| Project/Area Number |
11640580
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
機能・物性・材料
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| Research Institution | NIIGATA UNIVERSITY |
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Principal Investigator |
MASUDA Yoshio Faculty of Science, NIIGATA UNIVERSITY, Professor, 理学部, 教授 (50018347)
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| Co-Investigator(Kenkyū-buntansha) |
YUKAWA Yasuhiko Faculty of Science, NIIGATA UNIVERSITY, Associate Professor, 理学部, 助教授 (50200861)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2000: ¥700,000 (Direct Cost: ¥700,000)
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| Keywords | Hydrogen Storage Metals / Siebert-type Apparatus / DV-X α Method / Electronic Structure Analysis / Cluster Model / 圧力等温線(PCT線) / DV-Xa法 |
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| Research Abstract |
The Siebert-type apparatus was made to measure pressure-concentration-isotherm (PCT) diagrams of metal hydrogen systems. The apparatus equipped with a horizontal sample container, was improved to minimize the dead space. A leak rate of the hydrogen of the apparatus was 4.82 x 10^<-4> Pa dm^3 s^<-1>. When PCT diagrams of LaNi_<4.5>Co_<0.5> - hydrogen systems were measured using this apparatus, the reproducibility of the diagram was invariably good. The enthalpy change (ΔH) and entropy change (ΔS) determined for LaNi_<4.5>Co_<0.5> -H_6 were -32.7 kJ mol(H_2)^<-1> and 113 J mol (H_2)^<-1> K^<-1>, respectively.
The electronic structures of LaNi_5 , LaNi_5H_<0.2> (α phase ; P6/mmm) and LaNi_5H_6 (β phase ; P31m) were investigated by means of the DV-X α cluster method to understand the interaction between hydrogen and metals. It is found that the hydrogen atoms make a strong chemical bond with Ni (1) atoms rather than La atoms in both the phases of α and β. These results were not accord with the expectation from the heat of formations of the hydrides of La and Ni.
In the case of LaNi_<4.5>Co_<0.5>, the bond order of Ni - Co changed somewhat stronger than that of Ni - Ni. This finding is consistent with the experimental results that LaNi_5 fails easily than LaNi_<4.5>Co_<0.5> by repetition of the procedure of the hydrogen absorption and desorption. The interaction between the metals and hydrogen atoms seems to be affected by the cluster size. The small cluster model (HNi_<13>La) was used in this study, it is necessary to study the electronic structures for larger cluster models than that used in this study.
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