2013 Fiscal Year Final Research Report
Crystal structural change of iron hydroxide by nanoparticulation
| Project/Area Number |
24740352
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| Research Category |
Grant-in-Aid for Young Scientists (B)
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| Allocation Type | Multi-year Fund |
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| Research Field |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | University of Tsukuba |
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Principal Investigator |
KYONO Atsushi 筑波大学, 生命環境系, 講師 (40375431)
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| Project Period (FY) |
2012-04-01 – 2014-03-31
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| Keywords | フェリハイドライト / ヘマタイト / ナノ鉱物 / PDF法 / 相転移 / 粒径サイズ |
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| Research Abstract |
Aggregation-induced phase transition of ferrihydrite to hematite was investigated using atomic pair distribution function (PDF) analysis of synchrotron x-ray total scattering experiments. The particle size of six-line ferrihydrite estimated from attenuation of the PDF increases from about 4 nm to above 10 nm. Then the ferrihydrite starts to transform to hematite. The ferrihydrite structure exhibits a strong tendency for the a lattice parameter to decrease with particle size. As the a lattice parameter decreases continuously, contractions of the six-membered rings occur. When a six-membered ring comprising three FeO6 octahedra and three FeO4 tetrahedra is contracted, the FeO4 tetrahedral coordination changes to octahedral. Consequently, the six-membered ring transforms to that comprising six FeO6 octahedra, which is the same configuration as that of hematite. This coordination change caused by the six-membered ring contraction induces the phase transition of ferrihydrite to hematite.
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