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Fe-Al2O3 Nanocomposite: Synthesis and Magnetic Properties

Published online by Cambridge University Press:  21 February 2011

A. Santos ,
W. A. A. Macedo ,
J. D. Ardisson ,
A. D. C. Viegas  and
J. E. Schmidt
A. Santos
Affiliation:
Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear - CDTN, CNEN / MCT, 0123-970 Belo Horizonte, Brazil.
W. A. A. Macedo
Affiliation:
Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear - CDTN, CNEN / MCT, 0123-970 Belo Horizonte, Brazil.
J. D. Ardisson
Affiliation:
Laboratório de Física Aplicada, Centro de Desenvolvimento da Tecnologia Nuclear - CDTN, CNEN / MCT, 0123-970 Belo Horizonte, Brazil.
A. D. C. Viegas
Affiliation:
Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501 Porto Alegre, Brazil.
J. E. Schmidt
Affiliation:
Instituto de Física, Universidade Federal do Rio Grande do Sul, 91501 Porto Alegre, Brazil.
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Abstract

We have investigated the synthesis and the structural and magnetic properties of Fe nanoparticles embedded in Al2O3 matrix, a granular nanocomposite prepared by sol-gel processing. Samples with volumetric Fe content ranging from 20 to 62% were obtained starting from Al nitrate and Fe sulfate as precursors and the preparation method results initially in a mixture of Fe- and Al oxides. The conversion of Fe oxides into metallic Fe was done by calcination at 800°C followed of reduction at 600°C for 2 hours, in H2 atmosphere. Our results indicated the following phases in the amorphous alumina matrix, after reduction: α-Fe, the main phase, α- and γ-Fe2O3, Fe3O4 and some interstitial Fe2+ and substitutional Fe3+ atoms in the Al2O3 lattice. For the investigated system, Fe reduction rate was very sensitive to the sample porosity and, with the applied method, we have obtained reductions of the Fe atoms into metallic Fe ranging from 45 to 68%, preserving the mean diameter of the oa-Fe nanoparticles between 55 and 80 nm. VSM measurements at room temperature resulted in coercivity between 450 and 630 Oe and saturation magnetization between 40 and 110 emu/g. Magneto-transport measurements in samples with 25% metallic Fe (and 51% total Fe) reveal ΔR/R close to 2% at room temperature.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 581: Symposium F – Nanophase & Nanocomposite Materials II , 1999 , 333
Copyright
Copyright © Materials Research Society 2000

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References

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