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[2003_01]
Journal of Alloys and Compounds, 352 (2003) 218-225
Masanori Hara, Ryo Hayakawa, Yoshinobu Kaneko, Kuniaki Watanabe
Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
Abstract
Hydrogen induced disproportionation for Zr2Fe,
Zr2Co and Zr2Ni were studied by means of volumetric
measurements of hydrogen absorption and desorption, and X-ray diffraction
analyses of the product phases. These alloys formed respective hydrides
of Zr2MH5 (M=Fe, Co and Ni) type at room temperature
only under conditions of very slow hydrogen absorption, otherwise the alloys
disproportionated. Heating Zr2MH5 to 1073K gave Zr2Ni
and Zr2Co through decomposition, disproportionation and reproportionation.
On the other hand, heating Zr2FeH5 to 1073K yielded
ZrFe2 and Zr3Fe. At the elevated temperature of 773K, each alloy
disproportionated very fast, within several tens of seconds, to ZrH2
and Zr-deficient alloys such as ZrCo, ZrNi and ZrFe for Zr2Co,
Zr2Ni and Zr2Fe, respectively. ZrCo and ZrNi further
disproportionated to ZrCo2 and Zr7Ni10
at this temperature, but the rates were very slow. These observations showed
that the stability to hydrogen induced disproportionation is in the order
of Zr2Ni > Zr2Co > Zr2Fe. This order is
also valid for the ease of reproportionation, although the behavior of
Zr2Fe was completely different from the others.
Keywords: Hydrogen absorbing materials; Zr-based
alloy; Disproportionation; Reproportionation
[2003_02]
J. of Nuclear Materials, 313-316 (2003) 491-495
M. Matsuyama a, N. Bekris b, M.
Glugla b, N. Noda c, V. Phillipps d, K.
Watanabe a
a Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
b Tritium Laboratory, Forschungszentrum Karlsruhe, D-76021Karlsruhe, Germany
c National Institute for Fusion Science, Oroshi-cho, Toki-shi, Gifu 509-5292, Japan
d Institute for Plasma Physics, Forschungszentrum
Julich, Association EURATOM, Trilaternal Euregio Cluster (TEC), 52425 Julich, Germany
Abstract
β-ray -induced X-ray
spectrometry was applied to determine the amounts and depth profiles of
tritium captured by graphite tiles used in the PTE1 campaign and by carbon
fiber composite tiles in the DTE1 campaign of JET. Although, the X-ray
spectra observed for both carbon tiles consisted of characteristic and
bremsstrahlung X-rays, the intensities and shapes of the X-ray spectra
were quite different between these tiles. The analyses of the X-ray spectra
showed that the amount of tritium retained in the latter tile was on average
15,500 times greater than that in the former tile, and the tritium depth
profile extended to 60 μm for the latter tile
compared to 5 μm for the former tile. In addition,
characteristic X-rays corresponding to Cl, Cr, Fe, Ni and Mo appeared in
the latter tile, where Ni showed the highest concentration, indicating
that considerable erosion and deposition of caccum vessel materials took
place in the DTE1 campaign.
Keywords: Amount and depth profile of tritium; Metallic
impurities; Non-destructive measurement; β-ray
-induced X-ray spectrometry; JET divertor tiles
[2003_03]
J. of Alloys and Compounds, 349 (2003) 279-283
Takayuki Abe, Sachio Inoue, Daobin Mu, Yuji Hatano, Kuniaki Watanabe
Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
Abstract
The effect of surface modification of amorphous
MgNi by carbon or Ni was examined by conventional charge/discharge cycle
tests and by a newly developed micro-paste electrode method. The charge/discharge
tests showed that the surface modification by Ni had no effect on the capacity
degradation of amorphous MgNi. The carbon modification, however, clearly
improved the degradation; the discharge capacity after six cycles was still
--220m A/g, which was about twice that of the unmodified sample. In cyclic
voltammograms (CVs) obtained for the carbon-modified samples using the
micro-paste electrode technique, the potential at the rising of the cathodic
current shifted to the anodic direction and the anodic peak was sharper
and larger than those for the unmodified sample. In addition, the CVs observed
for carbon-modified samples immersed in 6N KOH solution, which can be regarded
as degraded samples, revealed that the deposited carbon suppressed the
reduction in the electron transfer rate due to Mg(OH)2 formation.
Potential step measurements for the carbon-modified samples, on the other
hand, showed that carbon modification on MgNi did not affect the diffusion
process of hydrogen.
Keywords: Ni-MH batteries, Micro-paste electrode technique,
Amorphous MgNi, Mg(OH)2
[2003_04]
J. of Nuclear Materials, 320 (2003) 214-222
A. Pisarev a, V. Shestakov b, R. Hayakawa a, Y. Hatano a, K. Watanabe a
a Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan
b The State University of Kazakhstan, Almaty 480100, Kazakhstan
Abstract
Gas-driven permeation of hydrogen through metal membranes in the surface-limited regime (SLR) is analyzed. An analytical solution for the concentration and permeation flux as a function of time is given for permeation through the asymmetric membrane having different conditions on the inlet and outlet sides. The features of the steady state and transient permeation are discussed. Comparison of calculations with an experiment on deuterium permeation through vanadium, which is available from literature, is performed. It has been demonstrated that the parameters, extracted from the measurements of the permeation rate in SLR are very uncertain. Even the calculations with opposite asymmetries can be equally well adjusted to the experiment. Non-zero initial conditions in SLR experiments are additional source of uncertainty. Measurements of the accumulation in a closed volume instead of the permeation rate can seriously mislead in the interpretation of the experiment. Complementary experiments on permeation in two opposite directions and measurements of permeation decay could increase the reliability of the data obtained.
[2003_05]
J. of Nuclear Materials, 320 (2003) 265-271
M. Hara a, Y. Hatano a, T. Abe a,
K. Watanabe a, T. Naitoh b, S. Ikeno b, Y. Honda c
a Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
b Faculty of Engineering, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
c Youtec Company, Nishihirai 986-1, Nagareyama, Chiba 270-156, Japan
Abstract
To improve the durability of hydrogen storage materials against surface poisoning by impurity gases, effectiveness of Pd-coating layer prepared by using a Barrel-Sputtering System was examined for ZrNi powder. The effectiveness of Pd-coating was evaluated by activation temperature, at which Pd/ZrNi poisoned by air could be activated to absorb hydrogen. Characterization of Pd-coated ZrNi (denoted as Pd/ZrNi) by scanning electron microscopy, electron probe microanalysis and X-ray diffraction showed that a uniform Pd-coating layer was formed with the barrel-sputtering system. It was found that the poisoned Pd/ZrNi sample could be activated even at 423 K to absorb hydrogen at room temperature. This exhibits remarkable contrast to bare ZrNi, which could be only activated appreciably above 1073 K. It is concluded that the Pd-coating by barrel sputtering is quite effective to avoid the effect of surface poisoning of powdery hydrogen storage materials. However, the activation at excessively high temperature resulted in the loss of high activity to absorb hydrogen. It was concluded that this phenomenon was associated with reactions between Pd and ZrNi to form PdZr and other byproducts.
[2003_06]
Physica Scripta, T103 (2003) 113-116
R. Hayakawa1, A. Busnyuk2, Y. Hatano1, A. Livshits2, K. Watanabe1
1Hydrogen Isotope Research Center, Toyama University, Toyama 930-8555, Japan
2Bonch-Bruyevich University, 61 Moika, St. Petersburg 191186, Russia
Abstract
A systematic study was carried out on the relation between the surface recombination rate constant of deuterium at a Nb surface and the oxygen concentration in bulk. Oxygen was introduced into a Nb specimen up to concentrations from 0.12 to 4.3 at.%. Then, deuterium was introduced into the specimens, and the surface recombination rate constant was measured by thermal desorption in a temperature range from 623 to 913K. The surface recombination rate constant of deuterium decreased with increasing oxygen concentration in the solid solution phase. This reduction in the recombination rate constant was attributed to the increase of oxygen coverage at the surface with the bulk concentration. Irrespective of the bulk oxygen concentration, no significant increase was observed in the height of the potential barrier against desorption processes.
[2003_07]
Fusion Science and Technology, 44 (2003) 410-414
S. Fukada1, R. A. Anderl2, R. J. Pawelko2, G. R. Smolik2,
S. T. Schuetz2, J. E. O'Brien2, H. Nishimura3, Y. Hatano5,
T. Terai3, D. A. Petti2, D.-K. Sze3, S. Tanaka3
1Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
2Idaho National Engineering and Environment Laboratory (INEEL), Idaho Falls, ID 83415, USA
3University of California, Center for Energy Research, San Diego, CA 92093-0417, USA
4The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
5Toyama University, Gofuku, Toyama 930-8555, Japan
Abstract
Experiment of D2 permeation through Ni facing with purified Flibe is being carried out under the Japan-US joint research project (JUPITER-II). The experiment is proceeding in the following phases; (i) fabrication and assembly of a dual-probe permeation apparatus, (ii) a single-probe Ni/D2 permeation experiment without Flibe, (iii) a dual-probe Ni/D2 permeation experiment without Flibe, (iv) Flibe chemical purification by HF/H2 gas bubbling, (v) physical purification by Flibe transport through a porous Ni filter, (vi) Ni/Flibe/D2 permeation experiment, and (vii) Ni/Flibe/HT permeation experiment. The present paper describes results of the single and dual Ni/D2 permeation experiments in detail.