Uranium Speciation in Glass Corrosion Layers: an XAFS Study

1996 ◽  
Vol 465 ◽  
Author(s):  
Bruce M. Biwer ◽  
L. Soderholm ◽  
R. B. Greegort ◽  
F. W. Lytle
Keyword(s):  
Corrosion Layer ◽  
Borosilicate Glasses ◽  
Absorption Data ◽  
X Ray ◽  
Surface Sensitivity ◽  
Glass Corrosion ◽  
Uranium Speciation ◽  
Before And After ◽  
X Ray Absorption ◽  
Leaching Surface

ABSTRACTUranium L3 X-ray absorption data were obtained from two borosilicate glasses, which are considered as models for radioactive wasteforms, both before and after leaching. Surface sensitivity to uranium speciation was attained by a novel application of simultaneous fluorescence and electron-yield detection. Changes in speciation are clearly discernible, from U(VI) in the bulk to (UO2)2+-uranyl in the corrosion layer. The uranium concentrations within the corrosion layer also show variations with leaching times that can be determined from the data.

SIGMAL: A Program for Calculating L-Shell lonization Cross-Sections

1981 ◽  
Vol 39 ◽  
pp. 198-199 ◽  
Author(s):  
R.F. Egerton
Keyword(s):  
Cross Sections ◽  
Fortran Program ◽  
Absorption Data ◽  
X Ray ◽  
Atomic Electrons ◽  
Energy Dependent ◽  
Hydrogenic Model ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Shell Ionization

SIGMAL is a short (∼ 100-line) Fortran program designed to rapidly compute cross-sections for L-shell ionization, particularly the partial crosssections required in quantitative electron energy-loss microanalysis. The program is based on a hydrogenic model, the L1 and L23 subshells being represented by scaled Coulombic wave functions, which allows the generalized oscillator strength (GOS) to be expressed analytically. In this basic form, the model predicts too large a cross-section at energies near to the ionization edge (see Fig. 1), due mainly to the fact that the screening effect of the atomic electrons is assumed constant over the L-shell region. This can be remedied by applying an energy-dependent correction to the GOS or to the effective nuclear charge, resulting in much closer agreement with experimental X-ray absorption data and with more sophisticated calculations (see Fig. 1 ).

Combined TDPAC and EXAFS Study of InPt/FER Catalysts

2000 ◽  
Vol 55 (1-2) ◽  
pp. 327-330 ◽  
Author(s):  
J. M. Ramallo-López ◽  
F. G. Requejo ◽  
A. G. Bibiloni ◽  
M. Rentería ◽  
L. Gutierrez ◽  
...  
Keyword(s):  
Perturbed Angular Correlation ◽  
Local Environment ◽  
X Ray ◽  
Time Differential ◽  
Before And After ◽  
Nuclear Quadrupole Moment ◽  
Exafs Study ◽  
Nuclear Quadrupole ◽  
X Ray Absorption ◽  
Asymmetry Parameters

Time Differential Perturbed Angular Correlation (TDPAC) experiments using 111In as probe were performed in order to determine the nature of In-sites in In-ferrierite (In/FER), before and after the incorporation of Pt through the hyperfine interaction between the nuclear quadrupole moment of the probe's nucleus and the extranuclear electric field gradient (EFG). Extended X-ray Absorption Fine Structure (EXAFS) measurements were performed to measure the absorbance above the Pt's LIII absorption edge in the transmission mode in order to determine the local environment of Pt atoms in Pt/FER and In Pt/FER catalysts. TDPAC spectra of 111In in In/FER and InPt/FER taken at 500°C in air indicated that there are no changes in the indium surroundings after the incorporation of Pt. Three sites were found for indium in both samples. Two of them correspond to the two sites of indium in ln2O3 and the third one is attributed to In in exchange sites of the zeolites. Their population, quadrupole frequencies and asymmetry parameters didn't change with the incorporation of Pt. EXAFS experiments showed similar near neighborhood Pt-0 distances and Pt coordination number in Pt/FER and In Pt/FER samples. There is no evidence of the presence of any In-Pt bimetallic entity in In Pt/FER catalyst.

A combined diffraction and EXAFS study of LaCoO3 and La0.5Sr0.5Co0.75Nb0.25O3 powders

2017 ◽  
Vol 32 (S1) ◽  
pp. S52-S55
Author(s):  
E. A. Efimova ◽  
V. V. Sikolenko ◽  
D. V. Karpinsky ◽  
I. O. Troyanchuk ◽  
S. Pascarelli ◽  
...  
Keyword(s):  
Spin State ◽  
State Transition ◽  
X Ray Diffraction ◽  
Absorption Data ◽  
X Ray ◽  
Bond Lengths ◽  
Structural Distortions ◽  
Spin State Transition ◽  
Local Range ◽  
X Ray Absorption

A combination of neutron diffraction, synchrotron X-ray diffraction, and high-resolution extended X-ray absorption fine structure measurements has been used to clarify the correlations between long- and local-range structural distortions across the spin-state transition in powders of LaCoO3 and La0.5Sr0.5Co0.75Nb0.25O3. The analysis of the diffraction data has revealed that the isotropic thermal parameters of Co–O bond abnormally increase below 100 K in both samples, while the temperature dependence of the average Co–O bond lengths is linear from 10 to 300 K. We also have found that the Co–O bond lengths are larger in La0.5Sr0.5Co0.75Nb0.25O3, as compared with the ones in LaCoO3. The X-ray absorption data showed an anomalous decrease of the Co–O bond lengths only for LaCoO3, in contrast to the bond length values obtained by diffraction. The structural anomalies observed by spectroscopy measurements are discussed in terms of the spin-state transition model.

Changing Np Redox Speciation in the Synchrotron Beam

2003 ◽  
Vol 802 ◽  
Author(s):  
S. Skanthakumar ◽  
D. Gorman-Lewis ◽  
A. Locock ◽  
M.-H. Chiang ◽  
M. P. Jensen ◽  
...  
Keyword(s):  
Metal Ion ◽  
Absorption Data ◽  
X Ray ◽  
Synchrotron Beam ◽  
Show Evidence ◽  
X Ray Absorption ◽  
Redox Speciation

ABSTRACTX-ray absorption data, obtained from Np(V) in two environmentally-related samples, show evidence of significant metal-ion reduction in the synchrotron beam. The data are presented and possible sources of reduction are discussed.

scholarly journals Wavelet investigation of La0.5Ca0.5CoO3−δ x-ray absorption data

2007 ◽  
Vol 101 (1) ◽  
pp. 014911 ◽  
Author(s):  
M. Sahnoun ◽  
C. Daul ◽  
O. Haas
Keyword(s):  
Absorption Data ◽  
X Ray ◽  
X Ray Absorption

Characterization of Polymers and Their Surfaces Using Ultra-Soft X-Ray Absorption Spectroscopy

1993 ◽  
Vol 304 ◽  
Author(s):  
Gary E. Mitchell ◽  
Benjamin M. Dekoven ◽  
David R. Speth ◽  
Mark E. Jones ◽  
James J. Curphy ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Film Thickness ◽  
Absorption Spectroscopy ◽  
Film Surface ◽  
Polymeric Materials ◽  
Fluorescence Yield ◽  
X Ray ◽  
Surface Sensitivity ◽  
X Ray Absorption

AbstractIn this paper we illustrate the use of Ultra Soft X-ray Absorption Spectroscopy (USXAS) for the characterization of polymeric materials by highlighting three novel applications of the technique. The surface sensitivity of electron yield (3 nm) and the bulk information available from fluorescence yield USXAS (200 nm) provide unique information on the chemistry of polymer surfaces and interfaces. USXAS is sensitive to both concentration and orientation of functional groups in polymers. The systems highlighted here include the characterization of flame treated model acrylic automotive coatings, ultra-low surface energy crosslinked fluorocarbon films, and spin cast polystyrene films. The chemical and surface sensitivity of the technique are emphasized by the ability of USXAS to detect an increase in the trigonally coordinated carbon at the surface after treatment with a reducing flame. The sensitivity to functional group orientation at the surface is demonstrated by the characterization of the crosslinked flurocarbon polymer films. The results show that the pendant fluoroalkyl moieties of these polymers are strongly oriented perpendicular to the film surface. Spin coated polystyrene films were characterized as a functionv of molecular weight, film thickness and casting solvent. The pendant phenyl groups were found to be preferentially oriented towards the normal to the surface plane, independent of casting solvent, molecular weight, and film thickness

Bayes-Turchin analysis of x-ray absorption data above the FeL2,3-edges

2006 ◽  
Vol 74 (13) ◽  
Author(s):  
H. H. Rossner ◽  
D. Schmitz ◽  
P. Imperia ◽  
H. J. Krappe ◽  
J. J. Rehr
Keyword(s):  
Absorption Data ◽  
X Ray ◽  
X Ray Absorption
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