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| 2. |
- Manzoni, A. M., et al.
(författare)
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Evolution of γ/γ' phases, their misfit and volume fractions in Al 10 Co 25 Cr 8 Fe 15 Ni 36 Ti 6 compositionally complex alloy
- 2019
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Ingår i: Materials Characterization. - : Elsevier BV. - 1044-5803. ; 154, s. 363-376
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Tidskriftsartikel (refereegranskat)abstract
- Recently introduced Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy has been investigated in the as-cast state and after heat treatment in a thorough characterization. The combination of optical, scanning and transmission electron microscopy, three dimensional atom probe and x-ray diffraction, both at lab and synchrotron level provides precise information of the microstructural evolution. After the typical dendritic solidification the alloy reveals dendritic cores consisting of γ and γ' phases and interdendritic regions consisting of η and Heusler type phases. Homogenization removes the interdendritic regions and their phases and subsequent annealing produces a microstructure similar to Ni based superalloys consisting of γ/γ' phases. In addition, about 50 μm sized Al-Ni rich needle-shaped precipitates of Heusler type structure can be observed. The four phases and their evolution with heat treatment are investigated in detail. Special focus lies on the γ/γ' misfit determination and the determination of volume fractions by different methods.
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| 3. |
- Mori, R. Alonso, et al.
(författare)
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Sulfur-Metal Orbital Hybridization in Sulfur-Bearing Compounds Studied by X-ray Emission Spectroscopy
- 2010
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 49:14, s. 6468-6473
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure and ligand environment of sulfur was investigated in various sulfur-containing compounds with different structures and chemical states by using X-ray emission spectroscopy (XES). Calculations were performed using density functional theory (DFT) as implemented in the StoBe code. The sulfur chemical state and atomic environment is discussed in terms of the molecular orbitals and partial charges that are obtained from the calculations. The main spectral features can be modeled using our calculational approach. The sensitivity of the K beta emission to the cation and the local symmetry is discussed.
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| 8. |
- Wernet, Ph., et al.
(författare)
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The Structure of the First Coordination Shell in Liquid Water
- 2004
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 304:5673, s. 995-999
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy and x-ray Raman scattering were used to probe the molecular arrangement in the first coordination shell of liquid water. The local structure is characterized by comparison with bulk and surface of ordinary hexagonal ice Ih and with calculated spectra. Most molecules in liquid water are in two hydrogen-bonded configurations with one strong donor and one strong acceptor hydrogen bond in contrast to the four hydrogen-bonded tetrahedral structure in ice. Upon heating from 25°C to 90°C, 5 to 10% of the molecules change from tetrahedral environments to two hydrogen-bonded configurations. Our findings are consistent with neutron and x-ray diffraction data, and combining the results sets a strong limit for possible local structure distributions in liquid water. Serious discrepancies with structures based on current molecular dynamics simulations are observed.
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| 9. |
- Alonso-Mori, Roberto, et al.
(författare)
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Energy-dispersive X-ray emission spectroscopy using an X-ray free-electron laser in a shot-by-shot mode
- 2012
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:47, s. 19103-19107
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Tidskriftsartikel (refereegranskat)abstract
- The ultrabright femtosecond X-ray pulses provided by X-ray free-electron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this probe-before-destroy approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. K beta(1,3) XES spectra of Mn-II and Mn-2(III,IV) complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to > 100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shot-by-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II.
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