1996 Fiscal Year Final Research Report Summary
Theoretical calculation and experimental investigation of interganular van-der Waals forces in ceramics
| Project/Area Number |
08455302
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Inorganic materials/Physical properties
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
TANAKA Isao Kyoto Univ., Energy Science, Assoc.Professor, 工学研究科, 助教授 (70183861)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAHIRA Atsushi Kyoto Inst.of Technology, Engineering, Assoc.Professor, 工芸学部, 助教授 (90172387)
ADACHI Hirohiko Kyoto Univ., Engineering, Professor, エネルギー科学研究科, 教授 (60029105)
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| Project Period (FY) |
1996
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| Keywords | Si_3N_4 / SiC / TEM / EELS / molecular orbital |
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| Research Abstract |
Intergranular van-der Waals (vdW) force determines long range interaction of ceramics interfaces. It is effective over 10 hich is the order of the intergranular glassy film of Si_3N_4 ceramics. Such film is ubiquitous in Si_3N_4 ceramics but not in SiC.With recent improvement of high spatial resolution analytical electron microscopy, one can obtain electron energy-loss spectra (EELS) directly from the intergranular film. Since major features of the near edge structures of EELS (ELNES) can be ascribed to electronic dipole transitions from core orbitals to unoccupied band, accurate electronic calculations of the unoccupied band are necessary in order to interpret the experimental spectra.
In the present study, we made first principle molecular orbital calculations by discrete variational (DV) Xalpha method using model clusters composed of Si, N and O.There were tow objectives. 1) Interpretation of spectral features of ELNES obtained from the film in terms of the local chemical bonding. 2) Theoretical calculation of intergranular vdWforces across the film. Parallel to these theoretical works, experimental efforts to characterize the intergranular glassy film have been made mainly by means of high spatial resolution electron microscopy.
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