EXELFS Studies of Carbon Fibers

The present developments of electron energy analysis in the microscopes by E.E.L.S. allow an accurate recording of the spectra and of their different complex structures associated with the inner shell electron excitation by the incident electrons (1). Among these structures, the Extended Energy Loss Fine Structures (EXELFS) are of particular interest. They are equivalent to the well known EXAFS oscillations in X-ray absorption spectroscopy. Due to the EELS characteristic, the Fourier analysis of EXELFS oscillations appears as a promising technique for the characterization of composite materials, the major constituents of which are low Z elements. Using EXELFS, we have developed a microstructural study of carbon fibers. This analysis concerns the carbon K edge, which appears in the spectra at 285 eV. The purpose of the paper is to compare the local short range order, determined by this way in the case of Courtauld HTS and P100 ex-polyacrylonitrile carbon fibers, which are high tensile strength (HTS) and high modulus (HM) fibers respectively.

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Characterization of the Local Titanium Environment in Doped Sodium Aluminum Hydride using X-ray Absorption Spectroscopy

MRS Proceedings ◽

10.1557/proc-837-n2.4 ◽

2004 ◽

Vol 837 ◽

Cited By ~ 1

Author(s):

J. Graetz ◽

A.Yu. Ignatov ◽

T.A. Tyson ◽

J.J. Reilly ◽

J. Johnson

Keyword(s):

Absorption Spectroscopy ◽

Interatomic Distance ◽

Aluminum Hydride ◽

Titanium Atom ◽

Long Range Order ◽

X Ray ◽

Fine Structures ◽

X Ray Absorption ◽

Exafs Spectra

ABSTRACTTi K -edge x-ray absorption spectroscopy was used to explore the local titanium environment and valence in 2–4 mol% Ti-doped sodium alanate. An estimate of the oxidation state of the dopant, based upon known standards, revealed a zero-valent titanium atom. An analysis of the near-edge and extended fine structures indicates that the Ti does not enter substitutional or interstitial sites in the NaAlH4 lattice. Rather, the Ti is located on/near the surface and is coordinated by 10.2±1 aluminum atoms with an interatomic distance of 2.82±0.01 Å, similar to that of TiAl3. The Fourier transformed EXAFS spectra reveal a lack of long-range order around the Ti dopant indicating that the Ti forms nano-clusters of TiAl3. The similarity of the spectra in the hydrided and dehydrided samples suggests that the local Ti environment is nearly invariant during hydrogen cycling.

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Database of ab initio L-edge X-ray absorption near edge structure

Scientific Data ◽

10.1038/s41597-021-00936-5 ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Yiming Chen ◽

Chi Chen ◽

Chen Zheng ◽

Shyam Dwaraknath ◽

Matthew K. Horton ◽

...

Keyword(s):

High Throughput ◽

Scattering Theory ◽

Research Community ◽

Metal Compounds ◽

Edge Structure ◽

X Ray ◽

Initial Release ◽

Computational Workflow ◽

X Ray Absorption

AbstractThe L-edge X-ray Absorption Near Edge Structure (XANES) is widely used in the characterization of transition metal compounds. Here, we report the development of a database of computed L-edge XANES using the multiple scattering theory-based FEFF9 code. The initial release of the database contains more than 140,000 L-edge spectra for more than 22,000 structures generated using a high-throughput computational workflow. The data is disseminated through the Materials Project and addresses a critical need for L-edge XANES spectra among the research community.

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Characterization of Silver Binding in Cryptomelane by X-ray Absorption Spectroscopy

MRS Proceedings ◽

10.1557/proc-524-353 ◽

1998 ◽

Vol 524 ◽

Cited By ~ 4

Author(s):

R. Ravikumar ◽

D. W. Fuerstenau ◽

G. A. Waychunas

Keyword(s):

Manganese Oxide ◽

Silver Ions ◽

Oxide Phase ◽

Synthetic Sample ◽

Temperature Spectrum ◽

X Ray ◽

Room Temperature Sample ◽

X Ray Absorption ◽

Temperature Sample

ABSTRACTUsing silver K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy, two different samples of silver-containing manganese oxide were analyzed in the fluorescence mode. For the first sample, silver ions from solution were sorbed onto one synthetic manganese oxide phase, namely cryptomelane (KxMn8O16, where l<x<2). The second sample was a silvermanganese oxide from Colorado. From the EXAFS analysis, silver was found to occupy two different sites in the synthetic sample. The natural samples from Colorado also exhibited a very similar coordination distances as the synthetic samples. In the low temperature spectrum of the synthetic sample at 10 K, the Ag-O peak was found to be missing and the amplitude of the Ag- Ag peak was approximately three times larger than the corresponding room temperature sample.

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