X-ray absorption study at the Fe K-edge of garnets from the Ivrea-Verbano zone

1993 ◽  
Vol 57 (387) ◽  
pp. 249-255 ◽  
Author(s):  
Simona Quartieri ◽  
Gianni Antonioli ◽  
Pier Paolo Lottici ◽  
Gilberto Artioli
Keyword(s):  
Absorption Study ◽  
X Ray Diffraction ◽  
Neighbour Distance ◽  
X Ray ◽  
Coordination Numbers ◽  
Exafs Analysis ◽  
Diffraction Structure ◽  
Dodecahedral Site ◽  
X Ray Absorption ◽  
Xanes Analysis

AbstractK-edge X-ray absorption spectra of Fe in garnet samples from the Ivrea-Verbano zone were collected using synchrotron radiation. From XANES analysis, the prevalent oxidation state of Fe has been determined as 2+ in all studied samples. Coordination numbers and Fe-O bond lengths derived from the EXAFS analysis are compatible with a dodecahedral environment of Fe atoms and seem to be nearly independent of the variable Fe/Ca ratio of the cations sharing the dodecahedral site in these garnets. This suggests that, since at least up to 0.5 Ca atoms p.f.u, no sensible deformation of the dodecahedron geometry is sensed by the Fe cations, iron might strongly compete with Ca atoms in controlling the entry of rare earth elements in the dodecahedral site of garnets falling within this compositional range. Comparison of the EXAFS results with the data from single crystal X-ray diffraction structure refinements indicates a first shell neighbour distance accuracy of ±0.02 Å, using theoretical EXAFS phases and amplitudes. The Debye-Waller factors derived from the EXAFS analysis indicate a higher degree of disorder on the four longer Fe-O bond distances, in comparsion with the other four shorter distances of the height-coordinated cation; this could be related to the nonrigid polyhedral behaviour of the dodecahedral site.

Preparation of Iron Catalysts Generated from Fe-Coagulated Sludge Produced by Ferric Chloride Coagulation of Wastewater

2014 ◽  
Vol 1025-1026 ◽  
pp. 645-650
Author(s):  
Supranee Foowut ◽  
Tawanrat Palothaisit ◽  
Natthadabhorn Boonlor ◽  
Panida Prompinit ◽  
Pinsuda Viravathana
Keyword(s):  
Specific Surface ◽  
Pore Volume ◽  
Total Pore Volume ◽  
Iron Catalysts ◽  
Precipitation Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Co Precipitation ◽  
X Ray Absorption ◽  
Xanes Analysis

In this work, the FexOy catalysts were prepared by the co-precipitation method. The catalysts were characterized by X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), and Brunauer-Emmett-Teller (BET) surface analysis. From XRD results, the FexOy with the wastewater to coagulant ratio of 1:2 catalyst (FexOy-1:2) calcined at 600 °C for 6 h showed the presence of the wustite (FeO) form. XANES analysis showed the phase of FeO in FexOy-1:2 calcined at 600 °C for 6 h which corresponded to the result from XRD. The FexOy 1:1 catalyst had higher specific surface area and larger total pore volume compared to the FexOy 1:2 catalyst.

scholarly journals Состав, электронное и атомное строение наночастиц палладия при различных концентрациях металла в матрице полиэтилена

2020 ◽  
Vol 46 (7) ◽  
pp. 20
Author(s):  
С.С. Подсухина ◽  
А.В. Козинкин ◽  
В.Г. Власенко ◽  
Г.Ю. Юрков ◽  
О.В. Попков
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Palladium Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coordination Numbers ◽  
Transmission Electron ◽  
High Pressure Polyethylene ◽  
Average Size ◽  
X Ray Absorption

The composition, electronic and atomic structure of palladium nanoparticles stabilized in high pressure polyethylene (with palladium concentrations of 10 and 20 mass%) were studied by transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. It was found that nanoparticles consist of metal (Pd) and oxide (Pd2O3) components, and their average size and coordination numbers for first Pd coordination sphere decrease(from 7 to 6 nm and from 7 to 5.7, respectively) with a decrease in metal concentration.

scholarly journals Calcite Nanocrystals Investigated Using X-ray Absorption Spectroscopy

Crystals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 490
Author(s):  
Varsha Singh ◽  
Anil Kumar Paidi ◽  
Cheol-Hwee Shim ◽  
So Hee Kim ◽  
Sung Ok Won ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Shape Change ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Coordination Numbers ◽  
Transmission Electron ◽  
Local Electronic Structure ◽  
X Ray Absorption

For the present work, calcite nanocrystals were grown by annealing precursors at 500 °C. These precursors were obtained by three different thermal schemes. Among these schemes, two involve heating at 100 °C for 16 h and 16 + 24 h, respectively. In the third scheme, heating was performed at 100 °C for 16 h, followed by annealing at 300 °C for 24 h. X-ray diffraction studies, followed by Fourier transform infrared and Raman spectroscopic studies, exhibited the formation of calcite phase of calcium carbonate. Transmission electron microscopy showed that particle sizes of synthesized calcite nanocrystals were in the range of 25–40 nm. Onsets of shape change were also observed with different thermal schemes, using these measurements. X-ray absorption spectroscopy envisaged that the coordination numbers of Ca-O and Ca-Ca shell were not influenced by the thermal schemes; however, bond lengths of these shells were modified. This study in the near edge region evidenced the manifestation of a local electronic structure of calcite when kept in an open environment, depending upon different thermal schemes.

Synthesis and characterization of 1,2,3,4 tetrahydroquinoline intercalated into MoS2 in search of cleaner fuels

2007 ◽  
Vol 22 (10) ◽  
pp. 2747-2757 ◽  
Author(s):  
Karina Castillo ◽  
Felicia Manciu ◽  
J.G. Parsons ◽  
Russell R. Chianelli
Keyword(s):  
Fine Structure ◽  
Infrared Spectroscopy ◽  
Synthesis And Characterization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Coordination Numbers ◽  
Absorption Fine ◽  
Diffraction Patterns ◽  
X Ray Absorption

Two different morphologies of MoS2 (short and long sheets) were utilized to elucidate the intercalation mechanism of 1,2,3,4 tetrahydroquinoline (THQ). MoS2 (short sheets) and molybdenite (MB) (long sheets) were exfoliated and restacked in the presence of THQ. The x-ray diffraction patterns of both samples show a new reflection in the 001 plane, which implies a lowering of symmetry and corresponds to an expansion of the layers by approximately 12.3 Å. In the MoS2-THQ sample, 80% of the MoS2 was intercalated and 20% remained stacked. In the MB-THQ sample, 30% of MB was intercalated while 70% remained stacked. X-ray absorption structure (XAS) studies showed changes in atomic geometry and coordination. The x-ray absorption near-edge spectra showed shifts in the geometry of the intercalated MoS2 and MB sample compared to the unintercalated samples. Extended x-ray absorption fine structure studies showed lower coordination numbers compared to the untreated samples. Infrared spectroscopy characterization of these same samples suggests intercalation and partial dehydrogenation of the THQ.

Isomorphous replacement in electron diffraction of wet crystals of rat hemoglobin

1983 ◽  
Vol 41 ◽  
pp. 446-447
Author(s):  
William F. Tivol ◽  
Murray Vernon King ◽  
D. F. Parsons
Keyword(s):  
Electron Diffraction ◽  
Heavy Atom ◽  
Isomorphous Substitution ◽  
X Ray Diffraction ◽  
Salt Solutions ◽  
X Ray ◽  
Isomorphous Replacement ◽  
Structure Factors ◽  
Diffraction Structure ◽  
The Mean

Feasibility of isomorphous substitution in electron diffraction is supported by a calculation of the mean alteration of the electron-diffraction structure factors for hemoglobin crystals caused by substituting two mercury atoms per molecule, following Green, Ingram & Perutz, but with allowance for the proportionality of f to Z3/4 for electron diffraction. This yields a mean net change in F of 12.5%, as contrasted with 22.8% for x-ray diffraction.Use of the hydration chamber in electron diffraction opens prospects for examining many proteins that yield only very thin crystals not suitable for x-ray diffraction. Examination in the wet state avoids treatments that could cause translocation of the heavy-atom labels or distortion of the crystal. Combined with low-fluence techniques, it enables study of the protein in a state as close to native as possible.We have undertaken a study of crystals of rat hemoglobin by electron diffraction in the wet state. Rat hemoglobin offers a certain advantage for hydration-chamber work over other hemoglobins in that it can be crystallized from distilled water instead of salt solutions.

X-RAY ABSORPTION STUDY OF FREE AND BOUND SULPHUR IN MoS2+x(0 ≤ x ≤ 1)

1987 ◽  
Vol 48 (C9) ◽  
pp. C9-1049-C9-1052
Author(s):  
P. BELOUGNE ◽  
B. DEROIDE ◽  
J. M. ESTEVA ◽  
R. C. KARNATAK ◽  
J. V. ZANCHETTA
Keyword(s):  
Absorption Study ◽  
X Ray ◽  
X Ray Absorption

X-ray absorption study of Cu, Zn SOD under high pressure

2000 ◽  
Vol 19 (1-6) ◽  
pp. 277-283 ◽  
Author(s):  
Isabella Ascone ◽  
Andrea Cognigni ◽  
Yann Le Godec ◽  
Jean Paul Itié
Keyword(s):  
High Pressure ◽  
Absorption Study ◽  
X Ray ◽  
X Ray Absorption
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