1989 Fiscal Year Final Research Report Summary
Creep and Creep Fracture of Oxide Ceramics
| Project/Area Number |
63550581
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
無機工業化学
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
OKAMOTO Yasunori Kyoto Institute of Technology, Department of Chemistry and Materials Technology, Associate Professor, 工芸学部, 助教授 (50101259)
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| Co-Investigator(Kenkyū-buntansha) |
HAYASHI Kunio Kyoto Institute of Technology, Department of Chemistry and Materials Technology,, 工芸学部, 助教授 (30027817)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Ceramics / Creep / Fracture / Deformation / Zirconia / Glass ceramics / Mullite / Diffusion |
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| Research Abstract |
The effects of microstructures (grain size, second phase, etc) on high temperature deformation such as creep and creep fracture were studied for some oxide ceramics; magnesias with and without an intergranular glass phase, a fine-grained, yttria stabilized tetragonal zircoenia exhibiting superplasticity, a beta-spodumene glass ceramic and fine-grained, single phase mullite (3Al_2O_3・2SiO_2). Glass phases in the magnesia and the glass ceramic enhanced the creep strain rates by pressure solution. However, they were the origins of cavitation, resulting in microcracking at grain boundaries. Modern ceramics often have very fine microstructures without apparent glassy phases, thus show sometimes high ductility (superplasticity in some cases) at high temperatures, leading the application to plastic forming. On the other hand, these ceramics show limited resistance to deformation in high-temperature structural application. The mullite was shown to have high creep resistance in spite of its fine grain size (1.5 mum) and to have high strength in creep fracture. The increase in grain size of the mullite led to cavitation at grain boundaries and thus lowered the creep fracture stress, as observed in Y-TZP. The criterion for initiation of cavitation was difficult to determine, which is the next step of this study.
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