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Microstructural Evolution of Nanocrystalline Magnetite Synthesized by Electrocoagulation

Published online by Cambridge University Press:  03 March 2011

Ying-Chieh Weng ,
I.A. Rusakova ,
Andrei Baikalov ,
J.W. Chen  and
Nae-Lih Wu
Ying-Chieh Weng
Affiliation:
Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan, Republic of China
I.A. Rusakova
Affiliation:
Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5932
Andrei Baikalov
Affiliation:
Texas Center for Superconductivity and Advanced Materials, University of Houston, Houston, Texas 77204-5932
J.W. Chen
Affiliation:
Department of Physics, National Taiwan University, Taipei 106, Taiwan, Republic of China
Nae-Lih Wu*
Affiliation:
Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan, Republic of China
*
a)Address all correspondence to this author. e-mail: [email protected]
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Abstract

Nanocrystalline magnetite powders were synthesized by an electrocoagulation technique, in which an electric current was passed across two plate electrodes of carbon steel immersed in NaCl(aq) electrolyte, and the microstructure of the oxide powder was found to evolve in roughly three stages. The first stage involves formation and growth of severely defective colloidal crystallites. This is followed by agglomeration among the oxide crystallites to form mesoporous agglomerates containing predominantly inter-crystallite pores, and the average crystallite size was found to reach a plateau. Finally, coarsening of the crystallites within the agglomerates leads to another rapid increase in crystallite size and reduction in pore opening. The synthesized powders typically showed a saturation magnetization of ∼75 emu/g and a coercivity Hc of ∼118 Oe. A mechanism involving competition between nucleation and growth of free colloids and coarsening of the skeletal framework was proposed to explain the temporary level-off in crystallite size during the synthesis.

Keywords

ColloidalElectrochemical synthesisMagnetic
Type
Articles
Information
Journal of Materials Research , Volume 20 , Issue 1 , January 2005 , pp. 75 - 80
Copyright
Copyright © Materials Research Society 2004

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