Issue 37, 2008

A kinetic study of the phase conversion of layered cobalt hydroxides

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

Supplementary files

Article information

Article type
Paper
Submitted
04 Jun 2008
Accepted
18 Jul 2008
First published
11 Aug 2008

J. Mater. Chem., 2008,18, 4450-4459

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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