Stability and particle size control of self-assembled cadmium–aluminum layered double hydroxide
We use the reaction–diffusion framework (RDF) to study the kinetics of formation of hierarchical microstructures of cadmium–aluminum layered double hydroxide (CdAlCl LDH), its particle size distribution, and its polymorphic transformation to brucite-like cadmium hydroxide (β-Cd(OH)2). The system exhibits the evolution of two successive bands separated by a sharp interface, a leading one that constitutes the yellow CdAlCl LDH followed by the white brucite band. We show that by using the RDF we can manipulate the size distribution of the particles within the LDH band along the tubular reactor. The spatiotemporal dynamics of these bands provides a simple means to study the kinetics of formation of the LDH and its polymorphic transformation as a function of the cationic ratio, hence predicting its stability. Consequently, the relative rate constants and the Avrami exponents are calculated and are shown to exhibit a linear correlation with the cationic ratio. The collapse of the LDH microstructures into nano-spheroids of β-Cd(OH)2 is visualized using scanning electron microscopy at the LDH–brucite interface.