1987 Fiscal Year Final Research Report Summary
Application of REDG Effect to Improve Fracture Toughness and Machinability of Ceramics
| Project/Area Number |
61460060
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Applied materials
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HYODO Shin-ichi The Faculty of Engineering, The University of Tokyo, 工学部, 教授 (30010713)
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| Co-Investigator(Kenkyū-buntansha) |
MAEDA Koji The Faculty of Fngineering, The University of Tokyo (BABA,Hiroshi), 工学部, 講師 (10107443)
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| Project Period (FY) |
1986 – 1987
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| Keywords | Ceramics / Fracture toughness / REDG effect / SiC / GaAs / Deslocation glide / Radiation / 脆性一延性遷移 |
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| Research Abstract |
In order to study the feasibility of increase in the fracture toughnes and machinability of SiC-based ceramics by controlling the mobility of dislocations throuth the REDG (radiation enhanced dislocation glide) effect, an effect observed in many covalent semiconductors, the following experiments have been performed: (1) To determine the intrinsic mobility of dislocations in SiC crystals and to clarify its relation to the mechanical strength, micro-indentation tests, high-temperature compression tests and transmission electron microscopic observations of deformation-induced defects have been carried out for 6H SiC single crystals over a temperature range covering the ductile-brittle transition (DBT). (2) Klc enhancement due to the REDG effect was studied in GaAs, the crystals for which the effect has been most intensively studied. (3) Whether the REDG effect is present in SiC was also examined. These experiments revealed the following points: (1) Basal slips in 6H SiC become active at temperatures (<1000゜C) much lower than so far believed. (2) The DBT taking place around 800゜C in SiC sinters can be interpreted in terms of the dislocation mechanism. (3) The dislocation glides are controlled by the Peierls mechanism and have an activation energy of 3.4eV. (4) The stacking fault (SF) energy is so small that 6H SiC can be Deformed at low temperatures (RT[[800゜C) by forming many SFs. (5) Light illumination suppresses the growth of indentation-induced cracks on n-GaAs, causing an increase in K_<ic>by a factor of two. (6) This crack-suppression effect does not operate without sufficient dislocation mobility. (7) Crack suppression by electron irradiation, presumably due to the REDG effect, was observed in a p-type 6H SiC, although not found in n-type crystals. In view of the present results, improvement of fracture toughness in SiC-based ceramics seems possible if the stress condition and the electric properties of the crystal are appropriately controlled.
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Research Products
(14 results)
