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Issue 37, 2008
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A kinetic study of the phase conversion of layered cobalt hydroxides

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Abstract

A kinetic study of the phase conversions of three layered α-type cobalt hydroxides, two pink forms {Co(OH)1.4(NCO)0.6·0.6H2O, Co(OH)1.5(NO3)0.5·0.6H2O} and a green form {Co(OH)1.6Cl0.4·0.4H2O} to a brucite-like β-Co(OH)2 in the presence of NaOH have been investigated using time-resolved, in situ energy-dispersive X-ray diffraction (EDXRD) and time-resolved, in situ simultaneous small/wide angle X-ray scattering (SAXS/WAXS). The kinetic data have been modelled using the Avrami–Erofe'ev model. This analysis suggests that conversion of Co(OH)1.4(NCO)0.6·0.6H2O to β-Co(OH)2 follows a two-dimensional diffusion-controlled model while the conversion of Co(OH)1.6Cl0.4·0.4H2O to β-Co(OH)2 is best modelled by a phase-boundary-controlled process. The in situ SAXS/WAXS experiments on the conversion of Co(OH)1.6Cl0.4·0.4H2O to β-Co(OH)2 suggests that an Ostwald ripening model is obeyed during the final stages of the reaction. The transformation from Co(OH)1.5(NO3)0.5·0.6H2O to β-Co(OH)2 proceeds via an intermediate crystalline phase, which is thought to be an α-cobalt hydroxide with an expanded interlayer separation containing tetrahedrally coordinated Co2+.

Graphical abstract: A kinetic study of the phase conversion of layered cobalt hydroxides

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Publication details

The article was received on 04 Jun 2008, accepted on 18 Jul 2008 and first published on 11 Aug 2008


Article type: Paper
DOI: 10.1039/B809085H
Citation: J. Mater. Chem., 2008,18, 4450-4459
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    A kinetic study of the phase conversion of layered cobalt hydroxides

    Y. Du, K. M. Ok and D. O'Hare, J. Mater. Chem., 2008, 18, 4450
    DOI: 10.1039/B809085H

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