In Situ Study of the Bonding of Impurities in Metal-Impurity-Metal Laminate Composites

1988 ◽  
Vol 143 ◽  
Author(s):  
E. V. Barrera ◽  
S. M. Heald ◽  
H. L. Marcus
Keyword(s):  
Electron Beam Evaporation ◽  
Laminate Composites ◽  
Exafs Analysis ◽  
Molecular Beam Deposition ◽  
Oxide Phases ◽  
Interface Layers ◽  
Impurity Elements ◽  
X Ray Absorption ◽  
Reactive Ion Sputtering

The local structure of interface or near interface impurity elements has been observed by means of extended x-ray absorption fine structure spectroscopy (EXAFS). Multilayered samples were prepared using reactive ion sputtering, electron beam evaporation , and molecular beam deposition methods with vacuum conditions ranging from 10−5 to 10−9 Pa. The interface layers of titanium, gallium, and arsenic were deposited in partial to multiple atom layers alternating with 5 to 10 nm thick matrix layers of nickel, cobalt, or aluminum. Oxide phases, atoms in solution, and local ordering were identified. Ti oxides and silicon arsenide were used as standards for the EXAFS analysis. Auger electron spectroscopy complemented the EXAFS analysis.

Oxidation and phase identification in silver/iron-oxide nanocomposites

1995 ◽  
Vol 53 ◽  
pp. 200-201
Author(s):  
P. Bandaru ◽  
T. Yamamot ◽  
F. Cosandey
Keyword(s):  
Giant Magnetoresistance ◽  
Inert Atmosphere ◽  
Annealed Sample ◽  
Phase Identification ◽  
X Ray ◽  
Transmission Electron ◽  
Oxide Phases ◽  
Resolution Imaging ◽  
X Ray Absorption

In the last few years, there has been great interest in magnetic nanocomposite materials because of their unique properties such as giant magnetoresistance and enhanced magnetocaloric effects. We have recently synthesized bulk Ag/FeOx nanocomposites by inert gas phase condensation (GPC). In this process, Ag and Fe particles were first formed by co-evaporation followed by vapor phase condensation and collection on a LN2 cooled collector. The particles were then passivated in oxygen, collected and compacted in-situ. Selected samples were then annealed in an inert atmosphere of helium at 250°C for 1h or in an oxidizing atmosphere of 10%-O2/He at 230°C for 15h. These annealing treatments were found to modify the effective magnetic moment size and saturation value of magnetization. For the O annealed sample, a superparamagnetic nanocomposite has been obtained with a transition temperature Tc of 160 °K. In order to understand these magnetization changes, an effort has been made to characterize the microstructure and to identify the oxide phases by combined Mössbauer, X-ray absorption spectroscopy (XAS) and transmission electron microscopy (TEM). In this paper, phase identification by combined selected area diffraction and direct high resolution imaging are presented.

Hetero-Epitaxy of Group Va Metals on Sapphire

1972 ◽  
Vol 30 ◽  
pp. 492-493
Author(s):  
J. E. O'Neal ◽  
J. J. Bellina ◽  
B. B. Rath
Keyword(s):  
Thermal Contact ◽  
High Vacuum ◽  
Electron Beam Evaporation ◽  
Ultra High Vacuum ◽  
Backing Plate ◽  
Sapphire Substrates ◽  
Deposition Parameters ◽  
Polishing Damage ◽  
Reflection Electron Diffraction

Thin films of the bcc metals vanadium, niobium and tantalum were epitaxially grown on (0001) and sapphire substrates. Prior to deposition, the mechanical polishing damage on the substrates was removed by an in-situ etch. The metal films were deposited by electron-beam evaporation in ultra-high vacuum. The substrates were heated by thermal contact with an electron-bombarded backing plate. The deposition parameters are summarized in Table 1.The films were replicated and examined by electron microscopy and their crystallographic orientation and texture were determined by reflection electron diffraction. Verneuil-grown and Czochralskigrown sapphire substrates of both orientations were employed for each evaporation. The orientation of the metal deposit was not affected by either increasing the density of sub-grain boundaries by about a factor of ten or decreasing the deposition rate by a factor of two. The results on growth epitaxy are summarized in Tables 2 and 3.

In Situ X-Ray Absorption Studies of the Electrochemical Reduction of Hydroxocobalamin

1997 ◽  
Vol 7 (C2) ◽  
pp. C2-619-C2-620 ◽  
Author(s):  
M. Giorgett ◽  
I. Ascone ◽  
M. Berrettoni ◽  
S. Zamponi ◽  
R. Marassi
Keyword(s):  
Electrochemical Reduction ◽  
X Ray ◽  
Absorption Studies ◽  
X Ray Absorption

Application of In Situ X-ray Absorption Spectroscopy to Study Dilute Chromium Ions in a Molten Chloride Salt

2019 ◽  
Author(s):  
Jisue Moon ◽  
Carter Abney ◽  
Dmitriy Dolzhnikov ◽  
James M. Kurley ◽  
Kevin A. Beyer ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Structure ◽  
Chloride Salt ◽  
X Ray ◽  
Molten Chloride ◽  
Stable Species ◽  
Higher Temperature ◽  
Cr Concentration ◽  
X Ray Absorption

The local structure of dilute CrCl<sub>3</sub> in a molten MgCl<sub>2</sub>:KCl salt was investigated by <i>in situ</i> x-ray absorption spectroscopy (XAS) at temperatures from room temperature to 800<sup>o</sup>C. This constitutes the first experiment where dilute Cr speciation is explored in a molten chloride salt, ostensibly due to the compounding challenges arising from a low Cr concentration in a matrix of heavy absorbers at extreme temperatures. CrCl<sub>3</sub> was confirmed to be the stable species between 200 and 500<sup>o</sup>C, while mobility of metal ions at higher temperature (>700<sup>o</sup>C) prevented confirmation of the local structure.

Kinetic analysis of Ag particle redispersion into ZSM-5 in the presence of coke using in situ XAFS

2021 ◽  
Author(s):  
Kazumasa Murata ◽  
Junya Ohyama ◽  
Atsushi Satsuma
Keyword(s):  
Fine Structure ◽  
Kinetic Analysis ◽  
X Ray ◽  
Xafs Spectroscopy ◽  
Absorption Fine ◽  
Ag Particles ◽  
In Situ Xafs ◽  
Ag Particle ◽  
X Ray Absorption

In the present study, the redispersion behavior of Ag particles on ZSM-5 in the presence of coke was observed using in situ X-ray absorption fine structure (XAFS) spectroscopy.

scholarly journals Backbonding contributions to small molecule chemisorption in a metal–organic framework with open copper(i) centers

2021 ◽  
Author(s):  
Gregory M. Su ◽  
Han Wang ◽  
Brandon R. Barnett ◽  
Jeffrey R. Long ◽  
David Prendergast ◽  
...  
Keyword(s):  
Fine Structure ◽  
Small Molecule ◽  
Metal Organic Framework ◽  
X Ray ◽  
Metal Site ◽  
Absorption Fine ◽  
Metal Organic ◽  
X Ray Absorption ◽  
Organic Framework

In situ near edge X-ray absorption fine structure spectroscopy directly probes unoccupied states associated with backbonding interactions between the open metal site in a metal–organic framework and various small molecule guests.

Observing progressive damage in carbon fiber epoxy laminate composites via 3D in-situ X-ray tomography

2021 ◽  
pp. 107626
Author(s):  
Alejandra M. Ortiz-Morales ◽  
Imad Hanhan ◽  
Jose Javier Solano ◽  
Michael D. Sangid
Keyword(s):  
Carbon Fiber ◽  
Progressive Damage ◽  
Laminate Composites ◽  
X Ray ◽  
Carbon Fiber Epoxy

scholarly journals EXAFS Determination of Clay Minerals in Martian Meteorite Allan Hills 84001 and Its Implication for the Noachian Aqueous Environment

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 176
Author(s):  
Ryoichi Nakada ◽  
Gaku Tanabe ◽  
Iori Kajitani ◽  
Tomohiro Usui ◽  
Masashi Shidare ◽  
...  
Keyword(s):  
Silica Glass ◽  
Large Body ◽  
Aqueous Environment ◽  
Martian Surface ◽  
Exafs Analysis ◽  
Martian Meteorite ◽  
Fe Species ◽  
Allan Hills 84001 ◽  
X Ray Absorption

The aqueous environment of ancient Mars is of significant interest because of evidence suggesting the presence of a large body of liquid water on the surface at ~4 Ga, which differs significantly from the modern dry and oxic Martian environment. In this study, we examined the Fe-bearing minerals in the 4 Ga Martian meteorite, Alan Hills (ALH) 84001, to reveal the ancient aqueous environment present during the formation of this meteorite. Extended X-ray absorption fine structure (EXAFS) analysis was conducted to determine the Fe species in ALH carbonate and silica glass with a high spatial resolution (~1–2 μm). The μ-EXAFS analysis of ALH carbonate showed that the Fe species in the carbonate were dominated by a magnesite-siderite solid solution. Our analysis suggests the presence of smectite group clay in the carbonate, which is consistent with the results of previous thermochemical modeling. We also found serpentine in the silica glass, indicating the decrease of water after the formation of carbonate, at least locally. The possible allochthonous origin of the hematite in the carbonate suggests a patchy redox environment on the ancient Martian surface.

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