Epitaxial Growth of CeO<Subscript>2</Subscript>/YSZ/CeO<Subscript>2</Subscript> Buffer Layers on Textured Ni Substrates for YBCO Conductors

CeO₂/YSZ/CeO₂ buffer layers were deposited on textured Ni substrates byin situ pulsed laser deposition. The out-of-plane texture and in-plane texture of the buffer layers were characterized by X-ray diffraction ω-scans and ϕ-scans. Using this CeO₂/YSZ/CeO₂ architecture as the buffer layers, high quality YBCO films with a zero-resistanceT _c about 90 K and a self-field critical current densitiesJ _c above 10⁶ A/cm² at 77 K can be obtained on Ni substrates.     

Infrared to visible upconversion luminescence in Er/Yb co-doped CeO2 inverse opal

Infrared to visible upconversion luminescence has been investigated in Er³⁺/Yb³⁺ co-doped CeO₂ inverse opal. Under the excitation of 980 nm diode lasers, visible emissions centered at 525, 547, 561, 660 and 680 nm are observed, which are assigned to the Er³⁺ transitions of ²H_11/2 → ⁴I_15/2 (525 nm), ⁴S_3/2 → ⁴I_15/2 (547, 561 nm), ⁴F_9/2 → ⁴I_15/2 (660 and 680 nm), respectively. The effect of photonic band gap on the upconversion luminescence intensity was also obtained. Additionally, the upconversion luminescence mechanism was studied. The dependence of Er³⁺ upconversion emission intensity on pump power reveals that it is a two-photon excitation process.     

Hydrothermal synthesis of CeO2 nano-octahedrons

CeO₂ nano-octahedrons were synthesized with a facile hydrothermal synthesis process where Ce(NO₃)₃·6H₂O and urea were used as a cerium resource and mineralizer respectively and no surfactant or template was applied. The effects of synthesis parameters such as reaction temperature, reaction time, as well as the dosages of Ce (NO₃)₃·6H₂O and urea were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis were conducted to characterize the crystalline and morphology of the obtained CeO₂ powders. The optimal reaction condition to prepare the CeO₂ of the desired fluorite structure was established. The possible mechanism of synthesis of CeO₂ with a nano-octahedron morphology was illustrated.     

Hydrothermal synthesis of monodisperse CeO2 nanocubes

Monodisperse CeO₂ nanocubes have been fabricated via an acrylamide-assisted hydrothermal route. NH₃ and acrylic acid from the hydrolysis of acrylamide act as OH⁻ provider and capping reagent, respectively. The structure and morphology of the products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FE-SEM) and Fourier transformed infrared (FT-IR). The products have a cubic morphology with a mean size of 200 nm. The possible formation mechanism has been discussed based on the experimental results.     

Microstructure of YBCO bulk superconductors with CeO2 addition

The refinement of Y₂BaCuO₅ (Y211) particles by CeO₂ in the single-grain YBa₂Cu₃O₇/Y₂BaCuO₅ (Y123/Y211) bulk superconductors of nominal composition Y_1.5Ba₂Cu₃O_x prepared by top-seeded melt-growth process with Y₂O₃ addition has been studied by polarised light microscopy. It is shown that cerium is active in the Y211 particle refinement when it is solved in the peritectic melt, L_p. Observed growth of Y211 particles during sintering stage is ascribed to higher amount of melt induced by CeO₂ reaction with Y123 phase producing barium cerate and CuO.     

Synthesis and characterization of stable and crystalline Ce0.6Y0.4O1.8 nanoparticle sol

Ce_0.6Y_0.4O_1.8 (40YCO) nanoparticle sol was synthesized via the hydrolysis of a Ce-Y-triethanolamine (TEA) complex derived from the reaction of hydrate cerium (III) nitrate (Ce(NO₃)₃·6H₂O), yttrium nitrate (Y(NO₃)₃·6H₂O) and TEA in alcohol solution at room temperature. The resultant sol possessed excellent UV shielding ability and high transparency in visible light region, and can be stable for one month. Transmission electron microscopy (TEM) showed a particle size distribution of 4.1 ± 0.7 nm for 40YCO. X-ray diffraction (XRD) as well as selected area electron diffraction (SAED) gave evidence that the as-synthesized nanoparticles were well crystalline. The formation of a solid solution was monitored by XRD and ICP-MS. Moreover, zeta potential measurement and infrared spectra were employed to study the YCO particles.     

3D navicular ceria micro/nanocomposite structure with multi-layered arrangement and its application in CO oxidation

In this work, novel three-dimensional (3D) navicular ceria micro/nanocomposite architecture with multi-layered structure was synthesized for the first time via solution reaction followed by a simple hydrothermal treatment in the presence of lysozyme. During the synthesis procedure, a 3D navicular ceria precursor (Ce₂O(CO₃)₂·H₂O) with multi-layered structure was obtained after hydrothermal treatment at 100 °C for 10 h. Ceria with the same morphology can be obtained after thermal decomposition of this Ce₂O(CO₃)₂·H₂O precursor. Structural properties of the products were characterized by XRD, TG-DTA, FT-IR, SEM, TEM, and N₂-sorption techniques. Then a possible layer-by-layer electrostatic self-assembled growth mechanism was proposed for the formation of this 3D navicular architecture based on the experimental results and detail analysis of the evolution process of ceria precursors. Furthermore, a mold reaction of the catalytic oxidation of CO was conducted on the as-obtained CeO₂ and gold supported catalyst, both showed excellent activity and durability for CO conversion.     

Surface and grain-boundary energies as well as surface mass transport in polycrystalline CeO2

The multiphase equilibration technique for the determination of the equilibrium angles that develop at the interphase boundaries of a solid–liquid–vapor system, has been used to calculate the surface and interfacial energies in polycrystalline CeO₂ and CeO₂/Cu system in argon atmosphere at the temperature range 1473–1773 K. Linear temperature functions were obtained by extrapolation, for the surface energy γ_sv (J/m²) = 2.465–0.563 × 10⁻³ T and the grain-boundary energy γ_ss (J/m²) = 1.687–0.391 × 10⁻³ T of the ceramic, as well as for the interfacial energy γ_sl (J/m²) = 2.623–1.389 × 10⁻³(T −1356 K) of the CeO₂/Cu system. Grain-boundary grooving studied on polished surfaces of CeO₂ annealed in argon atmosphere at the same temperature range has shown that surface diffusion was the dominant mechanism for the mass transport. The surface diffusion coefficient can be expressed according to the equation D_s (m²/s) = 3.82 × 10⁻⁴ exp(−308,250/RT).     

Metal oxide–chitosan based nanocomposite for cholesterol biosensor

Metal oxide [cerium oxide (NanoCeO₂)]–chitosan (CH) nanocomposite film has been fabricated onto indium-tin-oxide (ITO) coated glass plate to immobilize cholesterol oxidase (ChOx) via physiosorption for cholesterol detection. Electrochemical studies reveal that the presence of NanoCeO₂ in CH–CeO₂ nanocomposite results in increased electroactive surface area for ChOx loading resulting in enhanced electron transport between ChOx and electrode. The ChOx/CH–NanoCeO₂/ITO bioelectrode exhibits interesting characteristics such as detection range of 10–400 mg/dL, detection limit of 5 mg/dL, response time of 10 s, low K_m value of 3.5 mg/dL and value of regression coefficient of 0.994.     

Novel synthesis of nanocrystalline CeO2 by mechanochemical and water-in-oil microemulsion methods

Nanocrystalline cerium dioxide (CeO₂) had been synthesized by two different methods which were mechanochemical and water-in-oil microemulsion. Effects of synthesis conditions on properties of nanocrystalline cerium dioxide were investigated. X-ray diffraction (XRD) was used to characterize the phase and crystallite size of synthesized cerium dioxide nanoparticles. XRD results showed that face centered cubic CeO₂ nanoparticles with crystallite size in nanometer scale were formed. The crystallinity increased with increasing annealing temperature. The average specific surface area of the particles was probed using gas adsorption-desorption measurements. The average particles size was calculated from the specific surface area and was determined to be 5.2 nm for microemulsion samples and 6.9 nm for mechanochemical samples. These results showed that properties of synthesized cerium dioxide could be tailored by adjusting the synthesis conditions.     

The heterostructured AAO/CeO2 nanosystem fabricated by electrodeposition for charge storage and hydrophobicity

Tilted cathode was adopted to prepare porous anodic alumina membrane (PAAM) during the second aluminum anodic oxidation (AAO). A heterostructured AAO/CeO₂ nanosystem was fabricated by filling CeO₂ into the PAAM by electrochemical deposition. The larger the intersection angle of the cathode, the more the charge storage of the fabricated system. A lower potential scan rate is beneficial to the electrochemical charge storage of the system. With the cathode intersection angle increasing, the hydrophobicity of the AAO/CeO₂ system is greatly improved. As the 40° is the optimum angle, the charge storage and hydrophobicity of the system increase with the increasing cathode intersection angle up to 40°. The AAO/CeO₂ system could be utilized in both charge storage and self-cleaning.     

Graphene oxide (GO) doped CeO2 as potential enhancer of methyl orange degradation

In this article, a simple method for the synthesis of Graphene Oxide-Cerium oxide (GO/CeO₂) is carried out. The prepared sample was characterized in detail, such as scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman, Brunauer-Emmett-Teller technology N₂ adsorption-desorption analysis (BET), photoluminescence (PL) and UV-visible diffuse reflectance spectroscopy (DRS). It was indicated that GO was successfully incorporated into CeO₂. The photocatalytic mechanism of GO/CeO₂ was also explained. The MO solution catalyzed by CeO₂ and GO/CeO₂ was analyzed by a UV-visible spectrometer. The efficiency of GO/CeO₂ degrading methyl orange (MO) is improved from 50% to 87% compared to pure CeO₂ under the visible light. GO/CeO₂ exhibited better photocatalytic performance than CeO₂, which indicated GO doping improved the photocatalytic capacity of the CeO₂ catalyst. It may have potential applications in addressing environmental wastewater.     

Preparation of an Alkali-Element or Alkali-Earth-Element-Doped CeO2–Sm2O3 System and Its Operation Properties as the Electrolyte in Planar Solid Oxide Fuel Cells

Ceria–samaria (CeO₂–Sm₂O₃) is one of the most interesting fluorite oxides since its ionic conductivity is higher than that of yttria-stabilized zirconia in air. However, these CeO₂ -based oxides are partially reduced and develop electronic conductivity under fuel cell operating conditions. In their application to the SOFC system, their current densities and power densities are not at a satisfactory level. For the development of high-performance CeO₂ electrolytes, it is important that the fluorite lattice of CeO₂-based oxide be improved from the viewpoint of crystallography. In this study, it is assumed that the reduction of Ce⁴⁺ in the fluorite lattice was inhibited by expansion of the CeO₂ lattice. In order to investigate the contribution of the expanded CeO₂ lattice to reduction resistance, CeO₂–Sm₂O₃ solid solution, calcia-doped CeO₂–Sm₂O₃ solid solution, and a small amount of alkali element-doped CeO₂–Sm₂O₃ -based oxide were prepared for comparison. It was found that the calcia or a small amount of alkali element-doped CeO₂ solid solution enhanced the oxide ionic conductivity. The power density of the latter showed a high value at 800°C. It is concluded that the improved fuel cell performance can be attributed to the good reduction resistance in the fuel cell atmosphere.     

大比表面积、高孔隙率多孔仿生CeO2-CuO光催化剂

以富含多孔结构的纤维素为诱导体,采用浸渍法制备仿生CeO_2-CuO催化材料,通过X射线衍射(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、氮气吸附-脱附(N2adsorption-desorption)、紫外-可见漫反射光谱(UV-vis)等分析手段对产物的结构和形貌进行了表征。在可见光条件下,以亚甲基蓝溶液为模拟废水,测试其TOC(Total organic carbon)去除率,并对光催化降解机理进行探讨。实验结果表明所制备的材料颗粒均匀,平均颗粒尺寸在10nm左右,并且含有丰富的介孔结构,其孔径集中分布于5~10nm。由紫外-可见漫反射吸收光谱可知,材料对可见光的吸收程度高于块状氧化铈,从而具有更高的可见光催化活性,光照2.5h后对亚甲基蓝的TOC去除率为90%。     

Synthesis of ordered mesoporous CuO/CeO2 composite via co-nanocasting replication method and its improved reactivity towards hydrogen

Ordered mesoporous CuO/CeO₂ composites with cubic Ia3d or 2-D hexagonal p6mm structure have been synthesized by a co-nanocasting-replication method using mesoporous silica KIT-6 or SBA-15 as hard template. XRD, TEM, N₂-adsorption and H₂-TPR techniques were used for the structural analysis and catalytic activity characterization. The results indicated that the high surface area mesoporous CuO/CeO₂ composites with different amounts of CuO addition were well-crystallized and exhibited much improved reactivity towards hydrogen than pure mesoporous CeO₂, and the CuO/CeO₂ composite with 20 wt.% CuO addition possessed the highest reactivity towards hydrogen. The enhanced H₂-TPR property could be attributed to the synergetic catalytic effects between copper oxide and cerium oxide.     

Interaction mediated by size differences between Y2BaCuO5 and CeO2 particles in melt-textured YBCO superconductors

The Refining of Y₂BaCuO₅ (Y211) is crucial in the fabrication of YBa₂Cu₃O_x (Y123) bulk superconductors with a high critical current density (J_c) for power engineering applications.In this work, the influence of an addition of Y211 and CeO₂ of different sizes on the Y211 refinement and superconducting properties of melt-textured Y123 superconductors is investigated. Nano-size Y211 and nano-size CeO₂ were prepared by attrition-milling (250 rpm and 2 h). Using mixed powders consisting of 85 wt.% Y123, 15 wt.% Y211, and 1 wt.% CeO₂, Y123 quasi-single crystals were fabricated via a top seed melt-textured growth process. The interaction between Y211 and CeO₂ of different particle sizes was examined in terms of the size, uniformity and density of the Y211 particles that existed in the melt-textured samples. The reaction between the nano-size Y211 and the nano-size CeO₂ was more violent due to the more frequent collisions compared to the other reactions (micro-size Y211/nano-size CeO₂ or micro-size Y211/micro-size CeO₂), resulting in the most effective for refinement of Y211 particles and the best J_c value of 4.2 × 10⁴ (A/cm²) (at 77 K and a zero-field).     

Photocatalytic degradation of C.I. Direct Red 23 in aqueous solutions under UV irradiation using SrTiO3/CeO2 composite as the catalyst

The photocatalytic degradation of C.I. Direct Red 23 (4BS) in aqueous solutions under UV irradiation was investigated with SrTiO3/CeO2 composite as the catalyst. The SrTiO3/CeO2 powders had more photocatalytic activity for decolorization of 4BS than that of pure SrTiO3 powder under UV irradiation. The effects of catalytic dose, pH value, initial concentration of dye, irradiation intensity as well as scavenger KI were ascertained, and the optimum conditions for maximum degradation were determined. Under the irradiation of a 250 W mercury lamp, the best catalytic dose was 1.5 g/L and the best pH was 12.0. Light intensity exhibited a significant positive effect on the efficiency of decolorization, whereas the initial dye concentration showed a significant negative effect. Under the conditions of a catalytic dose of 1.5 g/L, pH of 12.0, initial dye concentration of 100mg/L, light intensity of 250 W, and air flow rate of 0.15 m3/h, complete decolorization, as determined by UV-visible analysis, was achieved in 60 min, corresponding to a reduction in chemical oxygen demand (COD) of 69% after a 240 min reaction. A tentative degradation pathway based on the sensitization mechanism of photocatalysis is proposed.     

碳纤维颗粒增强CeO2/PMMA/PVDF超疏水复合涂层及其耐磨性能

提高耐磨性能是推动仿生超疏水表面走向实际应用的关键挑战之一。设计了二氧化铈微米粒子增强PMMA/PVDF超疏水复合涂层配方,获得了水珠接触角达152°、水珠滚动角为5°的超疏水复合涂层。该涂层经过落砂磨损试验后接触角下降为103°、滚动角增大为20°。采用碳纤维颗粒对CeO2/PMMA/PVDF超疏水复合涂层进行增强,优化配方的接触角达153°、滚动角达到5°。经过相同落砂磨损试验后,增强后的复合涂层水珠接触角能在一定程度磨损后达到140°左右。可见,CeO2/PMMA/PVDF复合涂层具有良好的超疏水性能,碳纤维颗粒增强是提高该涂层耐磨性能的有效方法。