Selectivity of Crystal Growth Direction and Control of Particle Size in Layered Double Hydroxides

Mg-Al layered double hydroxides (LDH) have been synthesized at high supersaturation using a new method developed in our laboratory. The influence of aging temperature and aging time on the crystal structure, selectivity of crystal growth in different directions and the particle size of LDH has been investigated. It has been shown that with increasing aging time at the same temperature, the crystallinity of the LDH increased and the particle size became larger. The same effect was observed when samples were aged at increasing temperature for a fixed period, but the particle size of the LDH increased dramatically with increasing aging temperature. The size of the crystallites in the a direction was larger than that in the c direction under all experimental conditions. This is the result of the greater rate of crystal growth in the a direction than that in the c direction. On the basis of the variation in particle size of LDH with aging time and aging temperature, an optimum aging condition was determined and LDH nanomaterials with a narrow particle size distribution were obtained.