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Title: The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites

Authors:
ORCiD logo; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NSFOTHER
OSTI Identifier:
1419881
Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemical Geology; Journal Volume: 479; Journal Issue: C
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Ling, Florence T., Post, Jeffrey E., Heaney, Peter J., and Ilton, Eugene S.. The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites. United States: N. p., 2018. Web. doi:10.1016/j.chemgeo.2018.01.011.
Ling, Florence T., Post, Jeffrey E., Heaney, Peter J., & Ilton, Eugene S.. The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites. United States. doi:10.1016/j.chemgeo.2018.01.011.
Ling, Florence T., Post, Jeffrey E., Heaney, Peter J., and Ilton, Eugene S.. 2018. "The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites". United States. doi:10.1016/j.chemgeo.2018.01.011.
@article{osti_1419881,
title = {The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites},
author = {Ling, Florence T. and Post, Jeffrey E. and Heaney, Peter J. and Ilton, Eugene S.},
abstractNote = {},
doi = {10.1016/j.chemgeo.2018.01.011},
journal = {Chemical Geology},
number = C,
volume = 479,
place = {United States},
year = 2018,
month = 2
}
  • The characterization of birnessite structures is particularly challenging for poorly crystalline materials of biogenic origin, and a determination of the relative concentrations of triclinic and hexagonal birnessite in a mixed assemblage has typically required synchrotron-based spectroscopy and diffraction approaches. In this study, Fourier-transform infrared spectroscopy (FTIR) is demonstrated to be capable of differentiating synthetic triclinic Na-birnessite and synthetic hexagonal H-birnessite. Furthermore, IR spectral deconvolution of peaks resulting from Mnsingle bondO lattice vibrations between 400 and 750 cm - 1 yield results comparable to those obtained by linear combination fitting of synchrotron X-ray absorption fine structure (EXAFS) data when applied tomore » known mixtures of triclinic and hexagonal birnessites. Density functional theory (DFT) calculations suggest that an infrared absorbance peak at ~ 1628 cm - 1 may be related to OH vibrations near vacancy sites. The integrated intensity of this peak may show sensitivity to vacancy concentrations in the Mn octahedral sheet for different birnessites.« less
  • An x-ray powder diffraction analysis at 5 K shows that the structure of Cu/sub 1.8/Mo/sub 6/S/sub 8/ in the superconducting state is a triclinic distorted version of the rhombohedral room temperature structure. The distortion is due to a clustering of the Cu atoms into pairs (d(Cu--Cu) =2.58 A) as the compound transforms at 270 K from the disordered high-temperature into the ordered low-temperature modification.
  • An analysis of available data shows that BE values for the 3d level of Mo oxides and the 4f values of W oxides are not linearly related to oxidation number because of an increased extra-atomic relaxation due to the presence of conduction electrons. These relaxation effects are neglected by Broclawik, Foti, and Smith. A reply by these authors discusses differences between the formal and the effective oxidation number.
  • The relationship between molybdenum oxidation state and iodine volatility in nuclear fuel was investigated using high-temperature Knudsen cell-mass spectroscopy. It was observed that the ratio of the intensities of molecular iodine ions I{sub 2}{sup +} and CsI{sup +} in the Knudsen cell-mass spectroscopic experiments can be used to investigate the iodine volatility in fuel under different conditions. The experiments show that the iodine volatility is similar in systems consisting of CsI alone, CsI/UO{sub 2}, and CsI/UO{sub 2}/MoO{sub x} (with molybdenum in oxidation states 0, 2, and 4). The iodine volatility is much higher, however, in CsI/UO{sub 2}/MoO{sub 3} systems (withmore » molybdenum in oxidation state = 6). The iodine volatility in the fuel increases significantly if oxidation of the molybdenum goes to the MoO{sub 3} stage. The increase in the iodine volatility is caused by the formation of elemental iodine from cesium iodide. It is concluded from these measurements that the oxidation of the fuel to the UO{sub 2.2} will substantially increase the volatilization of fission product iodine. An analysis of the literature data suggests that the enhanced iodine volatilization process may be initiated when the fuel is oxidized to UO{sub 2.02}.« less