The high levels of flux available at a fourth-generation synchrotron are shown to have significant beam heating effects for high-energy X-rays and radiation hard samples, leading to temperature increases of over 400 K with a monochromatic beam. These effects have been investigated at the ID11 beamline at the recently upgraded ESRF Extremely Brilliant Source, using thermal lattice expansion to perform in situ measurements of beam heating. Results showed significant increases in temperature for metal and ceria samples, which are compared with a lumped thermodynamic model, providing a tool for estimating beam heating effects. These temperature increases may have a drastic effect on samples and measurements, such as the rapid recrystallization of a copper wire shown here. These results demonstrate the importance of beam heating and provide information needed to consider, predict and mitigate these effects.

Charge ordering creates a spontaneous array of differently charged ions and is associated with electronic phenomena such as superconductivity, colossal magnetoresistances (CMR), and multiferroicity. Charge orders are usually suppressed by chemical doping and site selective doping of a charge ordered array has not previously been demonstrated. Here we show that selective oxidation of one out of eight distinct Fe 2+ sites occurs within the complex Fe 2+ /Fe 3+ ordered structure of 2%-doped magnetite (Fe 3 O 4 ), while the rest of the charge and orbitally ordered network remains intact. This ‘charge order within a charge order’ is attributed to the relative instability of the trimeron distortion surrounding the selected site. Our discovery suggests that similar complex charge ordered arrays could be used to provide surface sites for selective redox reactions, or for storing information by doping specific sites.

To understand why heterogeneity leads to improved ductility in bulk metallic glasses (BMGs), we derived the local elastic moduli and energy barriers for the activation of shear transformation zones (STZs) in homogeneous and heterogeneous BMGs using high-energy x-ray diffraction. In contrast to the homogeneous glass, STZ activation dynamics in the heterogeneous BMG are spatially nonuniform and the activation of STZs with low energy barriers is favored. Using qualitative arguments, we propose that there is an alternative deformation pathway involving multiple shear bands, which makes the material plastically deformable.

This work discusses an experimental technique for studying the mechanics of three-dimensional (3D) granular solids. The approach combines 3D X-ray diffraction and X-ray computed tomography to measure grain-resolved strains, kinematics and contact fabric in the bulk of a granular solid, from which continuum strains, grain stresses, interparticle forces and coarse-grained elasto-plastic moduli can be determined. We demonstrate the experimental approach and analysis of selected results on a sample of 1099 stiff, frictional grains undergoing multiple uniaxial compression cycles. We investigate the inter-particle force network, elasto-plastic moduli and associated length scales, reversibility of mechanical responses during cyclic loading, the statistics of microscopic responses and microstructure–property relationships. This work serves to highlight both the fundamental insight into granular mechanics that is furnished by combined X-ray measurements and describes future directions in the field of granular materials that can be pursued with such approaches.

Short term sub-glass transition annealing controls the structural reordering and nanocrystallization of CuZr−based bulk metallic glasses (BMGs). Using this method, 5 times higher resistance against strain softening as confirmed by three-point bending tests is attained. Homogenously dispersed nanoparticles in sizes of 20–50nm accounts for the remarkable shifts and peak formations on reciprocal space together with the diffraction spots observed on 2D diffraction pattern. Real-space pair distribution function analysis reveals noticeable changes in peak shapes and positions correlated with the changes in short- to medium-range ordering. The differences in the partial nearest neighbor numbers upon annealing mark the dominant Zr−Zr pair to diminish whereas the Cu−Cu pair becomes prominent, hinting that Cu diffusion is mainly responsible for structural reordering and formation of new phases. The pursued study using hard X-ray synchrotron radiation reveals important aspects of structural changes preceding nanocrystallization, which in turn enhances the mechanical performance in BMGs.

The stress-induced martensitic transformation in tensioned nickel-titanium shape-memory alloys proceeds by propagation of macroscopic fronts of localized deformation. We used three-dimensional synchrotron x-ray diffraction to image at micrometer-scale resolution the grain-resolved elastic strains and stresses in austenite around one such front in a prestrained nickel-titanium wire. We found that the local stresses in austenite grains are modified ahead of the nose cone-shaped buried interface where the martensitic transformation begins. Elevated shear stresses at the cone interface explain why the martensitic transformation proceeds in a localized manner. We established the crossover from stresses in individual grains to a continuum macroscopic internal stress field in the wire and rationalized the experimentally observed internal stress field and the topology of the macroscopic front by means of finite element simulations of the localized deformation.

This study focuses on the effects of the organic ligand 4-ethylresorcinol on the crystal structure of human insulin using powder X-ray crystallography. For this purpose, systematic crystallization experiments have been conducted in the presence of the organic ligand and zinc ions within the pH range 4.50–8.20, while observing crystallization behaviour around the isoelectric point of insulin. High-throughput crystal screening was performed using a laboratory X-ray diffraction system. The most representative samples were selected for synchrotron X-ray diffraction measurements, which took place at the European Synchrotron Radiation Facility (ESRF) and the Swiss Light Source (SLS). Four different crystalline polymorphs have been identified. Among these, two new phases with monoclinic symmetry have been found, which are targets for the future development of microcrystalline insulin drugs.

Angle-dispersive X-ray diffraction and microfluorescence together with precession electron diffraction (PED) and scanning electron microscopy measurements on iron nitride prepared at 15 GPa and 1800 K from iron and sodium azide starting materials reveal synthesis of both hexagonal P6(3)22 and trigonal P312 Fe3N1+x modifications (a = 4.745 (1) angstrom, c = 4.403 (1) angstrom, Z = 2). Nitrogen access to vacant interstitial sites, repulsions between nitrogen ions and metal nitride thermal stability are the factors relating iron nitride-phase relations to those of other early (Hf, Zr, Ti)-N and late (Ni-N) transition metal nitrides subjected to similar pressure and temperature conditions. Here, Fe3N1+x can accommodate pressure and x variability by situating nitrogen in a broader range of interstitial crystallographic sites in the intimately related hexagonal and trigonal crystal structures.

The primary focus of the present work is the study of the effects that two ligands and the crystallization pH have on the crystalline forms of human insulin. For this purpose, human insulin (HI) was co-crystallized with two distinct phenolic derivatives: the organic ligands meta-cresol (m-cresol) and 4-nitrophenol. The formation of polycrystalline precipitates was then followed by means of structural characterization of the individual specimens in terms of unit-cell symmetry and parameters. In both cases, two different polymorphs were identified via X-ray powder diffraction measurements, the first of hexagonal symmetry (R3 space group) at higher pH values and the second of monoclinic symmetry (space group P21) with unit-cell parameters a = 87.4282 (5), b = 70.5020 (3), c = 48.3180 (4) Å, β = 106.8958 (4)°, the latter of which to our knowledge has never been observed before.

A powerful insight into the structural and interfacial properties of post-fabricated bulk heterojunction (BHJ) organic photovoltaic (OPV) devices, utilizing partially reduced graphene oxide as the hole transport layer, is reported.

The stability of individual metastable austenite grains in low-alloyed TRIP steels has been studied during tensile loading using high-energy X-ray diffraction. The carbon concentration, grain volume and grain orientation with respect to the loading direction was monitored for a large number of individual grains in the bulk microstructure. Most austenite grains transform into martensite in a single transformation step once a critical load is reached. The orientation-dependent stability of austenite grains was found to depend on their Schmid factor with respect to the loading direction. Under the applied tensile stress the average Schmid factor decreased from an initial value of 0.44 to 0.41 at 243MPa. The present study reveals the complex interplay of microstructural parameters on the mechanical stability of individual austenite grains, where the largest grains with the lowest carbon content tend to transform first. Under the applied tensile stress the average carbon concentration of the austenite grains increased from an initial value of 0.90 to 1.00 wt% C at 243MPa, while the average grain volume of the austenite grains decreased from an initial value of 19 to 15 µm3 at 243MPa.

A novel high spatial resolution synchrotron X-ray diffraction stratigraphy technique has been applied in-situ to an integrated plasmonic nanoparticle-based organic photovoltaic device. This original approach allows for the disclosure of structure-property relations linking large scale organic devices to length scales of local nano/hetero structures and interfaces between the different components.

High energy synchrotron XRD was employed to determine the lattice strain epsilon{111} and diffraction peak intensity ratio R{200} in tetragonal PZT ceramics, both in the virgin poled state and after a bipolar fatigue experiment. It was shown that the occurrence of microstructural damage during fatigue was accompanied by a reduction in the gradient of the epsilon{111}-cos(2) psi plot, indicating a reduction in the level of residual stress due to poling. In contrast, the fraction of oriented 90 degrees ferroelectric domains, quantified in terms of R{200}, was not affected significantly by fatigue. The change in residual stress due to fatigue is interpreted in terms of a change in the average elastic stiffness of the polycrystalline matrix due to the presence of inter-granular microcracks. (C) 2013 AIP Publishing LLC.

The martensitic transformation behavior of the meta-stable austenite phase in low alloyed TRIP steels has been studied in situ using high-energy X-ray diffraction during deformation. The stability of austenite has been studied at different length scales during tensile tests and at variable temperatures down to 153 K. A powder diffraction analysis has been performed to correlate the macroscopic behavior of the material to the observed changes in the volume fraction of the phases. Our results show that at lower temperatures the deformation induced austenite transformation is significantly enhanced and extends over a wider deformation range, resulting in a higher elongation at fracture. To monitor the austenite behavior at the level of an individual grain a high-resolution far-field detector was used. Sub-grains have been observed in austenite prior to transformation.

Electronic structure calculations of the Verwey ground state of magnetite, Fe3O4, using density functional theory with treatment of on-site Coulomb interactions (DFT + U scheme), are reported. These calculations use the recently published experimental crystal structure coordinates for magnetite in the monoclinic space group Cc. The computed density distribution for minority spin electron states close to the Fermi level demonstrates that charge order and Fe2+-orbital order are present at the B-type lattice sites to a first approximation. However, Fe2+/Fe3+ charge differences are diminished through weak bonding interactions of the Fe2+ states to specific pairs of neighboring iron sites that create linear, three-B-atom trimeron units that may be regarded as orbital molecules. Trimerons are ordered evenly along most Fe atom chains in the Verwey structure, but more complex interactions are observed within one chain.

The presence of residual stresses in multicrystalline silicon solar cells has become a problem of growing importance, especially in view of silicon wafer thickness reduction. Without increasing the wafer strength, this leads to a high fracture rate during subsequent handling and processing steps. The most critical processing step during the manufacture of screen-printed solar cells is the firing of metallic contacts. In this work we evaluate the development of mechanical stresses in metallic contacts (Al, Ag and Al/Ag bus bars) with respect to different processing steps. For this purpose we combine X-ray diffraction (XRD) stress measurements, Synchrotron measurements, cell bowing measurements with a laser scanning device and in-situ bending tests. Synchrotron diffraction analysis showed that there is a stress gradient in both Ag and Al layers. It was found that the Al back contact layer represents a very porous/loose microstructure, which does not affect the mechanical stability of the solar cell. It was also found that the thickness and composition of the eutectic layer are the most important factors influencing the bowing of a complete solar cell. Furthermore, residual stresses and stresses developing during cell bending in Ag, Al/Ag bus bars are measured and discussed in detail in this work.

Synchrotron pole figures have been recorded from the Nd2Fe14B, Nd2O3, and NdO grains in commercial Dy-free, Nd-Fe-B sintered magnets in the as-sintered and fully annealed states. In contrast to the well known <00l> fiber texture in the Nd2Fe14B grains, the Nd-oxide phases showed no preferred orientation in the as-sintered or annealed states. The random orientation of the Nd-oxide grains was confirmed from histograms of the pole density values. These showed only small deviations from the pole density of a non-textured material.

We have studied the micromechanical behaviour of two low-alloyed multiphase TRIP steels with different aluminium contents by performing in situ high-energy X-ray diffraction experiments at a synchrotron source under increasing tensile stress levels. A detailed analysis of the two-dimensional diffraction data has allowed us to unravel the interplay between the martensite formation, the texture evolution and the load partitioning, and to correlate the observed behaviour to the macroscopic response of the material. The high aluminium content TRIP steel grade presents a higher volume fraction of retained austenite at room temperature that transforms more gradually into martensite under deformation, providing a larger uniform elongation. The comparison between the observed transformation behaviour and the texture evolution indicates that the < 1 0 0 > component along the loading direction corresponds to a low critical stress for the transformation. The evolution of the elastic strains revealed the occurrence of a significant load partitioning before reaching the macroscopic yield strength, which becomes more pronounced in the plastic regime due to the progressive yielding of the different grains in the polycrystalline material. This opens the door to tailor the austenite stability by altering the distribution in grain size, local carbon content, and grain orientation in order to produce the optimal load partitioning and work hardening for improved combinations of strength and formability in low-alloyed TRIP steels. (C) 2011 Elsevier B.V. All rights reserved.

Two synchrotron diffraction techniques, three-dimensional X-ray diffraction and Laue microdiffraction, are applied to studying the deformation behaviour of individual grains embedded in a Cu74Al23Be3 superelastic shape memory alloy. The average lattice rotation and the intragranular heterogeneity of orientations are measured during in situ tensile tests at room temperature for four grains of mean size similar to 1 mm. During mechanical loading, all four grains rotate and the mean rotation angle increases with austenite deformation. As the martensitic transformation occurs, the rotation becomes more pronounced, and the grain orientation splits into several sub-domains: the austenite orientation varies on both sides of the martensite variant. The mean disorientation is similar to 1 degrees. Upon unloading, the sub-domains collapse and reverse rotation is observed. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The stability of the retained austenite has been studied in situ in low-alloyed transformation-induced-plasticity (TRIP) steels using high-energy X-ray diffraction during tensile tests at variable temperatures down to 153K. A detailed powder diffraction analysis has been performed to probe the austenite-to-martensite transformation by characterizing the evolution of the phase fraction, load partitioning and texture of the constituent phases simultaneously. Our results show that at lower temperatures the mechanically induced austenite transformation is significantly enhanced and extends over a wider deformation range, resulting in a higher elongation at fracture. Low carbon content grains transform first, leading to an initial increase in average carbon concentration of the remaining austenite. Later the carbon content saturates while the austenite still continues to transform. In the elastic regime the probed {hkl} planes develop different strains reflecting the elastic anisotropy of the constituent phases. The observed texture evolution indicates that the austenite grains oriented with the {200} plane along the loading direction are transformed preferentially as they show the highest resolved shear stress. For increasing degrees of plastic deformation the combined preferential transformation and grain rotation results in the standard deformation texture for austenite with the {111} component along the loading direction. The mechanical stability of retained austenite in TRIP steel is found to be a complex interplay between carbon concentration in the austenite, grain orientation, load partitioning and temperature.