CINDECA   05422
CENTRO DE INVESTIGACION Y DESARROLLO EN CIENCIAS APLICADAS "DR. JORGE J. RONCO"
Unidad Ejecutora - UE
artículos
Título:
NANOWIRES OF IRON OXIDES EMBEDDED IN SiO2 TEMPLATES
Autor/es:
N. A. FELLENZ, J. F. BENGOA, S. G. MARCHETTI, F. R. SIVES, S. J. STEWART AND R. C. MERCADER.
Revista:
HYPERFINE INTERACTIONS
Editorial:
Springer
Referencias:
Año: 2006 vol. 170 p. 75 - 82
ISSN:
0304-3843
Resumen:
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 +-Fe2O3 or Fe3O4. The Mössbauer and
magnetic results show that after this method, the as-prepared composite displays a sizedistribution
of magnetic particles. It is mainly made up of fine particles that display a
superparamagnetic relaxation at room temperature and get blocked at ≈42 K for the AC
susceptibility time-scale measurements both for +-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
110 K; in addition, there is a minor Fe (III) fraction that remains paramagnetic down to 4.2 K.+-Fe2O3 or Fe3O4. The Mössbauer and
magnetic results show that after this method, the as-prepared composite displays a sizedistribution
of magnetic particles. It is mainly made up of fine particles that display a
superparamagnetic relaxation at room temperature and get blocked at ≈42 K for the AC
susceptibility time-scale measurements both for +-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
110 K; in addition, there is a minor Fe (III) fraction that remains paramagnetic down to 4.2 K.≈42 K for the AC
susceptibility time-scale measurements both for +-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
110 K; in addition, there is a minor Fe (III) fraction that remains paramagnetic down to 4.2 K.+-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
110 K; in addition, there is a minor Fe (III) fraction that remains paramagnetic down to 4.2 K.3O4 particles, this fraction undergoes the Verwey transition at about
110 K; in addition, there is a minor Fe (III) fraction that remains paramagnetic down to 4.2 K.