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Y Miyake

Bio: Y Miyake is an academic researcher from Kansai University. The author has contributed to research in topics: Hydride & Hydrogen. The author has an hindex of 2, co-authored 2 publications receiving 76 citations.

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TL;DR: The hydrogen absorption and desorption characteristics of mischmetal (Mm)-nickel-aluminum alloys were investigated in this paper, where the same hexagonal structure as LaNi5 and MmNi5 was found to react readily with hydrogen to form the hydrides MnNi4.5Al0.75 Al0.5A10.
Abstract: The hydrogen absorption and desorption characteristics of mischmetal (Mm)-nickel-aluminum alloys were investigated. MmNi5−xAlx (x = 0.25 −0.5) have been found to have the same hexagonal structure as LaNi5 and MmNi5, and they reacted readily with hydrogen to form the hydrides MmNi4.75 Al0.25H5.4, MmNi4.65Al0.35H 5.3H5.3 and MmNi4.5Al0.5H4.9 (hydrogen content: 1.3,1.2 and 1.2 wt.%, respectively) under 60 atm hydrogen pressure at room temperature. The dissociation pressures of these hydrides were dependent on the aluminum content (aluminum partially substitutes for nickel) and the value of log Pbecame lower than the value for MmNi5 hydride as x increased. The enthalpy change on hydride formation as determined from the dissociation isotherms for the MmNi4.5Al0.5-H system was − 5.5 kcal (mol H2)−1; this value was smaller than those for LaNi5 and MmNi5. The dissociation pressure at 30 °C was 3 atm and was nearly the same as that of LaNi5. The desorption rate of hydrogen for MmNi4.5Al0.5 was larger than those for LaNi5 and MmNi5) and a value of 2.1 – 4.3 kcal mol−1 was obtained for the apparent activation energy of hydrogen desorption. For MmNi4.5Al0.5 the hydrogen absorption-desorption cycle was repeated 30 times, but no variation in the hydrogen absorption-desorption capacity was observed. The hydride of MmNi4.5A10.5 proved to be suitable for use as a stationary hydrogen storage material.

66 citations

Journal ArticleDOI
Yasuaki Osumi1, H. Suzuki1, Akihiko Kato1, M Nakane1, Y Miyake 
TL;DR: In this paper, the hydrogen absorption and desorption characteristics of Ti-Co-Mn alloys were investigated and it was shown that the dissociation pressures of these hydrides are dependent on the manganese content and the value of log P increases gradually with increasing x.
Abstract: The hydrogen absorption and desorption characteristics of Ti-Co-Mn alloys were investigated. Alloys of composition TiCo 1− x Mn x ( x = 0.05 – 0.5) were found to have the same cubic structure as TiCo and they reacted readily with hydrogen to form the hydrides TiCo 0.95 Mn 0.05 H 1.4 , TiCo 0.9 Mn 0.1 H 1.4 , TiCo 0.8 Mn 0.2 H 1.6 and TiCo 0.5 Mn 0.5 H 1.7 (hydrogen content 1.3, 1.3, 1.4 and 1.6 wt.% respectively) under a hydrogen pressure of 30 atm at room temperature. The dissociation pressures of these hydrides are dependent on the manganese content x (the manganese partially substitutes for the cobalt) and the value of log P increases gradually with increasing x . In addition, with increasing x , the width of the plateau in the isotherms becomes greater than that of TiCo hydride and the hydrogen content increases. The enthalpy change on hydride formation determined from the dissociation isotherms for the TiCo 0.5 Mn 0.5 −H system is −11.2 kcal (mol H 2 ) −1 ; this value is smaller than that of the TiCo-H system. The temperature required to produce a dissociation pressure of 1 atm is 90 °C, which is lower than the temperature required for TiCo (130 °C). The desorption rate of hydrogen for TiCo 0.5 Mn 0.5 is greater than that for TiCo, and a value of 9.9–11.4 kcal mol −1 was obtained for the apparent activation energy of hydrogen desorption. For TiCo 0.5 Mn 0.5 , only two cycles under mild conditions are needed for the activation treatment so the alloy can be easily activated. The hydrogen absorption-desorption cycles were repeated 30 times but no variation in the hydrogen absorption-desorption capacity was observed. The hydride of TiCo 0.5 Mn 0.5 proved to be suitable for use as a hydrogen storage material.

12 citations


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TL;DR: In this article, a columnar structure was formed so that the c -axis of the hexagonal structure was oriented parallel to the cooling plane, and the cylindrical sealed cell also showed a very long cycle life (a capacity decay of 6% after 2000 cycles).

177 citations

Journal ArticleDOI
TL;DR: In this article, a review of the alloy groups which absorb large quantities of hydrogen is presented, with emphasis placed on thermodynamic and kinetic properties, activation and deactivation, poisoning effects and storage capacity.
Abstract: Metal hydrides, as energy storage media, are receiving considerable attention. The amount of literature concerning the properties of these materials has increased markedly over the past few years. In this paper, we conduct a review of the alloy groups which absorb large quantities of hydrogen. These alloy classes are designated as AB5, AB, AB2, AB3 and A2B7 and Mg-based compounds. These materials are discussed with emphasis placed on thermodynamic and kinetic properties, activation and deactivation, poisoning effects and storage capacity.

153 citations

Journal ArticleDOI
TL;DR: Several hydrogen getter materials of potential interest for the handling, transport, and storage of tritium were compared on the basis of properties such as dissociation pressure, storage capacity, P-c isotherms, rate of hydrogen uptake, recoverability of the gettered hydrogen, reactivity with impurities, characteristics of the fusion fuel cycle, pyrophoricity in air and in pure oxygen, aging, employing data from the literature as well as results from experiments carried out during the course of this study.

149 citations

Journal ArticleDOI
TL;DR: In this article, a low-cost negative battery electrode for MmNi-5-based alloys (Mm, mischmetal) was proposed and induction-melting tests showed that the surface region with a columnar structure had a longer cycle lifetime than the inner region with an equiaxed structure.
Abstract: Extensive work has been carried out on utilizing MmNi 5 -based alloys (Mm, mischmetal) as a low cost negative battery electrode. The replacement of nickel by cobalt was effective in improving cycle lifetime but caused a decrease in capacity and high rate capability. The replacement of lanthanum by large amounts of cerium of neodymium gave the alloy a satisfactory cycle lifetime with small amounts of cobalt present and without impairing the high rate capability. The alloy MmNi 3.5 Co 0.7 Al 0.8 was selected consistent with the above requirements. Induction-melting tests showed that the surface region with a columnar structure had a longer cycle lifetime than the inner region with an equiaxed structure. Annealing treatment also caused a decrese in the cycle lifetime. It was considered that alloys with smaller crystal grains had a longer cycle lifetime because the protective surface layer on the grain would remain effective after pulverization. The deviation from stoichiometric composition to the nickel-rich side or the Mm-rich side also caused a decrease in cycle lifetime, accompanied by the precipitation of nickel or Mm on the grain boundaries. It was concluded that the surface layer of the crystal grain played a very important role in preventing capacity decay.

114 citations

Journal ArticleDOI
TL;DR: The production of small-sized Ni-MH batteries, which amounts to some 40% of market share for portable appliances, is still growing because of an increase in the energy density per volume and also a reduction in price.

104 citations