Microtextural properties of layered double hydroxides:: a theoretical and structural model

In this paper, a theoretical method to estimate the textural properties of layered double hydroxides (LDHs) of the type [M1-x2+Mx3+(OH)(2)][A(x/n)(n-)] is presented. The theoretical calculations are based on the structure and composition of the LDH, using geometrical models of an LDH crystallite and the intercalating anion. Several examples of the application of this model to LDHs and pillared LDHs are shown. The estimated properties include the interpillar distances, the interlamellar and external areas, the interlamellar free volume, the fraction of external anions and the apparent and true density of the LDH. For well crystallized LDH samples, agreement between the estimated and the experimental results is found, for poorly crystalline samples, a correlation between the degree of crystallite agglomeration and the experimental areas is proposed. (C) 2003 Elsevier Inc. All rights reserved.