BEATS: BEAmline for synchrotron X-ray microTomography at SESAME.

The ID10 beamline of the SESAME (Synchrotron-light for Experimental Science and Applications in the Middle East) synchrotron light source in Jordan was inaugurated in June 2023 and is now open to scientific users. The beamline, which was designed and installed within the European Horizon 2020 project BEAmline for Tomography at SESAME (BEATS), provides full-field X-ray radiography and microtomography imaging with monochromatic or polychromatic X-rays up to photon energies of 100 keV. The photon source generated by a 2.9 T wavelength shifter with variable gap, and a double-multilayer monochromator system allow versatile application for experiments requiring either an X-ray beam with high intensity and flux, and/or a partially spatial coherent beam for phase-contrast applications. Sample manipulation and X-ray detection systems are designed to allow scanning samples with different size, weight and material, providing image voxel sizes from 13 µm down to 0.33 µm. A state-of-the-art computing infrastructure for data collection, three-dimensional (3D) image reconstruction and data analysis allows the visualization and exploration of results online within a few seconds from the completion of a scan. Insights from 3D X-ray imaging are key to the investigation of specimens from archaeology and cultural heritage, biology and health sciences, materials science and engineering, earth, environmental sciences and more. Microtomography scans and preliminary results obtained at the beamline demonstrate that the new beamline ID10-BEATS expands significantly the range of scientific applications that can be targeted at SESAME.

Emergence of the first XAFS/XRF beamline in the Middle East: providing studies of elements and their atomic/electronic structure in pluridisciplinary research fields.

XAFS/XRF is a general-purpose absorption spectroscopy beamline at the Synchrotron-light for Experimental Science and Applications in the Middle East (SESAME), Jordan. Herein, its optical layout is presented along with its powerful capabilities in collecting absorption and fluorescence spectra within a wide energy range (4.7-30 keV). The beamline is equipped with a conventional fixed-exit double-crystal monochromator that allows the collection of an X-ray absorption spectrum within a few minutes in step-by-step mode. An on-the-fly scanning mode will be implemented shortly where the acquisition time will be reduced to less than a minute per scan. The full automation of the beamline allows performing successive measurements under different conditions. The different experimental setups and special features available to users are reported. Examples of XRF and XAFS measurements are presented, showing the performance of the beamline under different standard conditions.

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste.

In this study the first in situ high-pressure single-crystal X-ray diffraction experiments at Xpress, the Indo-Italian beamline of the Elettra synchrotron, Trieste (Italy), are reported. A description of the beamline experimental setup and of the procedures for single-crystal centring, data collection and processing, using diamond anvil cells, are provided. High-pressure experiments on a synthetic crystal of clinoenstatite (MgSiO3), CaCO3 polymorphs and a natural sample of leucophoenicite [Mn7Si3O12(OH)2] validated the suitability of the beamline experimental setup to: (i) locate and characterize pressure-induced phase transitions; (ii) solve ab initio the crystal structure of high-pressure polymorphs; (iii) perform fine structural analyses at the atomic scale as a function of pressure; (iv) disclose complex symmetry and structural features undetected using conventional X-ray sources.

Effect of H2O on the Pressure-Induced Amorphization of Hydrated AlPO4-17.

The incorporation of guest species in zeolites has been found to strongly modify their mechanical behavior and their stability with respect to amorphization at high pressure (HP). Here we report the strong effect of H2O on the pressure-induced amorphization (PIA) in hydrated AlPO4-17. The material was investigated in-situ at HP by synchrotron X-ray powder diffraction in diamond anvil cells by using non- and penetrating pressure transmitting media (PTM), respectively, silicone oil and H2O. Surprisingly, in non-penetrating PTM, its structural response to pressure was similar to its anhydrous phase at lower pressures up to ~1.4 GPa, when the amorphization was observed to start. Compression of the structure of AlPO4-17 is reduced by an order of magnitude when the material is compressed in H2O, in which amorphization begins in a similar pressure range as in non-penetrating PTM. The complete and irreversible amorphization was observed at ~9.0 and ~18.7 GPa, respectively, in non- and penetrating PTM. The present results show that the insertion of guest species can be used to strongly modify the stability of microporous material with respect to PIA, by up to an order of magnitude.

High temperature structural study of Gd-doped ceria by synchrotron X-ray diffraction (673 K ≤ T ≤ 1073 K).

The crystallographic features of Gd-doped ceria were investigated at the operating temperature of solid oxides fuel cells, where these materials are used as solid electrolytes. (Ce(1-x)Gd(x))O(2-x/2) samples (x = 0.1, 0.3, 0.5, 0.7) were prepared by coprecipitation of mixed oxalates, treated at 1473 K in air, and analyzed by synchrotron X-ray diffraction in the temperature range 673 K ≤ T ≤ 1073 K at the Elettra synchrotron radiation facility located in Trieste, Italy. In the whole temperature span a boundary was found at x ∼ 0.2 between a CeO2-based solid solution (for x ≤ 0.2) and a structure where Gd2O3 microdomains grow within the CeO2 matrix, taking advantage of the similarity between Gd(3+) and Ce(4+) sizes; the existence of the boundary at x ∼ 0.2 was confirmed also by measurements of ionic conductivity performed by impedance spectroscopy. Similar to what observed at room temperature, the trend of the cell parameter shows the presence of a maximum; with increasing temperature, the composition corresponding to the maximum moves toward lower Gd content. This evidence can be explained by analyzing the behavior of the coefficient of thermal expansion as a function of composition.

Tuning the growth mode of nanowires via the interaction among seeds, substrates and beam fluxes.

The growth mechanism of semiconductor nanowires is still an argument of high interest, and it is becoming clearer, investigation after investigation, that simple pictures fail to describe the complex behaviors observed under different growth conditions. We report here on the growth of semiconductor nanowires, maintaining control over the chemical composition and the physical state of the metallic seeds, and tuning the growth mechanism by varying the growth conditions. We focused on Au-assisted ZnSe nanowires grown by molecular beam epitaxy on GaAs(111)B substrates. We show that at sufficiently high temperatures, the Au seed is strongly affected by the interaction with the substrate and that nanowire growth can occur through two different mechanisms, which have a strong impact on the nanowire's morphology and crystal quality. In particular, ZnSe NWs may exhibit either a uniformly oriented, straight morphology when the nanoparticle seed is liquid, or a kinked, worm-like shape when the nanoparticle seed is switched to a solid phase. This switch, which tunes the nanowire growth mechanism, is achieved by controlling the Zn-to-Se beam pressure ratio at the Au-seed surface. Our results allow a deeper understanding of particle-assisted nanowire growth, and an accurate control of nanowire morphology via the control of the growth mechanism.

In situ reaction furnace for real-time XRD studies.

The new furnace at the Materials Characterization by X-ray Diffraction beamline at Elettra has been designed for powder diffraction measurements at high temperature (up to 1373 K at the present state). Around the measurement region the geometry of the radiative heating element assures a negligible temperature gradient along the capillary and can accommodate either powder samples in capillary or small flat samples. A double capillary holder allows flow-through of gas in the inner sample capillary while the outer one serves as the reaction chamber. The furnace is coupled to a translating curved imaging-plate detector, allowing the collection of diffraction patterns up to 2θ ≃ 130°.