A.Taguchi, M.yTanizawa, S.Akamaru, T.Abe

Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract

　Catalytic hydrogenation of Cyo₂over α-Al₂O₃ supported Ru nanoparticles (Ru/Al₂O₃)prepared by"barrel-sputtering and conventional "wet impregnation" methods was investigated. Highly dispersed Ru nanoparticles were obtained by using the barrel-sputtering method. The mean particle diameter of Ru nanoparticles increased from ca. 5.5 to ca. 13.2 nm with an increase in the amount of Ru loaded. On the other hand, Ru particles were agglomerated when the impregnation method was used. Mean particle diameter of resultant Ru particles was 13.4 nm. Both catalysts showed selective methane production by hydrogenation of CO₂, and Ru/Al₂O₃ prepared by the barrel-sputtering method exhibited higher activity than that of Ru/Al₂O₃ prepared by the wet impregnation method. The turnover number (TON) of methane formation linearly decreased with an increase in the mean diameter of Ru nanoparticles.

K. Watanabe, Y. Torikai, M. Hara, Y. Hatano

Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract

Adsorption and desorption of water over Cr-oxide and alumina are of great concern with the contamination of stainless steel and gas chromatographic isotope separation. However,the mechanisms of those phenomena have not been fully clarified. A preliminary ab inito study on the behavior of water molecules on the (001) surfaces of α-Cr₂O₃ and α-Al₂O₃ was carried out for small clusters of Me4O4 (Me=Cr or Al) by use of the Gaussian 03 package. It was found that water molecules can be adsorbed molecularly and dissociatively on these surfaces. Molecular adsorption of a H₂O molecule takes place on a metal atom of the cluster as Me-OH₂, with the bond length of about 2.0 Å. Dissociative adsorption occurs by forming Me-OH (on-top site) or Me2-OH (bridge site) and O-H bonds. There appeared a feature that the bond length of Me2-OH is greater than that of Me-OH. Calculated adsorption energies were examined by comparing with the values estimated from the thermal desorption spectra of water for α-Cr₂O₃ and γ-alumina. The ab initio calculations coincided quite well with the observed thermal desorption spectrum for α-Cr₂O₃, whereas they did not for γ-alumina. Further studies are required to clarify the structures of adsorbed species, adsorptiron energies and kinetic processes.

S.Naoe, Y.Torikai, K.Akaishi,R.-D Penzhorn, K.Watanabe, M.Matsuyama

Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract

The release behavior of tritium from stainless steel 316 previously loaded with tritium gas was investigated isothermally under an argon gas flow or under vacuum conditions. Depth profiles of the heated specimens were determined by chemical etching. The experimental release rate and tritium depth profiles in the solid could be simulated with a model based on bulk diffusion. The diffusion coefficients used to fit the depth profiles of specimens heated under vacuum conditions were not discernible from those obtained for specimens heated under an argon gas flow at the same temperature.

K.Shimada¹, H.Hommae²,Y.Hatano¹, M.Matsuyama ¹

¹Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
²Institute of Laser Engineerlng, Osaka University, Yamadaoka 2-6 Sulta 565-0871, Japan

Abstract
Tritium distribution on/beneath a mechanically-treated surface of vanadium was examined by an imaging plate (IP) technique. Enrichment of tritium was observed around WC indentation lefts and was ascribed to the trapping effects of defects induced by plastic deformation. 0n the other hand, such an increase in tritium concentration was not observed around the lefts of Vickers indentation due to a smaller extent of plastic deformation and higher compressive stress. The accuracy and spatial resolution of the IP technique were sufficient to distinguish the difference in tritium distributions in the areas treated by two different methods.

S.Akamaru, A.Taguchi, T.Abe

Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract

　Ni nanoparticles were deposited on Al₂0₃ particles with a diameter of 0.3 μm by the barrel sputterlng technique, and analyzed the prepared samples by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD pattern of the prepared sample did not show any diffraction peak assigned to the Ni metal. On the other hand, both Ni metal and NiO peaks appeared clearly in the XRD pattern or a sample annealed at 873 K for 3 hours. From TEM observations, lt was confirmed that the morphology of Ni deposited on Al₂0₃ particles was not a thin film but nanoparticles with diameters of 2 nm to 20 nm and that the Ni particles partially crystallized. After annealing, Ni particles were aggregated and the average diameter became 24.2 mm. The results of TEM observation were consistent with the results of XRD measurements. The magnetic properties of Ni nanoparticles deposited on Al₂0₃ particles were also examined. The prepared samples showed superparamagnetism, which is one of the characteristic behaviors of magnetic nanoparticles. An exchange-bias effect was also observed, and the effect was reduced by annealing. The magnetic behaviors are explained by the core-Ni shell-NiO structure, which results from the creation of a passivative oxide layer on the Ni nanoparticles in air.

T.Nakazawa¹, M.Hara², S.Akamaru², K.Nishimura¹, M.Matsuyama²

¹Faculty of Engineering,University of Toyama, Gofuku 3190, Toyama 930-8555, Japan
²Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract

A vessel was designed to examine changes in electrical resistance of hydrogen-absorbing alloys to hydrogen gas absorption. Performance tests on the designed vessel were carried out using palladium and its alloys.The equilibrium pressure and relative resistance-composition curves of palladium obtained by using the vessel agreed with values the reported in the literature. The designed vessel can therefore be used for simultaneous measurements of relative electrical resistance and equilibrium pressure.