2000 Fiscal Year Final Research Report Summary
Study of boundary structure and toughening mechanism of ceramic bicrystal and polycrystal
| Project/Area Number |
10450244
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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 | KYUSHU UNIVERSITY |
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Principal Investigator |
ABE Hiroshi KYUSHU UNIVERSITY, Faculty of Engineering Sciences, Prof., 大学院・総合理工学研究院, 教授 (10294977)
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| Co-Investigator(Kenkyū-buntansha) |
KOGA Kazuko KYUSHU UNIVERSITY, Faculty of Engineering Sciences, Research Ass., 大学院・総合理工学研究院, 助手 (00315144)
YOSHIDA Fuyuki KYUSHU UNIVERSITY, Faculty of Engineering Sciences, Asst. Prof., 大学院・総合理工学研究院, 講師 (30243968)
NAKASHIMA Hideharu KYUSHU UNIVERSITY, Faculty of Engineering Sciences, Ass. Prof., 大学院・総合理工学研究院, 助教授 (80180280)
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| Project Period (FY) |
1998 – 2000
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| Keywords | microstructure / grain boundary / bicrystal / single crystal / sintered SiC / alumina / fracture toughness / fracture surface energy |
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| Research Abstract |
1 Mechanical properties of single crystal and sintered SiC with different additives and different microstructures were evaluated. The results are summarizes as follows :
(1) The order of K_<IC> is sintered SiC with Al_2O_3 additives (K_<IC>=6MPa・m^<1/2>)>sintered SiC with B and C additives>single crystals (K_<IC>=2MPa・m^<1/2>).
(2) The properties of single crystals depend on the crystal orientation, while little difference of properties is observed between 4H and 6H SiC.
(3) High fracture toughness of Al_2O_3 containing SiC resulted from crack deflection and branching at the boundaries of elongated grains. It is to be emphasized that high K_<IC> partially results at the sacrifice of a local damage when stress is applied by indentation. Similar results were obtained for Al_2O_3 ceramics.
(4) Slightly higher fracture toughness of sintered SiC with B and C additives, in comparison with single crystals, is caused by crack deflection which is observed even in a transgranular fracture due to the different orientation of cleavage planes of each grain.
2 Study of bicrystals and microstructure designing
Results of the study of 6H-SiC bicrystals show that there are remarkable differences of properties between crystals of different orientations. The properties were resistance to crack initiation and propagation, resistance to chemical etching and damage during machining and polishing. It was concluded that the desired properties and environments where materials are used have to be taken into consideration in designing microstructures of ceramics,
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