2000 Fiscal Year Final Research Report Summary
Development of Diffraction Techniquesfor Studying Phase Transformation (Synchrotron Radiation and High-Resolution Electron Microscopy)
| Project/Area Number |
09242102
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas
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| Allocation Type | Single-year Grants |
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| Research Institution | Tohoku University |
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Principal Investigator |
HIRAGA Kenji Tohoku Univ. Institute for Materials Research Professor, 金属材料研究所, 教授 (30005912)
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| Co-Investigator(Kenkyū-buntansha) |
OHSHIMA Ken-ichi Univ. of Tsukuba Institute of Applied Physics Professor, 物理工学系, 教授 (70109271)
SHIODO Daisuke Tohoku Univ. Institute for Advanced Materials Processing Professor, 素材工学研究所, 教授 (20154396)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Phase transformation / X-ray diffraction / Energy filtering / Energy loss spectroscopy / Quasicrystal / Martensite / Diffuse scattering |
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| Research Abstract |
The results in the present work are summarized as follows.
1) By introducing the omega-type magnet into a conventional electron microscope, the energy-filtering electron diffraction method was established. With this method, the strong background in the electron diffraction due to the inelastic scattering could be removed and complicated diffuse scattering resulting from the phase transformation could now be analyzed quantitatively. For example, the precursor effects on the martensitic transformation in Ti50Ni48Fe2 were investigated by the energy-filtering electron diffraction and in situ dark field electron microscopy, and the existence and the growth process of microdomains containing a transverse atomic displacement were clarified for the first time. Also, the short-range order parameter in Cu3Pd was determined quantitatively by the energy-filtered electron diffraction method.
2) The kinetics on the nucleation and growth process is an effective approach to investigate the mechanism of first-order phase transformations for non-equilibrium state. In-situ X-ray diffraction data with an accurate temperature controller and highly sensitive detector attached to rota-unit has been obtained from Au-47.5 at%Cd-0.75at.Cu single crystal. It is understood that the nucleus of the low-temperature phase starts from the surface and grows into the inner part gradually.
3) High-angle annular detector dark-field scanning transmission electron microscopy, which is much attention as a new technique for high-resolution electron microscopy, is applied for studying the structure of decagonal quasicrystals. Ordered quasicrystals, which can be interpreted from the projection of NaCl-and CsCl-type hypercubic lattices, have been found.
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