| Project/Area Number |
16560588
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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 |
Inorganic materials/Physical properties
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
AKATSU Takashi Tokyo Institute of Technology, Materials and Structures Laboratory, Associate Professor, 応用セラミックス研究所, 講師 (40231807)
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| Co-Investigator(Kenkyū-buntansha) |
WAKAI Fumihiro Tokyo Institute of Technology, Materials and Structures Laboratory, Professor, 応用セラミックス研究所, 教授 (30293062)
SHINODA Yutaka Tokyo Institute of Technology, Materials and Structures Laboraty, Research Associate, 応用セラミックス研究所, 助手 (30323843)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 2005: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2004: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Structural・Functional Materials / Ceramics / Nano Materials / ナノ多結晶体 / ナノインデンテーション / 変形 / 破壊 |
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| Research Abstract |
The aim of this research work is to investigate the mechanical properties of nano-structured ceramics which show superior mechanical performance. We obtained important results as follows,
1. The hardness of cubic zirconia polycrystals with average grain size of 100nm was observed to be the same as that of cubic zirconia single crystals. This means that there is no grain size dependence in the hardness of cubic zirconia, which is quite different from metal materials.
2. In tetragonal zirconia, extremely high hardness was found in polycrystals with the average grain size of 60nm, which was almost two times larger than the hardness observed in ordinal tetragonal zirconia with average grain size of submicron. The high hardness is attributed to the inhibition of stress-induced transformation from tetragonal to monoclinic phase, which was experimentally confirmed through laser raman spectra.
3. In monoclinic zirconia, the hardness of polycrystals with average grain size of 60nm was found to be
… More
1.5 times larger than that of polycrystals with average grain size of submicron. The plastic deformation due to twinning seems to occur hardly in polycrystals when the average grain size becomes smaller than 100nm.
4. In alumina, it was rather difficult to obtain polycrystals with average grain size smaller than 100nm, because the rate of grain growth in alumina was very fast in comparison with zirconia. Alpha alumina polycrystals with average grain size of 600nm was fabricated two-step sintering by utilizing hot-pressing and HIP technique. The hardness of the polycrystals was observed to be the same as that of alpha alumina single crystals. This means that there is no grain size dependence in the hardness of alpha alumina.
5. Extremely high hardness was found in cubic magnesia polycrystals with the average grain size of 100nm, which was almost two times larger than the hardness observed in ordinal magnesia with average grain size of the order of micron. This seems to be due to the difficulty of dislocation slip and/or glide in very small grains of the order of 100nm.
6. Indentation size effect of hardness, i.e. hardness increases with the decrease in indentation depth, was, for the first time, found in ceramic materials although ISE has been predicted to be difficult to observe for hard materials according to the theory of the strain gradient plasticity. Less
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