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Synchrotron Radiation (synchrotron + radiation)
Terms modified by Synchrotron Radiation Selected AbstractsDETERMINATION OF PIGMENTS AND BINDERS IN POMPEIAN WALL PAINTINGS USING SYNCHROTRON RADIATION , HIGH-RESOLUTION X-RAY POWDER DIFFRACTION AND CONVENTIONAL SPECTROSCOPY , CHROMATOGRAPHYARCHAEOMETRY, Issue 2 2010A. DURAN The employment of synchrotron techniques complemented by conventional laboratory systems has allowed us to deepen and improve our knowledge of Roman wall painting procedures. The palette identified in wall paintings from Pompeii and Herculaneum from the second century bc includes goethite, hematite, cinnabar, glauconite, Egyptian blue, and other components such as calcite and aragonite. Proof of the use of organic binders is provided by FTIR and PY,GC/MS. Therefore, the possibility of the use of ,a secco' techniques cannot be ruled out. Pigments in wall paintings are usually found in small percentages and conventional X-ray diffractometers do not detect them. Synchrotron radiation , high-resolution X-ray powder diffraction has allowed identification with only a few micrograms of sample. [source] Oriented Grain Growth Analyses With In Situ Annealing Experiments Using High Energy Synchrotron RadiationADVANCED ENGINEERING MATERIALS, Issue 3 2010Caterina Elisabetta Tommaseo The development of the recrystallization and annealing textures of Al,Mn alloys with 0.4, 0.7 and 1,wt.-% manganese is analyzed using specific techniques that allow the detection of changes in grain orientation during in situ annealing. In order to investigate the evolution of texture components during annealing, highly rolled samples were annealed from room temperature to 500,°C at a constant heating rate. The advantage of in situ annealing experiments using synchrotron radiation is the detection of grain orientations over time, which allows observation of the development of the recrystallization and annealing textures in a sample. In fact, the recrystallization and annealing textures in the Al,0.4Mn are characterized by an interruption in the detection of most of the grain orientations between 380 and 425,°C and by competition between the cube {001}<100>, {011}<1-33>, {011}<0-11> and rotated-cube {001}<110> grain orientations, where the latter is detected until the end of the experiment. In the Al,0.7Mn sample a competition between the cube {001}<100>, {011}<100>, and rotated cube {001}<110>, {011}<0,11> grain orientations is observed. In the sample with the highest manganese concentration (1,wt.-%) an unhindered grain growth of all possible grain orientations with a high amount of the {011}<0-11> grain orientation is observed. The evolution of the resulting local textures is discussed in terms of preferentially oriented grain growth depending on the temperature and manganese concentration. [source] Principles of Highly Resolved Determination of Texture and Microstructure using High-Energy Synchrotron Radiation,ADVANCED ENGINEERING MATERIALS, Issue 6 2009Helmut Klein Abstract Diffraction imaging with hard X-rays (high-energy synchrotron radiation) using the detector sweeping techniques allows measurement of the texture and microstructure of polycrystalline materials with high orientation- and location-resolution. These techniques provide continuous two-dimensional images of different sections and projections of the six-dimensional "orientation-location" space. For the high orientation resolution case, it is possible to measure the orientation and location coordinates of up to 105 individual grains simultaneously. From these parameters, the grain size and shape can also be obtained, yielding the complete orientation stereology of the polycrystalline aggregate, which is required for its complete characterization. For the high location resolution case, the intensity at any point of the diagrams corresponds to a pole density as a function of the orientation-location space. [source] Workshop on X-ray Detectors for Synchrotron RadiationJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2004DOI: 10.1107/S090904950400926 First page of article [source] Processing of a Strong Biodegradable Poly[(R)-3-hydroxybutyrate] Fiber and a New Fiber Structure Revealed by Micro-Beam X-Ray Diffraction with Synchrotron RadiationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 11 2004Tadahisa Iwata Abstract Summary: Biodegradable poly[(R)-3-hydroxybutyrate] (P(3HB)) fibers with high tensile strength of 1.32 GPa were processed from ultra-high-molecular-weight P(3HB) by a method combining cold-drawing and two-step-drawing procedures at room temperature. The distribution of molecular structures in a mono-filament was analyzed by micro-beam X-ray diffraction with synchrotron radiation. It was revealed that the P(3HB) fiber has a new core-sheath structure consistent with two types of molecular conformations: a 21 helix conformation in the sheath region and a planar zigzag conformation in the core region. P(3HB) fiber processed by cold-drawing in ice water and two-step drawing at room temperature, and subsequently annealing at 50,°C. [source] 60 years of IUCr journalsACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2009André Authier In the 60 years since its birth in 1948, the number of journals published by the International Union of Crystallography has risen from one to eight. A brief account of the history of the forerunner of the IUCr journals, Zeitschrift für Kristallographie, is given. The context of the birth of the IUCr and the first of its journals, Acta Crystallographica, is recalled. The circumstances which led to the growth of Acta into several sections, at first A and B then, successively, C, D, E and F, and the launch of two new journals, the Journal of Applied Crystallography and the Journal of Synchrotron Radiation, are described. The transition from print-on-paper to electronic journals is also remembered. [source] Titelbild: Determination of Arsenic Poisoning and Metabolism in Hair by Synchrotron Radiation: The Case of Phar Lap (Angew. Chem.ANGEWANDTE CHEMIE, Issue 25 201025/2010) Nach achtzig Jahren hat eine Obduktion das Geheimnis um den Tod des berühmten Rennpferds Phar Lap gelüftet. I. Kempson und D. Henry beschreiben in ihrer Zuschrift auf S.,4333,ff. auffällige Arsenverteilungen und -verbindungen, die darauf hindeuten, dass Phar Lap das Gift Stunden vor seinem unerwarteten qualvollen Ende eingenommen hat. Diese außergewöhnliche Haaranalyse beleuchtet metabolische Prozesse nach der Arsenaufnahme. [source] Determination of Arsenic Poisoning and Metabolism in Hair by Synchrotron Radiation: The Case of Phar Lap,ANGEWANDTE CHEMIE, Issue 25 2010Neues Beweismaterial zum Tod des Rennpferds Phar Lap (siehe Photo) lieferten hochauflösende Röntgen-Fluoreszenz(XRF)- und Röntgen-Nahkantenabsorptions(XANES)-Analysen von Mähnenhaaren mithilfe von Synchrotronstrahlung. Die Ergebnisse deuten auf Arsenaufnahme und -metabolismus hin , das Rennpferd erlag folglich einer Vergiftung. [source] ChemInform Abstract: Synchrotron Radiation in Natural ScienceCHEMINFORM, Issue 18 2002several authors several authors Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Photolysis of rac -Leucine with Circularly Polarized Synchrotron RadiationCHEMISTRY & BIODIVERSITY, Issue 6 2010Abstract Amino acids that pass the RNA machinery in living organisms occur in L -configuration. The question on the evolutionary origin of this biomolecular asymmetry remains unanswered to this day. Amino acids were detected in artificially produced interstellar ices, and L -enantiomer-enriched amino acids were identified in CM-type meteorites. This hints at a possible interstellar/circumstellar origin of the amino acids themselves as well as their stereochemical asymmetry. Based upon the current knowledge about the occurrence of circularly-polarized electromagnetic radiation in interstellar environments, we subjected rac -leucine to far-UV circularly-polarized synchrotron radiation. Asymmetric photolysis was followed by an analysis in an enantioselective GC/MS system. Here, we report on an advanced photolysis rate of more than 99% for leucine. The results indicate that high photolysis rates can occur under the chosen conditions, favoring enantioselective photolysis. In 2014, the obtained results will be reexamined by cometary mission Rosetta. [source] Synchrotron radiation in soil and geosciencesJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2010Roberto Terzano [source] Evaluation of enamel crystallites in subsurface lesion by microbeam X-ray diffractionJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2009N. Yagi Early caries lesion is a demineralization process that takes place in the top 0.1,mm layer of tooth enamel. In this study, X-ray microbeam diffraction was used to evaluate the hydroxyapatite crystallites in the subsurface lesion of a bovine enamel section and the results are compared with those obtained by transversal microradiography, a method commonly used for evaluation of tooth mineral. Synchrotron radiation from SPring-8 was used to obtain a microbeam with a diameter of 6,µm. Wide-angle X-ray diffraction reports the amount of hydroxyapatite crystals, and small-angle X-ray scattering reports that of voids in crystallites. All three methods showed a marked decrease in the enamel density in the subsurface region after demineralization. As these diffraction methods provide structural information in the nanometre range, they are useful for investigating the mechanism of the mineral loss in early caries lesion at a nanometre level. [source] Synchrotron radiation and nanobiosciences , introductory overviewJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2005Eugenia Pechkova First page of article [source] Magnetisation dynamics of Fe nanoclusters exchange-coupled to magnetic substratesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2004C. Binns Abstract Synchrotron radiation was used to study exposed Fe nanoclusters with controlled sizes in the size range 140,270 atoms (1.5,1.8 nm) deposited in situ from a gas aggregation source on to magnetic vitrovac amorphous ribbons. Magnetic linear dichroism in the angular distribution (MLDAD) of the Fe 3p core level photoemission was used to show that the clusters are exchange-coupled to the substrate with an interface molecular field of about 20 T. The switching dynamics was studied on the nanosecond timescale by time-resolved spin-polarised photoemission. At low coverages, below the percolation threshold, when the film consists of separated islands the switching dynamics of the cluster islands is identical to the clean substrate. At around the percolation threshold, however, the data indicates that the magnetic reversal propagates faster in the cluster film than in the substrate. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A synchrotron study of (2R,5,S)-5,-benzyl-5-bromo-6-methoxyspiro[indane-2,2,-piperazine]-3,,6,-dione dimethylformamide solvateACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Gary S. Nichol Synchrotron radiation was used to study the structure of the title compound, C20H19BrN2O3·C3H7NO, which was obtained as fine fragile needle-shaped crystals by recrystallization from dimethylformamide (DMF), one molecule of which is incorporated per asymmetric unit into the crystal. The compound adopts a compact closed conformation with the orientation of the benzyl group such that the aryl ring is positioned over the piperazinedione ring, resulting in a Cspiro...Ctrans,C,CPh pseudo-torsion angle of ,3.3,(3)°. The five-membered ring is present in an expected envelope conformation and the six-membered piperazinedione ring adopts a less puckered boat-like conformation. Reciprocal amide-to-amide hydrogen bonding between adjacent piperazinedione rings and C,H...O interactions involving DMF molecules propagate in the crystal as a thick ribbon in the a -axis direction. [source] DETERMINATION OF PIGMENTS AND BINDERS IN POMPEIAN WALL PAINTINGS USING SYNCHROTRON RADIATION , HIGH-RESOLUTION X-RAY POWDER DIFFRACTION AND CONVENTIONAL SPECTROSCOPY , CHROMATOGRAPHYARCHAEOMETRY, Issue 2 2010A. DURAN The employment of synchrotron techniques complemented by conventional laboratory systems has allowed us to deepen and improve our knowledge of Roman wall painting procedures. The palette identified in wall paintings from Pompeii and Herculaneum from the second century bc includes goethite, hematite, cinnabar, glauconite, Egyptian blue, and other components such as calcite and aragonite. Proof of the use of organic binders is provided by FTIR and PY,GC/MS. Therefore, the possibility of the use of ,a secco' techniques cannot be ruled out. Pigments in wall paintings are usually found in small percentages and conventional X-ray diffractometers do not detect them. Synchrotron radiation , high-resolution X-ray powder diffraction has allowed identification with only a few micrograms of sample. [source] Oriented Grain Growth Analyses With In Situ Annealing Experiments Using High Energy Synchrotron RadiationADVANCED ENGINEERING MATERIALS, Issue 3 2010Caterina Elisabetta Tommaseo The development of the recrystallization and annealing textures of Al,Mn alloys with 0.4, 0.7 and 1,wt.-% manganese is analyzed using specific techniques that allow the detection of changes in grain orientation during in situ annealing. In order to investigate the evolution of texture components during annealing, highly rolled samples were annealed from room temperature to 500,°C at a constant heating rate. The advantage of in situ annealing experiments using synchrotron radiation is the detection of grain orientations over time, which allows observation of the development of the recrystallization and annealing textures in a sample. In fact, the recrystallization and annealing textures in the Al,0.4Mn are characterized by an interruption in the detection of most of the grain orientations between 380 and 425,°C and by competition between the cube {001}<100>, {011}<1-33>, {011}<0-11> and rotated-cube {001}<110> grain orientations, where the latter is detected until the end of the experiment. In the Al,0.7Mn sample a competition between the cube {001}<100>, {011}<100>, and rotated cube {001}<110>, {011}<0,11> grain orientations is observed. In the sample with the highest manganese concentration (1,wt.-%) an unhindered grain growth of all possible grain orientations with a high amount of the {011}<0-11> grain orientation is observed. The evolution of the resulting local textures is discussed in terms of preferentially oriented grain growth depending on the temperature and manganese concentration. [source] Synchrotron-Based Micro-CT and Refraction-Enhanced Micro-CT for Non-Destructive Materials Characterisation,ADVANCED ENGINEERING MATERIALS, Issue 6 2009Bernd R. Müller Abstract X-ray computed tomography is an important tool for non-destructively evaluating the 3-D microstructure of modern materials. To resolve material structures in the micrometer range and below, high brilliance synchrotron radiation has to be used. The Federal Institute for Materials Research and Testing (BAM) has built up an imaging setup for micro-tomography and -radiography (BAMline) at the Berliner storage ring for synchrotron radiation (BESSY). In computed tomography, the contrast at interfaces within heterogeneous materials can be strongly amplified by effects related to X-ray refraction. Such effects are especially useful for materials of low absorption or mixed phases showing similar X-ray absorption properties that produce low contrast. The technique is based on ultra-small-angle scattering by microstructural elements causing phase-related effects, such as refraction and total reflection. The extraordinary contrast of inner surfaces is far beyond absorption effects. Crack orientation and fibre/matrix debonding in plastics, polymers, ceramics and metal-matrix-composites after cyclic loading and hydro-thermal aging can be visualized. In most cases, the investigated inner surface and interface structures correlate to mechanical properties. The technique is an alternative to other attempts on raising the spatial resolution of CT machines. [source] Principles of Highly Resolved Determination of Texture and Microstructure using High-Energy Synchrotron Radiation,ADVANCED ENGINEERING MATERIALS, Issue 6 2009Helmut Klein Abstract Diffraction imaging with hard X-rays (high-energy synchrotron radiation) using the detector sweeping techniques allows measurement of the texture and microstructure of polycrystalline materials with high orientation- and location-resolution. These techniques provide continuous two-dimensional images of different sections and projections of the six-dimensional "orientation-location" space. For the high orientation resolution case, it is possible to measure the orientation and location coordinates of up to 105 individual grains simultaneously. From these parameters, the grain size and shape can also be obtained, yielding the complete orientation stereology of the polycrystalline aggregate, which is required for its complete characterization. For the high location resolution case, the intensity at any point of the diagrams corresponds to a pole density as a function of the orientation-location space. [source] Effect of Microstructure on Residual Stresses in Sintered Diamond,Metal Composites,ADVANCED ENGINEERING MATERIALS, Issue 6 2009U. Selvadurai-Laßl As residual stresses can reduce the lifetime of diamond-cobalt composite cutting tools, the composite stress state needs to be understood very well. Thus, the effect of microstructure on the residual stresses was investigated here. Stress measurements were carried out in the cobalt matrix by X-ray diffraction (XRD) and Synchrotron-XRD (SXRD). In addition to global stress measurements, investigations of stresses in small cobalt areas near the diamonds were performed by high brilliant synchrotron radiation using different apertures. [source] Multi-scale Microstructure Characterization of Solid Oxide Fuel Cell Assemblies With Ultra Small-Angle X-Ray Scattering,ADVANCED ENGINEERING MATERIALS, Issue 6 2009Andrew J. Allen Ultra small angle X-ray scattering with synchrotron radiation is applied to assess the pore space of a highly complex solid oxide fuel cell assembly. The instrument permits to record scattering curves covering a size range from 1,nm to several ,m in a fine step width of 15,,m. [source] Engineering of a monomeric and low-glycosylated form of human butyrylcholinesteraseFEBS JOURNAL, Issue 2 2002Expression, characterization, crystallization, purification Human butyrylcholinesterase (BChE; EC 3.1.1.8) is of particular interest because it hydrolyzes or scavenges a wide range of toxic compounds including cocaine, organophosphorus pesticides and nerve agents. The relative contribution of each N-linked glycan for the solubility, the stability and the secretion of the enzyme was investigated. A recombinant monomeric BChE lacking four out of nine N-glycosylation sites and the C-terminal oligomerization domain was stably expressed as a monomer in CHO cells. The purified recombinant BChE showed catalytic properties similar to those of the native enzyme. Tetragonal crystals suitable for X-ray crystallography studies were obtained; they were improved by recrystallization and found to diffract to 2.0 Å resolution using synchrotron radiation. The crystals belong to the tetragonal space group I422 with unit cell dimensions a = b = 154.7 Å, c = 124.9 Å, giving a Vm of 2.73 Å3 per Da (estimated 60% solvent) for a single molecule of recombinant BChE in the asymmetric unit. The crystal structure of butyrylcholinesterase will help elucidate unsolved issues concerning cholinesterase mechanisms in general. [source] Shape-prediction of 3D PTFE Microstructures Fabricated by Synchrotron Radiation AblationIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2010Mitsuhiro Horade Non-member Abstract This article describes the calculation of the predictions of the deformed shapes of three-dimensional polytetrafluoroethylene (PTFE) microstructures fabricated by direct etching with a synchrotron radiation (SR) light source. As PTFE is a remarkable material, there is a lot of expectation regarding its applications in various devices. We did research on establishing a highly accurate three-dimensional technology for microfabricating PTFE by using an SR-light source because we aimed at applying this material in future devices. We built a shape-prediction technique as part of this research. Since this technique had the advantage of predicting shapes without experimentation, both fabrication time and cost could be reduced. It is also a useful technique for investigating and clarifying processing mechanisms. We compared structures fabricated in an experiment and the shapes computed with shape-prediction. The shape-prediction results were mostly in agreement with those from the experiment. As PTFE demonstrated excellent material characteristics, especially in its resistance to chemicals, it should be possible to use it in the fabrication of micro total analysis systems (µ-TAS) for biomedical applications. We expect that these applications will benefit from (based on) the designs which are predicted utilizing this calculation method. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] One-Dimensional Quantum-Confinement Effect in ,-Fe2O3 Ultrafine Nanorod Arrays,ADVANCED MATERIALS, Issue 19 2005L. Vayssieres A 1D quantum confinement effect in hematite thin films consisting of oriented ultrafine nanorod bundles (see Figure) is investigated by resonant inelastic x-ray scattering of synchrotron radiation. The direct observation of a substantial bandgap increase compared to bulk hematite is revealed. This finding shows that these low-dimensional nanomaterials may be used for the generation of hydrogen by solar illumination without applied bias. [source] Teaching crystallography to undergraduate physical chemistry studentsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5-2 2010Virginia B. Pett Teaching goals, laboratory experiments and homework assignments are described for teaching crystallography as part of two undergraduate physical chemistry courses. A two-week teaching module is suggested for introductory physical chemistry, including six to eight classroom sessions, several laboratory experiences and a 3,h computer-based session, to acquaint undergraduate physical chemistry students with crystals, diffraction patterns, the mathematics of structure determination by X-ray diffraction, data collection, structure solution and the chemical insights available from crystal structure information. Student projects and laboratory work for three to four weeks of an advanced physical chemistry course are presented. Topics such as symmetry operators, space groups, systematic extinctions, methods of solving the phase problem, the Patterson map, anomalous scattering, synchrotron radiation, crystallographic refinement, hydrogen bonding and neutron diffraction all lead to the goal of understanding and evaluating a crystallographic journal article. Many of the ideas presented here could also be adapted for inorganic chemistry courses. [source] In situ diffraction strain analysis of elastically deformed polycrystalline thin films, and micromechanical interpretationJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2009D. Faurie In situ tensile tests have been carried out under synchrotron radiation on supported gold (Au) thin films exhibiting a pronounced crystallographic texture. The 2, shift of X-ray diffraction lines has been recorded for different specimen orientations and several loading levels in the elastic domain. The data obtained demonstrate the large strain heterogeneities generated within the specimen because of the intergranular interactions associated with the large elastic anisotropy of Au grains. To interpret these results, the use of a multi-scale micromechanical approach is unavoidable. The theoretical background of such methods is described, and the points where exact results can be obtained and where approximations have to be introduced are highlighted. It is shown that the Vook,Witt model, for which a general formulation is provided, is the exact solution for polycrystals exhibiting a laminate microstructure, which is a significant departure from the standard thin-film microstructures. Among several standard models used in the field, the self-consistent model is the only one that reproduces the experimental data correctly. This is achieved by accounting for the actual crystallographic texture of the specimen, and assuming pancake-shaped two-point statistics for the morphological texture. A discussion of the limitations of this approach, originally developed for bulk materials, is given for the specific case of thin films. [source] Reciprocal-space imaging of a real quasicrystal.JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2008A feasibility study with PILATUS 6M How many of the theoretically densely distributed Bragg reflections of a quasicrystal can be observed employing an area detector and synchrotron radiation? How does the reflection density of a real quasicrystal change as a function of exposure time, and what is the minimum distance between reflections? What does the distribution of diffuse scattering look like? To answer these questions, the Bragg reflection density of a perfect icosahedral quasicrystal with composition Al64Cu23Fe13 was measured employing a novel type of single-photon-counting X-ray pixel detector, PILATUS 6M, which allows noise-free data collection with the extraordinarily large dynamic range of 20,bit. The reflection density was found to be two orders of magnitude lower than expected for a strictly quasiperiodic structure. Moreover, diffuse scattering reflects significant structural disorder, breaking six-dimensional F -lattice symmetry. These findings have some implications for the interpretation of physical properties. [source] Tracking reflections through cryogenic cooling with topographyJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3 2006Jeffrey J. Lovelace The mosaic structure of a single protein crystal was analyzed by reflection profiling and topography using highly parallel and monochromatic synchrotron radiation. Fine-,-sliced diffraction images (0.002° stills) were collected using a conventional large-area CCD detector in order to calculate reflection profiles. Fine-,-sliced topographic data (0.002°) stills were collected with a digital topography system for three reflections in a region where the Lorentz effect was minimized. At room temperature, several different mosaic domains were clearly visible within the crystal. Without altering the crystal orientation, the crystal was cryogenically frozen (cryocooled) and the experiment was repeated for the same three reflections. Topographs at cryogenic temperatures reveal a significantly increased mosaicity, while the original domain structure is maintained. A model for the observed changes during cryocooling is presented. [source] A new technique for angle-dispersive powder diffraction using an energy-dispersive setup and synchrotron radiationJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2004Yanbin Wang A new diffraction technique for combined angle- and energy-dispersive structural analysis and refinement (CAESAR), by collecting angle-dispersive data using a solid-state detector (SSD) and white synchrotron radiation, is introduced. By step scanning a well calibrated SSD over a limited 2, range, a series of one-dimensional energy-dispersive data (intensity versus energy) are obtained as a function of 2,. The entire intensity (Int) data set consists of several thousand channels covering a range of photon energies, E (up to ,150,keV), at each of the ,1000 2, steps, forming a 2,4 mega-element two-dimensional array, Int(E, 2,). These intensity data are then regrouped according to photon energies, which are defined in the multichannel SSD as individual channels, yielding a large number of intensity versus 2, (angle-dispersive) data sets, Int(E = const., 2,), each of which corresponds to a given photon energy or wavelength. The entire data set, selected subsets or composite scans can be used for multiple data set Rietveld refinement. Data collected both on ,-Al2O3 (a NIST diffraction standard) at ambient conditions and on a mixture of MgO and Au at high pressure were analyzed using the Rietveld technique, with varying schemes of data treatment. Furthermore, it is demonstrated that data within certain energy bands (,E/E = ±10%) may be binned together to improve counting statistics in a composite angle-dispersive scan, even when collected with much coarser scan steps of 0.1 or 0.2°. This technique is useful for high-pressure as well as general purpose powder diffraction studies that have limited X-ray access to the sample using synchrotron radiation. Several advantages are discussed. [source] Phase composition depth profiles using spatially resolved energy dispersive X-ray diffractionJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2004Andrew C. Jupe Spatially resolved energy dispersive X-ray diffraction, using high-energy synchrotron radiation (,35,80,keV), was used nondestructively to obtain phase composition profiles along the radii of cylindrical cement paste samples to characterize the progress of the chemical changes associated with sulfate attack on the cement. Phase distributions were acquired to depths of ,4,mm below the specimen surface with sufficient spatial resolution to discern features less than 200,µm thick. The experimental and data analysis methods employed to obtain quantitative composition profiles are described. The spatial resolution that could be achieved is illustrated using data obtained from copper cylinders with a thin zinc coating. The measurements demonstrate that this approach is useful for nondestructively visualizing the sometimes complex transformations that take place during sulfate attack on cement-based materials. These transformations can be spatially related to microstructure as seen by computed microtomography. [source] | |||||||||||||||||||