高比表面CexZr1-xO2复合氧化物的制备及表征

分别采用共沉淀法和阴离子表面活性剂模板法制备了Ce_xZr_1-xO₂复合氧化物。采用XRD、AFM、FTIR以及N₂吸附-脱附等方法对样品进行了表征。结果表明，共沉淀法合成的样品在500 ℃煅烧2 h后，生成了立方相Ce_0.75Zr_0.25O₂和四方相Ce_0.5Zr_0.5O₂固溶体，比表面积为62.1 m²·g^-1，孔体积为0.097 cm³·g^-1；以阴离子表面活性剂十二烷基苯磺酸钠(SDBS)为模板剂，乙二胺为助模板剂合成的样品在500 ℃煅烧2 h后，生成了纯四方相Ce_0.5Zr_0.5O₂固溶体，比表面积为180 m²·g^-1，孔体积为0.182 cm³·g^-1。结果表明，以阴离子表面活性剂SDBS为模板剂，可以合成高比表面积且具有介孔结构的Ce_0.5Zr_0.5O₂复合氧化物；加入乙二胺作为助模板剂可明显的提高比表面积和孔体积。     

Ce1－xNdxO2－δ固溶体的电子顺磁共振谱和阻抗谱的研究

利用溶胶-凝胶方法在800 ℃焙烧10 h后, 合成了固溶体Ce_1－xNd_xO_2－δ (x＝0.05～0.55), X射线衍射(XRD)测试表明固溶体已经形成立方萤石结构; 电子顺磁共振谱(EPR)研究表明在固溶体Ce_1－xNd_xO_2－δ中随着掺杂量x的增大, Ce^3＋离子含量减少, 说明掺杂Nd^3＋离子可以抑制Ce^4＋的还原; 交流阻抗谱的测量表明固溶体Ce_0.9Nd_0.1O_2－d 具有离子导电特性, 600和700 ℃时的电导率分别为4.25×10^－3和1.12×10^－2 S•cm^－1, 活化能为0.68 eV.     

Ce0.5+xZr0.4-xLa0.1O2-Al2O3催化剂催化燃烧柴油车碳烟

采用共沉淀法制备了系列Ce_0.5+xZr_0.4-xLa_0.1O₂-Al₂O₃催化剂, 其中0≤x≤0.4且Ce_0.5+xZr_0.4-xLa_0.1O₂与Al₂O₃的质量比为1:1. 考察了该系列催化剂对柴油车排放碳烟的催化燃烧性能, 并用低温N2吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、氢气程序升温还原(H₂-TPR)和氧气程序升温脱附(O₂-TPD)等手段对催化剂进行了表征. 研究结果表明该系列催化剂均形成了具有立方萤石结构的固溶体. 当x=0.2时, Ce³⁺离子在催化剂表面有一定的富集, 此时催化剂具有最大的β氧脱附峰和最好的表面还原性能, 同时具有良好的催化碳烟氧化活性, 碳烟在该催化剂的起燃温度为360 °C, 具有较好的应用前景.     

柠檬酸溶胶-凝胶法制备的Ce1-xZrxO2: 结构及其氧移动性

采用 XRF、XRD、Raman、XPS、H₂-TPR 以及与氩离子刻蚀相结合的XPS等表征技术对柠檬酸溶胶-凝胶法制备的Ce_1-xZr_xO₂ (0≤x≤1)样品的结构及其氧移动性进行了研究. 结果表明, Ce_1-xZr_xO₂ 样品的晶型结构对其中氧的移动性有明显影响. 当x≤0.15 时, Ce_1-xZr_xO₂ 以立方CeO₂相 Ce-Zr-O 固溶体存在, 随着Zr含量的逐渐增加, CeO₂晶胞体积减小、氧空位浓度增加, 氧移动性逐渐增强; 当x＞0.15时, 形成四方ZrO₂相和立方CeO₂相Ce-Zr-O固溶体的混合物, 随着Zr含量的逐渐增加, 四方ZrO₂相的含量增加、氧空位浓度减小, 氧移动性逐渐减弱. 因此, Ce_0.852Zr_0.152O₂样品具有最高的氧移动性.     

镁掺杂氧化铈整体式催化剂催化CO2和CH3OH直接合成碳酸二甲酯

采用共沉淀法成功地合成了不同Mg掺杂量的Ce_1-xMg_xO₂(x=0.05、0.10、0.15、0.20)固溶体催化材料,并运用透射电子显微镜(TEM)、X射线衍射(XRD)、氮气吸附-脱附测试、拉曼光谱、X射线光电子能谱(XPS)、CO₂程序升温脱附(CO₂-TPD)等技术对这些材料进行了表征。结果发现,通过调控CeO₂晶格中Mg的含量,可以调控所制备的Ce_1-xMg_xO₂催化材料的粒径、比表面积、表面缺陷等。其中Ce_0.90Mg_0.10O₂展现了最佳的表面性质,具有最小的平均粒径(约5.8 nm),最大的比表面积(约136 m2·g^-1)以及最高的表面氧含量(31.98%)。将Ce_1-xMg_xO₂催化材料涂覆在堇青石蜂窝陶瓷上制成整体催化剂,考察其对CO₂和CH₃OH直接合成碳酸二甲酯的催化性能。在140℃、2.4 MPa、反应2 h的条件下,Ce_0.90Mg_0.10O₂整体催化剂上碳酸二甲酯的收率高达20.21%,催化效果明显优于CeO₂和其余的Ce_1-xMg_xO₂(x=0.05、0.15、0.20)催化材料。     

Ba1-1.5yLayZrxTi1-xO3固溶体的合成、结构与介电特性

用软化学合成方法在100℃以下制备了一系列Ba_1-1.5yLa_yZr_xTi_1-xO₃(0<x<0.3, 0≤y≤0.08)固溶体纳米粉末。XRD物相分析及晶间距-组成图表明，产品为完全互溶取代固溶体。用TEM观察可知其粒子为均匀球形，平均粒径为60纳米。通过制陶实验，对该系列固溶体的介电特性分别进行了测试。结果表明：采用化学掺杂方法在BaTiO₃中掺入适量锆、镧后，样品的室温介电常数可提高到30，000以上，并呈现出规律性。     

Ce4+替代Pu4+的模拟固化体(Gd1-xCex)2Zr2O7+x的合成及结构演变

Gd₂Zr₂O₇中Gd具有很大的中子吸收截面, 其烧绿石结构-缺陷萤石结构的转变能较低, 使其成为理想的核废料固化基材. 使用硝酸盐为原料, 添加少量NaF作助熔剂, 在较低温度下(和传统高温固相反应相比), 合成了烧绿石型Gd₂Zr₂O₇. 以Ce⁴⁺模拟Pu⁴⁺, 研究了Gd₂Zr₂O₇对锕系核素的固化, 并合成了系列模拟固化体(Gd_1-xCe_x)₂Zr₂O_7+x (0≤x≤0.6). 采用粉末X射线衍射(XRD)对系列样品进行了表征. 结果表明: 随着x值的增大,样品从烧绿石结构向缺陷萤石结构转变, 且晶胞大小基本保持恒定, 但当x=0.6时, 衍射峰明显宽化, 晶格畸变比较严重, 晶格稳定性降低. 当x=1时, 即用Ce⁴⁺完全取代Gd³⁺进行合成, 不能得到Ce₂Zr₂O₈, 产物发生了相分离, 为四方结构的(Zr_0.88Ce_0.12)O₂和萤石结构的(Ce_0.75Zr_0.25)O₂的混合物. 模拟固化体的浸出率测试表明: 当x≤0.2时, 各元素浸出率均很低, 但当x≥0.4时, 各元素的浸出率明显升高, 说明以Gd₂Zr₂O₇作为固化Pu⁴⁺的基材, Pu⁴⁺掺入量不宜高于40%.     

室温下制备以{211}晶面为主的Ti1-xVxO2薄膜及其可见光催化性能

以金属Ti和V作为靶材,采用直流反应共溅射技术在室温下制备了以{211}晶面为主的锐钛矿相Ti_1-xV_xO₂薄膜,研究了不同V靶功率对Ti_1-xV_xO₂薄膜的薄膜成分、晶相结构和可见光催化性能的影响。研究表明,Ti_1-xV_xO₂薄膜的晶相结构为锐钛矿相,择优取向为(211),而结晶度受V靶功率的影响。随着V靶功率的增加,薄膜中V元素含量逐渐增加,同时,晶粒和沉积速率也逐渐增加。另外,当V靶功率为150W时,薄膜的表面粗糙度值有一个最大值。V的掺杂导致薄膜的能带间隙变窄,对光的吸收向可见光区偏移,从而有效地改善了薄膜的可见光催化能力。当V靶功率为150W时,Ti_1-xV_xO₂薄膜的能带间隙值为2.82eV,其在2h的可见光照射下分解了80%的RhB染料。这被归结于能带间隙窄,高能晶面{211}和结晶度高的共同作用。     

室温下制备以{211}晶面为主的Ti1-xVxO2薄膜及其可见光催化性能

以金属Ti和V作为靶材,采用直流反应共溅射技术在室温下制备了以{211}晶面为主的锐钛矿相Ti_1-xV_xO₂薄膜,研究了不同V靶功率对Ti_1-xV_xO₂薄膜的薄膜成分、晶相结构和可见光催化性能的影响。研究表明,Ti_1-xV_xO₂薄膜的晶相结构为锐钛矿相,择优取向为(211),而结晶度受V靶功率的影响。随着V靶功率的增加,薄膜中V元素含量逐渐增加,同时,晶粒和沉积速率也逐渐增加。另外,当V靶功率为150 W时,薄膜的表面粗糙度值有一个最大值。V的掺杂导致薄膜的能带间隙变窄,对光的吸收向可见光区偏移,从而有效地改善了薄膜的可见光催化能力。当V靶功率为150 W时,Ti_1-xV_xO₂薄膜的能带间隙值为 2.82 eV,其在2 h的可见光照射下分解了80%的RhB染料。这被归结于能带间隙窄,高能晶面{211}和结晶度高的共同作用。     

铈锆固溶体的微波辅助法制备及表征

采用共沉淀法并结合不同的老化处理方式(室温陈化、常规加热回流和微波辅助加热回流)制备了Ce_0.6Zr_0.4O₂固溶体。利用SEM、N₂吸附、XRD、Raman光谱和H₂-TPR等技术对样品的形貌、比表面积、孔结构、晶相结构、高温热稳定性和还原性进行了表征,并考察了其对CO氧化反应的催化性能。结果表明,微波辅助加热回流老化处理所制备的固溶体属于立方萤石结构,颗粒的大小均匀,表面结构疏松,具有最大的比表面积和孔容、最高的热稳定性及最好的低温还原性。CO氧化实验表明微波辅助加热回流老化处理所制备的Ce_0.6Zr_0.4O₂固溶体具有最好的催化氧化活性。     

Direct synthesis of dimethyl carbonate ?from CH3OH AND CO2 by H3PW12O40/CexTi1-xO2 catalyst

Summary Ce_xTi_1-xO₂ and H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts were prepared using a sol-gel method, and applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ showed a better catalytic performance than the corresponding Ce_xTi_1-xO₂, due to the bifunctional catalysis of Br?nsted acid sites (provided by H₃PW₁₂O₄₀) and base sites (provided by Ce_xTi_1-xO₂). H₃PW₁₂O₄₀/Ce_0.1Ti_0.9O₂ showed the highest catalytic performance among the H₃PW₁₂O₄₀/Ce_xTi_1-xO₂ catalysts.     

Improvement of the oxidation behavior of Ti1-xAlxN hard coatings by optimization of the Ti/Al ratio

The oxidation behavior of cubic Ti_1-xAl_xN films was improved by decreasing the Ti/Al ratio from 50/50 in the direction of the phase transition between cubic and hexagonal structure. Metastable, polycrystalline, single-phase Ti_1-xAl_xN films were deposited on high speed steel (HSS) substrates by reactive magnetron sputtering ion plating (MSIP). The composition of the bulk was determined by electron probe microanalysis (EPMA), the crystallographic structure by thin film X-ray diffraction (XRD). A Ti_1-xAl_xN film with a Ti/Al atomic ratio of 38/62 was deposited in cubic NaCl structure, whereas a further decrease of the Ti/Al ratio down to 27/73 led to a two-phase film with both cubic and hexagonal constituents. The Ti_0.38Al_0.62N film was oxidized in synthetic air for 1 h at 800?°C. The oxidic overlayer was analyzed by X-ray photoelectron spectroscopy (XPS) sputter depth profiling, EPMA crater edge linescan analysis, and secondary neutrals mass spectroscopy (SNMS). Scanning electron microscopy (SEM) micrographs of the cross sectional fracture were taken for morphological examination. With higher Ti content, the Ti_1-xAl_xN formed a TiO_2-x rich sublayer beneath an Al₂O₃ rich toplayer, whereas the oxide layer on the Ti_0.38Al_0.62N film consisted of pure Al₂O₃. The thickness of the oxide layer was determined to 60–80 nm, about a quarter of the oxide layer thickness detected on Ti_0.5Al_0.5N films. The absence of a TiO_2-x sublayer was also confirmed by XRD. The results show a distinct improvement of the oxidation resistance of cubic Ti_1-xAl_xN films by increasing the Al content from x = 0.5 to 0.62, whereas a further increase leads to the hexagonal structure, which is less suitable for tribological applications due to its tendency to form cracks during oxidation.     

Thermal characterization of Er-doped and Er–Gd co-doped ceria-based electrolyte materials for SOFC

Ce_1?xEr_xO₂ and Ce_1?2xEr_xGd_xO₂ co-doped ceria electrolyte nanopowder materials were successfully prepared by sol–gel method. Depending on the temperature, the crystal structure changes were analyzed by X-ray diffraction. It was observed that the crystal size of the electrolytes decreased depending on the temperature and the time. X-ray diffraction results confirmed cubic fluorite structure in the samples. The microstructural properties of the samples were analyzed by scanning electron microscopy, and thermal stability measurement was performed by thermogravimetric and differential thermal analyses. The total electrical conductivity of the nanopowder electrolytes was determined by the dc four-point probe technique in air at temperatures ranging from room temperature to 1373 K. The four-probe conductivity results revealed that Ce_0.8Er_0.1Gd_0.1O₂ has a higher ionic conductivity compared to Ce_0.83Er_0.17O₂ at 1123 K. The four-probe conductivity results show that both Ce_1?xEr_xO₂ and Ce_1?2xEr_xGd_xO₂ solid electrolytes have potential application to oxide ionic conductor for solid oxide fuel cells.     

Pt/CexZr1-xO2 催化剂在含硫合成气中催化水煤气变换反应活性

 采用浸渍法制备了 Pt/Ce_xZr_1-xO₂ 催化剂, 通过 X 射线衍射和程序升温还原等方法对催化剂进行了表征, 并在固定床反应器中评价了催化剂在合成气和含硫合成气中的水煤气变换活性. 结果表明, 铈锆固溶体的氧化还原能力强于 CeO₂, Zr 的掺杂明显改善了 CeO₂ 的孔道结构, 其担载的 Pt 催化剂具有更高的金属分散度, 因而活性更高. 两种催化剂在含硫合成气中的催化活性较无硫合成气中的均有所降低, 且 H₂S 浓度越大, 催化剂活性下降越多, 但这种因吸附硫而引起的失活是可逆的, 即催化剂重新暴露在无 H₂S 重整气的还原性气氛下活性能基本恢复.     

Sol–gel synthesis and catalytic property of Ce1−x Ti x O2 nanocomposites supported on attapulgite clay

Ce_1?x Ti _x O₂ nanocomposites supported on attapulgite clay (Ce_1?x Ti _x O₂/ATP) were prepared by a facile sol–gel route. The textural and structural properties of the prepared products were characterized by thermogravimetric-differential scanning calormetry analysis, X-ray diffraction, transmission electron microscopy, energy-dispersive spectrometry, Fourier transform infrared spectroscopy and Nitrogen adsorption-desorption measurements. The catalytic activity of the prepared Ce_1?x Ti _x O₂/ATP catalysts for rhodamine B degradation was investigated. Results indicate that the particle size of Ce_1?x Ti _x O₂ nanoparticles evenly attached onto the surface of ATP is approximately 10 nm. The Ti⁴⁺ doping ratios exhibit considerable impact on the redox ability and catalytic activity of Ce_1?x Ti _x O₂/ATP composites. The introduction of an optimal amount of Ti⁴⁺ contributes to forming structure defects and electronic defects in the oxide lattice, increasing concentration of oxygen vacancies, consequently improving low-temperature redox ability of Ce⁴⁺ and enhancing catalytic activity of the composites. Ce_1?x Ti _x O₂/ATP (x = 0.5) catalyst has the best catalytic degradation efficiency, which can reach as high as 97 % after reaction for 240 min. It is also found that attapulgite clay exhibit a positive synergistic effect to the Ce_1?x Ti _x O₂ nanoparticles.     

Physicochemical properties of the surface of the (Y,La0.1)Ce x Zr1? x O2?δ( x = 0.1–0.7) and Y0.1Pr0.3Zr0.6O2?δ complex oxide systems

The physicochemical properties of the surface of the Y_0.1Ce _x Zr_1−x O_2−δ, La_0.1Ce _x Zr_1−x O_2−δ (x=0.1–0.7), and Y_0.1Pr_0.3Zr_0.6O_2−δ. complex oxide systems were studied using IR and X-ray photoelectron spectroscopies. An appreciable enrichment of the surface of the solids in rare-earth-metal cations (cerium or praseodymium) during the synthesis was revealed. While cations are uniformly spread over the surface of cerium-zirconium solid solutions, the Y_0.1Pr_0.3Zr_0.6O_2−δ surface is covered by the clusters or even a phase of praseodymia. Reductive treatment in hydrogen with subsequent reoxidation results in the segregation of cerium ions on the Y_0.1Ce_0.3Zr_0.6O_2−δ surface at a temperature as low as 770 K. Original Russian Text ? A.N. Kharlanov, L.N. Ikryannikova, V.V. Lunin, A. Yu. Stakheev, 2007, published in Zhurnal Fizicheskoi Khimii, 2007, Vol. 81, No. 7, pp. 1271–1277.     

Preparation and characterization of Ce1−xSmxO2−δ (x = 0.1–0.3) as electrolyte material for intermediate temperature SOFC

The effect of Sm doping on CeO₂ for its use as a solid electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been explored here. Ce_1−xSm_xO_2−δ (x = 0.1–0.3) samples are successfully synthesized by carbonate co-precipitation method. TG–DTA, XRD, Raman, UV–Vis, FT-IR, SEM and ac-impedance are used for structural and electrical characterization. From the XRD patterns, well-crystalline cubic fluorite structured solid solution is confirmed. Lattice parameters increased with increase in Sm³⁺ while the crystallite size decreased. The optical absorption spectra exhibits a red shift for Sm³⁺ doped CeO₂. Raman spectra show an intense peak at 463 cm⁻¹, a characteristic peak for doped ceria. SEM shows cluster like particles. Based on ac-impedance data, the total oxygen ionic conductivity is highest for Ce_0.8Sm_0.2O_2−δ in the temperature range of 473–623 K.     

Vapor phase reduction of cyclohexanone to cyclohexanol on CexZr1-xO2 solid solutions

Reduction of cyclohexanone to cyclohexanol using propane-2-ol as hydrogen donor has been carried out in vapor phase on Ce_xZr_1-xO₂ solid solutions synthesized by ombustion synthesized at 302°C. The solid solutions around 0.4 mol% cerium content show better catalytic activity compared to pure ZrO₂ and the selectivity to cyclohexanol is 98%. A moderate acid-base and good redox properties of Ce_xZr_1-xO₂ solid solutions are seen to be responsible for the catalytic activity. A possible mechanism of hydride transfer has been proposed with cerium ions as promoters. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis, Electrical Properties, and Powder Neutron Crystal Structure Refinement of Pb1−xBixPt2O4 Compounds (0≤x≤0.3)

Substitution of Pb for Bi in the recently characterized mixed-valence lead-platinum oxide PbPt₂O₄ was attempted and a Pb_1−xBi_xPt₂O₄ solid solution was obtained for 0≤x≤0.3. Powder X-ray diffraction study showed that all substituted compounds crystallize with similar triclinic unit cell and PbPt₂O₄ lattice parameters. The structural model of Pb_0.7Bi_0.3Pt₂O₄ was refined from powder X-ray diffraction data using the Rietveld method and the results indicate the same crystal structure than PbPt₂O₄ with one mixed Pb/Bi atomic site. Neutron diffraction realized on the two limit compositions of the solid solution (x=0 and 0.3) allowed to confirm the PbPt₂O₄ and Pb_0.7Bi_0.3Pt₂O₄ stoichiometries. Mean oxidation degree of Pt atoms in the [PtO₄] infinite chains decreases from +3 for PbPt₂O₄ to +2.7 for Pb_0.7Bi_0.3Pt₂O₄. Conductivity measurements show a metallic behavior for all the compositions except the limit composition x=0.3 for which a semiconducting behavior appears.     

Bulk and surface analysis of Ti1–xFexO2/Fe2O3 composites prepared by solid state reaction for photocatalytic applications

Ti_1–xFe_xO₂ / Fe₂O₃ (x = 0.3, 0.6, and 0.7 wt%) composites were prepared by solid state reaction of the oxides TiO₂ (rutile phase) and Fe₂O₃ at 550 °C. The following techniques were applied for the characterization of the composites: X‐ray powder diffraction, Mössbauer spectroscopy, SEM, energy dispersive X‐ray spectroscopy and adsorption of nitrogen. The anatase/rutile/hematite ratio and the abundance of Fe³⁺ were quantified. The results indicate that Fe³⁺ substituted Ti⁴⁺ in the rutile structure and that the α‐Fe₂O₃ phase was predominantly on the surface of the crystalline Ti_1–xFe_xO₂ powders. A substantial increase of the materials density, with respect to rutile, favoured the application of the composites in photocatalytic experiments. The performance of the solids upon the photodegradation of aqueous solutions of carbofuran was evaluated. The Lewis sites created in the composites correlated directly with the photodegradation rate constant of carbofuran and the decrease of the total organic carbon content in the treated solutions. Copyright © 2011 John Wiley & Sons, Ltd.