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[2001_01]
The Fourth Pacific Rim International Conference on Advanced Materials and Proceeding (PRICM4)
Yuji Hatano, Kuniaki Watanabe
Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 933-8555, Japan
Abstract
Hydrogenation of MgNi2 by hydrogen plasma
was examined at elevated temperatures. Powder of MgNi2 was compacted
into a disk and heated in vacuum at 773 K. MgNi2 was transformed
into MgNi2 by evaporation of Mg. This specimen was hydrogenated
by rf-discharged hydrogen plasma (10-30 Pa) at 673 and 773 K. At 673 K,
hydrogen was not absorbed. At 773 K, however, the specimen was hydrogenated
up to [H]/[M]=0.14 within 25 ks. New peaks appeared in the X-ray diffraction
pattern at 2θ=34.0, 42.0, 48.9, and 86.6°.
The peaks at 42.0, 48.9, and 86.6° were assigned to Ni hydride, which
can be formed in hydrogen gas atmosphere at high pressure (10 8
Pa). Hydrides of Mg and MiNi, however, were not observed.
Keywords: magnesium (Mg). nickel (Ni), intermetallic
compound, hydrogen, hydride, plasma, atom
[2001_02]
Journal of Nuclear Science and Technology, 38(11) (2001) 952-958
Kan Ashida 1, Yuji Hatano 1, Wataru
Nishida 1, Kuniaki Watanabe 1
Asami Amano 2, Kenji Matsuda 2, Susumu Ikeno 2
1 Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama-shi, Toyama 930-8555
2 Department of Material Systems Engineering and Life Science, Faculty of Engineering, Toyama University, Gofuku 3190,
Toyama-shi, Toyama 930-8555
Abstract
Effect of Pd coating on recovery of hydrogen isotopes from inert gas atmosphere was investigated for intermetallic compounds ZrNi. Powder of ZrNi was coated with Pd by electroless plating. Subsequent annealing at 1073 K led to the formation of ZrPd at the powder surface. The durability in deuterium recovery from Ar gas was examined for the bare and the Pd-coated powders at temperatures from 373 to 573 K as well as the kinetics of deuterium absorption and desorption. The absorption and desorption of deuterium obeyed the first and the second order kinetics, respectively. The ZrPd layer on ZrNi did not alter the absorption and the desorption kinetics, The deuteium recovery by the bare powder was degraded with time owing to oxidation of powder surfaces by impurities contained in the Ar gas. The durability in deuterium recovery was markedly improved by Pd coating, and no significant degradation was observed for the Pd-coated specimen at 573 K. This difference in the durability was ascribed to the difference in the oxidation behavior between ZrNi and ZrPd. It was concluded that Pd coating significantly improves the applicability of ZrNi to tritium recovery in blanket systems.
[2001_03]
Journal of Nuclear Materials, 290-293 (2001) 437-442
M. MATSUYAMA a), T. TANABE b), N.
NODA c), V. PHILIPPS d), K. H. FINKEN d), K. WATANABE a)
a) Hydrogen Isotope Research Center, Toyama university, Gofuku 3190, Toyama 930-8555, Japan
b) Center for Integrated Research in Science and Engineering,
Nagoya University, Nagoya 464-8603, Japan
c) National Institute for Fusion Science, Oroshi-cho, Toki 509-5292, Japan
d) Institute of Plasma Physics, Julich Research Center, Julich 52428, Germany
Abstract
Applicability of a newly developedβ-ray
induced x-ray spectrometry (BIXS) has been examined to measure nondestructively
tritium retained on/in the graphite samples. Examination was carried out
by using the graphite plates irradiated with tritium ions and an ALT-2
limiter tile exposed to D-plasmas in TEXTOR. For the former samples, a
sharp intense peak and a broad weak peak appeared clearly in the spectra;
the former peak was attributed to the characteristic x-rays from argon
used as a working gas, and the latter peak was assigned to the bremsstrahlung
x-rays from sub-surface layers of graphite. On the other hand, for the
latter sample, a rather weak characteristic x-ray peak was observed along
with a diminutive bremsstrahlung x-ray peak. Although the intensities of
those x-rays differed from spot to spot, the tritium levels retained on
the limiter tile were determined to be 58-132 Bq/cm2. It was
concluded, therefore, that valuable information on the amount and the distribution
of tritium retained on/in the wall materials can be nondestructively obtained
by using the BIXS.
Keywords: Surface tritium measurement; β-ray
induced X-ray spectrometry (BIXS); Tritium retention; Graphite materials
[2001_04]
Journal of Nuclear Materials, 290-293 (2001) 42-46
K. Ashida a, K. Fujino b, T. Okabe
b, M. Matsuyama a, K. Watanabe a
a Hydrogen Isotope Research Center, Toyama
University, Gofuku 3190, Toyama 930-8555, Japan
b Department of Physics, Faculty of Science,
Toyama University, Gofuku 3190, Toyama 930-8555, Japan
Abstract
The solid-state reaction between hydrogen-containing
carbon and tungsten was studied by means of infrared, Raman, X-ray photoelectron
(XPS) and thermal desorption (TDS) spectroscopies. Infrared and Raman spectroscopies
revealed that as-prepared hydrogen-containing films were composed of carbon
atoms with sp2 and sp3 hybridized orbitals, where
hydrogen was bound to carbon as-CH3 and >CH2. Vacuum
heating of the carbon films deposited on tungsten caused thermal desorption
peaks of hydrogen at about 723 and 1173 K in TDS. The former was accompanied
by other desorption of CO, CO2 and hydrocarbons, whereas the
latter was evolved with only a minor amount of CO. It was observed by XPS
that the W4f peak began to appear at about 773 K, with an increasing surface
composition corresponding to tungsten carbide at 1273 K. These observations
indicate that a solid-state reaction between the carbon film and tungsten
took place extensively above 973 K to yield an intermetallic compound of
W2C at 1273 K.
Keywords: Tungsten; Carbon; Co-deposition; Solid-state
reaction; Heat load; Hydrogen
[2001_05]
Journal of Japan Institute of Light Metals, 51(1) (2001) 23-27
Shotaro Morozumi *, ***, Hiroshi Saikawa **, Kuniaki Watanabe ***
* Magnesium Research Center, Chiba Institute
of Technology, Tsudanuma 2-17-1, Narashino-shi, Chiba 275-0016
** Department of Metallurgical Engineering,
Chiba Institute of Technology, Tsudanuma 2-17-1, Narashino-shi, Chiba 275-0016
*** Hydrogen Isotope Research Center, Toyama University
**** The term "demagnesization" used here
means the depletion of magnesium from the specimen by sublimation
Abstract
Cut pieces of cast Mg2Ni ingot were
heated in a vacuum of about 10 -2 Pa for 1.8-14.4 Ks at 773,
823 and 873 K, and then examined using X-ray diffraction, optical microscopy
and electron probe X-ray microanalyzer with EDX. The vacuum heating resulted
in the demagnesization of Mg2Ni phase by sublimation of magnesium
from the surface, forming porous layer of MgNi2. Thickness of
the layer increased with increasing temperature and/or heating time. Approximate
estimation, using these kinetic data, showed that apparent activation energy
of the growth of the layer was 210 kJ/mol. Based on the estimation, the
whole Mg2Ni specimen with 0.7x10 -3 m thickness was
found to change into the porous MgNi2 after vacuum-heating for
14.4 ks at 923 K.
Keywords: Mg2Ni, MgNi2, demagnesization, magnesium, pore
*The text is Japanese.
[2001_06]
The Fourth Pacific Rim International Conference on Advanced Materials and Processing (PRICM4)
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 6 cycles was still
ca. 220 mA/g, which was about two-times larger than that for the unmodified
sample. In the cyclic voltammogram (CV) obtained for the carbon-modified
samples using the micro-paste electrode technique, the potential at rising
of the cathodic current shifted to the anodic direction and the anodic
peak was shaper and larger in comparison with that for the unmodified sample.
Moreover, the CV observed for a carbon-modified sample immersed in 6N KOH
solution, which can be regarded as a degraded sample, revealed that the
deposited carbon suppressed the reduction in the electron transfer rate
due to Mg(OH)2 formation.
Keywords: rechargeable hydrogen batteries; micro-paste
electrode technique; amorphous MgNi; Mg(OH)2