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Extended X-ray absorption fine structure

About: Extended X-ray absorption fine structure is a research topic. Over the lifetime, 10452 publications have been published within this topic receiving 276744 citations.


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Journal ArticleDOI
TL;DR: In this paper, the influence of heat treatment in electrocatalytic activity for O 2 reduction for two cobalt catalysts was investigated. But the results obtained by XANES and EXAFS data clearly show that metallic cobalt aggregates with different size are synthetized in the range of increased activity.
Abstract: Electrochemical and X-ray absorption techniques have been used to determine the influence of heat treatment in electrocatalytic activity for O 2 reduction for two cobalt catalysts. The catalysts are cobalt phthalocyanine (catalyst 1) and polyacrylonitrile +cobalt acetate (catalyst 2) adsorbed on carbon black and heat treated at several temperatures. A maximum for the catalytic activity was obtained for PcCo at 850 o C and for the PAN+Co catalyst at 950 o C with subsequent decrease. The results obtained by XANES and EXAFS data clearly show that metallic cobalt aggregates with different size are synthetized in the range of increased activity

151 citations

Journal ArticleDOI
TL;DR: In this article, the authors used two-photon absorption, self-defocusing, and optically-induced melting in GaAs to limit 1 μm picosecond pulsed radiation.
Abstract: We have used two-photon absorption, self-defocusing, and optically-induced melting in GaAs to limit 1 μm picosecond pulsed radiation. The contribution to the limiting action from each of these mechanisms is discussed and demonstrated. Additionally, we measure a two-photon absorption coefficient of 26 cm/GW, which is in good agreement with the smallest values reported in the literature. A pulse-width study of the nonlinear absorption was conducted to isolate the effects of two-photon-generated free-carrier absorption. Results indicate that, even though the number of free-carriers is sufficient to severely defocus the incident beam, free-carrier absorption does not measurably contribute to the nonlinear absorption.

151 citations

Journal ArticleDOI
TL;DR: In this article, an extended x-ray absorption fine structure (EXAFS) measurements between 8 and 290 K at the Cd and Te K-edge were used to investigate the properties of thiolcapped CdTe nanocrystals.
Abstract: Thiolcapped CdTe nanocrystals (18 A diameter) are investigated by extended x-ray absorption fine structure (EXAFS) measurements between 8 and 290 K at the Cd and Te K-edge. The different coordination sites of Cd in the particle core and at the surface are identified and are consistent with a CdTe particle core which is covered by a Cd–SR surface layer (R=organic rest). We are able to study individually changes of the properties of the interior and the surface of the nanoparticle with respect to bulk material. Structure and dynamics of the CdTe nanocrystals are mainly altered by the requirement of heteroepitaxial growth at the interface between the CdTe core and the Cd–SR shell. As a consequence, bond lengths and Debye temperatures of particle core and surface show a tendency to accommodate in thiolcapped CdTe nanocrystals. The trends in bond lengths variation observed in the experiment can be reproduced by calculations of the strain distribution induced by the lattice mismatch in a simplified isotropic mo...

151 citations

Journal Article
TL;DR: In this article, the magnetic and structural properties of ultra-thin 3D transition metals films have been investigated, in particular Fe, Ni and Co films, by performing XMCD on Fe/Ag(100) and observing a spin reorientation from in-plane to out-ofplane as the Fe thickness is lowered.
Abstract: In this thesis the magnetic and structural properties of ultra-thin 3d transition metals films have been investigated, in particular Fe, Ni and Co films. X-ray Magnetic Circular Dichroism (XMCD) has provided element specific spin (ms ) and orbital (ml ) moments per atom by utilizing the magneto optic sum-rules. Element specific hysteresis curves have been measured by means of X-ray Resonant Magnetic Scattering (XRMS), and the local crystallographic structure has been investigated using Extended X-ray Absorption Fine Structure (EXAFS).By performing XMCD on Fe/Ag(100) we observe a spin reorientation from in-plane to out-of-plane as the Fe thickness is lowered. At temperatures below 300K it occurs around 5-7 mono layers (ML) of Fe. While reorienting the magnetization out-of-plane the orbital moment increases with 125% but only a minor increase (5%) of the spin moment is observed. Extended X-ray Absorption Fine Structure (EXAFS) measurements indicate that films 6 ML and thicker have a bulk-like bcc structure. For the thin out-of-plane films, the local crystallographic structure is more complicated.The spin reorientation of the Au/Co/Au tri-layer system has been studied as a function of temperature, Co layer and Au cap thickness. An unexpected behavior of the orbital moment upon spin reorientation is found in these systems. An ex-situ prepared sample shows a smooth spin reorientation from an in-plane to an out-of-plane easy magnetization direction as the temperature is lowered from 300K to 200K. In-situ prepared samples have also been investigated and a novel phase diagram has been identified. The Au/Co interface has been explored during the Au capping by means of photoemission measurements.In the bi- and tri-layer system of Fe and Ni we have been able to manipulate the spin reorientation by varying the Fe and Ni thickness. A novel non-collinear interlayer exchange interaction for 3d ferro magnets in direct contact has been discovered for a set of samples. This exchange interaction is found to be strongly dependant on the preparation conditions.

151 citations

Journal ArticleDOI
TL;DR: In this paper, a cobaltosic-oxide-nanosheets/reduced-graphene-oxide composite (CoNSs@RGO) was successfully prepared as a light-weight broadband electromagnetic wave absorber.
Abstract: A cobaltosic-oxide-nanosheets/reduced-graphene-oxide composite (CoNSs@RGO) was successfully prepared as a light-weight broadband electromagnetic wave absorber. The effects of the sample thickness and amount of composite added to paraffin samples on the absorption properties were thoroughly investigated. Due to the nanosheet-like structure of Co3O4, the surface-to-volume ratio of the wave absorption material was very high, resulting in a large enhancement in the absorption properties. The maximum refection loss of the CoNSs@RGO composite was–45.15 dB for a thickness of 3.6 mm, and the best absorption bandwidth with a reflection loss below–10 dB was 7.14 GHz with a thickness of 2.9 mm. In addition, the peaks of microwave absorption shifted towards the low frequency region with increasing thickness of the absorbing coatings. The mechanism of electromagnetic wave absorption was attributed to impedance matching of CoNSs@RGO as well as the dielectric relaxation and polarization of RGO. Compared to previously reported absorbing materials, CoNSs@RGO showed better performance as a lightweight and highly efficient absorbing material for application in the high frequency band.

151 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023110
2022264
2021156
2020164
2019164
2018151