Time-resolved X-ray diffraction study of SHS-produced NiAl and NiAl-ZrO2 composites

NiAl intermetallide and NiAl–ZrO 2 composites were prepared from pressed elemental powders by SHS in adynamic vacuum. The effect of diluent properties (such as conductivity and grain size) on the parameters of the SHS reaction has been investigated by time-resolved X-ray diffraction (TRXRD). By decreasing the reactivity of the green mixture, these nonreactive additives not only slow down the velocity of combustion front propagation but also give rise to local melting of the product. Synchrotron radiation was also used to elucidate the reaction mechanism. It has been found that the combustion synthesis of NiAl is triggered by aluminum melting and proceeds via the formation of two transient intermetallic phases, NiAl 3 and Ni 2 Al 3 . In the final product, only the NiAl phase has been detected

Tidal pumping in the upper Seine estuary as deciphered by plutonium isotope (238Pu and 239, 240Pu)

International audienc

ZnO Thin Films Synthesized by Sol-Gel Process for Photonic Applications

Undoped and aluminum-doped ZnO thin films are prepared by the sol-gel process. Zinc acetate dihydrate, ethanol and monoethanolamine are used as precursor, solvent and stabilizer, respectively. In the case of Al-doped ZnO, aluminum nitrate nonahydrate is added to the precursor solution with an atomic percentage equal to 1 or 2 at.% Al. The multi thin layers are prepared by spin-coating onto glass substrates, and are transformed into ZnO upon annealing at 550°C. Films with preferential orientation along the c-axis are successfully obtained. The structural, morphological, and optical properties of the thin films as a function of aluminum content have been investigated for different elaboration parameters (e.g. layer number) using X-ray diffraction, atomic force microscopy, scanning electronic microscopy. Waveguiding properties of the thin films have been also studied using m-lines spectroscopy. The results indicate that our films are monomodes at 632.8 nm with propagation optical loss estimated around 1.6 dB/cm

Experimental studies of the interactions between a hydrogen plasma and a carbon or tungsten wall

International audienceWe present work done at LSPM (Laboratory of Sciences of Processes and Material Sciences), using the CASIMIR ECR plasma reactor device, aimed at answering questions about hydrogen isotope fuel retention and dust production in the context of the plasma-facing components (PFCs) of the International Thermonuclear Experimental Reactor (ITER). The plasma is characterized by means of optical spectroscopy, mass spectrometry and electrostatic probe; furthermore the dust density and size distribution will be measured by a laser diagnostic system. We present some early results obtained from hydrogen plasma exposure of pure tungsten samples, as well as samples of ITER-relevant tungsten-rich powders, produced inhouse by the ball-milling technique, which are likely to be a by-product of material erosion and migration during tokamak operation. In particular, we have performed measurements of the specific surface area of these powders as a proxy to their capacity to absorb hydrogen

Tidal asymmetry: the use of artificial radionuclides in sediments (the Seine estuary, France)

The Seine estuary is the outlet of the catchment area of the Paris Basin, where fine sediments and a number of anthropogenic elements and substances end in. Among them, artificial radionuclides can be used as tracers of sediment sources and mixing processes. They may originate from upstream (atmospheric fallout from Chernobyl accident in 1986 and from nuclear weapons testing in the 1960s, licensed discharges from nuclear facilities...) or from downstream (La Hague reprocessing plant -Central Channel). In this macrotidal estuary, trapping and upstream migration of sediment is in process, due to the tide asymmetry; it is named "tidal pumping". It has been previously documented using 60Co, a short-lived radionuclide, originating from the La Hague reprocessing plant (north of Cotentin peninsula). The average upstream velocity of 60Co-labelled sediment particles has been estimated to be in the order of 10 km per year. The plutonium 239, 240 and the americium 241 have much longer decay period and could, therefore, give the opportunity to better understand the dynamics of the "tidal pumping" on a longer term

Tidal asymmetry: the use of artificial radionuclides in sediments (the Seine estuary, France)

The Seine estuary is the outlet of the catchment area of the Paris Basin, where fine sediments and a number of anthropogenic elements and substances end in. Among them, artificial radionuclides can be used as tracers of sediment sources and mixing processes. They may originate from upstream (atmospheric fallout from Chernobyl accident in 1986 and from nuclear weapons testing in the 1960s, licensed discharges from nuclear facilities...) or from downstream (La Hague reprocessing plant -Central Channel). In this macrotidal estuary, trapping and upstream migration of sediment is in process, due to the tide asymmetry; it is named "tidal pumping". It has been previously documented using 60Co, a short-lived radionuclide, originating from the La Hague reprocessing plant (north of Cotentin peninsula). The average upstream velocity of 60Co-labelled sediment particles has been estimated to be in the order of 10 km per year. The plutonium 239, 240 and the americium 241 have much longer decay period and could, therefore, give the opportunity to better understand the dynamics of the "tidal pumping" on a longer term

Evolution pluriannuelle du pompage tidal dans l’estuaire fluvial de la Seine par l’analyse de radionucléides artificiels dans des carottes sédimentaires.

National audienc

Evolution pluriannuelle du pompage tidal dans l’estuaire fluvial de la Seine par l’analyse de radionucléides artificiels dans des carottes sédimentaires.

National audienc