氧化铈纳米粒子的制备

CeO2属于萤石型氧化物。 CeO2晶胞中的Ce4+按面心
石型晶体结构，这种亚稳氧化物暴露于氧化环境 时又易被氧化为CeO2，因而CeO2具有优越的储存 和释放氧功能及氧化还原反应能力，同时CeO2也 有着良好的化学稳定性和高温快速氧空位扩散能 力。
立方点阵排列，O2-占据所
有的四面体位置，每个Ce4+ 被8个O2-包围，而每个O2则与4个Ce4+配位。
precipitation Stir and ageing stage Scouring and drying to calcine precursor The power of CeO2
technology of direct precipitation
Results and discussion
Fig. 1. DTA/TG of Ce(OH)4 precursor The total measured weight loss from 25 to 900 ℃ was 11.64%, while the theoretical weight loss for the decomposition of cerium hydrate oxide is 17.3%, i.e. Ce(OH)4/CeO2· 2H2O to CeO2
ceria acetate was diluted, placing 30 ml of the solution into the Teflon vessel
the bomb was then placed in the oven and heated to 250℃ at different treatment times
1. Direct precipitation
Ce3+ or Ce4+
precipitant
Nitrate: Ce(NO3)3 or (NH4)2Ce(NO3)6 Precipitant: ammonia or NH4HCOwenku.baidu.com Surface active agent: PEG-4000 Process: nitrate and PEG-4000
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SEM photoes of precursor
XRD of precursor
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XRD of CeO2 synthesized at 600℃
The final products were re-washed, conductivity<=2ms, dried at 75 ℃
A.I.Y. Tok ,et al (Nanyang Technological University), Journal of Materials Processing Technology 190 (2007) 217 –222
the difference in weight loss observed could be due to the following reasons: (a) precipitate consisting of a partially hydrated form of ceria, (i.e. CeO2· xH2O), for which a 11.64% weight loss on decomposition corresponds to x = 1.35 or (b) the precipitate consisted of a mixture of phases like CeO2· 2H2O+ CeO2
Jan 3, 2008
1.Simply introduce the structure and applications of CeO2 2. Synthesis of nanocrystalline CeO2 by different methods 3. Future works
Brief introduction
were dissolved in distilled wate.Then
ammonia or NH4HCO3 solution was added dropwise under vigorous stirring till the pH reached 9. The precipitate was filtered, washed thrice with distilled water and alcohol and dried at 80℃ over night.
Microwave homogeneous precipitation
Nitrate: Ce(NO3)3 or (NH4)2Ce(NO3)6 Precipitant: urea Surface active agent: PEG-4000
CO(NH2)2 + H2O → CO2 + 2NH3 NH3 + H2O → NH4+ + OHCO2 + H2O → CO32- + 2H+ 水解生成的构晶 离子OH-、CO32-, 在微波辐照作用 下,与Ce3+、Ce4+ 等结合生成不溶 前驱物
The first endothermic peak was detected at around 100 ℃ . This is attributed to the release of the water molecules present in the precursor From 100 to 200℃, the weight loss was attribute to the removal of the surface acetate groups and later the formation of the acetic acid when surface acetate hydrolysis occurs. This also explains the very weak endothermic peak detected at 200℃ As temperature increased to 700℃, the Ce2O2CO3 decomposed endothermally to produce the final product CeO2
(a): Ce(NO3)3 + NH3· H 2O (b): (NH4)2Ce(NO3)6 + NH3· H2O
(c): Ce(NO3)3 + NH4HCO3
(d): (NH4)2Ce(NO3)6 + NH4HCO3
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XRD of precursor (a)
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700℃
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600℃
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XRD of CeO2 synthesized at 600℃、700℃
SEM photo of precursor(a)
SEM photo of CeO2 calcined at 600℃
Hydrothermal synthesis of CeO2 nano-particles
1. Cerium(IV) hydroxide precursor
H2O2 + cerium(III) nitrate , stirred for 5 min under heat to convert Ce3+ to Ce4+
the products were later centrifuged and dried at 75 ℃
Results and discussion
The decomposition of the precursor is a form of dehydration process of the hydrated CeO2
Fig. 2 DTA/TG of ceria acetate precursor
The precursor measured a total weight loss of 12.55% with four distinct temperature peaks There was a sharp weight loss from 200 to 400℃ and a corresponding exothermic peak. This exothermic peak suggests the formation of oxyacetate and dioxocarbonate complexes with cerium, Ce(OH)(CH3COO) and Ce2O2CO3
2. Ceria acetate precursor
hydrous cerium oxide stabilized by acetate ions (cerium acetate gel) was dissolved in deionized water to yield ‘acetate stabilized colloidal ceria and will be identified as ceria acetate
+ammonia (pH =8.8), stir continuously at 80 ℃ for 1 h
the pale yellow precipitates (Ce(OH)4) were washed ,the conductivity of the supernatant <=2ms
30 ml of the washed precipitates (pH=10) were placed into the Teflon vessel of the hydrothermal bomb, then placed in the oven and heated at the respective durations (0–24 h)
1. Structure of CeO2
2.功能特性
CeO2的结构中有1/2立方体空隙，可称之为敞 型结构。敞型结构允许离子快速扩散。经高温(T ＞950℃)还原后，CeO2转化为具有氧空位、非化
学计量比的CeO2-X氧化物(0<x<0.5)，而在低温下
(T＜450℃) CeO2可形成一系列组成各异的化合物。 值得注意的是，即使从晶格上失去相当数量 的氧，形成大量氧空位之后，CeO2仍然能保持萤
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LS of CeO2 calcined at 600℃ (a) Ce(NO3)3 + urea, without PEG-4000 (b) Ce(NO3)3 + urea + PEG-4000
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(c) (NH4)2Ce(NO3)6 + urea + PEG-4000
Applications of CeO2
CeO2 Slurry
氧化铈抛光粉
氧化铈抛光轮
玻璃脱色剂氧化铈
大颗粒氧化铈磨料
氧化铈抛光粉/液晶显示屏
此外， CeO2还用作催化材料、高温氧敏材料、 pH传感材料、电化学池中膜反 应器材料、燃料电池的中间材料、中温固体氧化物燃料电池(SOFC)用电极材料
Synthesis of CeO2
Members: Xianhong Rui Yu Chen Litao Yan Huamin Yao Liangjun Yi Department of Materials Science and Engineering University of Science and Technology of China
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XRD of CeO2 synthesized at 500℃
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XRD of CeO2 synthesized at 700℃
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SEM photoes of CeO2 calcined at 600℃
Microwave reaction equipment
Results and discussion
(c) (b)
Mean: (a)0.093um (b)0.171um (c)0.210um
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XRD of precursor calcined at 500℃