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Iron and Iron-oxide on Silica Nanocomposites Prepared by the Sol-gel Method

Published online by Cambridge University Press:  31 January 2011

G. Ennas ,
M. F. Casula ,
G. Piccaluga ,
S. Solinas ,
M. P. Morales  and
C. J. Serna
G. Ennas*
Affiliation:
Dipartimento di Scienze Chimiche, Università di Cagliari, 09100 Cagliari, Italy
M. F. Casula
Affiliation:
Dipartimento di Scienze Chimiche, Università di Cagliari, 09100 Cagliari, Italy
G. Piccaluga
Affiliation:
Dipartimento di Scienze Chimiche, Università di Cagliari, 09100 Cagliari, Italy
S. Solinas
Affiliation:
Dipartimento di Scienze Chimiche, Università di Cagliari, 09100 Cagliari, Italy
M. P. Morales
Affiliation:
Instituto de Ciencia de Materiales de Madrid, CSIC, 28049, Cantoblanco, Madrid, Spain
C. J. Serna
Affiliation:
Instituto de Ciencia de Materiales de Madrid, CSIC, 28049, Cantoblanco, Madrid, Spain
*
a)Address all correspondence to this author. e-mail: ennas@unica.it
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Abstract

γ–Fe2O3/SiO2 and Fe/SiO2 nanocomposites, with a Fe/Si molar ratio of 0.25, were prepared by the sol-gel method starting from ethanolic solutions of tetraethoxysilane and iron (III) nitrate. After gelation the xerogels were oxidated or reduced. Samples were investigated by transmission electron microscopy, x-ray diffraction, differential scanning calorimetry, and thermogravimetry. Magnetic properties of the samples were investigated at room temperature (RT) and at 77 K. Nanometric particles supported in the silica matrix were obtained in all cases. Bigger particles (10 nm) were obtained in the case of Fe/SiO2 nanocomposites with respect to the γ–Fe2O3/SiO2 samples (5–8 nm). A slight effect of sol dilution on particle size was observed only in the case of γ–Fe2O3/SiO2 nanocomposites. A superparamagnetic behavior was shown at RT only by γ–Fe2O3/SiO2 nanocomposites. Iron-based composites exhibited coercivity values higher than 700 Oe at RT.

Type
Articles
Information
Journal of Materials Research , Volume 17 , Issue 3 , March 2002 , pp. 590 - 596
Copyright
Copyright © Materials Research Society 2002

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