Study On Preparation Of CeO₂ With Controlled Size & Morphology And The Formation Mechanism

Nanometer cerium oxide as an important light rare earths product had become a material with the great applied prospect. New obtained use not only has something to do with its chemistry constitute and pure degree, but also with the index of size, morphologies and decentrality of CeO₂ nanoparticles. These bring forward the higher request to control the preparation process of CeO₂ nanoparticles. In this paper, the CeO₂ nanoparticles with different size and morphologies were obtained by controlling the preparation condition using nitric acid cerium as a raw material and choosing ammonia, urea, dimethyl oxalate as a precipitator respectively. The structure and performance of products were studied by means of XRD, BET, IR, TEM and TG-DTA.The relations between pH value and kinds of solvent, feeding method, aged time, additives and the size, morphologies of products were investigated by the numbers. The products were CeO₂ nanoparticle with integrated fluorite structure. The grain sizes can be controlled by adjusting the temperature of heat treatment or aged time. The results showed that the CeO₂ nanoparticles with different morphologies can be obtained by controlling the pH value. The well decentrality particles were got after adding SO42- as dispersant. Adding oxidant H₂O₂ at different time has different effects on morphologies. When using ethanol as solvent, the CeO₂ nanoparticle with 15nm and uniform distribution could be obtained. The feeding method also has important effects on particles morphologies. According to TG- DTA result, production structural formula CeO₂·1/2H₂O was predication.The CeO₂ precursor Ce₂O (CO₃)₂·H₂O belonging to single-phase orthorhombic system were prepared using urea as a precipitator. And the single-phase cubic system CeO₂ nanoparticles were obtained after calcinations. The influence factors in the synthesis process were investigated by the numbers and the obtained best reaction condition as follows: the ratio of raw materials was 1:40, the reaction temperature was 85℃and the reaction time was 4 hours. The ultrafine CeO₂ precursor synthesized at...