1999 Fiscal Year Final Research Report Summary
Development of Novel Guest Phases Confined in Carbon Based Micropore Space and Their Properties
| Project/Area Number |
08404048
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 | Tokyo Institute of Technology |
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Principal Investigator |
ENOKI Toshiaki Graduate Scholl of Decision Science, TOKYO INSTITUTE OF TECHNOLOGY, Professor, 大学院・理工学研究科, 教授 (10113424)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAZAKI Akira Graduate Scholl of Decision Science, TOKYO INSTITUTE OF TECHNOLOGY, Assistant, 大学院・理工学研究科, 助手 (40251607)
SATO Hirohiko Graduate Scholl of Decision Science, TOKYO INSTITUTE OF TECHNOLOGY, Assistant, 大学院・理工学研究科, 助手 (90262261)
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| Project Period (FY) |
1996 – 1999
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| Keywords | Nano-Graphite / Intercalation Compounds / Activated Carbon Fiber / Micropore / Spin Glass |
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| Research Abstract |
(1) Nano-graphite derived by the heat-treatment of nano-diamond is investigated in relation to their structures, electronic structures and host-guest systems with potassium and bromine. From Raman spectra and X-ray diffraction, it is found that nano-diamond is converted to nano-graphite around 1600℃. Nano-graphite thus obtained has a novel electronic structure featured with non-bonding π-electron states of edge origin. The non-bonding edge states play an important role in the spin-lattice relaxation mechanism as fast relaxation centers at the edges. The spin-lattice relaxation process is decelerated in less graphitized particles prepared at lower temperatures around 1200℃, which can be explained by the presence of remnant spィイD13ィエD1 regions. Intercalation of potassium makes edge states less important in the electronic structure due to charge transfer from potassium to graphite. The presence of potassium works to enhance the spin-orbit interaction.
(2) The electronic properties of activated carbon fibers are investigated, which consist of disordered network of nano-graphite. Heat-treatment induces an insulator-to-metal transition around 1300℃, due to the development of infinite percolation path networks. In the insulating state, the charging effect works importantly in the electron hopping process, while the metallic state is featured with a considerable amount of disorder. In the vicinity of the insulator-to-metal transition, spin-glass-like disordered magnetism appears where spins of edge-inherited non-bonding states are interacting with the aid of π-conduction-electron mediated interaction. Physisorption of water molecules in micropores surrounding nano-graphite domains induces a reduction of the spin concentration. This can be explained in terms of the enhancement of inter-nano-graphite interaction induced by the effective pressure of introduced water molecules.
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