Paper Title:
Iron Oxide and Oxide-Hydroxide Nanoparticles in Organic-Inorganic Matrices
  Abstract

Nanometric ferrihydrite, maghemite and magnetite particles formed within an organicinorganic hybrid matrix were obtained by the sol-gel process. In contrast to precipitation techniques, sol-gel process appears as suitable way to achieve size-controlled nanoscopic magnetic particles anchored in a hybrid structure. The hybrid matrix here reported, named di-ureasil, is composed of poly(oxyethylene) chains grafted to siloxane groups by means of urea cross-linkages. The formation of ferrihydrite particles was achieved incorporating iron nitrate during the sol-gel process, at low pH. The formation of maghemite takes place after the incorporation of a mixture of Fe3+ and Fe2+ ions and treatment with an ammonia solution, after the sol-gel process. Magnetite nanoparticles are formed after the incorporation of Fe2+ ions and treatment with ammonia at 80°C. The AC magnetic susceptibility shows thermal irreversibility with a blocking temperature TB≈13K and ≈25K depending on frequency for the ferrihydrite and maghemite particles, respectively. The magnetite nanoparticles are blocked at room temperature. Above the irreversibility the magnetization of ferrihydrite and maghemite follows a Langevin function modified with a linear term, as found in antiferromagnetic and ferrimagnetic particles.

  Info
Periodical
Materials Science Forum (Volumes 514-516)
Edited by
Paula Maria Vilarinho
Pages
142-146
DOI
10.4028/www.scientific.net/MSF.514-516.142
Citation
N. J. O. Silva, A. Millan, V. S. Amaral, F. Palacio, L. Fu, L. D. Carlos, V. de Zea Bermudez, "Iron Oxide and Oxide-Hydroxide Nanoparticles in Organic-Inorganic Matrices", Materials Science Forum, Vols. 514-516, pp. 142-146, 2006
Online since
May 2006
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$32.00
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