沉淀法合成纳米CeO_2的晶粒生长动力学  

Kinetic of Grain Growth of CeO_2 Nanocrystalline Prepared by Precipitation Method

作　　者：宋晓岚[1] 邱冠周[1] 曲鹏[1] 杨振华[1] 

机构地区：[1]中南大学,湖南长沙410083

出　　处：《稀有金属材料与工程》2005年第7期1085-1088,共4页Rare Metal Materials and Engineering

基　　金：湖南省自然科学基金项目资助(03JJY3015);国家自然科学基金项目资助(59925412)

摘　　要：以Ce(NO3)3·6H2O为铈源,(NH4)2CO3·H2O为沉淀剂,并加入一定量表面活性剂PEG4000,采用液相沉淀法制备前驱体Ce2(CO3)3·H2O,前驱体经热处理合成纳米CeO2。根据XRD线宽法研究了纳米CeO2热处理过程的晶粒生长动力学,结果表明:随焙烧温度升高,CeO2晶粒尺寸显著增大;300℃下焙烧时间对CeO2晶粒尺寸影响不明显,700℃下CeO2晶粒随焙烧时间延长而长大,且焙烧初期粒径增长较快,超过180min后增长速率变慢;700℃时CeO2晶粒生长指数为5,即符合5次方动力学方程,晶粒生长速率常数为1.9865×104nm5/min;由于纳米尺寸效应,使得CeO2晶粒生长活化能在低温区和高温区不同,低于400℃时为25.64kJ/mol,高于400℃时为87.64kJ/mol;认为热处理过程CeO2的晶粒生长为扩散生长机制。CeO2 nanocrystalline has been successfully synthesized by heating the precursor Ce-2(CO3)(3)(H2O)-H-. using Ce(NO3)(3).6H(2)O as Ce source, (NH4)(2)(CO3H2O)-H-. as an precipitant, adding a little of PEG4000 as surfactant. Kinetic study is conducted on the grain growth of CeO2 nanocrystallite by calculating the grain size using the Scherrer formula during isothermic heating at different temperatures. The results indicate that the grains of CeO2 nanocrystallites grow up with increasing of the calcination temperature. The effect of calcination time on the grain sizes of CeO2 nanocrystallites is not obvious at 300 degrees C, but the grain sizes increase with prolonging of the calcination time at 700 degrees C, especially at the initial stage of calcinations. At 700 degrees C, the grain growth exponent is five, viz the grain growth conforms to the fifth order kinetic equation, and the kinetic rate constants is 1.986 5 x 10(4) nm(5)/min. The activity energy calculated for the grain growth of CeO2 nanocrystallites is 25.64 kJ/mol at the temperature lower than 400 degrees C, and 87.64 kJ/mol at the higher temperature, owing to the effects of nanometer scale.

关 键 词：纳米CEO2 沉淀法 热处理 晶粒生长 动力学 活化能 

分 类 号：O614.332[理学—无机化学]