Abstract
Magnetic nanocomposites containing magnetite (Fe 3O 4) 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 Fe 3O 4 with a spinel-type structure was formed in a noncrystalline silicate matrix. The average crystallite size of the Fe 3O 4 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, Fe 3O 4 was reduced to wüstite (Fe 1 -xO) and finally crystallized into iron metal (α-Fe) and ferrous silicate (Fe 2SiO 4).
Original language | English |
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Pages (from-to) | 1156-1161 |
Number of pages | 6 |
Journal | Materials Chemistry and Physics |
Volume | 136 |
Issue number | 2-3 |
DOIs | |
Publication status | Published - Oct 15 2012 |
Keywords
- Amorphous materials
- Heat treatment
- Magnetic materials
- Magnetometer (for magnetic field, susceptibility, magnetic moment, magnetisation measurements)
- Nanostructures
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics