化学气相传输法分离稀土混合氧化物Sm2O3-Eu2O3-Gd2O3

以ＡｌＣｌ３ 为络合物配体, 研究Ｓｍ２Ｏ３Ｅｕ２Ｏ３Ｇｄ２Ｏ３ 的分离特性。结果表明, 其传输能力为：Ｓｍ ≈Ｇｄ＞ Ｅｕ, 氯化物主要在９８０ ～１１００ Ｋ 沉积。不同温区的最大分离系数分别为： βＥｕ／Ｓｍ;１２００ Ｋ＝ １－７０ ,βＥｕ／Ｇｄ;１３００ Ｋ＝ １－８８ , βＳｍ／Ｇｄ;１３００ Ｋ ＝ １－２４ , β′Ｓｍ／Ｅｕ;８５０ ～８８０ Ｋ＝ ２－７６ , β′Ｇｄ／Ｅｕ;８８０～９００ Ｋ ＝ ２－８３ , β′Ｇｄ／Ｓｍ;８００ Ｋ＝１－１２ , 高于传统的湿法分离系数。     

Phase equilibrium in the Sb2Se3-Gd2Te3 system

The Sb₂Se₃-Gd₂Te₃ system was studied using differential thermal analysis, X-ray powder diffraction, and microstructure examination. This is a quasi-binary system. Sb₂Se₃-based solubility at 300 K is 10 mol % Gd₂Te₃. The eutectic contains 20 mol % Gd₂Te₃ and melts at 760 K. One incongruently melting compound (870 K) of composition GdSbTe_1.5Se_1.5 was found in the system.     

Antimony dispersion and phase evolution in the Sb2O3-Fe2O3 system

This paper studies the antimony spreading and segregation that occurred along with the oxidation and solid-state reactions in the Fe2O3-Sb2O3 system. XRD, SEM, TG-DSC and particularly XPS were employed for characterizations. Sb2O4 and FeSbO4 are the only new phases detected. The formation of FeSbO4 is a more exothermic but slower reaction than oxidation of Sb2O3. A mechanical grinding of Sb2O3 and Fe2O3 leads to a significant dispersion of Sb2O3 possibly because of its low hardness. Dispersion of reference Sb2O4 in this way is negligible. During the heating of a mixture of Sb2O3 and Fe2O3 with an atomic ratio of Sb/Fe = 0.5 at 200-1000 degrees C in ambient air, the thermal spreading of Sb2O3 onto Fe2O3 increases with increasing temperature until Sb2O3 is oxidized into Sb2O4. The surface atomic ratio of Sb/Fe measured by XPS, R(Sb/Fe), reaches a maximum around 400 degrees C. The complete oxidation of Sb2O3 leads to a decrease in R(Sb/Fe) because of poorer dispersibility of Sb2O4. The formation of FeSbO4 starting at ca. 800 degrees C causes a further decrease in R(Sb/Fe), but the R(Sb/Fe) is still 3.2 times the nominal bulk Sb/Fe ratio when the Sb2O4 is completely transformed into FeSbO4.     

Structural features of ZrO2-Y2O3 and ZrO2-Gd2O3 nanoparticles formed under hydrothermal conditions

We synthesized nanoparticles of variable composition based on zirconium dioxide in the ZrO₂-Y₂O₃ (or Gd₂O₃)-H₂O systems under hydrothermal conditions. By X-ray diffraction and small-angle X-ray scattering studies revealed that the nanoparticles consist of crystalline core and amorphous shell. Increase of Y₂O₃ (or Gd₂O₃) content yields increases of shell size and decreases of core size. The effect is due to suppressed ZrO₂ crystallites growth caused by development of the shell preventing zirconium ions transport.     

Ionic conductivity,phase composition,and local defect structure of ZrO2-Gd2O3system solid solution crystals

Journal of Solid State Electrochemistry - The crystalline structure, ionic conductivity, and local structure of ZrO2-Gd2O3solid solution crystals have been studied for a wide range of compositions....     

Y2O3,CeO2掺杂的Mg-PSZ陶瓷材料研究

采用传统的陶瓷工艺制备少量掺杂Ｙ２Ｏ３,ＣｅＯ２的Ｍｇ－ＰＳＺ陶瓷,材料在较低的温度下烧结致密并实现了微晶化,探讨了Ｙ２Ｏ３,ＣｅＯ２的复合稳定作用和１１００℃热处理过程对材料相组成、显微结构和力学性能的影响。经１１００℃适当时间热处理,Ｙ２Ｏ３,ＣｅＯ２的复合稳定作用有效报制亚共析分解反应发生,优化调整ｃ－ＺｒＯ２晶粒中的ｔ－ＺｒＯ２析出体成核长大过程。断裂特征为穿晶、沿晶兼有,相变增韧和微裂纹     

Sm2O3掺杂CeO2纳米粉体的烧结动力学

对Sm2O3掺杂CeO2纳米粉体的烧结性能进行了研究, 得出等速烧结过程中试样的线收缩率、密度、气孔率随烧结温度的变化规律, 它们随烧结温度的变化均呈"S"型曲线关系, 利用非线性回归了等速烧结过程动力学方程. 结果表明, Sm2O3掺杂CeO2纳米粉体的烧结过程分为3个阶段, 当烧结温度低于1000 ℃时, 线收缩率与密度变化较小, 处于烧结的初期; 在1000～1400 ℃时, 随着烧结温度的升高, 线收缩率与体积密度急剧增大, 材料开始烧结并致密化; 当烧结温度高于1400 ℃时, 线收缩率与体积密度趋于一恒定值, 材料已经致密化. 由归一化速率方程可知, 在T=1225 ℃时, 材料的烧结致密化速率最大.     

钴铈复合金属氧化物催化剂上氧化亚氮催化分解性能研究

采用共沉淀法制备了一系列钴铈复合金属氧化物催化剂CoCex(x=0～0.2,x为Ce/Co摩尔比),进行了比表面积和XRD表征,并考察了它们对氧化亚氮催化分解反应的活性.结果表明,随着铈添加量的增加,催化剂上钴尖晶石相的衍射峰逐渐宽化,同时催化剂的比表面积逐渐增大;催化剂的活性随着铈添加量的增加先升高,然后下降,CoCe0.05催化剂表现出了最佳催化活性.在对CoCe0.05催化剂制备条件的考察实验中发现,共沉淀过程中控制pH值在9左右,于400 ℃焙烧得到的催化剂的活性最好.当反应气氛中存在O2或H2O时,CoCe0.05催化剂上N2O的分解反应受到抑制,但这种影响是可逆的,可能是由于它们与N2O在相同的活性位上存在竞争吸附.     

共沉淀-喷雾干燥法制备Sm2O3掺杂CeO2纳米粉体

以Sm（NO3）3.6H2O和Ce（NO3）3.6H2O为原料,用共沉淀-喷雾干燥法制备了Sm2O3掺杂CeO2（SDC）粉体。通过沉降实验、TG-DSC、XRD、BET、SEM和粒度分布对前驱体的分散性、稳定性及制得的SDC粉体性能进行表征,研究了洗涤方法、分散剂对前驱体及SDC粉体的影响。结果表明：无机陶瓷膜洗涤后前驱体分散性好,经500℃以上温度焙烧后的粉体为立方萤石型结构。加入分散剂后前驱体的分散性明显提高,制得的SDC粉体比表面积显著增加,最终获得了晶粒平均粒径为12.51 nm、团聚态颗粒为球形的SDC纳米粉体。     

Methane Decomposition over Ni/α-Al2O3 Promoted by La2O3 and CeO2

The decomposition of methane on Ni/a-Al2O3 modified by La2O3 and CeO2 with differ-ent contents has been investigated and the ralationship between methane decomposition and removal of carbon by CO2 over these catalyst has also been studied by pulse-chromatography. The catalysts were characterized by TPR and XRD. It was shown that Ni/a-Al2O3 could be promoted by adding La2O3, and the carbon species produced over this catalyst was activated and eliminated by CO2. But CeO2 would suppress the decomposition of methane over Ni crystallite. Both La2O3 and CeO2 can inhibit aggregation of the Ni particles. Decomposition of methane over the Ni-based catalysts is structure sensitive to a certain extent.     

纳米Sm2O3掺杂CeO2粉末的制备和性能表征

以Ce2(CO3)3和Sm2O3为原料, 用改进的氨水-双氧水沉淀法制备了CeO2和(CeO2)0.8为基质(Sm2O3)0.2的纳米粉末.对干燥后的氢氧化物进行了TG/DSC热分析, 约650 ℃时Ce(OH)4完全转变为CeO2.XRD分析表明, 650 ℃焙烧的粉末为萤石结构, 说明Sm2O3已固溶到CeO2中.经TEM测试, 粉体颗粒大小在5～10 nm之间, BET测试的平均颗粒尺寸为11.2 nm.由TEM照片还可以看出粉体具有良好的分散性, 且无硬团聚体存在.     

Methane Decomposition over Ni/α-Al_2O_3 Promoted by La_2O_3 and CeO_2

The decomposition of methane on Ni/a-Al2O3 modified by La2O3 and CeO2 with different contents has been investigated and the ralationship between methane decomposition and removal of carbon by CO2 over these catalyst has also been studied by pulse-chromatography. The catalysts were characterized by TPR and XRD. It was shown that Ni/a-Al2O3 could be promoted by adding La2O3, and the carbon species produced over this catalyst was activated and eliminated by CO2. But CeO2 would suppress the decomposition of methane over Ni crystallite. Both La2O3 and CeO2 can inhibit aggregation of the Ni particles. Decomposition of methane over the Ni-based catalysts is structure sensitive to a certain extent.     

Thermal synthesis of the CeO2-PrO2-La2O3 pigments

The synthesis of new compounds based on CeO₂-PrO₂-La₂O₃, which can be used as pigments for colouring of ceramic glazes, is investigated in our laboratory. The optimum conditions for the syntheses of these compounds have been estimated. The first information about the temperature region of the formation of the pigments investigated is provided by thermal analysis. The synthesis of these compounds is followed by thermal analysis using STA 449/C Jupiter (Netzsch, Germany). This revised version was published online in July 2006 with corrections to the Cover Date.     

Pd/γ-Al2O3三效催化剂中CeO2-ZrO2-La2O3的作用

用浸渍法制备了CeO2-ZrO2-La2O3复合氧化物,用XRD,TG-DTA,拉曼光谱、H2-TPR和BET表面积测定等方法对合成的样品进行了表征,研究了在单钯Pd/γ-Al2O3催化剂中添加CeO2-ZrO2-La2O3对催化剂活性和热稳定性的影响.结果表明,在Pd/γ-Al2O3中加入三元复合氧化物有利于提高三效催化剂的热稳定性,有利于阻止γ-Al2O3在高温时的相变以稳定Al2O3结构,防止在高温条件下催化剂表面积的损失.在Pd的负载量为1 g*L-1条件下,测定了Pd/CeO2-ZrO2-La2O3/γ-Al2O3/蜂窝陶瓷催化剂对CO,C3H6和NO净化的三效活性,研究了催化剂的结构和三效催化活性之间的关系.结果表明,CeO2-ZrO2-La2O3的存在能明显提高Pd基催化剂对CO,C3H6和NO的三效净化活性,扩大催化剂的操作窗口,提高在富氧条件下对NOx的还原性能.     

Theoretical study of CeO2 and Ce2O3 using a screened hybrid density functional

The predicted structures and electronic properties of CeO(2) and Ce(2)O(3) have been studied using conventional and hybrid density functional theory. The lattice constant and bulk modulus for CeO(2) from local (LSDA) functionals are in good agreement with experiment, while the lattice parameter from a generalized gradient approximation (GGA) is too long. This situation is reversed for Ce(2)O(3), where the LSDA lattice constant is much too short, while the GGA result is in reasonable agreement with experiment. Significantly, the screened hybrid HSE functional gives excellent agreement with experimental lattice constants for both CeO(2) and Ce(2)O(3). All methods give insulating ground states for CeO(2) with gaps for the 4f band lying between 1.7 eV (LSDA) and 3.3 eV (HSE) and 6-8 eV for the conduction band. For Ce(2)O(3) the local and GGA functionals predict a semimetallic ground state with small (0-0.3 eV) band gap but weak ferromagnetic coupling between the Ce(+3) centers. By contrast, the HSE functional gives an insulating ground state with a band gap of 3.2 eV and antiferromagnetic coupling. Overall, the hybrid HSE functional gives a consistent picture of both the structural and electronic properties of CeO(2) and Ce(2)O(3) while treating the 4f band consistently in both oxides.     

Thermal behaviour of CO2 laser-irradiated CeO2 doped with Yb2O3

Results concerning the thermal behaviour of Yb₂O₃-doped CeO₂ samples irradiated with CO₂ laser beams in continuous wave are presented.

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Zusammenfassung Es werden Ergebnisse einer Untersuchung des thermischen Verhaltens von CeO₂-Proben dargelegt, die mit CO₂-Laser bestraht wurden.

     

Microstructural evolution of CeO2 from porous structures to clusters of nanosheet arrays assisted by gas bubbles via electrodeposition

Here we report the preparation of porous CeO2 and clusters of CeO2 nanosheet arrays via a simple, efficient electrochemical approach. Gas bubbles functioning as a dynamic template were utilized in our research for the synthesis of nanosheet array clusters. The Hc and Mr values of porous CeO2 are almost the same as those of CeO2 nanosheet array clusters at 5 K, and they are about 5916 Oe and 8.83 x 10(-4) emu, respectively. However, the saturation magnetization of CeO2 nanosheet array clusters is much larger than that of porous CeO2 structures. The magnetic property of the prepared CeO2 deposits may be caused by the existence of Ce(III), indicating potential interest in the nanodevices because of their electronic and magnetic properties.     

TSL and EPR studies of SrBPO5 doped with CeO2 and co-doped with CeO2 and Sm2O3

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) investigations were carried out on gamma irradiated SrBPO₅ samples doped with CeO₂ and co-doped with CeO₂ and Sm₂O₃. On gamma-irradiation at room temperature, BO₃ ^2–, O₂ ^– and O^– radicals were produced. It was seen that the O^– radical ion disappeared in the sample annealed at 500 K. It is proposed that the recombination between trapped electrons and O^– radical ions results in transfer of recombination energy to the impurity centre Ce³⁺ resulting in TSL glow peak at 485 K. In the case of co-doped samples energy transfer occurs between Ce³⁺ to Sm³⁺ resulting in increase in the intensity of glow peak at 485 K.The authors are grateful to Dr. V. K. Manchanda, Head, Radiochemistry Division, BARC for his keen interest and encouragement during the course of this work.     

铈和镧改性γ-Al2O3担载Pd催化剂的结构效应

分别以镧-铈、铈-镧顺序浸渍和镧铈共浸渍的方式在γ-Al2O3载体上引入助剂La2O3和CeO2,然后担载Pd制备了一系列催化剂.以甲醇分解为探针反应,采用XRD、EXAFS和XPS对催化剂的体相和表面结构进行表征,用BET法测定比表面积,并进行了吸附态CO的FTIR研究.结果表明,La2O3容易进入CeO2的晶格中,促进了CeO2在γ-Al2O3上的分散.但不同的La2O3、CeO2加入方式对活性组分Pd在改性载体上的分散度、优势暴露面及其与CeO2之间的相互作用产生不同的影响.关联甲醇分解性能测试结果说明,Pd在载体上的高度分散以及Pd和CeO2之间通过界面产生的强相互作用是催化剂具有高活性的关键.