Characterization of Carbon-Encapsulated Nickel and Iron Nanoparticles by Means of X-ray Absorption and Photoelectron Spectroscopy

2010 ◽  
Vol 114 (51) ◽  
pp. 22413-22416 ◽  
Author(s):  
V. R. Galakhov ◽  
A. S. Shkvarin ◽  
A. S. Semenova ◽  
M. A. Uimin ◽  
A. A. Mysik ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Iron Nanoparticles ◽  
X Ray ◽  
X Ray Absorption

scholarly journals A multi-method characterization of natural terrestrial birnessites

2020 ◽  
Vol 105 (6) ◽  
pp. 833-847
Author(s):  
Florence T. Ling ◽  
Jeffrey E. Post ◽  
Peter J. Heaney ◽  
Cara M. Santelli ◽  
Eugene S. Ilton ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Large Set ◽  
X Ray Diffraction ◽  
Full Spectrum ◽  
X Ray ◽  
High Concentrations ◽  
Diffraction Patterns ◽  
X Ray Absorption ◽  
Crystal Structure And Chemistry

Abstract With a focus on a large set of natural birnessites collected from terrestrial, freshwater systems, we applied and compared the capabilities of X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) to characterize crystal structure and chemistry. Using XRD, we successfully identified 3 of the 11 natural birnessite samples as hexagonal ranciéite-like phases, but the remaining samples yielded less interpretable “3-line” diffraction patterns with broad, asymmetrical peaks at d-spacings of ~7.2, ~2.4, and ~1.4 Å. EXAFS analysis suggested that many of these samples had characteristics of both triclinic and hexagonal birnessite. However, application of EXAFS to the ranciéite-like phases yielded unreasonably high concentrations of triclinic birnessite as an intergrowth, calling into question the use of synthetic hexagonal H-birnessite as an appropriate standard in the linear combination fitting of EXAFS data for natural birnessites. FTIR spectroscopy of the “3-line” birnessite samples successfully distinguished triclinic and hexagonal constituents, and analyses of peak positions suggested that natural birnessites occur as a full spectrum of triclinic and hexagonal intergrowths. XPS analysis of these samples revealed that higher Mn3+ concentrations relative to Mn2+ and Mn4+ are correlated to increased proportions of triclinic birnessite.

Low-temperature preparation and structural characterization of Pr-doped ceria solid solutions

2002 ◽  
Vol 17 (4) ◽  
pp. 797-804 ◽  
Author(s):  
E. López-Navarrete ◽  
A. Caballero ◽  
A. R. González-Elipe ◽  
M. Ocaña
Keyword(s):  
Solid Solutions ◽  
Photoelectron Spectroscopy ◽  
Heating Temperature ◽  
Doped Ceria ◽  
X Ray ◽  
Ceria Solid Solutions ◽  
Low Temperature Preparation ◽  
Distribution Composition ◽  
X Ray Absorption

We report a method for preparing Pr-doped ceria by pyrolysis at 600 °C of aerosols consisting of aqueous solutions of Ce(III) nitrate and Pr(III) chloride. This procedure involves an important decrease of the temperature of solid solution formation (several hundred degrees) when compared with the ceramic and other previously reported methods, and does not require the addition of fluxes. The prepared samples and their products after thermal treatment were characterized in terms of particle shape and size distribution, composition, and crystalline structure. The color properties of these solid solutions were also evaluated as a function of the heating temperature and composition; the optimum red pigment was obtained for samples with a Pr/Ce mole ratio = 0.063 heated for 3 h at 600 °C. The oxidation state of the Pr cations and their distribution in the CeO2 matrix were investigated by x-ray absorption near-edge spectroscopy and x-ray photoelectron spectroscopy. A mixture of trivalent and tetravalent Pr was detected in all studies samples. The Pr(IV)/Pr(III) ratio increased as the Pr content or the heating temperature increased. These Pr(III) cations were found to be mainly located in the particles' outer layers, in which an enrichment of Pr was detected for all samples heated at 600 °C. The further calcination of the pigments at 1200 °C gave rise to a certain diffusion of the Pr cations toward the particle core, which was more significant for the sample with the highest Pr content (Pr/Ce mole ratio 4 0.091).

scholarly journals High mobility transparent and conducting oxide films of La-doped SrSnO3

2021 ◽  
Author(s):  
Yogesh Kumar ◽  
Ravi Kumar ◽  
K Asokan ◽  
R J Choudhary ◽  
D M Phase ◽  
...  
Keyword(s):  
Thin Films ◽  
Photoelectron Spectroscopy ◽  
Visible Region ◽  
High Mobility ◽  
X Ray ◽  
Carrier Effective Mass ◽  
Heterostructure Devices ◽  
X Ray Absorption ◽  
La Doped

Abstract The synthesis and characterization of high mobility thin films of La-doped SrSnO 3 are reported. The mobility for the 7% La-doped sample is found to be 228 cm 2 V -1 s -1 . The observed high mobility is associated with the reduced carrier effective mass and scattering centers of various scattering mechanisms. The enhancement in mobility and the increase in carrier concentration after doping reduced the resistivities of the thin films by 5 orders of magnitude. X-ray absorption spectroscopy and X-ray photoelectron spectroscopy revealed that La-dopant and oxygen vacancies donate the electrons in the films. Films were highly transparent (> 90%) in the visible region. These materials have great potential to be used in the optoelectronic and heterostructure devices.

Characterization of Antimony-Doped TIN Oxide Catalysts

2001 ◽  
Vol 7 (S2) ◽  
pp. 1094-1095
Author(s):  
K. Sun ◽  
J. Liu ◽  
N.D. Browning
Keyword(s):  
Tin Oxide ◽  
Photoelectron Spectroscopy ◽  
Contrast Imaging ◽  
X Ray ◽  
Catalytic Activities ◽  
Valence States ◽  
Z Contrast ◽  
Electron Energy Loss ◽  
X Ray Absorption

Antimony-doped tin oxide (ATO) catalysts are used for the oxidation of propylene to acrolein, the ammoxidation of propylene to acrylonitrile and the oxidative dehydrogenation of butanes to 1,3- butadiene. The distribution and valence states of Sb in ATOs are key in determining their catalytic activities. While these materials have been subjects of intensive studies for more than 20 years, X-ray photoelectron spectroscopy, Mössbauer spectrometry, and X-ray absorption spectroscopy4 have so far provided only indirect data for the distribution of Sb and its valence states. in particular, while has been hypothesized that the tin (IV) oxide contains Sb (V) within the bulk lattice and Sb (III) located at surface sites, no direct experimental evidence for this has been provided.Here we use electron energy loss spectroscopy (EELS) combined with Z-contrast imaging in a JEOL 2010F field emission STEM/TEM operating at 200 KV to analyze ATO catalysts.

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