[en] Recent electron spectroscopic work to determine the electronic bandstructure of intermetallic hydrides is reviewed. Due to experimental constraints (e.g. there are no single crystals available) information obtained up to now is limited to density of states like features. We discuss the trends in the spectra of Zr-(3d-tm) hydrides as well as newer results on YFe₂H_x and amorphous Zr-Ni hydrides. The difficulty of extracting quantitative results from these data is demonstrated. (author) 14 refs., 4 figs

[en] During the last two years at Stanford we have developed parallel beam geometries for powder diffraction. The instrumentation includes a silicon channel cut monochromator, horizontal parallel slits to define the diffracted beam and vertical parallel slits to limit axial divergence. Two identical automated vertical scanning diffractometers were used, one for the monochromator and the other for the powder specimens. Patterns can be obtained both in the energy dispersive mode by scanning the monochromator and in the standard 2θ:θ mode by scanning the powder diffractometer. The instrumental profile is essentially independent of scattering angle and specimen absorption, perfectly symmetric and the resolution can be chosen at will. A variety of experiments demonstrating these claims and utilizing anomalous dispersion is described. The set-up has many advantages in, for example, studies of preferred orientation, absolute measurements of lattice parameter and in structural refinement. (author) 9 refs., 6 figs

[en] Recent advances in both computational methods and instrumentation have brought powder diffraction techniques to the point where it is now possible to determine crystal structures ab initio. The methods that have been used will be discussed and a number of applications based upon constant wavelength and time-of-flight neutron diffraction, and synchrotron X-ray diffraction, will be described. (author) 35 refs., 4 figs., 2 tabs

[en] A coating of oxide particles of certain reactive elements applied to a metallic substrate may improve the nucleation, growth and spallation characteristics of its oxide scale, providing this is formed primarily by outward cation movement. The mechanisms for these effects are reviewed, and their significance for the selection of coating conditions to give optimum performance is discussed. Oxide particle size and spacing, and the concentration of reactive element segregation, have been shown to be controlling parameters in the effect of reactive elements on grain boundary diffusion. (author) 55 refs., 6 figs., 3 tabs

[en] To improve the efficiency of components operating at high temperatures, many efforts are deployed to develop new materials. Oxide Dispersion Strengthened (ODS) materials could be used for heat exchangers or cladding tubes for the new GENIV nuclear reactors. This type of materials are composed with a metallic matrix (usually iron base alloy for nuclear applications or nickel base alloy for heat exchangers) reinforced by a distribution of nano-oxides. They are obtained by powder metallurgy and mechanical alloying. The creep resistance of these materials is excellent, and they usually exhibit a high tensile strength at room temperature. Depending on the cold working and/or the heat treatments, several types of microstructure can be obtained: recrystallised, stress relieved. One of the key challenges is to transform ODS materials into thin tubes (up to 500 microns thick) within a robust fabrication route while keeping the excellent mechanical properties. To prevent cracking during the process or to obtain a final product with low residual stresses, it is important to quantify the effect of the heat treatments on the release of internal stresses. The aim of this study is to show how residual stresses can be determined on different thin tubes using two complementary approaches: (i) macroscopic stresses determination in the tube using beam theory (small cuts along the longitudinal and circumferential directions and measurements of the deflection), (ii) stress determination from x-ray diffraction analyses (surface analyses, using 'sin"2ψ' method with different hypothesis). Depending on the material and the heat treatment, residual stresses vary dramatically and can reach 800 MPa which is not far from the yield stress; comparisons between both methods are performed and suggestions are given in order to optimize the thermo-mechanical treatment of thin ODS tubes. (authors)

[en] ODS steels (Oxide Dispersion Strengthened) are candidate materials for fuel cladding in Sodium Fast Reactors (SFR). These materials have good mechanical properties at high temperature due to a dispersion of nano-meter-sized oxides into the matrix. Previous studies have shown that melting can induce a decrease of the mechanical properties at high temperatures due to modifications of the nano-meter-sized oxide dispersion. Therefore the fusion welding techniques are not recommended and the solid state bounding has to be evaluated. This study is focused on resistance upset welding. Welding experiments and numerical simulations are coupled. The numerical simulation is developed in order to have a better understanding of the thermal and the mechanical phenomena occurring during the welding process. The simulation shows that the welding steps can be divided in two stages. First, the temperature of the contact between pieces increases. Second, the heat generation is mainly located in the cladding leading to the collapse and forging the pieces. The microstructural observations confirm that the major deformation is located in the cladding. Oxide dispersion modification and dynamical recrystallisation has been found for welds achieved with a non optimized process parameter set. The deformation and the temperature seem to be of prime importance in the modification of the oxide dispersion. (authors)

[en] X-ray diffraction is used in combination with tensile testing for measuring elastic properties of metallic thin films. Size effect, elastic anisotropy and grain morphologies are considered in all these experiments and supported by different kind of numerical simulations operating at different length scales. Such instrumental studies are time consuming even if synchrotron sources are used. New experiments are under progress for reducing acquisition data and improving precision on strain measurements. After introducing briefly the main principles and results of our techniques, first promising measurements on nano-metric W/Cu multilayers using 2D CCD detectors and high monochromatic flux at the Advanced Light Source Berkeley (USA) on beam line 11.3.1 are presented. In addition, simulation experiments for analyzing elasticity in textured gold film are discussed. (authors)

[en] In vitro studies have demonstrated that fullerenol, a polyhydroxylated derivative of fullerene (C₆₀(OH)_n n = 12-26), has a high antioxidative potential. Since any radiation injury is mainly a consequence of the action of free radical species, the aim of this study was to examine radioprotective efficiency of fullerenol in whole-body irradiated mice. The experiment was performed on male, adult, white mice, whole-body irradiated with X-rays doses of 6 to 8 Gy (X-ray energy of 8 MV). Fullerenol C₆₀(OH)₂₄ was given in doses of 10 and 100 mg/kg i.p. 30 minutes before irradiation. The experimental groups consisted of 25-30 animals each. The survival rate and body mass gain of irradiated animals were monitored for 30 days after irradiation. The mean lethal times (LT₅₀) of irradiated mice and mean lethal dose of X-rays were calculated and compared. The results showed that fullerenol C₆₀(OH)₂₄, in a dose of 100 mg/kg i.p., prolonged LT₅₀ of irradiated mice. This effect was especially pronounced in mice irradiated with 7 and 8 Gy of X-rays. It seems that radioprotective efficiency of fullerenol C₆₀(OH)₂₄ is more marked in mice irradiated by higher doses of X-rays. (orig.)

[en] A number of investigators have shown that isotope effects in metal hydride systems can be used for the separation of hydrogen isotopes. The processes that have been demonstrated include displacement chromatography, pressure swing absorption, temperature swing absorption, and membrane permeation. At the present stage of development, hydride methods are potentially competitive with other methods for small and intermediate scale applications. (author) 58 refs., 6 figs., 3 tabs

[en] We demonstrate that the first principles band calculation accounts well for the completely different phase diagrams among Cu-Ag, Cu-Au and Ag-Au alloy systems. It is argued that the charge transfer will not be a crucial factor in producing this difference, being in contradiction with Miedema's empirical interpretation. Rather, an important role of the structure in the density of states at the Fermi level is pointed out. The many-body interaction parameters, which depend on the lattice constant, are derived by using Connolly and Williams' prescription. With these parameters, a detailed discussion is given on the effects of lattice constant mismatch on the alloy phase stability. (author) 11 refs., 5 figs