11-03
W.N. Budhysutanto, F.J. van den Bruele, B.D. Rossenaar, D. van
Agterveld, W.J.P. van Enckevort, H.J.M. Kramer,
A unique growth mechanism of donut-shaped Mg-Al layered
double hydroxides crystals revealed by AFM and STEM-EDX,
Journal of Crystal Growth 318 (2011) 110-116
Abstract
Donut-like crystals of Mg-Al layered double hydroxides (LDH) are synthesized
using a hydrothermal method with microwave heating. This morphology provides
enlargement of the specific surface area of the {h k 0} faces, needed for
adsorption application. The growth mechanism for donut-shaped crystals is
proposed on the basis of AFM and STEM-EDX images. The nucleation of Mg-Al LDH
starts on the amorphous surface of spherical MgO particles, which have a much
lower solubility compared to the aluminum trihydroxides at the synthesis pH
(similar to 11). The outgrowing nucleus provides re-entrant corners on both
sides. These are preferential sites for the addition of new growth units,
allowing lateral growth of the LDH crystal encircling the MgO particles. The
dissolving MgO provides the supersaturation needed for growth and once it is
depleted, a donut-like structure remains. (c) 2010 Elsevier B.V. All rights
reserved.