| Project/Area Number |
10555304
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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 | 展開研究 |
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| Research Field |
工業物理化学
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| Research Institution | Osaka University |
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Principal Investigator |
ADACHI Gin-ya Materials Chemistry, Osaka University Professor, 大学院・工学研究科, 教授 (60029080)
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| Co-Investigator(Kenkyū-buntansha) |
HIRASHIMA Yoshiyuki Shin Nippon Metal & Chemical Co., LTD., Director, 研究員・顧問
MASUI Toshiyuki Materials Chemistry, Osaka University Assistant Professor, 大学院・工学研究科, 助手 (00304006)
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| Project Period (FY) |
1998 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥12,700,000 (Direct Cost: ¥12,700,000)
Fiscal Year 1999: ¥5,400,000 (Direct Cost: ¥5,400,000)
Fiscal Year 1998: ¥7,300,000 (Direct Cost: ¥7,300,000)
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| Keywords | Rare earth oxides / Automotive exhaust catalysts / Oxygen storage capacity / Zirconia / Rare earth oxalate / Pyrochlore / Hydrazine / Chemical vapor transport / 希土類シュウ塩酸 / マイクロエマルション / 微粒子 / 逆ミセル |
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| Research Abstract |
In this work we aimed development of rare-earth based oxides of high thermal stability and high catalytic activity. Especially we focused on ceria-zirconia mixed oxides which were applied as promoters in the automotive exhaust three-way catalysts.
Nanosize Ceria and ceria-zirconia ultrafine particles prepared using a reaction within reversed micelles were characterized by HREM. The catalytic activities of the ceria-zirconia ultrafine particles supported on γ-alumina powders were higher than those given by the conventional catalysts prepared by the co-precipitation method, even after the heat treatment at 1273 K for 5 h in air.
Ceria-zirconia solid solutions were also prepared by thermal decomposition of cerium zirconyl oxalate in an argon flow at 1273 K followed by oxidation at 673-873 K in air. The reduction behavior of the obtained powders was investigated and compared with the samples of high redox activity prepared by the conventional method. The ceria-zirconia samples prepared from the oxalate showed better reduction behavior, in spite of their very low surface areas. The reason for the behavior was attributed to both the appearance of a cubic phase with a different oxygen arrangement and the reduction by carbon formed in the sample preparation process.
Surface modification of the ceria-zirconia solid solutions was carried out using formation and transport of volatile vapor complexes such as AlClィイD23ィエD2-CeClィイD23ィエD2 and AlClィイD23ィエD2-ZrClィイD24ィエD2, This process was named as "chemical filing." Reduction temperature of the sample after the chemical filing was lower than that of the fresh sample, and further decreased by a reduction/reoxidation cycle. The redox property of the chemically filed sample was maintained even after the redox cycles at high temperatures, indicating its durability compared to the solid solution prepared by a conventional procedure.
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