Nanowires of iron oxides embedded in SiO2 templates

N. A. FELLENZ; S. G. MARCHETTI; F. R. SIVES; S. J. STEWART; R. C. MERCADER

HYPERFINE INTERACTIONS

Springer Netherlands

Año: 2006 vol. 170 p. 75 - 82

0304-3843

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 size-  distribution of magnetic particles. It is mainly made up of fine particles that display a  superparamagnetic relaxation at room temperature and get blocked at ¡Ö42 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.