Can Yildirim

We present the design and operation of a low-cost 3D printed resin flow cell for the study of bio-cementation between two aligned particles in contact. The cell supports multimodal synchrotron X-ray characterization of the same interparticle contact, combining 3D X-ray diffraction modalities including scanning 3D X-ray diffraction, X-ray computed tomography and darkfield X-ray microscopy across multiple beamlines at the European Synchrotron Radiation Facility. Its geometry allows calcite crystals precipitated at the particle contact to be unambiguously distinguished from those nucleated on the cell walls during both indexing and crystal selection. The platform is demonstrated on glass beads and S30 sand grains cemented over successive cycles under varying NaCl concentrations, resolving the morphology and orientation of individual calcite crystals from the grain scale down to the intragranular scale. Practical limitations of the current design are also discussed.

Compound refractive lenses (CRLs) are a type of X-ray optics that find widespread applications as focusing and imaging lenses. The choice of material is one of the most defining properties of these lenses. In this work, we present a CRL made out of diamond. It provides an advantageous balance between refractivity and absorption, along with good manufacturability. Compared with Be CRLs, it features a higher optical density and thus enables application at higher photon energies without relying on large lens stacks or very small radii of curvature, which are challenging to manufacture. A diamond CRL is characterized for use as an objective for dark-field X-ray microscopy (DFXM) at the ID03 beamline of the European Synchrotron Radiation Facility and compared with Al and Be CRLs at 17 keV, 33 keV and 37 keV. Increasing the photon energy in DFXM from 17 keV up to 37 keV opens up the possibility to investigate new sample systems that were previously opaque to low-energy X-ray radiation. The capability of the diamond CRL at 33 keV is illustrated through DFXM measurements on two 0.5 mm-thick iron-based samples, which cannot be probed at 17 keV.

We introduce a crossed pair of multilayer Laue lenses (MLLs) as an objective for dark-field x-ray microscopy (DFXM). At the ID03 beamline at ESRF, two flat Mo/C/Si/C with a physical aperture of 50× 50 μm2 were operated confocally at 19.0 keV. The effective pupil was measured to be approximately 44× 43 μm2, corresponding to an effective numerical aperture of 1.58×10−3 at 19.0 keV. The 10% modulation-transfer-function crossings are 51.5(5) nm and 59.8(4) nm in the two image directions, while the angularly integrated analysis gives 55.6(3) nm—more than three times better than for a compound refractive lens (CRL) reference. The dark-field contrast is consistent with the bright-field response. At a sample-detector distance of 2.5 m, the x-ray magnification is 207. The efficiency of the MLL objective is 26.7%. We also characterize the instrumental reciprocal-space response for the three components of the diffraction vector. In normalized units, its rolling and longitudinal FWHMs are 0.0055(1) and 0.0062(1), respectively, and contain only weak secondary components. Finally, intensity and longitudinal-strain maps of a through-silicon-via structure show substantially improved spatial definition relative to CRL-based DFXM. This work expands the science domain of DFXM significantly, both for bulk and near-surface studies. The principal tradeoffs are a short working distance and broader reciprocal-space acceptance.

Laser Additive Manufacturing (LAM)-induced directional solidification creates complex microstructures in nickel-based superalloys, featuring columnar grains with cellular sub-grains and carbides. Using Scanning 3D X-ray Diffraction (S3DXRD), we reveal orientation and intergranular strain relationships coupled to cellular sub-grain networks and primary cubic MC carbides. We analyzed 3D orientation and elastic strain fields across 82 γ grains and 37,000+ carbides in an ABD-900AM alloy produced via Directed Energy Deposition (DED). Cooling-induced solute segregation creates volumetric lattice parameter patterning in the γ phase, altering residual stress fields. Ti-, Ta-, and Nb-rich carbides form preferentially in these high-solute regions, exhibiting weak orientation relationships with parent γ grains. These results provide the first non-destructive 3D study linking rapid solidification segregation, deformation heterogeneity, and carbide architectures in additively manufactured Ni-superalloys. These insights provide crucial detail to rationalise LAM process parameter optimisation and the coupled spatially governed structural performance.

Pink-beam dark-field X-ray microscopy (pDFXM) is a powerful emerging technique for time-resolved studies of microstructure and strain evolution in bulk crystalline materials. In this work, we systematically assess the performance of pDFXM relative to monochromatic DFXM when using a compound refractive lens as the objective. Analytical expressions for the spatial and angular resolution are derived and compared with numerical simulations based on geometrical optics and experimental data. The pink-beam configuration provides an increased diffraction intensity depending on the deformation state of the sample, accompanied by a general tenfold degradation in angular resolution along the rocking and axial strain (longitudinal) directions. This trade-off is disadvantageous for axial strain mapping but can be advantageous in cases where integrated intensities are needed. For a perfect crystal under parallel illumination with a pink beam, our results show that chromatic aberration is absent, whereas under condensed illumination it becomes significant. The aberration is shown to depend strongly on the local distortion of the crystal. Weak-beam imaging conditions, such as those required for resolving dislocations, are shown to remain feasible under pink-beam operation and may even provide an improved signal-to-noise ratio. The higher incident flux, enhanced by nearly two orders of magnitude, results in a ∼30× increase in diffracted intensity; beam heating effects are quantified and implications for optimized scanning protocols are discussed.

La structure et la dynamique des liquides et des verres chalcogénures sous pression: Les verres de chalcogénure sont ont une grande importance dans des applications optoélectroniques, mais aussi pour leur réseau covalent qui leur procure une "variabilité structurale" accrue. Ce projet étudie des alliages Ge-Se et utilise l'association d'analyses dynamique moléculaire (AIMD), de simulations et de diffusion des rayons X afin de déterminer la structure et la dynamique des phases liquide et vitreuse sous pression. Les alliages de Ge-Se permettent la "formation de verre" sur une large gamme de conditions, ce qui permet de contrôler la rigidité du réseau en augmentant le nombre moyen de coordination en fonction de la teneur en Ge ce qui affectera les propriétés macroscopiques du matériau, comme la résistance au vieillissement, la dureté, la conductivité et la fragilité. Dans cette optique, nous étudions 10 compositions générées/calculées par AIMD, et 5 autres compositions déterminées expérimentalement (i.e par trempe ) couvrant les domaines transitions élastiques souple-rigide suivant les critères de stabilité isostatique de Maxwell. Dans le cas de l'état liquide, la comparaison au préalable des données de la expérimentale permet de valider les modèles structuraux, pour ensuite examiner la dynamique des liquides de Ge-Se à pression ambiante. En partant du postulat que la mobilité atomique du système décroit en devenant plus rigide, l'étude des coefficients de diffusion et de la viscosité à 1050 K a montré des anomalies flagrantes...

Validating dislocation patterning models against in situ imaging experiments is a longstanding goal in materials physics. Here, we provide the first direct morphological comparison of such models. Using in situ Dark-Field Xray Microscopy (DFXM), we map the local orientations in high-purity aluminium deformed along [100] and find unexpected planar dislocation boundaries aligned with {111} slip planes that form prior to the development of a conventional dislocation cell structure. To explain this behaviour, we generate synthetic DFXM contrast images from a continuum dislocation dynamics (CDD) simulation. This mesoscale model, using nickel as a high stacking fault energy (SFE) FCC analogue, independently predicts the formation of the same {111} planar boundary types. This correspondence demonstrates that state-of-the-art CDD and DFXM experimental data can be used synergistically — despite differences in strain rates and length scales — as a practical route for refining continuum theories of plasticity.