1993 Fiscal Year Final Research Report Summary
Development of Ceramic Based Nanocomposites with High Toughness and Strength at High Temperatures
| Project/Area Number |
03555157
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| Research Category |
Grant-in-Aid for Developmental Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | Osaka University |
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Principal Investigator |
NIIHARA Koichi Osaka University, ISIR,Professor, 産業科学研究所, 教授 (40005939)
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| Co-Investigator(Kenkyū-buntansha) |
SASAKI Hiroshi Cement Research Center, Mitsubishi Materials Co.Ltd.Principal Researcher, セメント研究所, 副部長
SEKINO Tohoru Osaka University, Research Associate, 産業科学研究所, 助手 (20226658)
NAKAHIRA Atsushi Osaka University, ISIR,Research Associate, 産業科学研究所, 助手 (90172387)
TANAKA Isao Kyoto University, Faculty of Engineering, Research Associte, 工学部, 助手 (70183861)
UEDA Satoru Osaka University, ISIR,Assistant Professor, 産業科学研究所, 講師 (20029870)
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| Project Period (FY) |
1991 – 1993
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| Keywords | Ceramics / Composite / Nanocomposite / Mechanical properties / Al_2O_3 / Si_3N_4 / Nanostructure / Micro-nano hybrid |
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| Research Abstract |
The nanocomposites, in which nano-sized second phases were dispersed within matrix grains and at grain boundaries, were developed in the composite systems such as Al_2O_3/SiC,MgO/SiC,Si_3N_4/SiC and Sialon/SiC by usual sintering techniques. The TEM/SEM observations and mechanical properties tests on these nanocomposites gave the following conclusions. 1) Mechanicalproperties including fracture strength was 2 to 4 times improved by this nanocomposite technology. 2) High-temperature mechanical properties as well as thermal shock fracture resistance was significantly improved by nano-sized particle dispersions. In special, the creep resistance of Al_2O_3 and Si_3N_4 was 1000 to 10000 times improved mainly by intergranular nano-sized dispersions. 3) These abnormal properties improvement was attributed to the strengthening of matrix grains by intragranular nano-sized dispersions and the atomic scale structure control by intergranular nano-sized dispersions. 4) Finally, the low pressure less
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sintering proccess to make complex-shaped machine parts from these nanocomposite materials were successfully developed.
It was clear, however, that only nanocomposite technology could not break thorugh the brittleness of ceramics. Thus, the micro-nano hybrid concept, that is, the concept to improve the fracture toughness of nanocomposites by further-reinforcing them with micro-sized second phases, was applied to the Sialon/SiC nanocomposite system. The long carbon fiber was selected as the micro-sized reinforcement. The results are as follows : 5) The super tough and strong ceramics with the strength of over 1000 MPa at 1500ﾟC and the toughness of 20 to 25 MPam^<1/2> were developed by reinforcing the Sialon/3vol% SiC nanocomposites with the carbonlong fiber. 6) Some parts of gas turbine engine could be successfully fabricated from this super-ceramic material. In adition to these results, following experimental results were also obtained. 7) The Si_3N_4/SiC and Al_2O_3/SiC nanocomposites exhibited essentiallyt much better properties for cutting tools than the monolithic materials. 8) The toughening strenghening mechanisms by intra/intergranular nano-sized dispersions were made clear for the over-tens composite systems. Less
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