摘要
采用以柠檬酸为配体的溶胶———凝胶法制备了 Ｃｅ Ｏ２ 超细粒子．考察了不同制备条件（ 金属离子与配体的摩尔比、反应温度、ｐ Ｈ、凝胶烘干温度、焙烧温度及时间） 对粒子的影响，获得了最佳的制备条件：金属离子与配体的摩尔比为１ ：３ 、反应温度为６５ ℃、ｐ Ｈ＜ ０（ 未调） 、凝胶烘干温度为６５ ℃、３２０ ℃焙烧温度２ｈ ．并在该条件下成功地制得了均匀分散的 Ｃｅ Ｏ２ 超细粒子（ 平均粒径为１０ｎｍ ，比表面为５７ ｍ ２／ｇ） ．
Ultrafine CeO 2 particles were perpared by sol gel method using citric acid as complex agent. The influence of preparation conditions such as molar ratio of Ce 3+ and citric acid, reaction temperature, pH value, drying temperature of the gel, calcination temperature and time of xerogel on the particle size and specific surface area has been studied in detail. XRD, TEM, DTA and BET surface area measurements were used for the samples characterization. It is found that the molar ratio of Ce 3+ and citric acid has a significant effect on the particle size, dispersion state and surface area of CeO 2 sample. As the ligand amount increases, the product diameter increases and surface area decreases but the better homogenity is obtained. The best ratio is Ce 3+ /citric=1:3. The pH value of the solution needs to keep below zero, otherwise the particle size would be larger than 100nm and inhomogeneous. Four different reaction temperatures (55℃,65℃,75℃ and 85℃) were selected to study the reaction temperature effect on the gel formation. The result shows that the homogeneous gel can be formed below 65℃ and the gelatinization increases with lowering the temperature, the best reaction temperature is 65℃. DTA analysis of the dried gel shows that there are two exothermic peaks at 135℃ and 270℃, representing the decomposition of HNO 3 and citric acid. After calcination at 320℃ for 2h, ultrafine dispersed CeO 2 can be obtained. The particles begin to aggregate beyond 500℃ and sinter over 800℃. Calcination time also affects the ultrafine particle size; at 320℃ calcined for 8h, the particles begin to aggregate. XRD spectra shows that after calcination at 250℃ characteristic peaks of CeO 2 occur, and the intensity of these characteristic peaks for CeO 2 increases with the temperature. The above results suggest that too high or too low calcination temperature and too long are not suitable for ultrafine particle preparation. The optimum preparation condition is as follows: Ce 3+ /citric=1:3, reaction temperature=65℃,pH<0, drying temperature of gel=65℃, calcination temperature and time are 320℃ and 2h. Under these conditions, monodispersed ultrafine CeO 2 particles with average particles size of 10nm and surface area of 57m 2/g were obtained.
出处
《南京大学学报（自然科学版）》
CAS
CSCD
1999年第4期486-490,共5页
Journal of Nanjing University（Natural Science）
基金
攀登项目资助课题
