Ion Exchange Synthesis Of Cerium Oxide

CeO2is a kind of industrial chemicals always aroused more attention for a long time as it was widely used in many fields including catalysis, polishing, ultraviolet absorbers, functional ceramics and luminous materials. Much studies indicate that the structure, size and morphology of nano-CcO2powders would seriously influence its performance, therefore controlling size and morphology of nano-CeO2powders is one of hot spots in investigation domain.In this thesis, nano-CeO2particles of various sizes and morphologies were prepared by ion exchange reaction route (direct precipitation and hydrothermal precipitation) through controlling reaction temperature, reaction time and concentration of precipitation agent. X-ray diffraction (XRD) was used to characterize their structure and phase. Field emission transmission electron microscopy (TEM) and field emission scanning electron microscopy (SEM) were used to characterize their sizes and morphologies. Thermo gravimetric analyzer and differential scanning calorimeter (TG/DSC) were used to study thermal decomposition of precursors.1. Precursors were synthesized by precipitation reaction between ion exchange resin or ion exchange fiber and ammonium carbonate (as precipitation agent). The precursor then was roasted to prepared nano-CeO2powders with various sizes and morphologies. The precursor as CeCO3OH or Ce2O(CO3)2H2O was synthesized from the precipitation reaction of ion-exchange resin or ion-exchange fiber. And longer reaction time or lower reaction temperature is advantageous to the oxidative decomposition of CeCO3OH. Compared with ion-exchange fiber, ion-exchange resin is advantageous to get smaller size and higher dispersity precursor, and the size of the last product wouldn’t to be enlarged after roasting.2. Precursors were prepared through precipitation reaction between ion-exchange fiber and urea (as precipitation agent). Various morphologies precursors such as microchip, microspheric, needle-like and self-assembly cluster had been synthesized through modify advance exchange degree, concentration of urea, reaction temperature and reaction time. Product would be generated on the surface of ion-exchange fiber in the case of less concentrated urea. Crystal particle would form micron bar and outward stretch to self-assembly flower shape. High advance exchange degree and longer reaction time would increase the size of the product particle.