1994 Fiscal Year Final Research Report Summary
Preparation of Long Alumina Whiskers
| Project/Area Number |
04555184
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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 |
無機工業化学・無機材料工学
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
OKADA Kiyoshi Tokyo Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (80114859)
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| Co-Investigator(Kenkyū-buntansha) |
TARUTA Seiichi Shinshu University, Faculty of Engineering, Lecturer, 工学部, 講師 (00217209)
HAYASHI Shigeo Tokyo Institute of Technology, Faculty of Engineering, Associate, 工学部, 助手 (20218572)
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| Project Period (FY) |
1992 – 1994
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| Keywords | Alumina / Whisker / Aluminum fluoride / Vapor reaction / Mechanical property |
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| Research Abstract |
Alumina whiskers were synthesized by chemical vapor reaction of alumium fluoride hydrolyzing at high temperatures. Synthesis was performed with changing important factors such as the species and flow rate of sarrier gas, partial gas pressure of H_2O,and temperature and time of reaction. When one step synthetic method to sublimate aluminum fluoride and deposit alumina whiskers on a substrate, the whiskers can be grown up to around 20 mm in length at reaction temperature of 1200ﾟC.The whiskers grew from wall to center of the reaction tube perpendicular to the flow direction of the carrier gas.Since droplet like precipitate was found on the tip of the whiskers, the whiskers were considered to grow by the vapor-liquid-solid (VLS) mechanism.The droplet contained potassium and sodium elements as impurities and they formed melt at high temperature.
Tensile strength of the whiskers was measured by the Iwanaga et al. (1992)method and present study's method. The strength showed apparent dependence for the cross section area of the whiskers and was several GPa at cross section area of 10 mum^2. However, the present values were 10 to 10^2 lower than those reported by Levitt(1966). The present whiskers were found to contain some content of fluorine by XPS chemical analysis and was considered to be the main cause for low strength. Therefore, synthesis of whiskers under further higher reaction temperature was examined using two step synthetic method to avoid incorporation of fluorine in the whiskers. Whiskers were obtained by this method when adding iron metal as an impurity and using mullite ceramics as a substrate. However, the whiskers obtained were shorter in length and lower in yield than the former synthetic method and it was necessary to find further optimum experimental conditions for the second synthetic method.
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