Growth behavior of water dispersed MgAl layered double hydroxide nanosheets

Abstract

Water-dispersed LDH nanosheets prepared using a microreactor could be used as building blocks for LDH-based functional materials. Elucidating the growth behavior of LDH nanosheets in aqueous phase helps to obtain its aqueous dispersion for further application in different fields. In this paper, a two stage growth behavior of LDH nanosheets was proposed which was based on the results of transmittance, viscosity, pH value, size distribution and morphological features of crystallites. In the first stage, MgAl-LDH nanosheet gel was dispersive in aqueous phase and the lateral size of nanosheets grew progressively, while in the second stage, the nanosheets stacked to build a three-dimensional network and the integrated plate-like structure of LDH was formed progressively. For both stages, curves of pH versus standing time implied the growth behavior fitted a first-order model. The results of both transmittance and viscosity indicated that the dispersion degree and nanosheet stacking rate were temperature dependent and independent of concentration. A diagram including three regions was made, which could be used to determine the state of the LDH nanosheets in aqueous phase and could also provide a theoretical basis for the practical application of LDH nanosheets.