[en] Here we present the in-situ monitoring by XANES/EXAFS (experiments carried out on the ROCK line at SOLEIL) of the reduction of Keggin-type [SiW_12-xMo_xO₄₀]^4- and Dawson-type [P₂W_18-xMo_xO₆₂]^6- POMs. By using chemometric tools to analyse the spectra collected at the K threshold for Mo and the L3 threshold for W, we will show that it is possible to obtain valuable information on the nature of the species formed during the reduction. These data, supported by complementary studies (multi-core NMR, UV-visible and single-crystal XRD), have enabled us to determine the distribution of electrons within super-reduced POMs. Finally, we will review our observations and attempt to shed light on the relationship between the structure/composition of POMs and their electron storage capacity

[en] Many in situ XAFS studies have shown that zinc incorporated in layered minerals is a major form of zinc in Zn-contaminated soils. Quantitative information on the local structural environment(s) and ordering of Zn in these minerals is required to better understand its behavior in soils. In this study, EXAFS spectroscopy was used to assess the structural environment of zinc incorporated at trace levels (40 ppm to 4,000 ppm) within the octahedral sheets of various natural and synthetic layered minerals. Results indicate that EXAFS data analyzed using ab initio FEFF calculations (FEFF 8.10) can unambiguously distinguish between zinc incorporation within the octahedral sheet of dioctahedral versus trioctahedral layered minerals and can determine the distribution (random or ordered) of zinc cations within the octahedral sheets of these minerals

[en] Iodate-substituted hydroxy-apatites are novel phases of potential interest for the immobilisation of radioactive iodine-129. However, the local environment of the iodine in these phases is still unclear. Here, a combined experimental-computational strategy has been used to investigate the mode of incorporation of iodates (IO_3"-) in Ca-hydroxyapatite and Sr-hydroxyapatite lattices. On one hand, I K and L3-edge XANES (X-ray Absorption Near Edge Structure) spectra are presented, showing that while the local structure around the iodate is similar in the two substituted hydroxyapatite lattices, it differs significantly from the one observed in a series of model compounds (NaIO_3, KIO_3, Ca(IO_3)_2.H_2O). I Kedge EXAFS (Extended X-ray Absorption Fine Structure) spectra were then analysed, revealing the lack of order around the iodate, and also the absence of local clustering of the iodates along the hydroxyl columns of the apatite. Further insight into the local environment of iodates in apatites was then obtained by DFT (Density Functional Theory) computational modeling of iodate-substituted Ca-hydroxyapatite lattices. (authors)

[en] This collective publication proposes a comprehensive synthesis on instruments, methodology, applications and works in which the interaction between X rays and condensed matter is implemented. This fourth release mainly focuses on the use the synchrotron radiation which is largely used by scientists to explore matter in new directions. After a presentation of X ray sources and of the issue of coherence, the chapters address some specific issues: small angle scattering of X rays, the EXAFS (Extended X-ray Absorption Fine Structure) as a local synchrotron technique, the state of art and evolution of X ray tomography in 2012, structural studies of complex ordered states in material science, studies of relationships between structures and properties in oxide ion based conducting materials, the possible explanation and prediction of recrystallisation from the characterization of the deformed state, and the applications of X rays to the study of metallic contaminants in the environment

[en] Basic oxygen furnace (BOF) steel slag is a residue from the basic oxygen converter in steel-making operations, and is partially reused as an aggregate for road constructions. Although BOF slag is an attractive building material, its long-term behaviour and the associated environmental impacts must be taken into account. Indeed BOF slag is mainly composed of calcium, silicon and iron but also contains trace amounts of potential toxic elements, specifically chromium and vanadium, which can be released. The present research focuses (i) on the release of Cr and V during leaching and (ii) on their speciation within the bearing phase. Indeed the mobility and toxicity of heavy metals strongly depend on their speciation. Leaching tests show that only low amounts of Cr, present at relatively high concentration in steel slag, are released while the release of V is significantly high. X-ray absorption near-edge structure (XANES) spectroscopy indicates that Cr is present in the less mobile and less toxic trivalent form and that its speciation does not evolve during leaching. On the contrary, V which is predominantly present in the 4+ oxidation state seems to become oxidized to the pentavalent form (the most toxic form) during leaching

[en] This document gathers the numerous contributions to a workshop which discussed scientific and societal challenges for academic, institutional and industrial actors of research for the development of new energy materials, and which strategic orientations to collectively define to face these challenges. A first session addressed stakes and needs for energy and for the environment (from fundamental research to industry for energy transition) and notably proposed contributions on fundamental research at the IFPEN (French Institute for Renewable Energies) in the field of materials for new energies, innovative materials and processes at the service of energy transition, insights on industrial building materials and ceramics to be developed by advanced characterization. The second session addressed materials and applications (assessment of the main classes of functional materials which may be used) with notably: accelerated discovery of materials at the service of durability in environment, present challenges for functional porous hybrid solids, materials for the electrochemical storage of energy (network RS2E), survey and prospective in the field of materials for catalysis, spectroscopies and microscopies for the study of reactive nanoparticles. The third session addressed the situation and perspectives of cutting-edge experimental methods and modelling approaches for functional materials: overview of material characterization, synchrotron-based X microscopy for the study of complex materials, to explore the world with advanced in-situ electronic microscopy, real-time and correlative electronic microscopy for the study of matter (birth, life and transformation of nano-materials), some perspectives in the experimental study of the colloidal transport in a complex porous environment, contribution of NMR of solid to the characterisation of functional materials, recent advances in hyper-polarised NMR and paramagnetic NMR of solid for the investigation of functional materials, contribution of NMR to the study of water transfers in fuel cells with proton exchanging membranes, recent advances in EPR spectroscopy for material characterization, situation and perspectives of vibrational spectroscopy for functional materials, theoretical chemistry at the service of the characterization of heterogeneous catalysts. A synthesis of the workshop is proposed