Structural changes in amorphous Co40Fe40B20 thin film interfaced with tungsten upon thermal annealing: A depth resolved XRD and XAS study
Mandeep SinghP. D. GuptaSanjay RaiSarathlal Koyiloth VayalilMukul GuptaIlaria CarlomagnoCarlo MeneghiniA. S. Gupta
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X-ray absorption spectroscopy
This report contains the feasibility and cost data for the production of tungsten-rhenium alloys from tungsten targets in the N-Reactor. The two types of target elements assumed were: (a) tungsten containing 90 a/o tungsten-186, 9 a/o tungsten-184 and 1 a/o tungsten-183 and 182, and (b) tungsten of natural isotopic composition.
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X-ray absorption spectroscopy
XANES
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TRACER
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고압 환경에서 규산염 용융체의 원자 구조에 대한 정보는 지구 내부 마그마의 열전도율이나 주변 암석과의 원소 분배계수와 같은 이동 물성을 이해하는 단서를 제공한다. 규소의 전자 구조는 규산염 다면체 주변의 산소 원자 분포와 연관성을 가질 것으로 예상되나, 이 사이의 상관관계가 명확하게 밝혀져 있지 않다. 본 연구는 SiO2의 고밀도화에 따른 규소의 전자 구조 변화의 미시적인 기원을 규명하기 위해 SiO2 동질이상의 규소 부분 상태 밀도와 L3-edge X-선 흡수분광분석(X-ray absorption spectroscopy; XAS) 스펙트럼을 계산하였다. 규소의 전도 띠 영역에서 전자 구조는 결정 구조에 따라서 변화하였다. 특히 d-오비탈은 108, 130 eV 영역에서 배위 환경에 따른 뚜렷한 차이를 보였다. 계산된 XAS 스펙트럼은 규소 전도 띠의 s,d-오비탈에서 기인하는 피크를 보였으며, 결정 구조에 따라 s,d-오비탈과 유사한 양상으로 변화했다. 계산된 석영의 XAS스펙트럼은 SiO2 유리의 X R S 실험 결과와 유사하였으며 규소 주변 원자 환경이 비슷하기 때문으로 생각된다. XAS 스펙트럼을 수치화한 무게 중심 값은 Si-O 결합 거리와 밀접한 상관관계를 가지며 이로 인하여 고밀도화 과정에서 체계적으로 변화한다. 본 연구의 결과는 Si-O 결합 거리에 민감한 규소 L2,3-edge XRS가 규산염 유리 및 용융체의 고밀도화 기작을 규명하는 과정에서 유용하게 적용될 수 있음을 지시한다.
X-ray absorption spectroscopy
K-edge
X-Ray Spectroscopy
Absorption edge
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Abstract
In this mini-review, we briefly discuss the physical origin of x-ray absorption spectroscopy (XAS) before illustrating its application using dinuclear metallohydrolases as exemplary systems. The systems we have selected for illustrative purposes present a challenging problem for XAS, one that is ideal to demonstrate the potential of this methodology for structure/function studies of metalloenzymes in general. When the metal ion is redox active, XAS provides a sensitive measure of oxidation-state-dependent differences. When the metal ion is zinc, XAS is the only spectroscopic method that will provide easily accessible structural information in solution. In the case of heterodimetallic sites, XAS has the unique ability to interrogate each metal site independently in the same sample. One of the strongest advantages of XAS is its ability to examine metal ion site structures with crystallographic precision, without the need for a crystal. This is key for studying flexible metal ion sites, such as those described in the selected examples, because it allows one to monitor structural changes that occur during substrate turnover.X-ray absorption spectroscopy
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電気化学反応を理解する上で，電極固液界面を含む電解質溶液の局所構造変化を調べることが重要である．X線吸収分光法（XAS）は液体の局所構造を元素選択的に観測できる有用な手法であり，著者らが開発した透過赤外分光にもそのまま対応できる液体セルにより，C－K，N－K，O－Kなどの化学的に重要な吸収端が存在する1 keV以下の軟X線領域において，透過法XAS測定が可能になった．この液体セルに電極を備えることにより，電気化学反応中の電解質溶液のXASによるその場観測を可能にして，硫酸鉄水溶液の電位変化による鉄イオンの価数変動をFe－L吸収端XAS測定から明らかにした．更に電位変調XAS法を開発することで，サイクリックボルタンメトリーと同じ電位掃引速度（100 mV s－1）で，硫酸鉄水溶液の電気化学反応をXASでオペランド（実動作下）観測した．また液体セルを走査型透過軟X線顕微鏡（STXM）に組み込むことで，30 nmの空間分解能で電気化学反応中の電解質溶液をXASで顕微観測する試みについても報告する．
X-ray absorption spectroscopy
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A micro-structuring of the tungsten plasma-facing surface can strongly reduce near surface thermal stresses induced by ELM heat fluxes. This approach has been confirmed by numerical simulations with the help of ANSYS software. For experimental tests, two 10 × 10 mm2 samples of micro-structured tungsten were manufactured. These consisted of 2000 and 5000 vertically packed tungsten fibres with dimensions of Ø240 µm × 2.4 mm and Ø150 µm × 2.4 mm, respectively. The 1.2 mm bottom parts of the fibres are embedded in a copper matrix. The top parts of the fibres have gaps about of 10 µm so they are not touching each others. The top of all tungsten fibres was electro-polished. A Nd:YAG laser with a pulse duration 1 ms and a pulse repetition frequency of 25 Hz was used to simulate up to 105 ELM-like heat pulses. No damage on either of the micro-structured tungsten samples were observed. Neon plasma erosion rate and fuel retention of the micro-structured tungsten samples were almost identical to bulk tungsten samples.
Pulse duration
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Application of X-ray Absorption Spectroscopy (XAS) to observation of various reactions is reviewed. XAS is a unique tool for studying the local structure around a selected element at atomic scale. XAS can be applied to materials such as crystals, amorphous systems, and liquids, which are situated in various conditions (in gas, at high temperature, with an applied stress,…). Thus XAS is one of the most powerful techniques to investigate the structure change of materials during reactions and understand the mechanism. In this paper, some of typical examples-redox of catalyst, corrosion of steel, heterogeneous reduction of oxides-are shown and their key points are discussed.
X-ray absorption spectroscopy
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X-ray absorption spectroscopy
XANES
Coordination complex
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Feasibility and cost data are supplied for the production of tungsten-rhenium alloys from tungsten targets in the N-Reactor. The two types of target elements assumed were: (a) tungsten containing 90 a/o tungsten-186, 9 a/o tungsten-184 and 1 a/o tungsten-183 and 182, and (b) tungsten of natural isotopic composition (28.4 a/o tungsten-186, 30.6 a/o tungsten-184, 14.4 a/o tungsten 183, and 26.4 tungsten-182). It is assumed that the average thermal neutron capture cross section for the tungsten-186 is 32 barns.
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