Synthesis and characterization of layered double hydroxides with different cations (Mg, Co, Ni, Al), decomposition and reformation of mixed metal oxides to layered structures

摘要

Three layered double hydroxides (LDH) [Mg1?xAlx(OH)2]x+(Am?)x/m]·nH2O and [MII 1?xMIII x (OH)2]x+(Am?)x/m]·nH2O (MII — Mg, Co, Ni; MIII — Al; A — CO3 2?) were successfully synthesized by the low supersaturation method. The as-synthesized LDH samples were thermally decomposed and the derived mixed metal oxides reformed back to layered structures in water and magnesium nitrate media at different temperatures. All synthesized samples were characterized by X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis, X-ray fluorescence (XRF) analysis and scanning electron microscopy (SEM). The results of XRD and XRF analyses showed that single-phase layered double hydroxides were formed during synthesis and reformation. It was demonstrated, that a partially substituted by cobalt and nickel LDH samples also show memory effect. The crystallite size of regenerated LDH depends on the regeneration media, temperature and chemical composition. The LDH samples after regeneration consist of large particles with sharp edges along with a large amount of smaller particles