Physicochemical study of nanocapsular layered double hydroxides evolution

A sol - gel method for the synthesis of MgAl layered double hydroxides is presented. The sols thus obtained were submitted to several hydrothermal treatments, in presence or absence of water, in order to examine the thermal evolution of specific physicochemical properties, such as morphology, crystal size, basicity, and textural properties. The morphological evolution was followed by transmission electron microscopy (TEM) and scanning electron microscopy techniques. TEM analyses revealed unique nanocapsular morphology; the nanocapsules grow with increasing hydrothermal treatment time and aggregate in the presence of water. X-ray diffraction confirms the expected increase in crystal size. The nitrogen adsorption - desorption surface analysis (Brunauer - Emmett - Teller) of the calcined solids indicates that surface areas range from 251 to 289 m² g^-1. Furthermore, CO₂ thermoprogrammed desorption and Fourier-transform infrared analyses using CDC1₃ as a probe molecule indicate that basic strength is inversely proportional to crystal size.