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Issue 12, 2002
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Monodispersed spindle-type goethite nanoparticles from FeIII solutions

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A new synthetic route for producing monodispersed and single crystal acicular goethite particles with small particle size and a high axial ratio adequate for use as a high density magnetic recording media precursor is reported. It essentially consists of the hydrolysis of alkaline FeIII suspensions in the presence of carbonate by a three-step procedure, the formation of ferrihydrite primary particles, the ferrihydrite dissolution and nucleation of goethite, and the growth of the goethite nuclei. Changing the temperature of heating during ageing achieved a separation of the two last stages. X-Ray diffraction, transmission electron microscopy, infrared spectroscopy and surface area data have been used to determine the mechanism responsible for the formation of goethite particles with controlled size and shape. The best conditions to prepare monodispersed goethite particles have been established. The results show that uniform goethite particles of (a) 60 nm length with an axial ratio of 6 and (b) 230 nm length with a high axial ratio of 10, can be obtained by using an [OH]/[Fe] molar ratio of 0.35 in the initial suspensions with carbonate or sodium hydroxide, respectively. The [OH]/[Fe] molar ratio determines the particle size and elongation by controlling the hydrolysis reaction rate, while the carbonate ions promote a constant [OH] in the solution, keeping the pH around 10 during the entire synthesis process. This procedure, associated with the appropriate temperature control, leads, under certain conditions, to highly homogeneous goethite particles with sizes smaller than those obtained using sodium hydroxide with the same [OH]/[Fe] ratio.

Graphical abstract: Monodispersed spindle-type goethite nanoparticles from FeIII solutions

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Publication details

The article was received on 23 Jul 2002, accepted on 02 Oct 2002 and first published on 29 Oct 2002

Article type: Paper
DOI: 10.1039/B207190H
Citation: J. Mater. Chem., 2002,12, 3649-3653
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    Monodispersed spindle-type goethite nanoparticles from FeIII solutions

    L. C. Varanda, M. P. Morales, M. Jafelicci, Jr and C. J. Serna, J. Mater. Chem., 2002, 12, 3649
    DOI: 10.1039/B207190H

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