language:English
Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-09-2019
Springer Nature B.V
Subjects:
Chemical composition
Crystallography and Scattering Methods
Decomposition
Deuteration
Deuterium
Earth and Environmental Science
Earth Sciences
Fayalite
Geochemistry
High temperature
Hydrogen
Hydrogen storage
Iron
Liquid nitrogen
Mass spectroscopy
Mineral Resources
Mineralogy
Organic chemistry
Original Paper
Pressure
Quadrupoles
Raman spectroscopy
Silica
Silicon dioxide
Spectrum analysis
Thermal stability
X-ray diffraction
X-ray spectroscopy
Fayalite
Hydrogen
Silica
Iron hydride
Decomposition reaction
High pressure
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Summary:Thermal stability of fayalite (Fe 2 SiO 4 ) is studied at hydrogen pressures up to 7.5 GPa and temperatures up to 400 °C. Powder samples of Fe 2 SiO 4 were exposed to a hydrogen or deuterium atmosphere for 24 h in the Toroid-type apparatus at pre-selected pressures and temperatures followed by quenching to the temperature of liquid nitrogen. The phase and chemical compositions of the quenched samples were examined by energy-dispersive X-ray spectroscopy, X-ray diffraction and Raman spectroscopy at ambient pressure. The chemical composition of volatile products was studied by quadrupole mass spectroscopy in the course of heating from − 196 to 20 °C in a pre-evacuated quartz tube. In these experiments, deuterated samples were used to be sure that the detected compounds could only be formed in the reaction of fayalite with the high-pressure D 2 gas. The obtained data allowed us to construct the line of thermal stability of fayalite at hydrogen pressures up to 7.5 GPa. The decomposition temperature of fayalite was proved to nonlinearly decrease from ~ 375 °C at the pressures P H2  = 1.4–2.8 GPa to ~ 175 °C at P H2  = 7.5 GPa. At higher temperatures, fayalite fully decomposed to a mixture of silica, water and metallic Fe or FeH depending on the pressure and temperatures of the hydrogenation.
ISSN:0342-1791
1432-2021
DOI:10.1007/s00269-019-01035-z