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Abstract In search to identify extremely stable materials to perform the collimation function of the 7-TeV proton beam halo at the Large Hadron Collider (LHC), oxide dispersion strengthened (DS) copper alloys were explored. These internally oxidized copper alloys known as GlidCop are also leading candidates for high heat flux applications in fusion reactors and as divertor and first wall structure in ITER. These considerations have led to an extensive body of research on neutron-induced changes in the microstructure and physio-mechanical properties. This study focused primarily on the damage induced by 200 MeV protons on as wrought and cold-worked GlidCop Al15 DS copper ally selected as a candidate material of the LHC beam collimation structure to damage levels up to ∼10 displacements-per-atom (dpa) and irradiation temperatures up to ∼600 °C. For reference, low dose spallation neutron damage at sub-zero irradiation temperature was included in the study. Proton irradiation effects on dimensional stability, mechanical behavior, electrical resistivity and X-ray diffraction-based microstructural changes are presented in the paper. GlidCop Al15 exhibited excellent thermal stability and superior to pure Cu resistance to conductivity loss. Proton irradiation-induced hardening and embrittlement at distinct irradiation temperature regimes were shown to follow similar trends to what was reported under neutron exposure to even higher dpa damage. At T irr ∼600 ± 20 °C the cold-worked DS copper alloy exhibited softening accompanied by elongation reduction while at T irr ∼200 ± 10 °C the as-wrought experienced hardening with elongation increase. High resolution X-ray diffraction revealed that even low-dose neutron irradiation has a strong influence on the size and distribution of dispersed Al 2 O 3 particles. [ABSTRACT FROM AUTHOR]

The microstructural response of neutron irradiated 3C-SiC have been investigated over a wide irradiation temperature and fluence range via qualitative and quantitative synchrotron-based X-ray diffraction characterization. We identify several neutron fluence- and irradiation temperature-dependent changes in the microstructure, and directly highlight the specific defects introduced through the course of irradiation. By quantifying the microstructure, we aim to develop a more detailed understanding of the radiation response of SiC. Such studies are important to build mechanistic models of material performance and to understand the susceptibility of various microstructures to radiation damage for advanced energy applications. [ABSTRACT FROM AUTHOR]

The microstructural response of neutron irradiated 3C-SiC have been investigated over a wide irradiation temperature and fluence range via qualitative and quantitative synchrotron-based X-ray diffraction characterization. We identify several neutron fluence- and irradiation temperature-dependent changes in the microstructure, and directly highlight the specific defects introduced through the course of irradiation. By quantifying the microstructure, we aim to develop a more detailed understanding of the radiation response of SiC. Such studies are important to build mechanistic models of material performance and to understand the susceptibility of various microstructures to radiation damage for advanced energy applications. [ABSTRACT FROM AUTHOR]

The study revealed that loss of ductility in an amorphous Fe-alloy coating on a steel substrate composite structure was essentially prevented from occurring, following radiation with modest neutron doses of ∼2 × 10 18 n/cm 2 . At the higher neutron dose of ∼2 × 10 19 , macroscopic stress-strain analysis showed that the amorphous Fe-alloy nanostructured coating, while still amorphous, experienced radiation-induced embrittlement, no longer offering protection against ductility loss in the coating-substrate composite structure. Neutron irradiation in a corrosive environment revealed exemplary oxidation/corrosion resistance of the amorphous Fe-alloy coating, which is attributed to the formation of the Fe 2 B phase in the coating. To establish the impact of elevated temperatures on the amorphous-to-crystalline transition in the amorphous Fe-alloy, electron microscopy was carried out which confirmed the radiation-induced suppression of crystallization in the amorphous Fe-alloy nanostructured coating. [ABSTRACT FROM AUTHOR]

Massive, thick-walled pressure vessels are permanent nuclear reactor structures that are exposed to a damaging flux of neutrons from the adjacent core. The neutrons cause embrittlement of the vessel steel that grows with dose (fluence), as manifested by an increasing ductile-to-brittle fracture transition temperature. Extending reactor life requires demonstrating that large safety margins against brittle fracture are maintained at the higher neutron fluence associated with beyond 60 years of service. Here synchrotron-based x-ray diffraction and small angle x-ray scattering measurements are used to characterize highly embrittling nm-scale Mn–Ni–Si precipitates that develop in the irradiated steels at high fluence. These precipitates lead to severe embrittlement that is not accounted for in current regulatory models. Application of the complementary techniques has, for the very first time, successfully identified the crystal structures of the nanoprecipitates, while also yielding self-consistent compositions, volume fractions and size distributions. [ABSTRACT FROM AUTHOR]

Abstract: Corrosions that are associated to the presence of chloride-containing phases are one of the main causes of the decay of metallic materials of historic value. In order to improve the currently used desalination treatments, the processes occurring have to be understood. The purpose of the present study is based on the preparation and desalination of pure akaganeite β-FeOOH powder, which is one of the main chloride-containing compounds present in the corrosion layers of ancient iron objects. The combination of X-ray Absorption Spectroscopy (XAS) and X-ray Diffraction (XRD) is a powerful tool, which revealed a correlation between the chloride content and the β-FeOOH structural parameters. We show that akaganeite contains different forms of chloride. These latter could be trapped inside the crystalline structure or adsorbed at the surface of the compound. In addition, we prove that dechlorination treatments, even in pure water, can easily remove the adsorbed chloride, while the chloride located within the channels of the β-FeOOH structure is also extracted but with less efficiency. Such structural evidence for the desalination process of akaganeite provides fundamental results for the treatment optimisation used in the context of the preservation of iron archaeological artefacts. [Copyright &y& Elsevier]

Depending on the experimental conditions, the CO disproportionation reaction over well-calibrated Co/Al2O3 catalysts leads to the formation of carbon with two distinct morphologies: carbon nanotubes (with cylindrical carbon layers parallel to the tube axis) and carbon filaments (constituted of carbon layers with a truncated cone shape). The structural differences between these two morphologies were investigated by X-ray diffraction using synchrotron X-ray radiation. In situ X-ray diffraction analyses performed during the carbon growth at 600 °C show that the (002) inter-layer spacing is larger by a few percents in carbon nanotubes than in carbon filaments. d(002) is, respectively, equal to 0.3486 and 0.3469 nm for the nanotubes and filaments. The variation of d(002) with the graphene layer stacking geometry was confirmed by additional measurements performed at room temperature on samples prepared ex situ. The evolution of the cobalt catalyst during the carbon growth was also investigated. The results of this study indicate that the catalyst deactivation is not the result of a bulk transformation of the cobalt particles. [Copyright &y& Elsevier]

Abstract: We present the temperature phase diagram of the compound DyFe4Ge2 determined from high-quality powder XRPD for the entire magnetically ordered regime. DyFe4Ge2 undergoes at , a simultaneous structural and magnetic transition of second-order P42/mnm, , , followed by two subsequent isostructural first-order magnetic transitions at and . The structural transition at , is characterised by strong changes of the ratio and of the shear strain while the transition is related to a lattice expansion along on cooling. Minor Fe parameter shifts and deformations (torsion angle and out-of plane Fe–Fe distances) of the Fe tetrahedra were found to accompany the two magnetic transitions. Using the XRPD instrumental resolution and modelling the anisotropic micro-strain enabled us to refine the observed anisotropic peak broadening associated with the presence of micro-structure effects. The maximum strain experienced by the crystal lattice during a sequence of subtle magnetic transitions was observed in the intermediate temperature interval of incommensurate magnetic phases. [Copyright &y& Elsevier]

High-quality powder XRD data collected on the ESRF beam line BM16, are presented for the entire magnetically ordered regime (TN=50 K) of the compound HoFe4Ge2. The data analysis reveals the occurrence of a re-entrant structural transition. The first symmetry breaking transition is of second order and occurs at the magnetic transition while the second transition occurs at lower temperatures at 15 K and is of first order: P42/mnm (Tc,TN=50 K)→Cmmm (TIC=15 K)→P42/mnm. The phase diagram comprises three temperature regions: (a) the high temperature range with T>TN for the tetragonal P42/mnm phase; (b) the intermediate temperature range, 15 K<T, with exclusively the orthorhombic phase Cmmm (c) the low temperature range, 4.2–15 K, where the Cmmm and P42/mnm phases coexist in strongly variable proportions. The P42/mnm phase reaches 73.6% at 4.2 K. This phenomenon is most likely due to competing magneto-elastic mechanisms involving the Ho crystal field anisotropy, the Ho–Ho, Ho–Fe and the Fe–Fe exchange interactions and their coupling with the lattice strains. The anisotropic peak broadening associated with the presence of microstructure effects has been refined by using the instrumental resolution and modeling the anisotropic strain. [Copyright &y& Elsevier]