Crystallographic and magnetic properties of UFe5.8Al6.2 single crystals

Single crystals of UFe5.8Al6.2 were characterised by X-ray and neutron diffraction, 57Fe Mössbauer spectroscopy and magnetisation. The structure refinement by X-ray and neutron diffraction shows a ThMn12-type structure, the Fe atoms fully occupying the 8f and partially occupying the 8j positions. Mössbauer spectra confirm these occupations and further indicate a magnetic ordering below 293 K. Magnetisation measurements show a ferromagnetic behaviour below 300 K, with a and b as easy directions and a spontaneous magnetisation of 10.4 [mu]B/f.u. at 5 K, due to the Fe occupation of 8j position. These single crystal results significantly differ from those previously obtained in UFe6Al6 polycrystalline samples obtained by melting and annealing.http://www.sciencedirect.com/science/article/B6TJJ-3V7WTYX-N/1/f7893080a7f27a628198f02aeb40fe2

Highly efficient separation of actinides from lanthanides by a phenanthroline-derived bis-triazine ligand

The synthesis, lanthanide complexation, and solvent ex- traction of actinide(III) and lanthanide(III) radiotracers from nitric acid solutions by a phenanthroline-derived quadridentate bis-triazine ligand are described. The ligand separates Am(III) and Cm(III) from the lanthanides with remarkably high efficiency, high selectivity, and fast extraction kinetics compared to its 2,2'-bipyridine counterpart. Structures of the 1:2 bis-complexes of the ligand with Eu(III) and Yb(III) were elucidated by X-ray crystallography and force field calculations, respec-tively. The Eu(III) bis-complex is the first 1:2 bis-complex of a quadridentate bis-triazine ligand to be characterized by crystallography. The faster rates of extraction were verified by kinetics measurements using the rotating membrane cell technique in several diluents. The improved kinetics of metal ion extraction are related to the higher surface activity of the ligand at the phase interface. The improvement in the ligand's properties on replacing the bipyridine unit with a phenanthroline unit far exceeds what was anticipated based on ligand design alone

Surface studies of UFe2 and evaluation of its catalytic properties with a 2H2:CO mixture

The reactivity of UFe2 with O2, CO and CO2 were studied using x-ray photoelectron spectroscopy (XPS). Adsorption of O2 on clean UFe2 surfaces (Fe/U approx. = 2.0), produced by argon-ion sputtering, leads to the formation of UO2 and depletion of Fe from the surface layer probed by XPS (Fe/U approx. = 0.8). The oxidation state of Fe in this layer, as determined by XPS (Fe 2p/sub 3/2/ = 710.4 eV), is between Fe S and Fe T of pure Fe oxides. Exposure of sputtered-clean UFe2 to CO and CO2 results in a slight broadening of the U 4f peaks, indicating U oxidation, and some Fe depletion in the analyzed layer (Fe/U approx. = 1.7). The O ls (530.2 and 530.4 eV for CO and CO2, respectively) and C ls (282.7 and 282.6 eV for CO and CO2, respectively) indicate that dissociative chemisorption to O and C atoms occurs. UFe2 ground into a fine powder was tested as a catalyst in a differential high-pressure flow reactor with a 2H2:CO gas mixture. A significant amount of methanol and hydrocarbons are produced at 577K; while hydrocarbons are the main products (>99%) at 739K. XPS analysis of the used catalyst indicates that U is present as UO/sub 2+x/ and Fe as Fe2O3

Single crystal and film growth of actinide pnictides by chemical vapour transport

Single crystals and films of actinide (Th, Pa, U) pnictides (As, Sb) were prepared from the elements, by chemical vapour transport using iodine as transporting agent. In a van Arkel process, the actinide compounds were deposited on an induction-heated tungsten support. Depending on the compounds, deposition temperatures ranged from 1 000 to 2 200 °C, whereas the quartz bulb was kept at 400 to 600 °C. The deposits were identified and characterized by X-ray diffraction (Debye-Scherrer, rotating crystal, Weissenberg) methods