Full metadata
Title
Possible Control of Redox Conditions in the Laser-Heated Diamond Anvil Cell
Description
The redox conditions of Earth have been changing since proto-Earth’s accretion from the solar nebula. These changes have influenced the distribution and partitioning of volatile elements between the atmosphere and the mantle (Righter et al., 2020; Stagno and Fei, 2020. Though oxygen fugacity fO2 is arguably not the main factor for phase stability at certain pressure-temperature conditions (McCammon, 2005), it can influence which phases are stable, especially within a closed system such as the ones presented in this study. Despite the importance of controlling fO2 for interpreting the history of planetary bodies, there have been no methods to control the redox conditions in the laser-heated diamond anvil cell (LHDAC). This thesis has examined the feasibility for controlling redox conditions in the LHDAC using a mixture of Ar and H2 for insulation media. The experiments of this study were carried out at the GSECARS sector of the Advanced Photon Source at Argonne National Laboratory. In this study, α-Fe2O3 (hematite), ε-FeOOH (CaCl2-type), and Fe3O4 (magnetite) starting materials were used for probing changes of redox conditions. Experiments were also conducted with a pure Ar-medium for ε-FeOOH at the same pressure-temperature conditions of the hydrogen-bearing medium in order to provide a reference point for data which has uncontrolled redox conditions for an initially Fe(2+)-free material. The results for the ε-FeOOH starting material in Ar show transformation to ι-Fe2O3 (Rh2O3(II)-type) at 30.0 GPa and 1900 K, while in Ar + H2 it transformed to Fe5O7 with minor FeH (dhcp) at 30.0 GPa and 1850 K. For α-Fe2O3 in Ar + H2, it was found to convert to ε-FeOOH, Fe5O7, Fe5O6, and FeH (dhcp) at 36.5 GPa and 1800 K. For Fe3O4 in Ar + H2, it was found to convert to Fe4O5 (CaFe3O5-type), Fe5O6, and minor FeH (fcc) at 26.0 GPa and 1800 K. These results demonstrate that H in an Ar medium can promote the conversion of some Fe(3+) to Fe(2+) and Fe(0). However, the formation of ε-FeOOH in the α-Fe2O3 starting material suggests that H may participate in the chemical reaction of iron oxides.
Date Created
2021
Contributors
- Kulka, Britany Lynn (Author)
- Shim, Sang-Heon (Thesis advisor)
- Sharp, Thomas (Committee member)
- Leinenweber, Kurt (Committee member)
- Hervig, Richard (Committee member)
- Arizona State University (Publisher)
Topical Subject
Resource Type
Extent
58 pages
Language
eng
Copyright Statement
In Copyright
Primary Member of
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.2.N.161753
Level of coding
minimal
Cataloging Standards
Note
Partial requirement for: M.S., Arizona State University, 2021
Field of study: Geological Sciences
System Created
- 2021-11-16 03:43:55
System Modified
- 2021-11-30 12:51:28
- 2 years 11 months ago
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