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Most engineering structural metallic alloys are used in polycrystalline form. The nature of the mechanical response of these systems is complex and hierarchical, spanning a range of scales. Lattice strains, distortions and defects (notably, dislocations) nucleate, interact, pile up at grain boundaries and self-organize at the (sub)micrometre scale. Individual grains experience strong interactions with their neighbours and geometric features (cracks, notches). Groups of grains sharing common orientation find themselves embedded within large ensembles possessing certain statistical properties (size distributions, preferred orientation, etc.). Ultimately, the macroscopic properties of grain aggregates are determined by this hierarchy of interactions. Notably, while collective properties such as stiffness are relatively well represented by averages, strength properties associated with fracture, fatigue crack propagation, creep and damage show a strong dependence on the local microscopic conditions of the ‘weakest link’. Ongoing improvements in the spatial resolution of X-ray imaging and tomography and the availability of micro-focused X-ray beams open up a number of opportunities for the study of the structure and deformation at (sub)micrometre scales. Fundamental questions concerning the scale dependence and strain gradient effects in solids can now be tackled by the combination of synchrotron X-ray methods and suitably refined deformation modelling. In this study, a range of methodologies and experimental configurations are presented that have allowed us to develop improved insight into the physical mechanisms of plastic deformation in ductile metallic alloys. Examples include white-beam energy-dispersive diffraction, micro-beam Laue diffraction, scanning micro-beam diffraction topography, high-resolution reciprocal space mapping and imaging. Connections are established with advanced numerical models of polycrystal deformation using strain gradient plasticity and discrete dislocation dynamics modelling.
The new synchrotron light source PETRA-III produced its first beam last year. The extremely high brilliance of PETRA-III and the large energy range of many of its beamlines make it useful for a wide range of experiments, particularly in materials science. The detectors at PETRA-III will need to meet several requirements, such as operation across a wide dynamic range, high-speed readout and good quantum efficiency even at high photon energies. PETRA-III beamlines with lower photon energies will typically be equipped with photon-counting silicon detectors for two-dimensional detection and silicon drift detectors for spectroscopy and higher-energy beamlines will use scintillators coupled to cameras or photomultiplier tubes. Longer-term developments include ‘high-Z’ semiconductors for detecting high-energy X-rays, photon-counting readout chips with smaller pixels and higher frame rates and pixellated avalanche photodiodes for time-resolved experiments.
The I13 beamline of Diamond Light Source encompasses two fully independent branches devoted for coherent imaging experiments (coherent X-ray diffraction and ptychography) and X-ray imaging and tomography (full-field microscopy and in-line phase contrast imaging). This contributed paper outlines the main features of the coherence beamline and a preliminary design of the experimental station for coherent X-ray diffraction imaging.
Circular dichroism spectroscopy is a useful and versatile tool to obtain low-resolution structural information about proteins, biopolymers and other chiral materials in solution. The first UV–VIS beamline dedicated to circular dichroism, B23, at Diamond Light Source Ltd., a third-generation synchrotron facility in the UK, has recently become operational and is now available for the user community. Herein we summarize the main characteristics of the beamline and some possible applications.
Thermal spraying is emerging as the leading route for the deposition of protective coatings onto engineering components to improve operation under extreme conditions of temperature, wear or corrosion. Detailed microstructural assessment is a key element in improving coating performance, and this study demonstrates the application of microfocus X-ray techniques to the determination of elemental and structural variations in the coatings.
Electroluminescent zinc sulfide doped with copper and chloride (ZnS:Cu, Cl) powder was heated to 400°C and rapidly quenched to room temperature. Comparison between the quenched and non-quenched phosphors using synchrotron radiation X-ray powder diffraction (XRPD) (λ = 0.828692 Å) and X-ray absorption spectroscopy (XAS) was made. XRPD shows that the expected highly faulted structure is observed with excellent resolution out to 150° 2θ (or to (12 2 2) of the sphalerite phase). The quenched sample compared to the unheated sample shows a large change in peak ratios between 46.7° and 46.9°, which is thought to correspond to the wurtzite (0 0 6), (0 3 2) and sphalerite (3 3 3)/(5 1 1) peaks. Hence, a large proportion of this sphalerite diffraction is lost from the material upon rapid quenching, but not when the material is allowed to cool slowly. The Zn K-edge XAS data indicate that the crystalline structures are indistinguishable using this technique, but do give an indication that the electronic structure has altered due to changing intensity of the white line. It is noted that the blue electroluminescence (EL) emission bands are lost upon quenching: however, a large amount of total EL emission intensity is also removed, which is consistent with our findings. We report the XRPD of a working alternating-current electroluminescence device in the synchrotron X-ray beam, which exhibits a new diffraction pattern when the device is powered in an AC field even though the phosphor is fixed in the binder. Significantly, only a few crystals are required to yield the diffraction data because of the high flux X-ray source. These in panel data show multiple sharp diffraction lines spread out under the region, where capillary data show broad diffraction intensity indicating that the phosphor powder is comprised of unique crystals, each having different structures.
One of the multiple capabilities of the new Joint Engineering, Environmental and Processing (JEEP) beamline I12 at Diamond Light Source is the set-up for polychromatic high-energy X-ray diffraction for the study of polycrystalline deformation and residual stresses. The results and interpretation of the first experiments carried out on JEEP are reported. Energy dispersive diffraction patterns from titanium alloy Ti-6Al-4V were collected using the new 23-cell ‘horseshoe’ detector and interpreted using Pawley refinement to determine the residual elastic strains at the macro- and meso-scale. It provides a clear demonstration of the tensile-compressive hardening asymmetry of the hexagonal close-packed grains oriented with the basal plane perpendicular to the loading direction.
The Bi-based oxide superconducting wire is one of the most promising materials for practical uses such as electric power transmission, electromagnets and so on. For the higher performances required in these applications, it is necessary to increase the critical current (Ic). We have carried out synchrotron radiation X-ray diffraction analysis to improve our manufacturing processes and thus to achieve higher Ic. We have performed in situ X-ray diffraction measurements during the sintering and cooling processes, and observed the decrease of Bi-2223(=(Bi,Pb)2Sr2Ca2Cu3Ox) phase during the cooling process. We have also evaluated the distribution of the crystal orientation in whole wire thickness, by measuring the rocking curves. We have observed that the distribution of the crystal orientation is improved by a refinement of the process conditions.
The limiting factor to the exploitation of the huge photon flux produced by a third-generation synchrotron light source is very often the detector. Experiments in material science often exploit X-ray diffraction. A fast and efficient detection of diffraction patterns enables dynamic experiments. Monolithic active pixel sensors (MAPS) can be exploited effectively to build fast and efficient detectors for X-ray diffraction. For its material science beam lines Diamond Light Source is developing and evaluating detectors based on commercial MAPS and MAPS developed for scientific applications. The various projects, target performance and some experimental results are reported in this paper.
We present an X-ray diffraction study of a semiconductor symmetric tilt grain boundary. The theory of crystal truncation rod scattering is extended to bicrystal interfaces and compared with experimental data measured at the Diamond Light Source.
A system is presented which combines photoelectron spectroscopy with complementary characterization techniques in order to provide in situ analysis of surfaces processes. The real-time capability of photoelectron spectroscopy has been enabled by an electron counting array detector that allows core and valence level spectra to be recorded in 1–10 s using a laboratory X-ray source and as low as 25 ms when coupled to synchrotron radiation source.
The efficient detection system is combined with a versatile heater stage, temperature and vacuum monitoring, and controllable evaporation sources in order to monitor chemical, structural and electronic changes in situ. The heated stage allows a range of programmed heating and cooling regimes to be applied to samples. Evaporation sources are provided for medium-temperature materials such as small organic molecules and high-temperature metals such as aluminium. The system has a linked vacuum vessel for plasma etching and Ar ion sputtering for surface preparation.
Micro-beam Laue diffraction is a well-established technique to determine lattice orientation and lattice structure. A polychromatic X-ray beam is used to illuminate a scattering volume within individual crystallites. The resulting diffraction pattern consists of a number of Laue spots. By refinement of the exact spot positions, lattice orientation and deviatoric elastic strain of the single crystalline scattering volume can be determined. Diffraction spot shape is linked to the orientation spread in the scattering volume arising due to the local dislocation structure. However, angular resolution of Laue diffraction spots is limited due to small sample-to-detector distance (~100 mm) and large Laue camera pixel size (~40 µm). In contrast, X-ray diffraction topography allows high-resolution imaging of an individual reflection from a crystal. On beamline B16 at the Diamond Light Source, we have combined micro-beam Laue diffraction with simultaneous collection of diffraction topographs, using a second high-resolution X-ray camera in the far field. In situ deformation of a single grain within a thin Ni foil has been studied using this setup. While detailed analysis is ongoing, some early results are presented here to allow an assessment of the technique's utility and future development possibilities.
We studied X-ray Fourier transform holography using separated holography-mask and sample geometry. The method was successfully applied to the imaging of the magnetic nanostructure using soft X-ray in addition to the cross-sectional imaging of Cu interconnect lines using hard X-ray.
Understanding the effects of thermal disorder on extended X-ray absorption fine structure increases the accuracy of results and allows one to gain original insights on local dynamical properties. Some recent advances are reviewed here.
The orbital ordering in perovskite-type vanadium oxides, RVO3 (R: rare earth), has been investigated by resonant X-ray scattering (RXS) near the V K-edge energy. The G-type orbital order, C-type orbital order and orbital disorder phases are elucidated on the basis of the azimuthal-angle and polarization dependence of the RXS signal reflecting the orbital ordering.
With modern undulators generating light of an arbitrary polarization state, experiments exploiting this feature in the soft X-ray region are becoming increasingly widespread. Circularly polarized light in the soft X-ray region is of particular interest to investigate of magnetic metals such as Fe, Co and Ni, and the rare earths. A versatile multilayer polarimeter has been designed and developed to characterize the polarization state of the soft X-ray beam. A W/B4C multilayer transmission phase retarder and reflection analyser has been used for polarimetry measurements on the beamline (I06) at Diamond Light Source. The design details of the polarimeter and preliminary polarimetry results are presented.
Understanding the physics of strongly correlated systems is one of the most challenging tasks of condensed matter research. Besides displaying extremely interesting physical behaviour, their sensitivity to small changes in external parameters makes them highly appealing for future technological applications. That sensitivity is attributed to the small value of the electron bandwidth W in comparison with other relevant energy scales such as the electron correlation U or the charge transfer (CT) energy gap Δ. While being a challenging experimental technique, the application of high pressure (HP) through a diamond anvil cell (DAC) permits to tune the bandwidth W continuously and without introducing impurities or disorder. Because of the small throughput of DACs, infrared (IR) measurements at HP take great advantage of the use of a high-brightness source as a synchrotron IR source (Lupi et al. 2007). We review here our latest results on several correlated insulators of the Mott–Hubbard and CT type.
The meta-foil is an all-metal self-supported electromagnetic metamaterial that features a space-grid that is locally stiff, yet globally flexible. Owing to its mechanical, thermal, chemical and radiative robustness, it lends itself to widespread applications.
Crystallinity of area-selective Ge layer with a (0 0 1) surface grown on Si substrate has been investigated by means of diffractometry using a parallel X-ray microbeam. The measured lattice parameters of 〈0 0 1〉 direction were about 0.17% smaller than that of bulk Ge crystal. This tensile strain value was almost the same as the simulated ones that used the finite-element method.
The new Core-XAS (X-ray absorption spectroscopy) beamline (B18) at Diamond aims to provide a reliable spectrometer for a broad scientific community. With this in mind, B18 has been built as a general-purpose beamline and offers to users a variety of sample environments and detection methods. Here we will present the first commissioning results and some of the capabilities of this versatile instrument.