T. Abe
Hydrogen Isotope Research Center, University of Toyama 3190 Gofuku, Toyama 930-8555

Abstract

Particle surface modification of powdered materials has currently attracted considerable attention in various industrial and scientific fields. However, conventional wet processes, such as plating and impregnation method, produce wastewater streams containing potentially harmful residual chemicals. In addition, the wet processes involve the decomposition of precursors by heating and chemical reduction, which interfere with controlled surface modification. To avoid such drawbacks of wet processes, we have developed novel particle surface modification methods based on the plasma technologies. In our original surface modification methods, a polygonal barrel containing the powdered sample is rotated or oscillated to stir the particles during treatment, achieving the uniform modification of the particle surfaces. Since plasma technologies used in our methods are categorized as dry processes, they do not accompany wastewater discharge. Furthermore, the treatment in our methods is carried out without heating or chemical reduction, allowing controlled surface modification. This report describes the particle surface modification using the "polygonal barrel-sputtering method", "polygonal barrel-plasma chemical vapor deposition method", and "polygonal barrel-plasma treatment method".

V. Kh. Alimov¹, Y. Hatano¹, K. Sugiyama², I. Takagi³,M. Matsuyama^3
1Hydrogen isotope research center, University of Toyama Gofuku 3190, Toyama 〒930-8555, Japan
²Max-Planck-Institut fur Plasmaphysik, EURATOM Association, D-85748 Garching, Germany
³Department of Nuclear Engineering, Kyoto University Kyoto 606-8501, Japan

Abstract

Influence of Pd deposition on deuterium (D) retention in W samples irradiated with W self-ions was examined to understand the correlation between the probability of occupation of radiation-induced traps by D and the concentration of D in a solid solution state under plasma exposure. W samples were irradiated with 4.8 MeV W ions to 0.65 and 12 dpa, and a thin Pd layer was deposited on the sample with the higher damage level by a technique of sputter-deposition. Then, the samples were exposed to DC glow-discharge D plasma at 403 K. In spite of the higher damage level, the concentration of trapped D in the damaged zone of the Pd-covered sample was far smaller than that in the non-covered one. The small D retention in the Pd-covered sample was explained by a decrease in the D concentration in the solution state owing to the enhanced recombinative release by Pd and the consequent reduction in the occupation probability of radiation-induced traps. These observations indicated that tritium inventory in neutron-irradiated W materials can be significantly reduced by enhancement of tritium reemission by surface modifications.

Y. Okushima, M. Inoue, T. Abe
Hydrogen Isotope Research Center, University of Toyama, Gofuku 3190, Toyama 930-8555, Japan

Abstract

  Degradation of a carbon-supported Pt (Pt/C) catalyst used at the cathode of polymer electrolyte fuel cells was investigated. The Pt/C sample was prepared by the polygonal barrel-sputtering method. The results showed that the Pt nanoparticles were highly dispersed on the powder carbon support. The cyclic voltammograms of the prepared Pt/C sample showed that the Pt particles were electrochemically cleaned by 100 repetitions of the potential cycling. Further continuation of potential cycling, however, resulted in the gradual decrease in H adsorption/desorption currents, indicating a loss of the electrochemical surface area (ESA) of the deposited Pt. Note that the ESA obtained after the 4000th potential cycling was ca. 20% of that at 1st potential cycling, and the decrease in the ESA is most likely attributed to the growth and aggregation of the deposited Pt particles.

M. Hara^a, R. Mizuuchi^a, K. Miyao^a, M. Matsuyama^a, A. Hirata^b, Y. Oya^c.K. Okuno^c
a Hydrogen Isotope Research Center, University of Toyama Gofuku 3190, Toyama 930-8555, JAPAN
^b Center for Research and Development in Natural Sciences, Instrumental Analysis Laboratory, University of Toyama Gofuku 3190, Toyama 930-8555, JAPAN
^cRadioscience Research Laboratory, Faculty of Science, Shizuoka University Ohya 836, Suruga-ku Shizuoka 422-8529, Japan

Abstract
  To understand the mechanisms of the gas evolution fromLi_2+xTiO_3+y stored in moist air, their weight loss curves were measured in a helium atmosphere with a thermal gravimeter. No weight loss was observed Li_2.0TiO₃ stored in moist air in the temperature range from ambient temperature to 800 ℃. On the other hand, the weight loss curves of Li_2.2TiO_3+y and Li_2.4TiO_3+y stored in moist air showed two steps. The first step began around 100 ℃, and the second step started around 650 ℃. The first and second weight loss steps were attributed to H₂O and CO₂ evolutions, respectively. The CO₂ evolution in the second step resulted from the thermal decomposition of Li₂CO₃, which was produced by the reaction between Li₄TiO₃ and CO₂ during storage. However, the reaction causing the first step could not be identified.

A. Taguchi, Y. Torikai, M. Matsuyama
Hydrogen Isotope Research Center, University of Toyama, Toyama 930-8555, Japan

Abstract

  The mesostructure and tritium desorption properties of as-synthesized MCM-41 and that after 5 cycles of sequential H₂O impregnation/desorption have been compared. The XRD and tritium desorption experiments showed good reusability and reproducibility in the enrichment of tritiated water.

S. Akamaru, M. Hara, M. Matsuyama

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

Abstract

  We evaluated the electrical resistivity of Pd hydride without electrical contact. An alternating current susceptometer was used to measure the electrical resistivity. When columnar samples were used, it was possible to determine their relative electrical resistivity was obtained after simple analysis. The relative electrical resistivity increased monotonically with increasing hydrogen concentration in the Pd rod. At lower hydrogen concentrations, the obtained relative electrical resistivity was approximately the same as that reported previously, indicating that the alternating-current susceptometer correctly measured relative electrical resistivity. At higher hydrogen concentrations, the results differed from the values reported previously. Sample shape and geometry must be considered to obtain accurate values at higher hydrogen concentrations.