Articles de revues : « Angle Resolved - XRF »

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Szwedowski-Rammert, Veronika, Jonas Baumann, Christopher Schlesiger, Ulrich Waldschläger, Armin Gross, Birgit Kanngießer et Ioanna Mantouvalou. « Laboratory based GIXRF and GEXRF spectrometers for multilayer structure investigations ». Journal of Analytical Atomic Spectrometry 34, n^o 5 (2019) : 922–29. http://dx.doi.org/10.1039/c8ja00427g.

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Ebel, Horst, Maria F. Ebel, Robert Svagera, Norbert Wirth, Roland Kaitna et Hartinut Schandl. « Xrf With Tunable Monochromatic Excitation and Variation of the Incidence Angle ». Advances in X-ray Analysis 37 (1993) : 619–27. http://dx.doi.org/10.1154/s0376030800016177.

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The x-ray source of our instrument is a rotating anode system with a silver target. It is flanged to a He-filled monochromator chamber. The photon energy of the x-rays for the excitation of characteristic specimen radiation can be tuned continuously from IkeV to 30 keV. The cross-section of the beam - monochromatic or polychromatic tube radiation - leaving the monochromator chamber is variable within 0.1 and 100mm2. A Be-window separates the evacuable specimen chamber from the monochromator chamber. The specimen holder allows for a linear movement of the specimen in x- and y-direction normal to the beam of incident x-radiation and allows a laterally resolved analysis. A rotation around an axis normal to the incident x-ray beam enables investigations under variable incidence- and take-off angles. X-ray detection is performed by an energy dispersive system.

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Carpenter, D. A., et M. A. Taylor. « Fast, High-Resolution X-ray Microfluorescence Imaging ». Advances in X-ray Analysis 34 (1990) : 217–21. http://dx.doi.org/10.1154/s0376030800014506.

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X-ray micro fluorescence imaging refers to the use of an x-ray beam as a probe to excite XRF in a specimen and produce a spatially resolved image of the element distribution. The advantages of high sensitivity and low background, together with the nondestructive nature of the measurement, have lead to applications of x-ray microfluorescence analysis in biology, geology, materials science, as well as in the area of nondestructive evaluation. Previous reports have described the development of an x-ray microprobe which uses a conventional source of x-rays to produce a 10-μm beam. This paper describes improvements to the microprobe which have increased the beam power and the solid angle of detection. The data collection and display software have also been enhanced.

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Reis, M. A., P. C. Chaves, V. Corregidor, N. P. Barradas, E. Alves, F. Dimroth et A. W. Bett. « Detection angle resolved PIXE and the equivalent depth concept for thin film characterization ». X-Ray Spectrometry 34, n^o 4 (2005) : 372–75. http://dx.doi.org/10.1002/xrs.841.

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LIU, SHUANG, CHARLES M. FALCO et ZHIYONG ZHONG. « STUDY OF THE MICRO-STRUCTURE OF PtxSi ULTRA-THIN FILM ». International Journal of Modern Physics B 25, n^o 21 (20 août 2011) : 2925–29. http://dx.doi.org/10.1142/s0217979211100497.

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Ultra-thin platinum (Pt) films were deposited on Si (100) substrates at 160°C by magnetron sputtering and subsequently annealed to form silicides. The thickness of the Pt x Si films was found to be approximately 4 nm as determined by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) analysis shows that these films consist of PtSi and Pt 2 Si phases, and a multi-layer configuration of SiO x/ PtSi/Pt 2 Si/Si was detected by angle-resolved XPS. However, the Pt 3 Si phase was not detected by X-ray diffraction (XRD).

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Perrillat, J. P. « Kinetics of high-pressure mineral phase transformations using in situ time-resolved X-ray diffraction in the Paris-Edinburgh cell : a practical guide for data acquisition and treatment ». Mineralogical Magazine 72, n^o 2 (avril 2008) : 683–95. http://dx.doi.org/10.1180/minmag.2008.072.2.683.

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AbstractSynchrotron X-ray diffraction (XRD) is a powerful technique to study in situ and in real-time the structural and kinetic processes of pressure-induced phase transformations. This paper presents the experimental set-up developed at beamline ID27 of the ESRF to perform time-resolved angle dispersive XRD in the Paris-Edinburgh cell. It provides a practical guide for the acquisition of isobaric-isothermal kinetic data and the construction of transformation-time plots. The interpretation of experimental data in terms of reaction mechanisms and transformation rates is supported by an overview of the kinetic theory of solid-solid transformations, with each step of data processing illustrated by experimental results of relevance to the geosciences. Reaction kinetics may be affected by several factors such as the sample microstructure, impurities or differential stress. Further high-pressure kinetic studies should investigate the influence of such processes, in order to acquire kinetic information more akin to natural or technological processes.

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Balashova, Elena, Andrey Zolotarev, Aleksandr A. Levin, Valery Davydov, Sergey Pavlov, Alexander Smirnov, Anatoly Starukhin et al. « Crystal Structure, Raman, FTIR, UV-Vis Absorption, Photoluminescence Spectroscopy, TG–DSC and Dielectric Properties of New Semiorganic Crystals of 2-Methylbenzimidazolium Perchlorate ». Materials 16, n^o 5 (28 février 2023) : 1994. http://dx.doi.org/10.3390/ma16051994.

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Single crystals of 2-methylbenzimidazolium perchlorate were prepared for the first time with a slow evaporation method from an aqueous solution of a mixture of 2-methylbenzimidazole (MBI) crystals and perchloric acid HClO4. The crystal structure was determined by single crystal X-ray diffraction (XRD) and confirmed by XRD of powder. Angle-resolved polarized Raman and Fourier-transform infrared (FTIR) absorption spectra of crystals consist of lines caused by molecular vibrations in MBI molecule and ClO4− tetrahedron in the region ν = 200–3500 cm−1 and lattice vibrations in the region of 0–200 cm−1. Both XRD and Raman spectroscopy show a protonation of MBI molecule in the crystal. An analysis of ultraviolet-visible (UV-Vis) absorption spectra gives an estimation of an optical gap Eg~3.9 eV in the crystals studied. Photoluminescence spectra of MBI-perchlorate crystals consist of a number of overlapping bands with the main maximum at Ephoton ≅ 2.0 eV. Thermogravimetry-differential scanning calorimetry (TG-DSC) revealed the presence of two first-order phase transitions with different temperature hysteresis at temperatures above room temperature. The higher temperature transition corresponds to the melting temperature. Both phase transitions are accompanied by a strong increase in the permittivity and conductivity, especially during melting, which is similar to the effect of an ionic liquid.

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Kumar, Arun, Seyed Ariana Mirshokraee, Alessio Lamperti, Matteo Cantoni, Massimo Longo et Claudia Wiemer. « Interface Analysis of MOCVD Grown GeTe/Sb2Te3 and Ge-Rich Ge-Sb-Te/Sb2Te3 Core-Shell Nanowires ». Nanomaterials 12, n^o 10 (10 mai 2022) : 1623. http://dx.doi.org/10.3390/nano12101623.

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Controlling material thickness and element interdiffusion at the interface is crucial for many applications of core-shell nanowires. Herein, we report the thickness-controlled and conformal growth of a Sb2Te3 shell over GeTe and Ge-rich Ge-Sb-Te core nanowires synthesized via metal-organic chemical vapor deposition (MOCVD), catalyzed by the Vapor–Liquid–Solid (VLS) mechanism. The thickness of the Sb2Te3 shell could be adjusted by controlling the growth time without altering the nanowire morphology. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to examine the surface morphology and the structure of the nanowires. The study aims to investigate the interdiffusion, intactness, as well as the oxidation state of the core-shell nanowires. Angle-resolved X-ray photoelectron spectroscopy (XPS) was applied to investigate the surface chemistry of the nanowires. No elemental interdiffusion between the GeTe, Ge-rich Ge-Sb-Te cores, and Sb2Te3 shell of the nanowires was revealed. Chemical bonding between the core and the shell was observed.

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Zhu, Rong, Yan Jun Wu, Jing Tao Wang et Ke Cheng Lu. « Mechanical Anisotropy of Extruded Mg-10Gd-2Y-0.5Zr Alloy ». Advanced Materials Research 320 (août 2011) : 222–27. http://dx.doi.org/10.4028/www.scientific.net/amr.320.222.

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Tensile and compressive tests were performed on extruded Mg-10Gd-2Y-0.5Zr (mass fraction, %) alloy specimens with different tilt angles relative to extrusion direction. The microstructures were examined by X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM). Calculations of the orientation factors for basal slip were done for that existed texture. The results show that the alloy doesn’t show tensile-compressive yield strength asymmetry, and the highest flow stress is appeared along the extrusion direction. Meanwhile the extruded textures are much more randomized. The reason may be that the addition of rare-earth is benefit to activate the non-basal slips, especially pyramidal <c+a>slip. The reduction of c/a ratio is helpful to enhance the symmetry of the Mg crystal, which decreases the critical resolved shear stress of <c+a> slip.

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Overduin, Michael, et Mansoore Esmaili. « Structures and Interactions of Transmembrane Targets in Native Nanodiscs ». SLAS DISCOVERY : Advancing the Science of Drug Discovery 24, n^o 10 (26 juin 2019) : 943–52. http://dx.doi.org/10.1177/2472555219857691.

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Transmembrane proteins function within a continuous layer of biologically relevant lipid molecules that stabilizes their structures and modulates their activities. Structures and interactions of biological membrane–protein complexes or “memteins” can now be elucidated using native nanodiscs made by poly(styrene co-maleic anhydride) derivatives. These linear polymers contain a series of hydrophobic and polar subunits that gently fragment membranes into water-soluble discs with diameters of 5–50 nm known as styrene maleic acid lipid particles (SMALPs). High-resolution structures of memteins that include endogenous lipid ligands and posttranslational modifications can be resolved without resorting to synthetic detergents or artificial lipids. The resulting ex situ structures better recapitulate the in vivo situation and can be visualized by methods including cryo-electron microscopy (cryoEM), electron paramagnetic resonance (EPR), mass spectrometry (MS), nuclear magnetic resonance (NMR) spectroscopy, small angle x-ray scattering (SAXS), and x-ray diffraction (XRD). Recent progress including 3D structures of biological bilayers illustrates how polymers and native nanodiscs expose previously inaccessible membrane assemblies at atomic resolution and suggest ways in which the SMALP system could be exploited for drug discovery.

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Kim, Hyun-Soo, Tahir Sattar, Seong-Joo Sim, Myungsu Seo et Bong-Soo Jin. « Enhanced Structural Stability and Capacity Retention of Ni-Rich LiNi_0.91Co_0.06Mn_0.03O₂ Cathode Material By Dual Doping and Coating for Libs ». ECS Meeting Abstracts MA2022-02, n^o 7 (9 octobre 2022) : 2431. http://dx.doi.org/10.1149/ma2022-0272431mtgabs.

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Nickel-rich layered cathode material has been received a lot of attention due to their superior cycle-ability, high energy density and improved safety. However, there are some issues which are needed to be resolved to ensure the long term application. The hostile attack of electrolyte with the charged cathode electrode results in the growth of thick solid electrolyte interphase (SEI) at the expense of Li+ consumption and increase in interfacial resistance. In addition, de/intercalation of Li+ leads to the continuous contraction and expansion of lattice structure that leads to the crack formation in the active material particles during extended cycling. In this work, a facile technique has been adopted to resolve the mentioned problems. In this study, Li3BO3 has been coated on the NCM surface to protect the active material against the continuous attack of electrolyte and boron is doped to enhance the structural stability of LiNi0.91Co0.06Mn0.03O2 NCM cathode material. The samples were characterized by XPS, XRD, SEM and TEM and the electrochemical properties were measured by assembling the coin cells. The XRD results confirm the shifting of (003) diffraction peak towards low angle which validates the boron doping in the crystal structure. The presence of B1s is confirmed on the surface of modified NCM by XPS analysis. The FETEM images shows a uniform and distinct coating layer of 12 nm on the surface of 0.05 wt% coated NCM. The 0.05 wt% NCM samples offers the highest discharge capacity of 215.3 mAh g-1 at 0.1C and capacity retention of 81.6% at 0.5C (1C = 202 mA g-1) after 100 cycles. The reason behind enhanced cycling is the high bond dissociation energy of B−O (ΔHf298 = 402 kJ mol−1) than Ni–O (ΔHf298 = 391.6 kJ mol−1), Co–O (ΔHf298 = 368 kJ mol−1) and even Mn–O (ΔHf298 = 402 kJ mol−1). Even at 2C cycling, LBO-0.05 NCM sample demonstrated a capacity retention of 79.4% after 100 cycles while pristine shows only 67.3%. The modified samples displayed superior rate performance as compare to pristine NCM, especially at high current density. The cyclic voltammetry and EIS results are in-line with the cycling data. The presence of B3+ doping in host structure and Li3BO3 coating on the NCM surface results in the superior electrochemical performance of modified NCM.

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Neves, Cristina S., Alexandre C. Bastos, Andrei N. Salak, Maksim Starykevich, Daisy Rocha, Mikhail L. Zheludkevich, Angela Cunha, Adelaide Almeida, João Tedim et Mário G. S. Ferreira. « Layered Double Hydroxide Clusters as Precursors of Novel Multifunctional Layers : A Bottom-Up Approach ». Coatings 9, n^o 5 (21 mai 2019) : 328. http://dx.doi.org/10.3390/coatings9050328.

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The specific microstructure of aluminum alloys is herein explored to grow spatially-resolved layered double hydroxide (SR-LDH) clusters on their surface. Upon chemical modification of LDHs via intercalation, adsorption and grafting with different functional molecules, novel surface-engineered surfaces were obtained. Crystal structure and phase composition were analyzed by X-ray diffraction (XRD) and surface morphology was observed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectrometry (GDOES) were used to correlate structural changes upon ion-exchange and interfacial modifications with chemical composition and surface profiles of the SR-LDH films, respectively. The protection conferred by these films against localized corrosion was investigated at microscale using the scanning vibrating electrode technique (SVET). LDH-NO3 phase was obtained by direct growth onto AA2024 surface, as evidenced by (003) and (006) XRD diffraction reflections. After anion exchange of nitrate with 2-mercaptobenzothiazole (MBT) there was a decrease in the SR-LDH thickness inferred from GDOES profiles. The subsequent surface functionalization with HTMS was confirmed by the presence of Si signal in XPS and GDOES analyses, leading to an increase in the water contact angle (c.a 144° ± 3°). SVET measurements of the SR-LDH films revealed exceptional corrosion resistance, whereas the bioluminescent bacteria assay proved the anti-microbial character of the obtained films. Overall the results obtained show an effective corrosion protection of the SR-LDHs when compared to the bare substrate and the potential of these films for biofouling applications as new Cr-free pre-treatments.

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Brune, Alicia B., Gregory P. Holland, Jeffery L. Yarger et William T. Petuskey. « Structure and Properties in Synthetic MSUM and the Corresponding Biomaterial ». MRS Advances 1, n^o 36 (2016) : 2551–56. http://dx.doi.org/10.1557/adv.2016.481.

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ABSTRACTAt the MRS Fall 2014 Meeting, Symposium E, we reported on morphologies, fragmentation, and hardness in synthetic hydrogen urate monohydrate (monosodium urate monohydrate, MSUM, or MSU) crystals. We are now presenting further characterization results, including some from the biomaterial that forms in humans with gout disease: The fanning of radiating blades (needles) in spherulitic grains of synthetic MSUM was examined by microscopy techniques. These and previous data are consistent with an interpretation in terms of the crystallographic parameters in the unit cell, and the presence of dislocation arrays at low angle boundaries. The kinetics of such branched growth is here related to thermodynamic properties and super-saturation levels. Secondary nucleation is an additional mechanism leading to more complex morphologies. Differences in overall growth rates, under conditions of either branched or single needle growth, are considered in relation to gout. Novel powder XRD and solid state NMR data show, respectively, preferred orientation in the biomaterial, and the potential of NMR for identifying and characterizing MSUM in specific environments, helping to resolve pending questions in gout. Present results are anticipated to be useful for designing bio-inspired and bio-mimetic materials, regarding morphologies, overall growth rates, and mechanical properties.

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Wang, Haijing, Boqin Sun, Zheng Yang, Scott J. Seltzer et Marcus O. Wigand. « Accurate Rock Mineral Characterization With Nuclear Magnetic Resonance ». Petrophysics – The SPWLA Journal of Formation Evaluation and Reservoir Description 63, n^o 3 (1 juin 2022) : 405–17. http://dx.doi.org/10.30632/pjv63n3-2022a8.

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Nuclear magnetic resonance (NMR) logging is a powerful formation evaluation technology that provides mineralogy-independent porosity and helps distinguish clay-bound water, capillary-bound water, and free fluids. NMR logging tool generally operates at 1H NMR frequency of 2 MHz (magnetic field, B0 ~ 470 Gauss) or lower. At this magnetic field, it is only feasible to detect 1H signal from fluids in pores and rely on the relaxation time variation to characterize fluid and pore types. As magnetic field strength increases, NMR sensitivity increases very dramatically, and NMR signals from solid matrix become easier to be detected in high field. For example, NMR at 600 MHz is about 5,000 times more sensitive than the NMR at 2 MHz. Meanwhile, the spectral resolution of high-field NMR is also greatly increased, and high-field NMR spectrum can resolve the detailed differences between molecule types. Therefore, the high sensitivity and spectral resolution of high-field NMR open a totally new horizon for the characterization of geological samples, especially in organic shale reservoirs, in which organic matter and complex mineralogy remain challenging to be accurately characterized. In this work, we report high-field NMR applications for mineral characterization using a 600-MHz NMR spectrometer equipped with a multichannel and Magic-Angle Spinning (MAS) probe. Compared to X-ray diffraction (XRD), which is the primary tool for identifying and quantifying the mineralogy of crystalline compounds in geological samples based on Bragg’s diffraction, NMR can provide more compositional and structural information for noncrystalline compounds due to its sensitivity to local electronic binding structures. Here we demonstrate such an application of high-resolution 27Al NMR to determine the composition and bonding chemistry of 27Al as a fingerprint for a wide range of minerals. The ratio of 27Al at tetrahedral and octahedral binding sites is quantitative and essential to differentiate the dioctahedral and trioctahedral phases. 27Al NMR can also distinguish plagioclase series members ranging from albite to anorthite end members, where Na and Ca atoms can substitute for each other. 27Al NMR can be further combined with 1H, 13C, 29Si, 25Mg, 23Na, and 31P for more detailed mineral determination and clay typing. Our results show that, combined with XRD, this group of high-field NMR spectroscopic methods can greatly improve the accuracy of rock mineral and formation clay characterization in tight-rock and unconventional reservoirs.

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Orsilli, Jacopo, Alessandro Migliori, Roman Padilla Alvarez, Marco Martini et Anna Galli. « AR-XRF measurements and data treatment for the evaluation of gildings samples in the Cultural Heritage ». Journal of Analytical Atomic Spectrometry, 2023. http://dx.doi.org/10.1039/d2ja00227b.

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Subramanian, S., D. A. Muller, J. Silcox et S. L. Sass. « Ni-Enrichment and its Influence on the Structure Chemistry and Bonding of Grain Boundaries in Ni3Al ». MRS Proceedings 364 (1994). http://dx.doi.org/10.1557/proc-364-333.

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AbstractSmall angle [001] twist boundaries and [001[(110) tilt boundaries in B-free and B-doped Ni-rich Ni3AI (76 at. pet. Ni) were examined using conventional electron microscopy techniques as well as annular dark field (ADF) imaging, X-ray Fluorescence (XRF) and spatially resolved electron energy loss spectroscopy (EELS) in an UHV scanning transmission electron microscope. The interface structure consists of periodically spaced pairs of a/2<10> partial dislocations, linked by an antiphase boundary (APB). An analysis of the separation of the partials gives APB energies which are lower than in bulk Ni3Al and which decrease with increasing misorientation angle. EELS, XRF and ADF imaging demonstrate that the APBs are Ni-rich. The observations on the APB chemistry and energy taken together lead to the conclusion that Ni-enrichment occurs to lower boundary energy by decreasing the number of high energy Al-Al bonds across the APB. These results on small angle boundaries lead to the suggestion that Ni-enrichment also occurs at large angle boundaries to decrease the number of high energy bonds across the interface.

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Yorita, Daisuke, Ulrich Henne et Christian Klein. « Time-resolved pressure-sensitive paint measurements for cryogenic wind tunnel tests ». CEAS Aeronautical Journal, 10 janvier 2023. http://dx.doi.org/10.1007/s13272-022-00637-8.

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AbstractA first time-resolved pressure-sensitive paint (PSP) test campaign at the European Transonic Wind Tunnel (ETW) was conducted within the research initiative “Unsteady flow and interaction phenomena at High Speed Stall conditions”. One of the objectives of this wind tunnel campaign was to resolve time-series of surface pressure distributions caused by complex 3-D buffet phenomena on a full-span airplane model XRF-1 transport aircraft configuration. At higher angle-of-attack and high Mach number, pressure fluctuations with a frequency of several hundred Hertz are expected to occur on the main wing and the horizontal tail plane (HTP) caused by the buffet effect. To capture the expected buffet phenomena by PSP, the German Aerospace Center developed a time-resolved PSP measurement and data acquisition system as well as a post-processing method for measurements in ETW. The measurements were conducted on the main wing and HTP simultaneously, with a camera frame rate of up to 2 kHz. The transonic buffet phenomena were observed at the flight relevant Reynolds number Re = 12.9 × 106 and Re = 25.0 × 106. The time-varying surface pressure distribution on the model was successfully captured by PSP. The time-series and spectra of both PSP and pressure transducer data match very well.

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Ohtani, M., T. Fukumura, A. Ohtomo, T. Kikuchi, K. Omote, H. Koinuma et M. Kawasaki. « High Throughput X-ray Diffractometer for Combinatorial Epitaxial Thin Films ». MRS Proceedings 700 (2001). http://dx.doi.org/10.1557/proc-700-s3.8.

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AbstractWe report on the development of a high throughput x-ray diffractometer that concurrently measures spatially resolved x-ray diffraction (XRD) spectra of epitaxial thin films integrated on a substrate. A convergent x-ray is focused into a stripe on a substrate and the diffracted beam is detected with a two-dimensional x-ray detector, so that the snapshot image represents a mapping of XRD intensity with the axes of the diffraction angle and the position in the sample. High throughput characterization of crystalline structure is carried out for a BaxSr1-xTiO3 composition-spread film on a SrTiO3 substrate. Not only the continuous spread of the composition (x), but also the continuous spread of the growth temperature (T) are given to the film by employing a special heating method. The boundary between the strained lattice and relaxed lattice is visualized by the concurrent XRD as functions of x and T in a high throughput fashion.

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Pickup, DM, G. Mountjoy, RJ Newport, ME Smith, GW Wallidge et MA Roberts. « In Situ Studies of the Processing of Sol-Gel Produced Amorphous Materials Using Xanes, Saxs and Curved Image Plate XRD ». MRS Proceedings 590 (1999). http://dx.doi.org/10.1557/proc-590-119.

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ABSTRACTSol-gel produced mixed oxide materials have been extensively studied using conventional, ex situ structural techniques. Because the structure of these materials is complex and dependent on preparation conditions, there is much to be gained from in situ techniques: the high brightness of synchrotron x-ray sources makes it possible to probe atomic structure on a short timescale, and hence in situ. Here we report recent results for mixed titania- (and some zirconia-) silica gels and xerogels. Titania contents were in the range 8–18 mol%, and heat treatments up to 500°C were applied. The results have been obtained from intrinsically rapid synchrotron x-ray experiments: i) time-resolved small angle scattering, using a quadrant detector, to follow the initial stages of aggregation between the sol and the gel; ii) the use of a curved image plate detector in diffraction, which allowed the simultaneous collection of data across a wide range of scattering at high count rate, to study heat treatments; and iii) x-ray absorption spectroscopy to explore the effects of ambient moisture on transition metal sites.

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Löffler, Jörg F., X. P. Tang, Yue Wu et William L. Johnsona. « Structural and Electronic Properties of Zr-Ti-Cu-Ni-Be Alloys ». MRS Proceedings 644 (2000). http://dx.doi.org/10.1557/proc-644-l1.9.

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AbstractWe present crystallization studies on Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit1) and on other alloys, where the (Zr,Ti) and (Cu,Be) contents, along the line in composition space connecting Vit1 and Zr46.8Ti8.2Cu7.5Ni10Be27.5 (Vit4), were varied. Results from x-ray diffraction (XRD), small-angle neutron scattering (SANS) and differential scanning calorimetry (DSC) are combined to describe the crystallization behavior of these alloys at deep undercooling. SANS gives evidence for decomposition and the formation of nanometer sized crystals below a critical temperature Tc, which varies drastically as a function of composition. When Tc intersects with the glass transition temperature Tg, changes in the crystallization behavior are observed by DSC and XRD. At annealing temperatures near Tg, XRD resolves quasicrystalline phases for all alloy compositions from Vit1 to Vit4. From 9Be nuclear magnetic resonance (NMR) experiments performed on Vit1 upon annealing, we obtain information about the electronic structure and volume fraction of Be containing crystalline and quasicrystalline phases.

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Hölzing, Astrid, Roland Schurr, Stefan Jost, Jörg Palm, Klaus Deseler, Peter J. Wellmann et Rainer Hock. « Real-time Investigations on the Formation of CuIn(S,Se)2 while annealing precursors with varying sulfur content ». MRS Proceedings 1165 (2009). http://dx.doi.org/10.1557/proc-1165-m02-02.

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AbstractCIS based chalcopyrite absorber materials are usually substituted in the cation and anion lattice to yield mixed pentanary crystals with the general composition Cu(In,Ga)(Se,S)2 to achieve an optimised adaptation of the semiconductor bandgap to the terrestrial solar spectrum. Real-time investigations during the annealing of stacked elemental layers (SEL) of sputtered metals Cu and In and evaporated chalcogens S and Se with varying ratios were performed by angle-dispersive time-resolved XRD (X-ray diffraction) measurements. After qualitative phase analysis the measured powder diagrams were quantitatively analysed by the Rietveld method, the phases formed determined and their reaction kinetics obtained. Ternary indium and copper sulfoselenides form by the sulfoselenisation of the intermetallic alloy yielding different educts for the chalcopyrite formation with varying sulfur content. For S/(S+Se) ≥ 0.5 the formation of the chalcopyrite CuIn(S,Se)2 is similar to the crystallisation path of CuInS2. With increasing amount of selenium (S/(S+Se) = 0.25) different ternary sulfoselenides contribute to the semiconductor formation. For small amounts of sulfur, i.e. S/(S+Se) ≤ 0.1, the chalcopyrite crystallisation proceeds comparable to the one observed for sulfur-free Cu-In-Se precursors. The formation of CuIn(S,Se)2 is accelerated and proceeds mainly after the peritectic decomposition of Cu(S,Se) to Cu2(S,Se). The sulfur content determines the crystallisation temperature of the semiconductor because Cu(S,Se) decomposes at higher temperatures with increasing sulfur. Upon heating S ↔ Se exchange reactions take place in the Cu-S-Se and Cu-In-S-Se system.

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