2001 Fiscal Year Final Research Report Summary
DEVELOPMENT OF NEW NONDESTRUCTIVE INSPECTION METHOD FOR CREEP RUPTURE OF HEAT-RESISTING FERRITE STEELS USING POSITRON ANNIHILATION TECHNIQUE
Project/Area Number |
12640334
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Research Category |
Grant-in-Aid for Scientific Research (C)
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Allocation Type | Single-year Grants |
Section | 一般 |
Research Field |
固体物性Ⅱ(磁性・金属・低温)
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Research Institution | TOHOKU UNIVERSITY |
Principal Investigator |
TANG Zheng TOHOKU UNIVERSITY, INSTITUTE FOR MATERIALS RESEARCH, RESEARCH ASSOCIATE, 金属材料研究所, 助手 (80271972)
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Co-Investigator(Kenkyū-buntansha) |
YUBUTA Kunio TOHOKU UNIVERSITY, INSTITUTE FOR MATERIALS RESEARCH, RESEARCH ASSOCIATE, 金属材料研究所, 助手 (00302208)
NAGAI Yasuyoshi TOHOKU UNIVERSITY, INSTITUTE FOR MATERIALS RESEARCH, ASSOCIATE PROFESSOR, 金属材料研究所, 助教授 (10302209)
HASEGAWA Masayuki TOHOKU UNIVERSITY, INSTITUTE FOR MATERIALS RESEARCH, PROFESSOR, 金属材料研究所, 教授 (80005975)
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Project Period (FY) |
2000 – 2001
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Keywords | POSITRON ANNIHILATION / EMBEDDED NANO CRYSTAL / FERMI SURFACE / AFFINITY INDUCED POSITRON TRAPPING |
Research Abstract |
It is well known that nano particles embedded in materials show unique characteristics different from the bulk materials. However, the electronic state of the embedded particles is hardly revealed experimentally because there is no tool to probe such particle sensitively. Recently, we have found that positron annihilation technique can reveal the electronic structure of the embedded particles utilizing "affinity induced positron giant trapping". In this study, we measure the Fermi surface of metal nano crystals embedded in solids by positron annihilation for the first time, and the corresponding first-principles calculations are performed and compared with the experimental results. In the present work, we observed the Fermi surface of bcc Cu nano-crystals embedded coherently in bcc Fe as the first example. The Cu nano-crystals Fe were obtained by thermal aging a single crystal of a dilute Fe-Cu alloy (Fe-1. 0wt%Cu). The single crystal was prepared from high-purity Fe (4N) and Cu (5N) by
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arc melting, followed by strain-annealing method. It was heated to 825 degree C and kept 4h, followed by quenching into ice water, and thermally aged at 550 degree C for 0.1 h. Then, the Cu atoms are aggregated to form nano-crystals (about 1 nm in diameter) coherent to the bcc Fe matrix. Two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) was measured to obtain the momentum distribution of the bcc Cu directly. While the Fermi surface of bulk fcc Cu has necks at the eight L-point of the fcc Brillouin zone, that of bcc Cu has the necks of the twelve N-point of the bcc Brillouin zone, the characteristic of the topology is quite different from that for bulk Cu. We also performed the first-principles calculations of electronic structure of bcc Cu based on FLAPW method. The calculated results well reproduced the above experimental results. The present results show that the positron annihilation provides us with a unique method to probe the electronic structure of the nano-crystals embedded in materials. Less
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Research Products
(20 results)