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Superparamagnetic particles in ZSM-5–type ferrisilicates

Published online by Cambridge University Press:  31 January 2011

A. López
Affiliation:
Instituto de Ciencia de Materiales de Aragón (Universidad de Zaragoza-Consejo Superior de Investigaciones Cientificas), 50015 Zaragoza, Spain
F. J. Lázaro
Affiliation:
Instituto de Ciencia de Materiales de Aragón (Universidad de Zaragoza-Consejo Superior de Investigaciones Cientificas), 50015 Zaragoza, Spain
J. L. García-Palacios*
Affiliation:
Instituto de Ciencia de Materiales de Aragón (Universidad de Zaragoza-Consejo Superior de Investigaciones Cientificas), 50015 Zaragoza, Spain
A. Larrea
Affiliation:
Instituto de Ciencia de Materiales de Aragón (Universidad de Zaragoza-Consejo Superior de Investigaciones Cientificas), 50015 Zaragoza, Spain
Q. A. Pankhurst
Affiliation:
Department of Physics and Astronomy, University College London, London WC1E 6BT, United Kingdom
C. Martínez
Affiliation:
Instituto de Tecnología Química (Consejo Superior de Investigaciones Científicas), 46022 Valencia, Spain
A. Corma
Affiliation:
Instituto de Tecnología Química (Consejo Superior de Investigaciones Científicas), 46022 Valencia, Spain
*
a)Author to whom correspondence should be addressed.
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Abstract

As-synthesized, low iron content, ferrisilicates of ZSM-5-type contain well-separated Fe(III) ions in a tetrahedral environment and display paramagnetic behavior. After hydrothermal treatment, the iron ions are partially extracted from the framework, generating nanosize iron oxide or oxyhydroxide ferrimagnetic particles. This process has been studied by transmission electron microscopy (TEM), Mössbauer spectroscopy, magnetic ac susceptibility (χac), and field dependent magnetization, on samples containing up to 6.7 wt.% Fe. The experiments evidence the growth of nonaggregated particles, with a typical size around 3 nm, presumably located at the surface of the ferrisilicate crystallites. From a thorough granulometric analysis involving TEM and χac data, it is concluded that, in the range from 1.5 to 4.6 wt.% Fe, the particle size distributions are significantly independent of the iron content.

Type
Articles
Copyright
Copyright © Materials Research Society 1997

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References

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