Nanowires of iron oxides embedded in SiO2 templates
| Autor: | S. J. Stewart, Nicolás Antonio Fellenz, Roberto C. Mercader, Jose Fernando Bengoa, Sergio Gustavo Marchetti, F. R. Sives |
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| Rok vydání: | 2006 |
| Předmět: |
Nuclear and High Energy Physics
Materials science Relaxation (NMR) Maghemite Nanotechnology engineering.material Condensed Matter Physics Atomic and Molecular Physics and Optics Charge ordering Paramagnetism chemistry.chemical_compound chemistry Chemical engineering engineering Magnetic nanoparticles Physical and Theoretical Chemistry Mesoporous material Incipient wetness impregnation Magnetite |
| Zdroj: | Hyperfine Interactions. 170:75-82 |
| ISSN: | 1572-9540 0304-3843 |
| DOI: | 10.1007/s10751-006-9469-0 |
| Popis: | To attain the complete filling of the channels of MCM-41 with magnetite and maghemite, we have tried out an alternative method to the incipient wetness impregnation. The mesoporous material was instilled with a Fe-carrying organic salt after subjecting the matrix to a silylation treatment. Thus, a solid of 7.7 wt.% iron-loaded MCM-41 was obtained. Different subsequent thermal treatments were used to produce γ-Fe2O3 or Fe3O4. The Mossbauer and magnetic results show that after this method, the as-prepared composite displays a size-distribution of magnetic particles. It is mainly made up of fine particles that display a super paramagnetic relaxation at room temperature and get blocked at ≈2 K for the AC susceptibility time-scale measurements both for γ-Fe2O3 and Fe3O4 particles. For both samples, about 24% of larger iron-containing phases are magnetically blocked at room temperature. For the Fe3O4 particles, this fraction undergoes the Verwey transition at about 110K; in addition, there is a minor Fe(III) fraction that remains paramagnetic down to 4.2 K. |
| Databáze: | OpenAIRE |
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