CENTRO DE INVESTIGACION Y DESARROLLO EN CIENCIAS APLICADAS "DR. JORGE J. RONCO"
Unidad Ejecutora - UE
congresos y reuniones científicas
NANOWIRES OF IRON OXIDES EMBEDDED IN SIO2 TEMPLATES
N. A. FELLENZ, J. F. BENGOA, S. G. MARCHETTI, F. R. SIVES, S. J. STEWART AND R. C. MERCADER
Garden City, New York, Estados Unidos
Simposio; 4th Nassau Mössbauer Symposium at Nassau Community College; 2006
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 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 ≈42 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 110 K; in addition, there is a minor Fe(III) fraction that remains paramagnetic down to 4.2 K.