沉淀法合成的纳米CeO2前驱体的热分解动力学

以Ce(NO3)3.6H2O为铈源,(NH4)2 CO3.H2O为沉淀剂,加入少量PEG4000作为分散剂,采用化学沉淀法并经水洗、超声波醇洗,70℃干燥后得到CeO2的前驱体Ce2(CO3)3.H2 O。对Ce2(CO3)3.H2 O样品运用差示/热重分析(DSC/TG)和X射线衍射(XRD)方法进行其热分解过程研究,并通过多重速率扫描法记录样品在不同升温速率下的DSC/TG曲线,采用Kissinger-Akahira-Sunose(KAS)法和Coats-Redfern法进一步研究Ce2(CO3)3.H2 O的热分解动力学。研究结果表明:Ce2(CO3)3.H2 O热分解反应过程分2步进行,主要反应阶段的反应动力学参数是:反应活化能为105.51 kJ/mol,反应级数为2,频率因子为3.61;由此推断出可能的Ce2(CO3)3.H2 O热分解机理函数为Anti-Jander方程,受三维扩散机制控制。

Thermal decomposition kinetics of precursor of CeO2 nanocrystalline prepared by precipitation method

With Ce(NO3)3.6H2O and(NH4)2 CO3.H2O as raw materials,the precursor Ce2(CO3)3.H2O of CeO2 nanocrystalline was prepared by chemical precipitation method using a little amount of PEG4000 as surfactant.The technique of DSC/TG and XRD were used to study the process of thermal decomposition.In particular,the differential thermal analysis curves were measured at different temperature raising-rate in air atmosphere for decomposition of the precursor of CeO2 nanocrystalline by thermal analysis apparatus.The kinetics process was studied with the method of Kissinger-Akahira-Sunose(KAS) and Coats-Redfern.The results show that the decomposition of Ce2(CO3)3.H2O consists of two steps.The active energy of the main step is 105.51 kJ/mol,the reaction order is 2,and the frequency factor is 3.61.The possible conversion functions for the decomposition of the precursor of CeO2 nanocrystalline is Anti-Jander equation and the mechanism of reaction is three-dimensional diffusion.