| Autor: |
Makoto Nakanishi, Yasunori Ikeda, Hideki Hashimoto, Tatsuo Fujii, Yoshihiro Kusano, Jun Takada |
| Rok vydání: |
2012 |
| Předmět: |
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| Zdroj: |
Materials Chemistry and Physics. 136:1156-1161 |
| ISSN: |
0254-0584 |
| Popis: |
Magnetic nanocomposites containing magnetite (Fe3O4) nanoparticles were prepared from iron oxide microtubules produced by Leptothrix ochracea, a species of water-habitant iron-oxidizing bacteria. The microtubules were mainly composed of Si-containing ferric hydroxide that shows a broad X-ray diffraction pattern similar to that of 2-line ferrihydrite. After moderate heat treatment in a reductive atmosphere above 325 °C, the ferric ions were partially reduced to a ferrous state, and nanocrystalline Fe3O4 with a spinel-type structure was formed in a noncrystalline silicate matrix. The average crystallite size of the Fe3O4 nanoparticles was estimated to be in the order of a few nanometers. The sample heat-treated at 500 °C exhibited considerable magnetization together with superparamagnetic behavior at room temperature, and super-spin-glass interaction occurred at low temperature. On further heat treatment above 530 °C, Fe3O4 was reduced to wustite (Fe1−xO) and finally crystallized into iron metal (α-Fe) and ferrous silicate (Fe2SiO4). |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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