Synthesis and Characterization of Mesostructured Crystalline-Framework CeO_2 and CeO_2-ZrO_2 Composite

Mesostuctured CeO_2 and CeO_2-ZrO_2 composite were synthesized via sol-gel method using cerium acetate and zirconium acetate as inorganic species,block copolymer P123 as surfactant,respec- tively.The obtained samples were characterized by XRD,N_2 adsorption-desorption,TEM,HRTEM, and SAED.Results show that the mesostrutured CeO_2 possesses crystalline framework with the average pore size of ca.10nm.In particular,it's revealed that the inorganic framework consists of highly oriented nanocrystals with the preferential orientation parallel to the channel arrays.In situ TEM observation equipped with the heating holder demonstrates that the mesostructured CeO_2 maintains perfect pore in- tegrity up to 800℃due to the confined growth tendency of oriented grains.Mesostructured CeO_2-ZrO_2 composite remains the similar framework structure when ZrO_2 molar ratio is less than 30%,however,it appears to transform to random oriented polycrystalline mesostructure when ZrO_2 molar ratio is higher than 30%.