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1,169 items found (0 items not approved), displaying 61 to 70.[First/Prev] 3, 4, 5, 6, 7, 8, 9, 10 [Next/Last]

Instruments / Technical Area	Publication Details	Published
B07-B-Versatile Soft X-ray beamline: High Throughput	Nanostructured silicon matrix for materials engineering Poting Liu , Alexander Schleusener , Gabriel Zieger , Arne Bochmann , Matthijs A. Van Spronsen , Vladimir Sivakov Small 4 DOI: 10.1002/smll.202206318 Diamond Proposal Number(s): [31119] Open Access Show Abstract ▼ Abstract: Tin-containing layers with different degrees of oxidation are uniformly distributed along the length of silicon nanowires formed by a top-down method by applying metalorganic chemical vapor deposition. The electronic and atomic structure of the obtained layers is investigated by applying nondestructive surface-sensitive X-ray absorption near edge spectroscopy using synchrotron radiation. The results demonstrated, for the first time, a distribution effect of the tin-containing phases in the nanostructured silicon matrix compared to the results obtained for planar structures at the same deposition temperatures. The amount and distribution of tin-containing phases can be effectively varied and controlled by adjusting the geometric parameters (pore diameter and length) of the initial matrix of nanostructured silicon. Due to the occurrence of intense interactions between precursor molecules and decomposition by-products in the nanocapillary, as a consequence of random thermal motion of molecules in the nanocapillary, which leads to additional kinetic energy and formation of reducing agents, resulting in effective reduction of tin-based compounds to a metallic tin state for molecules with the highest penetration depth in the nanostructured silicon matrix. This effect will enable clear control of the phase distributions of functional materials in 3D matrices for a wide range of applications.	Jan 2023
B18-Core EXAFS I20-Scanning-X-ray spectroscopy (XAS/XES)	Cr2+ solid solution in UO2 evidenced by advanced spectroscopy Hannah Smith , Luke T. Townsend , Ritesh Mohun , Théo Cordara , Martin C. Stennett , J. Frederick W. Mosselmans , Kristina Kvashnina , Claire L. Corkhill Communications Chemistry 5 DOI: 10.1038/s42004-022-00784-3 Diamond Proposal Number(s): [20872, 24074, 28515] Open Access Show Abstract ▼ Abstract: Advanced Cr-doped UO2 fuels are essential for driving safe and efficient generation of nuclear energy. Although widely deployed, little is known about their fundamental chemistry, which is a critical gap for development of new fuel materials and radioactive waste management strategies. Utilising an original approach, we directly evidence the chemistry of Cr(3+)2O3–doped U(4+)O2. Advanced high-flux, high-spectral purity X-ray absorption spectroscopy (XAS), corroborated by diffraction, Raman spectroscopy and high energy resolved fluorescence detection-XAS, is used to establish that Cr2+ directly substitutes for U4+, accompanied by U5+ and oxygen vacancy charge compensation. Extension of the analysis to heat-treated simulant nuclear fuel reveals a mixed Cr2+/3+ oxidation state, with Cr in more than one physical form, explaining the substantial discrepancies that exist in the literature. Successful demonstration of this analytical advance, and the scientific underpinning it provides, opens opportunities for an expansion in the range of dopants utilised in advanced UO2 fuels.	Dec 2022
B18-Core EXAFS I11-High Resolution Powder Diffraction	Suppression of Fe-cation migration by indium substitution in LiFe2–xInxSbO6 cathode materials Xabier Martinez De Irujo-Labalde , Heather Grievson , Josie-May Mortimer , Samuel G. Booth , Alex Scrimshire , Paul A. Bingham , Emmanuelle Suard , Serena A. Cussen , Michael A. Hayward Chemistry Of Materials DOI: 10.1021/acs.chemmater.2c03418 Diamond Proposal Number(s): [25166] Open Access Show Abstract ▼ Abstract: Cation migration on electrochemical cycling can significantly influence the performance of li-ion cathode materials. Phases of composition LiFe2–xInxSbO6 (0 < x <1) adopt crystal structures described in space group Pnnm, consisting of a hexagonally close-packed array of oxide ions, with Fe/In and Sb cations ordered on octahedral sites, and lithium cations located within partially occupied tetrahedral sites. NPD, SXRD, and 57Fe Mössbauer data indicate that on reductive lithium insertion (either chemically or electrochemically), LiFe2SbO6 is converted to Li2Fe2SbO6 accompanied by large-scale cation migration, to form a partially Fe/Li cation-ordered and Fe2+/Fe3+ charge-ordered phase from which lithium cations cannot be easily removed, either chemically or electrochemically. Partial substitution of Fe with In suppresses the degree of cation migration that occurs on lithium insertion such that no structural change is observed when LiFeInSbO6 is converted into Li1.5FeInSbO6, allowing the system to be repeatedly electrochemically cycled between these two compositions. Phases with intermediate levels of In substitution exhibit low levels of Fe migration on Li insertion and electrochemical capacities which evolve on cycling. The mechanism by which the In3+ cations suppress the migration of Fe cations is discussed along with the cycling behavior of the LiFe1.5In0.5SbO6–Li1.75Fe1.5In0.5SbO6.	Dec 2022
I10-Beamline for Advanced Dichroism	Polarization analysis by means of individual soft x-ray absorption spectra of rare earths Gerrit Van Der Laan , Thorsten Hesjedal , Peter Bencok Physical Review B 106 DOI: 10.1103/PhysRevB.106.214423 Diamond Proposal Number(s): [10207] Open Access Show Abstract ▼ Abstract: X-ray magnetic circular dichroism (XMCD), which by virtue of the sum rules provides element-specific spin and orbital moments, is obtained from the difference between two polarized spectra by reversing the direction of either the light helicity or the applied magnetic field. Usually, it is tacitly assumed that these two spectra are obtained using the same absolute degree of light and magnetic polarization. This is, however, not always possible and depends on circumstances that can be beyond control. First, we recapitulate the conventional XMCD sum rule method to obtain the values of the moments and emphasize some of the complications in the case of the rare-earth M 4 , 5 edges, such as the presence of strong core-hole j j overlap, linear dichroism, and magnetic dipole term ⟨ T z ⟩ . Instead, we propose an alternative method. Using the individual polarized x-ray absorption spectra obtained at the Ho and Dy M 5 edges, where each of the Δ J = − 1 , 0 , and + 1 transitions are separated by ∼ 2 eV in photon energy, we are able to determine independently the degree of circular dichroism in a single spectrum. Since light is a transverse wave, we need to include, apart from the circular dichroism, also a linear dichroism contribution in order to fit the circularly polarized spectra. In the measurements on paramagnetic rare-earth dopants it was found that reversing the field produces the same degree of circular dichroism, while reversing the helicity yields a ∼ 20% difference in the degree of circular dichroism.	Dec 2022
I10-Beamline for Advanced Dichroism	Magnetic correlations in the magnetic topological insulator (Cr,Sb)2Te3 N.-J. Steinke , S. L. Zhang , P. J. Baker , L. B. Duffy , F. Kronast , J. Krieger , Z. Salman , T. Prokscha , A. Suter , S. Langridge , Gerrit Van Der Laan , T. Hesjedal Physical Review B 106 DOI: 10.1103/PhysRevB.106.224425 Diamond Proposal Number(s): [11503] Show Abstract ▼ Abstract: Chromium-doped Sb 2 Te 3 is a magnetic topological insulator (MTI), which belongs to the ( Sb , Bi ) 2 ( Se , Te ) 3 family. When doped with the transition metals V, Cr, and Mn this family displays long-range ferromagnetic order above liquid nitrogen temperature and is currently intensely explored for quantum device applications. Despite the large magnetic ordering temperature, the experimental observation of dissipationless electrical transport channels, i.e., the quantum anomalous Hall effect, is limited in these materials to temperatures below ≈ 2 K. Inhomogeneities in the MTI have been identified as a major concern, affecting the coupling between the Dirac states and the magnetic dopants. Nevertheless, details on the local magnetic order in these materials are not well understood. Here, we report the study of the magnetic correlations in thin films using a combination of muon spin relaxation ( μ SR ) , and magnetic soft x-ray spectroscopy and imaging. μ SR provides two key quantities for understanding the microscopic magnetic behavior: The magnetic volume fraction, i.e., the percentage of the material that is ferromagnetically ordered, and the relaxation rate, which is sensitive to the magnetic static ( ≈ μ s ) and dynamic disorder. By choosing different implantation depths for the muons, one can further discriminate between near-surface and bulk properties. No evidence for a surface enhancement of the magnetic ordering is observed, but, instead, we find evidence of small magnetically ordered clusters in a paramagnetic background, which are coupled. The significant magnetic field shift that is present in all samples indicates a percolation transition that proceeds through the formation and growth of magnetically ordered spin clusters. We further find that fluctuations are present even at low temperatures, and that there appears to be a transition between superparamagnetism and superferromagnetism.	Dec 2022
B18-Core EXAFS	Transition-metal catalysts for methane dehydroaromatization (Mo, Re, Fe): activity, stability, active sites, and carbon deposits Yujie Liu , Marita Ćoza , Victor Drozhzhin , Yannis Van Den Bosch , Lingqian Meng , Rim Van De Poll , Emiel J. M. Hensen , Nikolay Kosinov Acs Catalysis DOI: 10.1021/acscatal.2c04962 Diamond Proposal Number(s): [22225] Open Access Show Abstract ▼ Abstract: The most studied catalysts for methane dehydroaromatization (MDA)─Mo/ZSM-5─are not commercialized yet due to the rapid deactivation and insufficient activity. Catalytic systems based on Fe and Re are potential alternatives to Mo-containing zeolites. Here, we compare the catalytic performance of these catalysts as a function of metal type and its loading in ZSM-5 zeolite. The results show that the catalytic activity decreases in the order of Re/ZSM-5 > Mo/ZSM-5 > Fe/ZSM-5, while the catalyst stability decreases in the opposite order: Fe/ZSM-5 > Mo/ZSM-5 > Re/ZSM-5. The active metal species in the working catalysts were determined by operando X-ray absorption near-edge structure spectroscopy combined with mass spectrometry. We found that Re0 and Fe2+ species are the most likely active species for the catalytic dehydroaromatization of CH4 to aromatics in respective catalysts. Combining the pulse reaction technique with operando thermogravimetry analysis–mass spectrometry experiments, we demonstrate that the length of the induction period strongly correlates to the activity of the catalyst. The longer induction period of the Fe/ZSM-5 catalyst indicates the slow growth of hydrocarbon pool intermediates inside the zeolite pores and thus explains its poor catalytic performance. Finally, both the formation of hydrocarbon pool species and the activity of Fe/ZSM-5 can be improved by increasing the Fe loading, reaction pressure, and space velocity.	Dec 2022
I14-Hard X-ray Nanoprobe	A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu Takaaki Noguchi , Toru Matsumoto , Akira Miyake , Yohei Igami , Mitsutaka Haruta , Hikaru Saito , Satoshi Hata , Yusuke Seto , Masaaki Miyahara , Naotaka Tomioka , Hope A. Ishii , John P. Bradley , Kenta K. Ohtaki , Elena Dobrică , Hugues Leroux , Corentin Le Guillou , Damien Jacob , Francisco De La Peña , Sylvain Laforet , Maya Marinova , Falko Langenhorst , Dennis Harries , Pierre Beck , Thi H. V. Phan , Rolando Rebois , Neyda M. Abreu , Jennifer Gray , Thomas Zega , Pierre-M. Zanetta , Michelle S. Thompson , Rhonda Stroud , Kate Burgess , Brittany A. Cymes , John C. Bridges , Leon Hicks , Martin R. Lee , Luke Daly , Phil A. Bland , Michael E. Zolensky , David R. Frank , James Martinez , Akira Tsuchiyama , Masahiro Yasutake , Junya Matsuno , Shota Okumura , Itaru Mitsukawa , Kentaro Uesugi , Masayuki Uesugi , Akihisa Takeuchi , Mingqi Sun , Satomi Enju , Aki Takigawa , Tatsuhiro Michikami , Tomoki Nakamura , Megumi Matsumoto , Yusuke Nakauchi , Masanao Abe , Masahiko Arakawa , Atsushi Fujii , Masahiko Hayakawa , Naru Hirata , Naoyuki Hirata , Rie Honda , Chikatoshi Honda , Satoshi Hosoda , Yu-Ichi Iijima , Hitoshi Ikeda , Masateru Ishiguro , Yoshiaki Ishihara , Takahiro Iwata , Kousuke Kawahara , Shota Kikuchi , Kohei Kitazato , Koji Matsumoto , Moe Matsuoka , Yuya Mimasu , Akira Miura , Tomokatsu Morota , Satoru Nakazawa , Noriyuki Namiki , Hirotomo Noda , Rina Noguchi , Naoko Ogawa , Kazunori Ogawa , Tatsuaki Okada , Chisato Okamoto , Go Ono , Masanobu Ozaki , Takanao Saiki , Naoya Sakatani , Hirotaka Sawada , Hiroki Senshu , Yuri Shimaki , Kei Shirai , Seiji Sugita , Yuto Takei , Hiroshi Takeuchi , Satoshi Tanaka , Eri Tatsumi , Fuyuto Terui , Ryudo Tsukizaki , Koji Wada , Manabu Yamada , Tetsuya Yamada , Yukio Yamamoto , Hajime Yano , Yasuhiro Yokota , Keisuke Yoshihara , Makoto Yoshikawa , Kent Yoshikawa , Ryohta Fukai , Shizuho Furuya , Kentaro Hatakeda , Tasuku Hayashi , Yuya Hitomi , Kazuya Kumagai , Akiko Miyazaki , Aiko Nakato , Masahiro Nishimura , Hiromichi Soejima , Ayako I. Suzuki , Tomohiro Usui , Toru Yada , Daiki Yamamoto , Kasumi Yogata , Miwa Yoshitake , Harold C. Connolly , Dante S. Lauretta , Hisayoshi Yurimoto , Kazuhide Nagashima , Noriyuki Kawasaki , Naoya Sakamoto , Ryuji Okazaki , Hikaru Yabuta , Hiroshi Naraoka , Kanako Sakamoto , Shogo Tachibana , Sei-Ichiro Watanabe , Yuichi Tsuda Nature Astronomy 121 DOI: 10.1038/s41550-022-01841-6 Open Access Show Abstract ▼ Abstract: Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study of space-weathering signatures on the most abundant type of inner solar system body: a C-type asteroid, composed of materials largely unchanged since the formation of the Solar System. Weathered Ryugu grains show areas of surface amorphization and partial melting of phyllosilicates, in which reduction from Fe3+ to Fe2+ and dehydration developed. Space weathering probably contributed to dehydration by dehydroxylation of Ryugu surface phyllosilicates that had already lost interlayer water molecules and to weakening of the 2.7 µm hydroxyl (–OH) band in reflectance spectra. For C-type asteroids in general, this indicates that a weak 2.7 µm band can signify space-weathering-induced surface dehydration, rather than bulk volatile loss.	Dec 2022
I18-Microfocus Spectroscopy	The bonding environment of chlorine in silicate melts Richard W. Thomas , Jon Wade , Bernard J. Wood Chemical Geology 25 DOI: 10.1016/j.chemgeo.2022.121269 Diamond Proposal Number(s): [28784] Open Access Show Abstract ▼ Abstract: The local bonding environment of chlorine in silicate melts has a profound influence over the thermodynamic properties and structure of a melt, affecting the viscosity, rheology, and volatile degassing potential. To constrain the bonding environment of Cl in natural silicate melts, we have determined Cl K-edge X-ray absorption fine structure (XAFS) spectra for 44 experimentally produced silicate glasses in both the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions. In the pre-edge region, the presence of a pre-edge peak indicates covalent bonding of chlorine with silicon. Addition of divalent cations suppresses this pre-edge feature, and its centroid shifts to higher energy, indicating a change to increasingly more ionic bonding. In the XANES region the main absorption edge energy, E0, and the energy of maximum intensity, EMax, are also compositionally dependent. SiO2- rich glasses have relatively low values of E0 and EMax while the addition of 2+ ions increases both to values close to those found in the end-member chlorides CaCl2, MgCl2, and FeCl2. In two Na-rich glasses, E0 and EMax are close to corresponding energies in NaCl. It appears, therefore that bonding in the glasses is closely related to that found in the simple chlorides. This may be due to clustering which generates Casingle bondCl, Mgsingle bondCl, Fesingle bondCl and Nasingle bondCl linkages either in the melts themselves or in the glasses due to rearrangements during quenching. The EXAFS parts of the glass spectra confirm the conclusions derived from the XANES region. These show that, as expected from the XANES region, addition of Ca and Fe2+ leads to R-space peaks which are closely related to those found in anhydrous CaCl2 and FeCl2 respectively. In order to determine if the spectra depend on pressure, temperature or chlorine fugacity of synthesis, 9 experiments were conducted using a single starting composition (Fe-free haplobasalt, An50Di28Fo22) across a range of temperatures (1300–1400 °C), pressures (5–20 kbar), chlorine fugacities (f(Cl2)) (1.38E−03 to 1.66E−06), and water contents (expected 0–8 wt% H2O). The results show that there is almost no change in the spectra across the XANES and EXAFS regions, indicating either that chlorine bonding is independent of the intensive parameters of the experiment or that all melts quench to glasses with the same local structure around the Cl atoms.	Dec 2022
I20-Scanning-X-ray spectroscopy (XAS/XES)	Use of copper carbonate as corrosion inhibitor for carbon steel in post combustion carbon capture Epameinondas Skountzos , Cameron A. Price , Mustafa M. Alsalem , Samuel G. Booth , Simone Polastri , Serena A. Cussen , Christopher Parlett , Kyra Sedransk Campbell Carbon Capture Science & Technology 31 DOI: 10.1016/j.ccst.2022.100095 Diamond Proposal Number(s): [25542] Open Access Show Abstract ▼ Abstract: The realisation of post-combustion CO2 capture (PCCC) at industrial scale remains limited; one challenge is the concerns around capital costs and another concern is corrosion of the system itself. Corrosion resistance and mitigation against the amine solvent monoethanolamine (MEA) was studied, using the inhibitor copper (II) carbonate basic (CC). Carbon steel (C1018) was tested in CO2 loaded, 5M aqueous MEA solution, alone and in the presence of CC, to assess the corrosivity of the solution. Immersion testing used mass loss, Fe and Cu ion concentration in solution via ICP-MS, imaging (SEM) and analytical techniques (XRD and EDX) to investigate the effect of corrosion. Generally, the use of CC improved C1018 corrosion resistance relative to C1018 alone. Even at low concentrations (0.9 mM), CC was effective in inhibiting corrosion against CO2 loaded MEA, as the observed corrosion rate was effectively zero and no dissolved Fe was detected in solution. There was no evidence of copper surface adsorption. To clarify the solution chemistry resulting in corrosion inhibition, the local chemical environment of Fe and Cu were probed by Cu and Fe K-edge X-ray Absorption Spectroscopy, respectively. The Cu K- edge HERFD-XANES spectra reveal that a Cu2+ amine complex forms, critical to understanding the structure which is promoting significant corrosion inhibition.	Dec 2022
B18-Core EXAFS	Highly active and stable OER electrocatalysts derived from Sr2MIrO6 for proton exchange membrane water electrolyzers Maria Retuerto , Laura Pascual , Jorge Torrero , Mohamed Abdel Salam , Alvaro Tolosana-Moranchel , Diego Gianolio , Pilar Ferrer , Paula Kayser , Vincent Wilke , Svenja Stiber , Veronica Celorrio , Mohamed Mokthar , Daniel García Sanchez , Aldo Saul Gago , Kaspar Andreas Friedrich , Miguel Antonio Peña , José Antonio Alonso , Sergio Rojas Nature Communications 13 DOI: 10.1038/s41467-022-35631-5 Diamond Proposal Number(s): [27733] Open Access Show Abstract ▼ Abstract: Proton exchange membrane water electrolysis is a promising technology to produce green hydrogen from renewables, as it can efficiently achieve high current densities. Lowering iridium amount in oxygen evolution reaction electrocatalysts is critical for achieving cost-effective production of green hydrogen. In this work, we develop catalysts from Ir double perovskites. Sr2CaIrO6 achieves 10 mA cm−2 at only 1.48 V. The surface of the perovskite reconstructs when immersed in an acidic electrolyte and during the first catalytic cycles, resulting in a stable surface conformed by short-range order edge-sharing IrO6 octahedra arranged in an open structure responsible for the high performance. A proton exchange membrane water electrolysis cell is developed with Sr2CaIrO6 as anode and low Ir loading (0.4 mgIr cm−2). The cell achieves 2.40 V at 6 A cm−2 (overload) and no loss in performance at a constant 2 A cm−2 (nominal load). Thus, reducing Ir use without compromising efficiency and lifetime.	Dec 2022

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