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Sample records for ceo2 single buffer

  1. The influence of impurity on the critical thickness of the CeO2 buffer layer for coated conductors

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The lattice parameters, band structure, density of state and elastic constant of RE-doped CeO2 (RE=Sm, Gd, Dy), the buffer material for coated HTS conductors, are calculated using the plane-wave method with pseudopotentials based on the density functional theory (DFT) of first-principle. The rule and mechanism of the effect of rare earth impurity on the critical thickness of the CeO2 buffer layer are investigated. It is found that, in the range of the calculation, the changes of the lattice volume V and elastic constant E of CeO2 with the impurity are mainly determined by the increased electrons ne of the system. The relationship of the elastic constant E and increased electrons ne is established. It is indicated that the critical thickness of the CeO2 single buffer layer doped with Sm, Gd, and Dy may be enhanced by 22%, 43% and 33%, respectively.

  2. Investigation of CeO2 Buffer Layer Effects on the Voltage Response of YBCO Transition-Edge Bolometers

    DEFF Research Database (Denmark)

    Mohajeri, Roya; Nazifi, Rana; Wulff, Anders Christian

    2016-01-01

    The effect on the thermal parameters of superconducting transition-edge bolometers produced on a single crystalline SrTiO3 (STO) substrate with and without a CeO2 buffer layer was investigated. Metal-organic deposition was used to deposit the 20-nm CeO2 buffer layer, whereas RF magnetron sputtering...... responses, and the results were compared with that of simulations conducted by applying a one-dimensional thermophysical model. It was observed that adding the buffer layer to the structure of the bolometer results in an increased response at higher modulation frequencies. Results from simulations made...

  3. The influence of impurity on the critical thickness of the CeO2 buffer layer for coated conductors

    Institute of Scientific and Technical Information of China (English)

    PAN Min; HUANG Zheng; MA HuanFeng; QIANG WeiRong; WEI LianFu; WANG Long; ZHAO Yong

    2009-01-01

    The lattice parameters, band structure, density of state and elastic constant of RE-doped CeO2 (RE=Sm, Gd, Dy), the buffer material for coated HTS conductors, are calculated using the plane-wave method with paeudopotentials based on the density functional theory (DFT) of first-principle. The rule and mechanism of the effect of rare earth impurity on the critical thickness of the CeO2 buffer layer are in-vestigated. It is found that, in the range of the calculation, the changes of the lattice volume Ⅴ and elastic constant E* of CeO2 with the impurity are mainly determined by the increased electrons △ne of the system. The relationship of the elastic constant E* and increased electrons △ne is established. It is indicated that the critical thickness of the CeO2 single buffer layer doped with Sm, Gd, and Dy may be enhanced by 22%, 43% and 33%, respectively.

  4. Preparation and Characterization of CeO2/YSZ/CeO2 Buffer Layers for YBCO Coated Conductors

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    CeO2 seed layer was deposited on rolling-assisted biaxially textured metal substrates by direct-current (DC) magnetron reactive sputtering. The effect of deposition temperature on epitaxial orientation of CeO2 thin films was examined. High quality CeO2 layers were achieved at deposition temperature from 750℃ to 850℃.Subsequently yttria-stabilized zirconia (YSZ) and CeO2 films were deposited to complete the buffer layer structure via the same process. The best samples exhibited a highly biaxial texture, as indicated by FWHM (full width half maximum) values in the range of 4°-5°, and 2°-4° for in-plane and out-of-plane orientations,respectively. Secondary ion mass spectrometer analysis confirmed the effective prevention of buffer layer against Ni and W metal interdiffusion. Atomic force microscope observations revealed a smooth, dense and crack-free surface morphology, which provided themselves as the good buffer structure to the YBa2Cu3O7-δ(YBCO) coated conductors.

  5. Experimental evidence for self-assembly of CeO2 particles in solution: Formation of single-crystalline porous CeO2 nanocrystals

    DEFF Research Database (Denmark)

    Tan, Hui Ru; Tan, Joyce Pei Ying; Boothroyd, Chris

    2012-01-01

    Single-crystalline porous CeO2 nanocrystals, with sizes of ∼20 nm and pore diameters of 1-2 nm, were synthesized successfully using a hydrothermal method. Using electron tomography, we imaged the three-dimensional structure of the pores in the nanocrystals and found that the oriented aggregation...

  6. Fabrication of Ni-5 at. %W Long Tapes with CeO2 Buffer Layer by Reel-to-Reel Method

    DEFF Research Database (Denmark)

    Ma, Lin; Tian, Hui; Yue, Zhao

    2015-01-01

    A 10-m-long homemade textured Ni-5at.%W (Ni5W) long tape with a CeO2 buffer layer has been prepared successfully by means of rolling-assisted biaxially textured substrate (RABiTS) route followed by a chemical solution deposition method in a reel-to-reel manner. Globally, the Ni5W substrate and CeO2...... film exhibit high homogeneity in terms of biaxial texture over the tape. The average values of full width at half maximum of in-plane and out-of-plane texture are 7.2° and 6.1° in Ni5W substrate, 7.6° and 6.1° in CeO2 buffer layer, respectively, all of those with a small standard deviation...

  7. Cube Texture Formation of Cu-33at.%Ni Alloy Substrates and CeO2 Buffer Layer for YBCO Coated Conductors

    DEFF Research Database (Denmark)

    Tian, Hui; Li, Suo Hong; Ru, Liang Ya;

    2014-01-01

    Cube texture formation of Cu-33 at.%Ni alloy substartes and CeO2 buffer layer prepared by chemical solution deposition on the textured substrate were investigated by electron back scattered diffraction (EBSD) and XRD technics systematically. The results shown that a strong cube textured Cu-33at.%...

  8. Characterization of a strongly textured non-ferromagnetic Cu-33 at%Ni substrate coated with a CeO2 buffer layer

    DEFF Research Database (Denmark)

    Tian, Hui; Suo, H.L.; Yue, Zhao

    2013-01-01

    the fraction of the cube {001}〈100〉 texture is 99.8% and the fraction of boundary misorientations with angles greater than 10 is only 5%. The material is shown to be non-ferromagnetic at typical operating temperatures for coated conductors. Furthermore, it is shown that a CeO2 buffer layer can be successfully...

  9. High-Performance Ru1 /CeO2 Single-Atom Catalyst for CO Oxidation: A Computational Exploration.

    Science.gov (United States)

    Li, Fengyu; Li, Lei; Liu, Xinying; Zeng, Xiao Cheng; Chen, Zhongfang

    2016-10-18

    By means of density functional theory computations, we examine the stability and CO oxidation activity of single Ru on CeO2 (111), TiO2 (110) and Al2 O3 (001) surfaces. The heterogeneous system Ru1 /CeO2 has very high stability, as indicated by the strong binding energies and high diffusion barriers of a single Ru atom on the ceria support, while the Ru atom is rather mobile on TiO2 (110) and Al2 O3 (001) surfaces and tends to form clusters, excluding these systems from having a high efficiency per Ru atom. The Ru1 /CeO2 exhibits good catalytic activity for CO oxidation via the Langmuir-Hinshelwood mechanism, thus is a promising single-atom catalyst.

  10. Comparison of the effects of platinum and CeO2 on the properties of single grain, Sm-Ba-Cu-O bulk superconductors

    Science.gov (United States)

    Zhao, Wen; Shi, Yunhua; Radušovská, Monika; Dennis, Anthony R.; Durrell, John H.; Diko, Pavel; Cardwell, David A.

    2016-12-01

    SmBa2Cu3O7-δ (Sm-123) is a light-rare-earth barium-cuprate (LRE-BCO) high-temperature superconductor (HTS) with significant potential for high field industrial applications. We report the fabrication of large, single grain bulk [Sm-Ba-Cu-O (SmBCO)] superconductors containing 1 wt% CeO2 and 0.1 wt% Pt using a top-seeded melt growth process. The performance of the SmBCO bulk superconductors containing the different dopants was evaluated based on an analysis of their superconducting properties, including critical transition temperature, T c and critical current density, J c , and on sample microstructure. We find that both CeO2 and Pt dopants refine the size of Sm2BaCuO5 (Sm-211) particles trapped in the Sm-123 superconducting phase matrix, which act as effective flux pinning centres, although the addition of CeO2 results in broadly improved superconducting performance of the fully processed bulk single grain. However, 1 wt% CeO2 is significantly cheaper than 0.1 wt% Pt, which has clear economic benefits for use in medium to large scale production processes for these technologically important materials. Finally, the use of CeO2 results generally in the formation of finer Sm-211 particles and to the generation of fewer macro-cracks and Sm-211 free regions in the sample microstructure.

  11. 采用低 F 工艺在低碳残留 La2Zr2O7/CeO2缓冲层上沉积 YBCO 膜%Fabrication of YBCO Film on the La 2 Zr 2 O 7/CeO 2 Buffer Layer with Little Residual Carbon by a Low F Content Deposition Process

    Institute of Scientific and Technical Information of China (English)

    贾佳林; 王辉; 李成山; 王耀; 金利华; 吕建凤; 许征兵

    2015-01-01

    In this paper, the La2 Zr2 O7 (LZO) / CeO2 buffer layer and superconducting layer with bi-layer membrane structure were fabricated on the NiW baseband of bi-axial texture by the chemical solution method. In the buffer layer deposition process, the carbon residue among them was reduced by mixing with CO2 in the annealing atmosphere, and the deposition of YB-CO superconducting layer was carried out by the Low F content deposition process. The texture and morphology of the prepared samples were characterized by X ray diffraction (XRD) and scanning electron microscopy (SEM), and the electrical properties of the samples were tested. The result indicates that mixing with a small amount of weakly oxidizing gases did not destroy the texture and morphology of the buffer layer while removing residual carbon in the buffer lay-er. However, the YBCO layer deposited on the flat surface of the buffer layer showed a sharp bi-axial texture and good superconductivity, and this process can be further transplanted into the process of long length baseband preparation.%采用化学溶液法在双轴织构的 NiW 基带上制备了双层膜结构的 La2 Zr2 O7(LZO)/ CeO2缓冲层和超导层,在缓冲层沉积过程中通过在退火气氛中混入 CO2降低其中的碳残留量,YBCO 超导层的沉积则是通过低 F 工艺进行的。利用 X 射线衍射(XRD)和扫描电镜(SEM)对所制得样品的织构和表面形貌进行了表征,并测试了样品的电性能。结果表明,少量弱氧化性气体的混入在除去缓冲层中残留碳的同时并没有破坏缓冲层的织构和形貌。而在平整的缓冲层表面沉积的 YBCO 层显示出了锐利的双轴织构和良好的超导电性,该工艺可以进一步移植到长带制备过程中。

  12. Development of One Meter Long Double-Sided CeO2 Buffered Ni-5at.%W Templates by Reel-to-Reel Chemical Solution Deposition Route

    DEFF Research Database (Denmark)

    Yue, Zhao; Konstantopoulou, K.; Wulff, Anders Christian

    2013-01-01

    High performance long-length coated conductors fabricated using various techniques have attracted a lot of interest recently. In this work, a reel-to-reel design for depositing double-sided coatings on long-length flexible metallic tapes via a chemical solution method is proposed and realized....... The major achievement of the design is to combine the dip coating and drying processes in order to overcome the technical difficulties of dealing with the wet films on both sides of the tape. We report the successful application of the design to fabricate a one-meterlong double side coated CeO2/Ni − 5at...... layer are 7.2◦ and 5.8◦ with standard deviation of 0.26◦ and 0.34◦, respectively, being indicative of the high quality epitaxial growth of the films prepared in the continuous manner. An all chemical solution derived YBCOLow−TFA/Ce0.9La0.1O2/Gd2Zr2O7/CeO2 structure is obtained on a short sample...

  13. CeO2 as insulation layer in HTc superconducting multilayer and cross over structures

    NARCIS (Netherlands)

    Wijck, van M.A.A.M.; Verhoeven, M.A.J.; Reuvekamp, E.M.C.M.; Gerritsma, G.J.; Blank, D.H.A.; Rogalla, H.

    1996-01-01

    We present a study of the electrical properties of insulating CeO2 layers in combination with superconducting (Y/Dy) Ba2Cu3O7-delta (RBCO) films over ramps and in crossover structures. CeO2 is frequently used as a buffer layer, or template layer for biepitaxial grain boundary junctions, but can als

  14. Research on CeO2 cap layer for YBCO-coated conductor

    Institute of Scientific and Technical Information of China (English)

    Shi Dong-Qi; Ma Ping; Ko Rock-Kil; Kim Ho-Sup; Chung Jun-Ki; Song Kyu-Jeong; Park Chan

    2007-01-01

    Two groups of coated conductor samples with different thicknesses of CeO2 cap layers deposited by pulsed laser deposition (PLD) under the same conditions have been studied. Of them, one group is of CeO2 films, which are deposited on stainless steel (SS) tapes coated by IBAD-YSZ (IBAD-YSZ/SS), and the other group is of CeO2/YSZ/Y2O3 multilayers, which are deposited on NiW substrates by PLD for the fabrication of YBCO-coated conductor through the RABiTS approach. YBCO film is then deposited on the tops of both types of buffer layers by PLD. The effects of the thickness of the CeO2 film on the texture of the CeO2 film and the critical current density (Jc) of the YBCO film are analysed. For the case of CeO2 film on IBAD-YSZ/SS, there appears a self-epitaxy effect with increasing thickness of the CeO2 film. For CeO2/YSZ/Y2O3/NiW, in which the buffer layers are deposited by PLD, there occurs no self-epitaxy effect, and the optimal thickness of CeO2 is about 50nm. The surface morphologies of the two groups of samples are examined by SEM.

  15. Growth and Photoluminescence of Epitaxial CeO2 Film on Si (111) Substrate

    Institute of Scientific and Technical Information of China (English)

    GAO Fei; ZHANG Jian-Hui; QIN Fu-Guang; YAO Zhen-Yu; LIU Zhi-Kai; WANG Zhan-Guo; LIN Lan-Ying

    2001-01-01

    A CeO2 film with a thickness of about 80nm was deposited by a mass-analysed low-energy dual ion beam deposition technique on an Si(111) substrate. Reflection high-energy electron diffraction and x-ray diffraction measurements showed that the film is a single crystal. The tetravalent state of Ce in the film was confirmed by xray photoelectron spectroscopy measurements, indicating that stoichiometric CeO2 was formed. Violet/blue light emission (379.5 nm) was observed at room temperature, which may be tentatively explained by charge transitions from the 4f band to the valence band of CeO2.

  16. Rare earth metal doped CeO2-based catalytic materials for diesel soot oxidation at lower temperatures

    Institute of Scientific and Technical Information of China (English)

    A Rangaswamy; Putla Sudarsanam; Benjaram M Reddy

    2015-01-01

    In this work, the influence of trivalent rare-earth dopants (Sm and La) on the structure-activity properties of CeO2 was thor-oughly studied for diesel soot oxidation. For this, an optimized 40%of Sm and La was incorporated into the CeO2 using a facile co-precipitation method from ultra-high dilute aqueous solutions. A systematic physicochemical characterization was carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), Brumauer-Emmett-teller method (BET) surface area, X-ray pho-toelectron spectroscopy (XPS), Raman, and H2-temperature programmed reduction (TPR) techniques. The soot oxidation efficiency of the catalysts was investigated using a thermogravimetric method. The XRD results suggested the formation of nanocrystalline sin-gle phase CeO2-Sm2O3 and CeO2-La2O3 solid solutions. The Sm-and La-doped CeO2 materials exhibited smaller crystallite size and higher BET surface area compared with the pure CeO2. Owing to the difference in the oxidation states of the dopants (Sm3+and La3+) and the Ce4+, a number of oxygen vacancies were generated in CeO2-Sm2O3 and CeO2-La2O3 samples. The H2-TPR studies evidenced the improved reducible nature of the CeO2-Sm2O3 and CeO2-La2O3 samples compared with the CeO2. It was found that the addition of Sm and La to the CeO2 outstandingly enhanced its catalytic efficiency for the oxidation of diesel soot. The observed 50%soot con-version temperatures for the CeO2-Sm2O3, CeO2-La2O3 and CeO2 were~790, 843 and 864 K (loose contact), respectively, and similar activity order was also found under the tight contact condition. The high soot oxidation efficacy of the CeO2-Sm2O3 sample was at-tributed to numerous catalytically favourable properties, like smaller crystallite size, larger surface area, abundant oxygen vacancies, and superior reducible nature.

  17. Synthesis and characterization of nanostructured CeO2 with dyes adsorption property

    Directory of Open Access Journals (Sweden)

    Oman Zuas

    2014-03-01

    Full Text Available The nanostructured cerium dioxide (CeO2 has been successfully fabricated using a simple precipitation method. Its characteristics were evaluated using TG-DTA, DR-UV-Vis, XRD, FTIR and TEM. The results showed that the nanostructured CeO2 has high purity and good crystalline nature, with face centered cubic (fcc phase and the average diameter of CeO2 single crystal about 14 nm. Performance evaluation of the synthesized CeO2 samples showed that the nanostructured CeO2 has a strong adsorption toward acid orange-10 (AO-10 and congo red (CR in aqueous solution. Under given experimental conditions (dye concentration of 15 mg/l, adsorbent dosage of 1 g/l, reaction temperature of 30 ± 1 °C, it was estimated that the adsorption equilibrium for AO-10 and CR occurred at 60 min and 90 min of reaction time, respectively, with total removal of 96.82% for AO-10 dye and 93.55% for CR dye. The results suggested that the CeO2 nanopowder could be potentially used as an efficient adsorbent for the removal of synthetic organic dyes in aqueous solution and may address for future concern in the area.

  18. X-ray photoelectron spectroscopy study of high-k CeO2/La2O3 stacked dielectrics

    Directory of Open Access Journals (Sweden)

    Jieqiong Zhang

    2014-11-01

    Full Text Available This work presents a detailed study on the chemical composition and bond structures of CeO2/La2O3 stacked gate dielectrics based on x-ray photoelectron spectroscopy (XPS measurements at different depths. The chemical bonding structures in the interfacial layers were revealed by Gaussian decompositions of Ce 3d, La 3d, Si 2s, and O 1s photoemission spectra at different depths. We found that La atoms can diffuse into the CeO2 layer and a cerium-lanthanum complex oxide was formed in between the CeO2 and La2O3 films. Ce3+ and Ce4+ states always coexist in the as-deposited CeO2 film. Quantitative analyses were also conducted. The amount of CeO2 phase decreases by about 8% as approaching the CeO2/La2O3 interface. In addition, as compared with the single layer La2O3 sample, the CeO2/La2O3 stack exhibits a larger extent of silicon oxidation at the La2O3/Si interface. For the CeO2/La2O3 gate stack, the out-diffused lanthanum atoms can promote the reduction of CeO2 which produce more atomic oxygen. This result confirms the significant improvement of electrical properties of CeO2/La2O3 gated devices as the excess oxygen would help to reduce the oxygen vacancies in the film and would suppress the formation of interfacial La-silicide also.

  19. Facile hydrothermal synthesis of CeO2 nanopebbles

    Indian Academy of Sciences (India)

    N Sabari Arul; D Mangalaraj; Jeong In Han

    2015-09-01

    Cerium oxide (CeO2) nanopebbles have been synthesized using a facile hydrothermal method. X-ray diffraction pattern (XRD) and transmission electron microscopy analyses confirm the presence of CeO2 nanopebbles. XRD shows the formation of cubic fluorite CeO2 and the average particle size estimated from the Scherrer formula was found to be 6.69 nm. X-ray absorption spectrum of CeO2 nanopebbles exhibits two main sharp white lines at 880 and 898 eV due to the spin orbital splitting of 4 and 5. Optical absorption for the synthesized CeO2 nanopebbles exhibited a blue shift (g = 3.35 eV) with respect to the bulk CeO2 (g = 3.19 eV), indicating the existence of quantum confinement effects.

  20. Single-Crystalline CeOHCO3 with Rhombic Morphology:Synthesis and Thermal Conversion to CeO2%单晶菱形CeOHCO3片状物的制备及其向CeO2的热转换

    Institute of Scientific and Technical Information of China (English)

    张泽芳; 俞磊; 刘卫丽; 宋志棠

    2011-01-01

    Single-crystalline CeOHCO3 rhombic micro-plates with an orthorhombic structure were synthesized by the precipitation reaction between (NH4)2Ce(NO3)6 and CO(NH)2 in the presence of 3-aminopropyltriethoxysilane (APS). Polycrystalline CeO2 rhombic micro-plates were prepared by thermal decomposition of single-crystalline CeOHCO3 rhombic micro-plates at 600 ℃ in air. CeOHCO3 and CeO2 rhombic micro-plates were characterized by XRD, filed-emission scanning electron microscopy (FESEM), TEM, and XPS. The results indicate that APS plays an important role in the preparation of single-crystalline CeOHCO3 rhombic micro-plates because the CeO2 is produced without APS. In addition, the rhombic shape of the products is not ruined apparently by the thermal conversion process from CeOHCO3 to CeO2.%以硝酸铈铵和尿素为反应物,γ-氨丙基三乙氧基硅烷(KH550)为助剂,通过沉淀反应制得了单晶菱形CeOHCO3片状物.然后将CeOHCO3在600℃空气气氛中灼烧获得了菱形CeO2.通过XRD和SEM对反应物中是否含有KH550助剂所得的产物进行了分析,结果发现只有含有KH550才能获得菱形CeOHCO3片状物,并且在灼烧过程中产物的形貌仍保持菱形.然后采用TEM对菱形CeOHCO3和CeO2进行了表征,结果发现CeOHCO3为单晶产物而灼烧后所得的CeO2为多晶产物.

  1. Lattice-matched Cu2ZnSnS4/CeO2 solar cell with open circuit voltage boost

    DEFF Research Database (Denmark)

    Crovetto, Andrea; Yan, Chang; Iandolo, Beniamino;

    2016-01-01

    We report a reproducible enhancement of the open circuit voltage in Cu2ZnSnS4 solar cells by introduction of a very thin CeO2 interlayer between the Cu2ZnSnS4 absorber and the conventional CdS buffer. CeO2, a non-toxic earth-abundant compound, has a nearly optimal band alignment with Cu2ZnSnS4...

  2. Catalytic Reduction of SO2 on CeO2-La2O3 Rare Earth Mixed Compounds

    Institute of Scientific and Technical Information of China (English)

    胡辉; 李劲; 程国宏; 李胜利

    2004-01-01

    Adding rare earth oxide CeO2 with variable valences to La2O3 formed a mixture of rare earth oxides. By means of dipping CeO2, La2O3 and their mixture, whose carriers were all γ-Al2O3, were used as the catalyst for the reduction of SO2 by CO. The activation process of this catalyst and the impact of temperature and reactant concentration on the activation process were investigated. Using X-ray diffraction, the structure characteristics of catalyst before and after reaction were analyzed to reveal the change of phase structure. The result shows that the rare earth oxide mixtures composing of CeO2 and La2O3, as the catalyst for the reduction of SO2 by CO, diminish activation temperature 50~100 ℃ less and have higher activity than a single oxide CeO2 or La2O3. The reason possibl is that La2O3 goes into in the lattice of CeO2 to form solid phase complex CeO2-La2O3 and increases the capability of CeO2-La2O3/γ-Al2O3 catalyst to store oxygen, which supplies the redox of CeO2 reaction with a better condition. At the same time, elemental sulfur formed in the redox reaction impels La2O3 to be transformed to activation phase La2O2S in a lower temperature, which can be explained with the synergism between redox reaction and COS intermediate mechanism reaction.

  3. Antimicrobial potential of green synthesized CeO2 nanoparticles from Olea europaea leaf extract

    Science.gov (United States)

    Maqbool, Qaisar; Nazar, Mudassar; Naz, Sania; Hussain, Talib; Jabeen, Nyla; Kausar, Rizwan; Anwaar, Sadaf; Abbas, Fazal; Jan, Tariq

    2016-01-01

    This article reports the green fabrication of cerium oxide nanoparticles (CeO2 NPs) using Olea europaea leaf extract and their applications as effective antimicrobial agents. O. europaea leaf extract functions as a chelating agent for reduction of cerium nitrate. The resulting CeO2 NPs exhibit pure single-face cubic structure, which is examined by X-ray diffraction, with a uniform spherical shape and a mean size 24 nm observed through scanning electron microscopy and transmission electron microscopy. Ultraviolet-visible spectroscopy confirms the characteristic absorption peak of CeO2 NPs at 315 nm. Fourier transform infrared spectroscopy reflects stretching frequencies at 459 cm−1, showing utilization of natural components for the production of NPs. Thermal gravimetric analysis predicts the successful capping of CeO2 NPs by bioactive molecules present in the plant extract. The antimicrobial studies show significant zone of inhibition against bacterial and fungal strains. The higher activities shown by the green synthesized NPs than the plant extract lead to the conclusion that they can be effectively used in biomedical application. Furthermore, reduction of cerium salt by plant extract will reduce environmental impact over chemical synthesis.

  4. DESIGN AND IMPLEMENTATION OF SINGLE-BUFFERED ROUTERS

    Institute of Scientific and Technical Information of China (English)

    Hu Ximing; Qu Jing; Wang Binqiang; Wu Jiangxing

    2007-01-01

    A Single-Buffered (SB) router is a router where only one stage of shared buffering is sand-wiched between two interconnects in comparison of a Combined Input and Output Queued (CIOQ)router where a central switch fabric is sandwiched between two stages of buffering. The notion of SB routers was firstly proposed by the High-Performance Networking Group (HPNG) of Stanford University, along with two promising designs of SB routers: one of which was Parallel Shared Memory (PSM) router and the other was Distributed Shared Memory (DSM) router. Admittedly, the work of HPNG deserved full credit, but all results presented by them appeared to relay on a Centralized Memory Management Algorithm (CMMA) which was essentially impractical because of the high processing and communication complexity. This paper attempts to make a scalable high-speed SB router completely practical by introducing a fully distributed architecture for managing the shared memory of SB routers. The resulting SB router is called as a Virtual Output and Input Queued (VOIQ) router. Furthermore, the scheme of VOIQ routers can not only eliminate the need for the CMMA scheduler, thus allowing a fully distributed implementation with low processing and communication complexity, but also provide QoS guarantees and efficiently support variable-length packets in this paper. In particular, the results of performance testing and the hardware implementation of our VOIQ-based router (NDSC(R) SR1880-TTM series) are illustrated at the end of this paper. The proposal of this paper is the first distributed scheme of how to design and implement SB routers publicized till now.

  5. Electronic storage capacity of ceria: role of peroxide in Aux supported on CeO2(111) facet and CO adsorption.

    Science.gov (United States)

    Liu, Yinli; Li, Huiying; Yu, Jun; Mao, Dongsen; Lu, Guanzhong

    2015-11-07

    Density functional theory (DFT+U) was used to study the adsorption of Aux (x = 1-4) clusters on the defective CeO2(111) facet and CO adsorption on the corresponding Aux/CeO2-x catalyst, in this work Aux clusters are adsorbed onto the CeO2-x + superoxide/peroxide surface. When Au1 is supported on the CeO2(111) facet with an O vacancy, the strong electronegative Au(δ-) formed is not favorable for CO adsorption. When peroxide is adsorbed on the CeO2(111) facet with the O vacancy, Aux was oxidized, resulting in stable Aux adsorption on the defective ceria surface with peroxide, which promotes CO adsorption on the Aux/CeO2-x catalyst. With more Au atoms in supported Aux clusters, CO adsorption on this surface becomes stronger. During both the Au being supported on CeO2-x and CO being adsorbed on Aux/CeO2-x, CeO2 acts as an electron buffer that can store/release the electrons. These results provide a scientific understanding for the development of high-performance rare earth catalytic materials.

  6. Dual-functional CeO2:Eu3+ nanocrystals for performance-enhanced dye-sensitized solar cells.

    Science.gov (United States)

    Roh, Jongmin; Hwang, Sun Hye; Jang, Jyongsik

    2014-11-26

    Single-crystalline, octahedral CeO2:Eu3+ nanocrystals, successfully prepared using a simple hydrothermal method, were investigated to determine their photovoltaic properties in an effort to enhance the light-harvesting efficiency of dye-sensitized solar cells (DSSCs). The size of the CeO2:Eu3+ nanocrystals (300-400 nm), as well as their mirrorlike facets, significantly improved the diffuse reflectance of visible light. Excitation of the CeO2:Eu3+ nanocrystal with 330 nm ultraviolet light was re-emitted via downconversion photoluminescence (PL) from 570 to 672 nm, corresponding to the 5D0→7FJ transition in the Eu3+ ions. Downconversion PL was dominant at 590 nm and had a maximum intensity for 1 mol % Eu3+. The CeO2:Eu3+ nanocrystal-based DSSCs exhibited a power conversion efficiency of 8.36%, an increase of 14%, compared with conventional TiO2 nanoparticle-based DSSCs, because of the strong light-scattering and downconversion PL of the CeO2:Eu3+ nanocrystals.

  7. Local structure and nanoscale homogeneity of CeO2-ZrO2: differences and similarities to parent oxides revealed by luminescence with temporal and spectral resolution.

    Science.gov (United States)

    Tiseanu, Carmen; Parvulescu, Vasile; Avram, Daniel; Cojocaru, Bogdan; Boutonnet, Magali; Sanchez-Dominguez, Margarita

    2014-01-14

    Although homogeneity at the atomic level of CeO2-ZrO2 with a Ce/Zr atomic ratio close to unity is considered to be one of the main causes for the increased total oxygen storage capacity (OSC), the characterization approaches of homogeneity remain a major challenge. We propose a simple, yet effective method, to assess both structural and compositional homogeneity of CeO2-ZrO2 by using Eu(3+) luminescence measured with time and dual spectral resolution (emission and excitation). For Eu(3+)-CeO2-ZrO2 calcined at 750 °C, the X-ray diffraction, Raman and High-Resolution Transmission Electron Microscopy data converge to a single pseudo-cubic phase. However, the evolution of Eu(3+)-delayed luminescence from cubic ceria-like to tetragonal zirconia-like emission reveals the formation of CeO2- and ZrO2-rich nanodomains and provides evidence for early phase separation. For Eu(3+)-CeO2-ZrO2 calcined at 1000 °C, the emission of Eu(3+) reveals both structural and compositional inhomogeneity. Our study identifies the differences between the local structure properties of CeO2 and ZrO2 parent oxides and CeO2-ZrO2 mixed oxide, also confirming the special chemical environment of the oxygen atoms in the mixed oxide as reported earlier by Extended X-ray Absorption Fine Structure investigations.

  8. Mn3O4-CeO2 nano-catalysts: Synthesis, characterization and application

    Science.gov (United States)

    Anushree, Sharma, C.; Kumar, S.

    2016-05-01

    Nano-sized Mn3O4-CeO2 catalysts were synthesized by a cost effective co-precipitation method, and were studied as a heterogeneous catalyst for wet air oxidation of paper industry wastewater at mild operating conditions of 90 °C and 1 atm. The structural, micro-structural and textural properties of synthesized catalysts were studied through various characterization techniques, i.e. XRD, TEM, N2-sorption and EDS. The catalytic activity of Mn3O4-CeO2 was interestingly found to be higher than the corresponding single-metal oxides, and the Ce50Mn50 nano-catalyst with small crystallite size (4.5 nm), high specific surface area (75 m2g-1) and high porosity (0.24 ccg-1) was found to be most efficient with 69% color, 60% COD, 59% TOC, 48% AOX removal.

  9. Simple Route to Obtain Nanostructured CeO2 Microspheres and CO Gas Sensing Performance

    Science.gov (United States)

    López-Mena, Edgar R.; Michel, Carlos R.; Martínez-Preciado, Alma H.; Elías-Zuñiga, Alex

    2017-03-01

    In this work, nanostructured CeO2 microspheres with high surface area and mesoporosity were prepared by the coprecipitation method, in absence of a template. The reaction between cerium nitrate and concentrated formic acid produced cerium formate, at room temperature. Further, calcination at 300 °C yielded single-phase CeO2 microspheres, with a diameter in the range 0.5-2.6 μm, the surface of these microspheres is completely nanostructured (diameter about 30-90 nm). CeO2 microspheres were used to fabricate a sensor device, and it was tested for intermediate CO gas concentrations (200-800 ppm). The detection of 200 ppm carbon monoxide was observed at 275 °C, with a response time of 9 s, using an applied frequency of 100 kHz. The detection of changes on the CO gas concentration was studied at different temperatures and applied frequencies. The results revealed a reproducible and stable gas sensing response.

  10. Ceo2 Based Catalysts for the Treatment of Propylene in Motorcycle’s Exhaust Gases

    Directory of Open Access Journals (Sweden)

    Phuong Thi Mai Pham

    2014-11-01

    Full Text Available In this work, the catalytic activities of several single metallic oxides were studied for the treatment of propylene, a component in motorcycles’ exhaust gases, under oxygen deficient conditions. Amongst them, CeO2 is one of the materials that exhibit the highest activity for the oxidation of C3H6. Therefore, several mixtures of CeO2 with other oxides (SnO2, ZrO2, Co3O4 were tested to investigate the changes in catalytic activity (both propylene conversion and CO2 selectivity. Ce0.9Zr0.1O2, Ce0.8Zr0.2O2 solid solutions and the mixtures of CeO2 and Co3O4 was shown to exhibit the highest propylene conversion and CO2 selectivity. They also exhibited good activities when tested under oxygen sufficient and excess conditions and with the presence of co-existing gases (CO, H2O.

  11. Variation of power generation at different buffer types and conductivities in single chamber microbial fuel cells.

    Science.gov (United States)

    Nam, Joo-Youn; Kim, Hyun-Woo; Lim, Kyeong-Ho; Shin, Hang-Sik; Logan, Bruce E

    2010-01-15

    Microbial fuel cells (MFCs) are operated with solutions containing various chemical species required for the growth of electrochemically active microorganisms including nutrients and vitamins, substrates, and chemical buffers. Many different buffers are used in laboratory media, but the effects of these buffers and their inherent electrolyte conductivities have not been examined relative to current generation in MFCs. We investigated the effect of several common buffers (phosphate, MES, HEPES, and PIPES) on power production in single chambered MFCs compared to a non-buffered control. At the same concentrations the buffers produced different solution conductivities which resulted in different ohmic resistances and power densities. Increasing the solution conductivities to the same values using NaCl produced comparable power densities for all buffers. Very large increases in conductivity resulted in a rapid voltage drop at high current densities. Our results suggest that solution conductivity at a specific pH for each buffer is more important in MFC studies than the buffer itself given relatively constant pH conditions. Based on our analysis of internal resistance and a set neutral pH, phosphate and PIPES are the most useful buffers of those examined here because pH was maintained close to the pK(a) of the buffer, maximizing the ability of the buffer to contribute to increase current generation at high power densities.

  12. Variation of power generation at different buffer types and conductivities in single chamber microbial fuel cells

    KAUST Repository

    Nam, Joo-Youn

    2010-01-15

    Microbial fuel cells (MFCs) are operated with solutions containing various chemical species required for the growth of electrochemically active microorganisms including nutrients and vitamins, substrates, and chemical buffers. Many different buffers are used in laboratory media, but the effects of these buffers and their inherent electrolyte conductivities have not been examined relative to current generation in MFCs. We investigated the effect of several common buffers (phosphate, MES, HEPES, and PIPES) on power production in single chambered MFCs compared to a non-buffered control. At the same concentrations the buffers produced different solution conductivities which resulted in different ohmic resistances and power densities. Increasing the solution conductivities to the same values using NaCl produced comparable power densities for all buffers. Very large increases in conductivity resulted in a rapid voltage drop at high current densities. Our results suggest that solution conductivity at a specific pH for each buffer is more important in MFC studies than the buffer itself given relatively constant pH conditions. Based on our analysis of internal resistance and a set neutral pH, phosphate and PIPES are the most useful buffers of those examined here because pH was maintained close to the pKa of the buffer, maximizing the ability of the buffer to contribute to increase current generation at high power densities. © 2009 Elsevier B.V. All rights reserved.

  13. Lattice-matched Cu2ZnSnS4/CeO2 solar cell with open circuit voltage boost

    Science.gov (United States)

    Crovetto, Andrea; Yan, Chang; Iandolo, Beniamino; Zhou, Fangzhou; Stride, John; Schou, Jørgen; Hao, Xiaojing; Hansen, Ole

    2016-12-01

    We report a reproducible enhancement of the open circuit voltage in Cu2ZnSnS4 solar cells by introduction of a very thin CeO2 interlayer between the Cu2ZnSnS4 absorber and the conventional CdS buffer. CeO2, a non-toxic earth-abundant compound, has a nearly optimal band alignment with Cu2ZnSnS4 and the two materials are lattice-matched within 0.4%. This makes it possible to achieve an epitaxial interface when growing CeO2 by chemical bath deposition at temperatures as low as 50 °C. The open circuit voltage improvement is then attributed to a decrease in the interface recombination rate through formation of a high-quality heterointerface.

  14. Fabrication of CeO2 Nanoparticle Modified Glassy Carbon Electrode for Ultrasensitive Determination of Trace Amounts of Uric Acid in Urine

    Institute of Scientific and Technical Information of China (English)

    WEI Yan; LI Mao-Guo; FANG Bin

    2007-01-01

    The preparation of a glassy carbon electrode modified by CeO2 nanoparticles was described, which was characterized by cyclic voltammetry and electrochemical impedance spectroscopy. In pH 6.0 buffer, the CeO2 nanoparticle modified electrode (CeO2 NP/GC) gave an excellent electrocatalytic activity for the oxidation of uric acid (UA).The catalytic current of UA versus its concentration had a good linear relation in the range of 2.0 × 10-7-5.0×10-4 mol/L, with the correlation coefficient of 0.9986 and detection limit of 1.0×10-7 mol/L. The modified electrode can be used for the determination of UA in urine, which can tolerate the interference of ascorbic acid up to 1000-fold. The method was simple, quick and sensitive.

  15. Photocatalytic degradation of methyl orange by CeO2 and Fe-doped CeO2 films under visible light irradiation.

    Science.gov (United States)

    Channei, D; Inceesungvorn, B; Wetchakun, N; Ukritnukun, S; Nattestad, A; Chen, J; Phanichphant, S

    2014-08-29

    Undoped CeO2 and 0.50-5.00 mol% Fe-doped CeO2 nanoparticles were prepared by a homogeneous precipitation combined with homogeneous/impreganation method, and applied as photocatalyst films prepared by a doctor blade technique. The superior photocatalytic performances of the Fe-doped CeO2 films, compared with undoped CeO2 films, was ascribed mainly to a decrease in band gap energy and an increase in specific surface area of the material. The presence of Fe(3+) as found from XPS analysis, may act as electron acceptor and/or hole donor, facilitating longer lived charge carrier separation in Fe-doped CeO2 films as confirmed by photoluminescence spectroscopy. The 1.50 mol% Fe-doped CeO2 film was found to be the optimal iron doping concentration for MO degradation in this study.

  16. Collective magnetic response of CeO2 nanoparticles

    Science.gov (United States)

    Coey, Michael; Ackland, Karl; Venkatesan, Munuswamy; Sen, Siddhartha

    2016-07-01

    The magnetism of nanoparticles and thin films of wide-bandgap oxides that include no magnetic cations is an unsolved puzzle. Progress has been hampered by both the irreproducibility of much of the experimental data, and the lack of any generally accepted theoretical explanation. The characteristic signature is a virtually anhysteretic, temperature-independent magnetization curve that saturates in an applied field that is several orders of magnitude greater than the magnetization. It would seem as if a tiny volume fraction, sugar or latex microspheres. The saturation magnetization, Ms ≍ 60 A m-1 for compact samples, is maximized by 1 wt% lanthanum doping. Dispersing the CeO2 nanopowder reduces its magnetic moment by up to an order of magnitude, and there is a characteristic length scale of order 100 nm for the magnetism to appear in CeO2 nanoparticle clusters. The phenomenon is explained in terms of a giant orbital paramagnetism that appears in coherent mesoscopic domains due to resonant interaction with zero-point fluctuations of the vacuum electromagnetic field. The theory explains the observed temperature-independent magnetization curve and its doping and dispersion dependence, based on a length scale of 300 nm that corresponds to the wavelength of a maximum in the ultraviolet absorption spectrum of the magnetic CeO2 nanoparticles. The coherent domains occupy roughly 10% of the sample volume.

  17. Optical properties of CeO2 thin films

    Indian Academy of Sciences (India)

    S Debnath; M R Islam; M S R Khan

    2007-08-01

    Cerium oxide (CeO2) thin films have been prepared by electron beam evaporation technique onto glass substrate at a pressure of about 6 × 10-6 Torr. The thickness of CeO2 films ranges from 140–180 nm. The optical properties of cerium oxide films are studied in the wavelength range of 200–850 nm. The film is highly transparent in the visible region. It is also observed that the film has low reflectance in the ultra-violet region. The optical band gap of the film is determined and is found to decrease with the increase of film thickness. The values of absorption coefficient, extinction coefficient, refractive index, dielectric constant, phase angle and loss angle have been calculated from the optical measurements. The X-ray diffraction of the film showed that the film is crystalline in nature. The crystallite size of CeO2 films have been evaluated and found to be small. The experimental -values of the film agreed closely with the standard values.

  18. Unusual Compression Behavior of Nanocrystalline CeO2

    Science.gov (United States)

    Wang, Qiming; He, Duanwei; Peng, Fang; Lei, Li; Liu, Pingping; Yin, Shuai; Wang, Pei; Xu, Chao; Liu, Jing

    2014-01-01

    The x-ray diffraction study of 12 nm CeO2 was carried out up to ~40 GPa using an angle dispersive synchrotron-radiation in a diamond-anvil cell with different pressure transmitting medium (PTM) (4:1 methanol: ethanol mixture, silicone oil and none) at room temperature. While the cubic fluorite-type structure CeO2 was retained to the highest pressure, there is progressive broadening and intensity reduction of the reflections with increasing pressure. At pressures above 12 GPa, an unusual change in the compression curve was detected in all experiments. Significantly, apparent negative volume compressibility was observed at P = 18–27 GPa with silicone oil as PTM, however it was not detected in other circumstances. The expansion of the unit cell volume of cubic CeO2 was about 1% at pressures of 15–27 GPa. To explain this abnormal phenomenon, a dual structure model (hard amorphous shell and relatively soft crystalline core) has been proposed. PMID:24658049

  19. Rose Bengal sensitized bilayered photoanode of nano-crystalline TiO2-CeO2 for dye-sensitized solar cell application

    Science.gov (United States)

    Sayyed, Suhail A. A. R.; Beedri, Niyamat I.; Kadam, Vishal S.; Pathan, Habib M.

    2016-08-01

    The present work deals with the study of TiO2-CeO2 bilayered photoanode with low-cost Rose Bengal (RB) dye as sensitizer for dye-sensitized solar cell application. The recombination reactions are reduced in bilayered TiO2-CeO2 photoanode as compared to the single-layered CeO2 photoanode. Once the electrons get transferred from lowest unoccupied molecular orbital level of RB dye to the conduction band (CB) of TiO2, then the possibilities of recombination of electrons with oxidized dye molecules or oxidized redox couple are reduced. This is because the CB position of CeO2 is higher than that of TiO2, which blocks the path of electrons. The electrochemical impedance spectroscopy (EIS) analysis shows negative shift in frequency for bilayered TiO2-CeO2 photoanode as compared to CeO2 photoanode. Hence, in bilayered photoanode lifetime of electrons is more than in single-layered photoanode, confirming reduction in recombination reactions. The X-ray diffraction patterns confirm both anatase TiO2 and CeO2 with crystalline size using Scherrer formula as 24 and 10 nm, respectively. The scanning electron microscopy images of photoanode show the porous structure useful for dye adsorption. The presence of Ti and Ce is confirmed by electron diffraction studies. The band gap values for TiO2 and CeO2 were calculated as 3.20 and 3.11 eV, respectively, using diffused reflectance spectroscopy. The bilayered TiO2-CeO2 photoanode showed open-circuit voltage ( V OC) ~500 mV and short-circuit photocurrent density ( J SC) ~0.29 mA/cm2 with fill factor (FF) ~62.17 %. There is increase in V OC and J SC values by 66.67 and 38.10 %, respectively, compared to RB-sensitized CeO2 photoanode.

  20. Preparation and catalytic behavior of CeO2 nanoparticles on Al2O3 crystal

    Science.gov (United States)

    Hattori, Takashi; Kobayashi, Katsutoshi; Ozawa, Masakuni

    2017-01-01

    In this work, we examined the preparation, morphology, and catalytic behavior of CeO2 nanoparticles (NPs) on Al2O3(0001) crystal substrates. A CeO2 NP layer was prepared by the dipping method using a CeO2 nanocrystal colloid solution. Even after heat treatment at 1000 °C, the CeO2 NP layer maintained the granular morphology of CeO2 with a grain diameter of less than 40 nm. CeO2 NPs on an Al2O3 crystal showed higher oxidation activity for gaseous hydrogen at moderate temperatures and enhanced oxygen release properties of CeO2, compared with CeO2 powder. This was due to the highly dispersed CeO2 NPs and the interaction between CeO2 NPs and Al2O3; this clarified the importance of the Al2O3 support for the CeO2 catalyst.

  1. An on-chip coupled resonator optical waveguide single-photon buffer.

    Science.gov (United States)

    Takesue, Hiroki; Matsuda, Nobuyuki; Kuramochi, Eiichi; Munro, William J; Notomi, Masaya

    2013-01-01

    Integrated quantum optical circuits are now seen as one of the most promising approaches with which to realize single-photon quantum information processing. Many of the core elements for such circuits have been realized, including sources, gates and detectors. However, a significant missing function necessary for photonic quantum information processing on-chip is a buffer, where single photons are stored for a short period of time to facilitate circuit synchronization. Here we report an on-chip single-photon buffer based on coupled resonator optical waveguides (CROW) consisting of 400 high-Q photonic crystal line-defect nanocavities. By using the CROW, a pulsed single photon is successfully buffered for 150 ps with 50-ps tunability while maintaining its non-classical properties. Furthermore, we show that our buffer preserves entanglement by storing and retrieving one photon from a time-bin entangled state. This is a significant step towards an all-optical integrated quantum information processor.

  2. An on-chip coupled resonator optical waveguide single-photon buffer

    CERN Document Server

    Takesue, Hiroki; Kuramochi, Eiichi; Munro, Willian J; Notomi, Masaya

    2013-01-01

    Integrated quantum optical circuits are now seen as one of the most promising approaches with which to realize single photon quantum information processing. Many of the core elements for such circuits have been realized including sources, gates and detectors. However, a significant missing function necessary for photonic information processing on-chip is a buffer, where single photons are stored for a short period of time to facilitate circuit synchronization. Here we report an on-chip single photon buffer based on coupled resonator optical waveguides (CROW) consisting of 400 high-Q photonic crystal line defect nanocavities. By using the CROW, a pulsed single photon was successfully buffered for 150 ps with 50-ps tunability while maintaining its non-classical properties. Furthermore, we showed that our buffer preserves entanglement by storing and retrieving one photon from a time-bin entangled state. This is a significant step towards an all-optical integrated quantum information processor.

  3. Structural characterization of nanosized CeO(2)-SiO(2), CeO(2)-TiO(2), and CeO(2)-ZrO(2) catalysts by XRD, Raman, and HREM techniques.

    Science.gov (United States)

    Reddy, Benjaram M; Khan, Ataullah; Lakshmanan, Pandian; Aouine, Mimoun; Loridant, Stéphane; Volta, Jean-Claude

    2005-03-03

    Structural characteristics of nanosized ceria-silica, ceria-titania, and ceria-zirconia mixed oxide catalysts have been investigated using X-ray diffraction (XRD), Raman spectroscopy, BET surface area, thermogravimetry, and high-resolution transmission electron microscopy (HREM). The effect of support oxides on the crystal modification of ceria cubic lattice was mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahighly dilute solutions and were subjected to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO(2)-SiO(2) sample primarily consists of nanocrystalline CeO(2) on the amorphous SiO(2) surface. Both crystalline CeO(2) and TiO(2) anatase phases were noted in the case of CeO(2)-TiO(2) sample. Formation of cubic Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) (at 1073 K) were observed in the case of the CeO(2)-ZrO(2) sample. Raman measurements disclose the fluorite structure of ceria and the presence of oxygen vacancies/Ce(3+). The HREM results reveal well-dispersed CeO(2) nanocrystals over the amorphous SiO(2) matrix in the cases of CeO(2)-SiO(2), isolated CeO(2), and TiO(2) (anatase) nanocrystals, some overlapping regions in the case of CeO(2)-TiO(2), and nanosized CeO(2) and Ce-Zr oxides in the case of CeO(2)-ZrO(2) sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental images reveal that the CeO(2) is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the OSC of the mixed oxide systems is more than that of pure CeO(2) and is system dependent.

  4. Effects of CeO2 Nanoparticles on Terrestrial Isopod Porcellio scaber: Comparison of CeO2 Biological Potential with Other Nanoparticles.

    Science.gov (United States)

    Malev, Olga; Trebše, Polonca; Piecha, Małgorzata; Novak, Sara; Budič, Bojan; Dramićanin, Miroslav D; Drobne, Damjana

    2017-02-01

    Nano-sized cerium dioxide (CeO2) particles are emerging as an environmental issue due to their extensive use in automobile industries as fuel additives. Limited information is available on the potential toxicity of CeO2 nanoparticles (NPs) on terrestrial invertebrates through dietary exposure. In the present study, the toxic effects of CeO2 NPs on the model soil organism Porcellio scaber were evaluated. Nanotoxicity was assessed by monitoring the lipid peroxidation (LP) level and feeding rate after 14-days exposure to food amended with nano CeO2. The exposure concentration of 1000 μg of CeO2 NPs g(-1) dry weight food for 14 days significantly increased both the feeding rate and LP. Thus, this exposure dose is considered the lowest observed effect dose. At higher exposure doses of 2000 and 5000 μg of CeO2 NPs g(-1) dry weight food, NPs significantly decreased the feeding rate and increased the LP level. Comparative studies showed that CeO2 NPs are more biologically potent than TiO2 NPs, ZnO NPs, CuO NPs, CoFe2O4 NPs, and Ag NPs based on feeding rate using the same model organism and experimental setup. Based on comparative metal oxide NPs toxicities, the present results contribute to the knowledge related to the ecotoxicological effects of CeO2 NPs in terrestrial invertebrates exposed through feeding.

  5. Origin of enhanced photocatalytic activity of F-doped CeO2 nanocubes

    Science.gov (United States)

    Miao, Hui; Huang, Gui-Fang; Liu, Jin-Hua; Zhou, Bing-Xin; Pan, Anlian; Huang, Wei-Qing; Huang, Guo-Fang

    2016-05-01

    CeO2 nanoparticles are synthesized using a low-temperature solution combustion method and subsequent heat treatment in air. It is found that F-doping leads to smaller particle size and the formation of CeO2 nanocubes with higher percentage of reactive facets exposed. The band gap is estimated to be 3.16 eV and 2.88 eV, for pure CeO2 and fluorine doped CeO2 (F-doped CeO2) nanocubes, respectively. The synthesized F-doped CeO2 nanocubes exhibit much higher photocatalytic activities than commercial TiO2 and spherical CeO2 for the degradation of MB dye under UV and visible light irradiation. The apparent reaction rate constant k of MB decomposition over the optimized F-doped CeO2 nanocubes is 9.5 times higher than that of pure CeO2 and 2.2 times higher than that of commercial TiO2. The enhanced photocatalytic activity of F-doped CeO2 nanocubes originates from the fact that F-doping induces the small size, the highly reactive facets exposed, the intense absorption in the UV-vis range and the narrowing of the band gap. This research provides some new insights for the synthesis of the doping of the foreign atoms into photocatalyst with controlled morphology and enhanced photocatalytic activity.

  6. Simulation study on single event burnout in linear doping buffer layer engineered power VDMOSFET

    Science.gov (United States)

    Yunpeng, Jia; Hongyuan, Su; Rui, Jin; Dongqing, Hu; Yu, Wu

    2016-02-01

    The addition of a buffer layer can improve the device's secondary breakdown voltage, thus, improving the single event burnout (SEB) threshold voltage. In this paper, an N type linear doping buffer layer is proposed. According to quasi-stationary avalanche simulation and heavy ion beam simulation, the results show that an optimized linear doping buffer layer is critical. As SEB is induced by heavy ions impacting, the electric field of an optimized linear doping buffer device is much lower than that with an optimized constant doping buffer layer at a given buffer layer thickness and the same biasing voltages. Secondary breakdown voltage and the parasitic bipolar turn-on current are much higher than those with the optimized constant doping buffer layer. So the linear buffer layer is more advantageous to improving the device's SEB performance. Project supported by the National Natural Science Foundation of China (No. 61176071), the Doctoral Fund of Ministry of Education of China (No. 20111103120016), and the Science and Technology Program of State Grid Corporation of China (No. SGRI-WD-71-13-006).

  7. CeO2 nanocubes-graphene oxide as durable and highly active catalyst support for proton exchange membrane fuel cell.

    Science.gov (United States)

    Lei, M; Wang, Z B; Li, J S; Tang, H L; Liu, W J; Wang, Y G

    2014-12-10

    Rapid degradation of cell performance still remains a significant challenge for proton exchange membrane fuel cell (PEMFC). In this work, we develop novel CeO2 nanocubes-graphene oxide nanocomposites as durable and highly active catalyst support for proton exchange membrane fuel cell. We show that the use of CeO2 as the radical scavenger in the catalysts remarkably improves the durability of the catalyst. The catalytic activity retention of Pt-graphene oxide-8 wt.% CeO2 nanocomposites reaches as high as 69% after 5000 CV-cycles at a high voltage range of 0.8-1.23 V, in contrast to 19% for that of the Pt-graphene oxide composites. The excellent durability of the Pt-CeO2 nanocubes-graphene oxide catalyst is attributed to the free radical scavenging activity of CeO2, which significantly slows down the chemical degradation of Nafion binder in catalytic layers, and then alleviates the decay of Pt catalysts, resulting in the excellent cycle life of Pt-CeO2-graphene oxide nanocomposite catalysts. Additionally, the performance of single cell assembled with Nafion 211 membrane and Pt-CeO2-graphene oxide catalysts with different CeO2 contents in the cathode as well as the Pt-C catalysts in the anode are also recorded and discussed in this study.

  8. Preparation and Characterization of Nanocrystalline CeO2 by Precipitation Method

    Institute of Scientific and Technical Information of China (English)

    董相廷; 李明; 张伟; 刘桂霞; 洪广言

    2002-01-01

    CeO2 nanocrystalline particulates with different sizes were prepared by precipitation method using ethanol as dispersive and protective reagent. XRD spectra show that the synthesized CeO2 has cubic crystalline structure of space group O5H-FM3M, when calcination temperature is in the range of 250~800 ℃. TEM images reveal that CeO2 particles are spherical in shape. The average size of the particles increases with the increase of calcination temperature. Thermogravimetric analysis indicates that the weight loss of precursor mainly depends on the calcination temperature, and little depends on the calcination time. Measurements of CeO2 relative density show that the relative density of CeO2 nanocrystalline powders increases with increasing CeO2 particle size.

  9. Visible light induced degradation of methylene blue using CeO2/V2O5 and CeO2/CuO catalysts.

    Science.gov (United States)

    Saravanan, R; Joicy, S; Gupta, V K; Narayanan, V; Stephen, A

    2013-12-01

    In the present study, the nanocatalysts CeO2, V2O5, CuO, CeO2/V2O5 and CeO2/CuO were synthesized by thermal decomposition method. This method is simple, fast and cost effective compared with other preparation methods. The synthesized catalysts were characterized by different techniques. The XRD and XPS results confirmed the structure and the oxidization states of the nanocomposite materials. DRS results suggested that the prepared CeO2/V2O5 and CeO2/CuO nanocomposites can generate more electrons and holes under visible light irradiation. The photocatalytic activities of prepared catalysts were evaluated using the degradation of aqueous methylene blue solution as a model compound under visible light irradiation. In addition, the nanocomposite (CeO2/V2O5 and CeO2/CuO) materials were employed to degrade the textile effluent under visible light condition.

  10. Controllable preparation of CeO2 nanostructure materials and their catalytic activity

    Institute of Scientific and Technical Information of China (English)

    Shan Wenjuan; Guo Hongjuan; Liu Chang; Wang Xiaonan

    2012-01-01

    Well-crystalline CeO2 nanostructures with the morphology ofnanorods and nanocubes were synthesized by a template-free hydrothermal method.X-ray diffraction (XRD),transmission electron microscopy (TEM),Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption measurements were employed to characterize the synthesized materials.The reducibility and catalytic activity of nanostructured CeO2 were examined by hydrogen temperature-programmed reduction (H2-TPR) and CO oxidation.The results showed that CeO2 nanorods could be converted into CeO2 nanocubes with the increasing of the reaction time and the hydrothermal temperature,CeO2 nanorods became longer gradually with the increasing of the concentrations of NaOH.H2-TPR characterization demonstrated that the intense low-temperature reduction peak in the CeO2 nanorods indicated the amount of hydrogen consumed is larger than CeO2 nanocubes.Meantime the CeO2 nanorods enhanced catalytic activity for CO oxidation,the total conversion temperature was 340 ℃.The reasons were that CeO2 nanorods have much smaller crystalline sizes and higher surface areas than CeO2 nanocubes.

  11. Effect of oxidizing agents in CeO2 thin film formation.

    Science.gov (United States)

    Yadav, S. M.; Sartale, S. D.

    2012-06-01

    Cerium Oxide (CeO2) thin films have been prepared by oxidative soak method onto glass substrates using NaNO2 and NaBrO3 oxidizing agents. Because of different oxidation strength different crystallinity, morphology and optical properties of the CeO2 films have been observed. Furthermore it has been observed that crystalline, transparent and crack free CeO2 thin films can be obtained using NaNO2 oxidizing agent. On the other hand CeO2 thin films deposited by using NaBrO3 oxidizing agent are amorphous, less transparent and porous with large number of cracks.

  12. Effect of CeO2 coupling on the structural, optical and photocatalytic properties of ZnO nanoparticle

    Science.gov (United States)

    Sherly, E. D.; Vijaya, J. Judith; Kennedy, L. John

    2015-11-01

    This research work presents the microwave assisted combustion synthesis, characterization and photocatalytic applications of ZnO-CeO2 coupled nano metal oxide. ZnO, CeO2 and the coupled oxides ZnCe, Zn2Ce and ZnCe2 with ZnO and CeO2 in the molar ratio 1:1, 2:1 and 1:2 respectively were fabricated by microwave assisted metal nitrate-urea solution combustion synthesis, without using any organic solvent or surfactant. As-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance spectroscopy (DRS) and photoluminescence spectroscopy(PL). The experiments of photocatalytic activity indicate that Zn2Ce nanoparticles exhibit excellent photocatalytic performance in the degradation of 2,4-dichlorophenol (2,4-DCP). 95% of 2,4-DCP molecules were decomposed by Zn2Ce in 240 min. The better photocatalytic degradation ability of Zn2Ce compared to ZnCe, ZnCe2 or single component ZnO and CeO2 nanoparticles is attributed to the improved separation of photogenerated electron-hole pairs.

  13. Novel nanostructured CeO2 as efficient catalyst for energy and environmental applications

    Indian Academy of Sciences (India)

    Sumanta Kumar Meher; G Ranga Rao

    2014-03-01

    We report here versatile methods to engineer the microstructure and understand the fundamental physicochemical properties of CeO2 to improve its catalytic viability for practical applications. In this context, different morphologies of CeO2 are synthesized using tailored homogeneous precipitation methods and characterized by XRD, BET, SEM and TPR methods. The shuttle-shaped CeO2 prepared under hydrothermal condition shows higher surface area and low-temperature reducibility. The 0.5 wt% Pt-impregnated shuttle-shaped CeO2 shows lower-temperature CO oxidation behaviour as compared to its bulk-like CeO2 (with 0.5 wt% Pt) counterpart, synthesized by conventional-reflux method. Further, nanorod morphology of CeO2 prepared with Cl−as counter ion shows lower-temperature oxidation of soot as compared to the mesoflower morphology of CeO2, prepared with NO$^{−}_{3}$ as counter ion in the reaction medium. Further, linear sweep voltammetry, chronopotentiometry and CO-stripping voltammetry studies are performed to evaluate the promoting activity of CeO2 to Pt/C for ethanol electro-oxidation reaction in acidic media. Results show that CeO2 provides active triple-phase-interfacial sites for suitable adsorption of OH species which effectively oxidize the COads on Pt/C. The results presented here are significant in the context of understanding the physicochemical fine prints of CeO2 and CeO2 based hetero-nanocomposites for their suitability to important catalytic and energy-related applications.

  14. Diesel/biodiesel soot oxidation with ceo2 and ceo2-zro2-modified cordierites: a facile way of accounting for their catalytic ability in fuel combustion processes

    OpenAIRE

    Silva,Rodrigo F.; Edimar DeOliveira; Paulo C. de Sousa Filho; Neri,Cláudio R.; OSVALDO A. SERRA

    2011-01-01

    CeO2 and mixed CeO2-ZrO2 nanopowders were synthesized and efficiently deposited onto cordierite substrates, with the evaluation of their morphologic and structural properties through XRD, SEM, and FTIR. The modified substrates were employed as outer heterogeneous catalysts for reducing the soot originated from the diesel and diesel/biodiesel blends incomplete combustion. Their activity was evaluated in a diesel stationary motor, and a comparative analysis of the soot emission was carried out ...

  15. Dielectric Properties of CeO2 -Doped Ba( Zr, Ti)O3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    Huang Xinyou; Gao chunhua; Chen Xiangchong; Liu Huiping; Huang Guojun; Zheng Xialian

    2004-01-01

    The influence of additive amount of CeO2 on the properties of Ba(Ti, Zr)O3 (BTZ) capacitor ceramics prepared using conventional solid-state reaction method was investigated. The dielectric constant(ε) increases to a maximum when w( CeO2 ) is about 1.0% and then decreases again at higher doping concentration of CeO2. The dielectric constant gets a maximum while w ( CeO2 ) is about 1. 0%, and the dielectric loss is minimum while w ( CeO2 ) is0.5 %. CeO2 can decrease the curie temperature, widen the εr-T peak and decrease the absolute value of dielectric constant temperature coefficient. The influence mechanism of CeO2 additive on the properties of the BTZ ceramics was discussed. The results show that CeO2 additive influences the properties of BTZ ceramics by means of forming defect solid solution , shifting curie temperature peak effect, segregating in crystal boundary , and impeding grain growth.

  16. Size effect of Raman scattering on CeO2 nanocrystal by hydrothermal method

    Science.gov (United States)

    Hattori, Takashi; Kobayashi, Katsutoshi; Ozawa, Masakuni

    2017-01-01

    In this study, we prepared surface-modified CeO2 nanocrystals (NCs) by a hydrothermal method, and calcined CeO2 NCs at various temperatures between 400 and 1000 °C for 3 h in air to obtain crystal-size-controlled CeO2 NCs. We investigated the correlation between the Raman spectra and the crystal sizes of the CeO2 powder. The peak position of the F2g mode of CeO2 was shifted to lower energies as the crystal size decreased and the peak broadened. The present hydrothermally driven CeO2 NCs showed no change in lattice constant depending on crystal size after heat treatment. The Raman peak position of the F2g mode as a function of inverse CeO2 crystal size corresponded to the models for phonon confinement without the combination of strain and defect effects. Moreover, it was also suggested that the Raman peak width of CeO2 NCs without strain also showed dependence on particle size.

  17. Redox enzyme-mimicking activities of CeO2 nanostructures: Intrinsic influence of exposed facets

    Science.gov (United States)

    Yang, Yushi; Mao, Zhou; Huang, Wenjie; Liu, Lihua; Li, Junli; Li, Jialiang; Wu, Qingzhi

    2016-10-01

    CeO2 nanoparticles (NPs) have been well demonstrated as an antioxidant in protecting against oxidative stress-induced cellular damages and a potential therapeutic agent for various diseases thanks to their redox enzyme-mimicking activities. The Ce3+/Ce4+ ratio and oxygen vacancies on the surface have been considered as the major originations responsible for the redox enzyme-mimicking activities of CeO2 NPs. Herein, CeO2 nanostructures (nanocubes and nanorods) exposed different facets were synthesized via a facile hydrothermal method. The characterizations by X-ray photoelectron spectroscopy, Raman spectroscopy, and UV-Vis spectroscopy show that the Ce3+/Ce4+ ratio and oxygen vacancy content on the surfaces of as-synthesized CeO2 nanostructures are nearly at the same levels. Meanwhile, the enzymatic activity measurements indicate that the redox enzyme-mimicking activities of as-synthesized CeO2 nanostructures are greatly dependent on their exposed facets. CeO2 nanocubes with exposed {100} facets exhibit a higher peroxidase but lower superoxide dismutase activity than those of the CeO2 nanorods with exposed {110} facets. Our results provide new insights into the redox enzyme-mimicking activities of CeO2 nanostructures, as well as the design and synthesis of inorganic nanomaterials-based artificial enzymes.

  18. Preparation and performance of CeO2 hollow spheres and nanoparticles

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wenwen; CHEN Donghui

    2016-01-01

    CeO2 hollow spheres were synthesized by polystryrene sphere (PS) templates and CeO2 nanoparticles were prepared by a facile method. The as-obtained products were characterized by scanning electron microscopy (SEM), N2 adsorption-desorption, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and UV-vis diffuse reflectance spectra. The results showed that the structure of the obtained CeO2 hollow spheres was hollow microsphere with a diameter of 380 nm and the average particle size of CeO2 nanoparticles was about 1700 nm. The two samples' Brunauer-Emmett-Teller (BET) surface area was 67.1 and 37.2 m2/g. The CeO2 hollow spheres had a better performance than nanoparticles at UV-shielding because of higher surface area and the structure of hollow sphere.

  19. Synthesis of Mn-doped CeO2 nanorods and their application as humidity sensors

    Indian Academy of Sciences (India)

    C H Hu; C H Xia; F Wang; M Zhou; P F Yin; X Y Han

    2011-08-01

    Mn-doped CeO2 nanorods have been prepared from CeO2 particles through a facile compositehydroxide-mediated (CHM) approach. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The analysis from the X-ray photoelectron spectroscopy indicates that the manganese doped in CeO2 exists as Mn4+. The responses to humidity for static and dynamic testing proved dopingMn into CeO2 can improve the humidity sensitivity. For the sample with Mn% about 1.22, the resistance changes from 375.3 to 2.7M as the relative humidity (RH) increases from 25 to 90%, indicating promising applications of the Mn-doped CeO2 nanorods in environmental monitoring.

  20. Temperature Programmed Reduction Studies on CeO2-Containing Catalysts

    Institute of Scientific and Technical Information of China (English)

    Noriyoshi Kakuta; Harunobu Ohkita; Takanori Mizushima

    2004-01-01

    Temperature programmed reduction (TPR) study was carried out for CeO2/Al2O3 and CeO2/ZrO2 catalysts to evaluate oxygen storage property induced by a facile redox cycling of Ce ion. The CeO2/ZrO2 catalyst possesses excellent oxygen storage activity at 373 K after reduction above 1173 K although the oxygen storage of CeO2/Al2O3 catalyst after reduction above 1173 K is poor because of the formation of CeAlO3. Consequently, the oxygen storage on the CeO2/ZrO2 catalyst smoothly occurs from low temperatures when the catalyst is reduced even at high temperatures.

  1. Preparation of nanosized yttrium doped CeO2 catalyst used for photocatalytic application

    Directory of Open Access Journals (Sweden)

    A. Akbari-Fakhrabadi

    2015-09-01

    Full Text Available In the present work, the pure CeO2 and yttrium doped CeO2 nanopowders were synthesized by the nitrate-fuel self-sustaining combustion method and calcined at 700 °C for 2 h. X-ray diffraction (XRD and high resolution electron transmission microscopy (HRTEM results demonstrated a cubic fluorite with high purity and the crystallite sizes less than 20 nm calculated from Scherrer’s formula. The BET specific surface area of yttrium doped CeO2 samples showed high values than those of pure CeO2. The photocatalytic activity of yttrium doped CeO2 showed high degradation of Rhodamine B solution under visible light illumination.

  2. Direct Synthesis and Spectrum Analysis of CeO2 Nanoparticles Deposited on Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zuwei; HU Chenguo; XIONG Yufeng; XIA Chuanhui; LI Feiyun; WANG Xue

    2009-01-01

    A novel method of direct synthesis of CeO2 nanoparticles onto multi-walled carbon nanotubes (MWNTs) was developed with advantages of simplicity, ease of scale-up, and low costs.The size of CeO2 particles deposited on the MWNTs was less than 6 nm. SEM and TEM were em-ployed to analysis the CeO2 coated MWNTs, and the properties of FTIR spectrum and UV-vis ab-sorption spectrum were investigated. The functional groups on the MWNTs obtained by nitric acid treatment play an important role on the deposition of the CeO2 particles. The carbon nanotubes possess broadened UV absorption function after being coated with CeO2 nanopartilces.

  3. Kinetics of a single trapped ion in an ultracold buffer gas

    CERN Document Server

    Zipkes, Christoph; Sias, Carlo; Köhl, Michael

    2010-01-01

    The immersion of a single ion confined by a radiofrequency trap in an ultracold atomic gas extends the concept of buffer gas cooling to a new temperature regime. The steady state energy distribution of the ion is determined by its kinetics in the radiofrequency field rather than the temperature of the buffer gas. Moreover, the finite size of the ultracold gas facilitates the observation of back-action of the ion onto the buffer gas. We numerically investigate the system's properties depending on mass ratio, trap geometry, differential cross-section, and non-uniform neutral atom density distribution. We identify excess micromotion to set the typical scale for the ion energy statistics and explore the applicability of the mobility collision cross-section to the ultracold regime.

  4. CeO2 nanorods-supported transition metal catalysts for CO oxidation.

    Science.gov (United States)

    Mock, Samantha A; Sharp, Shannon E; Stoner, Thomas R; Radetic, Michael J; Zell, Elizabeth T; Wang, Ruigang

    2016-03-15

    A catalytically active oxide support in combination with metal catalysts is required in order to achieve better low temperature activity and selectivity. Here, we report that CeO2 nanorods with a superior surface oxygen release/storage capability were used as an active support of transition metal (TM) catalysts (Mn, Fe, Co, Ni, Cu) for CO oxidation reaction. The as-prepared CeO2 nanorods supported 10 wt% TM catalysts were highly active for CO oxidation at low temperature, except for the Fe sample. It is found that the 10%Cu-CeO2 catalyst performed best, and it provided a lower light-off temperature with T50 (50% conversion) at 75 °C and T100 (100% conversion) of CO to CO2 at 194 °C. The atomic level surface structure of CeO2 nanorods was investigated in order to understand the improved low temperature catalytic activity. The richness of surface roughness and various defects (voids, lattice distortion, bending, steps, twinning) on CeO2 nanorods could facilitate oxygen release and storage. According to XRD and Raman analysis, copper species migrate into the bulk CeO2 nanorods to a greater degree. Since CO adsorbed over the surface of the catalyst/support is detrimental to its catalytic activity, the surface defects on the CeO2 nanorods and CeO2-TM interactions were critical to the enhanced activity.

  5. Effect of the Addition of CeO2 to Iron Phosphate Glass for Catalytic Applications.

    Science.gov (United States)

    Chung, Jae-Yeop; Kim, Jong-Hwan; Choi, Su-Yeon; Ryu, Bong-Ki

    2015-10-01

    We investigated the effect of CeO2 content on the catalytic behavior and chemical properties of the (100 - x)(80P2O5-20Fe2O3)-xCeO2 (x = 0, 4, 8, 12, 16, 20 and 24 wt%) glass system. Using thermogravimetric analysis, we confirmed that the catalytic activity increased until a CeO2 content of 16 wt%, beyond which, it decreased. The reasons for the change in the catalytic properties of the glass samples were determined using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density analyses. It was confirmed using the FT-IR and XPS-01s spectra that CeO2 acts as a network modifier in iron phosphate glass. When the CeO2 content is above 16 wt%, the number of non-bridging oxygen atoms decreases with increasing CeO2 content. For these reasons, the catalytic properties decrease when the CeO2 content is more than 16 wt%. From the dissolution rate measurements, it can be observed that cerium-iron phosphate has a high water resistance. Also, as we expected, it can be confirmed that the chemical durability is improved with increasing CeO2 content.

  6. Fe-Doped Polycrystalline CeO2 as Terahertz Optical Material

    Institute of Scientific and Technical Information of China (English)

    WEN Qi-Ye; ZHANG Huai-Wu; YANG Qing-Hui; LI Sheng; XU De-Gang; YAO Jian-Quan

    2009-01-01

    @@ Fe-doped CeO2 is synthesized by ceramic method and the effects of Fe doping on the structure and properties are characterized by ordinary methods and terahertz-time domain spectrometer (THz-TDS) technique. Our results show that pure CeO2 only has a small dielectric constant ε of 4, while a small amount of Fe (0.9 at.%) doping into CeO2 promotes densification and induces a large ε of 23. From the THz spectroscopy, it is found that for undoped CeO2 both the power absorption and the index of re[faction increase with frequency, while for Fe-doped CeO2 we measure a remarkable transparency together with a flat index curve. The absorption coefficient of Fe-doped CeO2 at frequency ranging from 0.2 to 1.8 THz is less than 0.35 cm-1, implying that Fe-doped CeO2 is a potential THz optical material.

  7. Role of vacancies, light elements and rare-earth metals doping in CeO2.

    Science.gov (United States)

    Shi, H; Hussain, T; Ahuja, R; Kang, T W; Luo, W

    2016-08-24

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties.

  8. Photocatalytic and antibacterial properties of phytosynthesized CeO2 NPs using Moringa oleifera peel extract.

    Science.gov (United States)

    Surendra, T V; Roopan, Selvaraj Mohana

    2016-08-01

    Biosynthetic methods are alternative approaches which are much safer than the normal techniques (physical and chemical) used for the methods for synthesis of metal nanoparticles. The benefits are sample as it is economic and environment friendly. Herein present investigation, we have reported a microwave mediated eco-friendly synthetic approach for preparing cerium oxide (CeO2) nanoparticles. Here, we used Moringa oleifera peel as the stabilizing and reducing agent towards synthesize of Ce2O NPs via microwave irradiation. The NPs were further characterized using UV-Vis, FT-IR, XRD and HR-TEM techniques. The FTIR analysis confirmed the phytochemical involvement in NPs stabilization. The crystallinity of CeO2 nanoparticles are well demonstrated through X-ray Diffraction and HR-TEM. The TEM images reveal the spherical shape of the CeO2 NPs having an average size of 45nm. Additionally, these CeO2 NPs were used successfully as a catalyst in the degradation of the dye, crystal violet. Also the antibacterial activity of the synthesized CeO2 NPs was evaluated using Staphylococcus aureus (Gram positive bacteria) and Escherichia coli (Gram negative bacteria). CeO2 NPs showed better activity on E. coli than S. aureus. We have demonstrated an eco-friendly preparation of CeO2 nanoparticles, a good photocatalyst and having better antibacterial properties.

  9. Effects of Surfactants on the Performance of CeO2 Humidity Sensor

    Directory of Open Access Journals (Sweden)

    Chunjie Wang

    2014-01-01

    Full Text Available Nanosized CeO2 powders were synthesized via hydrothermal method with different types of surfactants (polyethylene glycol (PEG, cetyltrimethylammonium bromide (CTAB, and sodium dodecylbenzenesulfonate (SDBS. X-ray diffraction, Raman spectroscopy, and transmission electron microscopy were utilized to characterize the phase structures and morphologies of the products. The sample with CTAB as surfactant (CeO2-C has the largest specific surface area and the smallest particle size among these three samples. The humidity sensor fabricated by CeO2-C shows higher performance than those used CeO2-P and CeO2-S. The impedance of the CeO2-C sensor decreases by about five orders of magnitude with relative humidity (RH changing from 15.7 to 95%. The response and recovery time are 7 and 7 s, respectively. These results indicate that the performance of CeO2 humidity sensors can be improved effectively by the addition of cationic surfactant.

  10. Role of vacancies, light elements and rare-earth metals doping in CeO2

    Science.gov (United States)

    Shi, H.; Hussain, T.; Ahuja, R.; Kang, T. W.; Luo, W.

    2016-01-01

    The magnetic properties and electronic structures of pure, doped and defective cerium oxide (CeO2) have been studied theoretically by means of ab initio calculations based on the density function theory (DFT) with the hybrid HF/DFT technique named PBE0. Carbon (C), nitrogen (N), phosphorus (P), sulphur (S), lanthanum (La) and praseodymium (Pr) doped in CeO2 and CeO2 containing oxygen vacancies (Ov) were considered. Our spin-polarized calculations show that C, N, Pr dopants and Ov defects magnetize the non-magnetic CeO2 in different degree. The optical band gap related to photocatalysis for pure CeO2, corresponding to the ultraviolet region, is reduced obviously by C, N, S, Pr impurities and oxygen vacancies, shifting to the visible region and even further to the infrared range. Especially, N-, S- and Pr-doped CeO2 could be used to photocatalytic water splitting for hydrogen production. As the concentration of Ov increasing up to 5%, the CeO2 exhibits a half-metallic properties. PMID:27554285

  11. Preparation for CeO2/Nanographite Composite Materials and Electrochemical Degradation of Phenol by CeO2/Nanographite Cathodes.

    Science.gov (United States)

    Yu, Li; Yu, Xiujuan; Sun, Tianyi; Wang, Na

    2015-07-01

    CeO2/nanographite (CeO2/nano-G) composite materials were got by chemical precipitation method with nanographite (nano-G) and cerous nitrate hexahydrate as raw materials. The microstructures of CeO2/nano-G composite materials were characterized by means of SEM, XRD, XPS and Raman. The cathodes were made by nano-G and CeO2/nano-G composite materials, respectively. The electrolysis phenol was conducted by the diaphragm cell prepared cathode and the Ti/RuO2 anode. The results indicated that the Cerium oxide is mainly in nanoscale spherical state, uniformly dispersed in the nanographite sheet surface, and there are two different oxidation states for elemental Ce, namely, Ce(III) and Ce(IV). In the diaphragm electrolysis system with the aeration conditions, the degradation rate of phenol reached 93.9% under 120 min's electrolysis. Ceria in the cathode materials might lead to an increase in the local oxygen concentration, which accelerated the two-electron reduction of O2 to hydrogen peroxide (H2O2). The removal efficiency of phenol by using the CeO2/nano-G composite cathode was better than that of the nano-G cathode.

  12. Buffer layers for high-Tc thin films on sapphire

    Science.gov (United States)

    Wu, X. D.; Foltyn, S. R.; Muenchausen, R. E.; Cooke, D. W.; Pique, A.; Kalokitis, D.; Pendrick, V.; Belohoubek, E.

    1992-01-01

    Buffer layers of various oxides including CeO2 and yttrium-stabilized zirconia (YSZ) have been deposited on R-plane sapphire. The orientation and crystallinity of the layers were optimized to promote epitaxial growth of YBa2Cu3O(7-delta) (YBCO) thin films. An ion beam channeling minimum yield of about 3 percent was obtained in the CeO2 layer on sapphire, indicating excellent crystallinity of the buffer layer. Among the buffer materials used, CeO2 was found to be the best one for YBCO thin films on R-plane sapphire. High Tc and Jc were obtained in YBCO thin films on sapphire with buffer layers. Surface resistances of the YBCO films were about 4 mOmega at 77 K and 25 GHz.

  13. Violet/blue photoluminescence from CeO2 thin film

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    CeO2 thin film was fabricated by dual ion beam epitaxial technique. The violet/blue PL at room temperature and lower temperature was observed from the CeO2 thin film. After the analysis of crystal structure and valence in the compound was carried out by the XRD and XPS technique, it was inferred that the origin of CeO2 PL was due to the electrons transition from Ce4f band to O2p band and the defect level to O2p band. And these defects levels were located in the range of 1 eV around Ce4f band.

  14. Effect of CeO2 on Sintering and Hydration Resistance of Natural Dolomite

    Institute of Scientific and Technical Information of China (English)

    XUYan-qing; CHENZhao-you

    1996-01-01

    The sinteribility and hydration resistance of high pure natural dolomite doped with CeO2 addition were studied.It is found that the addition of CeO2 to dolomite can significantly improve the sintering and the resistane to hydration of dolomite.Doping 0.25% CeO2,followed by firing at 1600℃ for 4 hours,a dense doloma clinker with bulk density>3.25 g/cm3, apparent porosity<1.0% and excellent hydration resistance has been obtained.

  15. Dynamics of a single trapped ion immersed in a buffer gas

    CERN Document Server

    Höltkemeier, Bastian; López-Carrera, Henry; Weidemüller, Matthias

    2016-01-01

    We provide a comprehensive theoretical framework for describing the dynamics of a single trapped ion interacting with a neutral buffer gas, thus extending our previous studies on buffer-gas cooling of ions beyond the critical mass ratio [B. H\\"oltkemeier et al., Phys. Rev. Lett. 116, 233003 (2016)]. By transforming the collisional processes into a frame, where the ion's micromotion is assigned to the buffer gas atoms, our model allows one to investigate the influence of non-homogeneous buffer gas configurations as well as higher multipole orders of the radio-frequency trap in great detail. Depending on the neutral-to-ion mass ratio, three regimes of sympathetic cooling are identified which are characterized by the form of the ion's energy distribution in equilibrium. We provide analytic expressions and numerical simulations of the ion's energy distribution, spatial profile and cooling rates for these different regimes. Based on these findings, a method for actively decreasing the ion's energy by reducing the ...

  16. Effect of magnetic structural processing on structure and texture of La2Zr2O7 buffer layers

    Science.gov (United States)

    Chibirova, F. Kh.; Kotina, G. V.; Bovina, E. A.; Tarasova, D. V.; Polisan, A. A.; Parkhomenko, Yu. N.

    2016-11-01

    Epitaxial CeO2 seed layer and La2Zr2O7 (LZO) buffer layers were deposited on biaxially-textured Ni-5 at.% W (NiW) tape substrate by liquid-phase polymer assisted nanoparticles deposition (PAND) method. LZO layers deposited by PAND have consistently shown tilting of the c-axis toward the direction of the sample’s surface normal. A new approach increasing the sharpening of the buffer texture by magnetic structural processing (MSP) of buffer layers was tested. The LZO layers, deposited on the seed and buffer layers after MSP, have dense and smooth surface structure, and more importantly, significantly improved out-of-plane texture, compared with the LZO layers that were deposited on a layer without MSP. Transmission electron microscopy study confirmed the c-axis tilting of CeO2 and LZO layers and revealed the absence of interfaces between LZO layers which have been grown on the layers after MSP. There are very small (2-4 nm) gated pores in the single-crystal structure of LZO layers that are not typical for structure of LZO layers obtained by liquid-phase methods. Thus the LZO buffer layers can serve as an effective metal-ion diffusion barrier.

  17. CeO2-Co3O4 Catalysts for CO Oxidation

    Institute of Scientific and Technical Information of China (English)

    Xu Xiuyan; Li Jinjun; Hao Zhengping

    2006-01-01

    CeO2-Co3O4 catalysts for low-temperature CO oxidation were prepared by a co-precipitation method.In combination with the characterization methods of N2 adsorption/desorption, XRD, temperature-programmed reduction (TPR), and FT-IR, the influence of the cerium content on the catalytic performance of CeO2-Co3O4 was investigated.The results indicate that the prepared CeO2-Co3O4 catalysts exhibit a better activity than that of pure CeO2 or pure Co3O4.The catalyst with the Ce/Co atomic ratio 1:16 exhibits the best activity, which converts 77% of CO at room temperature and completely oxidizes CO at 45 ℃.

  18. The Preparation, Characterization and Photocatalytic Activity of Mixed P25/CeO2 Nanocomposites

    Science.gov (United States)

    Liu, I.-Tsan; Hon, Min-Hsiung; Teoh, Lay Gaik

    2017-01-01

    This study uses the wet chemical method to synthesize P25 (TiO2)/CeO2 composites by mixing P25 and Ce(NO3)3·6H2O at different volumetric concentrations. X-ray diffraction, transmission electron microscopy and ultraviolet-visible diffuse reflectance spectroscopy are used to analyze the structure, morphology, optical properties and photocatalytic activity of the TiO2/CeO2 composites with different compositions. The pollutant, methylene blue solution, was used for analysis. The results show that the photocatalytic activity of the composite catalysts is greater than that of pure TiO2 or pure CeO2. The catalyst, TiO2 55%/CeO2 (v/v), exhibits the greatest level of photocatalytic activity.

  19. Fruit juice extract mediated synthesis of CeO2 nanoparticles for antibacterial and photocatalytic activities

    Science.gov (United States)

    Reddy Yadav, L. S.; Manjunath, K.; Archana, B.; Madhu, C.; Raja Naika, H.; Nagabhushana, H.; Kavitha, C.; Nagaraju, G.

    2016-05-01

    Ceria ( CeO2 is a technologically important rare-earth material because of its unique properties and various engineering/biological applications. In the present work, cerium oxide nanoparticles have been prepared by a simple solution combustion method using watermelon juice as a novel combustible fuel. The structure and morphology of the synthesized CeO2 nanoparticles were analyzed using various analytical tools such as PXRD, FTIR, Raman, UV-Visible and SEM. PXRD pattern confirms that the prepared material is composed of cubic-phase cerium oxide nanoparticles. Photocatalytic degradation of Methylene blue dye using CeO2 nanoparticles shows 98% of degradation in UV irradiations. Furthermore the antibacterial properties of CeO2 nanoparticles were investigated by their bacterial activity against two bacterial strains using the agar well diffusion method.

  20. Study on Sulfation of CeO2/γ-Al2O3 Sorbent in Simulated Flue Gas

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The sulfation of CeO2/γ-Al2O3 sorbent in simulated flue gas was studied. A series of CeO2/γ-Al2O3 sorbents with different CeO2 loadings were prepared by impregnation and characterized by X-ray diffraction. Thermogravimetric technique was used to study the sulfation of CeO2/γ-Al2O3 sorbents, mainly on the CeO2 loading, sulfation cycles, and intrinsic kinetics. The study revealed that monolayer coverage of CeO2 supported on γ-Al2O3 was 0.125 g CeO2/g (γ-Al2O3). Below monolayer coverage, CeO2 was highly dispersed on γ-Al2O3. The optimal CeO2 loading on sulfation was 0.03 g CeO2/g (γ-Al2O3). CeO2/γ-Al2O3 sorbent was recyclable by controlling sulfation time. Intrinsic kineticd equation was R=1.1394×10-4×exp (-1,508.39/T) mg·mg-1·s-1. Activation energy and reaction order were 12.54 kJ·mol-1 and first order, respectively.

  1. MODIFICATION OF CeO2 AND ITS EFFECT ON THE HEAT-RESISTANCE OF SILICONE RUBBER

    Institute of Scientific and Technical Information of China (English)

    Teng-fei Gan; Bao-qing Shentu; Zhi-xue Weng

    2008-01-01

    By means of the wet chemical surface modification, the surface of CeO2 was modified by vinyltrimethoxysilane (VTMS). Infrared spectroscopy was used to investigate the structure of the modified CeO2 and the result showed that VTMS has been attached onto the surface of CeO2. Effect of VTMS concentration on the active index of the modified CeO2 was also studied, and the result indicated that the active index of the modified CeO2 increases with the increase of VTMS concentration and the optimal concentration of VTMS is 10 wt%. The effect of the modified CeO2 on the tear strength of silicone rubber before and after aging was studied and it was found that in comparison with the unmodified CeO2 the addition of the modified CeO2 results in the significant increase of the tear strength before ageing due to the increase of the crosslinking density of silicone rubber under the experimental conditions. The tear strength of silicone rubber filled with the modified CeO2 after ageing is higher than that with the unmodified CeO2, indicating that the modification of CeO2 can improve the heat-resistance of silicone rubber.

  2. Toxicity of CeO2 nanoparticles - the effect of nanoparticle properties.

    Science.gov (United States)

    Leung, Yu Hang; Yung, Mana M N; Ng, Alan M C; Ma, Angel P Y; Wong, Stella W Y; Chan, Charis M N; Ng, Yip Hang; Djurišić, Aleksandra B; Guo, Muyao; Wong, Mabel Ting; Leung, Frederick C C; Chan, Wai Kin; Leung, Kenneth M Y; Lee, Hung Kay

    2015-04-01

    Conflicting reports on the toxicity of CeO2 nanomaterials have been published in recent years, with some studies finding CeO2 nanoparticles to be toxic, while others found it to have protective effects against oxidative stress. To investigate the possible reasons for this, we have performed a comprehensive study on the physical and chemical properties of nanosized CeO2 from three different suppliers as well as CeO2 synthesized by us, and tested their toxicity. For toxicity tests, we have studied the effects of CeO2 nanoparticles on a Gram-negative bacterium Escherichia coli in the dark, under ambient and UV illuminations. We have also performed toxicity tests on the marine diatom Skeletonema costatum under ambient and UV illuminations. We found that the CeO2 nanoparticle samples exhibited significantly different toxicity, which could likely be attributed to the differences in interactions with cells, and possibly to differences in nanoparticle compositions. Our results also suggest that toxicity tests on bacteria may not be suitable for predicting the ecotoxicity of nanomaterials. The relationship between the toxicity and physicochemical properties of the nanoparticles is explicitly discussed in the light of the current results.

  3. Leucas aspera mediated multifunctional CeO2 nanoparticles: Structural, photoluminescent, photocatalytic and antibacterial properties.

    Science.gov (United States)

    Malleshappa, J; Nagabhushana, H; Sharma, S C; Vidya, Y S; Anantharaju, K S; Prashantha, S C; Daruka Prasad, B; Raja Naika, H; Lingaraju, K; Surendra, B S

    2015-01-01

    Spherical shaped cerium dioxide (CeO2) nanoparticles (NPs) were synthesized via bio mediated route using Leucas aspera (LA) leaf extract. The NPs were characterized by PXRD, SEM, UV-Visible techniques. Photoluminescence (PL), photocatalysis and antibacterial properties of NPs were studied. PXRD patterns and Rietveld analysis confirm cubic fluorite structure with space group Fm-3m. SEM results evident that morphology of the NPs was greatly influenced by the concentration of LA leaf extract in the reaction mixture. The band gap energy of the NPs was found to be in the range of 2.98-3.4 eV. The photocatalytic activity of NPs was evaluated by decolorization of Rhodamine-B (RhB) under UVA and Sun light irradiation. CeO2 NPs show intense blue emission with CIE coordinates (0.14, 0.22) and average color coordinated temperature value ∼148,953 K. Therefore the present NPs quite useful for cool LEDs. The superior photocatalytic activity was observed for CeO2 NPs with 20 ml LA under both UVA and Sunlight irradiation. The enhanced photocatalytic activity and photoluminescent properties were attributed to defect induced band gap engineered CeO2 NPs. Further, CeO2 with 20 ml LA exhibit significant antibacterial activity against Escherichia coli (EC) and Staphylococcus aureus (SA). These findings show great promise of CeO2 NPs as multifunctional material for various applications.

  4. Surface reaction network of CO oxidation on CeO2/Au(110) inverse model catalysts.

    Science.gov (United States)

    Ding, Liangbing; Xiong, Feng; Jin, Yuekang; Wang, Zhengming; Sun, Guanghui; Huang, Weixin

    2016-11-30

    CeO2/Au(110) inverse model catalysts were prepared and their activity toward the adsorption and co-adsorption of O2, CO, CO2 and water was studied by means of X-ray photoelectron spectroscopy, low energy electron diffraction, thermal desorption spectra and temperature-programmed reaction spectra. The Au surface of CeO2/Au(110) inverse model catalysts molecularly adsorbs CO, CO2 and water, and the polycrystalline CeO2 surface of CeO2/Au(110) inverse model catalysts molecularly adsorbs O2, and molecularly and reactively adsorbs CO, CO2 and water. By controllably preparing co-adsorbed surface species on CeO2/Au(110) inverse model catalysts, we successfully identified various surface reaction pathways of CO oxidation to produce CO2 with different barriers both on the CeO2 surface and at the Au-CeO2 interface, including CO oxidation by various oxygen species, and water/hydroxyl group-involved CO oxidation. These results establish a surface reaction network of CO oxidation catalyzed by Au/CeO2 catalysts, greatly advancing the fundamental understandings of catalytic CO oxidation reactions.

  5. Enhanced photocatalytic performances of CeO2/TiO2 nanobelt heterostructures.

    Science.gov (United States)

    Tian, Jian; Sang, Yuanhua; Zhao, Zhenhuan; Zhou, Weijia; Wang, Dongzhou; Kang, Xueliang; Liu, Hong; Wang, Jiyang; Chen, Shaowei; Cai, Huaqiang; Huang, Hui

    2013-11-25

    CeO2 /TiO2 nanobelt heterostructures are synthesized via a cost-effective hydrothermal method. The as-prepared nanocomposites consist of CeO2 nanoparticles assembled on the rough surface of TiO2 nanobelts. In comparison with P25 TiO2 colloids, surface-coarsened TiO2 nanobelts, and CeO2 nanoparticles, the CeO2 /TiO2 nanobelt heterostructures exhibit a markedly enhanced photocatalytic activity in the degradation of organic pollutants such as methyl orange (MO) under either UV or visible light irradiation. The enhanced photocatalytic performance is attributed to a novel capture-photodegradation-release mechanism. During the photocatalytic process, MO molecules are captured by CeO2 nanoparticles, degraded by photogenerated free radicals, and then released to the solution. With its high degradation efficiency, broad active light wavelength, and good stability, the CeO2 /TiO2 nanobelt heterostructures represent a new effective photocatalyst that is low-cost, recyclable, and will have wide application in photodegradation of various organic pollutants. The new capture-photodegradation-release mechanism for improved photocatalysis properties is of importance in the rational design and synthesis of new photocatalysts.

  6. Corrosion Resistance of an electrodeposited Zinc Coating Containing CeO2 Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    HE Jian-ping; LUO Xin-yi; CHEN Su-jing; WANG Xian-you

    2004-01-01

    A Zinc coating containing CeO2 nanoparticles has been deposited by electrodeposition in a zinc plating bath.The content of CeO2 in the coating is 0.22 mass%. The results of weight loss experiments and electrochemistry tests show that corrosion resistance of the Zinc coating containing CeO2 nanoparticles is remarkably improved in contrast to the pure zinc coating in 0.5 M MgSO4 solution. The effects of CeO2 microparticles on the corrosion resistance of the zinc coating have been studied, the results show that CeO2 microparticles have no effect on the corrosion resistance of the zinc coating. SEM and XRD experiments suggest that the presence of CeO2 nanoparticles in the coating causes the modification of the surface morphology and preferential orientation of the crystal planes; therefore, the reason for the enhancement of corrosion resistance is mainly related to improvement of the structure of the coating.

  7. Hexagonal CeO2 nanostructures: an efficient electrode material for supercapacitors.

    Science.gov (United States)

    Maheswari, Nallappan; Muralidharan, Gopalan

    2016-09-28

    Cerium oxide (CeO2) has emerged as a new and promising pseudocapacitive material due to its prominent valance states and extensive applications in various fields. In the present study, hexagonal CeO2 nanostructures have been prepared via the hydrothermal method employing cationic surfactant cetyl trimethyl ammonium bromide (CTAB). CTAB ensures a slow rate of hydrolysis to form small sized CeO2 nanostructures. The role of calcination temperature on the morphological, structural, electrochemical properties and cyclic stability has been assessed for supercapacitor applications. The mesoscopic hexagonal architecture endows the CeO2 with not only a higher specific capacity, but also with an excellent rate capability and cyclability. When the charge/discharge current density is increased from 2 to 10 A g(-1) the reversible charge capacity decreased from 927 F g(-1) to 475 F g(-1) while 100% capacity retention at a high current density of 20 A g(-1) even after 1500 cycles could be achieved. Furthermore, the asymmetric supercapacitor based on CeO2 exhibited a significantly higher energy density of 45.6 W h kg(-1) at a power density of 187.5 W kg(-1) with good cyclic stability. The electrochemical richness of the CeO2 nanostructure makes it a suitable electrode material for supercapacitor applications.

  8. Activity improvement of Pt/C catalysts by adding CeO2 nanoparticles

    Institute of Scientific and Technical Information of China (English)

    YANG Yuying; ZHANG Ziyu; HU Zhongai

    2011-01-01

    Carbon-supported platinum catalysts were prepared by NaBH4 reduction of metal precursors and the CeO2 nanoparticles were prepared by citric acid sol-gel method. The structure and morphology of two kinds of nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The Pt particles were uniformly dispersed on the carbon surface and showed the rod-like morphology. The CeO2 was spherical in shape. The appropriate amount of CeO2 nanoparticles was added into Pt/C systems to improve activity of the catalysts. Several electrochemical techniques such as cyclic voltammogram (CV), chronoamperometry (I-t)and electrochemical impedance spectroscopy (EIS) were used to investigate the properties of CeO2-Pt/C catalysts for methanol electrooxidation in 1 mol/L CH3OH+0.5H2SO4 aqueous solutions. The results revealed that compared with Pt/C catalysts CeO2-pt/C exhibited a higher activity and stability for methanol electro-oxidation. Moreover, the effect of CeO2 content on the activity of Pt/C catalysts was discussed in detail.

  9. New CeO2 nanoparticles-based topical formulations for the skin protection against organophosphates

    Directory of Open Access Journals (Sweden)

    Arnaud Zenerino

    2015-01-01

    Full Text Available To reinforce skin protection against organophosphates (OPs, the development of new topical skin protectants (TSP has received a great interest. Nanoparticles like cerium dioxide (CeO2 known to adsorb and neutralize OPs are interesting candidates for TSP. However, NPs are difficult to disperse into formulations and they are suspected of toxicological issues. Thus, we want to study: (1 the effect of the addition of CeO2 NPs in formulations for the skin protection (2 the impact of the doping of CeO2 NPs by calcium; (3 the effect of two methods of dispersion of CeO2 NPs: an O/W emulsion or a suspension of a fluorinated thickening polymer (HASE-F grafted with these NPs. As a screening approach we used silicone membranes as a skin equivalent and Franz diffusion cells for permeation tests. The addition of pure CeO2 NPs in both formulations permits the penetration to decrease by a 3–4-fold factor. The O/W emulsion allows is the best approach to obtain a film-forming coating with a good reproducibility of the penetration results; whereas the grafting of NPs to a thickener is the best way to obtain an efficient homogenous suspension of CeO2 NPs with a decreased of toxicological impact but the coating is less film-forming which slightly impacts the reproducibility of the penetration results.

  10. Influence of CeO2 nanoparticles on growth and physiology of sorghum

    Science.gov (United States)

    Mu, Linlin; Liang, Wei-zhen; Kinsey, Erin; Rauh, Bradley; Kresovich, Stephen; Darnault, Christophe

    2016-04-01

    Cerium oxide nanoparticles (CeO2 NPs) are commonly used as polishing agents for industry and fuel additives to decrease the particulate matter emissions. CeO2 NPs may be encountered in the soil and water environment through their life cycle or accidental releases, and have potential phytotoxicity effects. Therefore, it is critical to assess the potential effects of CeO2 NPs in soil on plant growth and physiology. The objective of this research is to determine the physiological responses of three sorghums (Grassl, BtX623 and Rio) to the effect of CeO2 nanoparticles in potting soil environment. Sorghums were germinated and grown in potting soil in the greenhouse for three weeks cultivation with treatments of 0, 100, 500, 1000 mg CeO2 NPs per kg soil. Plant parameters, such as length, weight, and biomass of root and leaves were measured in each treatment with 12 replications. After three weeks germination, the sorghum plants were dig out and the roots were examined and scanned by the Silverfast SE Plus scanner to compare and analyze their dimensions and shapes. To further study the growth and physiological changes in plants due to the presence of CeO2 NPs in soil, one selected type of sorghum (Grassl) was grown under the four different CeO2 NPs concentration treatments for six months until plant maturity, and was also cut and harvested three times to study CeO2 NPs effect on plant re-growth. At the end of each growing period, above ground vegetative tissues were air-dried, grounded to 2mm particle size and compositional traits were estimated by using near-infrared spectroscopy. The influence of nanoparticles was observed on some of the plant traits. Preliminary results showed the influence of CeO2 NPs on the roots growth, as Grassl and Btx623 in 100 mgkg-1 treatment grew significantly faster than other concentrations; however no significant difference between control and 100 mgkg-1 treatment in Rio. CeO2 NPs concentration of 100 mgkg-1 had no impact on sorghum growth, compared to the control treatment. Results of the six months growth and repetitive cutting experiments indicated that the different treatments, including the presence and/or concentrations of the nanoparticles, impacted some of the compositional traits of sorghum.

  11. A finite-buffer queue with a single vacation policy: An analytical study with evolutionary positioning

    Directory of Open Access Journals (Sweden)

    Woźniak Marcin

    2014-12-01

    Full Text Available In this paper, application of an evolutionary strategy to positioning a GI/M/1/N-type finite-buffer queueing system with exhaustive service and a single vacation policy is presented. The examined object is modeled by a conditional joint transform of the first busy period, the first idle time and the number of packets completely served during the first busy period. A mathematical model is defined recursively by means of input distributions. In the paper, an analytical study and numerical experiments are presented. A cost optimization problem is solved using an evolutionary strategy for a class of queueing systems described by exponential and Erlang distributions.

  12. Synthesis of CeO2/fly ash cenospheres composites as novel photocatalysts by modified pyrolysis process

    Institute of Scientific and Technical Information of China (English)

    张进; 王冰; 崔皓; 李闯; 翟建平; 李琴

    2014-01-01

    A novel fly ash cenospheres (FACs)-supported CeO2 composite (CeO2/FACs) was successfully synthesized by the modi-fied pyrolysis process. The prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflection spectra (DRS) techniques. XRD results indicated that the CeO2 film coated on cenospheres was a face-centered cubic structure. SEM images confirmed that the CeO2 film was relatively com-pact. XPS results showed that Ce was present as both Ce4+and Ce3+oxidation states in CeO2 film coated on FACs substrate. The bandgap of the composite was narrower compared with the pure CeO2. The as-prepared material exhibited good photocatalytic activ-ity for the decolorization of methylene blue (MB) under visible light irradiation, and the first-order reaction rate constant (k) of 0.0028 min–1 for CeO2/FACs composite was higher than 0.0015 min–1 of pure CeO2. The fact that they floated on water meant that CeO2/FACs composites were easily recovered from water by filtration after the reaction. The recycling test revealed that the compos-ites were quite stable during the MB photocatalytic decolorization. The CeO2/FACs catalyst was therefore promising for practical use in the degradation of pollutants or water cleanup.

  13. Physical Properties and Hydration Resistance of CeO2—and CeO2/Fe2O3—Bearing Dolomite Refractory Products

    Institute of Scientific and Technical Information of China (English)

    XUYanqing; CHENKaixian

    1998-01-01

    Dolomite refractory products with excellent hydration resistance have been produced by using CeO2-and CeO2/Fe2O3-bearing dolomite clinkers,Their physical properties as well as hydration resistance have been investigated,The addition of CeO2 has little harmful effect on the high temperature properties of dolomite refractory products such as hot MOR and slag resistance,And the shelf lives of the dolomite refractory products containing CeO2 and CeO2/Fe2O3 additions at the same condition are two times that of the common dolomite refractory produt.The dolomite refractory product containing CeO2/Fe2O3 combination possesses the best hydration resistance,but gives poor slag resistance.

  14. Effect of Co3O4 and Co3O4/CeO2 infiltration on the catalytic and electro-catalytic activity of LSM15/CGO10 porous cells stacks for oxidation of propene

    DEFF Research Database (Denmark)

    Ippolito, Davide; Kammer Hansen, Kent

    2015-01-01

    The objective of this work was to study the effect of Co3O4 and Co3O4/CeO2 infiltration on the propene oxidation catalytic activity of a La0.85Sr0.15MnO3/Ce0.9Gd0.1O1.95 electrochemical porous cell stack (11 layers, 5 single cells in series). The effect of the infiltration of Co3O4 and Co3O4/CeO2...... on the electrochemical properties of the porous cell stack was also investigated by electrochemical impedance spectroscopy (EIS). Co3O4 and Co3O4/CeO2 exhibited high catalytic activity for propene oxidation. The increase of propene oxidation rate with +4 V (0.8 V/cell) polarization reached 10% for the Co3O4 infiltrated...... reactor and 48% of efficiency at 300 °C. The Co3O4/CeO2 co-infiltration decreased the reactor polarization resistance, while Co3O4 infiltration had negligible effect on reactor electrochemical performance. The beneficial effect of CeO2 on the electrode activity was attributed to the increased...

  15. Electrocatalytic enhancement of methanol oxidation by adding CeO2 nanoparticle on porous electrode

    Institute of Scientific and Technical Information of China (English)

    FENG Xiaojuan; SHI Yanlong; ZHOU Huijuan

    2012-01-01

    The polyaniline/polysulfone (PAN/PSF) composite films were prepared by electropolymerization,and then CeO2-Pt particles were codeposited into this composite film to obtain the CeO2-Pt-modified polyaniline/polysulfone (CeO2-Pt/PAN/PSF) electrodes.Their morphology and chemical component were characterized by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS),respectively.The results showed that the composite film had bi-layer structure with asymmetrical pores,and platinum and cerium oxide particles were homogeneously dispersed in the modified film electrodes.The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques were applied to investigate the electrocatalytic activity of the Pt-CeO2/PAN/PSF electrodes.It was indicated that appropriate amount of CeO2 could enhance the catalytic activity of Pt for methanol electro-oxidation.Chronoamperometry (i-t)measurements revealed that the Pt-CeO2/PAN/PSF electrode was relatively endurable for intermediate production.In addition,different mixing amounts of Pt and CeO2 nanoparticles were also investigated in detail.

  16. Imaging the atomic surface structures of CeO2 nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yuyuan [Northwestern University, Evanston; Wu, Zili [ORNL; Wen, Jianguo [Argonne National Laboratory (ANL); Poeppelmeier, Kenneth R [Northwestern University, Evanston; Marks, Laurence D [Northwestern University, Evanston

    2014-01-01

    Atomic surface structures of CeO2 nanoparticles are under debate owing to the lack of clear experimental determination of the positions of the surface oxygen atoms. Particularly controversial is the (100) surface structure of this material. In this study, with oxygen atoms clearly observed using aberration corrected high resolution electron microscopy, we determined the atomic structures of the (100), (110) and (111) surfaces of CeO2 nanocubes. The predominantly exposed (100) surface has a mixture of Ce, O, and reduced CeO terminations, underscoring the complex structures of this polar surface that previously was often oversimplified. The (110) surface shows saw-like (111) nanofacets and flat CeO2-x terminations with oxygen vacancies. The (111) surface has an O termination. As these three low index surfaces are the most often exposed facets in the majority of CeO2 nanoparticles, these findings can be extended to the surfaces of differently shaped CeO2 nanoparticles as well as provide insight about face-selective catalysis.

  17. Growth and Electronic Properties of Ag Nanoparticles on Reduced CeO2-x(111) Films

    Institute of Scientific and Technical Information of China (English)

    Dan-dan Kong; Yong-he Pan; Guo-dong Wang; Hai-bin Pan; Jun-fa Zhu

    2012-01-01

    Ag nanoparticles grown on reduced CeO2-x thin films have been studied by X-ray photoelectron spectroscopy and resonant photoelectron spectroscopy of the valence band to understand the effect of oxygen vacancies in the CeO2-x thin films on the growth and interfacial electronic properties of Ag.Ag grows as three-dimensional particles on the CeO2-x(111) surface at 300 K.Compared to the fully oxidized ceria substrate surface,Ag favors the growth of smaller particles with a larger particle density on the reduced ceria substrate surface,which can be attributed to the nucleation of Ag on oxygen vacancies.The binding energy of Ag3d increases when the Ag particle size decreases,which is mainly attributed to the final-state screening.The interfacial interaction between Ag and CeO2-x(111) is weak.The resonant enhancement of the 4f level of Ce3+ species in RPES indicates a partial Ce4+→Ce3+ reduction after Ag deposited on reduced ceria surface.The sintering temperature of Ag on CeO 1.85 (111) surface during annealing is a little higher than that of Ag on CeO2 (111) surface,indicating that Ag nanoparticles are more stable on the reduced ceria surface.

  18. Effects of pH and phosphate on CeO2 nanoparticle dissolution.

    Science.gov (United States)

    Dahle, Jessica T; Livi, Ken; Arai, Yuji

    2015-01-01

    As the result of rapidly grown nanotechnology industries, release of engineered nanoparticles (ENPs) to environment has increased, posing in a serious risk to environmental and human health. To better understand the chemical fate of ENPs in aquatic environments, solubility of CeO2 NPs was investigated using batch dissolution experiments as a function of pH (1.65-12.5), [phosphate] and particle size (33 and 78 nm). It was found that CeO2 dissolution was only significant at pHCeO2 NPs was decreased in small NPs by 15% at pH 1.65 and 75% at pH 4.5 and in large NPs by 56% at pH 1.65 and 63% at pH 4.5. The inner-sphere surface complexation of P that is revealed by the zeta potential measurements is effectively suppressing the CeO2 NP dissolution. Predicting the fate and transport of CeO2 NPs in aquatic environment, pH and P ligands might play important roles in controlling the solubility of CeO2 NPs.

  19. Morphology-controllable synthesis and characterization of CeO2 nanocrystals

    Institute of Scientific and Technical Information of China (English)

    Yangfeng Huang; Yebin Cai; Dongkai Qiao; Hao Liu

    2011-01-01

    CeO2 nanocrystals with different morphologies were synthesized by adjusting the pH value of the starting solution in water-in-oil microemulsion. The obtained samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis and different thermal analysis (TGA/DTA), Brunauer-Emmet-Teller (BET) surface area measurement, ultraviolet-visible absorption (UV-vis) spectroscopy and photoluminescence (PL) spectroscopy. Results show that the morphologies of CeO2 were transformed from granular to spherical and to rod-like while the pH of the starting solution varied from 5 to 8 and to 11. All samples were indexed to the phase of CeO2 and Ce(OH)4, and the molar ratio of CeO2 to Ce(OH)4 was deduced to be about 0.25. The morphologies of CeO2 nanocrystals had but slight influence on their specific surface areas, LV-vis spectra and PL spectra. The band gap energies of different morphological samples were estimated by LV-vis spectroscopic method.

  20. Effect of La2O3/CeO2 particle size on high-temperature oxidation resistance of electrodeposited Ni-La2O3/CeO2 composites%La2O3/CeO2颗粒尺寸对Ni-La2O3/CeO2复合电镀层高温氧化性能的影响

    Institute of Scientific and Technical Information of China (English)

    孟君晟; 吉泽升

    2014-01-01

    Ni−La2O3/CeO2composite films were prepared by electrodeposition from a nickel sulfate bath containing certain content of micrometer and nanometer La2O3/CeO2 particles. The effect of La2O3 or CeO2 particle size on the oxidation resistance of the electrodeposited Ni−La2O3/CeO2 composites in air at 1000 °C was studied. The results indicate that, compared with the electrodeposited Ni-film, Ni−La2O3/CeO2 composites exhibit a superior oxidation resistance due to the codeposited La2O3 or CeO2 particles blocking the outward diffusion of nickel. Moreover, compared with nanoparticles, La2O3 or CeO2 microparticles have stronger effect because La2O3 or CeO2 microparticles also act as a diffusion barrier layer at the onset of oxidation.%通过向普通硫酸镍电镀液中添加一定含量的微米或纳米La2O3/CeO2颗粒,采用复合电镀制备微米或纳米La2O3/CeO2颗粒分布的Ni基复合镀层,并研究La2O3/CeO2颗粒尺寸对Ni−La2O3/CeO2复合镀层在1000°C抗氧化性能的影响。结果表明:与普通 Ni 镀层相比,Ni−La2O3/CeO2复合镀层中的 La2O3/CeO2颗粒通过溶解扩散进入氧化膜中,阻碍Ni的外扩散,从而降低氧化速度;此外,与La2O3/CeO2纳米颗粒相比,La2O3/CeO2微米颗粒在氧化初期还起到扩散障碍层的作用,对阻碍Ni的外扩散具有更强的作用。

  1. CeO_2-supported vanadium oxide catalysts for soot oxidation:the roles of molecular structure and nanometer effect

    Institute of Scientific and Technical Information of China (English)

    刘坚; 赵震; 徐春明; 段爱军; 姜桂元

    2010-01-01

    The nanometer CeO2 powder was prepared by the method of microwave-assisted heating hydrolysis,and the nanometer CeO2-supported or ordinary CeO2-supported vanadia catalysts with different vanadium loadings(atomic ratios:100V/Ce=0.1,1,4,10,and 20) were prepared by an incipient-wetness impregnation method.Spectroscopic techniques(XRD,FT-IR,Raman and UV-Vis DRS) were utilized to characterize the structures of VOx/CeO2 catalysts.The results showed that the structures of CeO2-supported vanadium oxide catalysts de...

  2. Particle-specific toxicity and bioavailability of cerium oxide (CeO2) nanoparticles to Arabidopsis thaliana.

    Science.gov (United States)

    Yang, Xinping; Pan, Haopeng; Wang, Peng; Zhao, Fang-Jie

    2017-01-15

    The use of manufactured cerium oxide nanoparticles (CeO2-NPs) in consumer products has increased markedly over the past decade, and their release into natural ecosystems is unavoidable. This study investigated the phytotoxicity and uptake of CeO2-NPs in Arabidopsis thaliana grown in an agar medium. Although low concentrations of CeO2-NPs had stimulatory effects on plant growth, at higher concentrations, CeO2-NPs reduced growth and had adverse effects on the antioxidant systems and photosystem. Importantly, the toxicity resulted from the nanoparticles per se, rather than from the dissolved Ce ions. CeO2-NPs were taken up and subsequently translocated to shoot tissues, and transmission electron microscopy (TEM) showed the presence of a large number of needle-like particle aggregations in the intercellular regions and the cytoplasm of leaf cells. The up-translocation factor to shoots was independent of the concentrations of Ce in the roots and the supplied forms of Ce (i.e. CeO2-NPs, CeO2-bulk, and ionic Ce), suggesting that endocytosis is likely to be a general mechanism responsible for the translocation of these Ce compounds. These findings provide important information regarding the toxicity and uptake of CeO2-NPs in plants, which needs to be considered in environmental risk assessment for the safe use and disposal of CeO2-NPs.

  3. Diesel/biodiesel soot oxidation with ceo2 and ceo2-zro2-modified cordierites: a facile way of accounting for their catalytic ability in fuel combustion processes

    Directory of Open Access Journals (Sweden)

    Rodrigo F. Silva

    2011-01-01

    Full Text Available CeO2 and mixed CeO2-ZrO2 nanopowders were synthesized and efficiently deposited onto cordierite substrates, with the evaluation of their morphologic and structural properties through XRD, SEM, and FTIR. The modified substrates were employed as outer heterogeneous catalysts for reducing the soot originated from the diesel and diesel/biodiesel blends incomplete combustion. Their activity was evaluated in a diesel stationary motor, and a comparative analysis of the soot emission was carried out through diffuse reflectance spectroscopy. The analyses have shown that the catalyst-impregnated cordierite samples are very efficient for soot oxidation, being capable of reducing the soot emission in more than 60%.

  4. Influence of CeO2 morphology on the catalytic activity of CeO2-Pt hybrids for CO oxidation.

    Science.gov (United States)

    Singhania, Nisha; Anumol, E A; Ravishankar, N; Madras, Giridhar

    2013-11-21

    Ceria, because of its excellent redox behavior and oxygen storage capacity, is used as a catalyst for several technologically important reactions. In the present study, different morphologies of nano-CeO2 (rods, cubes, octahedra) were synthesized using the hydrothermal route. An ultrafast microwave-assisted method was used to efficiently attach Pt particles to the CeO2 polyhedra. These nanohybrids were tested as catalysts for the CO oxidation reaction. The CeO2/Pt catalyst with nanorods as the support was found to be the most active catalyst. XPS and IR spectroscopy measurements were carried out in order to obtain a mechanistic understanding and it was observed that the adsorbed carbonates with lower stability on the reactive planes of nanorods and cubes are the major contributor to this enhanced catalytic activity.

  5. Formic Acid Modified Co3O4-CeO2 Catalysts for CO Oxidation

    Directory of Open Access Journals (Sweden)

    Ruishu Shang

    2016-03-01

    Full Text Available A formic acid modified catalyst, Co3O4-CeO2, was prepared via facile urea-hydrothermal method and applied in CO oxidation. The Co3O4-CeO2-0.5 catalyst, treated by formic acid at 0.5 mol/L, performed better in CO oxidation with T50 obtained at 69.5 °C and T100 obtained at 150 °C, respectively. The characterization results indicate that after treating with formic acid, there is a more porous structure within the Co3O4-CeO2 catalyst; meanwhile, despite of the slightly decreased content of Co, there are more adsorption sites exposed by acid treatment, as suggested by CO-TPD and H2-TPD, which explains the improvement of catalytic performance.

  6. Kinetics of thermal decomposition of CeO2 nanocrystalline precursor prepared by precipitation method

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The thermal decomposition of CeO2 nanocrystalline precursor prepared by chemical precipitation method was investigated using thermo-gravimetric/differential scanning calorimetry (TG/DSC) and X-ray powder diffraction (XRD).In particular,the differential thermal analysis curves for the decomposition of CeO2 nanocrystalline precursor were measured at different heating rates in air by a thermal analyzer (NETZSCH STA 449C,Germany).The kinetic parameters of the thermal decomposition of CeO2 nanocrystalline precursor were calculated using the Kissinger method and the Coats-Redfern method.Results show that the apparent active energy E of the reaction is 105.51 kJ/mol,the frequency factor lnA is 3.602 and the reaction order n is 2.This thermal decomposition process can be described by the anti-Jander equation and a threedimensional diffusion mechanism.

  7. A Dipole Polarizable Potential for Reduced and Doped CeO$_2$ from First-Principles

    CERN Document Server

    Burbano, Mario; Yildiz, Bilge; Tuller, Harry L; Norberg, Stefan T; Hull, Stephen; Madden, Paul A; Watson, Graeme W

    2011-01-01

    In this paper we present the parameterization of a new interionic potential for stoichiometric, reduced and doped CeO$_2$. We use a dipole-polarizable potential (DIPPIM) and optimize its parameters by fitting them to a series of DFT calculations. The resulting potential was tested by calculating a series of fundamental properties for CeO$_2$ and by comparing them to experimental values. The agreement for all the calculated properties (thermal and chemical expansion coefficients, lattice parameters, oxygen migration energies, local crystalline structure and elastic constants) is within 10-15% of the experimental one, an accuracy comparable to that of ab initio calculations. This result suggests the use of this new potential for reliably predicting atomic-scale properties of CeO$_2$ in problems where ab initio calculations are not feasible due to their size-limitations.

  8. Fabrication of CeO2 nanoparticle-modified silk for UV protection and antibacterial applications.

    Science.gov (United States)

    Lu, Zhisong; Mao, Cuiping; Meng, Mei; Liu, Sangui; Tian, Yunli; Yu, Ling; Sun, Bai; Li, Chang Ming

    2014-12-01

    To endow silk with UV-shielding ability and antibacterial activity, CeO2 nanoparticles were immobilized on silk surface via a dip-coating approach without changing silk structure. Surface density of the nanoparticles could be easily adjusted by controlling the number of dip-coating cycle. Enhanced thermal stability of the modified silk is exhibited in thermogravimetric analysis (TGA) and derivative thermogravimetric analysis (DTG). The excellent UV-protection ability and antibacterial property of the CeO2 nanoparticle-coated silk are demonstrated in UV-vis diffuse reflectance spectroscopy and colony-forming capability test, respectively. Based on the data, it can be concluded that CeO2 nanoparticles could be used as a very promising coating material to modify silk for UV-protection and antibacterial applications.

  9. Preparation and Characterization of Graphite Powder Covered with CeO2

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In order to improve the wetting properties of graphite with Al melt and reduce the oxidation of the graphite, by which the segregation of components during the liquid-stir-casting process could be prevented. In this paper, a uniform thin nano-film of CeO2, about 20 nm thick, was successfully prepared onto graphite powder surface by heterogeneous nucleation process. The results show that an obvious chemical reaction did exit between CeO2 film and graphite with the formation of Ce-O-C bond, leading to a shift of the binding energy of C and Ce. The cover with CeO2 film illustrates a distinct change of surface state of graphite with a decrease of angle of contact.

  10. A Comparison of GaN Epilayers with Multiple Buffer Layers and with a Single Buffer Layer Grown on Si(111) Studied by HRXRD and RBS/Channeling

    Institute of Scientific and Technical Information of China (English)

    DING Zhi-Bo; WANG Kun; YAO Shu-De

    2008-01-01

    @@ Two hexagonal GaN epilayers (samples A and B) with multiple buffer layers and single buffer layer are grown on Si (111) by metal-organic vapour phase epitaxy (MOVPE).From the results of Rutherford backscattering (RBS)/channeling and high resolution x-ray diffraction (HRXRD),we obtain the lattice constant (a and c) of two GaN epilayers (aA = 0.3190 nm,cA = 0.5184 nm and aB = 0.3192 nm,cB = 0.5179 nm),the crystal quality of two GaN epilayers ( XminA = 4.87%,XminB=7.35% along axis) and the tetragonal distortion eT of the two samples along depth (sample A is nearly fully relaxed,sample B is not relaxed enough).

  11. Resource allocation for two source-destination pairs sharing a single relay with a buffer

    KAUST Repository

    Zafar, Ammar

    2014-05-01

    In this paper, we obtain the optimal resource allocation scheme in order to maximize the achievable rate region in a dual-hop system that consists of two independent source-destination pairs sharing a single half-duplex relay. The relay decodes the received information and possesses buffers to enable storing the information temporarily before forwarding it to the respective destination. We consider both non-orthogonal transmission with successive interference cancellation at the receivers and orthogonal transmission. Also, we consider Gaussian block-fading channels and we assume that the channel state information is known and that no delay constraints are required. We show that, with the aid of buffering at the relay, joint user-and-hop scheduling is optimal and can enhance the achievable rate significantly. This is due to the joint exploitation of multiuser diversity and multihop diversity in the system. We provide closed-form expressions to characterize the average achievable rates in a generic form as functions of the statistical model of the channels. Furthermore, we consider sub-optimal schemes that exploit the diversity in the system partially and we provide numerical results to compare the different schemes and demonstrate the gains of the optimal one. © 2014 IEEE.

  12. First-principles characterization of formate and carboxyl adsorption on the stoichiometric CeO2(111) and CeO2(110) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Mei, Donghai

    2013-05-20

    Molecular adsorption of formate and carboxyl on the stoichiometric CeO2(111) and CeO2(110) surfaces was studied using periodic density functional theory (DFT+U) calculations. Two distinguishable adsorption modes (strong and weak) of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2(110) surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with experimental measurements. Finally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species are not affected by using different U parameters (U=0, 5, and 7). However, the calculated adsorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes (<0.2 eV). The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is negatively charge whiled the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased. This work was supported by the Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL) and by a Cooperative Research and Development Agreement (CRADA) with General Motors. The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC)

  13. RESONANT PHOTOEMISSION OF BULK CeO2 AND NANO-CeO2 FILMS

    Institute of Scientific and Technical Information of China (English)

    M.I. Abbas; K. Ibrahim; Z.Y. Wu; J. Zhang; F.Q. Liu; H.J. Qian

    2001-01-01

    Photoemission behaviors of nano-CeO2 films with particle sizes ranging from 8nm 1o50nm and bulk CeO2 in Ce 4d-4f absorption region have been investigated. Resonantenhancements of Ce 4f valance band and Ce 5p bands for nano film and bulk materialhave been observed. The variation of electron density of states in valance bands ofnano and bulk structures of CeO2 is discussed in terms of Ce 4d-4f resonance.

  14. Mixed cerium-platinum oxides: Electronic structure of [CeO]Ptn (n = 1, 2) and [CeO2]Pt complex anions and neutrals

    Science.gov (United States)

    Ray, Manisha; Kafader, Jared O.; Topolski, Josey E.; Jarrold, Caroline Chick

    2016-07-01

    The electronic structures of several small Ce-Pt oxide complexes were explored using a combination of anion photoelectron (PE) spectroscopy and density functional theory calculations. Pt and Pt2 both accept electron density from CeO diatomic molecules, in which the cerium atom is in a lower-than-bulk oxidation state (+2 versus bulk +4). Neutral [CeO]Pt and [CeO]Pt2 complexes are therefore ionic, with electronic structures described qualitatively as [CeO+2]Pt-2 and [CeO+]Pt2-, respectively. The associated anions are described qualitatively as [CeO+]Pt-2 and [CeO+]Pt2-2, respectively. In both neutrals and anions, the most stable molecular structures determined by calculations feature a distinct CeO moiety, with the positively charged Ce center pointing toward the electron rich Pt or Pt2 moiety. Spectral simulations based on calculated spectroscopic parameters are in fair agreement with the spectra, validating the computationally determined structures. In contrast, when Pt is coupled with CeO2, which has no Ce-localized electrons that can readily be donated to Pt, the anion is described as [CeO2]Pt-. The molecular structure predicted computationally suggests that it is governed by charge-dipole interactions. The neutral [CeO2]Pt complex lacks charge-dipole stabilizing interactions, and is predicted to be structurally very different from the anion, featuring a single Pt-O-Ce bridge bond. The PE spectra of several of the complexes exhibit evidence of photodissociation with Pt- daughter ion formation. The electronic structures of these complexes are related to local interactions in Pt-ceria catalyst-support systems.

  15. Ultrafast pump-probe spectroscopy studies of CeO2 thin film deposited on Ni-W substrate by RF magnetron sputtering

    Science.gov (United States)

    Singh, Preetam; Srivatsa, K. M. K.; Jewariya, Mukesh

    2016-08-01

    This study presents the first investigation of rapid dynamical processes that occur in pure CeO2 thin film, using ultra fast pump-probe spectroscopy at room temperature. For this purpose we have used a single (200) oriented CeO2 film deposited on biaxially textured Ni-W substrate by RF magnetron sputtering technique. The ultrafast transient spectra show initial sharp rise transition followed by an exponential photon decay. This rise time is about 10 ps irrespective of the probe wavelengths range 500-800 nm. The initial decay constant (τ) at 500 nm probe wavelength is found to be 171 ps, while at 800 nm probe wavelength it is 107.5 ps. The ultrafast absorption spectra show two absorption peaks at 745 and 800 nm, and are attributed to the electronic transitions from 2F7/2-2F5/2 and 1S0-1F3 respectively. The relatively high intensity absorption peak at 745 nm indicates dominant f-f electronic transition. Further, the absorption peak at 745 nm splits into two distinct peaks with respect to delay time, and is attributed to the charge transfer in between Ce4+ and Ce3+ ions. These results indicate that CeO2 itself is a potential candidate and can be used for optical applications.

  16. One-pot hydrothermal growth of raspberry-like CeO2 on CuO microsphere as copper-based catalyst for Rochow reaction

    Science.gov (United States)

    Jin, Zheying; Li, Jing; Shi, Laishun; Ji, Yongjun; Zhong, Ziyi; Su, Fabing

    2015-12-01

    In this work, we prepared a novel structure comprising of raspberry-like CeO2 deposited on CuO microspheres (Ce-CuO) for Rochow reaction. The synthesis was carried out via a facile one-pot hydrothermal reaction without using any template, in which, the basic copper carbonate microspheres were first formed via self-assembly of basic copper carbonate nanorods, followed with deposition of cerium hydroxide. After calcination, they were transformed into Ce-CuO but still maintained the hierarchical structure, and meanwhile, mesoporous structure was formed (for simplicity, we will only state them as metal oxide in the following context). The samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) techniques. When used as a Cu-based catalyst, Ce-CuO exhibited superior catalytic property to the single CuO, CeO2 and their physically mixture in the Rochow reaction with dimethyldichlorosilane (M2) selectivity increased from ca. 65 to 83.7%. The higher M2 selectivity of Ce-CuO is mainly due to its larger surface area and the synergistic effect between CuO and CeO2. This work demonstrates that catalytic performance of the Cu-based can be improved by adding Ce rare-earth element and by carefully controlling their structures.

  17. Preferential Oxidation of Carbon Monoxide in Excess Hydrogen over Au/Co3O4- CeO2 Catalysts

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Au/Co3O4-CeO2 mixed-oxide catalysts were shown experimentally to be highly active and selective for the oxidation of CO in hydrogen-rich mixture. Activity was markedly influenced by the composition of the support, aging temperature and Au-loading temperature. It provided that single-step removal of CO from hydrogen-rich stream both in the absence and presence of CO2 and H2O to a PEMFC tolerant level. It was found that catalytic activity is greatly affected by adding CO2 in the mixture and increased by farther adding H2O. It meants H2O has the effect to rise catalytic activity. Moreover,it shows better stability with reaction time for the preferential CO oxidation.

  18. Effect of the laser sputtering parameters on the orientation of a cerium oxide buffer layer on sapphire and the properties of a YBa2Cu3Ox superconducting film

    DEFF Research Database (Denmark)

    Mozhaev, P. B.; Ovsyannikov, G. A.; Skov, Johannes

    1999-01-01

    The effect of the laser sputtering parameters on the crystal properties of CeO2 buffer layers grown on a (1 (1) under bar 02) sapphire substrate and on the properties of superconducting YBa2Cu3Ox thin films are investigated. It is shown that (100) and (111) CeO2 growth is observed, depending...

  19. Enhanced Colloidal Stability of CeO2 Nanoparticles by Ferrous Ions: Adsorption, Redox Reaction, and Surface Precipitation.

    Science.gov (United States)

    Liu, Xuyang; Ray, Jessica R; Neil, Chelsea W; Li, Qingyun; Jun, Young-Shin

    2015-05-05

    Due to the toxicity of cerium oxide (CeO2) nanoparticles (NPs), a better understanding of the redox reaction-induced surface property changes of CeO2 NPs and their transport in natural and engineered aqueous systems is needed. This study investigates the impact of redox reactions with ferrous ions (Fe2+) on the colloidal stability of CeO2 NPs. We demonstrated that under anaerobic conditions, suspended CeO2 NPs in a 3 mM FeCl2 solution at pH 4.8 were much more stable against sedimentation than those in the absence of Fe2+. Redox reactions between CeO2 NPs and Fe2+ lead to the formation of 6-line ferrihydrite on the CeO2 surfaces, which enhanced the colloidal stability by increasing the zeta potential and hydrophilicity of CeO2 NPs. These redox reactions can affect the toxicity of CeO2 NPs by increasing cerium dissolution, and by creating new Fe(III) (hydr)oxide reactive surface layers. Thus, these findings have significant implications for elucidating the phase transformation and transport of redox reactive NPs in the environment.

  20. An Evaluation of the Potential Phototoxicity of CeO2 Nanoparticles in Retinal Pigment Epithelial Cells in-vitro

    Science.gov (United States)

    Cerium dioxide (CeO2) engineered nanoparticles (NP) are used as fuel-borne catalysts in off-road diesel engines, which can lead to exhaust emissions of respirable CeO2 NP. Other metal oxides may act as photo-catalysts which induce the generation of free radicals upon exposure to ...

  1. Intense up-conversion luminescence in Er3+/Yb3+ co-doped CeO2 powders.

    Science.gov (United States)

    Singh, Vijay; Rathaiah, M; Venkatramu, V; Haase, Markus; Kim, S H

    2014-03-25

    The Er(3+) and Er(3+)/Yb(3+) co-doped CeO2 powders have been prepared by a urea combustion route. The structural, morphological, compositional and vibrational analysis of the Er(3+):CeO2 and Er(3+)/Yb(3+):CeO2 powders have been studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and Fourier transform infrared spectroscopy. The optical and luminescence properties of Er(3+):CeO2 and Er(3+)/Yb(3+):CeO2 powders have been studied by using laser excited spectroscopy. The effects of Yb(3+) doping on up-conversion luminescence of Er(3+) co-doped CeO2 powders were studied. The ratio of red to green intensity is decreased in Er(3+):CeO2 whereas the ratio is increased in Er(3+)/Yb(3+):CeO2 powders with increase of power. The effect of co-doping with the Yb(3+) ions on the visible luminescence of Er(3+) and the energy transfer mechanism responsible for the variation in the green and red intensity are discussed. The results indicate that these materials may be suitable for display and light emitting devices.

  2. Facile fabrication of CeO2 hollowmicrospheres with yeast as bio-templates

    Institute of Scientific and Technical Information of China (English)

    牟广宇; 魏清莲; 黄永民

    2015-01-01

    CeO2 hollow microspheres were prepared through a facile method by using yeast cells as bio-templates. The yeast pro-vided a solid frame for the deposition of cerium hydroxide to form the hybrid Ce(OH)3@yeast precursor. The resulting CeO2 hollow microspheres were obtained by calcining the precursor. The products were characterized by field emission scanning electron micros-copy (FE-SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), fourier transform infrared spectroscopy (FTIR), N2 adsorption/desorption analysis, X-ray photoelectron spectrum (XPS) and H2 temperature programmed reduction (H2-TPR). It was found that the products fully retained the morphology of the yeast cells and the size of the hollow microspheres was about 1.5–2μm. The catalytic test results showed that the as-obtained hollow CeO2 microspheres possessed a higher catalytic activity in CO oxidation than the commercial CeO2, which attributed to their higher surface area, hollow structure and superior reducibility. This study provided a promising route for the preparation of a variety of other inorganic hollow microspheres.

  3. Anomalous compressive behavior in CeO2 nanocubes under high pressure

    DEFF Research Database (Denmark)

    Ge, M. Y.; Fang, Y. Z.; Wang, H.;

    2008-01-01

    High-pressure angle-dispersive x-ray diffraction measurements have been performed on bulk and nanocrystalline cubic CeO2 with mean sizes of 4.7 and 5.6 nm. It is found that the compressibility of the nanocrystals is lower than the bulk when a threshold pressure is reached. This critical pressure ...

  4. Fundamentals and Catalytic Applications of CeO2-Based Materials.

    Science.gov (United States)

    Montini, Tiziano; Melchionna, Michele; Monai, Matteo; Fornasiero, Paolo

    2016-05-25

    Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40(th) anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are deepening our understanding of these materials, helping us to predict their behavior and application potential. This review has a wide view on all those aspects related to ceria which promise to produce an important impact on our life, encompassing fundamental knowledge of CeO2 and its properties, characterization toolbox, emerging features, theoretical studies, and all the catalytic applications, organized by their degree of establishment on the market.

  5. Aqueous and Surface Chemistries of Photocatalytic Fe-Doped CeO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Duangdao Channei

    2017-01-01

    Full Text Available The present work describes the effects of water on Fe-doped nanoparticulate CeO2, produced by flame spray pyrolysis, which is a critical environmental issue because CeO2 is not stable in typical atmospheric conditions. It is hygroscopic and absorbs ~29 wt % water in the bulk when exposed to water vapor but, more importantly, it forms a hydrated and passivating surface layer when immersed in liquid water. In the latter case, CeO2 initially undergoes direct and/or reductive dissolution, followed by the establishment of a passivating layer calculated to consist of ~69 mol % solid CeO2·2H2O and ~30 mol % gelled Ce(OH4. Under static flow conditions, a saturated boundary layer also forms but, under turbulent flow conditions, this is removed. While the passivating hydrated surface layer, which is coherent probably owing to the continuous Ce(OH4 gel, would be expected to eliminate the photoactivity, this does not occur. This apparent anomaly is explained by the calculation of (a the thermodynamic stability diagrams for Ce and Fe; (b the speciation diagrams for the Ce4+-H2O, Ce3+-H2O, Fe3+-H2O, and Fe2+-H2O systems; and (c the Pourbaix diagrams for the Ce-H2O and Fe-H2O systems. Furthermore, consideration of the probable effects of the localized chemical and redox equilibria owing to the establishment of a very low pH (<0 at the liquid-solid interface also is important to the interpretation of the phenomena. These factors highlight the critical importance of the establishment of the passivating surface layer and its role in photocatalysis. A model for the mechanism of photocatalysis by the CeO2 component of the hydrated phase CeO2·2H2O is proposed, explaining the observation of the retention of photocatalysis following the apparent alteration of the surface of CeO2 upon hydration. The model involves the generation of charge carriers at the outer surface of the hydrated surface layer, followed by the formation of radicals, which decompose organic species that have diffused through the boundary layer, if present.

  6. On the mechanism of nanoparticulate CeO2 toxicity to freshwater algae.

    Science.gov (United States)

    Angel, Brad M; Vallotton, Pascal; Apte, Simon C

    2015-11-01

    The factors affecting the chronic (72-h) toxicity of three nanoparticulate (10-34nm) and one micron-sized form of CeO2 to the green alga, Pseudokirchneriella subcapitata were investigated. To characterise transformations in solution, hydrodynamic diameters (HDD) were measured by dynamic light scatter, zeta potential values by electrophoretic mobility, and dissolution by equilibrium dialysis. The protective effects of humic and fulvic dissolved organic carbon (DOC) on toxicity were also assessed. To investigate the mechanisms of algal toxicity, the CytoViva hyperspectral imaging system was used to visualise algal-CeO2 interactions in the presence and absence of DOC, and the role of reactive oxygen species (ROS) was investigated by 'switching off' ROS production using UV-filtered lighting conditions. The nanoparticulate CeO2 immediately aggregated in solution to HDDs measured in the range 113-193nm, whereas the HDD and zeta potential values were significantly lower in the presence of DOC. Negligible CeO2 dissolution over the time course of the bioassay ruled out potential toxicity from dissolved cerium. The nanoparticulate CeO2 concentration that caused 50% inhibition of algal growth rate (IC50) was in the range 7.6-28mg/L compared with 59mg/L for micron-sized ceria, indicating that smaller particles were more toxic. The presence of DOC mitigated toxicity, with IC50s increasing to greater than 100mg/L. Significant ROS were generated in the nanoparticulate CeO2 bioassays under normal light conditions. However, 'switching off' ROS under UV-filtered light conditions resulted in a similar IC50, indicating that ROS generation was not the toxic mechanism. The CytoViva imaging showed negligible sorption of nanoparticulate CeO2 to algal cells in the presence of DOC, and strong sorption in its absence, suggesting that this was the toxic mechanism. The results suggest that DOC in natural waters will coat CeO2 particles and mitigate toxicity to algal cells.

  7. Spray deposited CeO2–TiO2 counter electrode for electrochromic devices

    Indian Academy of Sciences (India)

    A K Bhosale; S R Kulal; V M Gurame; P S Patil

    2015-04-01

    Optically passive thin films of CeO2–TiO2 mixed oxides with molar ratio of Ce/Ti of 0.05 were deposited by the spray pyrolysis technique (SPT) on a glass and fluorine-doped tin oxide (FTO)-coated glass substrates. Precursor solution containing cerium nitrate hexahydrate (Ce(NO3)2·6H2O) and titanium tetraiso-propoxide (Ti(OiPr)4) having different volumetric proportions (0–5 vol% of Ti) in methanol were used. These films were characterized for structural, morphological, molecular, optical, electrochromic and colourimetric analysis. CeO2–TiO2 films deposited at 400° C were found to be polycrystalline with cubic fluorite crystal structure. Transformation from polycrystalline to amorphous phase was observed with increasing TiO2 content. The band centred at 539 cm−1 is assigned to Ce–O stretching vibration and the two medium intensity bands assigned to (Ti–O) and (Ti–O–Ti) stretching modes at 798 and 451 cm−1, which confirms the mixed CeO2 and TiO2 phases. The band gap energy decreases (g) from 3.45 eV for pristine CeO2 to 2.98–3.09 eV for CeO2–TiO2 films. The ion storage capacity (ISC) of CeO2–TiO2 thin film with 3 vol% Ti (Ce–Ti3 sample) was found to be 26 mC cm−2 and electrochemical stability up to 30,000 cycles in 0.5 M LiClO4-PC electrolyte. The optically passive behaviour of CeO2–TiO2 thin film is confirmed by its negligible transmission modulation ( ∼ 2.5%) upon Li+ ion insertion/extraction, irrespective of the extent of Li+ ion intercalation. The optical modulation of sputter deposited electrochromic WO3 thin film was found to be enhanced from 56 to 61% with rapid increase in colouration efficiency (CE) from 42 to 231 cm2 C−1 when CeO2–TiO2 is coupled as a counter electrode with WO3 in an electrochromic device (ECD). On reduction of WO3 thin film with CeO2–TiO2 as counter electrode, the CIELAB 1931 2° colour space coordinates show the transition from colourless to the deep blue state (* = 88.07, * = −2.37, * = 24.59 and * = 40.32, * = −1.16, * = −5.65) with steady decrease in relative lightness. Yxy and *** coordinates signify CeO2–TiO2 films and it also exhibits the application as counter electrode in electrochromic smart windows in which they are able to retain their transparency under charge insertion/extraction.

  8. Growth-Rate Induced Epitaxial Orientation of CeO2 on Al2O3(0001)

    Energy Technology Data Exchange (ETDEWEB)

    Kuchibhatla, Satyanarayana V N T; Nachimuthu, Ponnusamy; Gao, Fei; Jiang, Weilin; Shutthanandan, V.; Engelhard, Mark H.; Seal, Sudipta; Thevuthasan, Suntharampillai

    2009-05-19

    High-quality ceria (CeO2) films were grown on sapphire (Al2O3) (0001) substrates using oxygen plasma-assisted molecular beam epitaxy. The epitaxial orientation of the ceria films has been found to be (100) and (111) at low (< 8 Å/min) and higher growth rates (up to ~30 Å/min), respectively. Evidence shows that CeO2 (100) film grows as three-dimensional islands, while CeO2 (111) proceeds with layered growth. Three in-plane domains at 30° to each other are observed in the CeO2 (100), which is attributed to the close match of the oxygen sub-lattices in the film and substrate that has a three-fold symmetry. Molecular dynamic simulations have further confirmed that the CeO2 film retains (100) orientation on the Al2O3 (0001) substrate.

  9. Synthesis, characterization, and ecotoxicity of CeO2 nanoparticles with differing properties

    Science.gov (United States)

    Alam, Bushra; Philippe, Allan; Rosenfeldt, Ricki R.; Seitz, Frank; Dey, Sonal; Bundschuh, Mirco; Schaumann, Gabriele E.; Brenner, Sara A.

    2016-10-01

    CeO2 nanoparticles with various characteristics find an increasing number of applications in the electronic, medical, and other industries and are therefore likely released in the environment. This calls for investigations linking the physicochemical properties of these particles with their potential environmental impacts. In this study, CeO2 nanoparticle powders were prepared using three different precursors [Ce(NO3)3, CeCl3, and Ce(CH3COO)3] and annealing temperatures (300, 500, and 700 °C). This procedure resulted in nine different types of nanoparticles with differing size (5-90 nm), morphology, surface Ce3+/Ce4+ ratio, and slightly different crystal structures as characterized using transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, and X-ray diffraction measurements with Rietveld refinement. These CeO2 nanoparticles underwent toxicity testing at concentrations up to 64 mg L-1 using Daphnia magna. Toxic effects were observed for three particle types with EC50 values between 5 and 64 mg L-1. No clear correlation was observed between the physicochemical properties (size, shape, oxygen occupancy, Ce3+/Ce4+ ratio) of the nanoparticles and their toxicity. However, toxicity was correlated with the amount of Ce remaining suspended in the test medium after 24 h. This indicated that toxic effects may depend on the colloidal stability of CeO2 nanoparticles during the first day of exposure. Therefore, being readily suspended and remaining stable for several days in the aquatic media increases the likelihood that CeO2 nanoparticles will cause unwanted adverse effects.

  10. Superconducting NbN single-photon detectors on GaAs with an AlN buffer layer

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Ekkehart; Merker, Michael; Ilin, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme (IMS), Karlsruher Institut fuer Technologie, Hertzstrasse 16, 76187 Karlsruhe (Germany)

    2015-07-01

    GaAs is the material of choice for photonic integrated circuits. It allows the monolithic integration of single-photon sources like quantum dots, waveguide based optical circuits and detectors like superconducting nanowire single-photon detectors (SNSPDs) onto one chip. The growth of high quality NbN films on GaAs is challenging, due to natural occurring surface oxides and the large lattice mismatch of about 27%. In this work, we try to overcome these problems by the introduction of a 10 nm AlN buffer layer. Due to the buffer layer, the critical temperature of 6 nm thick NbN films was increased by about 1.5 K. Furthermore, the critical current density at 4.2 K of NbN flim deposited onto GaAs with AlN buffer is 50% higher than of NbN film deposited directly onto GaAs substrate. We successfully fabricated NbN SNSPDs on GaAs with a AlN buffer layer. SNSPDs were patterned using electron-beam lithography and reactive-ion etching techniques. Results on the study of detection efficiency and jitter of a NbN SNSPD on GaAs, with and without AlN buffer layer will be presented and discussed.

  11. Microwave synthesis of pure and doped cerium (IV) oxide (CeO2) nanoparticles for methylene blue degradation.

    Science.gov (United States)

    El Rouby, W M A; Farghali, A A; Hamdedein, A

    2016-11-01

    Cerium (IV) oxide (CeO2), samarium (Sm) and gadolinium (Gd) doped CeO2 nanoparticles were prepared using microwave technique. The effect of microwave irradiation time, microwave power and pH of the starting solution on the structure and crystallite size were investigated. The prepared nanoparticles were characterized using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscope. The photocatalytic activity of the as-prepared CeO2, Sm and Gd doped CeO2 toward degradation of methylene blue (MB) dye was investigated under UV light irradiation. The effect of pH, the amount of catalyst and the dye concentration on the degradation extent were studied. The photocatalytic activity of CeO2 was kinetically enhanced by trivalent cation (Gd and Sm) doping. The results revealed that Gd doped CeO2 nanoparticles exhibit the best catalytic degradation activity on MB under UV irradiation. For clarifying the environmental safety of the by products produced from the degradation process, the pathways of MB degradation were followed using liquid chromatography/mass spectroscopy (LC/MS). The total organic carbon content measurements confirmed the results obtained by LC/MS. Compared to the same nanoparticles prepared by another method, it was found that Gd doped CeO2 prepared by hydrothermal process was able to mineralize MB dye completely under UV light irradiation.

  12. Effects and implications of trophic transfer and accumulation of CeO2 nanoparticles in a marine mussel.

    Science.gov (United States)

    Conway, Jon R; Hanna, Shannon K; Lenihan, Hunter S; Keller, Arturo A

    2014-01-01

    Bivalves are hypothesized to be key organisms in the fate and transport of engineered nanomaterials (ENMs) in aquatic environments due to their ability to filter and concentrate particles from water, but how different exposure pathways influence their interactions with ENMs is not well understood. In a five-week experiment, we tested how interactions between CeO2 ENMs and a marine mussel, Mytilus galloprovincialis, are affected through two exposure methods, direct and through sorption to phytoplankton. We found that phytoplankton sorbed ENMs in CeO2 was captured and excreted in pseudofeces and average pseudofeces mass doubled in response to CeO2 exposure. Final mean dry tissue Ce concentration (±SE) for treatments exposed to 3 mg L(-1) CeO2 directly was 33 ± 9 μg g(-1) Ce, and 0 ± 0, 19 ± 4, 21 ± 3, and 28 ± 5 μg g(-1) for treatments exposed to 0, 1, 2, and 3 mg L(-1) CeO2 sorbed to phytoplankton. Clearance rates increased with CeO2 concentration but decreased over time in groups exposed to CeO2 directly, indicating stress. These results show the feedback between ENM toxicity and transport and the likelihood of biological mediation in the fate and transport of ENMs in aquatic environments.

  13. Synthesis of novel CeO2-BiVO4/FAC composites with enhanced visible-light photocatalytic properties.

    Science.gov (United States)

    Zhang, Jin; Wang, Bing; Li, Chuang; Cui, Hao; Zhai, Jianping; Li, Qin

    2014-09-01

    To utilize visible light more effectively in photocatalytic reactions, a fly ash cenosphere (FAC)-supported CeO2-BiVO4 (CeO2-BiVO4/FAC) composite photocatalyst was prepared by modified metalorganic decomposition and impregnation methods. The physical and photophysical properties of the composite have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and UV-Visible diffuse reflectance spectra. The XRD patterns exhibited characteristic diffraction peaks of both BiVO4 and CeO2 crystalline phases. The XPS results showed that Ce was present as both Ce(4+) and Ce(3+) oxidation states in CeO2 and dispersed on the surface of BiVO4 to constitute a p-n heterojunction composite. The absorption threshold of the CeO2-BiVO4/FAC composite shifted to a longer wavelength in the UV-Vis absorption spectrum compared to the pure CeO2 and pure BiVO4. The composites exhibited enhanced photocatalytic activity for Methylene Blue (MB) degradation under visible light irradiation. It was found that the 7.5wt.% CeO2-BiVO4/FAC composite showed the highest photocatalytic activity for MB dye wastewater treatment.

  14. Effects of CeO2 nanoparticles on system performance and bacterial community dynamics in a sequencing batch reactor.

    Science.gov (United States)

    Qiu, Guanglei; Neo, Sin-Yi; Ting, Yen-Peng

    2016-01-01

    The effects of CeO2 nanoparticles (NPs) on the system performance and the bacterial community dynamics in a sequencing batch reactor (SBR) were investigated, along with the fate and removal of CeO2 NPs within the SBR. Significant impact was observed on nitrification; NH4+-N removal efficiency decreased from almost 100% to around 70% after 6 days of continuous exposure to 1.0 mg/L of CeO2 NPs, followed by a gradual recovery until a stable value of around 90% after 20 days. Additionally, CeO2 NPs also led to a significant increase in the protein content in the soluble microbial products, showing the disruptive effects of CeO2 NPs on the extracellular polymeric substance matrix and related activated sludge structure. Denaturing gradient gel electrophoresis analysis showed remarkable changes in the bacterial community structure in the activated sludge after exposure to CeO2 NPs. CeO2 NPs were effectively removed in the SBR mainly via sorption onto the sludge. However, the removal efficiency decreased from 95 to 80% over 30 days. Mass balance evaluation showed that up to 50% of the NPs were accumulated within the activated sludge and were removed with the waste sludge.

  15. Morphology-dependent interplay of reduction behaviors, oxygen vacancies and hydroxyl reactivity of CeO2 nanocrystals.

    Science.gov (United States)

    Gao, Yuxian; Li, Rongtan; Chen, Shilong; Luo, Liangfeng; Cao, Tian; Huang, Weixin

    2015-12-21

    Reduction behaviors, oxygen vacancies and hydroxyl groups play decisive roles in the surface chemistry and catalysis of oxides. Employing isothermal H2 reduction we simultaneously reduced CeO2 nanocrystals with different morphologies, created oxygen vacancies and produced hydroxyl groups. The morphology of CeO2 nanocrystals was observed to strongly affect the reduction process and the resultant oxygen vacancy structure. The resultant oxygen vacancies are mainly located on the surfaces of CeO2 cubes and rods but in the subsurface/bulk of CeO2 octahedra. The reactivity of isolated bridging hydroxyl groups on CeO2 nanocrystals was found to depend on the local oxygen vacancy concentration, in which they reacted to produce water at low local oxygen vacancy concentrations but to produce both water and hydrogen with increasing local oxygen vacancy concentration. These results reveal a morphology-dependent interplay among the reduction behaviors, oxygen vacancies and hydroxyl reactivity of CeO2 nanocrystals, which deepens the fundamental understanding of the surface chemistry and catalysis of CeO2.

  16. Kinetics Study of Photocatalytic Activity of Flame-Made Unloaded and Fe-Loaded CeO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    D. Channei

    2013-01-01

    Full Text Available Unloaded CeO2 and nominal 0.50, 1.00, 1.50, 2.00, 5.00, and 10.00 mol% Fe-loaded CeO2 nanoparticles were synthesized by flame spray pyrolysis (FSP. The samples were characterized to obtain structure-activity relation by X-ray diffraction (XRD, high-resolution transmission electron microscopy (HRTEM, Brunauer, Emmett, and Teller (BET nitrogen adsorption, X-ray photoelectron spectroscopy (XPS, and UV-visible diffuse reflectance spectrophotometry (UV-vis DRS. XRD results indicated that phase structures of Fe-loaded CeO2 nanoparticles were the mixture of CeO2 and Fe2O3 phases at high iron loading concentrations. HRTEM images showed the significant change in morphology from cubic to almost-spherical shape observed at high iron loading concentration. Increased specific surface area with increasing iron content was also observed. The results from UV-visible reflectance spectra clearly showed the shift of absorption edge towards longer visible region upon loading CeO2 with iron. Photocatalytic studies showed that Fe-loaded CeO2 sample exhibited higher activity than unloaded CeO2, with optimal 2.00 mol% of iron loading concentration being the most active catalyst. Results from XPS analysis suggested that iron in the Fe3+ state might be an active species responsible for enhanced photocatalytic activities observed in this study.

  17. Electrochemical behavior and polishing properties of silicon wafer in alkaline slurry with abrasive CeO2

    Institute of Scientific and Technical Information of China (English)

    SONG Xiao-lan; XU Da-yu; ZHANG Xiao-wei; SHI Xun-da; JIANG Nan; QIU Guan-zhou

    2008-01-01

    The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated. The variations of corrosion potential (φcorr) and corrosion current density (Jcorr) of the P-type (100) silicon wafer with the slurry pH value and the concentration of abrasive CeO2 were studied by polarization curve technologies. The dependence of the polishing rate on the pH and the concentration of CeO2 in slurries during chemical mechanical polishing(CMP) were also studied. It is discovered that there is a large change of φcorr and Jcorr when slurry pH is altered and the Jcorr reaches the maximum (1.306 μA/cm2) at pH 10.5 when the material removal rate(MRR) comes to the fastest value. The Jcorr increases gradually from 0.994 μA/cm2 with 1% CeO2 to 1.304 μA/cm2 with 3% CeO2 and reaches a plateau with the further increase of CeO2 concentration. There is a considerable MRR in the slurry with 3% CeO2 at pH 10.5. The coherence between Jcorr and MRR elucidates that the research on the electrochemical behavior of silicon wafers in the alkaline slurry could offer theoretic guidance on silicon polishing rate and ensure to adjust optimal components of slurry.

  18. Electrochemical and optical properties of CeO2-SnO2 and CeO2-SnO2:X (X = Li, C, Si films

    Directory of Open Access Journals (Sweden)

    Berton Marcos A.C.

    2001-01-01

    Full Text Available Thin solid films of CeO2-SnO2 (17 mol% Sn and CeO2-SnO2:X (X = Li, C and Si were prepared by the sol-gel route, using an aqueous-based process. The addition of Li, C and Si to the precursor solution leads to films with different electrochemical performances. The films were deposited by the dip-coating technique on ITO coated glass (Donnelly Glass at a speed of 10 cm/min and submitted to a final thermal treatment at 450 °C during 10 min in air. The electrochemical and optical properties of the films were determined from the cyclic voltammetry and chronoamperometry measurements using 0.1 M LiOH as supporting electrolyte. The ion storage capacity of the films was investigated using in situ spectroelectrochemical method and during the insertion/extraction process the films remained transparent. The powders were characterized by thermal analysis (DSC/TGA and X-ray diffraction.

  19. Electrical and structural characterization of PLD grown CeO2–HfO2 laminated high-k gate dielectrics

    NARCIS (Netherlands)

    Karakaya, K.; Barcones, B.; Rittersma, Z.M.; Berkum, van J.G.M.; Verheijen, M.A.; Rijnders, G.; Blank, D.H.A.

    2006-01-01

    The electrical and physical properties of CeO2–HfO2 nanolaminates deposited by pulsed laser deposition (PLD) are investigated. The properties of the nanolaminates are compared with binary CeO2 and HfO2 thin films. Layers were deposited using CeO2 and HfO2 targets at substrate temperatures between 22

  20. Development and application of a green-chemistry solution deposition technique for buffer layer coating on cube-textured metal substrates in view of further deposition of rare-earth based superconductors

    DEFF Research Database (Denmark)

    Pallewatta, Pallewatta G A P

    , allowing the epitaxial growth of the superconducting layer. State-of-the-art coated conductor hetero structures are mainly based on CeO2 based buffer stacks that consist of a sequence of several different buffer layers. Buffer layers deposited by continuous chemical deposition techniques, which...... and hazardous chemicals such as 2-methoxyethanol, and trifluroacetic acid (TFA). Therefore, in our research the main focus was on the development of SrTiO3 single buffer layers based on environmentally safe chemicals, to reach the engineering requirements for continuous coating of long substrate tapes. A new......Superconductor based energy production has been thoroughly researched by many scientists all over the world, due to the advantage of zero electric resistance that will contribute to the energy saving capabilities. Recently successful developments have been reported in coated conductor architectures...

  1. Role of microstructure and surface defects on the dissolution kinetics of CeO2, a UO2 fuel analogue.

    OpenAIRE

    Corkhill, C.L; Bailey, D. J.; Tocino, F.Y.; Stennett, M.C.; Miller, J. A.; Provis, J.P.; Travis, K.P.; Hyatt, N.C.

    2016-01-01

    The release of radionuclides from spent fuel in a geological disposal facility is controlled by the surface mediated dissolution of UO2 in groundwater. In this study we investigate the influence of reactive surface sites on the dissolution of a synthesised CeO2 analogue for UO2 fuel. Dissolution was performed on: CeO2 annealed at high temperature, which eliminated intrinsic surface defects (point defects and dislocations); CeO2-x annealed in inert and reducing atmospheres to induce oxygen vac...

  2. Development of La3+ Doped CeO2 Thick Film Humidity Sensors

    Directory of Open Access Journals (Sweden)

    Chunjie Wang

    2014-01-01

    Full Text Available The humidity sensitive characteristics of the sensor fabricated from 10 mol% La2O3 doped CeO2 nanopowders with particle size 17.26 nm synthesized via hydrothermal method were investigated at different frequencies. It was found that the sensor shows high humidity sensitivity, rapid response-recovery characteristics, and narrow hysteresis loop at 100 Hz in the relative humidity range from 11% to 95%. The impedance of the sensor decreases by about five orders of magnitude as relative humidity increases. The maximum humidity hysteresis is about 6% RH, and the response and recovery time is 12 and 13 s, respectively. These results indicate that the nanosized La2O3 doped CeO2 powder has potential application as high-performance humidity sensor.

  3. Stable Electron Field Emission from CeO2 Nanowires by Hydrothermal Method

    Institute of Scientific and Technical Information of China (English)

    FU Xing-Qiu; FENG Ping; WANG Chong; WANG Tai-Hong

    2007-01-01

    @@ CeO2 nanowires are successful synthesized by hydrothermal method and their field emission (FE) properties are investigated. The turn-on electric field is 5.8 V/μm at an emitter-anode spacing of 700μm. The FE current is stable and the current fluctuations are less than 3% over 5 h. All the plotted Fowler-Nordheim curves yield straight lines, which are in agreement with the Fowler-Nordheim theory. The relationship between the field enhancement factorβ and the emitter-anode spacing d follows a universal equation. Our results imply that the CeO2 nanowires are promising materials for fabricating FE cathodes.

  4. Preparation, characterisation and dissolution of a CeO2 analogue for UO2 nuclear fuel

    Science.gov (United States)

    Stennett, Martin C.; Corkhill, Claire L.; Marshall, Luke A.; Hyatt, Neil C.

    2013-01-01

    The behaviour of spent nuclear fuel under geological conditions is a major issue underpinning the safety case for final disposal. This work describes the preparation and characterisation of a non-radioactive UO2 fuel analogue, CeO2, to be used to investigate nuclear fuel dissolution under realistic repository conditions as part of a developing EU research programme. The densification behaviour of several cerium dioxide powders, derived from cerium oxalate, were investigated to aid the selection of a suitable powder for fabrication of fuel analogues for powder dissolution tests. CeO2 powders prepared by calcination of cerium oxalate at 800 °C and sintering at 1700 °C gave samples with similar microstructure to UO2 fuel and SIMFUEL. The suitability of the optimised synthesis route for dissolution was tested in a dissolution experiment conducted at 90 °C in 0.01 M HNO3.

  5. Characterization of silicon-YBCO buffered multilayers grown by sputtering

    Science.gov (United States)

    Chiodoni, A.; Ballarini, V.; Botta, D.; Camerlingo, C.; Fabbri, F.; Ferrari, S.; Gerbaldo, R.; Ghigo, G.; Gozzelino, L.; Laviano, F.; Minetti, B.; Pirri, C. F.; Tallarida, G.; Tresso, E.; Mezzetti, E.

    2004-11-01

    In recent years, the scientific community has considered with interest the possibility to integrate YBCO-based devices with silicon-based electronics. In fact, the proved YBCO radiation hardness makes this integration appealing from the point of view of space and telecommunication applications. In this paper we report on the influence of buffered substrate properties on the superconducting performances of YBCO films. In this framework we here consider the Si/CeO2/YBCO multilayer. The non-satisfying quality of the YBCO film in this multilayer is attributed to an unavoidable interlayer of SiO2 between Si and CeO2. On the other hand, we prove, by means of quantitative magneto-optical analysis, the excellent properties of the bi-layer CeO2/YBCO on YSZ substrate. Thus, these measurements indicate YSZ as the best candidate to be deposited between Si and CeO2 for optimal YBCO performances on silicon.

  6. Physical Properties of Mixed Conductor Solid Oxide Fuel Cell Anodes of Doped CeO2

    DEFF Research Database (Denmark)

    Mogensen, Mogens Bjerg; Lindegaard, Thomas; Hansen, Uffe Rud

    1994-01-01

    Samples of CeO2 doped with oxides such as CaO and Gd2O3 were prepared. Their conductivities and expansions onreduction were measured at 1000°C, and the thermal expansion coefficients in the range 50 to 1000°C were determined. Theionic and electronic conductivity were derived from curves of total...... for solid oxide fuel cell anodes. Not all requirements are fulfilled. Measures to compensate for this arediscussed....

  7. RESONANT PHOTOEMISSION OF BULK CeO2 AND NANO—CeO2 FILMS

    Institute of Scientific and Technical Information of China (English)

    M.I.Abbas; K.Ibrahim; Z.Y.Wu; J.Zhang; F.Q.Liu; H.J.Qian

    2001-01-01

    Photoemission behaviors of nano-CeO2 films with parlicle sizes ranging from 8nm to 50nm and bulk CeO2 in Ce 4d-4f absorption region have been investigated.Resonant enhancements of Ce 4f valance band and Ce 5p bands for nano film and bulk material have been observed.The variation of electron density of Ce 4d-4f resonace.

  8. MnO2/CeO2 for catalytic ultrasonic degradation of methyl orange.

    Science.gov (United States)

    Zhao, He; Zhang, Guangming; Zhang, Quanling

    2014-05-01

    Catalytic ultrasonic degradation of aqueous methyl orange was studied in this paper. Heterogeneous catalyst MnO2/CeO2 was prepared by impregnation of manganese oxide on cerium oxide. Morphology and specific surface area of MnO2/CeO2 catalyst were characterized and its composition was determined. Results showed big differences between fresh and used catalyst. The removal efficiency of methyl orange by MnO2/CeO2 catalytic ultrasonic process was investigated. Results showed that ultrasonic process could remove 3.5% of methyl orange while catalytic ultrasonic process could remove 85% of methyl orange in 10 min. The effects of free radical scavengers were studied to determine the role of hydroxyl free radical in catalytic ultrasonic process. Results showed that methyl orange degradation efficiency declined after adding free radical scavengers, illustrating that hydroxyl free radical played an important role in degrading methyl orange. Theoretic analysis showed that the resonance size of cavitation bubbles was comparable with the size of catalyst particles. Thus, catalyst particles might act as cavitation nucleus and enhance ultrasonic cavitation effects. Measurement of H2O2 concentration in catalytic ultrasonic process confirmed this hypothesis. Effects of pre-adsorption on catalytic ultrasonic process were examined. Pre-adsorption significantly improved methyl orange removal. The potential explanation was that methyl orange molecules adsorbed on catalysts could enter cavitation bubbles and undergo stronger cavitation.

  9. Study on rare earth/alkaline earth oxide-doped CeO2 solid electrolyte

    Institute of Scientific and Technical Information of China (English)

    YAN Kai; ZHEN Qiang; Song Xiwen

    2007-01-01

    Five types of rare earth/alkaline earth oxide-doped CeO2 superfine-powders were synthesized by a low-temperature combustion technique. The relevant solid electrolyte materials were also sintered by pressureless sintering at different temperatures. The results of X-ray diffraction and transmission electron microscopy showed that the grain size of the powders was approximately 20-30 nm, and rare earth/alkaline earth oxides were completely dissolved into ceria-based solid solution with fluorite structure. The electrical conductivities of the Sm2O3-CeO2 system were measured by the ac impedance technique in air at temperatures ranging from 513-900℃. The results indicated that the ionic conductivities of Sm0.20Ce0.8O1.875 solid electrolyte increase with increasing sintering temperature, and the relationship between the conductivities and measuring temperature obeys the Arrhenius equation. Then the Sm2O3-CeO2 material was further doped with other rare earth/alkaline earth oxide, and the conductivities improve with the effective index.

  10. Synthesis, Characterization and Properties of CeO2-doped TiO2 Composite Nanocrystals

    Directory of Open Access Journals (Sweden)

    Oman ZUAS

    2013-12-01

    Full Text Available Pure TiO2 and CeO2-doped TiO2 (3 % CeO2-97 %TiO2 composite nanocrystals were synthesized via co-precipitation method and characterized using TGA, XRD, FTIR, DR-UV-vis and TEM. The XRD data revealed that the phase structure of the synthesized samples was mainly in pure anatase having crystallite size in the range of 7 nm – 11 nm. Spherical shapes with moderate aggregation of the crystal particles were observed under the TEM observation. The presence of the CeO2 at TiO2 site has not only affected morphologically but also induced the electronic property of the TiO2 by lowering the band gap energy from 3.29 eV (Eg-Ti to 3.15 eV (Eg-CeTi. Performance evaluation of the synthesized samples showed that both samples have a strong adsorption capacity toward Congo red (CR dye in aqueous solution at room temperature experiment, where  the capacity of the CeTi was higher than the Ti sample. Based on DR-UV data, the synthesized samples obtained in this study may also become promising catalysts for photo-assisted removal of synthetic dye in aqueous solution. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2732

  11. Hydriding/dehydriding properties of NdMgNi alloy with catalyst CeO2

    Institute of Scientific and Technical Information of China (English)

    李霞; 张羊换; 杨泰; 许剑轶; 赵栋梁

    2016-01-01

    Hydrogen storage composites Nd2Mg17-50 wt.%Ni-x wt.%CeO2 (x=0, 0.5, 1.0, 1.5, 2.0) were obtained by induction-ball milling method. The catalytic effect of CeO2 on hydriding kinetics of Nd2Mg17-50 wt.%Ni composite was investigated. X-ray diffrac-tion (XRD) and high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) analyses showed that Nd2Mg17-50 wt.%Ni alloy had a multiphase structure, consisting of NdMg12, NdMg2Ni, Mg2Ni and Ni phases and the addition of catalyst CeO2 prompted the composites to be partly transformed into amorphous strucutre. The CeO2 improved the maxi-mum hydrogen capacity of Nd2Mg17-50 wt.%Ni alloy from 3.192 wt.% to 3.376 wt.% (x=1.0). What’s more, the increment of diffu-sion coefficientD led to the faster hydriding kinetics, which was calculated by Avrami-Erofeev equation. The dehydrogenation tem-perature reduced from 515.54 to 504.72 K was mainly caused by the decrease of activation energy from 93.28 to 69.36 kJ/mol, which was proved by the Kissinger equation.

  12. RESPONSE OF SOIL MICROBIAL BIOMASS TO CeO2 NANOPARTICLES

    Directory of Open Access Journals (Sweden)

    Livia Vittori Antisari

    2011-12-01

    Full Text Available Aim of this work was to assess the impact of the chronic exposure of CeO2 nanoparticles (NPs (50 to 105 nm nominal size on soil microbial biomass.To evaluate if the CeO2 NPs can affect the soil quality, they were mixed to an A1 and A2 horizon of Epileptic Cambisols at a concentrations of 100 ppm and incubated in lab for short and medium (7 and 60 days times, at a constant temperature (25°C and moisture (60% WHC.The preliminary results of the soil physicochemical analyses have showed an insolubility of the CeO2 NPs at short-term incubation in water, EDTA and aqua regia. The biological assays detect a storing of Ce-CeO2 in the microbial biomass at short time that decreases in the C amount. An increment of the basal respiration and a decrease in the amount of carbon soil microbial biomass determined a higher metabolic quotient (qCO2 than the control test, that identifies a stressful situation, most evident in the short term condition.Physical-chemical characterization of the CeO2 NPs and of the soil before and after the NPs addition, was carried out by means of Environmental Scanning Electron Microscope (ESEM and an Energy Dispersive Spectroscopy (EDS. The investigations showed Ce-NPs and Ce-compounds in both- incubation-condition samples. The control soil showed the presence of cerium associated with other elements, like P, Nd, La, Th e Si. From literature, it appears that these elements identify Monazite-Ce/Nd minerals, whose chemical formulas are respectively (Ce, La, Nd, Th PO4 and (Nd, Ce, La (P, Si O4. The presence of CeO2 NPs was clearly detected in soil and recognized by ESEM morphological observations coupled with EDS characterization. The NPs chemical composition appears unaltered, while the size can be modified by NPs aggregation and clustering.The results contribute to setting reference baseline values of cerium in soil and indicate an impact on the amount of carbon soil microbial biomass due to a higher metabolic quotient (qCO2 that can condition the soil fertility.

  13. Enhancement of photocatalytic activity of combustion-synthesized CeO2/C3N4 nanoparticles

    Science.gov (United States)

    Li, Dong-Feng; Yang, Ke; Wang, Xiao-qin; Ma, Ya-Li; Huang, Gui-Fang; Huang, Wei-Qing

    2015-09-01

    Nanocrystalline CeO2/C3N4 was synthesized via a one-step solution combustion method using urea as fuel for the first time. The effects of the molar ratio of urea to cerium chloride on the photocatalytic activity of the synthesized samples were investigated. The synthesized nanocrystalline CeO2/C3N4 shows small size and large surface exposure area. Photocatalytic degradation of methylene blue demonstrates that the synthesized nanocrystalline CeO2/C3N4 possesses enhanced photocatalytic activity. It is proposed that the enhanced photocatalytic activity might be related to the favorable morphology and structure, and the effective charge separation between C3N4 and CeO2 in the photocatalytic process.

  14. The effect of CO-doped on the room-temperature ferromagnetism of CeO2 nanorods

    Science.gov (United States)

    Xu, H. F.; Li, H.

    2015-03-01

    Co-doped CeO2 nanorods of 10-20 nm in diameter and 200-600 nm or more in length have been synthesized by a simple co-precipitation method. The results of XRD and SADE analysis indicate that the as-synthesized CeO2 samples have the fluorite structure. X-ray photoelectron spectroscopy and Raman spectra show that Ce4+ and Ce3+ ions coexist at the surface of non-doped CeO2 nanorods. The magnetic measurements indicated that Co-doped CeO2 nanorods exhibit stronger ferromagnetism at room temperature, and while increasing the amount of Co ions, the ferromagnetism increase more, which can be associated with the presence of Ce3+ and Co2+.

  15. A facile method of fabricating mechanical durable anti-icing coatings based on CeO2 microparticles

    Science.gov (United States)

    Wang, Pengren; Peng, Chaoyi; Wu, Binrui; Yuan, Zhiqing; Yang, Fubiao; Zeng, Jingcheng

    2015-07-01

    Compromising between hydrophobicity and mechanical durability may be a feasible approach to fabricating usable anti-icing coatings. This work improves the contact angle of current commercial anti-icing coatings applied to wind turbine blades dramatically and keeps relatively high mechanical durability. CeO2 microparticles and diluent were mixed with fluorocarbon resin to fabricate high hydrophobic coatings on the glass fiber reinforced epoxy composite substrates. The proportion of CeO2 microparticles and diluent influences the contact angles significantly. The optimum mass ratio of fluorocarbon resin to CeO2 microparticles to diluent is 1:1.5:1, which leads to the highest contact angle close to 140°. The microscopy analysis shows that the CeO2 microparticles form nano/microscale hierarchical structure on the surface of the coatings.

  16. Studies on the Surface Morphology and Orientation of CeO2 Films Deposited by Pulsed Laser Ablation

    Science.gov (United States)

    Develos, Katherine; Kusunoki, Masanobu; Ohshima, Shigetoshi

    1998-11-01

    We studied the surface morphology and orientation of CeO2 films grown by pulsed laser ablation (PLA) on r-cut (1\\=102) Al2O3 substrates and evaluated the effects of predeposition annealing conditions of Al2O3 and film thickness of CeO2. The annealing of Al2O3 substrates improves the smoothness of the surface and performing this in high vacuum leads to better crystallinity and orientation of deposited CeO2 films compared to those annealed in oxygen. A critical value of the film thickness was found beyond which the surface roughness increases abruptly. Atomic force microscopy (AFM) study showed that the surface of CeO2 films is characterized by a mazelike pattern. Increasing the film thickness leads to the formation of larger islands which cause the increase in the surface roughness of the films. The areal density and height of these islands increased with film thickness.

  17. Water Dissociation on CeO2(100) and CeO2(111) Thin Films

    Energy Technology Data Exchange (ETDEWEB)

    Mullins, David R [ORNL; Albrecht, Peter M [ORNL; Chen, Tsung-Liang [ORNL; Calaza, Florencia C [ORNL; Biegalski, Micahel [Oak Ridge National Laboratory (ORNL); Christen, Hans [Oak Ridge National Laboratory (ORNL); Overbury, Steven {Steve} H [ORNL

    2012-01-01

    This study reports and compares the adsorption and dissociation of water on oxidized and reduced CeO{sub 2}(100) and CeO{sub 2}(111) thin films. Water adsorbs dissociatively on both surfaces. On fully oxidized CeO{sub 2}(100) the resulting surface hydroxyls are relatively stable and recombine and desorb as water over a range from 200 to 600 K. The hydroxyls are much less stable on oxidized CeO{sub 2}(111), recombining and desorbing between 200 and 300 K. Water produces 30% more hydroxyls on reduced CeO{sub 1.7}(100) than on oxidized CeO{sub 2}(100). The hydroxyl concentration increases by 160% on reduced CeO{sub 1.7}(111) compared to oxidized CeO{sub 2}(111). On reduced CeO{sub 1.7}(100) most of the hydroxyls still recombine and desorb as water between 200 and 750 K. Most of the hydroxyls on reduced CeO{sub 1.7}(111) react to produce H{sub 2} at 560 K, leaving O on the surface. A relatively small amount of H{sub 2} is produced from reduced CeO{sub 1.7}(100) between 450 and 730 K. The differences in the adsorption and reaction of water on CeO{sub X}(100) and CeO{sub X}(111) are attributed to different adsorption sites on the two surfaces. The adsorption site on CeO{sub 2}(100) is a bridging site between two Ce cations. This adsorption site does not change when the ceria is reduced. The adsorption site on CeO{sub 2}(111) is atop a single Ce cation, and the proton is transferred to a surface O in a site between three Ce cations. When the CeO{sub X}(111) is reduced, vacancy sites are produced which allows the water to adsorb and dissociate on the 3-fold Ce cation sites.

  18. Microstructure and corrosion resistance of Ni-based alloy laser coatings with nanosize CeO2 addition

    Directory of Open Access Journals (Sweden)

    Shi Hong Zhang et al

    2008-01-01

    Full Text Available Micron-size Ni-base alloy (NBA powders were mixed with both 1.5 wt.% (hereinafter % micron-size CeO2 (m-CeO2 and also 1.5% and 3.0% nano-size CeO2 (n- CeO2 powders. These mixtures were coated on low-carbon steel (Q235 by 2.0 kW CO2 laser cladding. The effects on the microstructures, phases and electrochemical corrosion of the coatings upon the addition of m- and n- CeO2 powders to NBA (m- and n- CeO2 /NBA have been investigated. The results showed that a smooth coating was prepared under suitable processing parameters (P= 2.0 kW, V= 180 mm min- 1 by adding 1.5% n- CeO2. In addition to the primary phases of γ-Ni, Cr23 C6 and Ni3 B in the Ni-base alloy coating, CeNi3 was formed in Ni-base alloy coatings with both n- CeO2 and m-CeO2 particles, and CeNi5 appeared in the coating upon decreasing the size of CeO2 particles. Well-developed dendrites were observed in the Ni-base alloy coating; directional dendrites grew at the interface in the coating upon the addition of m-CeO2, whereas fine and multioriented dendrites grew upon decreasing the size of CeO2 particles to the nanoscale. Actinomorphic dendrites and compact equiaxed dendrites grew from the interface to near the surface upon increasing the content of n- CeO2 from 1.5 to 3.0%. In strongly acidic HNO3 solution, the severe corrosion of dendrites occurred and there were many corrosion pits in the Ni-base alloy coating; intercrystalline corrosion also has a dominant role upon the addition of m-CeO2, whereas uniform corrosion occurs in the coating as the size of CeO2 particles is decreased to nanoscale.

  19. In vitro skin decontamination of the organophosphorus pesticide Paraoxon with nanometric cerium oxide CeO2.

    Science.gov (United States)

    Salerno, Alicia; Devers, Thierry; Bolzinger, Marie-Alexandrine; Pelletier, Jocelyne; Josse, Denis; Briançon, Stéphanie

    2017-04-01

    Organophosphorus compounds (OP), which mainly penetrate via the percutaneous pathway, represent a threat for both military and civilians. Body surface decontamination is vital to prevent victims poisoning. The development of a cost-effective formulation, which could be efficient and easy to handle in case of mass contamination, is therefore crucial. Metal oxides nanoparticles, due their large surface areas and the large amount of highly reactive sites, present high reactivity towards OP. First, this study aimed at evaluating the reaction of CeO2 nanoparticles, synthetized by microwave path and calcined at 500 or 600 °C, with Paraoxon (POX) in aqueous solution. Results showed that both nanoparticles degraded 60%-70% of POX. CeO2 calcined at 500 °C, owing to its larger specific area, was the most effective. Moreover, the degradation was significantly increased under Ultra-Violet irradiation (initial degradation rate doubled). Then, skin decontamination was studied in vitro using the Franz cell method with pig-ear skin samples. CeO2 powder and an aqueous suspension of CeO2 (CeO2-W) were applied 1 h after POX exposure. The efficiency of decontamination, including removal and/or degradation of POX, was compared to Fuller's earth (FE) and RSDL lotion which are, currently, the most efficient systems for skin decontamination. CeO2-W and RSDL were the most efficient to remove POX from the skin surface and decrease skin absorption by 6.4 compared to the control not decontaminated. FE reduced significantly (twice) the absorbed fraction of POX, contrarily to CeO2 powder. Considering only the degradation rate of POX, the products ranged in the order CeO2 > RSDL > CeO2-W > FE (no degradation). This study showed that CeO2 nanoparticles are a promising material for skin decontamination of OP if formulated as a dispersion able to remove POX like CeO2-W and to degrade it as CeO2 powder.

  20. Photocatalytic activity of the binary composite CeO2/SiO2 for degradation of dye

    Science.gov (United States)

    Phanichphant, Sukon; Nakaruk, Auppatham; Channei, Duangdao

    2016-11-01

    In this study, CeO2 photocatalyst was modified by composite with SiO2 to increase efficiency and improve photocatalytic activity. The as-prepared SiO2 particles have been incorporated into the precursor mixture of CeO2 by homogeneous precipitation and subsequent calcination process. The phase compositions of CeO2 before and after compositing with SiO2 were identified by X-ray diffraction (XRD). The morphology and particle size of CeO2/SiO2 composite was analyzed by high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM). The results showed SiO2 spheres with the particle size approximately 100-120 nm, and a uniform layer of CeO2 nanoparticles with a diameter of about 5-7 nm that were fully composite to the surfaces of SiO2. The X-ray photoelectron spectroscopy (XPS) technique was carried out in order to characterize the change in valence state and composite characteristic by shifted peaks of binding energies. The photocatalytic activity was studied through the degradation of Rhodamine B in aqueous solution under visible light exposure. The highest photocatalytic efficiency of CeO2/SiO2 composite was also obtained. To explain the high photocatalytic efficiency of CeO2/SiO2 composite, the proposed mechanism involves the high surface properties of the CeO2/SiO2 composite, as measured by Brunauer-Emmett-Teller (BET) method.

  1. Synthesis of mesoporous CeO2-MnOx binary oxides and their catalytic performances for CO oxidation

    Institute of Scientific and Technical Information of China (English)

    詹望成; 张欣烨; 郭杨龙; 王丽; 郭耘; 卢冠忠

    2014-01-01

    Mesoporous CeO2-MnOx binary oxides with different Mn/Ce molar ratios were prepared by hydrothermal synthesis and characterized by scanning electron microscopy (SEM), N2 sorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and H2 temperature-programmed reduction (H2-TPR). The characterization results indicated that the CeO2-MnOx catalysts exhibited flower-like microspheres with high specific surface areas, and partial Mn cations could be incorporated into CeO2 lattice to form solid solution. The CeO2-MnOx catalysts showed better catalytic activity for CO oxidation than that prepared by the coprecipitation method. Furthermore, the CeO2-MnOx catalyst with Mn/Ce molar ratio of 1 in the synthesis gel (Ce-Mn-1) exhibited the best catalytic activity, over which the conversion of CO could achieve 90%at 135 ºC. This was ascribed to presence of more Mn species with higher oxida-tion state on the surface and the better reducibility over the Ce-Mn-1 catalyst than other CeO2-MnOx catalysts.

  2. Effect of CeO2 on Microstructure and Bond Strength of Fe-Ni-Cr Alloy

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhenyu; Wang Zhiping; Liang Bunü

    2005-01-01

    Fe-Ni-Cr alloy powders with and without 0.4% CeO2 were flame sprayed on the surface of 1045 carbon steel substrate. The effect of rare earth oxide CeO2 on the interface layer and microstructure was investigated by X-ray diffraction analysis, SEM and EDS. Based on our previous work, comparison on the microstructure of a Fe-Ni-Cr alloy with and without 0.4% CeO2 addition was made. The correlation between the microstructure and bond strength was studied. The addition of CeO2 in Fe-Ni-Cr alloy shows promise results for providing good bonding strength as well as tribological properties. The results show that the hardness of the coatings can be improved by addition of 0.4% CeO2, and the shape of powders is more spheroidal. The combination of three aspects, namely small, well-distributed microstructure, the well-distributed matrix and promotion of diffusion leads to the improvement in bond strength of Fe-Ni-Cr alloy with addition of 0.4% CeO2.

  3. Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies.

    Science.gov (United States)

    Ravishankar, Thammadihalli Nanjundaiah; Ramakrishnappa, Thippeswamy; Nagaraju, Ganganagappa; Rajanaika, Hanumanaika

    2015-04-01

    CeO2 nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO2 nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO2 having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm(-1) due to the Ce-O-Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO2 nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO2 nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO2 nanoparticles also reduce Cr(VI) to Cr(III) and show antibacterial activity against Pseudomonas aeruginosa.

  4. Fate and Phytotoxicity of CeO2 Nanoparticles on Lettuce Cultured in the Potting Soil Environment.

    Science.gov (United States)

    Gui, Xin; Zhang, Zhiyong; Liu, Shutong; Ma, Yuhui; Zhang, Peng; He, Xiao; Li, Yuanyuan; Zhang, Jing; Li, Huafen; Rui, Yukui; Liu, Liming; Cao, Weidong

    2015-01-01

    Cerium oxide nanoparticles (CeO2 NPs) have been shown to have significant interactions in plants. Previous study reported the specific-species phytotoxicity of CeO2 NPs by lettuce (Lactuca sativa), but their physiological impacts and vivo biotransformation are not yet well understood, especially in relative realistic environment. Butterhead lettuce were germinated and grown in potting soil for 30 days cultivation with treatments of 0, 50, 100, 1000 mg CeO2 NPs per kg soil. Results showed that lettuce in 100 mg·kg-1 treated groups grew significantly faster than others, but significantly increased nitrate content. The lower concentrations treatment had no impact on plant growth, compared with the control. However, the higher concentration treatment significantly deterred plant growth and biomass production. The stress response of lettuce plants, such as Superoxide dismutase (SOD), Peroxidase (POD), Malondialdehyde(MDA) activity was disrupted by 1000 mg·kg-1 CeO2 NPs treatment. In addition, the presence of Ce (III) in the roots of butterhead lettuce explained the reason of CeO2 NPs phytotoxicity. These findings demonstrate CeO2 NPs modification of nutritional quality, antioxidant defense system, the possible transfer into the food chain and biotransformation in vivo.

  5. Mild activation of CeO2-supported gold nanoclusters and insight into the catalytic behavior in CO oxidation.

    Science.gov (United States)

    Li, Weili; Ge, Qingjie; Ma, Xiangang; Chen, Yuxiang; Zhu, Manzhou; Xu, Hengyong; Jin, Rongchao

    2016-01-28

    We report a new activation method and insight into the catalytic behavior of a CeO2-supported, atomically precise Au144(SR)60 nanocluster catalyst (where thiolate -SR = -SCH2CH2Ph) for CO oxidation. An important finding is that the activation of the catalyst is closely related to the production of active oxygen species on CeO2, rather than ligand removal of the Au144(SR)60 clusters. A mild O2 pretreatment (at 80 °C) can activate the catalyst, and the addition of reductive gases (CO or H2) can enhance the activation effects of O2 pretreatment via a redox cycle in which CO could reduce the surface of CeO2 to produce oxygen vacancies-which then adsorb and activate O2 to produce more active oxygen species. The CO/O2 pulse experiments confirm that CO is adsorbed on the cluster catalyst even with ligands on, and active oxygen species present on the surface of the pretreated catalyst reacts with CO pulses to generate CO2. The Au144(SR)60/CeO2 exhibits high CO oxidation activity at 80 °C without the removal of thiolate ligands. The surface lattice-oxygen of the support CeO2 possibly participates in the oxidation of CO over the Au144(SR)60/CeO2 catalyst.

  6. MnO2/CeO2 for catalytic ultrasonic decolorization of methyl orange: Process parameters and mechanisms.

    Science.gov (United States)

    Zhao, He; Zhang, Guangming; Chong, Shan; Zhang, Nan; Liu, Yucai

    2015-11-01

    MnO2/CeO2 catalyst was prepared and characterized by means of Brunauer-Emmet-Teller (BET) method, X-ray diffraction (XRD) and scanning electron microscope (SEM). The characterization showed that MnO2/CeO2 had big specific surface area and MnO2 was dispersed homogeneously on the surface of CeO2. Excellent degradation efficiency of methyl orange was achieved by MnO2/CeO2 catalytic ultrasonic process. Operating parameters were studied and optimized. The optimal conditions were 10 min of ultrasonic irradiation, 1.0 g/L of catalyst dose, 2.6 of pH value and 1.3 W/ml of ultrasonic density. Under the optimal conditions, nearly 90% of methyl orange was removed. The mechanism of methyl orange degradation was further studied. The decolorization mechanism in the ultrasound-MnO2/CeO2 system was quite different with that in the ultrasound-MnO2 system. Effects of manganese and cerium in catalytic ultrasonic process were clarified. Manganese ions in solution contributed to generating hydroxyl free radical. MnO2/CeO2 catalyst strengthened the oxidation ability of ultrasound and realized complete decolorization of methyl orange.

  7. CeO2 nanoparticles induce no changes in phenanthrene toxicity to the soil organisms Porcellionides pruinosus and Folsomia candida.

    Science.gov (United States)

    Tourinho, Paula S; Waalewijn-Kool, Pauline L; Zantkuijl, Irene; Jurkschat, Kerstin; Svendsen, Claus; Soares, Amadeu M V M; Loureiro, Susana; van Gestel, Cornelis A M

    2015-03-01

    Cerium oxide nanoparticles (CeO2 NPs) are used as diesel fuel additives to catalyze oxidation. Phenanthrene is a major component of diesel exhaust particles and one of the most common pollutants in the environment. This study aimed at determining the effect of CeO2 NPs on the toxicity of phenanthrene in Lufa 2.2 standard soil for the isopod Porcellionides pruinosus and the springtail Folsomia candida. Toxicity tests were performed in the presence of CeO2 concentrations of 10, 100 or 1000mg Ce/kg dry soil and compared with results in the absence of CeO2 NPs. CeO2 NPs had no adverse effects on isopod survival and growth or springtail survival and reproduction. For the isopods, LC50s for the effect of phenanthrene ranged from 110 to 143mg/kg dry soil, and EC50s from 17.6 to 31.6mg/kg dry soil. For the springtails, LC50s ranged between 61.5 and 88.3mg/kg dry soil and EC50s from 52.2 to 76.7mg/kg dry soil. From this study it may be concluded that CeO2 NPs have a low toxicity and do not affect toxicity of phenanthrene to isopods and springtails.

  8. Solid state sintering of lime in presence of La2O3 and CeO2

    Indian Academy of Sciences (India)

    T K Bhattacharya; A Ghosh; H S Tripathi; S K Das

    2003-12-01

    The sintering of lime by double calcination process from natural limestone has been conducted with La2O3 and CeO2 additive up to 4 wt.% in the temperature range 1500–1650°C. The results show that the additives enhanced the densification and hydration resistance of sintered lime. Densification is achieved up to 98.5% of the theoretical value with La2O3 and CeO2 addition in lime. Grain growth is substantial when additives are incorporated in lime. The grain size of sintered CaO (1600°C) with 4 wt.% La2O3 addition is 82 m and that for CeO2 addition is 50 m. The grains of sintered CaO in presence of additive are angular with pores distributed throughout the matrix. EDX analysis shows that the solid solubility of La2O3 and CeO2 in CaO grain is 2.9 and 1.7 weight %, respectively. The cell dimension of CaO lattice is 4.803 Å. This value decreases with incorporation of La2O3 and CeO2. The better hydration resistance of La2O3 added sintered lime compared to that of CeO2 added one, is related to the bigger grain size of the lime in former case.

  9. Catalytic oxidation of benzene over nanostructured porous Co3O4-CeO2 composite catalysts

    Institute of Scientific and Technical Information of China (English)

    Chunyan Ma; Zhen Mu; Chi He; Peng Li; Jinjun Li; Zhengping Hao

    2011-01-01

    Mesostructured Co3O4-CeO2 composite was found to be an effective catalytic material for the complete oxidation of benzene.The Co3O4-CeO2 catalysts with different Co/Ce ratios (mol/mol) were prepared via the nanocasting method and the mesostructure was replicated from two-dimensional (2D) hexagonal SBA-15 and three-dimensional (3D) cubic KIT-6 silicas,respectively.All the obtained Co3O4-CeO2 catalysts exhibited the similar symmetry with the parent silicas and well ordered mesostructures.The Co3O4-CeO2 catalysts with 2D mesostructure showed lower catalytic activities than the corresponding 3D materials.The Co3O4-CeO2 catalyst nanocasted from KIT-6 and with the Co/Ce ratio of 16/1 possessed the best catalytic benzene oxidation activity due to larger quantities of surface hydroxyl groups and surface oxygenated species.The mesostructured Co3O4-CeO2 material thus shows great potential as a promising eco-environmental catalyst for benzene effective elimination.

  10. Low-temperature selective catalytic reduction of NO on CeO2-CuO/Al2O3 catalysts prepared by different methods.

    Science.gov (United States)

    Guo, Rui-Tang; Zhen, Wen-Long; Pan, Wei-Guo; Hong, Jie-Nan; Jin, Qiang; Ding, Cheng-Gang; Guo, Shi-Yi

    2014-08-01

    CeO2-CuO/Al2O3 catalysts were prepared by three different methods and their activities for selective catalytic reduction (SCR) of NO with NH3 were investigated. As can be seen from the experimental results, the catalyst prepared by the single-step sol-gel (SG) method showed the best SCR activity and resistance to SO2 and H2O. In order to investigate the relationship between the preparation method and the performance of SCR catalysts, the catalysts were characterized by using Brunauer-Emmett-Teller, X-ray diffraction, temperature programmed reduction with hydrogen, temperature programmed desorption with ammonia, X-ray photoelectron spectroscopy, Fourier transform infrared and thermo-gravimetric analysis techniques. It was found that the excellent performance of CeO2-CuO/Al2O3 catalyst prepared by the single-step SG method should be resulted from its large surface area, low crystallinity, high oxygen storage capacity, high NH3 adsorption capacity, high concentration of surface chemisorbed oxygen, weak sulphation process and weak water absorption.

  11. Using single buffers and data reorganization to implement a multi-megasample fast Fourier transform

    Science.gov (United States)

    Brown, R. D.

    1992-01-01

    Data ordering in large fast Fourier transforms (FFT's) is both conceptually and implementationally difficult. Discribed here is a method of visualizing data orderings as vectors of address bits, which enables the engineer to use more efficient data orderings and reduce double-buffer memory designs. Also detailed are the difficulties and algorithmic solutions involved in FFT lengths up to 4 megasamples (Msamples) and sample rates up to 80 MHz.

  12. Reverse Monte Carlo studies of CeO2 using neutron and synchrotron radiation techniques

    Science.gov (United States)

    Clark, Adam H.; Marchbank, Huw R.; Hyde, Timothy I.; Playford, Helen Y.; Tucker, Matthew G.; Sankar, Gopinathan

    2017-03-01

    A reverse Monte Carlo analysis method was employed to extract the structure of CeO2 from Neutron total scattering (comprising both neutron diffraction (ND) and pair-distribution functions (PDF) and Ce L3- and K-edge EXAFS data. Here it is shown that there is a noticeable difference between using short ranged x-ray absorption spectroscopy data and using medium-long range PDF and ND data in regards to the disorder of the cerium atoms. This illustrates the importance of considering multiple length scales and radiation sources.

  13. Role of Microstructure and Surface Defects on the Dissolution Kinetics of CeO2, a UO2 Fuel Analogue.

    Science.gov (United States)

    Corkhill, Claire L; Bailey, Daniel J; Tocino, Florent Y; Stennett, Martin C; Miller, James A; Provis, John L; Travis, Karl P; Hyatt, Neil C

    2016-04-27

    The release of radionuclides from spent fuel in a geological disposal facility is controlled by the surface mediated dissolution of UO2 in groundwater. In this study we investigate the influence of reactive surface sites on the dissolution of a synthesized CeO2 analogue for UO2 fuel. Dissolution was performed on the following: CeO2 annealed at high temperature, which eliminated intrinsic surface defects (point defects and dislocations); CeO2-x annealed in inert and reducing atmospheres to induce oxygen vacancy defects and on crushed CeO2 particles of different size fractions. BET surface area measurements were used as an indicator of reactive surface site concentration. Cerium stoichiometry, determined using X-ray Photoelectron Spectroscopy (XPS) and supported by X-ray Diffraction (XRD) analysis, was used to determine oxygen vacancy concentration. Upon dissolution in nitric acid medium at 90 °C, a quantifiable relationship was established between the concentration of high energy surface sites and CeO2 dissolution rate; the greater the proportion of intrinsic defects and oxygen vacancies, the higher the dissolution rate. Dissolution of oxygen vacancy-containing CeO2-x gave rise to rates that were an order of magnitude greater than for CeO2 with fewer oxygen vacancies. While enhanced solubility of Ce(3+) influenced the dissolution, it was shown that replacement of vacancy sites by oxygen significantly affected the dissolution mechanism due to changes in the lattice volume and strain upon dissolution and concurrent grain boundary decohesion. These results highlight the significant influence of defect sites and grain boundaries on the dissolution kinetics of UO2 fuel analogues and reduce uncertainty in the long term performance of spent fuel in geological disposal.

  14. Comparison of superconducting properties between FeSe0.5Te0.5/CeO2/SrTiO3 and FeSe0.5Te0.5/SrTiO3 thin films

    Science.gov (United States)

    Chen, S. H.; Han, Y. Y.; Liu, J. Z.; Wang, T.; Tian, M. L.; Wen, H. H.; Xing, Z. W.

    2016-09-01

    The electrical resistance behaviors under angle-dependent magnetic fields up to 16 T are investigated in superconducting FeSe0.5Te0.5 (FST) thin films grown on SrTiO3 (STO) substrates without or with a CeO2 buffer layer. It is found that the FST/CeO2/STO films have an enhanced superconducting transition temperature Tc and slightly increased superconducting anisotropy in comparison with the FST/STO films. The enhancement of Tc in the presence of the CeO2 buffer is closely related to the changes in both the out-of-plane lattice constant and Se-Fe-Se (Te-Fe-Te) bond angle.

  15. Effect of short-term alkaline intervention on the performance of buffer-free single-chamber microbial fuel cell.

    Science.gov (United States)

    Yang, Na; Ren, Yueping; Li, Xiufen; Wang, Xinhua

    2017-06-01

    Anolyte acidification is a drawback restricting the electricity generation performance of the buffer-free microbial fuel cells (MFC). In this paper, a small amount of alkali-treated anion exchange resin (AER) was placed in front of the anode in the KCl mediated single-chamber MFC to slowly release hydroxyl ions (OH(-)) and neutralize the H(+) ions that are generated by the anodic reaction in two running cycles. This short-term alkaline intervention to the KCl anolyte has promoted the proliferation of electroactive Geobacter sp. and enhanced the self-buffering capacity of the KCl-AER-MFC. The pH of the KCl anolyte in the KCl-AER-MFC increased and became more stable in each running cycle compared with that of the KCl-MFC after the short-term alkaline intervention. The maximum power density (Pmax) of the KCl-AER-MFC increased from 307.5mW·m(-2) to 542.8mW·m(-2), slightly lower than that of the PBS-MFC (640.7mW·m(-2)). The coulombic efficiency (CE) of the KCl-AER-MFC increased from 54.1% to 61.2% which is already very close to that of the PBS-MFC (61.9%). The results in this paper indicate that short-term alkaline intervention to the anolyte is an effective strategy to further promote the performance of buffer-free MFCs.

  16. Stability of engineered nanomaterials in complex aqueous matrices: Settling behaviour of CeO2 nanoparticles in natural surface waters.

    Science.gov (United States)

    Van Koetsem, Frederik; Verstraete, Simon; Van der Meeren, Paul; Du Laing, Gijs

    2015-10-01

    The stability of engineered nanoparticles (ENPs) in complex aqueous matrices is a key determinant of their fate and potential toxicity towards the aquatic environment and human health. Metal oxide nanoparticles, such as CeO2 ENPs, are increasingly being incorporated into a wide range of industrial and commercial applications, which will undoubtedly result in their (unintentional) release into the environment. Hereby, the behaviour and fate of CeO2 ENPs could potentially serve as model for other nanoparticles that possess similar characteristics. The present study examined the stability and settling of CeO2 ENPs (7.3±1.4 nm) as well as Ce(3+) ions in 10 distinct natural surface waters during 7d, under stagnant and isothermal experimental conditions. Natural water samples were collected throughout Flanders (Belgium) and were thoroughly characterized. For the majority of the surface waters, a substantial depletion (>95%) of the initially added CeO2 ENPs was observed just below the liquid surface of the water samples after 7d. In all cases, the reduction was considerably higher for CeO2 ENPs than for Ce(3+) ions (CeO2 ENPs (R(2)≥0.998) and Ce(3+) ions (R(2)≥0.812) from the water column, at least in case notable sedimentation occurred over time. Solution-pH appeared to be a prime parameter governing nanoparticle colloidal stability. Moreover, the suspended solids (TSS) content also seemed to be an important factor affecting the settling rate and residual fraction of CeO2 ENPs as well as Ce(3+) ions in natural surface waters. Correlation results also suggest potential association and co-precipitation of CeO2 ENPs with aluminium- and iron-containing natural colloidal material. The CeO2 ENPs remained stable in dispersion in surface water characterized by a low pH, ionic strength (IS), and TSS content, indicating the eventual stability and settling behaviour of the nanoparticles was likely determined by a combination of physicochemical parameters. Finally, ionic release from the nanoparticle surface was also examined and appeared to be negligible in all of the tested natural waters.

  17. Synthesis and characterization of Sm3+-doped CeO2 powders

    Institute of Scientific and Technical Information of China (English)

    LIU Guo-cong; CHEN Li-miao; DUAN Xue-chen; LIANG Da-wen

    2008-01-01

    Sm3+-doped CeO2 (denoted as Ce1-xSmxO2) powders with different morphologies were successfully synthesized via a precursor-growth-calcination approach, in which precursor was first synthesized by a hydrothermal method and Ce1-xSmxO2 powders were finally obtained through a calcination process. The products were characterized with X-ray diffractometry(XRD), field emission scanning electron microscopy(FE-SEM) and fluorescence spectroscopy. The results reveal that the Ce1-xSmxO2 powders obtained by calcining the precursors prepared in the absence and presence of poly(vinyl pyrrolidone) (PVP) exhibit bundle- and sphere-like morphology, respectively. The possible growth process was proposed by preparing a series of intermediate morphologies during the shape evolution of CeO2 based on the SEM image observation. It is also found that the luminescence intensity of bundle-like Ce1-xSmxO2 is enhanced in comparison with that of sphere-like one due to its special morphology.

  18. Electrical and microstructural properties of Yb-doped CeO2

    Directory of Open Access Journals (Sweden)

    B. Matović

    2014-06-01

    Full Text Available Nanopowdered Ce1−xYbxO2−δ solid solutions (0 ≤ x ≤ 0.2 were synthesized by a self-propagating room temperature synthesis. XRD and SEM were used to study the properties of these materials as well as the Yb solubility in CeO2 lattice. Results showed that all the obtained powders were solid solutions with a fluorite-type crystal structure and with nanometric particle size. The average size of Ce1−xYbxO2−δ particles was approximately 3 nm. Electrochemical impedance spectroscopy for the sintered pellets depicted that it was possible to separate Rbulk and Rgb in the temperature interval of 550–800 °C. The activation energy for the bulk conduction was 1.03 eV and for grain boundary conduction was 1.14 eV. Grain boundary resistivity dominates over the other resistivities. These measurements confirmed that Yb3+-doped CeO2 material had a potential as electrolyte for intermediate-temperature solid oxide fuel cell applications.

  19. Synthesis and Electrical Conductivities of Sm2O3-CeO2 Systems

    Institute of Scientific and Technical Information of China (English)

    Song Xiwen; Peng Jun; Zhao Yongwang; Zhao Wenguang; An Shengli

    2005-01-01

    Doped Ceria nano-powders were synthesized via a Pechini-type gel rout. The specific surface area of Ce0.8Sm0.2O1.9 powder measured by the multilayer BET method is 41 m2.g-1. The electrical conductivities of Sm2O3-CeO2 systems were measured by the ac impedance technique in air at temperatures ranging from 513 to 900 ℃. Typical impedance spectra consist of two depressed semicircles at reduced measuring temperature and one depressed semicircle at elevated measuring temperature respectively, from which the grain interior and grain boundary conductivities were calculated. The relationship between the conductivities of Sm2O3 doped CeO2 (SDC) electrolyte and measuring temperature obeys Arrhenius equation. The grain interior conductivity of SDC varies slightly with improving sintering temperature, while the total conductivity increases with enhancing sintering temperature. The effective index has a significant effect on the ionic conductivity of ceria doped based electrolyte. When the effective index improves, the ionic conductivity increases and the apparent conductance activation energy decreases.

  20. Fabrication, microstructure, and optical properties of nanocrystalline transparent LAST glass ceramics containing CeO2

    Institute of Scientific and Technical Information of China (English)

    Mohammad Sadegh Shakeri

    2014-01-01

    In the present research, the effect of CeO2 dopant on the fabrication of transparent lithium aluminosilicate titanate (LAST) glass ceramics was investigated. Nanocrystallineβ-quartz solid solution (s.s.) was observed to be the main phase crystallized in this system. Com-parable refractive indices of the glassy matrix andβ-quartz s.s., as well as the incorporation of very fine grains size were determined as the main reasons for retaining the transparency of the glass ceramics. CeO2 was introduced as a suitable optical agent, playing a role as a network modifier in the glass ceramics, because it does not accelerate the growth process and retards the extended growth of crystals. Optical investi-gations indicate that the Fermi energy level, direct and indirect band gaps, and Urbach energy decrease with increasing nanocrystal content in the glassy matrix of specimens, which can be related to the expansion of conduction band, the enhancement of ionic bonds in the crystal lat-tice, and the enhancement of structural arrangement degree, respectively.

  1. Flower-Like Mn-Doped CeO2 Microstructures: Synthesis, Characterizations, and Catalytic Properties

    Directory of Open Access Journals (Sweden)

    Ling Liu

    2015-01-01

    Full Text Available Mn-doped CeO2 flower-like microstructures have been synthesized by a facile method, involving the precipitation of metallic alkoxide precursor in a polyol process from the reaction of CeCl3·7H2O with ethylene glycol in the presence of urea followed by calcination. By introducing manganese ions, the composition can be freely manipulated. To investigate whether there was a hybrid synergic effect in CH4 combustion reaction, further detailed characteristics of Mn-doped CeO2 with various manganese contents were revealed by XRD, Raman, FT-IR, SEM, EDS, XPS, OSC, H2-TPR, and N2 adsorption-desorption measurements. The doping manganese is demonstrated to increase the storage of oxygen vacancy for CH4 and enhance the redox capability, which can efficiently convert CH4 to CO2 and H2O under oxygen-rich condition. The excellent catalytic performance of MCO-3 sample, which was obtained with the starting Mn/Ce ratios of 0.2 in the initial reactant compositions, is associated with the larger surface area and richer surface active oxygen species.

  2. Congestion control for ATM multiplexers using neural networks:multiple sources/single buffer scenario

    Institute of Scientific and Technical Information of China (English)

    杜树新; 袁石勇

    2004-01-01

    A new neural network based method for solving the problem of congestion control arising at the user network interface (UNI) of ATM networks is proposed in this paper. Unlike the previous methods where the coding rate for all traffic sources as controller output signals is tuned in a body, the proposed method adjusts the coding rate for only a part of the traffic sources while the remainder sources send the cells in the previous coding rate in case of occurrence of congestion. The controller output signals include the source coding rate and the percentage of the sources that send cells at the corresponding coding rate. The control methods not only minimize the cell loss rate but also guarantee the quality of information (such as voice sources) fed into the multiplexer buffer. Simulations with 150 ADPCM voice sources fed into the multiplexer buffer showed that the proposed methods have advantage over the previous methods in the aspect of the performance indices such as cell loss rate (CLR) and voice quality.

  3. Congestion control for ATM multiplexers using neural networks:multiple sources/single buffer scenario

    Institute of Scientific and Technical Information of China (English)

    杜树新; 袁石勇

    2004-01-01

    A new neural network based method for solving the problem of congestion control arising at the user network interface (UNI) of ATM networks is proposed in this paper. Unlike the previous methods where the coding rate for all traffic sources as controller output signals is tuned in a body, the proposed method adjusts the coding rate for only a part of the traffic sources while the remainder sources send the cells in the previous coding rate in case of occurrence of congestion. The controller output signals include the source coding rate and the percentage of the sources that send cells at the corresponding coding rate. The control methods not only minimize the cell loss rate but also guarantee the quality of information (such as voice sources) fed into the multiplexer buffer. Simulations with 150 ADPCM voice sources fed into the multiplexer buffer showed that the proposed methods have advantage over the previous methods in the aspect of the performance indices such as cell loss rate (CLR) and voice quality.

  4. Effects of CeO2 Support Facets on VOx/CeO2 Catalysts in Oxidative Dehydrogenation of Methanol

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan; Wei, Zhehao; Gao, Feng; Kovarik, Libor; Peden, Charles HF; Wang, Yong

    2014-05-13

    CeO2 supports with dominating facets, i.e., low index (100), (110) and (111) facets, are prepared. The facet effects on the structure and catalytic performance of supported vanadium oxide catalysts are investigated using oxidative dehydrogenation of methanol as a model reaction. In the presence of mixed facets, Infrared and Raman characterizations demonstrate that surface vanadia species preferentially deposit on CeO2 (100) facets, presumably because of its higher surface energy. At the same surface vanadium densities, VOx species on (100) facets show better dispersion, followed by (110) and (111) facets. The VOx species on CeO2 nanorods with (110) and (100) facets display higher activity and lower apparent activation energies compared to that on CeO2 nanopolyhedras with dominating (111) facets and CeO2 nanocubes with dominating (100) facets. The higher activity for VOx/CeO2(110) might be related to the more abundant oxygen vacancies present on the (110) facets, evidenced from Raman spectroscopic measurements.

  5. Effect of CeO2-ZrO2 on Pt/C electrocatalysts for alcohols oxidation

    Institute of Scientific and Technical Information of China (English)

    WANG Qingchun; LIU Zhenpeng; AN Shengli; WANG Ruifen; WANG Yanling; XU Tuo

    2016-01-01

    The electrocatalytic activity and stability of Pt/C catalyst modified by using CeO2-ZrO2 mixed oxides for the alcohols elec-trochemical oxidation as probes were investigated. The catalyst samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties were measured by a three electrode system on electrochemical work-station (IVIUM). The results showed that the presence of CeO2-ZrO2 might be associated with the presence of Pt, which indicated that possibly there was synergistic effect between CeO2-ZrO2 and Pt nanoparticles. The electrocatalytic activity and stability of Pt-MOx/C (M=Ce, Zr) for methanol and ethanol oxidation was better than that of Pt-CeO2/C, which was attributed to that CeO2-ZrO2 compo-sited oxides enhanced oxygen mobility and promoted oxygen storage capacity (OSC). Furthermore, the best performance was found when the molar ratio of CeO2 to ZrO2 was 2:1 for the oxidation of methanol and ethanol. The forward peak current density of Pt-MOx/C (M=Ce, Zr, Ce:Zr=2:1) towards the methanol electrooxidation was about 3.8 times that of Pt-CeO2/C. Pt-MOx/C (M=Ce, Zr) appeared to be a promising and less expensive methanol oxidation anode catalyst.

  6. Hydrogen and syngas production from two-step steam reforming of methane using CeO2 as oxygen carrier

    Institute of Scientific and Technical Information of China (English)

    Xing Zhu; Hua Wang; Yonggang Wei; Kongzhai Li; Xianming Cheng

    2011-01-01

    CeO2 oxygen carrier was prepared by precipitation method and tested by two-step steam reforming of methane (SRM).Two-step SRM for hydrogen and syngas generation is investigated in a fixed-bed reactor.Methane is directly converted to syngas at a H2/CO ratio close to 2∶ 1 at a high temperature (above 750 ℃) by the lattice oxygen of CeO2; methane cracking is found when the reduction degree of CeO2 was above 5.0% at 850 ℃ in methane isothermal reaction.CeO2-δ obtained from methane isothermal reaction can split water to generate CO-free hydrogen and renew its lattice oxygen at 700 ℃; simultaneously, deposited carbon is selectively oxidized to CO2 by steam following the reaction (C+2H2O→CO2+2H2).Slight deactivation in terms of amounts of desired products (syngas and hydrogen) is observed in ten repetitive two-step SRM process due to the carbon deposition on CeO2 surface as well as sintering of CeO2.

  7. Influence of two types of organic matter on interaction of CeO2 nanoparticles with plants in hydroponic culture.

    Science.gov (United States)

    Schwabe, Franziska; Schulin, Rainer; Limbach, Ludwig K; Stark, Wendelin; Bürge, Diane; Nowack, Bernd

    2013-04-01

    An important aspect in risk assessment of nanoparticles (NPs) is to understand their environmental interactions. We used hydroponic plant cultures to study nanoparticle-plant-root interaction and translocation and exposed wheat and pumpkin to suspensions of uncoated CeO2-NP for 8d (primary particle size 17-100 nm, 100 mg L(-1)) in the absence and presence of fulvic acid (FA) and gum arabic (GA) as representatives of different types of natural organic matter. The behavior of CeO2-NPs in the hydroponic solution was monitored regarding agglomeration, sedimentation, particle size distribution, surface charge, amounts of root association, and translocation into shoots. NP-dispersions were stable over 8d in the presence of FA or GA, but with growing plants, changes in pH, particle agglomeration rate, and hydrodynamic diameter were observed. None of the plants exhibited reduced growth or any toxic response during the experiment. We found that CeO2-NPs translocated into pumpkin shoots, whereas this did not occur in wheat plants. The presence of FA and GA affected the amount of CeO2 associated with roots (pure>FA>GA) but did not affect the translocation factor. Additionally, we could confirm via TEM and SEM that CeO2-NPs adhered strongly to root surfaces of both plant species.

  8. Enhanced Photoreduction Activity of Carbon Dioxide over Co3O4/CeO2 Catalysts under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Ying Huang

    2015-01-01

    Full Text Available A series of new two semiconductor catalysts, Co3O4/CeO2, were prepared by glycine-nitrate combustion method for photocatalytic reduction of carbon dioxide to produce methanol and ethanol under visible light (λ>400 nm irradiation. The catalysts were characterized by BET, UV-vis spectra, XRD, SEM, PL, and XPS and the results indicated that the catalyst with 5 wt.% of Co3O4 has the highest yield among all kinds of tests with the methanol yield of 1.52 μmol·g−1·h−1 and the ethanol yield of 4.75 μmol·g−1·h−1, which are about 2.34 and 1.71 times as large as those of CeO2. However, methanol and ethanol can hardly be detected for Co3O4 under the same condition because of its too narrow band gap. The improvement of the photoreduction activity of Co3O4 doped CeO2 was caused by the separation of electron-hole pairs of Co3O4/CeO2 and charge transfer between Co3O4 and CeO2, mimicking the Z-scheme in photosynthesis.

  9. Transformation of pristine and citrate-functionalized CeO2 nanoparticles in a laboratory-scale activated sludge reactor.

    Science.gov (United States)

    Barton, Lauren E; Auffan, Melanie; Bertrand, Marie; Barakat, Mohamed; Santaella, Catherine; Masion, Armand; Borschneck, Daniel; Olivi, Luca; Roche, Nicolas; Wiesner, Mark R; Bottero, Jean-Yves

    2014-07-01

    Engineered nanomaterials (ENMs) are used to enhance the properties of many manufactured products and technologies. Increased use of ENMs will inevitably lead to their release into the environment. An important route of exposure is through the waste stream, where ENMs will enter wastewater treatment plants (WWTPs), undergo transformations, and be discharged with treated effluent or biosolids. To better understand the fate of a common ENM in WWTPs, experiments with laboratory-scale activated sludge reactors and pristine and citrate-functionalized CeO2 nanoparticles (NPs) were conducted. Greater than 90% of the CeO2 introduced was observed to associate with biosolids. This association was accompanied by reduction of the Ce(IV) NPs to Ce(III). After 5 weeks in the reactor, 44 ± 4% reduction was observed for the pristine NPs and 31 ± 3% for the citrate-functionalized NPs, illustrating surface functionality dependence. Thermodynamic arguments suggest that the likely Ce(III) phase generated would be Ce2S3. This study indicates that the majority of CeO2 NPs (>90% by mass) entering WWTPs will be associated with the solid phase, and a significant portion will be present as Ce(III). At maximum, 10% of the CeO2 will remain in the effluent and be discharged as a Ce(IV) phase, governed by cerianite (CeO2).

  10. Laminated CeO2/HfO2 High-K Gate Dielectrics Grown by Pulsed Laser Deposition in Reducing Ambient

    NARCIS (Netherlands)

    Karakaya, K.; Barcones, B.; Zinine, A.; Rittersma, Z.M.; Graat, P.; Berkum, van J.G.M.; Verheijen, M.A.; Rijnders, G.; Blank, D.H.A.

    2006-01-01

    CeO2 and HfO2 dielectric layers were deposited in an Ar+(5%)H2 gas mixture by Pulsed Laser Deposition (PLD) on Si (100). A CeO2-Ce2O3 transformation is achieved by deposition in reducing ambient. It is also shown that in-situ post deposition anneal efficiently oxidizes Ce2O3 layers to CeO2. The prop

  11. A comparative study of CeO2-Al2O3 support prepared with different methods and its application on MoO3/CeO2-Al2O3 catalyst for sulfur-resistant methanation

    Science.gov (United States)

    Jiang, Minhong; Wang, Baowei; Yao, Yuqin; Li, Zhenhua; Ma, Xinbin; Qin, Shaodong; Sun, Qi

    2013-11-01

    The CeO2-Al2O3 supports prepared with impregnation (IM), deposition precipitation (DP), and solution combustion (SC) methods for MoO3/CeO2-Al2O3 catalyst were investigated in the sulfur-resistant methanation. The supports and catalysts were characterized by N2-physisorption, transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy (RS), and temperature-programmed reduction (TPR). The N2-physisorption results indicated that the DP method was favorable for obtaining better textural properties. The TEM and RS results suggested that there is a CeO2 layer on the surface of the support prepared with DP method. This CeO2 layer not only prevented the interaction between MoO3 and γ-Al2O3 to form Al2(MoO4)3 species, but also improved the dispersion of MoO3 in the catalyst. Accordingly, the catalysts whose supports were prepared with DP method exhibited the best catalytic activity. The catalysts whose supports were prepared with SC method had the worst catalytic activity. This was caused by the formation of Al2(MoO4)3 and crystalline MoO3. Additionally, the CeO2 layer resulted in the instability of catalysts in reaction process. The increasing of calcination temperature of supports reduced the catalytic activity of all catalysts. The decrease extent of the catalysts whose supports were prepared with DP method was the lowest as the CeO2 layer prevented the interaction between MoO3 and γ-Al2O3.

  12. Facile preparation of well-dispersed CeO2-ZnO composite hollow microspheres with enhanced catalytic activity for CO oxidation.

    Science.gov (United States)

    Xie, Qingshui; Zhao, Yue; Guo, Huizhang; Lu, Aolin; Zhang, Xiangxin; Wang, Laisen; Chen, Ming-Shu; Peng, Dong-Liang

    2014-01-08

    In this article, well-dispersed CeO2-ZnO composite hollow microspheres have been fabricated through a simple chemical reaction followed by annealing treatment. Amorphous zinc-cerium citrate hollow microspheres were first synthesized by dispersing zinc citrate hollow microspheres into cerium nitrate solution and then aging at room temperature for 1 h. By calcining the as-produced zinc-cerium citrate hollow microspheres at 500 °C for 2 h, CeO2-ZnO composite hollow microspheres with homogeneous composition distribution could be harvested for the first time. The resulting CeO2-ZnO composite hollow microspheres exhibit enhanced activity for CO oxidation compared with CeO2 and ZnO, which is due to well-dispersed small CeO2 particles on the surface of ZnO hollow microspheres and strong interaction between CeO2 and ZnO. Moreover, when Au nanoparticles are deposited on the surface of the CeO2-ZnO composite hollow microspheres, the full CO conversion temperature of the as-produced 1.0 wt % Au-CeO2-ZnO composites reduces from 300 to 60 °C in comparison with CeO2-ZnO composites. The significantly improved catalytic activity may be ascribed to the strong synergistic interplay between Au nanoparticles and CeO2-ZnO composites.

  13. Facile and Mild Strategy to Construct Mesoporous CeO2-CuO Nanorods with Enhanced Catalytic Activity toward CO Oxidation.

    Science.gov (United States)

    Chen, Guozhu; Xu, Qihui; Yang, Ying; Li, Cuncheng; Huang, Taizhong; Sun, Guoxin; Zhang, Shuxiang; Ma, Dongling; Li, Xu

    2015-10-28

    CeO2-CuO nanorods with mesoporous structure were synthesized by a facile and mild strategy, which involves an interfacial reaction between Ce2(SO4)3 precursor and NaOH ethanol solution at room temperature to obtain mesoporous CeO2 nanorods, followed by a solvothermal treatment of as-prepared CeO2 and Cu(CH3COO)2. Upon solvothermal treatment, CuO species is highly dispersed onto the CeO2 nanorod surface to form CeO2-CuO composites, which still maintain the mesoporous feature. A preliminary CO catalytic oxidation study demonstrated that the CeO2-CuO samples exhibited strikingly high catalytic activity, and a high CO conversion rate was observed without obvious loss in activity even after thermal treatment at a high temperature of 500 °C. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen temperature-programmed reduction (H2-TPR) analysis revealed that there is a strong interaction between CeO2 and CuO. Moreover, it was found that the introduction of CuO species into CeO2 generates oxygen vacancies, which is highly likely to be responsible for high catalytic activity toward CO oxidation of the mesoporous CeO2-CuO nanorods.

  14. BiVO(4)/CeO(2) nanocomposites with high visible-light-induced photocatalytic activity.

    Science.gov (United States)

    Wetchakun, Natda; Chaiwichain, Saranyoo; Inceesungvorn, Burapat; Pingmuang, Kanlaya; Phanichphant, Sukon; Minett, Andrew I; Chen, Jun

    2012-07-25

    Preparation of bismuth vanadate and cerium dioxide (BiVO4/CeO2) nanocomposites as visible-light photocatalysts was successfully obtained by coupling a homogeneous precipitation method with hydrothermal techniques. The BiVO4/CeO2 nanocomposites with different mole ratios were synthesized and characterized by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). Absorption range and band gap energy, which are responsible for the observed photocatalyst behavior, were investigated by UV-vis diffuse reflectance (UV-vis DR) spectroscopy. Photocatalytic activities of the prepared samples were examined by studying the degradation of model dyes Methylene Blue, Methyl Orange, and a mixture of Methylene Blue and Methyl Orange solutions under visible-light irradiation (>400 nm). Results clearly show that the BiVO4/CeO2 nanocomposite in a 0.6:0.4 mol ratio exhibited the highest photocatalytic activity in dye wastewater treatment.

  15. A rationale for the development of thermally stable nanostructured CeO2-ZrO2-containing mixed oxides

    Institute of Scientific and Technical Information of China (English)

    Roberta Di Monte; Jan Ka(s)par; Heather Bradshaw; Colin Norman

    2008-01-01

    CeO2-ZeO2 solid solutions are extensively used as oxygen storage promoters in the current automotive three-way catalysts. High thermal stability of the textural properties is one of the most important requirements for practical application since temperatures up to 1273 K are easily experienced by these materials under real working conditions. In the present paper, we investigated how hydrothermal treatments applied to cakes of doped and undoped ZrO2-rich CeO2-ZrO2 precursors might improve the thermal stability of the final CeO2-ZrO2 solid solution. A rationale was developed that allowed to correlate the morphology of the hydrothermally treated cake with the thermal stability at 1273 K of the final product, which did not depend on the composition of the mixed oxides.

  16. Fabrication of multianalyte CeO2 nanograin electrolyte–insulator–semiconductor biosensors by using CF4 plasma treatment

    Directory of Open Access Journals (Sweden)

    Chyuan Haur Kao

    2015-09-01

    Full Text Available Multianalyte CeO2 biosensors have been demonstrated to detect pH, glucose, and urine concentrations. To enhance the multianalyte sensing capability of these biosensors, CF4 plasma treatment was applied to create nanograin structures on the CeO2 membrane surface and thereby increase the contact surface area. Multiple material analyses indicated that crystallization or grainization caused by the incorporation of flourine atoms during plasma treatment might be related to the formation of the nanograins. Because of the changes in surface morphology and crystalline structures, the multianalyte sensing performance was considerably enhanced. Multianalyte CeO2 nanograin electrolyte–insulator–semiconductor biosensors exhibit potential for use in future biomedical sensing device applications.

  17. Effect of CeO2 on Electrical Properties of (Nb,Mn)-Doped TiO2 Varistor Ceramics

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The electrical properties of TiO2-based varistor ceramics with different amount of CeO2 were investigated by measuring the properties of V-I, permittivity, density and boundary defect barriers. It is found that an optimal composition doped with 0.7% CeO2 exhibits the highest nonlinear coefficient of 10.5, the highest breakdown voltage of 12.77consistent with the highest and narrowest grain-boundary defect barriers. In order to illustrate the grain boundary barriers formation in TiO2-Nb2O5-MnCO3-CeO2 varistor, an grain-boundary defect barrier model was also introduced.

  18. ARTICLES: Synthesis of Biomorphic ZrO2-CeO2 Nanostructures by Silkworm Silk Template

    Science.gov (United States)

    Zhang, Zong-jian; Li, Jia; Sun, Fu-sheng; Dickon, H. L. Ng; Luen Kwong, Fung

    2010-06-01

    A simple and green technique has been developed to prepare hierarchical biomorphic ZrO2-CeO2, using silkworm silk as the template. Different from traditional immersion technics, the whole synthesis process depends more on the restriction or direction functions of the silkworm silk template. The analytic results showed that ZrO2-CeO2 exhibited a well-crystallized hierarchically interwoven hollow fiber structure with 16-28 μm in diameter. The grain size of the sample calcined at 800 °C was about 14 nm. Consequently, the interwoven meshwork at three dimensions is formed due to the direction of biotemplate. The action mechanism is summarily discussed here. It may bring the biomorphic ZrO2-CeO2 nanomaterials with hierarchical interwoven structures to more applications, such as catalysts.

  19. Study on Mg-PSZ Ceramics Doped with Y2O3 and CeO2

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Mg-PSZ ceramics doped with Y2O3 and CeO2 was prepared using traditional processing method. The fine-grain PSZ ceramics(dc≤10 μm) sintered at low temperature(≤1550 ℃) was obtained by means of composition design. The effects of co-stabilization of Y2O3, CeO2 and annealing at 1100 ℃ on material composition, microstructure and mechanical properties were studied. The results show that Y2O3 and CeO2 during annealing at 1100 ℃ can inhibit subeutectoid decomposition reaction effectively, and optimize nucleation and growth of t-ZrO2 precipitates in c-ZrO2 matrix phase. The materials show transgranular and intergranular fracture characteristics, and exhibit better mechanical properties owing to the cooperative effect of stress-induced transformation toughening and microcrack toughening.

  20. Effects of CeO2 doping on the structure and properties of PSN-PZN-PMS-PZT piezoelectric ceramics

    Institute of Scientific and Technical Information of China (English)

    SUN Qingchi; LU Cuimin; ZHOU Hua

    2005-01-01

    Quinary system piezoelectric ceramics PSN-PZN-PMS-PZT were prepared by using a two-step method. The effects of CeO2 doping on piezoelectric and dielectric properties of the system were investigated at morphotropic phase boundary (MPB). The results reveal that the relative dielectric constant εT33 / ε0, the Curie temperature Tc, the piezoelectric constant d33, the mechanical quality factor Qm, and the electromechanical coupling coefficient Kp are changed with the increase of CeO2 content. On the other hand, the effects of CeO2 doping on the dielectric properties of PSN-PZN-PMS-PZT piezoelectric ceramics at high electric field are consistent with the change at weak electric field. The values of dielectric constant and dielectric loss are enhanced with the increasing of electric field.

  1. Controllable synthesis of CeO2/g-C3N4 composites and their applications in the environment.

    Science.gov (United States)

    She, Xiaojie; Xu, Hui; Wang, Hefei; Xia, Jiexiang; Song, Yanhua; Yan, Jia; Xu, Yuanguo; Zhang, Qi; Du, Daolin; Li, Huaming

    2015-04-21

    This research has developed a photocatalytic reactor that includes circulating water, light, and a temperature control system. CeO2/g-C3N4 composites with high photocatalytic activity and stability were synthesized by a simple and facile hydrothermal method. The obtained photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that in the CeO2/g-C3N4 composites, the CeO2 nanoparticles were homogeneously cubic in shape (from 3 to 10 nm) and were evenly dispersed on the surface of the g-C3N4. At constant temperature (30 °C), 5% CeO2/g-C3N4 photocatalyst showed the best photocatalytic activity for degrading organic dye methylene blue (MB) under visible light irradiation. The photocatalytic reaction for degrading MB followed first-order kinetics and 5% CeO2/g-C3N4 exhibited a higher apparent rate of 1.2686 min(-1), 7.8 times higher than that of the pure g-C3N4 (0.1621 min(-1)). In addition, it was found that 5% CeO2/g-C3N4 had a new property that it could be used as a sensor for the determination of trace amounts of Cu(2+). Such unique design and one-step synthesis, with an exposed high-activity surface, are important for both technical applications and theoretical investigations.

  2. Aqueous Chemical Solution Deposition of Novel, Thick and Dense Lattice-Matched Single Buffer Layers Suitable for YBCO Coated Conductors: Preparation and Characterization

    Directory of Open Access Journals (Sweden)

    Isabel van Driessche

    2012-09-01

    Full Text Available In this work we present the preparation and characterization of cerium doped lanthanum zirconate (LCZO films and non-stoichiometric lanthanum zirconate (LZO buffer layers on metallic Ni-5% W substrates using chemical solution deposition (CSD, starting from aqueous precursor solutions. La2Zr2O7 films doped with varying percentages of Ce at constant La concentration (La0.5CexZr1−xOy were prepared as well as non-stoichiometric La0.5+xZr0.5−xOy buffer layers with different percentages of La and Zr ratios. The variation in the composition of these thin films enables the creation of novel buffer layers with tailored lattice parameters. This leads to different lattice mismatches with the YBa2Cu3O7−x (YBCO superconducting layer on top and with the buffer layers or substrate underneath. This possibility of minimized lattice mismatch should allow the use of one single buffer layer instead of the current complicated buffer architectures such as Ni-(5% W/LZO/LZO/CeO2. Here, single, crack-free LCZO and non-stoichiometric LZO layers with thicknesses of up to 140 nm could be obtained in one single CSD step. The crystallinity and microstructure of these layers were studied by XRD, and SEM and the effective buffer layer action was studied using XPS depth profiling.

  3. In situ FT-IR study on CO oxidation over Co3O4/CeO2 catalyst%Co3O4/CeO2CO氧化的原位红外光谱研究

    Institute of Scientific and Technical Information of China (English)

    邵建军; 朱锡; 张永坤; 王明贵

    2012-01-01

    Co3O4/CeO2 catalyst was prepared by co-precipitation-oxidation method. Adsorption of carbon monoxide and the co-adsorption of CO/O2 over Co3O4/CeO2 sample were investigated. In situ FT-IR analysis of the mechanism in CO oxidation was interpreted over Co3O4/CeO2 sample. Effects of the reaction conditions on the catalytic performance over Co3O4/CeO2 catalyst for carbon monoxide oxidation was investigated at humid and dry conditions. Results indicated that the addition of cerium to the cobalt oxide was beneficial for CO oxidation over Co3O4 at humid condition. The formation of carbonate species with reaction on Co3O4/CeO2 composite oxide slightly deactivated the catalyst. When the temperature was as low as 453 K, the dynamic equilibrium of formation and decomposition of carbonate species existed in Co3O4/CeO2 composite oxide catalyst. The carbonate species disappeared above 493 K. The strong interaction between CeO2 and Co3O4 may contribute to the excellent water resistance for low-temperature CO oxidation over Co3O4/CeO2 catalyst at humid condition.%采用沉淀氧化法制备了Co3O4/CeO2催化剂.分别在干、湿条件下进行了一氧化碳氧化反应研究.运用FT-IR表征手段,在钴铈复合氧化物上进行了CO吸附及CO/O2共吸附研究.结果表明,与纯的Co3O4样品相比,Co3O4/CeO2具有明显的抗湿气能力.Co3O4/CeO2催化剂在进行CO氧化时,表面形成了类碳酸盐物种.当环境温度低于453K时,催化剂上类碳酸盐的生成与形成类碳酸盐物种后受热分解存在着动态平衡.当环境温度高于493K,催化剂上生成的类碳酸盐物全部受热分解.氧化铈的加入提高了催化剂的抗湿气性能.较小粒径的Co3O4与CeO2产生的强相互作用可使CeO2向Co3O4提供氧,因而间接提供了CO氧化需要的氧.

  4. Growth of YBCO Thin Films on TiN(001) and CeO2-Coated TiN Surfaces

    Science.gov (United States)

    2012-02-01

    AFRL-RZ-WP-TP-2012-0102 GROWTH OF YBCO THIN FILMS ON TiN(001) AND CeO2-COATED TiN SURFACES (POSTPRINT) Paul N. Barnes, Rand Biggers...GROWTH OF YBCO THIN FILMS ON TiN(001) AND CeO2-COATED TiN SURFACES (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM...Number: ASC-01-1691; Clearance Date: 19 Nov 2002. This paper contains color 14. ABSTRACT Epitaxial growth of YBa2Cu3O7-x ( YBCO ) layers on TiN(0 0

  5. Effect of Y2O3, CeO2 on Sintering Properties of Si3N4 Ceramics

    Institute of Scientific and Technical Information of China (English)

    苏盛彪; 包亦望; 王黎; 李竟先

    2003-01-01

    The effect of rare earth oxides Y2O3 or CeO2 on sintering properties of Si3N4 ceramics was studied and the mechanism of assisting action during sintering was analyzed. The results indicate that the best sintering properties appear in Si3N4 ceramics with 5% Y2O3 or 8% CeO2. Secondary crystallites are formed at grain boundaries after heat treatment, which decreases the amount of glass phase and contributes to the improvement of high-temperature mechanical properties of silicon nitride.

  6. Study on CexLa1-xO2 Buffer Layer used in Coated Conductors by Chemical Solution Method

    DEFF Research Database (Denmark)

    Zhao, Yue; Suo, Hongli; Grivel, Jean-Claude

    2009-01-01

    Developing multi-functional single buffer layer is one of the most important challenges for simplification of coated conductors configuration. Ladoped CeO2 films were prepared by chemical solution method. And surface morphology and texture quality of the La-doped CeO2 films were investigated...... method. It suggects that Ce0.9La0.1O2 film prepared by chemical solution route have a promising prospect for the simplification of coated conductors configuration....... in details. The results show that the as-obtained pore-free Ce0.9La0.1O2 film are epitaxially deposited on the textured NiW substrate. The 120nm thickness Ce0.9La0.1O2 film is obtained though multi-coating route. The YBCO film with Tco=90.5K, which is deposited on Ce0.9La0.1O2/NiW metallic template by PLD...

  7. CeO2 nanocrystallines ensemble-on-nitrogen-doped graphene nanocomposites: one-pot, rapid synthesis and excellent electrocatalytic activity for enzymatic biosensing.

    Science.gov (United States)

    Du, Xiaojiao; Jiang, Ding; Chen, Saibo; Dai, Liming; Zhou, Lei; Hao, Nan; You, Tianyou; Mao, Hanping; Wang, Kun

    2017-03-15

    Ceria nanomaterials for heterogeneous catalysis have attracted much attention due to their excellent properties and have been extensively applied in recent years. But the poor electron conductivity and the aggregation behavior severely affect their electrocatalytic performances. In this paper, we prepared a novel catalyst based on CeO2 nanocrystallines (CeO2 NCs) ensemble-on-nitrogen-doped graphene (CeO2-NG) nanocomposites through a one-step heat-treatment without the need of the precursor. The results confirmed that the high dispersion of CeO2 NCs with the uniform size distribution of about 5nm on the surface of nitrogen-doped graphene (NG) sheets could be easily obtained via the one-step procedure and the resultant CeO2-NG nanocomposites were an excellent electrode material possessing outstanding electrochemical features for electron transfer. Luminol, an important electroactive substance, was further chosen to inspect the electrocatalytic properties of the as-prepared CeO2-NG nanocomposites. The studies showed that the presence of the NG in CeO2-NG nanocomposites could facilitate the electrochemical redox process of luminol. Compared with pristine CeO2 NCs, the synthesized CeO2-NG nanocomposites can enhance the electrochemiluminescence (ECL) intensity by 3.3-fold and decrease the onset ECL potential for about 72mV in the neutral condition. Employing above superiority, selecting cholesterol oxidase (ChOx) as the model oxidase, a facile ECL method for cholesterol detection with the CeO2-NG nanocomposites as the matrix to immobilize enzyme ChOx was developed. The results demonstrated CeO2-NG nanocomposites exhibited excellent performances in terms of sensitivity and catalytic activities, indicating that NG-based nanomaterials have great promise in electrocatalytic and enzymatic biosensing fields.

  8. Non-Enzymatic Glucose Biosensor Based on CuO-Decorated CeO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Panpan Guan

    2016-08-01

    Full Text Available Copper oxide (CuO-decorated cerium oxide (CeO2 nanoparticles were synthesized and used to detect glucose non-enzymatically. The morphological characteristics and structure of the nanoparticles were characterized through transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The sensor responses of electrodes to glucose were investigated via an electrochemical method. The CuO/CeO2 nanocomposite exhibited a reasonably good sensitivity of 2.77 μA mM−1cm−2, an estimated detection limit of 10 μA, and a good anti-interference ability. The sensor was also fairly stable under ambient conditions.

  9. NO reduction by CO over CuO supported on CeO2-doped TiO2: the effect of the amount of a few CeO2.

    Science.gov (United States)

    Deng, Changshun; Li, Bin; Dong, Lihui; Zhang, Feiyue; Fan, Minguang; Jin, Guangzhou; Gao, Junbin; Gao, Liwen; Zhang, Fei; Zhou, Xinpeng

    2015-06-28

    This work is mainly focused on the investigation of the influence of the amount of a few CeO2 on the physicochemical and catalytic properties of CeO2-doped TiO2 catalysts for NO reduction by a CO model reaction. The obtained samples were characterized by means of XRD, N2-physisorption (BET), LRS, UV-vis DRS, XPS, (O2, CO, and NO)-TPD, H2-TPR, in situ FT-IR, and a NO + CO model reaction. These results indicate that a small quantity of CeO2 doping into the TiO2 support will cause an obvious change in the properties of the catalyst and the TC-60 : 1 (the TiO2/CeO2 molar ratio is 60 : 1) support exhibits the most extent of lattice expansion, which indicates that the band lengths of Ce-O-Ti are longer than other TC (the solid solution of TiO2 and CeO2) samples, probably contributing to larger structural distortion and disorder, more defects and oxygen vacancies. Copper oxide species supported on TC supports are much easier to be reduced than those supported on the pure TiO2 and CeO2 surface-modified TiO2 supports. Furthermore, the Cu/TC-60 : 1 catalyst shows the highest activity and selectivity due to more oxygen vacancies, higher mobility of surface and lattice oxygen at lower temperature (which contributes to the regeneration of oxygen vacancies, and the best reducing ability), the most content of Cu(+), and the strongest synergistic effect between Ti(3+), Ce(3+) and Cu(+). On the other hand, the CeO2 doping into TiO2 promotes the formation of a Cu(+)/Cu(0) redox cycle at high temperatures, which has a crucial effect on N2O reduction. Finally, in order to further understand the nature of the catalytic performances of these samples, taking the Cu/TC-60 : 1 catalyst as an example, a possible reaction mechanism is tentatively proposed.

  10. Effects of ceria/zirconia ratio on properties of mixed CeO_2-ZrO_2-Al_2O_3 compound

    Institute of Scientific and Technical Information of China (English)

    李红梅; 祝清超; 李移乐; 龚茂初; 陈永东; 王健礼; 陈耀强

    2010-01-01

    A series of CexZr0.50-xAl0.50O1.75(0.05≤x≤0.45) mixed oxides with different Ce/Zr ratio were prepared by co-precipitation method and characterized by means of X-ray diffraction(XRD),Brunauer-Emmet Teller method(BET),temperature-programmed reduction(H2-TPR) and oxygen pulsing technique.The XRD results showed that all samples kept the single CeO2 cubic fluorite structure after calcination at 600 and 1000 oC for 5 h.The results of BET revealed that CexZr0.50-xAl0.50O1.75 with Ce/Zr molar ratio 1/1 exhibited hi...

  11. Catalytic wet air oxidation of phenol over CeO2-TiO2 catalyst in the batch reactor and the packed-bed reactor.

    Science.gov (United States)

    Yang, Shaoxia; Zhu, Wanpeng; Wang, Jianbing; Chen, Zhengxiong

    2008-05-30

    CeO2-TiO2 catalysts are prepared by coprecipitation method, and the activity and stability in the catalytic wet air oxidation (CWAO) of phenol are investigated in a batch reactor and packed-bed reactor. CeO2-TiO2 mixed oxides show the higher activity than pure CeO2 and TiO2, and CeO2-TiO2 1/1 catalyst displays the highest activity in the CWAO of phenol. In a batch reactor, COD and TOC removals are about 100% and 77% after 120 min in the CWAO of phenol over CeO2-TiO2 1/1 catalyst at reaction temperature of 150 degrees C, the total pressure of 3 MPa, phenol concentration of 1000 mg/L, and catalyst dosage of 4 g/L. In a packed-bed reactor using CeO2-TiO2 1/1 particle catalyst, over 91% COD and 80% TOC removals are obtained at the reaction temperature of 140 degrees C, the air total pressure of 3.5 MPa, the phenol concentration of 1000 mg/L for 100 h continue reaction. Leaching of metal ions of CeO2-TiO2 1/1 particle catalyst is very low during the continuous reaction. CeO2-TiO2 1/1 catalyst exhibits the excellent activity and stability in the CWAO of phenol.

  12. Co3O4-CeO2/C as a Highly Active Electrocatalyst for Oxygen Reduction Reaction in Al-Air Batteries.

    Science.gov (United States)

    Liu, Kun; Huang, Xiaobing; Wang, Haiyan; Li, Fuzhi; Tang, Yougen; Li, Jingsha; Shao, Minhua

    2016-12-21

    Developing high-performance and low-cost electrocatalysts for oxygen reduction reaction (ORR) is still a great challenge for Al-air batteries. Herein, CeO2, a unique ORR promoter, was incorporated into ketjenblack (KB) supported Co3O4 catalyst. We developed a facile two-step hydrothermal approach to fabricate Co3O4-CeO2/KB as a high-performance ORR catalyst for Al-air batteries. The ORR activity of Co3O4/KB was significantly increased by mixing with CeO2 nanoparticles. In addition, the Co3O4-CeO2/KB showed a better electrocatalytic performance and stability than 20 wt % Pt/C in alkaline electrolytes, making it a good candidate for highly active ORR catalysts. Co3O4-CeO2/KB favored a four-electron pathway in ORR due to the synergistic interactions between CeO2 and Co3O4. In full cell tests, the Co3O4-CeO2/KB exhibited a higher discharge voltage plateau than CeO2/KB and Co3O4/KB when used in cathode in Al-air batteries.

  13. Direct synthesis of dimethyl carbonate from methanol and carbon dioxide over CeO2(X)-ZnO(1-X) nano-catalysts.

    Science.gov (United States)

    Kang, Ki Hyuk; Joe, Wangrae; Lee, Chang Hoon; Kim, Mieock; Kim, Dong Baek; Jang, Boknam; Song, In Kyu

    2013-12-01

    CeO2(X)-ZnO(1-X) (X = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0) nano-catalysts were prepared by a co-precipitation method with a variation of CeO2 content (X, mol%), and they were applied to the direct synthesis of dimethyl carbonate from methanol and carbon dioxide. Successful formation of CeO2(X)-ZnO(1-X) nano-catalysts was well confirmed by XRD analysis. The amount of DMC produced over CeO2(X)-ZnO(1-X) catalysts exhibited a volcano-shaped curve with respect to CeO2 content. Acidity and basicity of CeO2(X)-ZnO(1-X) nano-catalysts were measured by NH3-TPD and CO2-TPD experiments, respectively, to elucidate the effect of acidity and basicity on the catalytic performance in the reaction. It was revealed that the catalytic performance of CeO2(X)-ZnO(1-X) nano-catalysts was closely related to the acidity and basicity of the catalysts. Amount of dimethyl carbonate increased with increasing both acidity and basicity of the catalysts. Among the catalysts tested, CeO2(0.7)-ZnO(0.3) with the largest acidity and basicity showed the best catalytic performance in the direct synthesis of dimethyl carbonate from methanol and carbon dioxide.

  14. An electrochemical DNA biosensor for evaluating the effect of mix anion in cellular fluid on the antioxidant activity of CeO2 nanoparticles.

    Science.gov (United States)

    Zhai, Yanwu; Zhang, Yan; Qin, Fei; Yao, Xin

    2015-08-15

    CeO2 nanoparticles are of particular interest as a novel antioxidant for scavenging free radicals. However, some studies showed that they could cause cell damage or death by generating reactive oxygen species (ROS). Up to now, it is not well understood about these paradoxical phenomena. Therefore, many attentions have been paid to the factors that could affect the antioxidant activity of CeO2 nanoparticles. CeO2 nanoparticles would inevitably encounter body fluid environment for its potential medical application. In this work the antioxidant activity behavior of CeO2 nanoparticles is studied in simulated cellular fluid, which contains main body anions (HPO4(2-), HCO3(-), Cl(-) and SO4(2-)), by a method of electrochemical DNA biosensor. We found that in the solution of Cl(-) and SO4(2-), CeO2 nanoparticles can protect DNA from damage by hydroxyl radicals, while in the presence of HPO4(2-) and HCO3(-), CeO2 nanoparticles lose the antioxidant activity. This can be explained by the cerium phosphate and cerium carbonate formed on the surface of the nanoparticles, which interfere with the redox cycling between Ce(3+) and Ce(4+). These results not only add basic knowledge to the antioxidant activity of CeO2 nanoparticles under different situations, but also pave the way for practical applications of nanoceria. Moreover, it also shows electrochemical DNA biosensor is an effective method to explore the antioxidant activity of CeO2 nanoparticles.

  15. Silver nanoparticles supported on CeO2-SBA-15 by microwave irradiation possess metal-support interactions and enhanced catalytic activity.

    Science.gov (United States)

    Qian, Xufang; Kuwahara, Yasutaka; Mori, Kohsuke; Yamashita, Hiromi

    2014-11-24

    Metal-support interactions (MSIs) and particle size play important roles in catalytic reactions. For the first time, silver nanoparticles supported on CeO2-SBA-15 supports are reported that possess tunable particle size and MSIs, as prepared by microwave (MW) irradiation, owing to strong charge polarization of CeO2 clusters (i.e., MW absorption). Characterizations, including TEM, X-ray photoelectron spectroscopy, and extended X-ray absorption fine structure, were carried out to disclose the influence of CeO2 contents on the Ag particle size, MSI effect between Ag nanoparticles and CeO2-SBA-15 supports, and the strong MW absorption of CeO2 clusters that contribute to the MSIs during Ag deposition. The Ag particle sizes were controllably tuned from 1.9 to 3.9 nm by changing the loading amounts of CeO2 from 0.5 to 2.0 wt%. The Ag nanoparticle size was predominantly responsible for the high turnover frequency (TOF) of 0.41 min(-1) in ammonia borane dehydrogenation, whereas both particle size and MSIs contributed to the high TOF of 555 min(-1) in 4-nitrophenol reduction for Ag/0.5CeO2-SBA-15, which were twice as large as those of Ag/SBA-15 without CeO2 and Ag/CeO2-SBA-15 prepared by conventional oil-bath heating.

  16. Biochemical effects of six TiO2 and four CeO2 nanomaterials in HepG2 cells

    Science.gov (United States)

    Biochemical effects of six TiO2 and four CeO2 nanomaterials in HepG2 cellsBecause of their growing number of uses, nanoparticles composed of CeO2 (cosmetics, polishing materials and automotive fuel additives) and TiO2 (pigments, sunscreens and photocatalysts) are of particular to...

  17. The interaction of carbon monoxide with rhodium on potassium-modified CeO2(111)

    Science.gov (United States)

    Mullins, David R.

    2016-10-01

    The adsorption and reactions of CO adsorbed on Rh particles deposited on K-covered CeO2(111) were studied by temperature programmed desorption and photoelectron spectroscopy. K deposited on CeO2(111) forms a KOX over-layer by extracting O from the ceria and partially reducing some of the Ce4 + to Ce3 +. CO does not adsorb on the KOX/ CeO2 - X(111) surface in the absence of Rh particles. CO adsorbed on Rh/K/CeO2(111) adsorbs molecularly on the Rh at 200 K. As the surface is heated the CO spills-over and reacts with the KOX to form carbonate. The carbonate decomposes at elevated temperature to produce CO and CO2. The carbonate stabilizes the KOX so that K desorbs at a higher temperature than it would in the absence of CO. When the Rh and K deposition are reversed so that K is deposited on both the Rh and the CeO2(111), CO adsorbs as CO2- at 200 K. The CO2- decomposes below 350 K to produce gas phase CO and adsorbed CO32 - and CO. The CO is stabilized by the K on the Rh and desorbs above 540 K. The carbonate decomposes into gas phase CO and CO2.

  18. The synthesis of CeO2 nanospheres with different hollowness and size induced by copper doping

    Science.gov (United States)

    Liu, Wei; Liu, Xiufang; Feng, Lijun; Guo, Jinxin; Xie, Anran; Wang, Shuping; Zhang, Jingcai; Yang, Yanzhao

    2014-08-01

    In this paper, copper-doped ceria oxides with different hollowness and size are fabricated by changing the Cu2+ doping concentration in the mixed water-glycol system. Results show that the copper-doped CeO2 oxides undergo a morphology transformation from the solid nanospheres to core-shell, then to hollow nanospheres with the increase of the Cu2+ doping concentration. The corresponding size becomes smaller during this transfer process. The Cu2+ doping induced acceleration in the nucleation and growth process is further investigated. The resultant Cu2+-doped CeO2 oxides exhibit enhanced CO conversion performance and better reduction behaviors.In this paper, copper-doped ceria oxides with different hollowness and size are fabricated by changing the Cu2+ doping concentration in the mixed water-glycol system. Results show that the copper-doped CeO2 oxides undergo a morphology transformation from the solid nanospheres to core-shell, then to hollow nanospheres with the increase of the Cu2+ doping concentration. The corresponding size becomes smaller during this transfer process. The Cu2+ doping induced acceleration in the nucleation and growth process is further investigated. The resultant Cu2+-doped CeO2 oxides exhibit enhanced CO conversion performance and better reduction behaviors. Electronic supplementary information (ESI) available: Fig. S1 the TEM images of the Cu2+-doped CeO2 (a-c): P2, P5 and P6; Fig. S2 EDS spectrum of the Cu2+-doped ceria sample; Fig. S3 the HRTEM images about lattice fringes of the Cu2+-doped CeO2: (a and b) P3; (c and d) P4; Fig. S4 the corresponding XPS survey spectrum of nanospheres: P1 and P4; Fig. S5 XRD pattern of P3 obtained at different solvothermal time, illustrated as (a) 1 h, (b) 2 h, (c) 4 h and (d) 8 h; Fig. S6 the TEM images of (a) the P1 sample at 36 h and (b) the P4 sample at 2 h; Fig. S7 N2 adsorption-desorption isotherms of the pure and Cu2+ doped CeO2: (a) P1, (b) P2, (c) P3, (d) P4, (e) P5 and (f) P6. Insets are the corresponding BJH pore-size distribution curves. See DOI: 10.1039/c4nr02485k

  19. The Effect of CeO2 Addition on the Microstructure and Properties of Ni-Based Flame-Spray Coatings

    Science.gov (United States)

    Zhang, Zhenyu; Liang, Bunv; Guo, Hongjian

    2014-04-01

    Ni-based alloy with different amount of CeO2 powders were flame sprayed and melted onto 1045 carbon steel substrate. Microstructure and properties of the coatings were studied by XRD, field emission gun scanning electron microscope (FEGSEM) and SEM analyses. The wear behavior of the coatings was investigated under dry sliding wear conditions, and was compared with that of the coatings without CeO2, The results show that the microstructure of the coating with CeO2 differs widely from the coating without CeO2, the novel microstructure is beneficial for wear resistance. Abrasive wear tests without lubricant and analysis of the worn surfaces revealed that the Ni-based alloy coatings with the addition of 0.8% CeO2 exhibit higher wear resistance.

  20. Pulsed Laser Deposition of YBCO With Yttrium Oxide Buffer Layers (Postprint)

    Science.gov (United States)

    2012-02-01

    AFRL-RZ-WP-TP-2012-0092 PULSED LASER DEPOSITION OF YBCO WITH YTTRIUM OXIDE BUFFER LAYERS (POSTPRINT) Paul N. Barnes, Timothy J. Haugan...Paper Postprint 01 January 2002 – 01 January 2004 4. TITLE AND SUBTITLE PULSED LASER DEPOSITION OF YBCO WITH YTTRIUM OXIDE BUFFER LAYERS (POSTPRINT...Textured metallic substrate based HTS coated conductors with the YBCO /CeO2/YSZ/CeO2/Ni architecture have already been shown to exhibit high current

  1. The role of hydrogenated amorphous silicon oxide buffer layer on improving the performance of hydrogenated amorphous silicon germanium single-junction solar cells

    Science.gov (United States)

    Sritharathikhun, Jaran; Inthisang, Sorapong; Krajangsang, Taweewat; Krudtad, Patipan; Jaroensathainchok, Suttinan; Hongsingtong, Aswin; Limmanee, Amornrat; Sriprapha, Kobsak

    2016-12-01

    Hydrogenated amorphous silicon oxide (a-Si1-xOx:H) film was used as a buffer layer at the p-layer (μc-Si1-xOx:H)/i-layer (a-Si1-xGex:H) interface for a narrow band gap hydrogenated amorphous silicon germanium (a-Si1-xGex:H) single-junction solar cell. The a-Si1-xOx:H film was deposited by plasma enhanced chemical vapor deposition (PECVD) at 40 MHz in a same processing chamber as depositing the p-type layer. An optimization of the thickness of the a-Si1-xOx:H buffer layer and the CO2/SiH4 ratio was performed in the fabrication of the a-Si1-xGex:H single junction solar cells. By using the wide band gap a-Si1-xOx:H buffer layer with optimum thickness and CO2/SiH4 ratio, the solar cells showed an improvement in the open-circuit voltage (Voc), fill factor (FF), and short circuit current density (Jsc), compared with the solar cells fabricated using the conventional a-Si:H buffer layer. The experimental results indicated the excellent potential of the wide-gap a-Si1-xOx:H buffer layers for narrow band gap a-Si1-xGex:H single junction solar cells.

  2. Analysis of oxidation characteristics on combustion of diesel fuels with CeO2 nano-catalyst particulates%CeO2纳米颗粒催化柴油燃烧氧化特性分析

    Institute of Scientific and Technical Information of China (English)

    孟建; 刘军恒; 孙平; 冯浩杰

    2016-01-01

    Diesel particle emission is a major resource of particulate matter 2.5 (PM2.5) and is harmful to human health. Diesel particulate filter (DPF) is a principal method to reduce diesel PM emission. The DPF requires periodical regeneration by oxidizing the particulates deposited in filters to prevent plugging. The exhaust gas temperature of the diesel engine is considerably lower than the ignition temperature of diesel particulates. Adding a nano-catalyst directly to the fuel to lower the ignition temperature of the diesel particulates is a good method. CeO2 nano-catalyst is proved to oxide the soot with high catalytic activity and stability, and is considered as a promising catalyst for application in DPF. The influence of CeO2 nano-catalyst added in diesel oil on the oxidation and structure characteristics of diesel particulates was studied using thermogravimetric analysis (TGA) and scanning electron microscope (SEM) in this article. Three kinds of CeO2 nano-catalyst fuels were confected, in which CeO2mass fractions were 0, 50 and 100 mg/kg (F0, F50 and F100), respectively. The micro-orifice uniform deposition impactor (MOUDI) was used to collect the particulates generated by burning P0, P50 and P100. The SEM was used to study the influence of CeO2 mass fraction on the particle morphology characteristics. The effects of heating rates and CeO2 mass fraction on particle thermal oxidation characteristics were studied by thermogravimetric analysis method. The activation energy of particulates was calculated with Coast-Redfern integrate method. The results show that there were obvious clusters morphology of particulates from diesel engine fueled with the three CeO2 nano-catalyst fuels, and the particle distribution sizes were mainly concentrated between 20 nm and 70 nm, which were single peak curves. With the increase of CeO2 mass fraction, the particle sizes of P0, P50 and P100, the mean diameter of particulates decreased and the box dimension increased, accordingly. The

  3. Novel CeO2-CuO-decorated enzymatic lactate biosensors operating in low oxygen environments.

    Science.gov (United States)

    Uzunoglu, Aytekin; Stanciu, Lia A

    2016-02-25

    The detection of the lactate level in blood plays a key role in diagnosis of some pathological conditions including cardiogenic or endotoxic shocks, respiratory failure, liver disease, systemic disorders, renal failure, and tissue hypoxia. Here, we described for the first time the use of a novel mixed metal oxide solution system to address the oxygen dependence challenge of first generation amperometric lactate biosensors. The biosensors were constructed using ceria-copper oxide (CeO2-CuO) mixed metal oxide nanoparticles for lactate oxidase immobilization and as electrode material. The oxygen storage capacity (OSC, 492 μmol-O2/g) of these metal oxides has the potential to reduce the oxygen dependency, and thus eliminate false results originated from the fluctuations in the oxygen concentration. In an effort to compare the performance of our novel sensor design, ceria nanoparticle decorated lactate sensors were also constructed. The enzymatic activity of the sensors were tested in oxygen-rich and oxygen-lean solutions. Our results showed that the OSC of the electrode material has a big influence on the activity of the biosensors in oxygen-lean environments. While the CeO2 containing biosensor showed an almost 21% decrease in the sensitivity in a O2-depleted solution, the CeO2-CuO containing electrode, with a higher OSC value, experienced no drop in sensitivity when moving from oxygen-rich to oxygen-lean conditions. The CeO2-CuO decorated sensor showed a high sensitivity (89.3 ± 4 μA mM(-1) cm(-2)), a wide linear range up to 0.6 mM, and a low limit of detection of 3.3 μM. The analytical response of the CeO2-CuO decorated sensors was studied by detecting lactate in human serum with good selectivity and reliability. The results revealed that CeO2-CuO containing sensors are promising candidates for continuous lactate detection.

  4. Biogenic synthesis and catalysis of porous CeO2 hollow microspheres

    Institute of Scientific and Technical Information of China (English)

    CHEN Feng; WANG Wei; CHEN Zhigang; WANG Taibin

    2012-01-01

    Porous CeO2 hollow microspheres were successfully prepared through a facile process by using the rape pollen as the biotemplate.Scanning electron microscopy (SEM),transmission electron microscopy (TEM),the N2 adsorption and desorption,X-ray diffraction (XRD),UV-vis diffuse reflectance spectra,and hydrogen temperature-programmed reduction (H2-TPR) were used for their characterization.The results showed that the obtained materials exhibited the same morphology as that of the pollen template,with a diameter of ca.10 μm,and the surface was evenly covered with a special network-like structure with mesh size of about 0.3 μm,and the Brunauer-Emmett-Teller (BET) surface area was measured to be 156 m2/g.The detailed property investigation inferred that the product exhibited better photocatalytic activity in acid fuchsine decolorization under daylight because of higher surface area,smaller crystallite size and higher oxygen capacity.

  5. Influence of nanometric CeO2 coating on high temperature oxidation of Cr

    Institute of Scientific and Technical Information of China (English)

    Jin Huiming; Zhang Linnan; Liu Xiaojun

    2007-01-01

    Isothermal and cyclic oxidation behavior of chromium and its superficially applied nanometric CeO2 samples were studied at 900℃ in air. Scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and high resolution electronic microscopy (HREM) were used to examine the morphology and micro-structure of oxide films. It was found that ceria addition greatly improved the anti-oxidation ability of Cr both in isothermal and cyclic oxidizing experiments. Acoustic emission (AE) technique was used in situ to monitor the cracking and spalling of oxide films, and AE signals were analyzed in time-domain and number-domain according to the related oxide fracture model. Laser Raman spectrometer was also used to study the stress status of oxide films formed on Cr with and without ceria. The main reason for the improvement in anti-oxidation of chromium was that ceria greatly reduced the growing speed and grain size of Cr2O3. This fine-grained Cr2O3 oxide film might have better high temperature plasticity and could relieve parts of compressive stress by means of creeping, and maintained the ridge character and relatively low internal stress level. Meanwhile, ceria application reduced the size and the number of interfacial defects, while remarkably enhanced the adhesive property of Cr2O3 oxide scale formed on Cr substrate.

  6. Configurational affects on the compaction response of CeO2 powders

    Directory of Open Access Journals (Sweden)

    Dattelbaum D.

    2012-08-01

    Full Text Available Initial configuration, which can include particle size and shape, initial density, and void location, can affect the measured compaction responses of initially porous materials. In this work, both the low- and high-strain-rate compaction response of several different morphology CeO2 powders are investigated experimentally. Quasi-static compaction curves are found to exhibit distinct differences between the morphologies, where initial packing efficiencies and particle aspect ratios are found to dominate the low pressure response. At low-strain-rates, the largest particles with the highest aspect ratio are found to exhibit the stiffest response, while those that most resemble spherical particles offer the least resistance to initial densification. At high-strain-rates a transition in compliance is observed, where smaller equiaxed particles are found to exhibit greater resistances to densification. The role of particle morphology and its affect on the communication of particle-level stresses during quasi-static and dynamic densification are discussed, and emphasis is placed on the mechanisms that cause the morphology-based transition in compliance.

  7. Diffusion Barriers Block Defect Occupation on Reduced CeO2(111 )

    Science.gov (United States)

    Lustemberg, P. G.; Pan, Y.; Shaw, B.-J.; Grinter, D.; Pang, Chi; Thornton, G.; Pérez, Rubén; Ganduglia-Pirovano, M. V.; Nilius, N.

    2016-06-01

    Surface defects are believed to govern the adsorption behavior of reducible oxides. We challenge this perception on the basis of a combined scanning-tunneling-microscopy and density-functional-theory study, addressing the Au adsorption on reduced CeO2 -x(111 ) . Despite a clear thermodynamic preference for oxygen vacancies, individual Au atoms were found to bind mostly to regular surface sites. Even at an elevated temperature, aggregation at step edges and not decoration of defects turned out to be the main consequence of adatom diffusion. Our findings are explained with the polaronic nature of the Au-ceria system, which imprints a strong diabatic character onto the diffusive motion of adatoms. Diabatic barriers are generally higher than those in the adiabatic regime, especially if the hopping step couples to an electron transfer into the ad-gold. As the population of O vacancies always requires a charge exchange, defect decoration by Au atoms becomes kinetically hindered. Our study demonstrates that polaronic effects determine not only electron transport in reducible oxides but also the adsorption characteristics and therewith the surface chemistry.

  8. Methanol decomposition on low index and stepped CeO2 surfaces from GGA+U

    Science.gov (United States)

    Reimers, Walter G.; Branda, María M.

    2017-02-01

    GGA + U calculations have been carried out to study the complete methanol decomposition on the more stable Ceria surfaces, i.e. (111), (221), (331) and (110). These results have shown that the methanol adsorption is exothermic on oxidized as well as on the partially reduced surfaces though the adsorption energy is greater for the latest. The first dehydrogenation step of methanol is highly probable for all the studied sites with activation barriers smaller than 0.2 eV. The first dehydrogenation reaction could also occur by breaking the Csbnd H methyl bond, but we found that this reaction is very unlikely. Reaction and activation energies for the second dehydrogenation - from methoxy to formaldehyde, are very similar for perfect (111) and stepped surfaces but these activation barriers are not negligible, almost ten times as many the first step barriers. Next, the formaldehyde decomposition to formyl and CO species on perfect CeO2(111) have an important energetic cost, therefore these reactions could occur only on stepped surfaces.

  9. Optical properties of CeO2/Fe3O4 solar control glass coating

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hongsheng; LIU Bing; HU Hongpo; LI Ziqiang; SHAO Youlin

    2006-01-01

    A cerium-iron oxide solar control coating on glass was prepared by citric acid sol-gel method, dip-coating techniques and proper heat treatment process. Results show that the cerium-iron glass coating is composed of nanocrystalline CeO2, Fe2O3, and nano holes. The cerium-iron glass coating has high transmittance in visible light, low UV and near IR transmittance. The wavelength of absorption edge for most glass coating has an obvious redshift to about 375 nm. There exist a wide absorption band at the range of 800-1600 nm and high transmittance at the wavelength from 400 nm to 800 nm, and the solar energy and visible transmittances are 50% and 65%, respectively. It ascribes to the high content of trivalence cerium and bivalence iron ions in the cerium/iron coating. It is indicated that this kind of glass coating has very good UV-sheering and heat-insulating property, can be used as an effective solar control glass in automobile and architecture.

  10. Synthesis and characterization of manganese doped CeO2 nanopowders from hydrolysis and oxidation of Ce37Mn18C45

    Institute of Scientific and Technical Information of China (English)

    DU Yanan; NI Jiansen; HU Pengfei; WANG Jun'an; HOU Xueling; XU Hui

    2013-01-01

    The Mn-doped CeO2 nanopowders with high catalysis activity were successfully fabricated through a simple hydrolyzed-oxidized approach.Firstly,the alloy Ce37Mn18C45 was prepared in vacuum induction melting furnace.Subsequently,Mn-doped CeO2 nanopowders with 142 m2/g of specific surface area were obtained through a simple hydrolyzed-oxidized procedure of the alloy.Those nanopowders were heat treated at different temperatures.The obtained materials were characterized by X-ray diffraction (XRD),transmission electron microscopy (TEM),high-resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS).And the catalytic activity on vinyl chloride (VC) emission combustion was investigated.The results showed that those nanopowders after hydrolyzed-oxidized from Ce37Mn1sC45 mainly consisted of CeO2 and Mn3O4.Manganese element increased the thermal stability of CeO2 nanopowders.The Mn-doped CeO2 nanopowders had three morphologies.Small particles were Mn-doped CeO2,square particles were Mn3O4 and the rods were Mn3O4 and Mn2O3.The Mn-doped CeO2 nanopowders had good vinyl chloride (VC) emission catalytic performance.

  11. Citric acid modifies surface properties of commercial CeO2 nanoparticles reducing their toxicity and cerium uptake in radish (Raphanus sativus) seedlings.

    Science.gov (United States)

    Trujillo-Reyes, J; Vilchis-Nestor, A R; Majumdar, S; Peralta-Videa, J R; Gardea-Torresdey, J L

    2013-12-15

    Little is known about the mobility, reactivity, and toxicity to plants of coated engineered nanoparticles (ENPs). Surface modification may change the interaction of ENPs with living organisms. This report describes surface changes in commercial CeO2 NPs coated with citric acid (CA) at molar ratios of 1:2, 1:3, 1:7, and 1:10 CeO2:CA, and their effects on radish (Raphanus sativus) seed germination, cerium and nutrients uptake. All CeO2 NPs and their absorption by radish plants were characterized by TEM, DLS, and ICP-OES. Radish seeds were germinated in pristine and CA coated CeO2 NPs suspensions at 50mg/L, 100mg/L, and 200mg/L. Deionized water and CA at 100mg/L were used as controls. Results showed ζ potential values of 21.6 mV and -56 mV for the pristine and CA coated CeO2 NPs, respectively. TEM images showed denser layers surrounding the CeO2 NPs at higher CA concentrations, as well as better distribution and smaller particle sizes. None of the treatments affected seed germination. However, at 200mg/L the CA coated NPs at 1:7 ratio produced significantly (p ≤ 0.05) more root biomass, increased water content and reduced by 94% the Ce uptake, compared to bare NPs. This suggests that CA coating decrease CeO2 NPs toxicity to plants.

  12. Thermally Stable Hierarchical Nanostructures of Ultrathin MoS2 Nanosheet-Coated CeO2 Hollow Spheres as Catalyst for Ammonia Decomposition.

    Science.gov (United States)

    Gong, Xueyun; Gu, Ying-Qiu; Li, Na; Zhao, Hongyang; Jia, Chun-Jiang; Du, Yaping

    2016-04-18

    MoS2 ultrathin nanosheet-coated CeO2 hollow sphere (CeO2@MoS2) hybrid nanostructures with a 3D hierarchical configuration were successfully constructed from a facile two-step wet chemistry strategy: first, CeO2 formed on a silica core which served as a template and was subsequently removed by NaOH solution to attain hollow spheres, and then few-layered ultrathin MoS2 nanosheets were deposited on the CeO2 hollow spheres through a hydrothermal process. As a proof of concept application, the as-prepared CeO2@MoS2 hybrid nanostructures were used as catalytic material, which exhibited enhanced catalytic activity in ammonia decomposition for H2 production at high temperature. It was demonstrated that, even with a structural transformation from MoS2 to MoNx under harsh conditions of ammonia decomposition at high temperature (700 °C), the 3D hierarchical nanostructures of the CeO2@MoNx were well kept, indicating the important role of the CeO2 support.

  13. Baize-like CeO2 and NiO/CeO2 nanorod catalysts prepared by dealloying for CO oxidation

    Science.gov (United States)

    Zhang, Xiaolong; Li, Kun; Shi, Wenyu; Wei, Caihua; Song, Xiaoping; Yang, Sen; Sun, Zhanbo

    2017-01-01

    Baize-like monolithic CeO2 and NiO/CeO2 nanorod catalysts were prepared by combined dealloying and calcination and the catalytic activities were evaluated using CO catalytic oxidation. The CeO2 catalysts were composed of nanorods and exhibited a three-dimensional supporting structure with pores. After introduction of NiO, dispersed NiO nanosheets and nanoparticles were supported on the surface of CeO2 nanorods and they were not well-crystallined due to CeO2 inhibiting the NiO crystallization. The Raman and x-ray photoelectron spectroscopy analyses revealed that the introduction of NiO species into CeO2 generated more coordinate unsaturated Ni atoms, oxygen vacancies, defects and active sites for CO catalytic reactions. The reaction activation energy of NiO/CeO2 nanorod catalyst prepared from the Al83Ce10Ni7 precursor alloy was just 31.2 kJ mol-1 and the CO conversion can reach up to 97% at 240 °C, which was superior to that of pure CeO2 and nanoporous NiO. The enhanced catalytic activity of baize-like NiO/CeO2 nanorods can be attributed to the strong synergistic effects between finely dispersed NiO species and surface oxygen vacancies in CeO2 nanorods.

  14. Identification of the arsenic resistance on MoO3 doped CeO2/TiO2 catalyst for selective catalytic reduction of NOx with ammonia.

    Science.gov (United States)

    Li, Xiang; Li, Xiansheng; Li, Junhua; Hao, Jiming

    2016-11-15

    Arsenic resistance on MoO3 doped CeO2/TiO2 catalysts for selective catalytic reduction of NOx with NH3 (NH3-SCR) is investigated. It is found that the activity loss of CeO2-MoO3/TiO2 caused by As oxide is obvious less than that of CeO2/TiO2 catalysts. The fresh and poisoned catalysts are compared and analyzed using XRD, Raman, XPS, H2-TPR and in situ DRIFTS. The results manifest that the introduction of arsenic oxide to CeO2/TiO2 catalyst not only weakens BET surface area, surface acid sites and adsorbed NOx species, but also destroy the redox circle of Ce(4+) to Ce(3+) because of interaction between Ce and As. When MoO3 is added into CeO2/TiO2 system, the main SCR reaction path are found to be changed from the reaction between coordinated NH3 and ad-NOx species to that between an amide and gaseous NO. Additionally, for CeO2-MoO3/TiO2 catalyst, As toxic effect on active sites CeO2 can be released because of stronger As-Mo interaction. Moreover, not only are the reactable Brønsted and Lewis acid sites partly restored, but the cycle of Ce(4+) to Ce(3+) can also be free to some extent.

  15. Exceptional capability of nanosized CeO(2) materials to "dissolve" lanthanide oxides established by time-gated excitation and emission spectroscopy.

    Science.gov (United States)

    Tiseanu, Carmen; Parvulescu, Vasile; Avram, Daniel; Cojocaru, Bogdan; Sanchez-Dominguez, Margarita

    2014-05-28

    The atomic scale homogeneity of Ce and Zr oxygen bonds represents the main reason for enhanced total oxygen storage capability of CeO2-ZrO2 (Ce/Zr = 1) as compared to that of CeO2. Here, we demonstrate that the addition of 10% Eu(3+) by wet impregnation on preformed nanosized CeO2-ZrO2 (Ce/Zr = 1) followed by calcination induces a remarkable homogeneity of 10% Eu(3+)-CeO2-ZrO2 solid solution. By use of time-resolved emission and excitation spectroscopies, the improvement of the nanoscale chemical and structural homogeneity of 10% Eu(3+)-CeO2-ZrO2 calcined at 1000 as compared to sample calcined at 750 °C is demonstrated. Based on the comparison of luminescence properties of 10% Eu(3+) impregnated on preformed nanosized CeO2-ZrO2 and CeO2, we also show that the presence of zirconium does not only preserve the ability of cerium oxide to "dissolve" lanthanide oxide, but also determines an important stabilization of defects (oxygen vacancies) generated upon Eu(3+) doping.

  16. Effects of CeO2 Coating on Oxidation Behavior of TP304H Steel in High-temperature Water Vapor

    Institute of Scientific and Technical Information of China (English)

    Li Xingeng; Wang Xuegang; He Jiawen

    2005-01-01

    Oxidation behaviors of TP304H steel with electrophoresis deposited CeO2 coating in water vapor were studied at 610℃~770℃ for 65 h. The results showed that CeO2 coating reduced effectively the oxidation rate of TP304H. Analysis with SEM and EDS showed the structure of oxide scale turned from multi-layer to mono-layer and oxide scale with high Cr content formed on the surface of CeO2 coating while inner oxidation disappeared. Based on test results and CeO2characters that Ce ion can vary between Ce4+ and Ce3+ under oxygen-rich and oxygen-poor environment, it is concluded that CeO2 coating acts as a barrier to prevent oxygen inner diffusion and the partial oxygen pressure of CeO2 coating-substrate interface is limited. Cr first diffuses outward across CeO2 coating and forms oxide scale on the surface, which delays formation of Fe oxide.

  17. Hydrogen production from methane steam reforming over Ni on high surface area CeO2 and CeO2-ZrO supports synthesized by surfactant-assisted method

    Directory of Open Access Journals (Sweden)

    Sumittra Charojrochkul

    2006-11-01

    Full Text Available Methane steam reforming performances of Ni on high surface area (HSA CeO2 and CeO2-ZrO2 supports have been studied under solid oxide fuel cell (SOFC operating conditions. Their performances were compared to general Ni/CeO2, Ni/CeO2-ZrO2, and Ni/Al2O3. It was firstly observed that Ni/CeO2-ZrO2 (HSA with the Ce/Zr ratio of 3/1 showed the best performance in terms of activity and stability toward the methane steam reforming among those with the Ce/Zr ratios of 1/1, 1/3, and 3/1. Both Ni/CeO2-ZrO2 (HSA and Ni/CeO2 (HSA presented better resistance toward carbon formation than the general Ni/CeO2, Ni/CeO2- ZrO2, and Ni/Al2O3 at the same operating conditions. These benefits are related to the high oxygen storage capacity (OSC of CeO2-ZrO2. During the steam reforming process, in addition to the reactions on Ni surface (*, the redox reactions between the gaseous components presented in the system and the lattice oxygen (Ox on CeO2-ZrO2 surface also take place. Among these reactions, the redox reactions between the high carbon formation potential compounds (CH4, CHx-*n and CO and the lattice oxygen (Ox can prevent the formation of carbon species from the methane decomposition and Boudard reactions at the inlet H2O/CH4 ratio of 3.0/1.0.

  18. Research on Sb2O3/CeO2-Doped ZnO Thin Film%Sb2O3/CeO2共掺杂ZnO薄膜的研究

    Institute of Scientific and Technical Information of China (English)

    徐芸芸; 张韬; 李争鸣; 徐新

    2011-01-01

    采用射频磁控溅射技术制备Sb2O3/CeO2共掺杂ZnO薄膜,研究了薄膜的结构及紫外光吸收性能.结果表明:Sb2O3和CeO2共同掺入ZnO薄膜后,ZnO(002)晶面的XRD衍射峰强度明显下降,ZnO薄膜呈混晶方式生长;共掺杂ZnO薄膜的紫外吸收性能明显优于纯ZnO薄膜,Sb对掺杂ZnO薄膜的结构和紫外吸收性能的影响起主导作用,Ce起进一步的强化作用.%The ZnO thin films doped with Sb2O3/CeO2 was prepared by RF magnetron sputtering technique. The results show that the Sb2O3/CeO2-doped films had an prominent effect on the developing ways of crystal grains and UV absorption property. The films' UVA absorption is enhanced. The ultraviolet absorption peak become wide and the absorption intensity increases. Sb-doped ZnO thin films on the structure and properties of UV absorption plays a dominant role,and Ce plays an enhanced role.

  19. CeO2-modified Au@SBA-15 nanocatalysts for liquid-phase selective oxidation of benzyl alcohol

    Science.gov (United States)

    Wang, Tuo; Yuan, Xiang; Li, Shuirong; Zeng, Liang; Gong, Jinlong

    2015-04-01

    Tuning the interfacial perimeter and structure is crucial to understanding the origin of catalytic performance. This paper describes the design, characterization, and application of CeO2 modified Au@SBA-15 (Au-CeO2@SBA-15) catalysts in selective oxidation of benzyl alcohol. The reaction results showed that Au-CeO2@SBA-15 catalysts exhibited higher catalytic activity compared with Au@SBA-15 and Au/CeO2 catalysts under identical conditions along with the high selectivity towards benzaldehyde (>99%). The turnover frequency of benzyl alcohol over the Au-100CeO2@SBA-15 catalyst is about nine-fold and four-fold higher than those of Au@SBA-15 and Au/CeO2 catalysts, respectively. The supported catalysts were characterized by N2 adsorption-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, scanning transmission electron microscopy-energy dispersive spectrometry, and X-ray photoelectron spectroscopy. It was found that the Au and small CeO2 nanoparticles (~5 nm) were homogeneously mixed in the channels of SBA-15, which led to an increase in the interfacial area between Au and CeO2 and consequently a better catalytic performance of Au-CeO2@SBA-15 catalysts for the selective oxidation of benzyl alcohol to benzaldehyde compared with that of Au/CeO2. The prevention of agglomeration and leaching of Au nanoparticles by restricting them inside the mesopores of SBA-15 was conducive to the stable existence of large quantities of Au-CeO2 interface, which leads to high stability of the Au-CeO2@SBA-15 catalyst.Tuning the interfacial perimeter and structure is crucial to understanding the origin of catalytic performance. This paper describes the design, characterization, and application of CeO2 modified Au@SBA-15 (Au-CeO2@SBA-15) catalysts in selective oxidation of benzyl alcohol. The reaction results showed that Au-CeO2@SBA-15 catalysts exhibited higher catalytic activity compared with Au@SBA-15 and Au/CeO2 catalysts under identical conditions along with the high selectivity towards benzaldehyde (>99%). The turnover frequency of benzyl alcohol over the Au-100CeO2@SBA-15 catalyst is about nine-fold and four-fold higher than those of Au@SBA-15 and Au/CeO2 catalysts, respectively. The supported catalysts were characterized by N2 adsorption-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, scanning transmission electron microscopy-energy dispersive spectrometry, and X-ray photoelectron spectroscopy. It was found that the Au and small CeO2 nanoparticles (~5 nm) were homogeneously mixed in the channels of SBA-15, which led to an increase in the interfacial area between Au and CeO2 and consequently a better catalytic performance of Au-CeO2@SBA-15 catalysts for the selective oxidation of benzyl alcohol to benzaldehyde compared with that of Au/CeO2. The prevention of agglomeration and leaching of Au nanoparticles by restricting them inside the mesopores of SBA-15 was conducive to the stable existence of large quantities of Au-CeO2 interface, which leads to high stability of the Au-CeO2@SBA-15 catalyst. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00246j

  20. Prediction of the Isothermal Sections in the ZrO2-YO1.5-CeO2 System

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The experimental work on the ZrO2-YO1.5-CeO2 system, its limiting quasi-binaries and previous thermodynamic assessments are reviewed and evaluated. Isothermal sections of ZrO2-YO1.5-CeO2 system in the temperature region between 1450 and 1800°C are estimated according to the substitutional model using the Bonnier equation. The CSS+YSS two-phase region of the calculated isothermal section at 1700°C was found to be in good agreement with the experimentally obtained ternary diagram of Longo and Podda. The phase composition in the ZrO2-rich corner however disagreed significantly.

  1. A new cathode using CeO2/MWNT for hydrogen peroxide synthesis through a fuel cell

    Institute of Scientific and Technical Information of China (English)

    XU Fuyuan; SONG Tianshun; XU Yuan; CHEN Yingwen; ZHU Shemin; SHEN Shubao

    2009-01-01

    Catalyst using CeO2/MWNT (multi-walled carbon nanotube) was prepared by chemical deposition method and was applied to prepare the cathode of fuel cell for hydrogen peroxide synthesis. Effect of catalyst loading, flow rate of aqueous solution, and KOH concentration on hydrogen peroxide synthesis were investigated. Experimental results indicated that hydrogen peroxide concentration approached 275 mmol/L given 25% of CeO2/MWNT, 18 ml/h of aqueous solution, and 5 mol/L of KOH concentration. Moreover, the reaction mechanism was further discussed. The results indicated that MWNT and cerium oxide were the synergism to produce hydrogen peroxide. Increase of KOH concentration not only reduced the apparent cell resistance but also increased the open-circuit voltage.

  2. Kinetic buffers.

    Science.gov (United States)

    Alibrandi, Giuseppe; Fabbrizzi, Luigi; Licchelli, Maurizio; Puglisi, Antonio

    2015-01-12

    This paper proposes a new type of molecular device that is able to act as an inverse proton sponge to slowly decrease the pH inside a reaction vessel. This makes the automatic monitoring of the concentration of pH-sensitive systems possible. The device is a composite formed of an alkyl chloride, which kinetically produces acidity, and a buffer that thermodynamically modulates the variation in pH value. Profiles of pH versus time (pH-t plots) have been generated under various experimental conditions by computer simulation, and the device has been tested by carrying out automatic spectrophotometric titrations, without using an autoburette. To underline the wide variety of possible applications, this new system has been used to realize and monitor HCl uptake by a di-copper(II) bistren complex in a single run, in a completely automatic experiment.

  3. Modified-EISA synthesis of mesoporous high surface area CeO_2 and catalytic property for CO oxidation

    Institute of Scientific and Technical Information of China (English)

    李霞章; 陈丰; 陆晓旺; 倪超英; 陈志刚

    2009-01-01

    Mesoporous CeO2 particles with high surface area were synthesized using a modified evaporation-induced self assembly(EISA) method which combined citric acid as complexing agent.As-prepared powder and further thermal treatment samples were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),selected area electron diffraction(SAED),Fourier transform infrared spectrometer(FTIR),thermogravimetry and differential thermal analysis(TG-DTA),Brunauer-Emmett-Teller(BET) and Barrett-Joyner-Ha...

  4. CeO2-modified Au@SBA-15 nanocatalysts for liquid-phase selective oxidation of benzyl alcohol.

    Science.gov (United States)

    Wang, Tuo; Yuan, Xiang; Li, Shuirong; Zeng, Liang; Gong, Jinlong

    2015-05-07

    Tuning the interfacial perimeter and structure is crucial to understanding the origin of catalytic performance. This paper describes the design, characterization, and application of CeO2 modified Au@SBA-15 (Au-CeO2@SBA-15) catalysts in selective oxidation of benzyl alcohol. The reaction results showed that Au-CeO2@SBA-15 catalysts exhibited higher catalytic activity compared with Au@SBA-15 and Au/CeO2 catalysts under identical conditions along with the high selectivity towards benzaldehyde (>99%). The turnover frequency of benzyl alcohol over the Au-100CeO2@SBA-15 catalyst is about nine-fold and four-fold higher than those of Au@SBA-15 and Au/CeO2 catalysts, respectively. The supported catalysts were characterized by N2 adsorption-desorption, inductively coupled plasma optical emission spectroscopy, X-ray diffraction, transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, scanning transmission electron microscopy-energy dispersive spectrometry, and X-ray photoelectron spectroscopy. It was found that the Au and small CeO2 nanoparticles (∼5 nm) were homogeneously mixed in the channels of SBA-15, which led to an increase in the interfacial area between Au and CeO2 and consequently a better catalytic performance of Au-CeO2@SBA-15 catalysts for the selective oxidation of benzyl alcohol to benzaldehyde compared with that of Au/CeO2. The prevention of agglomeration and leaching of Au nanoparticles by restricting them inside the mesopores of SBA-15 was conducive to the stable existence of large quantities of Au-CeO2 interface, which leads to high stability of the Au-CeO2@SBA-15 catalyst.

  5. Optimal Conditions for Preparing Ultra-Fine CeO2 Powders in A Submerged Circulative Impinging Stream Reactor

    Institute of Scientific and Technical Information of China (English)

    Chi Ru'an; Xu Zhigao; Wu Yuanxin; Wang Cunwen

    2007-01-01

    Cerium carbonate powders were produced in a submerged circulation impinging stream reactor (SCISR) from Ce(NO3)3·6H2O. NH4HCO3 was used as a precipitant in the reaction. Cerium carbonate powders were roasted to produce ultra-fine cerium dioxide (CeO2) powders. The optimal conditions of such production process were obtained by orthogonal and one-factor experiments. The results showed that ultra-fine and narrowly distributed cerium carbonate powders were produced under the optimal flowing conditions. The concentrations of Ce(NO3)3 and NH4HCO3 solutions were 0.25 and 0.3 mol·L-1, respectively. The concentration of PEG4000 added in these two solutions was 4 g·L-1. The stirring ratio, reaction temperature, feeding time, solution pH, reaction time and digestion time were 900 r·min-1, 80 ℃, 20 min, 5~6, 5 min and 1 h, respectively. The final product, CeO2 powders, was obtained by roasting the produced cerium carbonate in air for 3 h at 500 ℃. The finally produced CeO2 powders were torispherical particles with a narrow size distribution of 0.8~2.5 μm. The crystal structure of CeO2 powders belonged to cubic crystal system and its space point group was O5H-FM3M. Under optimal conditions, powders produced by SCISR were finer and more narrowly distributed than that by Stirred Tank Reactor (STR).

  6. Mechanical Properties of ZrO2 Ceramic Stabilized by Y2O3 and CeO2

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    ZrO2 ceramic was made from evenly dispersed (Y,Ce)-ZrO2 powder with different compositions,which was prepared by the chemical coprecipitation, and stabilized by compound additions through appropriate techniques.And its mechanical property that is related to the phase content and its microstructure was studied by X-ray diffraction(XRD),scan electron microscope(SEM).The results show that Y2O3 has stronger inhibition to the growth of ZrO2 crystal than CeO2 has.Therefore,within an appropriate composition range of Y2O3 and CeO2,the higher the content of Y2O3,the lower the content of CeO2,the smaller ZrO2 crystal.Combining this feature and the stabilization technique with complex additions instead of simple addition,ZrO2 ceramic with high density and excellent mechanical properties can be made under normal conditions. It is concluded that the improvement of mechanical properties originates from the toughening of microcrack,phase transformation and the effect of grain evulsions.

  7. Effects of Pretreatment Conditions on Redox Property over Au/Co3O4/CeO2 Material

    Institute of Scientific and Technical Information of China (English)

    SHAO Jian-jun; MA Xiao-lei; ZHU Xi

    2009-01-01

    Au/Co3O4/CeO2 materials are prepared using conventional deposition-precipitation method. The effects of calcination temperatures and pretreatment conditions on the catalytic performance of Au/Co3O4/CeO2 for CO low-temperature oxidation in humid circumstance are investigated. The sample calcines at 443 K in flowing air exhibited good activity and stability for CO oxidation. 80% CO conversion rate can be achieved after 3 000 min with a feed gas contained 3.1%(φw) of water vapor. The physical and chemical properties of the Au/Co3O4/CeO2 samples are characterized by X-ray diffraction (XRD), temperature-programmed reduction (H2-TPR), and transmission electron microscopy (TEM) techniques. The characterized results show that the prepared material calcined at 443 K has a weak diffraction peak of gold species observed by XRD, the grain diameter of 3 nm by TEM and best redox property and the highest activity for CO oxidation by H2-TPR at prope calcined temperature.

  8. Direct synthesis of dimethyl carbonate from CO2 and methanol over CeO2 catalysts of different morphologies

    Indian Academy of Sciences (India)

    UNNIKRISHNAN P; SRINIVAS DARBHA

    2016-06-01

    The direct synthesis of dimethyl carbonate (DMC) from carbon dioxide CO2 and methanol is an attractive approach towards conversion of the greenhouse gas - CO2 into value-added chemicals and fuels.Ceria CeO2 catalyzes this reaction. But the conversion efficiency of CeO2 is enhanced when the byproductwater in the reaction medium is separated by employing trapping agents like 2-cyanopyridine (2-CP). In thiswork, the influence of morphology of CeO2 on the direct synthesis of DMC in presence of 2-CP is reported.CeO2 catalysts of cube, rod, spindle and irregular morphology (Ce - C, Ce - R, Ce - S and Ce - N, respectively)were prepared, characterized and studied as catalysts in the said reaction conducted in a batch mode. Amongall, Ce - S shows superior catalytic performance with nearly 100 mol% of DMC selectivity. Catalytic activitycorrelates with the concentration of acid and base sites of medium strength as well as defect sites. Ce - S has anoptimum number of these active sites and thereby shows superior catalytic performance.

  9. Surface degradation of CeO2 stabilized acrylic polyurethane coated thermally treated jack pine during accelerated weathering

    Science.gov (United States)

    Saha, Sudeshna; Kocaefe, Duygu; Boluk, Yaman; Pichette, Andre

    2013-07-01

    The thermally treated wood is a new value-added product and is very important for the diversification of forestry products. It drew the attention of consumers due to its attractive dark brown color. However, it loses its color when exposed to outside environment. Therefore, development of a protective coating for this value added product is necessary. In the present study, the efficiency of CeO2 nano particles alone or in combination with lignin stabilizer and/or bark extracts in acrylic polyurethane polymer was investigated by performing an accelerated weathering test. The color measurement results after accelerated weathering demonstrated that the coating containing CeO2 nano particles was the most effective whereas visual assessment suggested the coating containing CeO2 nano particles and lignin stabilizer as the most effective coating. The surface polarity changed for all the coatings during weathering and increase in contact angle after weathering suggested cross linking and reorientation of the polymer chain during weathering. The surface chemistry altered during weathering was evaluated by ATR-FTIR analysis. It suggested formation of different carbonyl byproducts during weathering. The chain scission reactions of the urethane linkages were not found to be significant during weathering.

  10. Synthesis and characterization of molybdenum catalysts supported on γ-Al2O3-CeO2 composite oxides

    Science.gov (United States)

    Farooq, Muhammad; Ramli, Anita; Subbarao, Duvvuri

    2012-09-01

    The physical and chemical properties of a catalyst play a vital role in various industrial applications. Molybdenum catalysts supported on γ-Al2O3 and γ-Al2O3-CeO2 mixed oxides with varying loading of CeO2 (5, 10, 15, 20 wt% with respect to γ-Al2O3) were prepared by wet impregnation method. The physiochemical properties of these synthesized Mo catalysts were studied with various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX) and X-ray fluorescence spectrometer (XRF). The results showed that the addition of CeO2 into the support affected the binding energies of the elements and reducibility of the metal oxides formed after calcination of catalyst samples due to the change in metal-support interaction. Further, the characterization techniques showed that the active metal was well dispersed on the surface of support material.

  11. Ruthenium nanoparticles supported on CeO2 for catalytic permanganate oxidation of butylparaben.

    Science.gov (United States)

    Zhang, Jing; Sun, Bo; Guan, Xiaohong; Wang, Hui; Bao, Hongliang; Huang, Yuying; Qiao, Junlian; Zhou, Gongming

    2013-11-19

    This study developed a heterogeneous catalytic permanganate oxidation system with ceria supported ruthenium, Ru/CeO2 (0.8‰ as Ru), as catalyst for the first time. The catalytic performance of Ru/CeO2 toward butylparaben (BP) oxidation by permanganate was strongly dependent on its dosage, pH, permanganate concentration and temperature. The presence of 1.0 g L(-1) Ru/CeO2 increased the oxidation rate of BP by permanganate at pH 4.0-8.0 by 3-96 times. The increase in Ru/CeO2 dosage led to a progressive enhancement in the oxidation rate of BP by permanganate at neutral pH. The XANES analysis revealed that (1) Ru was deposited on the surface of CeO2 as Ru(III); (2) Ru(III) was oxidized by permanganate to its higher oxidation state Ru(VI) and Ru(VII), which acted as the co-oxidants in BP oxidation; (3) Ru(VI) and Ru(VII) were reduced by BP to its initial state of Ru(III). Therefore, Ru/CeO2 acted as an electron shuttle in catalytic permanganate oxidation process. LC-MS/MS analysis implied that BP was initially attacked by permanganate or Ru(VI) and Ru(VII) at the aromatic ring, leading to the formation of various hydroxyl-substituted and ring-opening products. Ru/CeO2 could maintain its catalytic activity during the six successive runs. In conclusion, catalyzing permanganate oxidation with Ru/CeO2 is a promising technology for degrading phenolic pollutants in water treatment.

  12. Catalytic Performance of CeO2/ZnO Nanocatalysts on the Oxidative Coupling of Methane with Carbon Dioxide and their Fractal Features

    Institute of Scientific and Technical Information of China (English)

    Yongjun He; Blun Yang; Haimin Pan; Guozhi Li

    2004-01-01

    CeO2/ZnO nanocatalysts were prepared from the coupling route of homogeneous precipitation with microemulsion and the impregnation method. The catalytic performance of these two kinds of catalysts on the oxidative coupling of methane with carbon dioxide was tested and compared; the fractal behavior of the nanocatalysts was analyzed using fractal theory. The CeO2/ZnO nanocatalysts had much higher activity than the catalysts prepared by impregnation method. There was no regular relationship between the average size of CeO2/ZnO nanocatalysts and their catalytic performance; however, the conversion of methane increased with the increase of the fractal dimension of CeO2/ZnO nanocatalysts.

  13. Utilizing peroxide as precursor for the synthesis of CeO2/ZnO composite oxide with enhanced photocatalytic activity

    Science.gov (United States)

    Lv, Zijian; Zhong, Qin; Ou, Man

    2016-07-01

    A facile synthesis method of CeO2/ZnO composite oxides with higher oxygen vacancy concentration was developed by a two-step precipitation method, in which peroxide was used as precursor. The photocatalytic activity of the catalysts under UV irradiation was studied in degradation of methylene blue (MB). All CeO2/ZnO photocatalysts exhibited higher photocatalytic performance than pure ZnO, and 1%CeO2/ZnO showed highest photocatalytic activity among the prepared catalysts. It was confirmed that the synergistic effect of CeO2 and oxygen vacancy caused the improved photocatalytic activity. Furthermore, the mechanism was investigated by introducing different additives, and it was found that the hydroxyl radicals played a crucial role in degradation process.

  14. Effects of CeO2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers

    Institute of Scientific and Technical Information of China (English)

    张辉; 邹勇; 邹增大; 史传伟

    2014-01-01

    The effects of CeO2 on microstructure and corrosion resistance of TiC-VC reinforced Fe-based laser cladding layers were investigated. The results showed that carbides presented in cladding layers were TiVC2 and VC. A small quantity of CeC appeared with 2.0 wt.%CeO2 addition. The amount of lamellar pearlite increased while the amount of residual austenite decreased with in-creasing CeO2 addition. The corrosion resistance of cladding layers increased firstly and then decreased with the addition of CeO2 in-creasing. The EIS spectrum of the cladding layer without CeO2 was composed of an inductive arc at low frequency and a capacitive arc at high frequency. The cladding layer with 0.5 wt.%CeO2 addition showed the best corrosion resistance, and then the inductive arc at low frequency transformed into a capacitive arc.

  15. Buffer gas-assisted four-wave mixing resonances in alkali vapor excited by a single cw laser

    Science.gov (United States)

    Shmavonyan, Svetlana; Khanbekyan, Aleksandr; Khanbekyan, Alen; Mariotti, Emilio; Papoyan, Aram V.

    2016-12-01

    We report the observation of a fluorescence peak appearing in dilute alkali (Rb, Cs) vapor in the presence of a buffer gas when the cw laser radiation frequency is tuned between the Doppler-broadened hyperfine transition groups of an atomic D2 line. Based on steep laser radiation intensity dependence above the threshold and spectral composition of the observed features corresponding to atomic resonance transitions, we have attributed these features to the buffer gas-assisted four-wave mixing process.

  16. Effect of water vapor on the CO and CH_4 catalytic oxidation over CeO_2-MO_x (M=Cu, Mn, Fe, Co, and Ni) mixed oxide

    Institute of Scientific and Technical Information of China (English)

    乔东升; 卢冠忠; 郭耘; 王艳芹; 郭杨龙

    2010-01-01

    CeO2-MOx (M=Cu, Mn, Fe, Co, and Ni) mixed oxide catalysts were prepared by a citric acid complexation-combustion method. CeO2-MOx solid solutions could be formed with M cations doping into CeO2 lattice, while NiO and Co3O4 phases were detected on the surface of CeO2-NiO and CeO2-Co3O4 by Raman spectroscopy. The presence of M in CeO2 could obviously promote its catalytic activity for CH4 catalytic combustion and CO oxidation. Among the prepared samples, CeO2-CuO exhibited the best performance for CO oxidatio...

  17. Stress response and tolerance of Zea mays to CeO2 nanoparticles: cross talk among H2O2, heat shock protein, and lipid peroxidation.

    Science.gov (United States)

    Zhao, Lijuan; Peng, Bo; Hernandez-Viezcas, Jose A; Rico, Cyren; Sun, Youping; Peralta-Videa, Jose R; Tang, Xiaolei; Niu, Genhua; Jin, Lixin; Varela-Ramirez, Armando; Zhang, Jian-ying; Gardea-Torresdey, Jorge L

    2012-11-27

    The rapid development of nanotechnology will inevitably release nanoparticles (NPs) into the environment with unidentified consequences. In addition, the potential toxicity of CeO(2) NPs to plants and the possible transfer into the food chain are still unknown. Corn plants (Zea mays) were germinated and grown in soil treated with CeO(2) NPs at 400 or 800 mg/kg. Stress-related parameters, such as H(2)O(2), catalase (CAT), and ascorbate peroxidase (APX) activity, heat shock protein 70 (HSP70), lipid peroxidation, cell death, and leaf gas exchange were analyzed at 10, 15, and 20 days post-germination. Confocal laser scanning microscopy was used to image H(2)O(2) distribution in corn leaves. Results showed that the CeO(2) NP treatments increased accumulation of H(2)O(2), up to day 15, in phloem, xylem, bundle sheath cells and epidermal cells of shoots. The CAT and APX activities were also increased in the corn shoot, concomitant with the H(2)O(2) levels. Both 400 and 800 mg/kg CeO(2) NPs triggered the up-regulation of the HSP70 in roots, indicating a systemic stress response. None of the CeO(2) NPs increased the level of thiobarbituric acid reacting substances, indicating that no lipid peroxidation occurred. CeO(2) NPs, at both concentrations, did not induce ion leakage in either roots or shoots, suggesting that membrane integrity was not compromised. Leaf net photosynthetic rate, transpiration, and stomatal conductance were not affected by CeO(2) NPs. Our results suggest that the CAT, APX, and HSP70 might help the plants defend against CeO(2) NP-induced oxidative injury and survive NP exposure.

  18. Comparative toxicity assessment of CeO2 and ZnO nanoparticles towards Sinorhizobium meliloti, a symbiotic alfalfa associated bacterium: use of advanced microscopic and spectroscopic techniques.

    Science.gov (United States)

    Bandyopadhyay, Susmita; Peralta-Videa, Jose R; Plascencia-Villa, Germán; José-Yacamán, Miguel; Gardea-Torresdey, Jorge L

    2012-11-30

    Cerium oxide (CeO(2)) and zinc oxide (ZnO) nanoparticles (NPs) are extensively used in a variety of instruments and consumer goods. These NPs are of great concern because of potential toxicity towards human health and the environment. The present work aimed to assess the toxic effects of 10nm CeO(2) and ZnO NPs towards the nitrogen fixing bacterium Sinorhizobium meliloti. Toxicological parameters evaluated included UV/Vis measurement of minimum inhibitory concentration, disk diffusion tests, and dynamic growth. Ultra high-resolution scanning transmission electron microscopy (STEM) and infrared spectroscopy (FTIR) were utilized to determine the spatial distribution of NPs and macromolecule changes in bacterial cells, respectively. Results indicate that ZnO NPs were more toxic than CeO(2) NPs in terms of inhibition of dynamic growth and viable cells counts. STEM images revealed that CeO(2) and ZnO NPs were found on bacterial cell surfaces and ZnO NPs were internalized into the periplasmic space of the cells. FTIR spectra showed changes in protein and polysaccharide structures of extra cellular polymeric substances present in bacterial cell walls treated with both NPs. The growth data showed that CeO(2) NPs have a bacteriostatic effect, whereas ZnO NPs is bactericidal to S. meliloti. Overall, ZnO NPs were found to be more toxic than CeO(2) NPs.

  19. Immobilization of metalloporphyrins on CeO2@SiO2 with a core-shell structure prepared via microemulsion method for catalytic oxidation of ethylbenzene

    Institute of Scientific and Technical Information of China (English)

    沈丹华; 吉琳韬; 付玲玲; 董旭龙; 刘志刚; 刘强; 刘世明

    2015-01-01

    CeO2@SiO2 core−shell nanoparticles were prepared by microemulsion method, and metalloporphyrins were immobilized on the CeO2@SiO2 core−shell nanoparticles surface via amide bond. The supported metalloporphyrin catalysts were characterized by N2 adsorption−desorption isotherm (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet and visible spectroscopy (UV-Vis), and Fourier transform infrared spectroscopy (FT-IR). The results show that the morphology of CeO2@SiO2 nanoparticles is core−shell microspheres with about 30 nm in diameter, and metalloporphyrins are immobilized on the CeO2@SiO2 core−shell nanoparticles via amide bond. Especially, the core−shell structure contains multi CeO2 core and thin SiO2 shell, which may benefit the synergistic effect between the CeO2 core and the porphyrin anchored on the very thin SiO2 shell. As a result, this supported metalloporphyrin catalysts present comparably high catalytic activity and stability for oxidation of ethylbenzene with molecular oxygen, namely, ethylbenzene conversion remains around 12% with identical selectivity of about 80%for acetophenone even after six-times reuse of the catalyst.

  20. Yb,Er-doped CeO2 nanotubes as an assistant layer for photoconversion-enhanced dye-sensitized solar cells

    Science.gov (United States)

    Zhao, Rongfang; Huan, Long; Gu, Peng; Guo, Rong; Chen, Ming; Diao, Guowang

    2016-11-01

    Yb,Er-doped CeO2 nanotubes were successfully synthesized using Ag nanowires as a hard template via a facile hydrothermal reaction and subsequent calcination and leaching processes. Yb,Er-doped CeO2 nanotubes as a promising assistant layer were investigated to determine theirs photovoltaic properties in an effort to enhance the power conversion efficiency of dye-sensitized solar cells (DSSCs). The influence factors of photoelectric properties of CeO2:Yb,Er NTs, including diameter of nanotubes, hydrothermal time, calcination temperature, and elements doping, have been studied. Compared with pristine P25 photoanode, the DSSCs fabricated by CeO2:Yb,Er nanotubes and P25 exhibited a power conversion efficiency (η) of 8.67%, an increase of 34%, and incident photo-to-electric conversion efficiency (IPCE) of 92.96%, an increase of 48.83%, which evidence that CeO2:Yb,Er NTs are a promising assistant photoanode material for DSSCs. The enhance mechanism of CeO2:Yb,Er nanotubes has been further revealed according to experimental results.

  1. A novel high-performance supercapacitor based on high-quality CeO2/nitrogen-doped reduced graphene oxide nanocomposite

    Science.gov (United States)

    Heydari, Hamid; Gholivand, Mohammad Bagher

    2017-03-01

    In this work, we have developed a novel nanocomposite via deposition of ceria (CeO2) on nitrogen-doped reduced graphene (CeO2/NRGO). NRGO was synthesized through a facile, safe, and scalable method to achieve simultaneous thermal reduction along with nitrogen doping of graphene oxide (GO) in air at much lower reaction temperature. CeO2/NRGO was prepared via a sonochemical method in which ceria nanoparticles were uniformly distributed on NRGO sheets. The structure and morphology of CeO2/NRGO nanocomposites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and Raman spectroscopy. Electrochemical properties of the proposed nanocomposite electrodes were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, continuous cyclic voltammetry (CCV), and electrochemical impedance spectroscopy (EIS) measurements. CeO2-NRGO nanocomposite electrodes showed excellent supercapacitive behavior, including much higher specific capacitance (230 F g-1 at 2 mV s-1) and higher rate capability compared to pure N-graphene. The cycling stability of the electrodes was measured by continues cyclic voltammetry (CCV) technique. The CCV showed that the specific capacitance of the CeO2/NRGO and NRGO nanocomposite maintained at 94.1 and 93.2% after 4000 cycles. The results suggest its promising potential as efficient electrode material for supercapacitors.

  2. First-principles DFT+U investigation of charged states of defects and fission gas atoms in CeO2

    Science.gov (United States)

    Shi, Lei; Vathonne, Emerson; Oison, Vincent; Freyss, Michel; Hayn, Roland

    2016-09-01

    Cerium dioxide (CeO2) is considered as a model material for the experimental study of radiation damage in the standard nuclear fuel uranium dioxide (UO2). In this paper, we present a first-principles study in the framework of the DFT+U approach to investigate the charged point defects and the incorporation of the fission gases Xe and Kr in CeO2 and compare it with published data in UO2. All intrinsic charge states are considered for point defects in contrast to previous published studies. Our calculations prove that CeO2 shows similar behavior to UO2 in the formation of point defects with the same charge states under stoichiometric and nonstoichiometric conditions. The charge states of vacancies have an important effect on the incorporation of fission gas atoms in CeO2. The bound Schottky defect with the two oxygen vacancies along the (100) direction is found to be energetically preferable to trap Xe and Kr atoms both in CeO2 and UO2. Xe and Kr atoms in the cation vacancy sites under nonformal charge states (different from 4 - ) in CeO2, unlike in UO2, lose electrons to their neighboring atoms, which is traced back to the absence of the +5 valence state for Ce in contrast to its existence for U.

  3. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    Energy Technology Data Exchange (ETDEWEB)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J. [Department of Materials Science and Engineering, NC State University, EB-1, Raleigh, North Carolina 27695-7907 (United States)

    2013-06-21

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 Multiplication-Sign 10{sup -9} s) at lower energies. Microstructural studies, conducted by X-ray diffraction ({theta}-2{theta} and {phi} techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO<111 > Double-Vertical-Line Double-Vertical-Line c-YSZ<001> and in-plane NiO<110> Double-Vertical-Line Double-Vertical-Line c-YSZ<100>. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min{sup -1} for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies

  4. Enhanced photocatalytic efficiency in zirconia buffered n-NiO/p-NiO single crystalline heterostructures by nanosecond laser treatment

    Science.gov (United States)

    Molaei, R.; Bayati, M. R.; Alipour, H. M.; Nori, S.; Narayan, J.

    2013-06-01

    We report the formation of NiO based single crystalline p-n junctions with enhanced photocatalytic activity induced by pulsed laser irradiation. The NiO epilayers were grown on Si(001) substrates buffered with cubic yttria-stabilized zirconia (c-YSZ) by using pulsed laser deposition. The NiO/c-YSZ/Si heterostructures were subsequently laser treated by 5 pulses of KrF excimer laser (pulse duration = 25 × 10-9 s) at lower energies. Microstructural studies, conducted by X-ray diffraction (θ-2θ and φ techniques) and high resolution transmission electron microscope, showed a cube-on-cube epitaxial relationship at the c-YSZ/Si interface; the epitaxial relationship across the NiO/c-YSZ interface was established as NiO⟨111 ⟩||c-YSZ⟨001⟩ and in-plane NiO⟨110⟩||c-YSZ⟨100⟩. Electron microscopy studies showed that the interface between the laser annealed and the pristine region as well as the NiO/c-YSZ interface was atomically sharp and crystallographically continuous. The formation of point defects, namely oxygen vacancies and NiO, due to the coupling of the laser photons with the NiO epilayers was confirmed by XPS. The p-type electrical characteristics of the pristine NiO epilayers turned to an n-type behavior and the electrical conductivity was increased by one order of magnitude after laser treatment. Photocatalytic activity of the pristine (p-NiO/c-YSZ/Si) and the laser-annealed (n-NiO/p-NiO/c-YSZ/Si) heterostructures were assessed by measuring the decomposition rate of 4-chlorophenol under UV light. The photocatalytic reaction rate constants were determined to be 0.0059 and 0.0092 min-1 for the as-deposited and the laser-treated samples, respectively. The enhanced photocatalytic efficiency was attributed to the suppressed charge carrier recombination in the NiO based p-n junctions and higher electrical conductivity. Besides, the oxygen vacancies ease the adsorption of 4-chlorophenol, hydroxyl, and water molecules to the surface. Thus, n

  5. Surface and Interface Properties of 10–12 Unit Cells Thick Sputter Deposited Epitaxial CeO2 Films

    Directory of Open Access Journals (Sweden)

    L. V. Saraf

    2008-01-01

    Full Text Available Ultrathin and continuous epitaxial films with relaxed lattice strain can potentially maintain more of its bulk physical and chemical properties and are useful as buffer layers. We study surface, interface, and microstructural properties of ultrathin (∼10–12 unit cells thick epitaxial ceria films grown on single crystal YSZ substrates. The out-of -plane and in-plane lattice parameters indicate relaxation in the continuous film due to misfit dislocations seen by high-resolution transmission electron microscopy (HRTEM and substrate roughness of ∼1-2 unit cells, confirmed by atomic force microscopy and HRTEM. A combination of secondary sputtering, lattice mismatch, substrate roughness, and surface reduction creating secondary phase was likely the cause of surface roughness which should be reduced to a minimum level for effective use of it as buffer layers.

  6. Toxicity of CeO2 nanoparticles at different trophic levels--effects on diatoms, chironomids and amphibians.

    Science.gov (United States)

    Bour, Agathe; Mouchet, Florence; Verneuil, Laurent; Evariste, Lauris; Silvestre, Jérôme; Pinelli, Eric; Gauthier, Laury

    2015-02-01

    The aim of the present work is to provide wider information on the toxicity of cerium dioxide nanoparticles (CeO2 NPs) in aquatic environments, by studying the toxicity of two types of CeO2 NPs for four species (diatoms Nitzschia palea, the sediment-dwelling invertebrate Chironomus riparius, and the amphibian larvae Xenopus laevis and Pleurodeles waltl.). The two types of CeO2 NPs have different intrinsic properties: some of them are small citrate-coated spheres (2-5 nm), and the others are larger uncoated plates (20-60 nm). Acute toxicity (mortality at 48 or 96 h, depending on the test-organism) was assessed for the four species, from 0.1 to 100 mg L(-1) of NPs. Sub-lethal effects were assessed on chironomids exposed between 0.01 and 1 mg L(-1) of NPs. Mortality, growth inhibition and genotoxic effects were evaluated on amphibian larvae from 0.1 to 10 mg L(-1). Results reveal that no acute toxicity occurs on any species after short exposures, even at the highest concentrations. Mortality (35%) is observed on Xenopus larvae after 12d of exposure at the highest concentration of one type of NPs. No significant effects were observed on chironomids during chronic exposure. Xenopus larvae growth was inhibited from 1 mg L(-1) of both NPs while growth inhibition is observed on Pleurodeles only at the highest concentration of one type of NPs. No genotoxicity was observed on Xenopus but Pleurodeles exhibited dose-dependent genotoxic effects when exposed to one type of NPs. Observed differences in toxicity are discussed focusing on the studied compartment, routes of exposure, species and NPs.

  7. New route to CeO2/LaCoO3 with high oxygen mobility for total benzene oxidation

    Science.gov (United States)

    Wang, Xiuyun; Zuo, Jiachang; Luo, Yongjin; Jiang, Lilong

    2017-02-01

    Electrospun LaCoO3 and Ce(NO3)3·6H2O were used as precursors to synthesize CeO2/LaCoO3 (SSI-LaCoCe) with high oxygen mobility by solid state impregnation. Besides, electrospinning and ball milling technologies were also adopted to prepare the other two La-Co-Ce oxides, which are denoted as ES-LaCoCe and BM-LaCoCe, respectively. The catalysts were evaluated for total benzene oxidation in comparison with bare electrospun LaCoO3 and CeO2, and characterized by means of O2-TPSR, XRD, BET, TEM, H2-TPR, O2-TPD, and XPS. Relative to LaCoO3, an enhanced catalytic performance can be obtained for La-Co-Ce oxides. Importantly, the concentration of surface adsorbed oxygen species from the highest to the lowest is SSI-LaCoCe > BM-LaCoCe > ES-LaCoCe, which is in good agreement with the order of catalytic activity in terms of T50. The high oxygen mobility in SSI-LaCoCe can be connected with sufficient interaction between active LaCoO3 and CeO2. On the other hand, O2-TPSR analysis match well with the catalytic behaviors of La-Co-Ce oxides. Moreover, the catalyst with the best performance, SSI-LaCoCe, also represents good thermal stability during the long-term continuous test.

  8. Fabrication and dye removal performance of magnetic CuFe2O4@CeO2 nanofibers

    Science.gov (United States)

    Zou, Lianli; Wang, Qiuju; Shen, Xiangqian; Wang, Zhou; Jing, Maoxiang; Luo, Zhou

    2015-03-01

    Novel magnetic adsorbents with CeO2 nanoparticles (about 20 nm) coated on CuFe2O4 nanofibers were fabricated by combining electrospinning technique and chemical precipitation methods. The prepared CuFe2O4@CeO2 composite nanofibers show a diameter of 200 nm with a high specific surface area of 64.12 m2/g. These composite nanofibers exhibit a typical soft-magnetic materials behavior with a specific saturation magnetization (Ms) of 20.51 Am2/kg. The adsorption performances of these composite nanofibers were evaluated by column bed studies for methyl orange (MO) removal from aqueous solution. The effect of pH, flow rate and dye concentration on adsorption performances were investigated. The results show that the adsorption capacity decreases with increase of pH. The largest adsorption capacity of the column beds shows about 100 g/mL under the condition of C0 = 0.05 mg/mL, F = 2.0 mL/min and pH 4.0. The kinetic process is described by Thomas model. The rate constant decreases with the extension of reaction time and decreasing pH. The desorption behaviors are also studied in 0.5 M NaCl solution, ethyl alcohol and deionized water, respectively, which show that the adsorbed MO molecules can be easily desorbed from CuFe2O4@CeO2 composite nanofibers in NaCl solution. The adsorption mechanism of ionic interaction, formation of hydrogen bonds and pore diffusion is rationally proposed.

  9. Preparation and photocatalytic activity of laponite pillared by CeO_2 modified TiO_2

    Institute of Scientific and Technical Information of China (English)

    林英光; 皮丕辉; 郑大锋; 杨卓如; 王炼石

    2010-01-01

    The laponite pillared by the CeO2 modified TiO2 (Ce-Ti-lap) were prepared by microwave intercalation reaction with laponite as the layered clay, tetrabutyl titanate and cerium chloride as the Ce-Ti composite pillaring agent, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brumauer-Emmett-Teller (BET) surface area. The photocatalytic activities of Ce-Ti-lap were investigated by the degradation of methyl orange (MO). The results showed that Ce and Ti could be introduced to...

  10. Preparation and characterization of CeO_2 doped ZnO nano-tubes fluorescent composite

    Institute of Scientific and Technical Information of China (English)

    李酽; 刘秀琳; 栗建钢

    2010-01-01

    ZnO nanotubes were hydrothermally synthesized and the ZNTs/CeO2 fluorescent composite were prepared by introducing nano CeO2 particles into ZnO nano-tubes via a chemical solution adsorption and annealing process. The samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transformation infrared spectroscopy and room temperature photoluminescence measurement. Due to the interaction between Ce4+ and the surface atoms of ZnO2 nano-tubes, a photoluminescence enhancement was obser...

  11. Extracellular polymeric substances (EPS of freshwater biofilms stabilize and modify CeO2 and Ag nanoparticles.

    Directory of Open Access Journals (Sweden)

    Alexandra Kroll

    Full Text Available Streams are potential receiving compartments for engineered nanoparticles (NP. In streams, NP may remain dispersed or settle to the benthic compartment. Both dispersed and settling NP can accumulate in benthic biofilms called periphyton that are essential to stream ecosystems. Periphytic organisms excrete extracellular polymeric substances (EPS that interact with any material reaching the biofilms. To understand the interaction of NP with periphyton it is therefore crucial to study the interaction of NP with EPS. We investigated the influence of EPS on the physicochemical properties of selected NP (CeO2, Ag under controlled conditions at pH 6, 7.6, 8.6 and light or dark exposure. We extracted EPS from five different periphyton communities, characterized the extracts, and exposed CeO2 and carbonate-stabilized Ag NP (0.5 and 5 mg/L, both 25 nm primary particle size and AgNO3 to EPS (10 mg/L over two weeks. We measured NP size distribution, shape, primary particle size, surface plasmon resonance, and dissolution. All EPS extracts were composed of biopolymers, building blocks of humic substances, low molecular weight (Mr acids, and small amphiphilic or neutral compounds in varying concentrations. CeO2 NP were stabilized by EPS independent of pH and light/dark while dissolution increased over time in the dark at pH 6. EPS induced a size increase in Ag NP in the light with decreasing pH and the formation of metallic Ag NP from AgNO3 at the same conditions via EPS-enhanced photoreduction. NP transformation and formation were slower in the extract with the lowest biopolymer and low Mr acid concentrations. Periphytic EPS in combination with naturally varying pH and light/dark conditions influence the properties of the Ag and CeO2 NP tested and thus the exposure conditions within biofilms. Our results indicate that periphytic organisms may be exposed to a constantly changing mixture of engineered and naturally formed Ag NP and Ag+.

  12. Preparation of CeO2 Nanoparticles and Its Application to Ion-selective Electrodes Based on Acetyl Cellulose

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    CeO2 nanoparticles with an average diameter of about 30 nm were prepared by sol-gel method at lower temperature. The gel, transformed from the aqueous solution of metal nitrate and citric acid, can be combusted completely at lower temperature. The redox behavior and the crystallization process of the dried gel were studied by thermogravimetric analysis and infrared spectroscopy. The synthesized powders were characterized by X-ray powder diffraction and transmission electron microscopy. In addition, rare earth elements ion-selective electrodes based on acetyl cellulose were prepared using ultra fine cerium oxide powders.

  13. Mechanical Properties and Corrosion Behavior of CeO2 and SiC Incorporated Al5083 Alloy Surface Composites

    Science.gov (United States)

    Amra, M.; Ranjbar, Khalil; Dehmolaei, R.

    2015-08-01

    In this investigation, nano-sized cerium oxide (CeO2) and silicon carbide (SiC) particles were stirred and mixed into the surface of an Al5083 alloy rolled plate using friction stir processing (FSP) to form a surface nano-composite layer. For this purpose, various volume ratios of the reinforcements either separately or in the combined form were packed into a pre-machined groove on the surface of the plate. Microstructural features, mechanical properties, and corrosion behavior of the resultant surface composites were determined. Microstructural analysis, optical microscopy and scanning electron microscopy, showed that reinforcement particles were fairly dispersed inside the stir zone and grain refinement was gained. Compared with the base alloy, all of the FSP composites showed higher hardness and tensile strength values with the maximum being obtained for the composite containing 100% SiC particles, i.e., Al5083/SiC. The corrosion behavior of the samples was studied by conducting potentiodynamic polarization tests and assessed in terms of corrosion potential, pitting potential, and passivation range. The result shows a significant increase in corrosion resistance of the base alloy; i.e., the longest passivation range when CeO2 alone was incorporated into the surface by acting as cathodic inhibitors. Composites reinforced with SiC particles exhibited lower pitting resistance due to the formation of microgalvanic couples between cathodic SiC particles and anodic aluminum matrix. The study was aimed to fabricate metal matrix surface composites with improved hardness, tensile strength, and corrosion resistance by the incorporation of CeO2 and SiC reinforcement particles into the surface of Al5083 base alloy. Optimum mechanical properties and corrosion resistance were obtained for the FSP composite Al5083/(75%CeO2 + 25%SiC). In this particular FSP composite, hardness and tensile strength were increased by 30, and 14%, respectively, and passivation range was increased to 0.19 V/SCE compared to the base alloy with no passivation range.

  14. Preparation and Characterization of CeO2-TiO2/SnO2:Sb Films Deposited on Glass Substrates by R.F.Sputtering

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qingnan; DONG Yuhong; NI Jiamiao; WANG Peng; ZHAO Xiujian

    2008-01-01

    CeO2-TiO2 films and CeO2-TiO2/SnO2:Sb(6 mol%)double films were deposited on glass substrates by radio-frequency magnetron sputtering(R.F.Sputtering),using SnO2:Sb(6 mol%)target,and CeO2-TiO2 targets with different molar ratio of CeO2 to TiO2 (CeO2:TiO2=0:1.0;0.1:0.9;0.2:0.8;0.3:0.7;0.4:0.6;0.5:0.5;0.6:0.4; 0.7:0.3; 0.8:0.2;0.9:0.1;1.0:0).The films are characterized by UV-visible transmission and infrared reflection spectra,scanning electron microscopy(SEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and X-ray diffraction(XRD),respectively.The obtained results show that the amorphous phases composed of CeO2-TiO2 play an important role in absorbing UV, there are Ce3+,Ce4+ and Ti4+ on the surface of the films;the glass substrates coated with CeO2-TiO2(Ce/Ti=0.5:0.5;0.6:0.4)/SnO2:Sb(6 mol%) double films show high absorbing UV(>99),high visible light transmission(75%)and good infrared reflection films can be used as window glass of buildings,automobile and so on.

  15. Aspect ratio plays a role in the hazard potential of CeO2 nanoparticles in mouse lung and zebrafish gastrointestinal tract.

    Science.gov (United States)

    Lin, Sijie; Wang, Xiang; Ji, Zhaoxia; Chang, Chong Hyun; Dong, Yuan; Meng, Huan; Liao, Yu-Pei; Wang, Meiying; Song, Tze-Bin; Kohan, Sirus; Xia, Tian; Zink, Jeffrey I; Lin, Shuo; Nel, André E

    2014-05-27

    We have previously demonstrated that there is a relationship between the aspect ratio (AR) of CeO2 nanoparticles and in vitro hazard potential. CeO2 nanorods with AR ≥ 22 induced lysosomal damage and progressive effects on IL-1β production and cytotoxicity in the human myeloid cell line, THP-1. In order to determine whether this toxicological paradigm for long aspect ratio (LAR) CeO2 is also relevant in vivo, we performed comparative studies in the mouse lung and gastrointestinal tract (GIT) of zebrafish larvae. Although oropharyngeal aspiration could induce acute lung inflammation for CeO2 nanospheres and nanorods, only the nanorods with the highest AR (C5) induced significant IL-1β and TGF-β1 production in the bronchoalveolar lavage fluid at 21 days but did not induce pulmonary fibrosis. However, after a longer duration (44 days) exposure to 4 mg/kg of the C5 nanorods, more collagen production was seen with CeO2 nanorods vs nanospheres after correcting for Ce lung burden. Using an oral-exposure model in zebrafish larvae, we demonstrated that C5 nanorods also induced significant growth inhibition, a decrease in body weight, and delayed vertebral calcification. In contrast, CeO2 nanospheres and shorter nanorods had no effect. Histological and transmission electron microscopy analyses showed that the key injury mechanism of C5 was in the epithelial lining of the GIT, which demonstrated blunted microvilli and compromised digestive function. All considered, these data demonstrate that, similar to cellular studies, LAR CeO2 nanorods exhibit more toxicity in the lung and GIT, which could be relevant to inhalation and environmental hazard potential.

  16. In-situ transmission electron microscopy study of oxygen vacancy ordering and dislocation annihilation in undoped and Sm-doped CeO2 ceramics during redox processes

    Science.gov (United States)

    Ding, Yong; Chen, Yu; Pradel, Ken C.; Liu, Meilin; Lin Wang, Zhong

    2016-12-01

    Ceria (CeO2) based ceramics have been widely used for many applications due to their unique ionic, electronic, and catalytic properties. Here, we report our findings in investigating into the redox processes of undoped and Sm-doped CeO2 ceramics stimulated by high-energy electron beam irradiation within a transmission electron microscope (TEM). The reduced structure with oxygen vacancy ordering has been identified as the CeO1.68 (C-Ce2O3+δ) phase via high-resolution TEM. The reduction of Ce4+ to Ce3+ has been monitored by electron energy-loss spectroscopy. The decreased electronic conductivity of the Sm-doped CeO2 (Sm0.2Ce0.8O1.9, SDC) is revealed by electron holography, as positive electrostatic charges accumulated at the surfaces of SDC grains under electron beam irradiation, but not at CeO2 grains. The formation of the reduced CeO1.68 domains corresponds to lattice expansion compared to the CeO2 matrix. Therefore, the growth of CeO1.68 nuclei builds up strain inside the matrix, causing annihilation of dislocations inside the grains. By using in-situ high-resolution TEM and a fast OneView camera recording system, we investigated dislocation motion inside both CeO2 and SDC grains under electron beam irradiation. The dislocations prefer to dissociate into Shockley partials bounded by stacking faults. Then, the partials can easily glide in the {111} planes to reach the grain surfaces. Even the Lomer-Cottrell lock can be swept away by the phase change induced strain field. Our results revealed the high mobility of dislocations inside CeO2 and SDC grains during their respective redox processes.

  17. MnO(x) Nanoparticle-Dispersed CeO2 Nanocubes: A Remarkable Heteronanostructured System with Unusual Structural Characteristics and Superior Catalytic Performance.

    Science.gov (United States)

    Putla, Sudarsanam; Amin, Mohamad Hassan; Reddy, Benjaram M; Nafady, Ayman; Al Farhan, Khalid A; Bhargava, Suresh K

    2015-08-05

    Understanding the interface-induced effects of heteronanostructured catalysts remains a significant challenge due to their structural complexity, but it is crucial for developing novel applied catalytic materials. This work reports a systematic characterization and catalytic evaluation of MnOx nanoparticle-dispersed CeO2 nanocubes for two important industrial applications, namely, diesel soot oxidation and continuous-flow benzylamine oxidation. The X-ray diffraction and Raman studies reveal an unusual lattice expansion in CeO2 after the addition of MnOx. This interesting observation is due to conversion of smaller sized Ce(4+) (0.097 nm) to larger sized Ce(3+) (0.114 nm) in cerium oxide led by the strong interaction between MnOx and CeO2 at their interface. Another striking observation noticed from transmission electron microscopy, high angle annular dark-field scanning transmission electron microscopy, and electron energy loss spectroscopy studies is that the MnOx species are well-dispersed along the edges of the CeO2 nanocubes. This remarkable decoration leads to an enhanced reducible nature of the cerium oxide at the MnOx/CeO2 interface. It was found that MnOx/CeO2 heteronanostructures efficiently catalyze soot oxidation at lower temperatures (50% soot conversion, T50 ∼660 K) compared with that of bare CeO2 nanocubes (T50 ∼723 K). Importantly, the MnOx/CeO2 heteronanostructures exhibit a noticeable steady performance in the oxidation of benzylamine with a high selectivity of the dibenzylimine product (∼94-98%) compared with that of CeO2 nanocubes (∼69-91%). The existence of a strong synergistic effect at the interface sites between the CeO2 and MnOx components is a key factor for outstanding catalytic efficiency of the MnOx/CeO2 heteronanostructures.

  18. Sm doped mesoporous CeO2 nanocrystals: aqueous solution-based surfactant assisted low temperature synthesis, characterization and their improved autocatalytic activity.

    Science.gov (United States)

    Mandal, Bappaditya; Mondal, Aparna; Ray, Sirsendu Sekhar; Kundu, Amar

    2016-01-28

    Mesoporous Sm(3+) doped CeO2 (Ce-Sm) with a nanocrystalline framework, a high content of Ce(3+) and surface area (184 m(2) g(-1)), have been synthesized through a facile aqueous solution-based surfactant assisted route by using inorganic precursors and sodium dodecyl sulphate as a template. The XRD results indicate that the calcined Ce-Sm and even the as-prepared material have a cubic fluorite structure of CeO2 with no crystalline impurity phase. XRD studies along with HRTEM results confirmed the formation of mesoporous nanocrystalline CeO2 at a lower temperature as low as 100 °C. A detailed analysis revealed that Sm(3+) doping in CeO2 has increased the lattice volume, surface area, mesopore volume and engineered the surface defects. Higher concentrations of Ce(3+) and oxygen vacancies of Ce-Sm resulted in lowering of the band gap. It is evident from the H2-TPR results that Sm(3+) doping in CeO2 strongly modified the reduction behavior of CeO2 by shifting the bulk reduction at a much lower temperature, indicating increased oxygen mobility in the sample which enables enhanced oxygen diffusion at lower temperatures, thus promoting reducibility, i.e., the process of Ce(4+)→ Ce(3+). UV-visible transmission studies revealed improved autocatalytic performance due to easier Ce(4+)/Ce(3+) recycling in the Sm(3+) doped CeO2 nanoparticles. From the in vitro cytotoxicity of both pure CeO2 and Sm(3+) doped CeO2 calcined at 500 °C in a concentration as high as 100 μg mL(-1) (even after 120 h) on MG-63 cells, no obvious decrease in cell viability is observed, confirming their excellent biocompatibility. The presence of an increased amount of surface hydroxyl groups, mesoporosity, and surface defects have contributed towards an improved autocatalytic activity of mesoporous Ce-Sm, which appear to be a potential candidate for biomedical (antioxidant) applications.

  19. Designing CuOx Nanoparticle-Decorated CeO2 Nanocubes for Catalytic Soot Oxidation: Role of the Nanointerface in the Catalytic Performance of Heterostructured Nanomaterials.

    Science.gov (United States)

    Sudarsanam, Putla; Hillary, Brendan; Mallesham, Baithy; Rao, Bolla Govinda; Amin, Mohamad Hassan; Nafady, Ayman; Alsalme, Ali M; Reddy, B Mahipal; Bhargava, Suresh K

    2016-03-08

    This work investigates the structure-activity properties of CuOx-decorated CeO2 nanocubes with a meticulous scrutiny on the role of the CuOx/CeO2 nanointerface in the catalytic oxidation of diesel soot, a critical environmental problem all over the world. For this, a systematic characterization of the materials has been undertaken using transmission electron microscopy (TEM), transmission electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDS), high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM), scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS), X-ray diffraction (XRD), Raman, N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS) techniques. The TEM images show the formation of nanosized CeO2 cubes (∼25 nm) and CuOx nanoparticles (∼8.5 nm). The TEM-EDS elemental mapping images reveal the uniform decoration of CuOx nanoparticles on CeO2 nanocubes. The XPS and Raman studies show that the decoration of CuOx on CeO2 nanocubes leads to improved structural defects, such as higher concentrations of Ce(3+) ions and abundant oxygen vacancies. It was found that CuOx-decorated CeO2 nanocubes efficiently catalyze soot oxidation at a much lower temperature (T50 = 646 K, temperature at which 50% soot conversion is achieved) compared to that of pristine CeO2 nanocubes (T50 = 725 K) under tight contact conditions. Similarly, a huge 91 K difference in the T50 values of CuOx/CeO2 (T50 = 744 K) and pristine CeO2 (T50 = 835 K) was found in the loose-contact soot oxidation studies. The superior catalytic performance of CuOx-decorated CeO2 nanocubes is mainly attributed to the improved redox efficiency of CeO2 at the nanointerface sites of CuOx-CeO2, as evidenced by Ce M5,4 EELS analysis, supported by XRD, Raman, and XPS studies, a clear proof for the role of nanointerfaces in the performance of heterostructured nanocatalysts.

  20. [Catalytic wet air oxidation of phenol with Ru/ZrO2-CeO2 catalyst].

    Science.gov (United States)

    Wang, Jian-bing; Zhu, Wan-peng; Wang, Wei; Yang, Shao-xia

    2007-07-01

    Wet air oxidation of phenol with Ru/ZrO2-CeO2 was systematically investigated and results showed that Ru/ZrO2-CeO2 could significantly increase the removal of COD and phenol. At the reaction temperature of 170 degrees C and pressure of 3MPa, about 99% COD and 100% phenol was removed respectively after 120 min. The optimal conditions were: reaction temperature, 170 degrees C; reaction pressure, 3 MPa; catalyst dosage, 5 g/L; agitator speed, 500 r/min. By analyzing intermediates, a simplified scheme of phenol oxidation was brought out. It includes two main steps. The first step is the production of organic acids, which is fast. The second step is the oxidation of organic acid, in which the oxidation of acetic acid is slow. Complete oxidation of acetic acid needs high temperature at which the radicals assault the C-H bond of a carbon and acetic acid is oxidized into carbon dioxide and water through formic acid.

  1. Modification of Cu/ZSM-5 catalyst with CeO2for selective catalytic reduction of NOxwith ammonia

    Institute of Scientific and Technical Information of China (English)

    刘雪松; 吴晓东; 翁端; 石磊

    2016-01-01

    Cu/ZSM-5 and CeO2-modified Cu/ZSM-5 catalysts were prepared by a wetness impregnation method. The addition of CeO2was found to enhance the NOxselective catalytic reduction (SCR) activity of the catalyst atlow temperatures, but the high-temperature activitywas weakened. The catalysts were characterized by X-ray diffraction (XRD), nitrogen physisorption, induc-tively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), H2temperature-programmed reduction (TPR) and NH3temperature-programmed desorption (TPD). The results showedthat more CuO clusters instead of isolated Cu2+specieswere obtained on the modified catalyst. These active CuO clusters, as well as the Cu-Ce synergistic effect, improvedthe redox property of the catalyst and low-temperatures SCR activity via promoting the oxidation of NO to NO2and fast SCR reaction. The loss in high-temperatures activitywas attributedto the enhanced competitive ox-idation of NH3by O2and decreased surface acidity of the catalyst.

  2. Hybrid nanocomposite from aniline and CeO2 nanoparticles: Surface protective performance on mild steel in acidic environment

    Science.gov (United States)

    Sasikumar, Y.; Kumar, A. Madhan; Gasem, Zuhair M.; Ebenso, Eno E.

    2015-03-01

    This present work contributes to the development of a new generation of active corrosion inhibitors composed of CeO2 nanoparticles covered with polyaniline that are able to release entrapped nanoparticles in acidic medium. Nanocomposites of aniline and CeO2 nanoparticles have been chemically synthesized by in-situ polymerization. The structural evolutions and morphological characteristics of PANI/CeO2 nanocomposite (PCN) have performed using various techniques such as XRD, IR, XPS, SEM and TEM analysis. It was illustrated from SEM and TEM observation that the PCN has globular particle with core-shell structure. The inhibition properties of synthesized PCN on mild steel (MS) corrosion in 0.5 M HCl were estimated using weight loss and electrochemical techniques. Potentiodynamic polarization results revealed PCN to be a mixed-type inhibitor, while impedance results indicate the adsorption of the PCN film on the MS surface. The inhibition efficiency of PCN was found to increase almost linearly with concentration. Moreover, an increase in the water contact-angle with PCN indicated its adsorption at the MS surface, and ATR-IR, SEM/EDAX and AFM visualization confirmed the formation of a protective film adsorbed on a MS surface. Finally, it was concluded that the PCN is a potential inhibitor for mild steel in HCl medium.

  3. Nanoscale mechanochemical wear of phosphate laser glass against a CeO2 particle in humid air

    Science.gov (United States)

    Yu, Jiaxin; He, Hongtu; Zhang, Yafeng; Hu, Hailong

    2017-01-01

    Using an atomic force microscope, the friction and wear of phosphate laser glass against a CeO2 particle were quantitatively studied both in humid air and in vacuum, to reveal the water molecules induced mechanochemical wear mechanism of phosphate laser glass. The friction coefficient of the glass/CeO2 pair in air was found to be 5-7 times higher than that in vacuum due to the formation of a capillary water bridge at the friction interface, with a contribution of the capillary-related friction to the total friction coefficient as high as 65-79%. The capillary water bridge further induced a serious material removal of glass and CeO2 particle surfaces, while supplying both a local liquid water environment to corrode the glass surface and a high shearing force to assist the stretching of the Cesbnd Osbnd P bond, accelerating the reaction between water and the glass/CeO2 pair. In vacuum, however, no discernable wear phenomena were observed, but the phase images captured by AFM tapping mode suggested the occurrence of potential strain hardening in the friction area of the glass surface.

  4. Anchoring noble metal nanoparticles on CeO2 modified reduced graphene oxide nanosheets and their enhanced catalytic properties.

    Science.gov (United States)

    Ji, Zhenyuan; Shen, Xiaoping; Xu, Yuling; Zhu, Guoxing; Chen, Kangmin

    2014-10-15

    The strategy of structurally integrating noble metal, metal oxide, and graphene is expected to offer prodigious opportunities toward emerging functions of graphene-based nanocomposites. In this study, we develop a facile two-step approach to disperse noble metal (Pt and Au) nanoparticles on the surface of CeO2 functionalized reduced graphene oxide (RGO) nanosheets. It is shown that Pt and Au with particle sizes of about 5 and 2nm are well dispersed on the surface of RGO/CeO2. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 was used as a model reaction to quantitatively evaluate the catalytic properties of the as-synthesized RGO/Pt/CeO2 and RGO/Au/CeO2 ternary nanocomposites. In such triple-component catalysts, CeO2 nanocrystals provide unique and critical roles for optimizing the catalytic performance of noble metallic Pt and Au, allowing them to express enhanced catalytic activities in comparison with RGO/Pt and RGO/Au catalysts. In addition, a possible mechanism for the enhanced catalytic activities of the RGO/Pt/CeO2 and RGO/Au/CeO2 ternary catalysts in the reduction of 4-NP is proposed. It is expected that our prepared graphene-based triple-component composites, which inherit peculiar properties of graphene, metal oxide, and noble metal, are attractive candidates for catalysis and other applications.

  5. Adsorption and Reaction of Acetaldehyde on Shape-Controlled CeO2 Nanocrystals: Elucidation of Structure-function Relationships

    Energy Technology Data Exchange (ETDEWEB)

    Mann, Amanda K [ORNL; Wu, Zili [ORNL; Calaza, Florencia [Max Planck Society, Fritz Haber Institute; Overbury, Steven {Steve} H [ORNL

    2014-01-01

    CeO2 cubes with {100} facets, octahedra with {111} facets, and wires with highly defective structures were utilized to probe the structure-dependent reactivity of acetaldehyde. Using temperature-programmed desorption (TPD), temperature-programmed surface reactions (TPSR), and in situ infrared spectroscopy it was found that acetaldehyde desorbs unreacted or undergoes reduction, coupling, or C-C bond scission reactions depending on the surface structure of CeO2. Room temperature FTIR indicates that acetaldehyde binds primarily as 1-acetaldehyde on the octahedra, in a variety of conformations on the cubes, including coupling products and acetate and enolate species, and primarily as coupling products on the wires. The percent consumption of acetaldehyde follows the order of wires > cubes > octahedra. All the nanoshapes produce the coupling product crotonaldehyde; however, the selectivity to produce ethanol follows the order wires cubes >> octahedra. The selectivity and other differences can be attributed to the variation in the basicity of the surfaces, defects densities, coordination numbers of surface atoms, and the reducibility of the nanoshapes.

  6. The effect of fission-energy Xe ion irradiation on the structural integrity and dissolution of the CeO2 matrix

    Science.gov (United States)

    Popel, A. J.; Le Solliec, S.; Lampronti, G. I.; Day, J.; Petrov, P. K.; Farnan, I.

    2017-02-01

    This work considers the effect of fission fragment damage on the structural integrity and dissolution of the CeO2 matrix in water, as a simulant for the UO2 matrix of spent nuclear fuel. For this purpose, thin films of CeO2 on Si substrates were produced and irradiated by 92 MeV 129Xe23+ ions to a fluence of 4.8 × 1015 ions/cm2 to simulate fission damage that occurs within nuclear fuels along with bulk CeO2 samples. The irradiated and unirradiated samples were characterised and a static batch dissolution experiment was conducted to study the effect of the induced irradiation damage on dissolution of the CeO2 matrix. Complex restructuring took place in the irradiated films and the irradiated samples showed an increase in the amount of dissolved cerium, as compared to the corresponding unirradiated samples. Secondary phases were also observed on the surface of the irradiated CeO2 films after the dissolution experiment.

  7. Nanoflake-assembled Al2O3-supported CeO2-ZrO2 as an efficient catalyst for oxidative dehydrogenation of ethylbenzene with CO2

    Science.gov (United States)

    Wang, Tehua; Guan, Xiaolin; Lu, Huiyi; Liu, Zhongwen; Ji, Min

    2017-03-01

    An Al2O3 material assembled by nanoflakes was used to prepare supported CeO2-ZrO2 catalyst via a deposition-precipitation method for oxidative dehydrogenation of ethylbenzene with CO2. Both unsupported and commercial Al2O3-supported CeO2-ZrO2 were prepared for comparison. It was found that the CeO2-ZrO2/nanoflake-assembled Al2O3 catalyst exhibited the best catalytic activity. The characterization results revealed that the slit-shape pores existing in nanoflake-assembled Al2O3 were responsible for the small particle size and high Ce/Zr surface ratio of supported CeO2-ZrO2 species. The dispersion of Ce1-xZrx(OH)4 precursors onto Al2O3 support surface during the deposition-precipitation process was proposed. The high dispersion and large numbers of surface oxygen vacancies of the CeO2-ZrO2 species on nanoflake-assembled Al2O3 contributed to the excellent catalytic performance in oxidative dehydrogenation of ethylbenzene with CO2. This kind of special Al2O3 is expected to be a promising support for preparing highly dispersed metal/metal oxide catalysts.

  8. Adsorption mechanism and kinetics of azo dye chemicals on oxide nanotubes: a case study using porous CeO2 nanotubes

    Science.gov (United States)

    Wu, Junshu; Wang, Jinshu; Du, Yucheng; Li, Hongyi; Jia, Xinjian

    2016-07-01

    Metal oxide nanotubes are believed to be promising materials with adsorption functionality for water purification due to their synergistic effect of the overall microscale morphology for easy separation and nanoscale surface characters providing enough surface active absorption sites. This work shows the synthesis of uniform hierarchical porous CeO2 nanotubes via nanowire-directed templating method and describes the adsorption behavior of CeO2 nanotubes for a typical azo dye Congo red which has resistance to oxidation and decoloration in natural conditions. Fourier transform infrared spectroscopy spectra provided the evidence that Congo red was successfully coated on the surface of CeO2 nanotubes by both bidentate-type bridge link of Ce4+ cations from sulfonate SO3 - groups and the electrostatic attraction between the protonated surface generated by oxygen vacancies and dissociated sulfonate groups. The adsorption kinetic data fitted well to the pseudo-second-order kinetic equation, whereas the Langmuir isotherm equation exhibited better correlation with the experimental data. The calculated maximum adsorption capacity from the isothermal model was 362.32 mg/g. In addition, the prepared CeO2 nanotubes exhibited good recyclability and reusability as highly efficient adsorbents for Congo red removal after regeneration. These favorable performances enable the obtained CeO2 nanotubes to be promising materials for dye removal from aqueous solution.

  9. Synthesis and Characterization of CeO2-SiO2 Nanoparticles by Microwave-Assisted Irradiation Method for Photocatalytic Oxidation of Methylene Blue Dye

    Directory of Open Access Journals (Sweden)

    R. M. Mohamed

    2012-01-01

    Full Text Available CeO2-SiO2 nanoparticles were synthesized for the first time by a facile microwave-assisted irradiation process. The effect of irradiation time of microwave was studied. The materials were characterized by N2 adsorption, XRD, UV-vis/DR, and TEM. All solids showed mesoporous textures with high surface areas, relatively small pore size diameters, and large pore volume. The X-ray diffraction results indicated that the as-synthesized nanoparticles exhibited cubic CeO2 without impurities and amorphous silica. The transmission electron microscopy (TEM images revealed that the particle size of CeO2-SiO2 nanoparticles, which were prepared by microwave method for 30 min irradiation times, was around 8 nm. The photocatalytic activities were evaluated by the decomposition of methylene blue dye under UV light irradiations. The results showed that the irradiation under the microwave produced CeO2-SiO2 nanoparticles, which have the best crystallinity under a shorter irradiation time. This indicates that the introduction of the microwave really can save energy and time with faster kinetics of crystallization. The sample prepared by 30 min microwave irradiation time exhibited the highest photocatalytic activity. The photocatalytic activity of CeO2-SiO2 nanoparticles, which were prepared by 30 min irradiation times was found to have better performance than commercial reference P25.

  10. Enhanced Gas Sensing Properties of SnO2 Hollow Spheres Decorated with CeO2 Nanoparticles Heterostructure Composite Materials.

    Science.gov (United States)

    Liu, Jiangyang; Dai, Mingjun; Wang, Tianshuang; Sun, Peng; Liang, Xishuang; Lu, Geyu; Shimanoe, Kengo; Yamazoe, Noboru

    2016-03-01

    CeO2 decorated SnO2 hollow spheres were successfully synthesized via a two-step hydrothermal strategy. The morphology and structures of as-obtained CeO2/SnO2 composites were analyzed by various kinds of techniques. The SnO2 hollow spheres with uniform size around 300 nm were self-assembled with SnO2 nanoparticles and were hollow with a diameter of about 100 nm. The CeO2 nanoparticles on the surface of SnO2 hollow spheres could be clearly observed. X-ray photoelectron spectroscopy results confirmed the existence of Ce(3+) and the increased amount of both chemisorbed oxygen and oxygen vacancy after the CeO2 decorated. Compared with pure SnO2 hollow spheres, such composites revealed excellent enhanced sensing properties to ethanol. When the ethanol concentration was 100 ppm, the sensitivity of the CeO2/SnO2 composites was 37, which was 2.65-times higher than that of the primary SnO2 hollow spheres. The sensing mechanism of the enhanced gas sensing properties was also discussed.

  11. Synthesis of Dimethyl Carbonate from Ethylene Carbonate and Methanol Over Nano-Catalysts Supported on CeO2-MgO.

    Science.gov (United States)

    Jun, Jin Oh; Lee, Joongwon; Kang, Ki Hyuk; Song, In Kyu

    2015-10-01

    A series of CeO2(X)-MgO(1-X) (X = 0, 0.25, 0.5, 0.75, and 1.0) nano-catalysts were prepared by a co-precipitation method for use in the synthesis of dimethyl carbonate from ethylene carbonate and methanol. Among the CeO2(X)-MgO(1-X) catalysts, CeO2(0.25)-MgO(0.75) nano-catalyst showed the best catalytic performance. Alkali and alkaline earth metal oxides (MO = Li2O, K2O, Cs2O, SrO, and BaO) were then supported on CeO2(0.25)-MgO(0.75) by an incipient wetness impregnation method with an aim of improving the catalytic performance of CeO2(0.25)-MgO(0.75). Basicity of the catalysts was determined by CO2-TPD experiments in order to elucidate the effect of basicity on the catalytic performance. The correlation between catalytic performance and basicity showed that basicity played an important role in the reaction. Yield for dimethyl carbonate increased with increasing basicity of the catalysts. Among the catalysts tested, Li2O/CeO2(0.25)-MgO(0.75) nano-catalyst with the largest basicity showed the best catalytic performance in the synthesis of dimethyl carbonate.

  12. Synthesis of nano-sized ceria (CeO2 particles via a cerium hydroxy carbonate precursor and the effect of reaction temperature on particle morphology

    Directory of Open Access Journals (Sweden)

    Majid Farahmandjou

    2015-06-01

    Full Text Available Cerium oxide (CeO2 or ceria has been shown to be an interesting support material for noble metals in catalysts designed for emission control, mainly due to its oxygen storage capacity. Ceria nanoparticles were prepared by precipitation method. The precursor materials used in this research were cerium nitrate hexahydrate (as a basic material, potassium carbonate and potassium hydroxide (as precipitants. The morphological properties were characterized by high resolution transmission electron microscopy (HRTEM, scanning electron microscopy (SEM and X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and UV-Vis spectrophotometer. XRD results showed face centered cubic CeO2 nanoparticles for annealed nanoparticles at 1000°C. SEM measurement showed that by increasing the calcinations temperature from 200 to 600°C, the crystallite size decreased from 90 to 28 nm. The SEM results showed that the size of the CeO2 nanoparticles decreased with increasing temperature. The particle size of CeO2 was around 25 nm as estimated by XRD technique and direct HRTEM observation. SEM and TEM studies showed that the morphology of the prepared powder was sphere-like with a narrow size distribution. The sharp peaks in FTIR spectrum determined the purity of CeO2 nanoparticles and absorbance peak of UV-Vis spectrum showed the small band gap energy of 3.26 ev.

  13. Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

    Science.gov (United States)

    Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

    2015-12-21

    A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability.

  14. Effect of CeO2 addition on Ni/Al2O3 catalysts for methanation of carbon dioxide with hydrogen

    Institute of Scientific and Technical Information of China (English)

    Hezhi Liu; Xiujing Zou; Xueguang Wang; Xionggang Lu; Weizhong Ding

    2012-01-01

    The Ni-CeO2/Al2O3 catalysts with a nickel content of 15 wt% prepared via impregnating boehmite were found to be highly active and stable for methanation of carbon dioxide with hydrogen at a H2/CO2 molar ratio of 4.The effects of CeO2 content and reaction temperature on the performance of the Ni-CeO2/Al2O3 catalysts were studied in detail.The results showed that the catalytic performance was strongly dependent on the CeO2 content in Ni-CeO2/Al2O3 catalysts and that the catalysts with 2 wt% CeO2 had the highest catalytic activity among the tested ones at 350 ℃.The XRD and H2-TPR characterizations revealed that the addition of CeO2 decreased the reduction temperature by altering the interaction between Ni and Al2O3,and improved the reducibility of the catalyst.Preliminary stability test of 120 h on stream over the Ni-2CeO2/Al2O3 catalyst at 350 ℃ revealed that the catalyst was much better than the unpromoted one.

  15. Mineralization of volatile organic compounds (VOCs) over the catalyst CuO-Co3O4-CeO2 and its applications in industrial odor control

    KAUST Repository

    Somekawa, Shouichi

    2011-12-01

    Volatile organic compounds (VOCs) present at ppm levels were decomposed over the catalyst CuO-Co3O4-CeO2 (Cu:Co:Ce = 10:45:45 in mol) in an attempt to scale up for industrial odor control. In addition to enhancing the catalytic activity, CuO-Co3O4 and CeO2 helped, respectively, to maintain the strength of the pelleted catalysts and inhibit their sintering. Using toluene as a VOC model compound, kinetic analysis of the total oxidation to carbon dioxide was conducted. The odor emitted from paint-drying processes could be eliminated effectively using CuO-Co3O4-CeO2 (Cu:Co:Ce = 10:45:45) pelleted catalysts (188 ml) in a large-scale system. © 2011 Elsevier B.V. All rights reserved.

  16. Thermodynamic Equilibrium Studies of Nanocrystallite CeO2 Grain Boundaries by High Temperature X-Ray Photoelectron Spectroscopy and Thermal Gravimetric Analysis

    Institute of Scientific and Technical Information of China (English)

    LIU Zhen-Xiang; XIE Kan

    2000-01-01

    Nanostructured CeO2 thin films and powders are studied by high temperature x-ray photoelectron spectroscopy and thermal gravimetric analysis. The results indicate that the surface composition strongly depends on temperature, the surface O/Ce ratio initially increases with increasing temperature, then decreases with the further increase of temperature, the maximum surface O/Ce ratio is at about 300℃ C. The variation of the surface composition with temperature arises from the ion migration, redistribution and transformation between lattice oxygen and gas phase oxygen near the grain boundaries during the thermodynamic equilibrium process. The results also show that CeO2 has a weakly bond oxygen, high oxygen mobility in the bulk and a high molecular dissociation rate at the surface, especially for the sol-gel prepared nanocrystallite CeO2.

  17. CeO2-TiO2 as a visible light active catalyst for the photoreduction of CO2 to methanol

    Institute of Scientific and Technical Information of China (English)

    Hamidah Abdullah; Maksudur R Khan; Manoj Pudukudy; Zahira Yaakob; Nur Aminatulmimi Ismail

    2015-01-01

    The performance of CeO2-TiO2 photocatalyst for the photocatalytic reduction of CO2 into methanol was studied under visi-ble light irradiation. The as-prepared catalysts were characterized for their structural, textural and optical properties using X-ray dif-fraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), nitrogen phy-sisorption analysis, UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The characterization results indicated that the presence of CeO2 stabilized the anatase phase of TiO2, decreased its crystallite size, increased the surface area, reduced the band gap energy and lowered the rate of electron-hole pair recombination. The CeO2-TiO2 photocatalyst showed an increased methanol yield of 18.6 µmol/g under visible light irradiation, compared to the bare TiO2 (6.0 µmol/g).

  18. Preferential oxidation of CO in excess H2 over CeO2/CuO catalyst: Effect of calcination temperature

    Institute of Scientific and Technical Information of China (English)

    Zhiming Gao; Ming Zhou; Hao Deng; Yong Yue

    2012-01-01

    Different from the classical configuration CuO/CeO2 catalyst,the inverse configuration CeO2/CuO catalyst (atomic ratio of Ce/Cu=10/100)was prepared by impregnation method.Five calcination temperatures were selected to investigate the interaction between CeO2 and CuO support.It is found that as calcination temperature increased from 500 to 900 ℃,sintering of CeO2 particles on the support occurred together with the diffusion of a portion of Ce4+ ions into CuO crystals,forming solid solution.Formation of interface complex Ce-O-Cu was suggested by TPR measurements.The catalyst calcined at 700℃ gives the highest activity for preferential oxidation of CO in excess H2 stream.

  19. Removals of aqueous sulfur dioxide and hydrogen sulfide using CeO2-NiAl-LDHs coating activated carbon and its mix with carbon nano-tubes

    KAUST Repository

    Li, Jing

    2015-07-01

    Ce-doped NiAl/layered double hydroxide was coated at activated carbon by urea hydrolysis method (CeO2-NiAl-LDHs/AC) in one pot, which was characterized by X-ray diffraction, infrared spectra, field emission scanning electron microscope and electrochemical techniques. CeO2-NiAl-LDHs/AC shows good uptake for aqueous sulfur dioxide (483.09mg/g) and hydrogen sulfide (181.15mg/g), respectively at 25°C. Meanwhile, the electrochemical removals of aqueous sulfur dioxide and hydrogen sulfide were respectively investigated at the mix of CeO2-NiAl-LDHs/AC and carbon nano-tubes modified homed paraffin-impregnated electrode. Both sulfur dioxide and hydrogen sulfide could be effectively oxidized to sulfuric acid at 1.0V in alkaline aqueous solution. © 2015 Elsevier B.V.

  20. Y2O3-CeO2-ZrO2 Powder Prepared by Co-Precipitation and As-Plasma-Sprayed Coating

    Institute of Scientific and Technical Information of China (English)

    SHAO Gang-qin; ZHANG Wen-xi; HOU Zhong-tao; YUAN Run-zhang

    2004-01-01

    The Y2O3-CeO2-ZrO2 powders were prepared using a co-precipitation process and the corresponding coatings were prepared by plasma spraying. The results show that an optimal composition exists in Y2O3-doped CeO2-ZrO2, but not in CeO2-doped Y2O3-ZrO2. The powders mainly contain tetragonal phase and a trace amount of monoclinic phase. The homogeneity in composition, large agglomerate size, ideal particle size distribution and high flowability were obtained. The as-sprayed coatings are composed of non-transformable tetragonal phase, tz′structure, and resistant to transformation under thermal or mechanical stresses.

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

    Institute of Scientific and Technical Information of China (English)

    Pengbo Jiang; Yongchen Shang; Tiexin Cheng; Yingli Bi; Keying Shi; Shuquan Wei; Guolin Xu; Kaiji Zhen

    2003-01-01

    The decomposition of methane on Ni/α-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/α-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.

  2. Long and short term impacts of CuO, Ag and CeO2 nanoparticles on anaerobic digestion of municipal waste activated sludge.

    Science.gov (United States)

    Ünşar, E Kökdemir; Çığgın, A S; Erdem, A; Perendeci, N A

    2016-02-01

    In this study, long and short term inhibition impacts of Ag, CuO and CeO2 nanoparticles (NPs) on anaerobic digestion (AD) of waste activated sludge (WAS) were investigated. CuO NPs were detected as the most toxic NPs on AD. As the CuO NP concentration increased from 5 to 1000 mg per gTS, an increase in the inhibition of AD from 5.8 to 84.0% was observed. EC50 values of short and long term inhibitions were calculated as 224.2 mgCuO per gTS and 215.1 mgCuO per gTS, respectively. Ag and CeO2 NPs did not cause drastic impacts on AD as compared to CuO NPs. In the long term test, Ag NPs created 12.1% decrease and CeO2 NPs caused 9.2% increase in the methane production from WAS at the highest dosage. FISH imaging also revealed that the abundance of Archaea in raw WAS was similar in short and long term tests carried out with WAS containing Ag and CeO2 NPs. On the other hand, CuO NPs caused inhibition of Archaea in the long term test. Digestion kinetics of WAS containing Ag, CeO2, CuO NPs were also evaluated with Gompertz, Logistic, Transference and First Order models. The hydrolysis rate constant (kH) for each concentration of Ag and CeO2 NPs and the raw WAS was 0.027745 d(-1) while the kH of WAS containing high concentrations of CuO NPs was found to be 0.001610 d(-1).

  3. Synthesis and characterization of reduced graphene oxide decorated with CeO2-doped MnO2 nanorods for supercapacitor applications.

    Science.gov (United States)

    Ojha, Gunendra Prasad; Pant, Bishweshwar; Park, Soo-Jin; Park, Mira; Kim, Hak-Yong

    2017-05-15

    A novel and efficient CeO2-doped MnO2 nanorods decorated reduced graphene oxide (CeO2-MnO2/RGO) nanocomposite was successfully synthesized via hydrothermal method. The growth of the CeO2 doped MnO2 nanorods over GO sheets and reduction of GO were simultaneously carried out under hydrothermal treatment. The morphology and structure of as-synthesized nanocomposite were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman spectroscopy, which revealed the formation of CeO2-MnO2 decorated RGO nanocomposites. The electrochemical performance of as-prepared CeO2-MnO2/RGO nanocomposites as an active electrode material for supercapacitor was evaluated by cyclic voltammetry, charge-discharge, and electrochemical impedance spectroscopy (EIS) methods in 2M alkaline medium. The obtained results revealed that as-synthesized CeO2-MnO2/RGO nanocomposite exhibited higher specific capacitance (648F/g) as compared to other formulations (MnO2/RGO nanocomposites: 315.13 F/g and MnO2 nanorods: 228.5 F/g) at the scan rate of 5mV/s. After 1000 cycles, it retained ∼90.4%, exhibiting a good stability. The high surface area, enhanced electrical conductivity, and good stability possess by the nanocomposite make this material a promising candidate to be applied as a supercapacitor electrode.

  4. Autothermal reforming of methane over Ni catalysts supported over ZrO2-CeO2-Al2O3

    Institute of Scientific and Technical Information of China (English)

    Xiulan Cai; Yuanxing Cai; Weiming Lin

    2008-01-01

    Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by co-precipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated.The Ni-supported catalysts were characterized by XRD, TPR and XPS. The relationship between the structures and catalytic activities of the catalysts was discussed. The results showed that the catalytic activity and stability of the Ni/ZrO2-CeO2-Al2O3 catalyst was better than those of other catalysts with the highest CH4 conversion, H2/CO and H2/COx ratio at 750 ℃. The cat-alyst showed a little deactivation along the reaction time during its 72 h on stream with the mean deactivation rate of 0.08%/h. The catalytic performance of the Ni/ZrO2-CeO2-Al2O3 catalyst was also affected by reaction temperature, nO2: nCH4 molar ratio and nH2O : nCH4 molar ratio. TPR, XRD and XPS measurements indicated that the formation of ZrO2-CeO2 solid solu-tion could improve the dispersion of NiO, and inhibit the formation of NiAl2O4, and thus significantly promoted the catalytic activity of the Ni/ZrO2-CeO2-Al2O3 catalyst.

  5. CO2 reforming of CH4 over CeO2-doped Ni/Al2O3 nanocatalyst treated by non-thermal plasma.

    Science.gov (United States)

    Rahemi, Nader; Haghighi, Mohammad; Babaluo, Ali Akbar; Jafari, Mahdi Fallah; Estifaee, Pooya

    2013-07-01

    Ni/Al2O3 and Ni/Al2O3-CeO2 nanocatalysts have been prepared with impregnation method, treated with non-thermal plasma, characterized and tested for dry reforming of methane. For catalyst characterization, the following techniques have been used: XRD, FESEM, TEM, EDX dot mapping, BET, FTIR, TG-DTG, and XPS techniques. According to XRD and XPS, Ni in all catalysts exists as NiO and NiAl2O4 that existence of NiAl2O4 reveals strong interaction between active phase and support. Catalyst particles had smaller average particle size in plasma treated Ni/Al2O3-CeO2 nanocatalyst with less agglomeration. Homogenous dispersion of active phase, narrower particle size distribution, and uniform morphology has been observed in ceria containing plasma treated catalyst. The plasma treated Ni/Al2O3-CeO2 nanocatalyst showed bigger NiAl2O4/NiO ratio in XPS analysis that is indicative of stronger interaction between Ni and Al2O3 in the presence of CeO2. The dry reforming of methane was carried out at 550-850 degrees C using a mixture of CH4:CO2 (0.5:2). Improved morphology of the plasma treated Ni/Al2O3-CeO2 nanocatalyst, resulted from both CeO2 and plasma treatment, caused higher ability of catalyst in H2 and CO production. Product yield decreased at higher GHSVs, due to the fact that mass transport limitations will be more severe at low residence time, but this reduction would be less noticeable in the plasma treated Ni/Al2O3-CeO2 nanocatalyst. In addition, the plasma treated Ni/Al2O3-CeO2 nanocatalyst can keep the reactivity without deactivation for either CH4 or CO2 conversion better than other investigated catalysts.

  6. Interfacial interaction in monolayer transition metal dichalcogenide/metal oxide heterostructures and its effects on electronic and optical properties: The case of MX2/CeO2

    Science.gov (United States)

    Yang, Ke; Huang, Wei-Qing; Hu, Wangyu; Huang, Gui-Fang; Wen, Shuangchun

    2017-01-01

    Using the density functional theory (DFT), we systematically study the interfacial interaction in monolayer MX2 (M = Mo, W; X = S, Se)/CeO2 heterostructures and its effects on electronic and optical properties. The interfacial interaction in the MX2/CeO2 heterostructures depends largely on chalcogens, and its strength determines the band gap variation and important electronic states at the band edges of the heterostructures. The MX2/CeO2 heterostructures with the same chalcogen have similar absorption spectra, from ultraviolet to near-infrared regions. These results suggest that chalcogens importantly determine the properties of MX2/metal oxide heterostructures.

  7. Facile synthesis of catalytically active CeO2-Gd2O3 solid solutions for soot oxidation

    Indian Academy of Sciences (India)

    D Naga Durgasri; T Vinodkumar; Benjaram M Reddy

    2014-03-01

    CeO2-Gd2O3 oxides were synthesized by a modified coprecipitation method and subjected to thermal treatments at different temperatures to understand their thermal behaviour. The obtained samples were characterized by XRD, BET, TEM, Raman and TPR techniques. Catalytic efficiencies for oxygen storage/release capacity (OSC) and soot oxidation were evaluated by a thermogravimetric (TG) method. XRD and Raman results indicated the formation of Ce0.8Gd0.2O2− (CG) solid solutions at lower calcination temperatures, and TEM studies confirmed nanosized nature of the particles. Raman studies further confirmed the presence of oxygen vacancies and lattice defects in the CG sample. TPR measurements indicated a facile reduction of ceria after Gd3+ addition. Activity studies revealed that incorporation of Gd3+ into the ceria matrix favoured the creation of more structural defects, which accelerates the oxidation rate of soot compared to pure ceria.

  8. Synthesis and characterization of biomorphic CeO2 obtained by using egg shell membrane as template

    Directory of Open Access Journals (Sweden)

    Marija Prekajski

    2014-06-01

    Full Text Available A new technology based on bio-templating approach was proposed in this paper. Egg-shell membrane (ESM has been employed as a natural biotemplate. Fibrous oxide ceramics was prepared by wet impregnation of biological template with water solution of cerium nitrate. The template was derived from membranes of fresh chicken eggs. Repeated impregnation, pyrolysis and final calcination in the range of 600 to 1200 °C in air resulted in template burnout and consolidation of the oxide layers. At low temperatures, the obtained products had structure which corresponded to the negative replication of biological templates. Unique bio-morphic CeO2 microstructures with interwoven networks were synthesized and characterized by scanning electron microscope (SEM and X-ray diffraction (XRD, whereas low-temperature nitrogen adsorption (BET method was used in order to characterize porous properties.

  9. Facile Synthesis of CeO2 Nanospheres%二氧化铈纳米球的合成

    Institute of Scientific and Technical Information of China (English)

    塔娜; 张密林; 李娟; 李华举; 李勇; 申文杰

    2008-01-01

    使用尿素水热法合成了均匀的二氧化铈球型纳米材料. 纳米球是由纳米层以及纳米颗粒所构成的核壳结构,其平均粒径为320 nm, 同时表面主要暴露{111}晶面. 尿素水解所产生的氨气分子为纳米球状结构的形成提供了模板,而生成的碳酸根与氢氧根离子作为铈离子的沉淀剂. 使用氢气程序升温还原技术表征了氧化铈纳米球材料的氧化还原能力,同时以一氧化碳氧化为探针反应研究了其催化性能.%Ceria nanospheres with an average size of 320 nm were prepared by a urea-hydrothermal route. The ceria nanospheres had a core-shell structure constructed by nanoparticles and nanosheets that predominantly exposed the {111} planes. Urea hydrolysis produced CO2-3 and OH- species as precipitation agent and simultaneously produced ammonia bubbles that acted as a structure-directing agent for the formation of the CeO2 nanospheres. The redox properties and catalytic activity of the CeO2 nanospheres were examined by hydrogen temperature-programmed reduction and CO oxidation, respectively.

  10. A TiN0.3/CeO2 photo-anode and its photo-electrocatalytic performance%TiN0.3/CeO2光阳极材料的构筑及其光电催化性能

    Institute of Scientific and Technical Information of China (English)

    崔华楠; 李登; 刘冠涛; 梁振兴; 石建英

    2015-01-01

    A TiN0.3/CeO2 photo‐anode was synthesized by the electro‐deposition of CeO2 on TiN0.3 supported on a Ti substrate. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study its structure and morphology. The crystalline nature of TiN0.3 and CeO2 was confirmed by XRD, and SEM images showed that CeO2 spheres uniformly distributed on the TiN0.3 surface. In ad‐dition to visible light absorption by TiN0.3, UV light was also harvested by the outer CeO2 component on the TiN0.3/CeO2 combined photo‐anode. In the photo‐electrochemical measurement, TiN0.3/CeO2 showed four times higher photo‐current density than TiN0.3 or CeO2, and the photo‐current stabili‐zation was also significantly improved compared to TiN0.3 or CeO2. The specific double‐layer struc‐ture of TiN0.3/CeO2 contributed to its improved photo‐electrocatalytic performance. Electron trans‐fer from CeO2 to TiN0.3 driven by the hetero‐junction and hole consumption by Ce3+ at the TiN0.3/CeO2 interface promoted the separation of electron and hole in the CeO2 layer, which im‐proved the photo‐current generation. Ce3+that existed in CeO2 acted as the adsorption and activa‐tion site for H2O and accelerated the oxidation of H2O on the CeO2 surface, which further led to the high and stable photo‐current density generated in TiN0.3/CeO2. This finding is useful for the design and synthesis of an effective photo‐electrocatalysis material for solar energy conversion.%采用高温氮化法在Ti片基底上生长一层TiN0.3薄膜,进一步利用电化学沉积法在TiN0.3薄膜上生长CeO2,制备了TiN0.3/CeO2复合材料.分别用X射线衍射和扫描电镜研究了复合材料的晶体和形貌结构,用紫外-可见光谱探究了材料的光学吸收性能.结果表明,球状CeO2颗粒均匀地分布在TiN0.3表面;该复合光阳极除了TiN0.3对可见光的吸收外,外层的CeO2同时实现了对紫外光的吸收.光电催化性能研究发现, TiN0.3/CeO2复合光阳极能够显著提高TiN0.3或CeO2的光电流密度,同时增加光电流的稳定性. TiN0.3/CeO2独特的双层结构是其光电催化性能提高的主要原因.在TiN0.3与CeO2界面处异质结构的驱动下, CeO2层中的光生电子迁移至TiN0.3层,而相应的光生空穴在界面处被Ce3+所消耗,从而提高了CeO2层中电子和空穴的分离效率,光电流密度也随之提高;同时,位于CeO2与电解液界面处的Ce3+作为水分子的吸附中心和反应活性中心,加快了界面处水的氧化反应,从而进一步促进了稳定光电流的产生.鉴于TiN0.3/CeO2光阳极材料优良的光电催化性能,其在太阳能光电催化领域具有潜在的应用,对于新型高效光电转化材料的设计与合成具有借鉴作用.

  11. Characterization of sol-gel thin films of TiO2-PbO, TiO2-Bi2O3 and TiO2-CeO2 compositions

    Science.gov (United States)

    Aegerter, Michel A.; La Serra, Eliane R.; Martins Rodrigues, Ana C.; Kordas, George; Moore, Glenn A.

    1990-11-01

    Single and multilayer sol-gel thin films of Ti02-PbO, Ti02-Bi203 and Ti02-CeO2 composition were deposited on glasses using the dip coating technique. The precursors included Ti(OPri)4 chemically modified by acetyl acetone and diluted in PriOH and sols of Pb(OAc)2, Bi(NO3)3 5H20 diluted in acetic acid. The Ti02-Ce02 sol was prepared by mixing Ce NH2 (NO3 )6 in ethanol and then adding Ti (O-iso-C3H7 )4. Structure texture and homogeneity of their main constituants was established by XRD, XPS,SIMS and SEM-EDX techniques as a function of heat treatments.

  12. Effect of Nano CeO2 Addition on the Microstructure and Properties of a Cu-Al-Ni Shape Memory Alloy

    Science.gov (United States)

    Pandey, Abhishek; Jain, Ashish Kumar; Hussain, Shahadat; Sampath, V.; Dasgupta, Rupa

    2016-08-01

    This article deals with the effect of adding nano CeO2 to act as a grain pinner/refiner to a known Cu-Al-Ni shape memory alloy. Elements were taken in a predefined ratio to prepare 300 g alloy per batch and melted in an induction furnace. Casting was followed by homogenization at 1173 K (900 °C) and rolling to make sheets of 0.5-mm thickness. Further, samples were characterized for microstructure using optical and electron microscope, hardness, and different phase studies by X-ray and transformation temperatures by differential scanning calorimetry. X-ray peak broadenings and changes were investigated to estimate the crystallite size, lattice strain, and phase changes due to different processing steps. A nearly uniform distribution of CeO2 and better martensitic structure were observed with increasing CeO2. The addition of CeO2 also shows a visible effect on the transformation temperature and phase formation.

  13. Ionic conductivity ageing behaviour of 10 mol.% Sc2O3–1 mol.% CeO2–ZrO2 ceramics

    DEFF Research Database (Denmark)

    Omar, Shobit; Bonanos, Nikolaos

    2010-01-01

    The long-term ionic conductivity behaviour of samples of zirconia co-doped with 10 mol.% of Sc2O3 and 1 mol.% CeO2 is evaluated in oxidizing and reducing atmospheres at 600 °C. After 3,000 h, the sample kept in reducing atmospheres exhibits 20% loss in the ionic conductivity, while the sample kept...

  14. Comment on 'The characterization of doped CeO2 electrodes in solid oxide fuel cells' by B.G. Pound

    DEFF Research Database (Denmark)

    Ranløv, J.; Poulsen, F.W.; Mogensen, Mogens Bjerg

    1993-01-01

    Electrode tests and ac impedance measurements presented by Pound on Ni, Co and Mn doped CeO2 are reviewed. We find that the stability of solid solutions in the systems of NiO-CeO2 and CoO-CeO2 are improbable and that therefore the interpretation of ac impedance data and electrode tests should...

  15. Stability of uncoated and fulvic acids coated manufactured CeO2 nanoparticles in various conditions: From ultrapure to natural Lake Geneva waters.

    Science.gov (United States)

    Oriekhova, Olena; Stoll, Serge

    2016-08-15

    Understanding the behavior of engineered nanoparticles in natural water and impact of water composition in changing conditions is of high importance to predict their fate once released into the environment. In this study we investigated the stability of uncoated and Suwannee River fulvic acids coated CeO2 manufactured nanoparticles in various environmental conditions. The effect of pH changes on the nanoparticle and coating stability was first studied in ultrapure water as well as the variation of zeta potentials and sizes with time in presence of fulvic acids at environmental pH. Then the stability of CeO2 in synthetic and natural Lake Geneva waters was investigated as a function of fulvic acids concentration. Our results indicate that the adsorption of environmentally relevant concentrations of Suwannee River fulvic acids promotes CeO2 stabilization in ultrapure water as well as synthetic water and that the coating stability is high upon pH variations. On the other hand in natural Lake Geneva water CeO2 NPs are found in all cases aggregated due to the effect of heterogeneous organic and inorganic compounds.

  16. Preparation and characterization of p–n heterojunction CuBi2O4/CeO2 and its photocatalytic activities under UVA light irradiation

    Directory of Open Access Journals (Sweden)

    Abdelkader Elaziouti

    2015-04-01

    Full Text Available CuBi2O4/CeO2 nanocomposites were synthesized by the solid state method and were characterized by a number of techniques such as X-ray diffraction, scanning electron microscopy and UV–Vis diffuse reflectance spectroscopy. The photocatalytic activity of the samples was investigated under UVA light and assessed using Congo red (CR dye as probe reaction. The efficiency of the coupled CuBi2O4/CeO2 photocatalyst was found to be related to the amount of added CuBi2O4 and to the pH medium. The CuBi2O4/CeO2 photocatalyst exhibited the high efficiency as a result of 83.05% of degradation of CR under UVA light for 100 min of irradiation time with 30 wt% of CuBi2O4 at 25 °C and pH 7, which is about 6 times higher than that of CeO2. The photodegradation reactions satisfactorily correlated with the pseudo-first-order kinetic model. The mechanism of the enhanced photocatalytic efficiency was explained by the heterojunction model.

  17. Corrosion of alloy 800H and the effect of surface-applied CeO2 in a sulphidizing/oxidizing/carburizing environment at 700°C

    NARCIS (Netherlands)

    Stroosnijder, M.F.; Guttmann, V.; Fransen, T.; Wit, de J.H.W.

    1990-01-01

    The corrosion behavior of a wrought austenitic Fe-20Cr-32Ni steel, Alloy 800H, was studied in a simulated coal-gasification atmosphere at 700°C for exposure times up to 2500 hr. The influence of preoxidation and CeO2-surface application followed by preoxidation on the corrosion resistance of this ma

  18. Germination and early plant development of 10 plant species exposed to Nano TiO2 and CeO2

    Science.gov (United States)

    Ten agronomic plant species were exposed to different concentrations of nano-TiO2 or CeO2 (0, 250, 500 and 1000 ug/l) and followed to examine effects on germination and early seedling development. For TiO2, cabbage showed increased and corn decreased percent germination, while ...

  19. Controlled synthesis of CeO2 microstructures from 1D rod-like to 3D lotus-like and their morphology-dependent properties

    Science.gov (United States)

    Gong, Jinfeng; Meng, Fanming; Fan, Zhenghua; Li, Huijie

    2016-10-01

    Monodisperse 3D lotus-like CeO2 microstructures have been successfully synthesized via controlling the morphology of CeCO3OH precursors under hydrothermal condition as well as subsequent calcination. The reaction time was systematically investigated. XRD, FT-IR, SEM, TEM, XPS, Raman scattering and Photoluminescence (PL) spectra were employed to characterize the samples. The lotus-like CeO2 hierarchical structures with an average of 4-6 μm are composed of many nanoplates of 100-200 nm in thickness as the petals stacking together to form open flowers and have a fluorite cubic structure. Based on the time-dependent morphology evolution evidences, a nucleation-dissolution-recrystallization mechanism has been proposed to explain the transformation from rod-like structures to lotus-like CeO2 hierarchical structures with the increase of reaction time. It is found that there are Ce3+ ions and oxygen vacancies in surface of samples. The magnetic and photoluminescence measurements indicated that all CeO2 samples exhibit excellent ferromagnetism and optical properties at room temperature, and while increasing the reaction time, the ferromagnetism and optical properties increase more, which can be reasonably explained for the influences of the different morphology of the particles and the concentration of oxygen vacancies and Ce3+ ions. [Figure not available: see fulltext.

  20. Pressure Regulations on the Surface Properties of CeO2 Nanorods and Their Catalytic Activity for CO Oxidation and Nitrile Hydrolysis Reactions.

    Science.gov (United States)

    Li, Jing; Zhang, Zhiyun; Gao, Wei; Zhang, Sai; Ma, Yuanyuan; Qu, Yongquan

    2016-09-07

    Surface properties of nanoscale CeO2 catalysts in terms of the surface Ce(3+) fraction and concentration of oxygen vacancy can affect their catalytic performance significantly. Continual adjustment on surface properties of CeO2 with the morphological preservation has not been realized by synthetic methods. The revisited studies show that surface properties of CeO2 nanorods can be effectively regulated by synthetic pressures while the rodlike morphology is well-preserved. Such phenomena are ascribed to the contact possibility between Ce(3+) species and dissolved O2, which is balanced by the rapidly increased and gradually saturated dissolution/recrystallization rate of Ce(OH)3 and linearly increased concentration of dissolved O2 with the increase of total air pressure or partial pressure of O2. Surface-property-dependent catalytic activity of CeO2 nanorods synthesized under various pressures was also demonstrated in two benchmark reactions-catalytic oxidation of CO and hydrolysis of nitrile. Such a finding of the pressure regulation on the reducible metal oxides provides an effective approach to rationally design novel catalysts for specific reactions, where ceria are supports, promoters, or actives.

  1. Differential genomic effects on canonical signaling pathways by two different CeO2 nanoparticles in HepG2 cells

    Science.gov (United States)

    Differential genomic effects on signaling pathways by two different CeO2 nanoparticles in HepG2 cells. Sheau-Fung Thai1, Kathleen A. Wallace1, Carlton P. Jones1, Hongzu Ren2, Benjamin T. Castellon1, James Crooks2, Kirk T. Kitchin1. 1Integrated Systems Toxicology Divison, 2Resea...

  2. WO3/CeO2/TiO2 Catalysts for Selective Catalytic Reduction of NO(x) by NH3: Effect of the Synthesis Method.

    Science.gov (United States)

    Michalow-Mauke, Katarzyna A; Lu, Ye; Ferri, Davide; Graule, Thomas; Kowalski, Kazimierz; Elsener, Martin; Kröcher, Oliver

    2015-01-01

    WO3/CeO2/TiO2, CeO2/TiO2 and WO3/TiO2 catalysts were prepared by wet impregnation. CeO2/TiO2 and WO3/TiO2 showed activity towards the selective catalytic reduction (SCR) of NO(x) by NH3, which was significantly improved by subsequent impregnation of CeO/TiO2 with WO3. Catalytic performance, NH3 oxidation and NH3 temperature programmed desorption of wet-impregnated WO3/CeO2/TiO2 were compared to those of a flame-made counterpart. The flame-made catalyst exhibits a peculiar arrangement of W-Ce-Ti-oxides that makes it very active for NH3-SCR. Catalysts prepared by wet impregnation with the aim to mimic the structure of the flame-made catalyst were not able to fully reproduce its activity. The differences in the catalytic performance between the investigated catalysts were related to their structural properties and the different interaction of the catalyst components.

  3. Origin of enhanced visible-light photocatalytic activity of transition-metal (Fe, Cr and Co)-doped CeO2: effect of 3 d orbital splitting

    Science.gov (United States)

    Yang, Ke; Li, Dong-Feng; Huang, Wei-Qing; Xu, Liang; Huang, Gui-Fang; Wen, Shuangchun

    2017-01-01

    Enhanced visible-light photocatalytic activity of transition-metal-doped ceria (CeO2) nanomaterials has experimentally been demonstrated, whereas there are very few reports mentioning the mechanism of this behavior. Here, we use first-principles calculations to explore the origin of enhanced photocatalytic performance of CeO2 doped with transition metal impurities (Fe, Cr and Co). When a transition metal atom substitutes a Ce atom into CeO2, t 2g and e g levels of 3 d orbits appear in the middle of band gap owing to the effect of cubic ligand field, and the former is higher than latter. Interestingly, t 2g subset of FeCe (CoCe and CrCe)-Vo-CeO2 splits into two parts: one merges into the conduction band, the other as well as e g will remain in the gap, because O vacancy defect adjacent to transition metal atom will break the symmetry of cubic ligand field. These e g and t 2g levels in the band gap are beneficial for absorbing visible-light and enhancing quantum efficiency because of forbidden transition, which is one key factor for enhanced visible-light photocatalytic activity. The band gap narrowing also leads to a redshift of optical absorbance and high photoactivity. These findings can rationalize the available experimental results and provide some new insights for designing CeO2-based photocatalysts with high photocatalytic performance.

  4. Facile Synthesis of CeO2-LaFeO3 Perovskite Composite and Its Application for 4-(Methylnitrosamino-1-(3-Pyridyl-1-Butanone (NNK Degradation

    Directory of Open Access Journals (Sweden)

    Kaixuan Wang

    2016-04-01

    Full Text Available A facile and environmentally friendly surface-ion adsorption method using CeCO3OH@C as template was demonstrated to synthesize CeO2-LaFeO3 perovskite composite material. The obtained composite was characterized by X-ray diffraction (XRD, fourier transform infrared spectra (FT-IR, field-emission scanning electron microscopy (FE-SEM, transmission electron microscopy (TEM, thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC, N2 adsorption/desorption isotherms and X-ray photoelectron spectra (XPS measurements. The catalytic degradation of nitrosamine 4-(methylnitrosamino-1-(3-pyridyl-1-butanone (NNK was tested to evaluate catalytic activity of the CeO2-LaFeO3 composite. Much better activity was observed for the CeO2-LaFeO3 composite comparing with CeO2 and LaFeO3. These results suggested that perovskite composite materials are a promising candidate for the degradation of tobacco-specific nitrosamines (TSNAs.

  5. Dose-Dependent Effects of CeO2 on Microstructure and Antibacterial Property of Plasma-Sprayed TiO2 Coatings for Orthopedic Application

    Science.gov (United States)

    Zhao, Xiaobing; Liu, Gaopeng; Zheng, Hai; Cao, Huiliang; Liu, Xuanyong

    2015-02-01

    Titanium and its alloys have been used extensively for orthopedic and dental implants. Although these devices have achieved high rates of success, two major complications may be encountered: the lack of osseointegration and the biomaterial-related infection. Accordingly, cerium oxide (CeO2)-doped titanium oxide (TiO2) materials were coated on titanium by an atmospheric plasma spraying (APS) technique. The phase structures, morphologies, and surface chemical states of the obtained coatings were characterized by x-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy techniques. The in vitro antibacterial and cytocompatibility of the materials were studied with Staphylococcus aureus ( S. aureus, ATCC25923) and osteoblast precursor cell line MC3T3-E1. The results indicated that the addition of CeO2 shifts slightly the diffraction peaks of TiO2 matrix to low angles but does not change its rutile phase structure. In addition, the CeO2/TiO2 composite coatings possess dose-dependent corrosion resistance and antimicrobial properties. And doping of 10 wt.% CeO2 exhibits the highest activity against S. aureus, improved corrosion resistance, and competitive cytocompatibility, which argues a promising option for balancing the osteogenetic and antibacterial properties of titanium implants.

  6. Photon management properties of rare-earth (Nd,Yb,Sm)-doped CeO2 films prepared by pulsed laser deposition.

    Science.gov (United States)

    Balestrieri, Matteo; Colis, Silviu; Gallart, Mathieu; Schmerber, Guy; Bazylewski, Paul; Chang, Gap Soo; Ziegler, Marc; Gilliot, Pierre; Slaoui, Abdelilah; Dinia, Aziz

    2016-01-28

    CeO2 is a promising material for applications in optoelectronics and photovoltaics due to its large band gap and values of the refractive index and lattice parameters, which are suitable for silicon-based devices. In this study, we show that trivalent Sm, Nd and Yb ions can be successfully inserted and optically activated in CeO2 films grown at a relatively low deposition temperature (400 °C), which is compatible with inorganic photovoltaics. CeO2 thin films can therefore be efficiently functionalized with photon-management properties by doping with trivalent rare earth (RE) ions. Structural and optical analyses provide details of the electronic level structure of the films and of their energy transfer mechanisms. In particular, we give evidence of the existence of an absorption band centered at 350 nm from which energy transfer to rare earth ions occurs. The transfer mechanisms can be completely explained only by considering the spontaneous migration of Ce(3+) ions in CeO2 at a short distance from the RE(3+) ions. The strong absorption cross section of the f-d transitions in Ce(3+) ions efficiently intercepts the UV photons of the solar spectrum and therefore strongly increases the potential of these layers as downshifters and downconverters.

  7. Influence of calcination temperature on selective catalytic reduction of NOx with NH3 over CeO2-ZrO2-WO3 catalyst

    Institute of Scientific and Technical Information of China (English)

    李军燕; 宋忠贤; 宁平; 张秋林; 刘昕; 李昊; 黄真真

    2015-01-01

    A series of CeO2-ZrO2-WO3 catalysts for the selective catalytic reduction (SCR) of NO with NH3 were prepared by hydro-thermal method. The influence of calcination temperature on the catalytic activity, microstructure, surface acidity and redox behavior of CeO2-ZrO2-WO3 catalyst was investigated using various characterization methods. It was found that the CeO2-ZrO2-WO3 catalyst calcined at 600 ºC showed the best catalytic performance and excellent N2 selectivity, and yielded more than 90% NO conversion in a wide temperature range of 250–500 ºC with a space velocity (GHSV) of 60000 h–1. As the calcination temperature was increased from 400 to 600 ºC, the NO conversion obviously increased, but decreased at higher calcination temperature. The results implied that the higher surface area, the strongest synergistic interaction, the superior redox property and the highly dispersed or amorphous WO3 species contributed to the excellent SCR activity of the CeO2-ZrO2-WO3 catalyst calcined at 600 ºC.

  8. Influence of CeO2 doping amount on property of BCTZ lead-free piezoelectric ceramics sintered at low temperature

    Institute of Scientific and Technical Information of China (English)

    黄新友; 邢仁克; 高春华; 陈志刚

    2014-01-01

    Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) lead-free piezoelectric ceramics co-doped with CeO2 (x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%) and Li2CO3 (0.6 wt.%) were prepared by conventional solid-state reaction method. Influence of CeO2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and other ana-lytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO2 de-creased greatly when Li2CO3 doping amount was 0.6 wt.%;a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li2CO3 and CeO2 and sintered at 1050 °C could also be obtained. The piezoelectric constant (d33), the relative permit-tivity (εr) and the planar electromechanical coupling factor (kp) of BCTZ ceramics doped with Li2CO3 increased firstly and then de-creased, the dielectric loss (tanδ) decreased firstly and then increased and decreased at last when CeO2 doping amount increased. The influence of CeO2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were caused by“soft effect”and “hard effect”piezoelectric additive and causing lattice distortion. When CeO2 doping amount (x) was 0.2 wt.%, the BCTZ ce-ramics doped with Li2CO3 (0.6 wt.%) and sintered at 1050 °C possessed the best piezoelectric property and dielectric property with d33 of 436 pC/N, kp of 48.3%,εr of 3650, tanδof 1.5%.

  9. Colloidal stability of CeO2 nanoparticles coated with either natural organic matter or organic polymers under various hydrochemical conditions

    Science.gov (United States)

    Dippon, Urs; Pabst, Silke; Klitzke, Sondra

    2016-04-01

    The worldwide marked for engineered nanoparticles (ENPs) is growing and concerns on the environmental fate- and toxicity of ENPs are rising. Understanding the transport of ENPs within and between environmental compartments such as surface water and groundwater is crucial for exposition modeling, risk assessment and ultimately the protection of drinking water resources. The transport of ENPs is strongly influenced by the surface properties and aggregation behavior of the particles, which is strongly controlled by synthetic and natural organic coatings. Both, surface properties and aggregation characteristics are also key properties for the industrial application of ENPs, which leads to the development and commercialization of an increasing number of surface-functionalized ENPs. These include metals and oxides such as Cerium dioxide (CeO2) with various organic coatings. Therefore, we investigate CeO2 ENPs with different surface coatings such as weakly anionic polyvinyl alcohol (PVA) or strongly anionic poly acrylic acid (PAA) with respect to their colloidal stability in aqueous matrix under various hydrochemical conditions (pH, ionic strength) and their transport behavior in sand filter columns. Furthermore, we investigate the interaction of naturally occurring organic matter (NOM) with CeO2 ENPs and its effect on surface charge (zeta potential), colloidal stability and transport. While uncoated CeO2 ENPs aggregate at pH > 4 in aqueous matrix, our results show that PAA and PVA surface coatings as well as NOM sorbed to CeO2-NP surfaces can stabilize CeO2 ENPs under neutral and alkaline pH conditions in 1 mM KCl solution. Under slightly acidic conditions, differences between the three particle types were observed. PVA can stabilize particle suspensions in presence of 1 mM KCl at pH > 4.3, PAA at pH >4.0 and NOM at >3.2. While the presence of KCl did not influence particle size of NOM-CeO2 ENPs, CaCl2 at >2 mM lead to aggregation. Further results on the influence of KCl and CaCl2 on aggregation of coated CeO2 ENPs and transport in sand filter columns will be presented.

  10. Identification and quantification of oxygen vacancies in CeO2 nanocrystals and their role in formation of F-centers

    Science.gov (United States)

    Jaffari, G. Hassnain; Imran, Ali; Bah, M.; Ali, Awais; Bhatti, Arshad S.; Qurashi, Umar Saeed; Ismat Shah, S.

    2017-02-01

    In this work we present synthesis and extensive characterization of Cerium oxide (CeO2) nanocrystals. Comparison between the properties of as-prepared and air annealed nanoparticles has been carried out, with a goal to clearly identify the effect of oxygen vacancies on crystal, electronic and band structure. Detail crystal and electronic structural analysis was employed to quantify oxygen vacancies. Structural analysis confirmed that the formation of single phase cubic Fluorite structure for both as-prepared and annealed samples. Crystal and electronic structural studies confirmed that Ce ions exists in two oxidation states, Ce+3 and Ce+4. Concentration of oxygen vacancies was larger in as-synthesis nanocrystal. A drastic decrease in oxygen vacancy concentration was observed for the sample annealed in air at 550 °C. For the as-prepared sample, the Raman allowed F2g mode shifted towards lower wavenumber, exhibiting mode softening with broader and asymmetric peak. Observation of absorption edge revealed presence of 4f band within the band gap. Absorption with different band edge, confirmed different energy position of 4f level for the sample possessing oxygen vacancies. Blue shift of the band edge for as-prepared sample has been discussed in terms of increase in lattice parameter, formation of Ce+3 ions, quantum confinement effect etc. Photoluminescence emission studies revealed presence of F-centers with corresponding energy level located below 4f band as a result of oxygen vacancies. It was found that within the measured experimental energy window, transitions associated by the F-center are mainly associated with 4f0 to 4f1, F++ to 4f1 and 4f0 to F+.

  11. No genotoxicity in rat blood cells upon 3- or 6-month inhalation exposure to CeO2 or BaSO4 nanomaterials.

    Science.gov (United States)

    Cordelli, Eugenia; Keller, Jana; Eleuteri, Patrizia; Villani, Paola; Ma-Hock, Lan; Schulz, Markus; Landsiedel, Robert; Pacchierotti, Francesca

    2017-01-01

    In the course of a 2-year combined chronic toxicity-carcinogenicity study performed according to Organisation for Economic Co-operation and Development (OECD) Test Guideline 453, systemic (blood cell) genotoxicity of two OECD representative nanomaterials, CeO2 NM-212 and BaSO4 upon 3- or 6-month inhalation exposure to rats was assessed. DNA effects were analysed in leukocytes using the alkaline Comet assay, gene mutations and chromosome aberrations were measured in erythrocytes using the flow cytometric Pig-a gene mutation assay and the micronucleus test (applying both microscopic and flow cytometric evaluation), respectively. Since nano-sized CeO2 elicited lung effects at concentrations of 5mg/m(3) (burdens of 0.5mg/lung) in the preceding range-finding study, whereas nano-sized BaSO4 did not induce any effect, female rats were exposed to aerosol concentrations of 0.1 up to 3mg/m(3) CeO2 or 50mg/m(3) BaSO4 nanomaterials (6h/day; 5 days/week; whole-body exposure). The blood of animals treated with clean air served as negative control, whereas blood samples from rats treated orally with three doses of 20mg/kg body weight ethylnitrosourea at 24h intervals were used as positive controls. As expected, ethylnitrosourea elicited significant genotoxicity in the alkaline Comet and Pig-a gene mutation assays and in the micronucleus test. By contrast, 3- and 6-month CeO2 or BaSO4 nanomaterial inhalation exposure did not elicit significant findings in any of the genotoxicity tests. The results demonstrate that subchronic inhalation exposure to different low doses of CeO2 or to a high dose of BaSO4 nanomaterials does not induce genotoxicity on the rat hematopoietic system at the DNA, gene or chromosome levels.

  12. Macroporous graphene capped Fe3O4 for amplified electrochemiluminescence immunosensing of carcinoembryonic antigen detection based on CeO2@TiO2.

    Science.gov (United States)

    Yang, Lei; Zhu, Wenjuan; Ren, Xiang; Khan, Malik Saddam; Zhang, Yong; Du, Bin; Wei, Qin

    2017-05-15

    A novel electrochemiluminescence (ECL) signal-amplified immunosensing strategy was proposed by using gold nanoparticles (Au NPs) functionalized reduced graphene oxide (rGO) capped Fe3O4 (Au-FrGO). In this work, CeO2@TiO2 was prepared by a sol-gel method to wrap CeO2 with TiO2. In the presence of CeO2, CeO2@TiO2 exhibited better ECL activity than TiO2 with peroxydisulfate as coreactant. In addition, FrGO with macroporous structure was synthesized by self-assembly of rGO sheets capped cationic Fe3O4 nanoparticles, exhibiting larger specific surface area than rGO. Due to the low toxicity and magnetism of Fe3O4, FrGO owned more favorable biocompatibility and the application of magnetic-separation simplified the preparation procedure. After hybridizing with Au NPs, FrGO exhibited more excellent electrical conductivity and could immobilize more CeO2@TiO2 and antibodies. Therefore, a novel label-free ECL immunosensor based on Au-FrGO-CeO2@TiO2 was constructed which generated higher ECL response. To investigate the performance of the immunosensor, carcinoembryonic antigen (CEA) was chosen as a model target analyte. Under optimal conditions, the immunosensor had sensitive response to CEA in a wide linear range of 0.01pgmL(-1) to 10ngmL(-1) with a detection limit of 3.28 fg mL(-1). The proposed ECL immunosensor exhibited excellent stability, repeatability and selectivity, which opened another promising avenue for CEA determination in real serum samples.

  13. Chloride salt of conducting polyaniline synthesized in the presence of CeO2: Structural analysis of the core-shell nanocomposite

    Science.gov (United States)

    da Silva, J. S. M.; de Souza, S. M.; Trovati, G.; Sanches, E. A.

    2017-01-01

    Chloride salt of conducting Polyaniline (ES-PANI) was synthesized in the presence of cerium dioxide (CeO2) for structural and morphological evaluation of the resulting core-shell nanocomposite. X-ray Diffraction (XRD), estimative of crystallinity percentage, Le Bail Method, Scanning Electron Microscopy (SEM) and DC electrical conductivity were used for materials characterization. The resulting nanocomposite was constituted of three phases as identified by X-Ray Diffraction: ES-PANI, CeO2 and CeCl3(H2O)7, chloride hepta-hydrate cerium. Crystallinity of ES-PANI and nanocomposite were estimated around 40 and 85%, respectively. XRD patterns were also used to perform the Le Bail Method. This refinement allowed structural characterization of each phase, obtainment of cell parameters and crystallite size and shape. For ES-PANI and CeCl3(H2O)7, crystallites showed a prolate-like shape with an average size of 21 Å and 104 Å, respectively. CeO2 crystallites presented much larger size, as expected, with isotropic average size of 490 Å. SEM images showed that the nanocomposite has a core-shell morphology with both ES-PANI nanofibers and CeCl3(H2O)7 particles coating the CeO2 particles. The polymerization of ES-PANI over the CeO2 particles in order to form the nanocomposite affected the natural chain alignment of the polymer, resulting in better molecular rearrangement and larger crystallites. Finally, measurements of DC electrical conductivity of ES-PANI and nanocomposite have showed values of 1.11 × 10-4 and 2.22 × 10-4 S/cm, respectively. Nanocomposite has showed electrical conductivity 50 times greater than the pure ES-PANI. Thus, in this work we have reported a systematic structural and morphological investigation of PANI/CeO2/CeCl3(H2O)7 core-shell nanocomposite.

  14. [Research on SCR denitrification of MnOx/Al2O3 modified by CeO2 and its mechanism at low temperature].

    Science.gov (United States)

    Guo, Jing; Li, Cai-Ting; Lu, Pei; Cui, Hua-Fei; Peng, Dun-Liang; Wen, Qing-Bo

    2011-08-01

    The Al2O3,which has large specific surface area and is used as carrier,was prepared by sol-gel method in this study. Series catalysts of MnOx, CeO2 plus MnOx supported on Al2O3 by isometric impregnation method. The SCR denitrification experimental conditions were as follows: NH3 as reductive agent, certain gas velocity and suitable ratio of gas mixed was setup. Furthermore, the experiments of BET, XRD and SEM were also carried out respectively in order to obtain physicochemical properties of the prepared catalysts. The experimental results showed that the loading of active component and calcination temperature made a big difference to the catalysts' performance. With appropriate addition of CeO2, MnOx/Al2O3 exhibits better activity and stability. For MnOx/Al2O3, the catalytic activity on NO was greatly influenced by its loaded content, and 7% MnOx/Al2O3 showed superior catalytic activity among the MnOx/Al2O3. The addition of CeO2 could greatly improve the dispersibility of MnOx on the carrier and increase its catalytic activity. The 4% CeO2 addition was the optimum loaded mass precent. Forthermore, 550 degrees C is the best calcination temperature, as MnOx formed different crystalline phases with temperature, at the same time, the addition of CeO2 could affect MnOx crystalline phase. The catalytic mechanism of SCR on NO was also discussed.

  15. Modification of LiCo1/3Ni1/3Mn1/3O2 cathode material by CeO2-coating

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    LiCo1/3Ni1/3Mn1/3O2 was coated by a layer of 1.0 wt% CeO2 via sol-gel method. The bared and coated LiMn1/3Co1/3Ni1/3O2 was characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),cyclic voltammogram (CV) and galvanotactic charge-discharge test. The results show that the coating layer has no effect on the crystal structure,only coating on the surface; the 1.0 wt% CeO2-coated LiCo1/3Ni1/3Mn1/3O2 exhibits better discharge capacity and cycling performance than the bared LiCo1/3Ni1/3Mn1/3O2. The discharge capacity of 1.0 wt% CeO2-coated cathode is 182.5 mAh.g-1 at a current density of 20 mA.g-1,in contrast to 165.8 mAh.g-1of the bared sample. The discharge capacity retention of 1.0 wt% CeO2-coated sample after 12 cycles reaches 93.2%,in comparison with 86.6% of the bared sample. CV results show that the CeO2 coating could suppress phase transitions and prevent the surface of cathode material from direct contact with the electrolyte,thus enhance the electro-chemical performance of the coated material.

  16. Design strategies for P-containing fuels adaptable CeO2-MoO3 catalysts for DeNO(x): significance of phosphorus resistance and N2 selectivity.

    Science.gov (United States)

    Chang, Huazhen; Jong, Min Tze; Wang, Chizhong; Qu, Ruiyang; Du, Yu; Li, Junhua; Hao, Jiming

    2013-10-15

    Phosphorus compounds from flue gas have a significant deactivation effect on selective catalytic reduction (SCR) DeNOx catalysts. In this work, the effects of phosphorus over three catalysts (CeO2, CeO2-MoO3, and V2O5-MoO3/TiO2) for NH3-SCR were studied, and characterizations were performed aiming at a better understanding of the behavior and poisoning mechanism of phosphorus over SCR catalysts. The CeO2-MoO3 catalyst showed much better catalytic behavior with respect to resistance to phosphorus and N2 selectivity compared with V2O5-MoO3/TiO2 catalyst. With addition of 1.3 wt % P, the SCR activity of V2O5-MoO3/TiO2 decreased dramatically at low temperature due to the impairment of redox property for NO oxidation; meanwhile, the activity over CeO2 and CeO2-MoO3 catalysts was improved. The superior NO oxidation activity contributes to the activity over P-poisoned CeO2 catalyst. The increased surface area and abundant acidity sites contribute to excellent activity over CeO2-MoO3 catalyst. As the content of P increased to 3.9 wt %, the redox cycle over CeO2 catalyst (2CeO2 ↔ Ce2O3 + O*) was destroyed as phosphate accumulated, leading to the decline of SCR activity; whereas, more than 80% NOx conversion and superior N2 selectivity were obtained over CeO2-MoO3 at T > 300 °C. The effect of phosphorus was correlated with the redox properties of SCR catalyst for NH3 and NO oxidation. A spillover effect that phosphate transfers from Ce to Mo in calcination was proposed.

  17. Advanced titania buffer layer architectures prepared by chemical solution deposition

    Science.gov (United States)

    Kunert, J.; Bäcker, M.; Brunkahl, O.; Wesolowski, D.; Edney, C.; Clem, P.; Thomas, N.; Liersch, A.

    2011-08-01

    Chemical solution deposition (CSD) was used to grow high-quality (100) oriented films of SrTiO3 (STO) on CSD CaTiO3 (CTO), Ba0.1Ca0.9TiO3 (BCT) and STO seed and template layers. These template films bridge the lattice misfit between STO and the nickel-tungsten (NiW) substrate, assisting in dense growth of textured STO. Additional niobium (Nb) doping of the STO buffer layer reduces oxygen diffusion which is necessary to avoid undesired oxidation of the NiW. The investigated templates offer suitable alternatives to established standard buffer systems like La2Zr2O7 (LZO) and CeO2 for coated conductors.

  18. Structural characteristics of single crystalline GaN films grown on (111) diamond with AlN buffer

    DEFF Research Database (Denmark)

    Pécz, Béla; Tóth, Lajos; Barna, Árpád;

    2013-01-01

    Hexagonal GaN films with the [0001] direction parallel to the surface normal were grown on (111) oriented single crystalline diamond substrates by plasma-assisted molecular beam epitaxy. Pre-treatments of the diamond surface with the nitrogen plasma beam, prior the nucleation of a thin AlN layer,...

  19. Influence of nano-structural feature on electrolytic properties in Y2O3 doped CeO2 system

    Directory of Open Access Journals (Sweden)

    Toshiyuki Mori, John Drennan, Yarong Wang, Graeme Auchterlonie, Ji-Guang Li and Anya Yago

    2003-01-01

    Full Text Available Doped ceria (CeO2 compounds are fluorite type oxides which show oxide ionic conductivity higher than yttria stabilized zirconia, in oxidizing atmosphere. As a consequence of this, considerable interest has been shown in application of these materials for 'low temperature operation (500–650 °C' of solid oxide fuel cells (SOFCs. In this study, YxCe1−xO2−δ (x=0.05, 0.1, 0.15, 0.2 and 0.25 fine powders were prepared using a carbonate co-precipitation method. The relationship between electrolytic properties and nano-structural features in the sintered bodies was examined. The micro-structures of Y0.05Ce0.95O1.975, Y0.15Ce0.85O1.925 and Y0.25Ce0.75O1.875 as representative three specimens have been investigated in more detail with transmission electron microscopy (TEM. The big diffuse scattering was observed in the background of electron diffraction pattern recorded from Y0.15Ce0.85O1.925 and Y0.25Ce0.75O1.875 sintered bodies. This means that the coherent micro-domain with ordered structure is in the micro-structure. While Y0.25Ce0.75O1.875 sintered body with low conductivity and high activation energy has big micro-domains, the micro-domain size in Y0.15Ce0.85O1.925 with high conductivity and low activation energy was much smaller than that of Y0.25Ce0.75O1.875. TEM observation gives us message that the size of coherent micro-domain with ordered structure would closely relate to the electrolytic properties such as conductivity and activation energy in the specimens. It was concluded that a control of micro-domain size in nano-scale in Y2O3 doped CeO2 system was a key for development of high quality solid electrolyte in fuel cell application.

  20. Estudo microestrutural do catalisador Ni/gama-Al2O3: efeito da adição de CeO2 na reforma do metano com dióxido de carbono Microstructural study of Ni/gamma-Al2O3 catalyst: addition effects of CeO2 on carbon dioxide reforming of methane

    Directory of Open Access Journals (Sweden)

    Antoninho Valentini

    2003-10-01

    Full Text Available The carbon dioxide reforming of methane was carried out over nickel catalysts supported on the gamma-Al2O3/CeO2 system prepared by wet impregnation. With the increase of the CeO2 weight in the catalyst, a higher stability was observed in the catalytic activity, together with an excellent resistance to carbon deposition and a better Ni dispersion. The catalysts were characterized by means of surface area measurements, TPR, H2 chemisorption, XRD, SEM, EDX, XPS and TEM. An interaction between Ni and CeO2 was observed to the Ni/CeO2 sample after activation in a H2 atmosphere above 300 ºC. Such behavior has a significantly influence on the catalytic activity.

  1. Zero lattice mismatch and twin-free single crystalline ScN buffer layers for GaN growth on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Lupina, L.; Zoellner, M. H.; Dietrich, B.; Capellini, G. [IHP, Im Technologiepark 25, 15236 Frankfurt, Oder (Germany); Niermann, T.; Lehmann, M. [Technische Universität Berlin, Institut für Optik und Atomare Physik, Straße des 17. Juni 135, 10623 Berlin (Germany); Thapa, S. B.; Haeberlen, M.; Storck, P. [SILTRONIC AG, Hanns-Seidel-Platz 4, 81737 München (Germany); Schroeder, T. [IHP, Im Technologiepark 25, 15236 Frankfurt, Oder (Germany); BTU Cottbus, Konrad-Zuse-Str. 1, 03046 Cottbus (Germany)

    2015-11-16

    We report the growth of thin ScN layers deposited by plasma-assisted molecular beam epitaxy on Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3}/Si(111) substrates. Using x-ray diffraction, Raman spectroscopy, and transmission electron microscopy, we find that ScN films grown at 600 °C are single crystalline, twin-free with rock-salt crystal structure, and exhibit a direct optical band gap of 2.2 eV. A high degree of crystalline perfection and a very good lattice matching between ScN and GaN (misfit < 0.1%) makes the ScN/Sc{sub 2}O{sub 3}/Y{sub 2}O{sub 3} buffer system a very promising template for the growth of high quality GaN layers on silicon.

  2. Study on application of CeO2 and CaCO3 nanoparticles in lubricating oils

    Institute of Scientific and Technical Information of China (English)

    GU Caixiang; LI Qingzhu; GU Zhuoming; ZHU Guangyao

    2008-01-01

    The ceria (CeO2) nanoparticles and calcium carbonate (CaCO3) nanoparticles were chosen as additives of anti-wear and extreme pressure for lubricating oils, and the morphology and sizes of nanoparticles were examined using Transmission Electron Microscope (TEM). The tribological performance of lubricating oils containing combined nanoparticles were determined by four-ball friction and wear tester, and the chemical composition of steel ball with worn surface were analyzed by X-ray Photoelectron Spectrum(XPS). The results showed that the lubricating oils containing combined nanoparticles had good anti-wear and friction reducing effects, and the tribological properties were optimal when WCeO2+CaCO3=0.6%, WCeO2:WCaCO3=1:1. The extreme pressure value increased by 40.25%, the wear spot diameter reduced by 33.5%, and friction coefficient reduced by 32% compared with 40CD oil. The coordinated action of big and small particles made anti-wear and friction reducing effective. Tribological chemical reactions resulting from the friction surface formed metal calcium, metal cerium and oxides film, and they could fill up the concave surface and protect the worn surface.

  3. Photoluminescence and electrochemical properties of transparent CeO2-ZnO nanocomposite thin films prepared by Pechini method

    Science.gov (United States)

    Sani, Z. Khosousi; Ghodsi, F. E.; Mazloom, J.

    2017-02-01

    Nanocomposite thin films of CeO2-ZnO with different molar ratios of Zn/Ce (=0, 0.25, 0.5, 0.75 and 1) were prepared by the Pechini sol-gel route. Various spectroscopic and electrochemical techniques were applied to investigate the films. XRD patterns of all the samples exhibited the peaks corresponding to cubic fluorite structure of ceria and the (101) and (103) peaks of ZnO with hexagonal structure was just observed in the sample with molar ratio of 1. EDS confirmed the presence of constituent of element in the samples. FESEM images of the films showed a surface composed of nanograins. AFM analysis revealed that root mean square roughness was enhanced as molar ratio of Zn/Ce increased. Moreover, fractal dimension of surfaces were calculated by cube counting approach. Optical measurements indicated that the film with molar ratio of 1 has the highest transmission and lowest reflectivity. The optical band gap values varied between 2.95 and 3.42 eV. The compositional dependence of refractive index and extinction coefficient were reported. The UV and blue emission appeared in PL spectra. The highest photoluminescence emission intensity was observed in the 1:1 molar ratio sample. The cyclic voltammetry measurements indicated the highest charge density (9.75 mC cm-2) and diffusion coefficient (3.507 × 10-17 cm2 s-1) belonged to the Ce/Zn (1:1) thin film.

  4. Evidence of translocation and physiological impacts of foliar applied CeO2 nanoparticles on cucumber (Cucumis sativus) plants.

    Science.gov (United States)

    Hong, Jie; Peralta-Videa, Jose R; Rico, Cyren; Sahi, Shivendra; Viveros, Marian N; Bartonjo, Jane; Zhao, Lijuan; Gardea-Torresdey, Jorge L

    2014-04-15

    Currently, most of the nanotoxicity studies in plants involve exposure to the nanoparticles (NPs) through the roots. However, plants interact with atmospheric NPs through the leaves, and our knowledge on their response to this contact is limited. In this study, hydroponically grown cucumber (Cucumis sativus) plants were aerially treated either with nano ceria powder (nCeO2) at 0.98 and 2.94 g/m(3) or suspensions at 20, 40, 80, 160, and 320 mg/L. Fifteen days after treatment, plants were analyzed for Ce uptake by using ICP-OES and TEM. In addition, the activity of three stress enzymes was measured. The ICP-OES results showed Ce in all tissues of the CeO2 NP treated plants, suggesting uptake through the leaves and translocation to the other plant parts. The TEM results showed the presence of Ce in roots, which corroborates the ICP-OES results. The biochemical assays showed that catalase activity increased in roots and ascorbate peroxidase activity decreased in leaves. Our findings show that atmospheric NPs can be taken up and distributed within plant tissues, which could represent a threat for environmental and human health.

  5. Preparation and Properties of Dip-coated CeO2-TiO2 Thin Golden Glass Film

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The golden and ultraviolet-absorbed CeO2-TiO2 film was prepared on soda-lime glass substrate with the thickness of 2 mm via the sol-gel method. The transmission spectra in range of 200 nm-800 nm were measured, and the crystallization, the abrasion and acid resistance were also investigated. The appropriate sol contents and heat-treatment schedule were determined. The results indicate that the appropriate molar ratio of Ce/Ti was 3:5 to 5:6. The ultraviolet-absorbance ability increased with the increase of the Ce/Ti molar ratio, but when the Ce/Ti molar ratio was higher than 1.5, the homogeneity of the film was deteriorated. With the increase of heat-treatment temperature, the main wavelengths of the color of the coated glasses were equal, but the color's saturation decreased; the transmission peaks were the same, while the intensity of the peaks decreased. The roughness, abrasion and acid resistance of the film were also en hanced at the same time. The appropriate heattreatment temperature may be 340 ℃.

  6. CeO2-Co3O4纳米晶粒对甲烷气敏性影响分析%Methane Gas-sensitive Property Analysis Influenced by CeO2-Co3O4 Nanocrystalline

    Institute of Scientific and Technical Information of China (English)

    曹小荣; 胡明江

    2016-01-01

    为了快速准确检测矿井中的甲烷气体浓度,以直接沉淀法制备了不同含量CeO2的CeO2-Co3 O4纳米晶粒。利用掩膜法将制备的CeO2-Co3 O4纳米晶粒镀膜于氧化硅绝缘层表面形成敏感薄膜,采用标准MEMS工艺制作了一种薄膜型甲烷传感器。采用 X 射线衍射仪表征了CeO2-Co3 O4纳米晶粒的相组成和微观形貌,利用全自动程序化学吸附仪分析了CeO2-Co3 O4纳米晶粒对甲烷的吸附机理。在气体传感器静态测试系统上,测试了甲烷传感器灵敏度、湿度、温度、动态响应、抗干扰和长期稳定性等特性。结果表明:以Ce30为敏感薄膜的甲烷传感器灵敏度为98.3%,动态响应时间为11 s,恢复时间为8 s。在矿井中连续使用12个月后,灵敏度衰减了8.5%。表明该甲烷传感器可实现矿井中甲烷气体在线检测。%In order to detect methane concentration in mine quickly and accurately,CeO2-Co3O4 nanocrystalline were pre-pared by direct precipitation method.CeO2-Co3O4 nanocrystalline was deposited onto the insulating layer of silicon oxide surface by mask method.A new film-type methane gas sensor was designed by micro electro mechanical system.The crystalline phase and microstructure of CeO2-Co3 O4 nanocrystalline were displayed using X-ray diffraction ( XRD) and field emission scanning electron microscope ( FE-SEM ) , methane adsorption mechanism of CeO2-Co3 O4 nanocrystalline were analyzed by automatic program chemisorption analyzer.These characteristic tests of methane gas sensors were carried out on the traits of sensitive performance, temperature,relative humidity,dynamic response,interference and long-term stability in gas sensor static test system.The conclu-sion demonstrates that the sensitivity of methane gas sensor based on Ce30 sensitive thin film was 98.3%,the dynamic response time and recover time of methane gas sensor were 11 s and 8 s respectively.The sensitivity of methane gas sensor was attenuated about 8.5%,when methane gas sensor was applied continually in the mine about 12 months.These are ensured that methane gas sensor based on Ce30 sensitive thin film is ideal to detect methane concentration in mine quickly and accurately.

  7. Assessing Hubbard-corrected AM05+U and PBEsol+U density functionals for strongly correlated oxides CeO2 and Ce2O3.

    Science.gov (United States)

    Weck, Philippe F; Kim, Eunja

    2016-09-29

    The structure-property relationships of bulk CeO2 and Ce2O3 have been investigated using AM05 and PBEsol exchange-correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U) and density functional perturbation theory (DFPT+U). Compared with conventional PBE+U, RPBE+U, PW91+U and LDA+U functionals, AM05+U and PBEsol+U describe experimental crystalline parameters and properties of CeO2 and Ce2O3 with superior accuracy, especially when +U is chosen close to its value derived by the linear-response approach. The present findings call for a reexamination of some of the problematic oxide materials featuring strong f- and d-electron correlation using AM05+U and PBEsol+U.

  8. Effects of CeO2 on structure and properties of Ni-Mn-K/bauxite catalysts for water-gas shift reaction

    Institute of Scientific and Technical Information of China (English)

    JIANG Lilong; YE Binghuo; WEI Kemei

    2008-01-01

    Multiple-metal catalysts (Ni-Mn-Ce-K/bauxite) for Water-Gas Shift (WGS) reaction were prepared by impregnation, and the catalytic structure and properties were investigated by N2 physical, XRD, H2-TPR, and CO-TPD. The results indicated that the addition of 7.5% CeO2 improved the activity of the WGS reaction obviously, and also increased the specific surface area and pore volume of the catalysts. The addition of CeO2 decreases the reduction temperature, enhanced the adsorption and activation of H2O, and improved the adsorption content of CO. Besides, active sites were not changed and the number of active sites on catalysts did not increase obviously.

  9. Fabrication and Mechanical Properties of Sm2O3 Doped CeO2 Reinforced Ti3AlC2 Nano Composite

    Institute of Scientific and Technical Information of China (English)

    Jae Ho Han; Sang Whan Park; Young Do Kim

    2004-01-01

    The fabrication process of Sm2O3 doped CeO2 reinforced Ti3AlC2 nano composites including the nano particle dispersion process by a hetero-coagulation process was developed using in-situ synthesis and densification process of Ti3AlC2. The effects of Sm2O2 doped CeO2 nano particles on mechanical properties of Ti3AlC2 were investigated. It was found that the presence of 20SDC nano particles in Ti3AlC2 was very effective to improve the mechanical properties of Ti3AlC2 without spoiling the unique characteristics of Ti3AlC2temary carbide.

  10. Hydrophilic CeO2 nanocubes protect pancreatic β-cell line INS-1 from H2O2-induced oxidative stress

    Science.gov (United States)

    Lyu, Guang-Ming; Wang, Yan-Jie; Huang, Xue; Zhang, Huai-Yuan; Sun, Ling-Dong; Liu, Yan-Jun; Yan, Chun-Hua

    2016-04-01

    Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at the highest dose of 200 μg mL-1 over the time scale of 72 h, while being able to protect INS-1 cells from H2O2-induced cytotoxicity even after protein adsorption. It is also noteworthy that nanoceria with a smaller hydrodynamic radius exhibit stronger antioxidant and anti-apoptotic effects, which is consistent with their H2O2 quenching capability in biological systems. These findings suggest that nanoceria can be used as an excellent antioxidant for controlling oxidative stress-induced pancreatic β-cell damage.Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at the highest dose of 200 μg mL-1 over the time scale of 72 h, while being able to protect INS-1 cells from H2O2-induced cytotoxicity even after protein adsorption. It is also noteworthy that nanoceria with a smaller hydrodynamic radius exhibit stronger antioxidant and anti-apoptotic effects, which is consistent with their H2O2 quenching capability in biological systems. These findings suggest that nanoceria can be used as an excellent antioxidant for controlling oxidative stress-induced pancreatic β-cell damage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00826g

  11. Fabrication of CeO2 by sol-gel process based on microfluidic technology as an analog preparation of ceramic nuclear fuel microspheres

    CERN Document Server

    Ye, Bin; Li, Jiaolong; Zhao, Zichen; Chang, Zhenqi; Serra, Christophe A

    2012-01-01

    Microfluidics integrated with sol-gel processes is introduced in preparing monodispersed MOX nuclear fuel microspheres using nonactive cerium as a surrogate for uranium or plutonium. The detailed information about microfluidic devices and sol-gel processes are provided. The effects of viscosity and flow rate of continuous and dispersed phase on size and size distribution of CeO2 microspheres have been investigated. A comprehensive characterization of the CeO2 microspheres has been conducted, including XRD pattern, SEM, density, size and size distribution. The size of prepared monodisperse particles can be controlled precisely in range of 10{\\mu}m to 1000{\\mu}m and the particle CV is below 3%.

  12. Preparation and Optical Investigations of [(Sr1-xBixTiO3]-[2SiO2B2O3]-[CeO2] Glasses

    Directory of Open Access Journals (Sweden)

    Chandkiram Gautam

    2014-01-01

    Full Text Available We are reporting synthesis and structural and optical investigation of strontium bismuth titanate borosilicate glasses with addition of one mole percent cerium oxide (CeO2. Glasses were synthesized by conventional rapid melt quench method. XRD studies of the glass samples confirm the amorphous nature. Infrared absorption spectra various strontium bismuth titanate borosilicate glass samples having glass system 60[(Sr1-xBixTiO3]-39[2SiO2B2O3]-1[CeO2] (x=0.0,0.1,0.2,0.4 were recorded over a continuous spectral range from 400 to 4000 cm−1. IR spectra were analyzed to determine and differentiate of various vibrational modes in the structural change. Raman spectroscopy of all glass samples was also carried out in the wave number range from 200 to 2000 cm−1.

  13. 纳米CeO2粉体制备方法的研究进展%Prowess in Preparation of Nanometer CeO2

    Institute of Scientific and Technical Information of China (English)

    王瑞芬; 张胤

    2011-01-01

    综述了近年来国内外纳米CeO2粉体的几种主要制备方法及它们的研究进展,其中重点介绍了液相法及其特点,对纳米CeO2的制备技术和发展趋势进行了展望,并指出了今后应重点研究和解决的主要问题.%Several main methods and their progress of studies on the preparation of nanometer CeO2 in resent years were introduced in this paper. The liquid phase methods were reviewed in detail. The future trend of the preparation technology of nanometer CeO2 was predicted and the main problems which should be resolved in the future research were indicated too.

  14. Inverse CeO2/CuO catalyst as an alternative to classical direct configurations for preferential oxidation of CO in hydrogen-rich stream.

    Science.gov (United States)

    Hornés, A; Hungría, A B; Bera, P; López Cámara, A; Fernández-García, M; Martínez-Arias, A; Barrio, L; Estrella, M; Zhou, G; Fonseca, J J; Hanson, J C; Rodriguez, J A

    2010-01-13

    A novel inverse CeO(2)/CuO catalyst for preferential oxidation of CO in H(2)-rich stream (CO-PROX) has been developed on the basis of a hypothesis extracted from previous work of the group (JACS 2007, 129, 12064). Possible separation of the two competing oxidation reactions involved in the process (of CO and H(2), respectively) is the key to modulation of overall CO-PROX activity and is based on involvement of different sites as most active ones for each of the two reactions. Achievement of large size CuO particles and adequate CeO(2)-CuO interfacial configurations in the inverse catalyst apparently allows appreciable enhancement of the catalytic properties of this kind of system for CO-PROX, constituting an interesting alternative to classic direct configurations so far explored for this process. Reasons for such behavior are analyzed on the basis of operando-XRD, -XAFS, and -DRIFTS studies.

  15. Controlled synthesis of Ce(OH)CO3 flowers by a hydrothermal method and their thermal conversion to CeO2 flowers

    Institute of Scientific and Technical Information of China (English)

    Dongen Zhang; Feng Li; Jian Gu; Qing Xie; Shanzhong Li; Xiaobo Zhang; Guiquan Han; Ailing Ying; Zhiwei Tong

    2012-01-01

    Highly uniform Ce(OH)CO3 flowers were successfully prepared in large quantities using a facile hydrothermal approach from the reaction of Ce(NH4)(NO3)4 with CO(NH2)2 at 160 ℃ in a water-N2H4 complex,The influences of the N2H4 content and temperature on flower formation were discussed.CeO2 flowers were prepared by thermal conversion of Ce(OH)CO3 flowers at 500 ℃ in air.Both Ce(OH)CO3 and CeO2 flowers were characterized by X-ray powder diffraction (XRD),and scanning electron microscopy (SEM),The UV-vis adsorption spectrum of the CeO2 flowers showed that the band gap energy (Eg) is 2.66 eV,which is lower than that of bulk ceria.

  16. Thermodynamic Assessment of the ZrO2-CeO2 and ZrO2-CeO1.5 Binary System

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    An optimal set of thermodynamic parameters of the ZrO2-CeO1.5 system has been obtained using phase diagram data by modern CALPHAD (CALculation of PHAse Diagrams) technique. The liquid and other solid solution phases were regarded as substitutional solution. The ordered Zr2Ce2O7 phase was treated as a stoichiometric compound. The ZrO2-CeO2 system has been re-optimized with new reference state. A comparison between the ZrO2-CeO2 system and ZrO2-CeO1.5 system has been made through calculation. With the calculation, the experimental information is well reproduced and a good agreement is obtained.

  17. CeO2掺杂对HfO2栅介质电学特性的影响%Influence of CeO2-Doping on Electrical Properties of HfO2 Gate Dielectrics

    Institute of Scientific and Technical Information of China (English)

    杨萌萌; 屠海令; 张心强; 熊玉华; 王小娜; 杜军

    2012-01-01

    采用磁控共溅射的方法在p-Si(100)衬底上沉积了掺杂和不掺杂CeO2的HfO2薄膜.通过X射线光电子能谱(XPS)研究了薄膜中元素的化学计量比及结合能,制备MOS结构并对漏电流及电容等电学性能进行表征.结果表明,掺入CeO2后,整个体系的氧空位生成能增大,氧空位数目减少,漏电流较纯HfO2下降了一个数量级,满足作为高k材料的要求.%CeO2-doped HfO2(CDH) thin films were deposited on p-Si substrates by RF magnetron co-sputtering. The film thickness was measured by surface profiler. The binding energy of elements was characterized by X-ray photoelectron spectroscopy ( XPS). MOS structures were made to characterize the leakage current and capacitance. XPS analysis of Hf 4f and 01s confirmed that the Hf-0 binding energy increased after doping CeO2. This resulted in the increase of the oxygen vacancy formation energy and the reduction of the concentration of oxygen vacancy. The leakage current density of CDH film was about one order of magnitude lower than that of HfO2 film. CDH film can meet the requirements of high-fc application.

  18. Screening of MgO- and CeO2-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C2+ Hydrocarbons

    Institute of Scientific and Technical Information of China (English)

    Istadi; Nor Aishah Saidina Amin

    2004-01-01

    The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM)have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O22-) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts.The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts,although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.

  19. Influence of Different Subsistence States of CeO2-ZrO2 Mixed Oxides in Catalyst Coating on Catalytic Properties

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The metallic substrate-catalysts with different subsistence states of CeO2-ZrO2 mixed oxides were prepared and the catalytic properties were investigated. The studies on CeO2-ZrO2-V2O5-CuO mixed oxides which were prepared by coprecipitation, show that the doping of V5+ and Cu2+ in CeO2-ZrO2 mixed oxides can enhance the catalytic activity and thermal stability of coating materials. Moreover, different additives were doped in slurries of γ-Al2O3 to investigate the influence of additives on oxidation activity of catalysts. The mixture of ceria-zirconia, alkali metals and other rare earths acting as additives exhibits promotion effect on oxidation activity by optimizing the distribution of oxygen on the surface and in the bulk of ceria species. This mentioned mixture was mixed with γ-Al2O3 and a newly proposed active component to prepare a new catalyst. Afterward, the influence of thermal treatment on the new catalyst were investigated by calcinations at 500, 650, 750, 800, 850 and 900 ℃ for 2 h. The light-off curves of CO and HC show that after being treated at 650~750 ℃, catalysts present the best activity. XRD patterns show that ceria and zirconia species in the newly proposed active component form a phase of extra CeO2-ZrO2 mixed oxides on the surface of catalysts after the thermal treatment at 750 ℃, which has practical value for improving the preparation process and promoting the catalytic properties. Moreover, XPS results imply the existence of Ce1-xPdxO2-σ and Ce1-xPtxO2-σ on the surface of these treated samples, which may show influence on the catalytic activities.

  20. Metabolomic effects in HepG2 cells exposed to CeO2, SiO2 and CuO nanomaterials.

    Science.gov (United States)

    To better assess potential hepatotoxicity of nanomaterials, human liver HepG2 cells were exposed for three days to 5 different CeO2 (either 30 or 100 ug/ml), 3 SiO2 based (30 ug/ml) or 1 CuO (3 ug/ml) nanomaterials with dry primary particle sizes ranging from 15 to 213 nm. Metab...

  1. Low temperature destruction of PCDD/Fs over V2O5-CeO2/TiO2 catalyst with ozone.

    Science.gov (United States)

    Yu, Ming-Feng; Lin, Xiao-Qing; Yan, Mi; Li, Xiao-Dong; Chen, Tong; Yan, Jian-Hua

    2016-09-01

    Catalytic destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans) over V2O5-CeO2/TiO2 catalyst was investigated at a low temperature range of 140-180 °C, in the absence and presence of ozone (200 ppm). Nano-TiO2 support was used to prepare the catalyst by step impregnation method. A stable PCDD/Fs-generating system was established to support the catalytic destruction tests. In the presence of ozone alone, destruction efficiencies of PCDD/Fs are between 32.2 and 43.1 % with temperature increasing from 140 to 180 °C. The activity of V2O5-CeO2/TiO2 catalyst alone on PCDD/Fs destruction is also studied. The increase of temperature from 140 to 180 °C enhances the activity of catalyst with destruction efficiencies increasing from 54.7 to 73.4 %. However, ozone addition greatly enhances the catalytic activity of V2O5-CeO2/TiO2 catalyst on PCDD/Fs decomposition. At 180 °C, the destruction efficiency of PCDD/Fs achieved with V2O5-CeO2/TiO2 catalyst and ozone is above 86.0 %. It indicates that the combined use of ozone and catalyst reduces the reaction temperature of PCDD/Fs oxidation and offers a new method to destroy PCDD/Fs with high destruction efficiency at a low temperature. Furthermore, the destruction efficiencies of 17 toxic PCDD/F congeners, achieved with ozone alone, catalyst alone, and catalyst/ozone are analyzed.

  2. Towards the standardization of nanoecotoxicity testing: Natural organic matter 'camouflages' the adverse effects of TiO2 and CeO2 nanoparticles on green microalgae.

    Science.gov (United States)

    Cerrillo, Cristina; Barandika, Gotzone; Igartua, Amaya; Areitioaurtena, Olatz; Mendoza, Gemma

    2016-02-01

    In the last few years, the emission of CeO2 and TiO2 nanoparticles (NPs) into the environment has been raising concerns about their potential adverse effects on wildlife and human health. Aquatic organisms constitute one of the most important pathways for the entrance of these NPs and transfer throughout the food web, but divergences exist in the experimental data published on their aquatic toxicity. The pressing need for standardization of methods to analyze their ecotoxicity requires aquatic media representing realistic environmental conditions. The present study aimed to determine the usefulness of Suwannee River natural organic matter (SR-NOM) in the assessment of the agglomeration kinetics and ecotoxicity of CeO2 and TiO2 NPs towards green microalgae Pseudokirchneriella subcapitata. SR-NOM alleviated the adverse effects of NPs on algal growth, completely in the case of TiO2 NPs and partially in the case of CeO2 NPs, suggesting a 'camouflage' of toxicity. This behavior has been observed also for other algal species and types of natural organic matter in the literature. Furthermore, SR-NOM markedly increased the stability of the NPs in algal medium, which led to a better reproducibility of the toxicity test results, and provided an electrophoretic mobility similar to that previously reported in various river and groundwaters. Thus, SR-NOM can be a representative sample of what is found in many different ecosystems, and the observed 'camouflage' of the effects of CeO2 and TiO2 NPs on algal cells might be considered as a natural interaction occurring in their standardized ecotoxicological assessment.

  3. Photocatalytic performance of TiO2 catalysts modified by H3PW12O40, ZrO2 and CeO2

    Institute of Scientific and Technical Information of China (English)

    CAI Tiejun; LIAO Yuchao; PENG Zhenshan; LONG Yunfei; WEI Zongyuan; DENG Qian

    2009-01-01

    The binary composite photo-catalysts CeO2/TiO2, ZrO2/TiO2 and the ternary composite photo-catalysts H3PW12O40-CeO2/TiO2,H2PW12O40-ZrO2/TiO2 were prepared by sol-gel method. The catalysts were characterized by thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photocatalyfic elimination of methanol was used as model reaction to evaluate the photocatalytic activity of the composite catalysts under ultraviolet light irradiation. The effects of doped content, activation temperature, time, initial concentration of methanol and gas flow rate on the catalytic activity were investigated. The results showed that after doping a certain amount of CeO2 and ZrO2, crystaniTation process of TiO2 was restrained, particles of catalysts are smaller and more uniform. Doping ZrO2 not only significantly improved the catalytic activity, but also increased thermal stability. Doping H3PW12O40 also enhanced the catalytic activity. The catalytic activities of binary and ternary composite photocatalysts were significantly higher than tin-doped TiO2. The dynamics law of photocatalytic reaction over the binary CeO2/TiO2 and ZrO2/TiO2 catalysts has been studied. The activation energy 15.627 and 15.631 kJ/mol and pre-exponential factors 0.5176 and 0.9899 s-1 over each corresponding catalyst were obtained. This reaction accords to the first order dynamics law.

  4. Contribution of Energetically Reactive Surface Features to the Dissolution of CeO2 and ThO2 Analogues for Spent Nuclear Fuel Microstructures

    OpenAIRE

    Corkhill, C.; Myllykyla, E.; Bailey, D. J.; Thornber, S.M.; Qi, J.; Maldonado, P.; Stennett, M.C.; Hamilton, A.; Hyatt, N.C.

    2014-01-01

    In the safety case for the geological disposal of nuclear waste, the release of radioactivity from the repository is controlled by the dissolution of the spent fuel in groundwater. There remain several uncertainties associated with understanding spent fuel dissolution, including the contribution of energetically reactive surface sites to the dissolution rate. In this study, we investigate how surface features influence the dissolution rate of synthetic CeO2 and ThO2, spent nuclear fuel analog...

  5. CeO2 as the Oxygen Carrier for Partial Oxidation of Methane to Synthesis Gas in Molten Salts: Thermodynamic Analysis and Experimental Investigation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A new technique - the direct partial oxidation of methane to synthesis gas using lattice oxygen in molten salts medium has been introduced. Using CeO2 as the oxygen carrier, thermodynamic data were calculated in the reaction process, and the results indicated that direct partial oxidation of methane to synthesis gas using lattice oxygen of cerium oxide is feasible in theory. In a stainless steel reactor, the effects of temperature and varying amounts of γ-Al2O3 supported CeO2 on CH4 conversion,H2 and CO selectivity, were investigated, respectively. The results show that 10% CeO2/γ-Al2O3 has the maximal reaction activity at a temperature of 865 ℃ and above, the H2/CO ratio in the gas that has been produced reaches 2 and the CH4 conversion, H2 and CO selectivity reached the following percentages: i.e.61%, 89%, and 91% at 870 ℃, respectively. In addition, increase of reaction temperature is favorable for the partial oxidation of methane.

  6. Effects of WOx modification on the activity, adsorption and redox properties of CeO2 catalyst for NOx reduction with ammonia

    Institute of Scientific and Technical Information of China (English)

    Ziran Ma; Duan Weng; Xiaodong WU; Zhichun Si

    2012-01-01

    A series of WO3/CeO2 (WOx/CeO2) catalysts were synthesized by wet impregnation of ammonium metatungstate on a CeO2 support.The resulting solid acid catalysts were characterized by X-ray diffraction (XRD),UV-Vis spectroscopy (UV-Vis),Raman spectroscopy (Raman),in-situ Fourier transform infrared spectroscopy (in-situ FT-IR) of ammonia adsorption,NH3-TPD,H2 temperatureprogrammed reduction (H2-TPR),NH3/NO oxidation and activity measurements for NOx reduction by NH3 (NH3-SCR).The results show that polytungstate (WOx) species are the main species of tungsten oxide on the surface of ceria.The addition of tungsten oxide enhances the Br(ō)nsted acidity of ceria catalysts remarkably and decreases the amount of surface oxygen on ceria,with strong interaction between CeO2 and WOx.As a result,the N2 selectivity of NH3 oxidation and NH3-SCR at high temperatures (> 300℃) is enhanced.Therefore,a wide working temperature window in which NOx conversion exceeds 80% (NOx conversion > 80%) from 200 to 450℃,is achieved over 10 wt.% WOx/CeO2 catalyst.A tentative model of the NH3-SCR reaction route on WOx/CeO2 catalysts is presented.

  7. Experimental study on a room temperature urea-SCR of NO over activated carbon fibre-supported CeO2-CuO.

    Science.gov (United States)

    Jiang, Xiao; Lu, Pei; Li, Caiting; Zeng, Zheng; Zeng, Guangming; Hu, Luping; Mai, Lei; Li, Zhi

    2013-01-01

    In order to establish a desirable method for NO reduction, selective catalytic reduction (SCR) of NO by urea-CeO2/ACF and urea-CeO2-CuO/ACF was carried out at room temperature. The experimental results showed that 10% urea-9% CeO2/ACF could yield the highest NO conversion of 85% among the series of urea-CeO2/ACF prepared. When urea-CeO2-CuO/ACF was compared with urea-CeO2/ACF, it achieved higher NO conversion to a certain degree with the addition of CuO, which was attributed to the synergistic effect between cerium and copper. The effect of the mass ratio of CeO2 and CuO was also observed. The desirable mass ratio of CeO2 and CuO was 1:1, which yielded about 90% NO conversion when ACF was loaded with 10% urea. Furthermore, the influence of O2 concentration and NO concentration was also observed. In this study, NO conversion increased with increasing O2 concentration. In addition, some samples were further characterized by BET, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared methods.

  8. Hot Corrosion Studies of Detonation-Gun-Sprayed NiCrAlY + 0.4 wt.% CeO2 Coated Superalloys in Molten Salt Environment

    Science.gov (United States)

    Kamal, Subhash; Jayaganthan, R.; Prakash, Satya

    2011-08-01

    Rare earth oxide (CeO2) has been incorporated in NiCrAlY alloy and hot corrosion resistance of detonation-gun-sprayed NiCrAlY + 0.4 wt.% CeO2 coatings on superalloys, namely, superni 75, superni 718, and superfer 800H in molten 40% Na2SO4-60% V2O5 salt environment were investigated at 900 °C for 100 cycles. The coatings exhibited characteristic splat globular dendritic structure with diameter similar to the original powder particles. The weight change technique was used to establish corrosion kinetics. X-ray diffraction (XRD), field emission scanning electron microscopy/energy-dispersive analysis (FE-SEM/EDAX), and x-ray mapping techniques were used to analyze the corrosion products. Coated superfer 800H alloy showed the highest corrosion resistance among the examined superalloys. CeO2 was found to be distributed in the coating along the splat boundaries, whereas Al streaks distributed non-uniformly. The main phases observed for the coated superalloys are oxides of Ni, Cr, Al, and spinels, which are suggested to be responsible for developing corrosion resistance.

  9. Heterogeneous synthesis of dimethylhexane-1,6-dicarbamate from 1,6-hexanediamine and methyl carbonate in methanol over a CeO2 catalyst☆

    Institute of Scientific and Technical Information of China (English)

    Yan Cao; Huiquan Li; Xintao Li; Liguo Wang; Ganyu Zhu; Qing Tang

    2015-01-01

    The efficient synthesis of dimethylhexane-1,6-dicarbamate (HDC) from 1,6-hexanediamine (HDA) and methyl carbonate over a series of heterogeneous catalysts (e.g., MgO, Fe2O3, Mo2O3, and CeO2) was investigated. The reaction pathway was confirmed as an alcoholysis reaction through a series of designed experiments. Under optimized conditions, 100%HDA conversion with 83.1%HDCtotal and 16.9%polyurea was obtained using a one-step with high temperature procedure with CeO2 as the catalyst. A new two-step with variable temperature technol-ogy was developed based on the reaction pathway to reduce the polyurea yield. Using the proposed method, the HDCtotal yield reached 95.2%, whereas the polyurea yield decreased to 4.8%. The CeO2 catalyst showed high stability and did not exhibit any observable decrease in the HDC yield or any structural changes after four recycling periods. © 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.

  10. Preparation and characterization of Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst for degradation dye wastewater

    Institute of Scientific and Technical Information of China (English)

    LIU Yan; SUN De-zhi; CHENG Lin; LI Yan-ping

    2006-01-01

    In order to develop a catalyst with high activity for catalytic wet oxidation (CWO) process at room temperature and atmospheric pressure, Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst was prepared by consecutive impregnation method and the prepared parameters were optimized. The structure of the catalyst was characterized by BET, XRF, SEM and XPS technologies, and the actual wastewater was used to investigate the catalytic activity of Fe2O3-CeO2-TiO2/γ-Al2O3 in CWO process. The experimental results showed that the prepared catalyst exhibited good catalytic activity when the doping amount of Ti was 1.0 wt% (the weight ratio of Ti to carriers), and the middle product, CeO2-TiO2/γ-Al2O3, was calcined in 450℃ for 2 h. The CWO experiment for treating actual dye wastewater indicated that the COD, color and TOC of actual wastewater were decreased by 62.23%, 50.12% and 41.26% in 3 h,respectively, and the ratio of BOD5/COD was increased from 0.19 to 0.30.

  11. The use of CeO2-Co3O4 oxides as a catalyst for the reduction of N2O emission

    Directory of Open Access Journals (Sweden)

    Rajska Maria

    2016-01-01

    Full Text Available The morphological characterization of a series of cobalt-cerium oxide composites prepared by the deposition of CeO2 onto Co3O4 powder with a molar ratio of cerium oxide to Co3O4 in the range of 0 to 1 was performed. The powders were also impregnated with a solution of K2CO3 to obtain the theoretical content of potassium atoms 2at·nm−2. To investigate the effect of adding specific amount of CeO2 on the catalytic activity, the X-ray diffraction, SEM-EDX, laser particle size distribution and BET surface area measurements were used. The catalysts were tested through the low-temperature decomposition of nitrous oxide in the temperature range of 50°C to 700°C. The addition of CeO2 and K always moved the temperature of a complete N2O conversion towards lower temperatures (480°C-540°C to 340°C-420°C. The best catalytic properties were shown by the samples in which the ratio of cerium oxide to cobalt oxide ranged from 0.4 to 0.7.

  12. Selective catalytic reduction (SCR) of NO by urea loaded on activated carbon fibre (ACF) and CeO2/ACF at 30 degrees C: the SCR mechanism.

    Science.gov (United States)

    Zeng, Zheng; Lu, Pei; Li, Caiting; Zeng, Guangming; Jiang, Xiao; Zhai, Yunbo; Fan, Xiaopeng

    2012-06-01

    Selective catalytic reduction (SCR) of NO by urea loaded on rayon-based activated carbon fibre (ACF) and CeO2/ACF (CA) was studied at ambient temperature (30 degrees C) to establish a basic scheme for its reduction. Nitric oxide was found to be reduced to N2 with urea deposited on the ACF and CA. When oxygen was present, the greater the amount of loaded urea (20-60%), the greater the NO(x) conversions, which were between 72.03% and 77.30%, whereas the NO(x) conversions were about 50% when oxygen was absent. Moreover, when the urea was loaded on CA, a catalyst containing 40% urea/ACF loaded with 10% CeO2 (UCA4) could yield a NO(x) conversion of about 80% for 24.5 h. Based on the experimental results, the catalytic mechanisms of SCR with and without oxygen are discussed. The enhancing effect of oxygen resulted from the oxidation of NO to NO2, and urea was the main reducing agent in the SCR of loaded catalysts. ACF-C was the catalytic centre in the SCR of NO of ACF, while CeO2 of urea-loaded CA was the catalytic centre.

  13. CeO2对镍基金属陶瓷复合层组织和耐腐蚀性能的影响%Effects of CeO2 on Structure and Corrosion Resistance of Ni-based Metal-Ceramic Coatings

    Institute of Scientific and Technical Information of China (English)

    赵涛; 蔡珣; 王顺兴; 郑世安

    2001-01-01

    利用5kW CO2激光器在5Cr21Mn9Ni4N不锈钢基体表面成功熔覆了含不同CeO2量的镍基金属陶瓷复合层。研究了稀土氧化物CeO2对激光熔覆金属陶瓷复合层显微组织形态和耐腐蚀性能的影响,发现稀土氧化物CeO2能加速碳化钨颗粒的溶解,促使钨与铬形成金属间化合物;激光熔覆镍基金属陶瓷复合层的耐硫酸腐蚀能力显著优于1Cr18Ni9Ti不锈钢;且含0.5%CeO2(质量分数)的激光熔覆层的耐腐蚀能力比含1.5% CeO2(质量分数)和不含CeO2的激光熔覆层都要强。%The Ni-based metal-ceramic coatings on the surface of 5Cr21Mn9Ni4N stainless steel were clad by a 5kW CO2 laser.The effects of CeO2 on structure and corrosion resistance of laser clad Ni-based metal-ceramic coatings were investigated.The studies revealed that CeO2 could accelerate the dissolution of tungsten carbide particles and made the formation of Cr-W intermetallic compound.Compared with steel 1Cr18Ni9Ti,the corrosion resistance of the laser clad Ni-based metal-ceramic coatings was raised remarkably and the corrosion resistance of the coatings with 0.5wt% CeO2 was better than that of the coatings with 1.5wt% CeO2 and without CeO2.

  14. Modeling of a CeO2 thermochemistry reduction process for hydrogen production by solar concentrated energy

    Science.gov (United States)

    Valle-Hernández, Julio; Romero-Paredes, Hernando; Arancibia-Bulnes, Camilo A.; Villafan-Vidales, Heidi I.; Espinosa-Paredes, Gilberto

    2016-05-01

    In this paper the simulation of the thermal reduction for hydrogen production through the decomposition of cerium oxide is presented. The thermochemical cycle for hydrogen production consists of the endothermic reduction of CeO2 at high temperature, where concentrated solar energy is used as a source of heat; and of the subsequent steam hydrolysis of the resulting cerium oxide to produce hydrogen. For the thermochemical process, a solar reactor prototype is proposed; consisting of a cubic receptacle made of graphite fiber thermally insulated. Inside the reactor a pyramidal arrangement with nine tungsten pipes is housed. The pyramidal arrangement is made respect to the focal point where the reflected energy is concentrated. The solar energy is concentrated through the solar furnace of high radiative flux. The endothermic step is the reduction of the cerium oxide to lower-valence cerium oxide, at very high temperature. The exothermic step is the hydrolysis of the cerium oxide (III) to form H2 and the corresponding initial cerium oxide made at lower temperature inside the solar reactor. For the modeling, three sections of the pipe where the reaction occurs were considered; the carrier gas inlet, the porous medium and the reaction products outlet. The mathematical model describes the fluid mechanics; mass and energy transfer occurring therein inside the tungsten pipe. Thermochemical process model was simulated in CFD. The results show a temperature distribution in the solar reaction pipe and allow obtaining the fluid dynamics and the heat transfer within the pipe. This work is part of the project "Solar Fuels and Industrial Processes" from the Mexican Center for Innovation in Solar Energy (CEMIE-Sol).

  15. Surface Acidity/Basicity and Catalytic Reactivity of CeO2/γ-Al2O3 Catalysts for the Oxidative Dehydrogenation of Ethane with Carbon Dioxide to Ethylene

    Institute of Scientific and Technical Information of China (English)

    Xin Ge; Shenghua Hu; Qing Sun; Jianyi Shen

    2003-01-01

    Dehydrogenation of ethane to ethylene in CO2 was investigated over CeO2/γ-Al2O3 catalysts at 700 ℃ in a conventional flow reactor operating at atmospheric pressure. XRD, BET and microcalorimetric adsorption techniques were used to characterize the structure and surface acidity/basicity of the CeO2/γ-Al2O3 catalysts. The results show that the surface acidity decreased while the surface basicity increased after the addition of CeO2 to γ-Al2O3. Accordingly, the activity of the hydrogenation reaction of CO2 increased, which might be responsible for the enhanced conversion in the dehydrogenation of ethane to ethylene. The highest ethane conversion obtained was about 15% for the 25%CeO2/γ-Al2O3. The selectivity to ethylene was high for all the CeO2, γ-Al2O3 and CeO2/γ-Al2O3 catalysts.

  16. Soot combustion over Ce1-xFexO2-δ and CeO2/Fe2O3 catalysts: Roles of solid solution and interfacial interactions in the mixed oxides

    Science.gov (United States)

    Li, Hongcheng; Li, Kongzhai; Wang, Hua; Zhu, Xing; Wei, Yonggang; Yan, Dongxia; Cheng, Xianming; Zhai, Kang

    2016-12-01

    Two series of CeO2-Fe2O3 catalysts (CeO2-based and Fe2O3-supported oxides) with varying composition were synthesized by a hydrothermal method and characterized using various techniques. The comparison on the activity and thermal stability of different catalysts for low-temperature soot oxidation was also performed. The presence of both Ce-Fe-O solid solution and CeO2-Fe2O3 interaction were observed over the two types of catalysts. The oxygen vacancy in the solid solution is the crucial active site to facilitating the soot combustion over the CeO2-based samples. Small CeO2 nanoparticles are well dispersed on the Fe2O3-supported catalysts, which results in the formation of Fe-O-Ce species due to the strong CeO2-Fe2O3 interaction. The Fe-O-Ce species could achieve the coupling of the Ce4+-Ce3+ and Fe3+-Fe2+ couples in the CeO2-Fe2O3 interface, which is also identified as an active species for catalytic soot oxidation. The concentration of oxygen vacancy is closely related to the content of iron in ceria lattice, while the formation of Fe-O-Ce species strongly relies on the particle size of CeO2. It is also found that the oxygen vacancy is more active than the Fe-O-Ce species for soot oxidation, but it is very easy to decompose at high temperature, resulting in obvious deactivation of catalysts. By contrast, the Fe-O-Ce species is very stable under high-temperature treatments. For the fresh samples, the CeO2-based and Fe2O3-supported catalysts showed comparable catalytic activity. After long term aging at 800 °C, the loss on activity over the CeO2-based catalyst (Ce-Fe-O solid solution) is much higher than that over the Fe2O3-supported sample. The Fe2O3-supported catalysts are more suitable for practical application than the Ce-Fe-O solid solution.

  17. Analysis of Single Event Effect on Buffer CELL Based on TCAD Simulation%基于TCAD模拟的Buffer单粒子效应解析分析

    Institute of Scientific and Technical Information of China (English)

    杜明; 邹黎; 李晓辉; 邱恒功; 邓玉良

    2014-01-01

    For semiconductor devices and ICs,the essence of radiation effect is a series of physical process including the generation and recombination of electron-hole pairs,the transmission and collection of charge,the interface state and accumulation of oxide trapped charge. Several factors might affect the physical process,such as the size of the pull-up compensating MOSFET,the incidence angle of the heavy ion,the substrate concentration of the device. This paper simulates how these key variables influence on the single event effect of the Buffer cell using mixed-mode TCAD simulations. Finally the experiment result approach to the real scene.%半导体器件和集成电路的辐射效应,其本质就是电子空穴对的产生和复合、电荷的传输与收集、界面态和氧化层陷阱电荷积累等一系列的物理过程。这些物理过程会受到各种因素的影响,例如上拉补偿管的尺寸、重离子入射角度、器件的外延层浓度等。使用TCAD器件/电路混合模式仿真了以上这些关键变量,同时分析了以上效应对对Buffer电路单粒子效应的影响。最终实验结果证明该模拟方法接近于真实情景。

  18. Electrochemical degradation of reactive brilliant red X-3B with the (CeO2/C)-β-PbO2-PTFE composite electrode

    Institute of Scientific and Technical Information of China (English)

    孙鹏哲; 陈东辉

    2016-01-01

    The (CeO2/C)-β-PbO2-PTFE composite electrodes modified by graphite powder, cerium oxide powder, polytetrafluoro-ethylene (PTFE) and the homemadeβ-PbO2 powder were prepared by the high pressure molding technique. The X-ray diffraction (XRD) was used to test the purity of the homemadeβ-PbO2 powder. The surface structure and electrical property of electrodes were characterized by using scanning electron microscopy (SEM) and the cyclic voltammetry curves (CV). Those images indicated that in electrolysis the (CeO2/C)-β-PbO2-PTFE composite electrodes had higher activity than theβ-PbO2-PTFE electrodes, as good as the excellent catalytic performance. In the electrode system the composite electrodes were applied to treat reactive brilliant red (RBR) X-3B solution and we studied the degradation influence factors and the reaction mechanism. The results showed that the electrode system was well in treating RBR X-3B solution with the 20%(CeO2/C)-β-PbO2-PTFE composite electrodes at the initial 100 mg/L RBR X-3B concentration, Na2SO4concentration of 0.35 mol/L, the constant current density of 30 mA/cm2 and electrolyte pH=2. Af-ter electrolytic time of 90 min, the maximum decolorization and chemical oxygen demand (COD) removal rates reached 88.92% and 54.54%. And the decolorization rate of RBR X-3B was in conformity with pseudo-first-order kinetics equation. The RBR X-3B deg-radation mechanism in the electrochemical oxidation system was used with LC-MS to analyze the possible intermediates and degra-dation pathway.

  19. Effects of CeO_2 nanoparticles on microstructure and properties of laser cladded NiCoCrAlY coatings

    Institute of Scientific and Technical Information of China (English)

    王宏宇; 左敦稳; 黎向锋; 陈康敏; 黄铭敏

    2010-01-01

    CeO2 nanoparticles(nano-CeO2p) were added into laser cladded NiCoCrAlY coatings on Ni-based superalloy substrate to improve the microstructure and properties.Scanning electron microscope(SEM),X-ray diffractometer(XRD),micro-hardness tester,and heat treatment furnace were employed to investigate their morphologies,phases,micro-hardness and thermal shock resistance,compared with the coating without nanoparticles added.The results showed that the microstructure and properties of the coatings with the addition ...

  20. A new approach of CeO2 and La2O3 effects on the three-way catalysts containing low precious metals

    Institute of Scientific and Technical Information of China (English)

    WANG, Wen-Dong; ZHANG, Xiao-Peng; MENG, Ming; YU, Shou-Ming; FU, Yi-Lu; LIN, Pei-Yan

    2000-01-01

    A series of three-way catalysts (TWCs), containing a small amount of precious metals ( PMs, including Pt, Pd and Rh ) and a large amount of promoters CeO2 and La2O3, were pre pared with different precursor compotmds and various doped mtaners. Crystal phases, dispersion of cerium and lan thamun, textural structure and thermal stability of the cata lysts were investigated by XRD, XPS and pore parameters de termination. The catalytic performance was studied by the measurements of CO, C3H6 and NO conversions on depen dence of temperature at stoichimetric nunber point (S = 1.00), and from S=0.75 to 1.30 at 280℃C or 340℃C for fresh or aged samples, respectively. The correlation between the catalytic performance and the characteristics of fresh and aged samples were discussed. The results show that the sampie, in which CeO2 and La2Os are doped with mixed oxide powders, possesses poor dispersion and less thermal stability, and the conversions of NO and C3H6 are apparently lower than those of the samples aged at 850℃C. The main reason is due to the ianthamum enriclument on the surface. The precious metals and cerium may be covered and enveloped, and the PMs lo cated on the internal microporous su-face where no cerium and lanthanum exist, are easier to sinter and oxidize. For the sample doped with La(NO3)3 and Ce(NO3)3 aqueous solu tions, high dispersion and thermal stable CeO2-La2O3 solid so lution on all the surface of microporous γ-Al2O3 is identified. The solid solution CeO2-La2O3 also possessed high dispersion in the sample doped with La2O3 powder and Ce(NO3)3 aque ous soltion The last two aged samples keep higher NO eon version at S>1 region.

  1. CHx adsorption (x = 1-4) and thermodynamic stability on the CeO2(111) surface: A first-principles investigation

    KAUST Repository

    Fronzi, Marco

    2014-01-01

    We present an ab initio investigation of the interaction between methane, its dehydrogenated forms and the cerium oxide surface. In particular, the stoichiometric CeO2(111) surface and the one with oxygen vacancies are considered. We study the geometries, energetics and electronic structures of various configurations of these molecules adsorbed on the surface in vacuum, and we extend the analysis to realistic environmental conditions. A phase diagram of the adsorbate-surface system is constructed and relevant transition phases are analyzed in detail, showing the conditions where partial oxidation of methane can occur. © 2014 The Royal Society of Chemistry.

  2. Visible Light Photocatalytic Activity of CeO2-ZnO-TiO2 Composites for the Degradation of Rhodamine B

    OpenAIRE

    Prabhu, S.; Viswanathan, T.; Jothivenkatachalam, K.; Jeganathan, K.

    2014-01-01

    TiO2 plays a significant role in many applications including solar cell. Consecutively to absorb the low-energy radiation, it is very much essential to tune the optical property of TiO2. We fabricated CeO2-ZnO-TiO2 semiconductor composites by sol-gel method and achieved the absorption of lower energy radiation. The prepared composites were characterized by TG-DTA, UV-DRS, XRD, AFM, TEM and FESEM techniques. The particle and crystalline size of the composites was calculated using FESEM and XRD...

  3. The role of the cationic Pt sites in the adsorption properties of water and ethanol on the Pt4/Pt(111) and Pt4/CeO2(111) substrates: A density functional theory investigation

    Science.gov (United States)

    Seminovski, Yohanna; Tereshchuk, Polina; Kiejna, Adam; Da Silva, Juarez L. F.

    2016-09-01

    Finite site platinum particles, Ptn, supported on reduced or unreduced cerium oxide surfaces, i.e., CeO2-x(111) ( 0 CeO2-x has been improved in the last years; however, the identification of the active sites on the Ptn/CeO2-x(111) substrates is still far from complete. In this work, we applied density functional theory based calculations with the addition of the on-site Coulomb interactions (DFT+U) for the investigation of the active sites and the role of the Pt oxidation state on the adsorption properties of water and ethanol (probe molecules) on four selected substrates, namely, Pt(111), Pt4/Pt(111), CeO2(111), and Pt4/CeO2(111). Our results show that water and ethanol preferentially bind in the cationic sites of the base of the tetrahedron Pt4 cluster instead of the anionic lower-coordinated Pt atoms located on the cluster-top or in the surface Ce (cationic) and O (anionic) sites. The presence of the Pt4 cluster contributes to increase the adsorption energy of both molecules on Pt(111) and CeO2(111) surfaces; however, its magnitude increases less for the case of Pt4/CeO2(111). Thus, the cationic Pt sites play a crucial role in the adsorption properties of water and ethanol. Both water and ethanol bind to on-top sites via the O atom and adopt parallel and perpendicular configurations on the Pt(111) and CeO2(111) substrates, respectively, while their orientation is changed once the Pt4 cluster is involved, favoring H binding with the surface sites.

  4. Hybrid solar cells based on MEH-PPV and thin film semiconductor oxides (TiO2, Nb2O5, ZnO, CeO2 and CeO2–TiO2): Performance improvement during long-time irradiation

    DEFF Research Database (Denmark)

    Lira-Cantu, M.; Krebs, Frederik C

    2006-01-01

    prepared as bi-layers of thin film semiconducting oxides (TiO2, Nb2O5, ZnO, CeO2-TiO2 and CeO2) and the polymer MEH-PPV, with a final device configuration of ITO/ Oxide(thin) (film)/MEH-PPV/Ag. The oxides were prepared as thin transparent films from sol-gel solutions. The photovoltaic cells were studied......Performance improvement of hybrid solar cells (HSC) applying five different thin film semiconductor oxides has been observed during long-time irradiation in ambient atmosphere. This behavior shows a direct relation between HSC and oxygen content from the environment. Photovoltaic devices were...... with TiO2 thin films showed the best performance with maximum V-oc as high as -0.74V and I-sc of 0.4mA/cm(2). Solar decay analyses showed that the devices require a stabilization period of several hours in order to reach maximum performance. In the case of TiO2, Nb2O5 and CeO2-TiO2, the maximum current...

  5. Thermal measurements and computational simulations of three-phase (CeO2-MgAl2O4-CeMgAl11O19) and four-phase (3Y-TZP-Al2O3-MgAl2O4-LaPO4) composites as surrogate inert matrix nuclear fuel

    Science.gov (United States)

    Angle, Jesse P.; Nelson, Andrew T.; Men, Danju; Mecartney, Martha L.

    2014-11-01

    This study investigates the temperature dependent thermal conductivity of multiphase ceramic composites for simulated inert matrix nuclear fuel. Fine grained composites were made of CeO2-MgAl2O4-CeMgAl11O19 or 3Y-TZP-Al2O3-MgAl2O4-LaPO4. CeO2 and 3Y-TZP are used as UO2 surrogates due to their similar structures and low thermal conductivities. Laser flash analysis from room temperature to 1273 K (1000 °C) was used to determine the temperature dependent thermal conductivity. A computational approach using Object Oriented Finite Element Analysis Version 2 (OOF2) was employed to simulate the composite thermal conductivity based on the microstructure. Observed discrepancies between experimental and simulated thermal conductivities at low temperature may be due to Kapitza resistance; however, there is less than 3% deviation between models and experiments above 673 K (400 °C) for both compositions. When the surrogate phase was replaced with UO2 in the computational model for the four-phase composite, a 12-16% increase in thermal conductivity resulted compared to single phase UO2, in the range of 673-1273 K (400-1000 °C). This computational approach may be potentially viable for the high-throughput evaluation of composite systems and the strategic selection of inert phases without extensive sample fabrication during the initial development stages of composite nuclear fuel design.

  6. Surface reactive species on MnOx(0.4)-CeO2 catalysts towards soot oxidation assisted with pulse dielectric barrier discharge

    Institute of Scientific and Technical Information of China (English)

    付名利; 林俊敏; 朱文波; 吴军良; 陈礼敏; 黄碧纯; 叶代启

    2014-01-01

    MnOx(0.4)-CeO2 was investigated for soot oxidation assisted with a pulse dielectric barrier discharge (DBD). The catalysts were evaluated and characterized with TPO (temperature programmed oxidation), X-ray diffraction (XRD), Raman and X-ray photo-electron spectroscopy (XPS). The ignition temperature Ti for soot oxidation decreased from 240.8 to 216.4 ºC with the increase of the pulse DBD frequencies from 50 to 400 Hz, lower than that of the case without pulse DBD present (253.4 ºC). The results of XRD, Raman and XPS agreed well with the TPO activities of MnOx(0.4)-CeO2 towards soot oxidation. More solid solution of ceria and manganese, and surface reactive species including O2-, O-and Mn4+were responsible for the enhancement of soot oxidation due to pulse DBD injection in the present study. For solid solution favors to the activation and transformation of those species, which are be-lieved to be involved in the soot oxidation in a hybrid catalysis-plasma.

  7. Synergistic effect between MnO and CeO2 in the physical mixture:Electronic interaction and NO oxidation activity

    Institute of Scientific and Technical Information of China (English)

    吴晓东; 于海宁; 翁端; 刘爽; 樊俊

    2013-01-01

    MnO and CeO2 powders were mechanically mixed by a spatula and by milling to obtain loose-contact and tight-contact mixed oxides, respectively. The monoxides and their physical mixtures were characterized by X-ray diffraction (XRD), Brun-auer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), Raman, O2 temperature-programmed desorption (O2-TPD), H2 temperature-programmed reduction (H2-TPR) and NO temperature-programmed oxidation (NO-TPO). The MnOx-CeO2 solid solu-tions did not form without any calcination process. The oxidation state of manganese tended to increase while the ionic valence of ce-rium decreased in the mixed oxides, accompanied with the formation of oxygen vacancies. This long-ranged electronic interaction occured more significantly in the tight-contact mixture of MnO and CeO2. The formation of more Mn4+and oxygen vacancies pro-moted the catalytic oxidation of NO in an oxygen-rich atmosphere.

  8. Dispersion state of CuO on CeO2——An incorporation model for the interaction between metal oxide and oxide support

    Institute of Scientific and Technical Information of China (English)

    董林; 金永漱; 陈懿

    1997-01-01

    XRD and XPS are used to study the dispersion state of CuO on ceria surface.The dispersion capacity values of CuO measured by the two methods are consistent,which are of 1.20 mmol CuO/100 m CeO2.In addition,the results reveal that highly dispersed Cu2 + ions are formed at low CuO loadings and that increasing the CuO content to a value higher than its dispersion capacity produces crystalline CuO after the surface vacant sites on CeO2 are filled.The atomic composition of the outermost layer of the CuO/CeO2 samples has been probed by using static secondary ion mass spectroscopy (SSIMS),and the ratios of Cu/Ce are found to be 0.93 and 0.46 for the 1.22 and 0 61 mmol CuO/CeO2 samples respectively.Temperature-programmed reduction (TPR) profile with two reduction peaks at 156 and 16513 suggests that the reduction of highly dispersed Cu2+ ions consists of two steps and is easier than that of CuO crystallites,in which the TPR profile has only one reduction peak at about 249℃.The above experimental results are in

  9. CeO2-TiO2 catalysts for catalytic oxidation of elemental mercury in low-rank coal combustion flue gas.

    Science.gov (United States)

    Li, Hailong; Wu, Chang-Yu; Li, Ying; Zhang, Junying

    2011-09-01

    CeO(2)-TiO(2) (CeTi) catalysts synthesized by an ultrasound-assisted impregnation method were employed to oxidize elemental mercury (Hg(0)) in simulated low-rank (sub-bituminous and lignite) coal combustion flue gas. The CeTi catalysts with a CeO(2)/TiO(2) weight ratio of 1-2 exhibited high Hg(0) oxidation activity from 150 to 250 °C. The high concentrations of surface cerium and oxygen were responsible for their superior performance. Hg(0) oxidation over CeTi catalysts was proposed to follow the Langmuir-Hinshelwood mechanism whereby reactive species from adsorbed flue gas components react with adjacently adsorbed Hg(0). In the presence of O(2), a promotional effect of HCl, NO, and SO(2) on Hg(0) oxidation was observed. Without O(2), HCl and NO still promoted Hg(0) oxidation due to the surface oxygen, while SO(2) inhibited Hg(0) adsorption and subsequent oxidation. Water vapor also inhibited Hg(0) oxidation. HCl was the most effective flue gas component responsible for Hg(0) oxidation. However, the combination of SO(2) and NO without HCl also resulted in high Hg(0) oxidation efficiency. This superior oxidation capability is advantageous to Hg(0) oxidation in low-rank coal combustion flue gas with low HCl concentration.

  10. Hydrocracking of cumene over Ni/Al 2O 3 as influenced by CeO 2 doping and γ-irradiation

    Science.gov (United States)

    El-Shobaky, G. A.; Doheim, M. M.; Ghozza, A. M.

    2004-01-01

    Cumene hydrocracking was carried out over pure and doped Ni/Al 2O 3 solids and also, on these solids after exposure to different doses of γ-rays between 0.4 and 1.6 MGy. The dopant concentration was varied between 1 and 4 mol% CeO 2. Pure and doped samples were subjected to heat treatment at 400°C and cumene hydrocracking reaction was carried out using various solids at temperatures between 250°C and 400°C by means of micropulse technique. The results showed that both CeO 2 doping and γ-irradiation of the investigated system brought about an increase in its specific surface area. γ-irradiation of pure samples increased their catalytic activities effectively. However, the doping caused a decrease in the catalytic activity. γ-irradiation of the doped samples brought about a net decrease in the catalytic activity. The catalytic reaction products over different investigated solids were ethylbenzene as a major product together with different amounts of toluene, benzene and C 1-C 3 gaseous hydrocarbons. The selectivity towards the formation of various reaction products varies with the reaction temperature, doping and γ-irradiation.

  11. Viscous properties of new mould flux based on aluminate systemwith CeO2 for continuous casting of RE alloyed heat resistant steel

    Institute of Scientific and Technical Information of China (English)

    QI Jie; LIU Chengjun; LI Chunlong; JIANG Maofa

    2016-01-01

    The conventional mould fluxes can not be applied to the continuous casting of RE alloyed heat resistant steel, because se-vere slag-metal interface reactions occur generally in the mold. To restrain the interface reaction and improve conditions for continu-ous casting, a new mould flux based on aluminate system was devised. The viscous properties were investigated. Scanning electron microscopy and X-ray diffraction were applied to detect and characterize the crystalline phases in the continuous cooling process. The results showed that appropriate addition of CeO2 could avoid the precipitation of CaO and decrease the viscosity of the mould flux. Increasing the mass ratio of CaO/Al2O3, especially to a value exceeding 1, could worsen the stability of the mould flux. With a con-tent of less than 14 wt.%, Li2O could reduce the viscosity and breaking temperature, but its effect could be weakened for the pro-moted precipitation of LiAlO2. To obtain a mould flux with stable viscous properties, such as viscosity and breaking temperature, ap-propriate contents of CeO2 and Li2O should be controlled to around 10 wt.% and 14 wt.%, while the mass ratio of CaO/Al2O3 should not be more than 1.

  12. Study on characteristics of Ni-W-B composites containing CeO2 nano-particles prepared by pulse electrodeposition

    Institute of Scientific and Technical Information of China (English)

    WANG Junli; XU Ruidong; ZHANG Yuzhi

    2012-01-01

    Ni-W-B composites containing CeO2 nano-particles on the surface of 45 steel were prepared by pulse electrodeposition,and the influence of pulse frequency,pulse duty circle and heat treatment temperature on the structures and properties were investigated.The results indicated that the pulse co-deposition of Ni,W,B and CeO2 nano-particles led to Ni-W-B/CeO2 composites possessing higher microhardness and better wear resistance when heat-treated at 400 ℃ for 1 h.The microhardness of 636 HV and the deposition rate of 0.0281 mm/h of the as-deposited alloy were the highest at pulse frequency of 1000 Hz,pulse duty circle of 10% and pulse average current density of 10 A/dm2.The composites were mainly in the amorphous state and were partially crystallized as-deposited,and the crystallization trend was strengthened when heat-treated at 400 ℃.Decreasing pulse duty cycle from 75% to 10% was favorable to the refinement in grain strctures and improvement ofmicrostructures.The crystal sizes of the composites were smaller by means of pulse electrodeposition.

  13. CeO2-supported Au38(SR)24 nanocluster catalysts for CO oxidation: a comparison of ligand-on and -off catalysts

    Science.gov (United States)

    Nie, Xiaotao; Zeng, Chenjie; Ma, Xiangang; Qian, Huifeng; Ge, Qingjie; Xu, Hengyong; Jin, Rongchao

    2013-06-01

    The catalytic properties of atomically precise, thiolate-protected Au38(SR)24 (R = CH2CH2Ph) nanoclusters supported on CeO2 were investigated for CO oxidation in a fixed bed quartz reactor. Oxygen (O2) thermal pretreatment of Au38(SR)24/CeO2 at a temperature between 100 and 175 °C largely enhanced the catalytic activity, while pretreatment at higher temperatures (>200 °C) for removing thiolate instead gave rise to a somewhat lower activity than that for 175 °C pretreatment, and the ligand-off clusters were also found to be less stable. The CO conversion in the case of wet feed-gas (i.e. the presence of H2O vapor) was appreciably higher than the case of dry feed-gas when the reaction temperature was kept relatively low (between 60 and 80 °C), and interestingly the ligand-on and ligand-off catalysts exhibited opposite response to water vapor. Finally, we discussed some insights into the catalytic reaction involving the well-defined gold nanocluster catalyst.

  14. Effect of manganese and potassium addition on CeO2-Al2O3 catalyst for hydrogenation of benzoic acid to benzaldehyde

    Institute of Scientific and Technical Information of China (English)

    CHENG; Dangguo; HOU; Chunyang; CHEN; Fengqiu; ZHAN; Xiaol

    2009-01-01

    A series of Mn/CeO2-Al2O3 and K/CeO2-Al2O3 catalysts for hydrogenation of benzoic acid to benzaldehyde were prepared to in-vestigate the effect of Mn, K addition on CeO2-Al2O3 catalyst. X-ray diffraction (XRD) and H2-temperature-programmed reduction (H2-TPR) results suggested that the interaction between CeO2 and MnOx enhanced the reducibility of catalysts and therefore benzoic acid conversion.The addition of K increased the number of basic number on the catalyst which leads to a high selectivity to benzaldehyde, but excessive addition imposed negative effects on the catalyst performance. A Mn-K/CeO2Al2O3 catalyst was developed and investigated in the reaction. The simul-taneous addition of Mn and K enhanced not only the catalytic activity but also the capacity to resist the coke formation over catalyst.

  15. Active sites over CuO/CeO2 and inverse CeO2/CuO catalysts for preferential CO oxidation

    Science.gov (United States)

    Zeng, Shanghong; Wang, Yan; Ding, Suping; Sattler, Jesper J. H. B.; Borodina, Elena; Zhang, Lu; Weckhuysen, Bert M.; Su, Haiquan

    2014-06-01

    A series of CuO/CeO2 and inverse CeO2/CuO catalysts are prepared by the surfactant-templated method and characterized via XRD, HRTEM, H2-TPR, SEM, XPS, in situ XRD, in situ UV-Vis and N2 adsorption-desorption techniques. It is found that there are two kinds of surface sites in the CuO-CeO2 system, including CuO surface sites for CO chemisorption and CeO2 surface sites with oxygen vacancies for oxygen sorption. The active sites for CO oxidation are located on the contact interface of two-kind surface sites and the lattice oxygen can make a significant contribution to the CO-PROX reaction. The resistance to H2O and CO2 is related to BET surface area, the crystallite sizes of CuO and the reduction behavior of catalysts. The Ce4Cu4 and Ce4Cu1 catalysts exhibit the best resistance against H2O and CO2.

  16. Structural and flux-pinning properties of laser ablated YBa 2Cu 3O 7-δ thin films: Effects of self-assembled CeO 2 nanodots on LaAlO 3 substrates

    Science.gov (United States)

    Haywood, Talisha; Oh, Sang Ho; Kebede, Abebe; Pai, Devdas M.; Sankar, Jag; Christen, David K.; Pennycook, Stephen J.; Kumar, Dhananjay

    2008-12-01

    Self-assembled nanodots of CeO 2 on (1 0 0) LaAlO 3 substrates, generated in situ by means of a pulsed laser deposition method prior to the deposition of YBa 2Cu 3O 7-δ (YBCO) films, have been used to modify the superconducting properties of resulting YBCO films. Structural characterization has indicated that CeO 2 layers grow via van der Merwe three-dimensional mode and the islands eventually acquire a pancake type of structure with lateral dimension several times larger than vertical dimension. The three-dimensional growth of CeO 2 islands with (1 0 0) preferred orientation is believed to be associated with its surface energy anisotropy. The magnetization versus temperature and magnetization versus field measurements and analysis have suggested that CeO 2 can affect the superconducting properties of YBCO films favorably or adversely depending on the density of CeO 2 nanodots on the substrate surfaces prior to the deposition of YBCO films.

  17. Design and Preparation of MnO2/CeO2-MnO2 Double-Shelled Binary Oxide Hollow Spheres and Their Application in CO Oxidation.

    Science.gov (United States)

    Zhang, Jian; Cao, Yidan; Wang, Chang-An; Ran, Rui

    2016-04-06

    Herein, we designed an extremely facile method to prepare well-defined MnO2@CeO2-MnO2 ball-in-ball binary oxide hollow spheres by employing carbon spheres (CSs) as sacrificial templates. The synthesis process involves a novel self-assembled approach to prepare core-shell CSs@CeO2 precursor, which would directly react with KMnO4 aqueous solution to form yolk-shell CSs@MnO2/CeO2-MnO2 precursor in the following step. Well-dispersed Ce-Mn binary oxide with double-shelled hollow sphere structure could be achieved after annealing the precursor in air. The evolution process and formation mechanism of this novel structure were thoroughly studied in this paper. Especially the as-prepared double-shell MnO2/CeO2-MnO2 hollow spheres exhibited enhanced catalytic activity for CO oxidation compared with the pure MnO2 hollow spheres and pure CeO2 hollow spheres. We believe the high surface area, hierarchical porous structures, and strong synergistic interaction between CeO2 and MnO2 contribute to the excellent catalytic activity. Most importantly, this method could be extended to prepare other transition metal oxides. As an example, triple-shelled Co-Mn composite hollow spheres assembled by ultrathin nanoplates were successfully prepared.

  18. Effect of CeO2 and CaO Promoters on Ignition Performance for Partial Oxidation of Methane over Ni/MgO-Al2O3 Catalyst

    Institute of Scientific and Technical Information of China (English)

    Yejun Qiu; Jixiang Chen; Jiyan Zhang

    2007-01-01

    The effect of CeO2 and CaO promoters on the ignition performance over Ni/MgO-Al2O3 catalyst for the partial oxidation of methane (POM) to synthesis gas was investigated. It was found that the POM reaction could not be ignited over 1wt%Ni/MgO-Al2O3 catalyst without the promoters in the temperature range from 773 K to 1073 K. CeO2 and CaO promoters enhanced the ignition performance and the POM reactivity of 1wt%Ni/MgO-Al2O3 catalyst remarkably. Moreover, the improving effect became greater with the increase of the promoter content under the investigated reactionconditions. The modification effects of CeO2 and CaO promoters were closely related to the concentration and reducibility of the surface and bulk oxygen species.

  19. Preferential oxidation of CO in excess H2 over CuO/CeO2 catalysts: Performance as a function of the copper coverage and exposed face present in the CeO2 support

    DEFF Research Database (Denmark)

    Monte, M.; Gamarra, D.; López Cámara, A.

    2014-01-01

    CuO/CeO2 catalysts where the support has different nanoparticle shapes exposing different lattice planes are examined for the preferential oxidation of CO in the presence of excess H2 (CO-PROX reaction) in operando DRIFTS conditions. Even for catalysts with same surface concentration of Cu...... CuO nanocrystals is more difficult on nanocube shaped CeO2 than on other CeO2 morphologies. Also EPR spectra show that the CuO entities nucleate on the ceria nanocubes differently. The higher stabilization of the oxidized state indicated by DFT, together with the mentioned structural distortion, may...... and selectivity, so that they are fully reduced at higher temperature in agreement with TPR data. DFT calculations show that CuO nanoparticles interact more strongly (distorting more their structure) with the CeO2 (001) surface than with the (111) surface, while XRD indicates that the formation of well developed...

  20. Effect of CeO2 doping on catalytic activity of Fe2O3/gamma-Al2O(3) catalyst for catalytic wet peroxide oxidation of azo dyes.

    Science.gov (United States)

    Liu, Yan; Sun, Dezhi

    2007-05-08

    In order to find a catalyst with high activity and stability for catalytic wet peroxide oxidation (CWPO) process under normal condition, with Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) catalysts prepared by impregnation method, the effect of CeO(2) doping on the structure and catalytic activity of Fe(2)O(3)/gamma-Al(2)O(3) for catalytic wet peroxide oxidation of azo dyes at 25 degrees C and atmospheric pressure is evaluated using BET, SEM, XRF, XRD, XPS and chemical analysis techniques, and test results show that, better dispersion and smaller size of Fe(2)O(3) crystal can be achieved by adding CeO(2), and the content of chemisorbed oxygen can also be increased on the surface of catalyst. CWPO experimental results indicate that azo dyes in simulated wastewater can be efficiently mineralized and the catalytic activity of Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) can be increased by about 10% compared with that of Fe(2)O(3)/gamma-Al(2)O(3) because of the promotion of the structural and redox properties of the ferric oxide by ceria doped. Leaching tests indicate that Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) are stable with a negligible amount of irons found in the aqueous solution after reaction for 2h. It can therefore be concluded from results and discussion that in comparison with Fe(2)O(3)/gamma-Al(2)O(3), Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) is a suitable catalyst, which can effectively degrade contaminants at normal temperature and atmospheric pressure.

  1. 一种新的CeO2改性渗铬涂层的制备与氧化性能%Preparation and oxidation behavior of a novel CeO2-modified chromizing coating

    Institute of Scientific and Technical Information of China (English)

    孙俭峰; 周月波; 张海军

    2013-01-01

    利用CeO2颗粒部分替代Al2O3粉作填充剂对电镀纳米Ni和微晶Ni进行800℃低温渗铬,将CeO2颗粒渗入涂层的外层,制备了2种CeO2改性渗铬涂层.采用相同的工艺在微晶Ni上利用不含CeO2的普通渗剂直接渗铬,获得一种不含CeO2粒子的普通渗铬涂层.SEM/EDX和TEM结果表明:基体Ni的细化和CeO2颗粒的渗入有利于得到细晶渗铬涂层.在900℃下氧化时,CeO2颗粒的渗入明显提高了渗铬涂层的抗氧化性能.对于该2种CeO2改性的渗铬涂层,基体Ni的纳米化明显降低了涂层在暂态氧化期的氧化速度,使得在纳米Ni上制备的CeO2改性渗铬涂层具有更好的抗氧化性能.%By using CeO2 particles instead of part of Al2O3 particles as filler,the CeO2 was successfully entrapped into the outer layer of the chromizing coatings on the as-deposited nanocrystalline (NC) and microcrystalline (MC) Ni films using a conventional pack-cementation method at 800 ℃.For comparison,chromizing was also performed under the same condition on MC Ni film using Al2O3 as filler without CeO2 particles.SEM/EDX and TEM results indicate that the refinement of Ni grain and CeO2 entrapped into the chromizing coatings refine the grain of the chromizing coating.Oxidation at 900 ℃ indicates that compared with the CeO2-free chromizing coating,the CeO2-dispersed chromizing coating exhibits an increased oxidation resistance.For the CeO2-dispersed chromizing coating,the refinement of Ni grain size significantly decreases the transient-oxidation scaling rate of the chromizing coatings.Together with this,the CeO2-dispersed chromizing coating formed on NC Ni exhibits a better oxidation resistance.

  2. Grain-boundary phases in hot-pressed silicon nitride containing Y2O3 and CeO2 additives

    Science.gov (United States)

    Guha, J. P.; Hench, L. L.

    1983-01-01

    Auger electron spectroscopy in conjunction with X-ray powder diffraction and scanning electron microscopy is used to analyze the grain-boundary phases of Y2O3- and CeO2-doped Si3N4 hot-pressed materials in order to demonstrate that the additives concentrate predominantly in the grain boundaries of Si3N4 in the form of various oxynitride phases. A high oxygen content observed in sample fracture surfaces was found to be consistent with the existence of an oxygen-enriched phase in the grain boundaries. The presence of yttrium and cerium in the fracture surfaces and an overall increase in the O/N ratio imply that the additive oxides are predominantly concentrated in the intergranular phases.

  3. Influence of the Electronic Structure and Optical Properties of CeO2 and UO2 for Characterization with UV-Laser Assisted Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Billy Valderrama; H.B. Henderson; C. Yablinsky; J. Gan; T.R. Allen; M.V. Manuel

    2015-09-01

    Oxide materials are used in numerous applications such as thermal barrier coatings, nuclear fuels, and electrical conductors and sensors, all applications where nanometer-scale stoichiometric changes can affect functional properties. Atom probe tomography can be used to characterize the precise chemical distribution of individual species and spatially quantify the oxygen to metal ratio at the nanometer scale. However, atom probe analysis of oxides can be accompanied by measurement artifacts caused by laser-material interactions. In this investigation, two technologically relevant oxide materials with the same crystal structure and an anion to cation ratio of 2.00, pure cerium oxide (CeO2) and uranium oxide (UO2) are studied. It was determined that electronic structure, optical properties, heat transfer properties, and oxide stability strongly affect their evaporation behavior, thus altering their measured stoichiometry, with thermal conductance and thermodynamic stability being strong factors.

  4. Effect of Preparation Method on Surface Area and Crystalline Form of CeO2-ZrO2 Solid Solution

    Institute of Scientific and Technical Information of China (English)

    王晓红; 郭耘; 卢冠忠; 郭杨龙; 王筠松; 张志刚; 刘晓晖

    2004-01-01

    The CeO2-ZrO2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m2·g-1, and that calcined at 900 ℃ for 6 h is 88 m2·g-1.The sample with tetragonal symmetry Ce0.5Zr0.5O2 phase has a higher stability.

  5. Hydrogen transfer reaction of cyclohexanone with 2-propanol catalysed by CeO2-ZnO materials: Promoting effect of ceria

    Indian Academy of Sciences (India)

    Braja Gopal Mishra; G Ranga Rao; B Poongodi

    2003-10-01

    Ce-Zn-O mixed oxides were prepared by amorphous citrate process and decomposition of the corresponding acetate precursors. The resulting materials were characterised by TGA, XRD, UV-Vis-DRS, EPR, SEM and surface area measurements. XRD and DRS results indicated fine dispersion of the ceria component in the ZnO matrix. EPR results clearly indicate the presence of oxygen vacancy and defect centres in the composite oxide. Addition of CeO2 to ZnO produced mixed oxides of high surface area compared to the pure ZnO. Hydrogen transfer reaction was carried out on these catalytic materials to investigate the effect of rare earth oxide on the activity of ZnO. Addition of ceria into zinc oxide was found to increase the catalytic activity for hydrogen transfer reaction. The catalytic activity also depended on the method of preparation. Citrate process results in uniformly dispersed mixed oxide with higher catalytic activity.

  6. Role of Surface Adsorption in Fast Oxygen Storage/Release of CeO2-ZrO2 Mixed Oxides

    Institute of Scientific and Technical Information of China (English)

    Wu Xiaodong; Liang Qing; Wu Xiaodi; Weng Duan

    2007-01-01

    Four kinds of CeO2-ZrO2 mixed oxides, i.e., a physical mixture of ceria and zirconia (CZP), zirconia-coated ceria (ZCC), ceria-coated zirconia (CCZ) and a chemical mixture of ceria and zirconia (CZC), were prepared. The oxygen storage capacity (OSC) measurements at 500 ℃ were performed under transient and stationary reaction conditions. All the curves of CO2 evolution during CO-O2 cycles presented a bimodal shape. The first peak was primarily the result of the reaction of CO with the oxygen from the oxides, which was mainly determined by the nature of the material. The second peak was mostly related to the CO2 adsorption behavior and was highly influenced by the surface area and the number of surface active sites. As a result, OSC activity of the samples followed in the order of CZC>CCZ>ZCC≈CZP.

  7. Laser-induced evaporation, reactivity and deposition of ZrO 2, CeO 2, V 2O 5 and mixed Ce-V oxides

    Science.gov (United States)

    Flamini, C.; Ciccioli, A.; Traverso, P.; Gnecco, F.; Giardini Guidoni, A.; Mele, A.

    2000-12-01

    It has been found that pulsed laser ablation has good potentiality for the deposition of ZrO2, CeO2, V2O5 and mixed Ce-V oxides which are very important materials for their application in optics and electrochromic devices. Laser induced compositional changes of thin films in the ablation and deposition processes of these materials have been explored. The effect of the oxygen gas pressure on the thin film composition has been examined. The congruency of the process has been treated on the basis of a thermal mechanism of evaporation-decomposition of the compounds. An attempt to model the processes by means of a thermodynamic approach is reported.

  8. Visible Light Photocatalytic Activity of CeO2-ZnO-TiO2 Composites for the Degradation of Rhodamine B

    Directory of Open Access Journals (Sweden)

    S. Prabhu

    2014-01-01

    Full Text Available TiO2 plays a significant role in many applications including solar cell. Consecutively to absorb the low-energy radiation, it is very much essential to tune the optical property of TiO2. We fabricated CeO2-ZnO-TiO2 semiconductor composites by sol-gel method and achieved the absorption of lower energy radiation. The prepared composites were characterized by TG-DTA, UV-DRS, XRD, AFM, TEM and FESEM techniques. The particle and crystalline size of the composites was calculated using FESEM and XRD techniques, respectively. The photocatalytic activity of the synthesized composite for the degradation of Rhodamine B (RhB under visible light irradiation was investigated. The photocatalytic degradation of RhB under various experimental conditions such as amount of catalyst, initial dye concentration and H2O2 amount was also demonstrated and the rate constant was calculated using L-H model.

  9. Characterization and Catalytic Activity for the Oxidation of Ethane and Propane on Platinum and Copper Supported on CeO2/Al2O3

    Directory of Open Access Journals (Sweden)

    Cataluña R.

    1998-01-01

    Full Text Available Ethane and propane oxidation on platinum and copper supported on Al2O3 and CeO2/Al2O3 catalysts were studied comparatively by examining reaction rates as a function of temperature. Results show that the addition of cerium oxide shifts the catalytic activity to higher temperatures. This negative influence is less pronounced in the case of supported copper samples, which on the basis of EPR and FTIR of adsorbed CO results is attributed to the low relative amount of this metal is in contact with ceria. The decrease in activity the presence of ceria might be due to changes in metal particle size or to the stabilization of the oxidized states of the metals, induced by their interactions with cerium oxide. The higher activity of platinum, in comparison with copper, is attributed to its higher reducibility along with an easier hydrocarbon activation on that metal.

  10. First principles study of the magnetism driven by cation defects in CeO2: the important role of O2p states

    Institute of Scientific and Technical Information of China (English)

    Lu Zhan-Sheng; Ma Dong-Wei; Zhang Jing; Xu Guo-Liang; Yang Zong-Xian

    2012-01-01

    The magnetism driven by cation defects in undoped CeO2 bulk and thin films is studied by the density functional theory corrected for on-site Coulomb interactions (DFT+U) with U =5 eV for the Ce4f states and U =7 eV for the O2p states.It is found that the Ce vacancies can induce a magnetic moment of the ~ 4 μB/supercell,which arises mainly from the 2p hole state of the nearest neighbouring O atom (~ 1 μB on per oxygen) to the Ce vacancy.The effect of the methodology is investigated,indicating that U =7 eV for the O2p state is necessary to obtain the localized O2p hole state in defective ceria with cation vacancies.

  11. The influence of Mn-doped CeO2 on the activity of CuO/CeO2 in CO oxidation and NO + CO model reaction

    Science.gov (United States)

    Deng, Changshun; Huang, Qingqing; Zhu, Xiying; Hu, Qun; Su, Wenli; Qian, Junning; Dong, Lihui; Li, Bin; Fan, Minguang; Liang, Caiyuan

    2016-12-01

    This work is mainly focused on the investigation of the influence of Mn-doped CeO2 supported by CuO on the physicochemical and catalytic properties for CO oxidation and NO + CO model reaction. The obtained samples were characterized using N2-physisorption (BET), XRD, LRS, TEM, EDS-Mapping, ICP-AES, XPS, H2-TPR, O2-TPD, in situ DRIFTS, CO oxidation, and NO + CO model reaction. The results imply that appropriate doping MnOx into the lattice of CeO2 will cause an obvious change in the properties of the catalyst and the Cu/CeMn-10: 1 catalyst shows the largest specific surface area, the most uniformity of structure, and the most extent of lattice expansion. A few addition of MnOx is more conducive to the generation of low valence manganese ion in the process of calcination, which may contribute to the synergetic introduction. This further results in more Cu+ due to the shifting of redox equilibrium (Cu2+ + Ce3+ ↔ Cu+ + Ce4+) to right, as well as more oxygen vacancies. Moreover, the capability of Cu/CeMn-10: 1 on desorb/transform/decompose of the adsorbed NO species is more effective than that of Cu/CeO2. The results of catalytic performance show that Cu+/Cu0 species play a key role, and the activity is mainly related to the specific surface area, the content of Cu+ and Ce3+, the reduction, desorption capability of chemisorbed O2- (and/or O-) species as well as adsorption behaviors of these catalysts for CO oxidation and NO + CO reaction. Finally, possible reaction mechanisms are tentatively proposed to understand the reactions.

  12. FTIR study of CO adsorption on Rh/MgO modified with Co, Ni, Fe, or CeO2 for the catalytic partial oxidation of methane.

    Science.gov (United States)

    Li, Dalin; Sakai, Shigemasa; Nakagawa, Yoshinao; Tomishige, Keiichi

    2012-07-07

    The surface state of Rh/MgO catalysts modified with Co, Ni, Fe, or CeO(2) after the reduction and partial oxidation pretreatments as well as during the catalytic partial oxidation of methane has been investigated by FTIR of adsorbed CO. The results of CO adsorption on the reduced catalysts suggest the formation of Rh-M alloy on Rh-M/MgO (M = Co, Ni, Fe) and Rh particles partially covered with reduced ceria on Rh-CeO(2)/MgO. The strength of CO adsorption on Rh/MgO is weakened by the modification with Co, Ni, Fe, or CeO(2). Partial oxidation pretreatment of Rh/MgO leads to a significant decrease in the CO adsorption due to the oxidation of Rh. In contrast, on partially oxidized Rh-M/MgO (M = Co, Ni, Fe) and Rh-CeO(2)/MgO, the preferential oxidation of the surface M atoms or reduced ceria maintains the metallic Rh and preserves the CO adsorbed on the surface Rh atoms. The CO adsorption during the reaction of catalytic partial oxidation of methane on Rh/MgO and Rh-Ni/MgO is similar to that on the reduced catalysts. On the other hand, the CO adsorption during the reaction on Rh-Co/MgO, Rh-Fe/MgO, and Rh-CeO(2)/MgO is different from that on the reduced catalysts, and this is related to the structural change of these catalysts during the reaction.

  13. Fabrication of Mesoporous Co_3O_4-CeO_2 and their Application in Selective Oxidation of CO%介孔Co_3O_4-CeO_2复合氧化物的制备及在CO选择性氧化中的应用

    Institute of Scientific and Technical Information of China (English)

    刘华; 许珊; 王晓来

    2011-01-01

    Mesoporous Co3O4-CeO2 mixed oxides was synthesized by a bi-solvent method in which SBA-15 was introduced as the hard template and cerium nitrate and cobalt nitrate were wed as precursors.The active composite and support were characterized by techniques of X-ray powder diffraction,nitrogen adsorption/desorption,temperature programmed reduction and transmission electron microscopy.The experimental results show that the catalyst prepared by the bi-solvent method displayed the uniform mesoporous structure,the smaller particle size,the higher surface area and the high dispersion of active composites compared with the catalysts prepared by impregnation and co-precipitation methods.In addition,the as-prepared mesoporous Co3O4-CeO2 showed a superior performance of CO oxidation over catalysts prepared by traditional preparation protocols of impregnation method and coprecipitation method,which can be ascribed to the high surface area and high dispersion of the catalyst.%以硝酸钴和硝酸铈为前驱物,SBA-15为硬模板,利用双溶剂法制备了Co3O4-CeO2介孔复合氧化物,通过X-射线衍射、N2吸脱附测试、程序升温还原和透射电子显微镜等技术对活性组分及载体进行了表征,并且与浸渍法和共沉淀法所制备的催化剂进行了对比分析.结果表明,相比于浸渍法和共沉淀法,采用双溶剂法制备的介孔Co3O4-CeO2复合氧化物具有均匀的介孔结构、较小的颗粒尺寸、较大的比表面积和较高的活性组分分散度.此外,CO氧化脱除评价显示与常规的共沉淀法和浸渍法所制备的催化剂相比该介孔复合氧化物具有较高的反应活性和选择性,其高活性主要归因于较高的比表面积和活性组分的高分散度.

  14. Effects of Sintering Temperature on Ti/RuO2-CeO2 Electrodes Applied in Super-Capacitors%烧结温度对Ti/RuO2-CeO2超电容性能的影响

    Institute of Scientific and Technical Information of China (English)

    孙俊梅; 王欣; 魏宗平; 邵艳群; 张腾; 唐电

    2011-01-01

    RuO2-CeO2/Ti electrodes were prepared by thermal decomposition, taking RuCl3 and CeCl3 as raw material, ethanol as solvent and Ti slide as substrate.The microstructures were investigated by means of XRD,SEM and HRTEM. The supercapacitive properties were examined by cyclic voltammetric and chrono-potentiometry measurements. The results showed that the highest specific capacitance was obtained in the electrodes prepared at 300 t, and the electrodes at higher or lower sintering temperature had lower specific capacitances. It is indicated that the capacitive properties of the Ti/RuO2-CeO2 electrodes were influenced by their microstructures. The unstable or well developed structure of the oxides was not good for the supercapacitor performance of the. Electrodes. In the electrodes prepared at 300℃, the amorphous structure with nanocrystals could be found. This kind of microstructure had more electroactive points and lager electrochemical roughness.%以三氯化钌和三氯化铈为原料,以无水乙醇为溶剂,采用热分解法在钛基材上制备了Ti/RuO2-CeO2二元氧化物涂层电极材料,利用XRD,SEM,HR-TEM分析方法对涂层组织结构进行表征,通过循环伏安和充放电曲线来研究涂层的超电容性质.结果表明,300℃烧结制备的电极可获得最大的比电容;烧结温度低于或者超过300℃,电极的超电容性能不佳.分析表明,Ti/RuO2-CeO2的超电容性能与其结构密切相关,氧化物的结构未稳定或发育良好,均不利于提高超电容性能.300℃时涂层形成带有纳米级微晶的非晶组织,获得了高的活性点数和电化学粗糙度.

  15. CeO2对Al2O3基泡沫陶瓷过滤器性能的影响%Effect of CeO2 on Properties of Al2O3-based Ceramic Foam Filters

    Institute of Scientific and Technical Information of China (English)

    马战红; 任凤章

    2012-01-01

    The effects of CeO2 on the properties of ceramic foam by using polymeric sponge impregnation process are studied.The influences of CeO2 different contents on properties of ceramic foam filter,such as cold compression strength(CCS),thermal shock resistance,volume weight,are investigated.The microstructure of samples is analyzed using scanning electron microscopy(SEM).The results show that the CeO2 used as sintering additives can promote the formation of a liquid phase,reduce the sintering temperature of alumina-based ceramic foam,and improve microstructure and properties of the ceramic.The samples with the best thermal shock resistance and high compression strength are obtained by adding 3% CeO2 respectively.%采用有机泡沫浸渍工艺,研究了CeO2对氧化铝基泡沫陶瓷过滤器性能的影响。通过检测试样的常温耐压强度、热震稳定性、通透率等性能以及利用扫描电镜(SEM)对试样的显微结构进行研究,较为详细地探讨不同含量的CeO2对氧化铝基泡沫陶瓷过滤器性能的影响。结果表明,使用CeO2作添加剂可促进液相的生成,降低氧化铝基泡沫陶瓷的烧成温度,改善瓷体的微观组织结构和性能。实验结果表明,当CeO2含量为3%时其热震稳定性和抗压强度最佳。

  16. A New Strategy for Humidity Independent Oxide Chemiresistors: Dynamic Self-Refreshing of In2 O3 Sensing Surface Assisted by Layer-by-Layer Coated CeO2 Nanoclusters.

    Science.gov (United States)

    Yoon, Ji-Wook; Kim, Jun-Sik; Kim, Tae-Hyung; Hong, Young Jun; Kang, Yun Chan; Lee, Jong-Heun

    2016-08-01

    The humidity dependence of the gas sensing characteristics of metal oxide semiconductors has been one of the greatest obstacles for gas sensor applications during the last five decades because ambient humidity dynamically changes with the environmental conditions. Herein, a new and novel strategy is reported to eliminate the humidity dependence of the gas sensing characteristics of oxide chemiresistors via dynamic self-refreshing of the sensing surface affected by water vapor chemisorption. The sensor resistance and gas response of pure In2 O3 hollow spheres significantly change and deteriorate in humid atmospheres. In contrast, the humidity dependence becomes negligible when an optimal concentration of CeO2 nanoclusters is uniformly loaded onto In2 O3 hollow spheres via layer-by-layer (LBL) assembly. Moreover, In2 O3 sensors LBL-coated with CeO2 nanoclusters show fast response/recovery, low detection limit (500 ppb), and high selectivity to acetone even in highly humid conditions (relative humidity 80%). The mechanism underlying the dynamic refreshing of the In2 O3 sensing surfaces regardless of humidity variation is investigated in relation to the role of CeO2 and the chemical interaction among CeO2 , In2 O3 , and water vapor. This strategy can be widely used to design high performance gas sensors including disease diagnosis via breath analysis and pollutant monitoring.

  17. Liquid-Phase Ethanol Oxidation and Gas-Phase CO Oxidation Reactions over M Doped (M = Ag, Au, Pd, and Ni and MM′ Codoped CeO2 Nanoparticles

    Directory of Open Access Journals (Sweden)

    Yohan Park

    2016-01-01

    Full Text Available Transition metal doped metal oxides have been studied extensively for potential applications to environments and chemical industry. Herein, M doped (M = Ag, Au, Pd, and Ni and MM′ codoped CeO2 nanoparticles (NPs were prepared by a hydrothermal method and their liquid-phase ethanol and gas-phase CO oxidation performances were examined by UV-visible absorption spectroscopy and temperature programmed mass spectrometry, respectively. The ethanol and CO oxidation performances were enhanced greatly by metal-doping and were dependent on the relative concentration of codoped metals. For ethanol oxidation, the concentration of acetaldehyde became saturated at low levels, while that of ethyl acetate continuously increased to become a final major product. For M doped CeO2 NPs, the ethanol oxidation performance showed an order of Ni < Ag < Pd ≪ Au. For MM′ codoped CeO2 NPs, the activity of Au doped CeO2 deteriorated drastically upon adding other metals (Ag, Ni, and Pd as a cocatalyst.

  18. Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO-SiO2 coating on titanium alloy.

    Science.gov (United States)

    Li, H C; Wang, D G; Chen, C Z; Weng, F

    2015-03-01

    To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular-dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris-HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample.

  19. Investigation of the Poisoning Mechanism of Lead on the CeO2-WO3 Catalyst for the NH3-SCR Reaction via in Situ IR and Raman Spectroscopy Measurement.

    Science.gov (United States)

    Peng, Yue; Si, Wenzhe; Li, Xiang; Chen, Jianjun; Li, Junhua; Crittenden, John; Hao, Jiming

    2016-09-01

    The in situ IR and Raman spectroscopy measurements were conducted to investigate lead poisoning on the CeO2-WO3 catalysts. The deactivation mechanisms were studied with respect to the changes of surface acidity, redox property, nitrate/nitrite adsorption behaviors, and key active sites (note that the results of structure-activity relationship of CeO2-WO3 were based on our previous research). (1) Lewis acid sites originated from CeO2 and crystalline WO3, whereas Brønsted acid sites originated from Ce2(WO4)3. The poisoned catalysts exhibited a lower surface acidity than the fresh catalysts: the number of acid sites decreased, and their thermal stability weakened. (2) The reducibility of catalysts and the amount of active oxygen exhibited a smaller influence after poisoning because lead preferred to bond with surface WOx species rather than CeO2. (3) The quantity of active nitrate species decreased due to the lead coverage on the catalyst and the partial bridged-nitrate species induced by lead exhibited a low degree of activity at 200 °C. (4) Crystalline WO3 and Ce2(WO4)3 originated from the transformation of polytungstate sites. These sites were the key active sites during the SCR process. The formation temperatures of polytungstate on the poisoned catalysts were higher than those on the fresh catalysts.

  20. KOH溶液中CeO2-Pd/C对乙醇的电催化研究%Study on CeO2-Pd/C to ethanol electrocatalytic reaction in KOH solution

    Institute of Scientific and Technical Information of China (English)

    刘畅; 田丹妮; 周新文; 代忠旭

    2015-01-01

    用液相还原法制得CeO2-Pd/C催化剂样品,研究Ce元素对Pd/C催化氧化乙醇能力的影响.通过XRD,循环伏安和计时电流法对实验样品进行了结构表征和催化氧化乙醇行为测试.结果表明,在碱性条件下,CeO2有助于提升Pd/C对乙醇的催化氧化能力.当n(Pd):n(CeO2)=2:1(摩尔比)时,催化效率达到峰值.但当Pd和CeO2的摩尔比达到1:2后,继续增加CeO2的量,其氧化电量基本保持平稳.样品中,Pd和CeO2的摩尔比达到1:2之前,CeO2可以作为Pd的助催化剂;当Pd和CeO2的摩尔比达到1:2之后,CeO2不再作为助催化剂,而可能是成为了催化剂的载体.%To study the influence of catalytic oxidation ability to ethanol of Ce element in Pd/C catalyst , CeO2-Pd/C catalysts were prepared by a liquid phase chemical reduction method. The structure and catalytic oxidation of ethanol behavior of the catalysts were characterized and tested by XRD,cyclic voltammograms and chronoamperometry experiment,respectively. The results show that CeO2 can improve Pd/C catalytic oxidation ability of ethanol in alkaline solution. When n(Pd):n(CeO2) equaled 2:1 (molar ratio),its catalytic efficiency value reached a peak. When the molar ratio of Pd and CeO2 changed less than 1:2,its oxidation capacity remained unchanged basically by increasing the amount of CeO2. It was indicated that CeO2 was a co-catalyst before the molar ratio of Pd to CeO2 was larger than 1:2. After the numerical value was less than 1:2,CeO2 was no longer act as a co-catalyst,but might play a role of the catalyst carrier.

  1. Methane reforming With CO2 to syngas over CeO2-promoted Ni/Al2O3-ZrO2 catalysts Prepared Via a direct sol-gel process

    Institute of Scientific and Technical Information of China (English)

    Hansheng Li; Hang Xu; Jinfu Wang

    2011-01-01

    CeO2-promoted Ni/Al2O3-ZrO2 (Ni/Al2O3-ZrO2-CeO2) catalysts were prepared by a direct sol-gel process with citric acid as gelling agent.The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy (IR), thermal gravimetric analysis (TGA), microscopic analysis, X-ray diffraction (XRD) and temperature-programmed reduction (TPR).The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure.TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support.There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable.The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts.The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst.The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.

  2. Análise por difração de raios x de filmes de óxidos cerâmicos compostos por IrO2/TiO2/CeO2

    Directory of Open Access Journals (Sweden)

    Alves Valéria Almeida

    2000-01-01

    Full Text Available Independent of the sample form (powder or film, XRD analysis of Ir0,3Ti(0,7-xCe xO2, (nominal mixtures, for x=0, shows the formation of a solid solution phase between IrO2 and TiO2, as well as the rutile phases of IrO2 and TiO2. The presence of the anatase phase of TiO2 is also confirmed. The introduction of 30 mol% CeO2 in the mixture reveals the presence of the CeO2 and Ce2O3 phases, besides the already mentioned ones, in the powder. In the film form, however, an amorphous phase is identified. When all of the TiO2 is substituded by CeO2, for both sample forms, the only phases found are IrO2, CeO2 and Ce2O3. This result suggests cerium oxides are not capable of forming solid solutions with either IrO2 or (Ir,TiO2 acting solely as a dispersant matrix for these phases. These results are consistent with the much higher electrochemically active surface area when CeO2 is introduced in the binary Ti/Ir0,3Ti0,7O2 mixture. It was possible to establish a relationship between the electrochemical stability of the supported films and their crystalline structure. The unexpected presence of TiO2 and Ti2O3 in the Ti/Ir0,3Ce0,7O2 (film sample is attributed to oxidation of the Ti support during the calcination step.

  3. Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnO(x)-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NO(x).

    Science.gov (United States)

    Shin, Byeongkil; Chun, Ho Hwan; Cha, Jin-Sun; Shin, Min-Chul; Lee, Heesoo

    2016-05-01

    The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnO(x)-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NO(x) emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnO(x)-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h(-)1, and its de-NO(x) efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersion state and catalytic acidity on the catalyst surface, and the highly dispersed Mn and Ce on the nano-scaled TiO2 catalyst affects the increase of Lewis and Brønsted acid sites. A CeO2-rich additive on MnO(x)-TiO2 could provide stronger catalytic acid sites, associated with NH3 adsorption and the SCR performance. As the results of sulfur resistance in flue gas that contains SO2, the de-NO(x) efficiency of MnO(x)-TiO2 decreased by 15% over 200 degrees C, whereas that of 30 wt% ceria-doped catalyst increased by 14-21% over 150 degrees C. The high SO2 resistance of CeO2-MnO(x)-TiO2 catalysts that resulted from the addition of ceria suppressed the formation of Mn sulfate species, which led to deactivation on the surface of nano-catalyst.

  4. Synthesis of the Nanotublar Cubic Fluorite CeO2%纳米管状结构立方萤石型CeO2的合成

    Institute of Scientific and Technical Information of China (English)

    杨儒; 郭亮

    2004-01-01

    低温水热条件下,Ce4+离子经尿素水解均匀沉淀,在十八胺分子模板导向下形成了多层有序排列的纳米管状结构的立方萤石型CeO2,采用粉末X射线衍射(PXRD)、透射电镜(TEM)、高分辨透射电镜(HRTEM)以及选区电子衍射(SEAD)等手段对产物进行了表征.结果表明,该结构是由单根外、内径分别为10~20 nm、5~6 am左右的纳米管有序排列形成的纳米管束构成,且产物具有结晶性良好的立方萤石型CeO2晶体结构.在管束的生长过程中,反应体系首先形成单根纳米管,继而管与管之间又相互缔合生长成多层有序排列的纳米管束.控制尿素的水解,获得了不同pH值下的反应产物,发现反应体系pH值在5~6之间时产物为立方萤石型CeO2、6~8时为立方萤石型CeO2与六方型Ce(OH)CO3的混合物、大于8则为六方型Ce(OH)CO3.%Under hydrothermal condition,nitrate cerium(IV) was used as a cerium source,octadecylamine (C18H37NH2)as the molecular template and urea as a precipitating agent, and the hierarchically well-aligned nanotublar bunches of the cubic fluorite ceria were successfully synthesized.The materials have been characterized by Powder X-ray diffraction (PXRD),transmission electron microscopy (TEM),high-resolution transmission electron microscopy (HRTEM)and the selected area electron diffraction (SAED).The products exhibited the hierarchically well-aligned nanotublar bunch which was composed of single nanotube with outer and inner diameter 10~20 and 5~6 nm. The growth process of nanotublar hunches was monitored.Firstly, the separated nanotube appeared in the reaction system. Subsequently, the separated nanotubes integrated into the hierarchically well-aligned nanotublar bunch each other. In addition, the products have different crystalline phase and composition ad increasing the final pH value of reaction system; And when the final pH values of reaction system were at 5~6,6~8 and >8 respectively, the

  5. Common data buffer

    Science.gov (United States)

    Byrne, F.

    1981-01-01

    Time-shared interface speeds data processing in distributed computer network. Two-level high-speed scanning approach routes information to buffer, portion of which is reserved for series of "first-in, first-out" memory stacks. Buffer address structure and memory are protected from noise or failed components by error correcting code. System is applicable to any computer or processing language.

  6. A simple MOD method to grow a single buffer layer of Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9} (CGO) for coated conductors

    Energy Technology Data Exchange (ETDEWEB)

    Liu Min, E-mail: Lm@bjut.edu.c [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Key Laboratory of Advanced Functional Materials, Ministry of Education, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China); Shi Dongqi, E-mail: dongqi@uow.edu.a [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Suo Hongli; Ye Shuai; Zhao Yue; Zhu Yonghua [Key Laboratory of Advanced Functional Materials, Ministry of Education, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China); Li Qi; Wang Lin; Jihyun Ahn [Institute for Superconducting and Electronic Materials, University of Wollongong, NSW 2522 (Australia); Zhou Meiling [Key Laboratory of Advanced Functional Materials, Ministry of Education, College of Materials Science and Engineering, Beijing University of Technology, Beijing 100022 (China)

    2009-03-15

    A single Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9} (CGO) buffer layer was successfully grown on the home-made textured Ni-5 at.%W (Ni-5W) substrates for YBCO coated conductors by a simple metal-organic deposition (MOD) technique. The precursor solution was prepared using a newly developed process and only contained common metal-organic salts of both Ce and Gd dissolved into a propionic acid solvent. The precursor solution at 0.4 M concentration was spin coated on short samples of Ni-5W substrates and heat-treated at 1100 deg. C in a mixture gas of 5% H{sub 2} in Ar for an hour. X-ray studies indicated that the CGO films had good out-of-plane and in-plane textures with full-width-half-maximum values of 4.18 deg. and 6.19 deg., respectively. Atomic force microscope (AFM) investigations of the CGO films revealed that most of the grain boundary grooves on the Ni-5W surface were found to be well covered by CGO layers, which had a fairly dense and smooth microstructure without cracks and porosity. These results indicate that our MOD technique is very promising for further development of single buffer layer architecture for YBCO coated conductors, due to its low cost and simple process.

  7. 纳米CeO2悬浮液的流变性能研究%Study on Rheological Behavior of Nanosized CeO2 Suspension

    Institute of Scientific and Technical Information of China (English)

    郑国琴; 沈志刚; 曾晓飞; 陈建峰

    2012-01-01

    The theological behavior of polishing slurry plays an important role in the chemical mechanical polishing. In this research, the rheology property of nano-ceria slurry is investigated. The effects of pH, particle concentration, temperature and electrolyte concentration are discussed. It is shown that a lower zeta potential gives rise to a higher apparent viscosity and results in the observed shear thinning property. In the suspension if the particle concentration is below 17.4wt% ,the nano-ceria slurry exhibits Newtonian behavior and further addition of CeO2, higher apparent viscosity and shear-thinning behavior is observed. The influence of temperature on rheology property of CeO2 slurry appears more complex. When the temperature is lower than 35℃ , the apparent viscosity of the CeO2 slurry decreases with temperature increases. But when the temperature is higher than 35 ℃, increasing temperature results in the apparent viscosity increasing. If the electrolyte is added into the slurry,a shift of apparent viscosity to a higher value is observed due to the decreased zeta potential.%在化学机械抛光过程中,抛光液的流变性能起到至关重要的作用.本文利用Haake流变仪研究了水基纳米CeO2悬浮液在不同pH值、CeO2颗粒浓度、温度、中性电解质浓度下的流变性能.研究结果表明,随着zeta电位减小,悬浮液表观粘度增大,体系逐渐转变为剪切变稀的非牛顿流体.悬浮液中CeO2颗粒浓度低于17.4wt%时,颗粒浓度对体系的流变性能影响较弱,体系为牛顿流体,但是继续增大颗粒浓度,悬浮体表观粘度明显增大,出现剪稀现象.温度对悬浮液流变性能影响较为复杂,当温度小于35℃时,随着温度的升高体系表观粘度变小,温度大于35℃时,温度的升高反而使体系表观粘度增高.中性电解质的加入使得悬浮体的zeta电位降低,从而使体系表现出较高的表观粘度.

  8. CeO2/NaF吸附剂的制备及其对MoF6的吸附性能研究%Preparation of adsorbent CeO2/NaF and its adsorption performance for MoF6

    Institute of Scientific and Technical Information of China (English)

    李洒洒; 程治强; 李杨娟; 龙德武; 龚昱; 窦强; 吴明红; 李晴暖

    2015-01-01

    Background: The fluoride volatility process has been developed to recover uranium from spent nuclear fuel. And the fluoride adsorption technique is usually applied in the purification and collection of UF6 during the fluoride volatility process.Purpose: This study aims to investigate the characteristics and sorption performance of a novel sorbent CeO2/NaF synthesized by doping NaF with CeF3.Methods: With polymer sodium carboxymethyl cellulose (CMC) as a binder and pore-forming agent, CeF3 and NaFwas mixed according to a mass ratio of 4:9:62, and then water were added (the ratio of CMC to water is 1:6). The porous CeO2/NaF adsorbent particles were prepared by a mixing, molding and sintering process. The characteristics and adsorption performance of the adsorbent particles were analyzed and characterized.Results: Specific surface area of CeO2/NaF was (0.84±0.04)m2·g−1, which was twice of NaF sorbent made under the same process. Porosity was 42.2%, which was larger than that of NaF sorbent. The initial adsorption rate of MoF6 on CeO2/NaF was much higher than that of NaF sorbent. The temperature zone for desorption of MoF6 from CeO2/NaF ranged from 150°C to 300°C, while there were two desorption zones for desorption of MoF6 from NaF sorbent, which varied from 100°C to 300°C and 350°C to 400°C, respectively. This phenomenon showed that CeO2 might stabilize Mo6+in MoF6. Conclusion: The physical properties of NaF could be changed by doping with CeO2, and its adsorption performance was also improved.%将作为粘结剂和造孔剂的高分子羧甲基纤维素钠(Carboxymethylcellulose, CMC)、CeF3和NaF按4:9:62的质量比例混合,再加一定量的水(CMC与水的比为1:6),通过混捏、成形和烧结等程序制得了一种新型的CeO2/NaF吸附剂颗粒。通过研究CeO2的掺杂对NaF吸附剂表观性质和吸附性能的影响发现:CeO2/NaF吸附剂的比表面积为(0.84±0.04) m2·g−1,是相同条件下制得的 NaF 吸附剂的两倍以上;孔隙率为42.2%,也优于NaF吸附剂;CeO2/NaF和NaF吸附剂对MoF6的饱和吸附容量相当,但CeO2/NaF吸附剂的初始吸附速率明显大于NaF吸附剂;吸附于CeO2/NaF吸附剂上的MoF6在150–300°C单个温度段解吸附,而吸附于NaF吸附剂上的MoF6在100–300°C和350–400°C两个温度段发生解吸,表明CeO2的引入在一定程度上起到了稳定MoF6的作用。在NaF吸附剂内掺杂CeO2可以改变NaF吸附剂部分表观性质,从而改善NaF的吸附性能。

  9. A parallel buffer tree

    DEFF Research Database (Denmark)

    Sitchinava, Nodar; Zeh, Norbert

    2012-01-01

    We present the parallel buffer tree, a parallel external memory (PEM) data structure for batched search problems. This data structure is a non-trivial extension of Arge's sequential buffer tree to a private-cache multiprocessor environment and reduces the number of I/O operations by the number...... of available processor cores compared to its sequential counterpart, thereby taking full advantage of multicore parallelism. The parallel buffer tree is a search tree data structure that supports the batched parallel processing of a sequence of N insertions, deletions, membership queries, and range queries...

  10. ОКИСЛЕНИЕ СО НА КАТАЛИЗАТОРАХ CUO/CEO 2/G-AL 2O 3 И СО 3О 4/CEO 2/G-AL 2O 3

    OpenAIRE

    Загайнов, И.; Либерман, Е.; Михайличенко, А.; Конькова, Т.; Почиталкина, И.

    2008-01-01

    Синтезированы образцы CuO/CeO 2/g-Al 2O 3 и Со 3О 4/CeO 2/g-Al 2O 3 путем импрегнирования растворов нитратов соответствующих солей. Исследована каталитическая активность нанесенных катализаторов в реакции окисления СО. Показано, что каталитическая активность синтезированных образцов определяется химическим составом и способом нанесения вторичного носителя CeO 2 на поверхность g-Al 2O 3.CuO/CeO 2/g-Al 2O 3 and Со 3О 4/CeO 2/g-Al 2O 3 were synthesited by their nitrate salts impregnation.Catalyt...

  11. The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

    Science.gov (United States)

    Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

    2015-05-28

    Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and hence, also affecting the location of the Ce(III) cations and the structure of the TM13 clusters.

  12. Total catalytic wet oxidation of phenol and its chlorinated derivates with MnO2/CeO2 catalyst in a slurry

    Directory of Open Access Journals (Sweden)

    A. J. Luna

    2009-09-01

    Full Text Available In the present work, a synthetic effluent of phenol was treated by means of a total oxidation process-Catalyzed Wet Oxidation (CWO. A mixed oxide of Mn-Ce (7:3, the catalyst, was synthesized by co-precipitation from an aqueous solution of MnCl2 and CeCl3 in a basic medium. The mixed oxide, MnO2/CeO2, was characterized and used in the oxidation of phenol in a slurry reactor in the temperature range of 80-130ºC and pressure of 2.04-4.76 MPa. A phenol solution containing 2.4-dichlorophenol and 2.4-dichlorophenoxyacetic acid was also degraded with good results. A lumped kinetic model, with two parallel reaction steps, fits precisely with the integrated equation and the experimental data. The kinetic parameters obtained are in agreement with the Arrhenius equation. The activation energies were determined to be 38.4 for the total oxidation and 53.4 kJ/mol for the organic acids formed.

  13. An ionic liquid supported CeO2 nanoparticles-carbon nanotubes composite-enhanced electrochemical DNA-based sensor for the detection of Pb2+

    Institute of Scientific and Technical Information of China (English)

    Yan Lia; Xiao-Rong Liut; Xiao-Hui Ning; Can-Can Hnang; Jian-Bin Zheng; Jun-cai Zhang

    2011-01-01

    An electrochemical sensor incorporating a signal enhancement for the determination of lead (II) ions (Pb2+) was designed on the basis of the thrombin-binding aptamer (TBA) as a molecular recog- nition element and ionic liquid supported cerium oxide (CeO2) nanoparticles-carbon nanotubes compo- site modification. The composite comprises nanoparticles CeO2, multi-waU carbon nanotubes (MWNTs) and hydrophobic room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4). The electrochemical sensors were fabricated by immersing the CeOa-MWNTs-EMIMBF4 modified glassy carbon electrode (GCE) into the solution of TBA probe. In the presence of Pb2+, the TBA probe could form stable G-quartet structure by the specific binding interactions between Pb2+ and TBA. The TBA-bound Pb2+ can be electrochemically reduced, which provides a readout signal for quantitative detection of Pb2+. The reduction peak current is linearly related to the concentration of Pb2+ from 1.0 * 10-8 M to 1.0 * 105 M with a detection limit of 5 * 109 M. This work demonstrates that the CeOz-MWNTs-EMIMBF4 nanocomposite modified GCE provides a promising platform for immobi- lizing the TBA probe and enhancing the sensitivity of the DNA-based sensors.

  14. CeO2-Y2O3-ZrO2 Membrane with Enhanced Molten Salt Corrosion Resistance for Solid Oxide Membrane (SOM) Electrolysis Process

    Science.gov (United States)

    Zou, Xingli; Li, Xin; Shen, Bin; Lu, Xionggang; Xu, Qian; Zhou, Zhongfu; Ding, Weizhong

    2017-02-01

    Innovative CeO2-Y2O3-ZrO2 membrane has been successfully developed and used in the solid oxide membrane (SOM) electrolysis process for green metallic materials production. The x mol pct ceria/(8- x) mol pct yttria-costabilized zirconia ( xCe(8- x)YSZ, x = 0, 1, 4, or 7) membranes have been fabricated and investigated as the membrane-based inert anodes to control the SOM electroreduction process in molten salt. The characteristics of these fabricated xCe(8- x)YSZ membranes including their corrosion resistances in molten salt and their degradation mechanisms have been systematically investigated and compared. The results show that the addition of ceria in the YSZ-based membrane can inhibit the depletion of yttrium during the SOM electrolysis, which thus makes the ceria-reinforced YSZ-based membranes possess enhanced corrosion resistances to molten salt. The ceria/yttria-costabilized zirconia membranes can also provide reasonable oxygen ion conductivity during electrolysis. Further investigation shows that the newly modified 4Ce4YSZ ceramic membrane has the potential to be used as novel inert SOM anode for the facile and sustainable production of metals/alloys/composites materials such as Si, Ti5Si3, TiC, and Ti5Si3/TiC from their metal oxides precursors in molten CaCl2.

  15. CeO2-Y2O3-ZrO2 Membrane with Enhanced Molten Salt Corrosion Resistance for Solid Oxide Membrane (SOM) Electrolysis Process

    Science.gov (United States)

    Zou, Xingli; Li, Xin; Shen, Bin; Lu, Xionggang; Xu, Qian; Zhou, Zhongfu; Ding, Weizhong

    2016-10-01

    Innovative CeO2-Y2O3-ZrO2 membrane has been successfully developed and used in the solid oxide membrane (SOM) electrolysis process for green metallic materials production. The x mol pct ceria/(8-x) mol pct yttria-costabilized zirconia (xCe(8-x)YSZ, x = 0, 1, 4, or 7) membranes have been fabricated and investigated as the membrane-based inert anodes to control the SOM electroreduction process in molten salt. The characteristics of these fabricated xCe(8-x)YSZ membranes including their corrosion resistances in molten salt and their degradation mechanisms have been systematically investigated and compared. The results show that the addition of ceria in the YSZ-based membrane can inhibit the depletion of yttrium during the SOM electrolysis, which thus makes the ceria-reinforced YSZ-based membranes possess enhanced corrosion resistances to molten salt. The ceria/yttria-costabilized zirconia membranes can also provide reasonable oxygen ion conductivity during electrolysis. Further investigation shows that the newly modified 4Ce4YSZ ceramic membrane has the potential to be used as novel inert SOM anode for the facile and sustainable production of metals/alloys/composites materials such as Si, Ti5Si3, TiC, and Ti5Si3/TiC from their metal oxides precursors in molten CaCl2.

  16. Influence of synthesis conditions on the crystal structure of the powder formed in the ZrO2 - Ce2O3/CeO2 system.

    Science.gov (United States)

    Popov, V. V.; Menushenkov, A. P.; Khubbutdinov, R. M.; Svetogorov, R. D.; Zubavichus, Ya V.; Sharapov, A. S.; Kurilkin, V. V.

    2016-09-01

    Influence of synthesis conditions (type of atmosphere, reduction and oxidation, annealing temperature) on the chemical composition and structure of the compounds formed in the “ZrO2 - Ce2O3 / CeO2” system has been investigated by X-ray absorption fine structure (XAFS) spectroscopy combined with X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It is revealed that isothermal annealing of precursor at temperatures less than 1000 °C in air leads to formation of Ce0.5Zr0.5O2 powders with cubic fluorite-type structure (Fm-3m). Further increase of annealing temperatures above 1000 °C causes decomposition of formed crystal structure into two phases: cubic and tetragonal. Annealing in reduction hydrogen atmosphere causes formation of Ce4 + 2xCe3 + 2-2xZr2O7 + x compounds with intermediate valency of cerium, where value of x depends on the reducing conditions and treatment parameters of precursor. Annealing in vacuum at 1400 °C strongly reduces the content of Ce4+ in a powder samples and leads to formation of pyrochlore structure (space group Fd-3m) with practically Ce3+ valence state.

  17. Condutividade elétrica de CeO2-10 mol% Gd2O3 - x mol% Sm2O3 (0 < x < 2

    Directory of Open Access Journals (Sweden)

    H. E. Araujo

    2013-06-01

    Full Text Available A condutividade elétrica de CeO2-10 mol% Gd2O3 co-dopado com x mol% de Sm2O3 (0 < x < 2 foi investigada. O aumento da concentração total de dopantes com a co-dopagem não promoveu variação significativa do parâmetro de rede e do tamanho médio de grão. A adição de até 1,0% em mol de co-dopante favoreceu a condutividade elétrica do grão e acima deste teor ocorreu decréscimo, apesar de o parâmetro de rede e o tamanho médio de grão se manterem constantes. A condutividade elétrica do contorno de grão teve um aumento sistemático com a adição do co-dopante, indicando a influência da co-dopagem na camada de carga espacial.

  18. Synthesis of novel CoOx decorated CeO2 hollow structures with an enhanced photocatalytic water oxidation performance under visible light irradiation.

    Science.gov (United States)

    Fang, Siman; Li, Songsong; Ge, Lei; Han, Changcun; Qiu, Ping; Gao, Yangqin

    2017-02-01

    Cobalt oxide decorated octahedral ceria hollow structures (CoOx/CeO2) with various contents of CoOx nanoparticles were prepared via a simple chemical impregnation method. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse-reflectance spectroscopy (DRS), surface photovoltage spectroscopy (SPV) and transient photovoltage spectroscopy (TPV). The photocatalytic oxygen evolution via water oxidation was investigated for the as-prepared CoOx/CeO2 nanocage composites. The photocatalytic results indicate that the CoOx/CeO2 nanocage composite with 1 mol% CoOx shows the highest photocatalytic activity. The excellent photocatalytic activity can be attributed to the improved visible-light absorption of CoOx/CeO2 composites and the efficient separation of excited electron-hole pairs between CoOx and CeO2, which can effectively enhance the lifetime of charge carriers in the CoOx-modified samples and then improve the oxygen evolution activity. Cobalt oxide is expected to be an excellent water oxidation co-catalyst for semiconductor photocatalysts.

  19. Effects of support property on the catalytic performance of CeO2-ZrO2-CrOx for 1,2-dichloroethane oxidation

    Institute of Scientific and Technical Information of China (English)

    陶飞; 杨姗姗; 杨鹏; 石智男; 周仁贤

    2016-01-01

    HZSM-5, Al2O3, TiO2 and SiO2 supported CeO2-ZrO2-CrOx catalysts were prepared by deposition-precipitation method and tested for deep catalytic oxidation of 1,2-dichloroethane (DCE), as one of the common chlorinated organic pollutants. All the catalysts were characterized by means of N2adsorption-desorption, X-ray photoelectron spectroscopy (XPS), ammonia-temperature- programmed desorption (NH3-TPD) and hydrogen temperature-programmed reduction (H2-TPR). The characterization results re-vealed that there was strongly synergistic effect between the oxidizability of CZCr species and the acidity of supports, which obvi-ously promoted the catalytic activity for DCE degradation. 20%CZCr/HZSM-5 showed the highest activity and good durability dur-ing the long-term continuous test. The catalytic activity decreased in the order: 20%CZCr/HZSM-5>CZCr>20%CZCr/TiO2> 20%CZCr/Al2O3>20%CZCr/SiO2.

  20. Preferential oxidation of CO in excess H2 over the CeO2/CuO catalyst:Effect of initial support

    Institute of Scientific and Technical Information of China (English)

    Zhiming Gao; Yuanyuan Gong; Qiang Zhang; Hao Deng; Yong Yue

    2014-01-01

    Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperature-programmed reduction (TPR), XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu(OH)2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina-tion temperatures of 400◦C-600◦C. As a result, Cu(OH)2 is better than CuO as initial support for preferential oxidation of CO in excess H2 (CO-PROX). The best catalytic performance was achieved on the sample calcined at 600◦C and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600◦C. And the atomic ratio of Ce/Cu at 40%led to a proper reducibility for the sample as illustrated by the TPR measurements.

  1. Effect of fluorine additive on CeO2(ZrO2)/TiO2 for selective catalytic reduction of NO by NH3.

    Science.gov (United States)

    Jin, Qijie; Shen, Yuesong; Zhu, Shemin

    2017-02-01

    A series of CeO2(ZrO2)/TiO2 catalysts with fluorine additive were prepared by impregnation method and tested for selective catalytic reduction (SCR) of NO by NH3. These samples were characterized by XRD, N2-BET, Raman spectra, SEM, TEM, NH3-TPD, H2-TPR and XPS, respectively. Results showed that the optimal catalyst with the appropriate HF exhibited excellent performance for NH3-SCR and more than 96% NO conversion at 360°C under GHSV of 71,400h(-1). It was found that the grain size of TiO2 increased and the specific surface area reduced with the modulation of HF, which was not good for the adsorption of gas molecule. However, the modulation of HF exposed the high energy (001) facets of TiO2 and increased the surface chemisorbed oxygen concentration, oxygen storage capacity and Ce(3+) concentration of catalyst. In addition, the synergy of (101) and (001) facets was beneficial to the improvement of catalytic activity.

  2. Selective catalytic reduction of NO with NH3 over CeO2-ZrO2-WO3 catalysts prepared by different methods

    Science.gov (United States)

    Ning, Ping; Song, Zhongxian; Li, Hao; Zhang, Qiulin; Liu, Xin; Zhang, Jinhui; Tang, Xiaosu; Huang, Zhenzhen

    2015-03-01

    The selective catalytic reduction (SCR) of NO by NH3 has been investigated over the CeO2-ZrO2-WO3 (CZW) catalysts prepared by hydrothermal synthesis, incipient impregnation, co-precipitation and sol-gel methods. The results indicate that the CZW catalyst prepared by hydrothermal method shows the best SCR activity, and more than 90% NO conversion is obtained at 195-450 °C with a gas hourly space velocity of 50,000 h-1. The samples are characterized by XRD, N2 adsorption-desorption, SEM, EDS, XPS, H2-TPR, NH3-TPD and Pyridine-IR techniques. The results imply that the superior SCR activity of CZW catalyst is contributed to the excellent redox property, strong acidity and highest content of chemisorbed oxygen species. Furthermore, the larger surface area and greater total pore volume improve the redox ability and enhance NO conversion at low temperature, while the co-existence of Lewis and Brønsted acid sites enhance the SCR activity at high temperature.

  3. Photorefractive Properties of Potassium Lithium Niobate Crystals with CeO2 and Nd2O3

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    KLN and Ce:Nd:KLN crystals were grown by Czochralski method and polarized into single ferroelectrics domain along c-axis. The properties of KLN and Ce:Nd:KLN crystals, such as Curie temperature, Raman spectra, exponential gain coefficient (Г) and thin crystal sheet effect, were measured. The results showed that the two spectra resembling Ce:Nd:KLN crystal were of tetragonal tungsten bronze structure, the exponential gain coefficient of Ce:Nd:KLN crystal was higher than that of KLN crystals and Ce:Nd:KLN crystal had thin crystal sheet effect, for its exponential gain coefficient increasing with crystal sheet thinning. The thin crystal sheet effect of Ce:Nd:KLN crystal was also discussed.

  4. Influence of the substitution of Y2O3 for CeO2 on the mechanical and microstructural properties of silicon nitride Influência da substituição de Y2O3 por CeO2 nas propriedades mecânicas e microestruturais do nitreto de silício

    Directory of Open Access Journals (Sweden)

    J. V. C. de Souza

    2005-09-01

    Full Text Available This work investigated the substitution of Y2O3 for CeO2 in liquid-phase sintered silicon nitride ceramics. Cost reduction as well as good physical, mechanical and microstructural properties are the main objectives of the present study. Two powder mixtures were prepared, varying the contents of alpha-Si3N4, Al2O3, AlN, Y2O3 and CeO2. The mixtures were homogenized in ethanol, dried in a rotating evaporator and kiln, respectively, and then uniaxially (100 MPa and cold isostatically pressed (300 MPa. The samples were sintered at 1850ºC for 1 h in a graphite resistive furnace under nitrogen atmosphere. After sintering the density of the samples was higher than 97% of the theoretical value. The fracture toughness and hardness were higher than 5.28 MPa.m½ and 17.12 GPa, respectively. Phase analysis by X-ray diffraction and scanning electron microscopy revealed the presence of alpha-SiAlON and beta-Si3N4.Este trabalho foi proposto com objetivo de analisar a possibilidade da substituição de Y2O3 por CeO2 sinterização via fase líquida de nitreto de silício (Si3N4, visando obter um material com boas propriedades físicas, mecânicas e microestruturais, além da redução de custos de produção desta cerâmica. Para o desenvolvimento deste trabalho foram preparadas duas misturas de pós, variando-se as proporções entre alfa-Si3N4, Al2O3, AlN, Y2O3 e CeO2. As misturas de pós foram homogeneizadas em etanol, secas em evaporador rotativo e estufa, respectivamente. Em seguida, prensadas uniaxialmente (100 MPa e isostaticamente a frio(300 MPa. As amostras foram sinterizadas à 1850 ºC durante 1 h, em forno com elemento resistivo de grafite sob atmosfera de nitrogênio. Após sinterização, as amostras apresentaram densidades relativas superiores a 97% do valor teórico. A tenacidade à fratura e a dureza foram superiores a 5,28 MPa.m½ e 17,12 GPa, respectivamente. As análises de fases por difração de raios X e microscopia eletrônica de varredura mostraram a presença das fases alfa-SiAlON e beta-Si3N4.

  5. 氧化碳烟的MnOx(0.4)-CeO2催化剂表面活性物种研究%An Investigation of Surface Reactive Species on MnOx(0.4)-CeO2 Catalyst towards Soot Oxidation

    Institute of Scientific and Technical Information of China (English)

    林俊敏; 付名利; 朱文波; 叶代启

    2014-01-01

    采用柠檬酸配合燃烧法和共沉淀法制备了MnOx(0.4)-CeO2催化剂,用于模拟碳烟的燃烧.通过XRD、BET、Raman、H2-TPR、O2-TPD与XPS表征催化剂的结构和表面活性物种,并借助原位拉曼研究碳烟的催化氧化机理.结果表明柠檬酸配合燃烧法制备的MnOx(0.4)-CeO2-CA催化剂中有更多的Mn进入了CeO2的立方萤石结构,比表面积更大,氧空位、Mn4+和Ce4+更多,因而氧化还原性能更好,催化氧化碳烟的活性更高.O-在碳烟的氧化中起重要作用,Mn4+和Ce4+有利于氧化反应的进行,氧空位的增加能提高氧的吸附、迁移和转化能力,促进了碳烟的氧化.反应路径为O-溢出参与碳烟的氧化,同时产生氧空位,部分晶格氧O2-补充O-,气相氧不断吸附到氧空位上得到活化生成O2-,O2-转化为O-(可进一步转化为O2-),O-迁移至碳烟颗粒表面参与反应,生成CO2.

  6. 水热法制备高纯超细CeO2-ZrO2复合氧化物%Preparation of High Purity and Superfine CeO2-ZrO2 by Hydrothermal Method

    Institute of Scientific and Technical Information of China (English)

    郑育英; 黄慧民; 邓淑华; 李大光; 余双平

    2005-01-01

    Superfine composite powders of CeO2-ZrO2 (CZ) and CeO2-ZrO2-La2O3 (CZL) were prepared by hydrothermal method. The effects of pH ,temperature and time for hydrothermal process on the performance of the resulting powders were studied. The optimized reaction parameters were on follows: the precursor's pH≈9.0, hydrothermal temperature of 200 ℃ holding for 2 h. Thermal stable powders with average particle size smaller than 10 nm and specific surface area of 171 m2·g-1 were obtained. A BET specific surface area was still at 44 m2·g-1 after calcination at 1 000 ℃ for 6 hours.

  7. Effect of CeO2, MgO and Y2O3 additions on the sinterability of a milled Si3N4 with 14.5 wt% SiO2

    Science.gov (United States)

    Arias, A.

    1981-01-01

    The sinterability of alpha Si3N4 with 0-5.07 equivalent per cent of CeO2, MgO, or Y2O3 has been studied in the temperature range 1650-1820 C by density measurements and X-ray diffraction analysis. Maximum densities were obtained in the range 1765-1820 C and were 99.6% of theoretical with 2.5% CeO2; 98.5% of theoretical with 1.24 to 1.87% MgO, and 99.2% of theoretical with 2.5% Y2O3. Densities 94% or more of theoretical value were obtained with as little as 0.62 equivalent per cent additive.

  8. The Effect of Acidic and Redox Properties of V2O5/CeO2-ZrO2 Catalysts in Selective Catalytic Reduction of NO by NH3

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Riisager, Anders; Fehrmann, Rasmus

    2009-01-01

    V2O5 supported ZrO2 and CeO2–ZrO2 catalysts were prepared and characterized by N2 physisorption, XRPD, TPR, and NH3-TPD methods. The influence of calcination temperature from 400 to 600 °C on crystallinity, acidic and redox properties were studied and compared with the catalytic activity in the s......V2O5 supported ZrO2 and CeO2–ZrO2 catalysts were prepared and characterized by N2 physisorption, XRPD, TPR, and NH3-TPD methods. The influence of calcination temperature from 400 to 600 °C on crystallinity, acidic and redox properties were studied and compared with the catalytic activity...

  9. Au/ZrLa掺杂 CeO2催化剂在CO氧化反应中优异的催化活性:锆镧协同作用%CO oxidation over Au/ZrLa-doped CeO2 catalysts:Synergistic effect of zirconium and lanthanum

    Institute of Scientific and Technical Information of China (English)

    杨琦; 杜林颖; 王旭; 贾春江; 司锐

    2016-01-01

    在过去的25年,纳米金催化剂上 CO氧化反应得到广泛研究,但始终没有一致的结论。这是因为影响纳米金催化活性的因素很多,包括金的价态、载体的性质、氧空位、金属与载体之间的相互作用等,尤其是各影响因素之间相互牵制,增加了催化反应机理的研究难度。氧化铈载体表面氧缺陷的浓度较高,有利于活性金属组分在其表面的稳定和分散,因此氧化铈纳米晶负载的 Au催化剂受到广泛关注。此外,当 CeO2晶格中部分 Ce被化学性质不同的其它元素取代后,可以促进 CeO2晶格氧的活化,提高氧的储放能力,从而有利于催化反应进行。因此,本文采用水热法合成了组成均匀的 CeO2, CeZrOx和 CeZrLaOx三个载体,并通过沉淀-沉积法负载金。利用 X射线衍射(XRD)、拉曼光谱(Raman)、X射线光电子能谱(XPS)、高分辨透射电镜(HRTEM)、X射线吸收精细结构(XAFS)和氢气程序升温还原(H2-TPR)等技术分析了催化剂的物相结构、表面性质、形貌以及金纳米颗粒的大小和价态等性质,并结合其在 CO氧化反应中催化性能的差异,探讨影响金催化剂活性的关键因素。 ;XRD, TEM, HRTEM和 XAFS结果表明,三个载体上所得金纳米颗粒的平均尺寸都在2–4 nm,且分散较好; XPS结果表明,影响催化剂活性的关键因素不是金的价态,而是载体表面的活性氧物种。从Raman结果可知,掺杂后的氧化铈载体上氧空位浓度明显增加,因而催化剂活性都有所提高。 H2-TPR进一步探讨了三个载体以及负载金后其氧化还原能力的变化,结果表明,金和载体之间的相互作用可以增强载体的氧化还原性能以及表面氧空位浓度,进一步提高了催化剂活性,而负载金催化剂氧化还原性能的变化与载体的组成密切相关。由于锆的掺杂可使金与载体之间相互作用减弱,而镧则增强了二者间相互作用,因此 Au/CeZrLaOx催化剂上锆和镧的协同掺杂作用使其表面活性氧物种浓度最高,低温时表现出最高的催化活性。%The physicochemical properties of nanosized Au catalysts supported on doped CeO2 and their cata‐lytic performance for the CO oxidation reaction were investigated. The Au/Zr‐doped CeO2 catalyst is much more active than undoped Au/CeO2, while Au/ZrLa‐doped CeO2 shows the highest activity. Characterization of the catalysts by X‐ray diffraction, transmission electron microscopy (TEM), high‐resolution TEM, and the X‐ray absorption fine structure technique shows high homogeneity of the oxide supports and well‐dispersed nanosized Au nanoparticles. Raman spectroscopy, X‐ray photoelectron spectroscopy, and H2‐tempeature‐programmed reduction show that the surface oxygen species are the main factor for the catalytic activity in the CO oxidation reaction, while the supported Au species can improve the redox properties and create oxygen vacancy sites on the support. The oxidation state of Au is not the main factor governing the activity of Au/doped‐CeO2 catalysts. Additionally, the synergistic effect of Zr and La is discussed.

  10. Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

    Science.gov (United States)

    Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M. Younus

    2017-01-01

    Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region. PMID:28079056

  11. Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material.

    Science.gov (United States)

    Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M Younus

    2017-01-12

    Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~10(2)) and no significant data degradation during endurance test of >10(4) switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region.

  12. Endurance and Cycle-to-cycle Uniformity Improvement in Tri-Layered CeO2/Ti/CeO2 Resistive Switching Devices by Changing Top Electrode Material

    Science.gov (United States)

    Rana, Anwar Manzoor; Akbar, Tahira; Ismail, Muhammad; Ahmad, Ejaz; Hussain, Fayyaz; Talib, Ijaz; Imran, Muhammad; Mehmood, Khalid; Iqbal, Khalid; Nadeem, M. Younus

    2017-01-01

    Resistance switching characteristics of CeO2/Ti/CeO2 tri-layered films sandwiched between Pt bottom electrode and two different top electrodes (Ti and TaN) with different work functions have been investigated. RRAM memory cells composed of TaN/CeO2/Ti/CeO2/Pt reveal better resistive switching performance instead of Ti/CeO2/Ti/CeO2/Pt memory stacks. As compared to the Ti/CeO2 interface, much better ability of TaN/CeO2 interface to store and exchange plays a key role in the RS performance improvement, including lower forming/SET voltages, large memory window (~102) and no significant data degradation during endurance test of >104 switching cycles. The formation of TaON thinner interfacial layer between TaN TE and CeO2 film is found to be accountable for improved resistance switching behavior. Partial charge density of states is analyzed using density functional theory. It is found that the conductive filaments formed in CeO2 based devices is assisted by interstitial Ti dopant. Better stability and reproducibility in cycle-to-cycle (C2C) resistance distribution and Vset/Vreset uniformity were achieved due to the modulation of current conduction mechanism from Ohmic in low field region to Schottky emission in high field region.

  13. Dopant-induced modification of active site structure and surface bonding mode for high-performance nanocatalysts: CO oxidation on capping-free (110)-oriented CeO2:Ln (Ln = La-Lu) nanowires.

    Science.gov (United States)

    Ke, Jun; Xiao, Jia-Wen; Zhu, Wei; Liu, Haichao; Si, Rui; Zhang, Ya-Wen; Yan, Chun-Hua

    2013-10-09

    Active center engineering at atomic level is a grand challenge for catalyst design and optimization in many industrial catalytic processes. Exploring new strategies to delicately tailor the structures of active centers and bonding modes of surface reactive intermediates for nanocatalysts is crucial to high-efficiency nanocatalysis that bridges heterogeneous and homogeneous catalysis. Here we demonstrate a robust approach to tune the CO oxidation activity over CeO2 nanowires (NWs) through the modulation of the local structure and surface state around Ln(Ce)' defect centers by doping other lanthanides (Ln), based on the continuous variation of the ionic radius of lanthanide dopants caused by the lanthanide contraction. Homogeneously doped (110)-oriented CeO2:Ln NWs with no residual capping agents were synthesized by controlling the redox chemistry of Ce(III)/Ce(IV) in a mild hydrothermal process. The CO oxidation reactivity over CeO2:Ln NWs was dependent on the Ln dopants, and the reactivity reached the maximum in turnover rates over Nd-doped samples. On the basis of the results obtained from combined experimentations and density functional theory simulations, the decisive factors of the modulation effect along the lanthanide dopant series were deduced as surface oxygen release capability and the bonding configuration of the surface adsorbed species (i.e., carbonates and bicarbonates) formed during catalytic process, which resulted in the existence of an optimal doping effect from the lanthanide with moderate ionic radius.

  14. Effect of CeO2 and Al2O3 on the activity of Pd/Co3O4/cordierite catalyst in the three-way catalysis reactions (CO/NO/CnHm)

    Institute of Scientific and Technical Information of China (English)

    Sergiy O. Soloviev; Pavlo I. Kyriienko; Nataliia O. Popovych

    2012-01-01

    The present article studies the effect of CeO2 and Al2O3 on the activity of Pd/Co3O4/cordierite catalyst in conversion of NO,CO,CnHm.The catalysts were characterized by temperature programmed reduction with hydrogen,X-ray diffraction,X-ray photoelectron spectroscopy and transmission electron microscopy.It is shown that the effect of CeO2 on the properties of Pd/Co3O4/cordierite catalyst depends on preparation method.The catalyst obtained by co-deposition of cerium and cobalt oxides has higher activity in CO oxidation (CO + O2 and CO + NO) and total hexane oxidation (C6H14 + O2).Such phenomenon is probably caused by more than stoichiometric amount of formed oxygen vacancies,an increase in both mobility of surface oxygen and dispersity of components in the catalytic composition.It is demonstrated that CeO2 addition promotes the SO2 resistance of Pd/Co3O4/cordierite.The second support decreases the activity of Pd/Co3O4/cordierite catalyst in the reactions of CO and C6H14 with oxygen because of CoAl2O4 formation.

  15. Structures and oxygen storage capacities of CeO2-ZrO2-Al2O3 ternary oxides prepared by a green route: supercritical anti-solvent precipitation

    Institute of Scientific and Technical Information of China (English)

    HUANG Pan; JIANG Haoxi; ZHANG Minhua

    2012-01-01

    CeO2-ZrO2-Al2O3 ternary oxides were successfully prepared by a green route of supercritical anti-solvent precipitation with supercritical CO2 as anti-solvent and methanol as solvent.The structures and oxygen storage capacities of these ternary oxides were characterized by XRD,Raman spectra and oxygen storage capacity measurements.It was found that Al3+ and Zr4+ inserted into CeO2 lattice,forming CeO2-ZrO2-Al2O3 solid solution.The concentration of aluminium isopropoxide in the solution affected the concentration of oxygen vacancy and the distortion of oxygen sublattice which were responsible for the oxygen storage capacity.The rapidest oxygen uptake/release rate and maximum total oxygen storage capacity (122.0 mmolO2/molCeO2) were obtained with the aluminium isopropoxide concentration at 0.2 wt.% in the solution.

  16. Effects of Doping CeO2, Er2O3 on Properties of TiO2-SiO2 Ceramics for Catalyst Supporter of deNOx

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Effects of doping CeO2 and Er2O3 on the mechanical strength, thermal expansion coefficient, sintering temperature of TiO2-SiO2 ceramics were investigated. The experimental results and the microscopic analysis of SEM, XRD, TG-DSC, FT-IR and TEM show that adding CeO2 and Er2O3 into TiO2-SiO2 ceramics can prohibit the growth of its crystal grains, make their size uniform and form them into a dense structure, which finally enhance its mechanical behaviors, and the lower thermal expansion coefficient that leads to an excellent property of thermal shock resistance. After the reforming TiO2-SiO2 ceramics doped by CeO2 was sintered at 1380 ℃, the bending strength reached to 83 MPa, and the thermal expansion coefficient was 9.8×10-6/℃ within the temperature range of 25~800 ℃, which provides a promising basis of making equipped honeycomb catalyst of deNOx.

  17. Effect of Ce doping of TiO2 support on NH3-SCR activity over V2O5-WO3/CeO2-TiO2 catalyst.

    Science.gov (United States)

    Cheng, Kai; Liu, Jian; Zhang, Tao; Li, Jianmei; Zhao, Zhen; Wei, Yuechang; Jiang, Guiyuan; Duan, Aijun

    2014-10-01

    CeO2-TiO2 composite supports with different Ce/Ti molar ratios were prepared by a homogeneous precipitation method, and V2O5-WO3/CeO2-TiO2 catalysts for the selective catalytic reduction (SCR) of NOx with NH3 were prepared by an incipient-wetness impregnation method. These catalysts were characterized by means of BET, XRD, UV-Vis, Raman and XPS techniques. The results showed that the catalytic activity of V2O5-WO3/TiO2 was greatly enhanced by Ce doping (molar ratio of Ce/Ti=1/10) in the TiO2 support. The catalysts that were predominantly anatase TiO2 showed better catalytic performance than the catalysts that were predominantly fluorite CeO2. The Ce additive could enhance the surface adsorbed oxygen and accelerate the SCR reaction. The effects of O2 concentration, ratio of NH3/NO, space velocity and SO2 on the catalytic activity were also investigated. The presence of oxygen played an important role in NO reduction. The optimal ratio of NH3/NO was 1/1 and the catalyst had good resistance to SO2 poisoning.

  18. Characterization and catalytic performance of CeO2-Co/SiO2 catalyst for Fischer-Tropsch synthesis using nitrogen-diluted synthesis gas over a laboratory scale fixed-bed reactor

    Institute of Scientific and Technical Information of China (English)

    Xiaoping Dai; Changchun Yu

    2008-01-01

    The surface species of CO hydrogenation on CeO2-Co/SiO2 catalyst were investigated using the techniques of temperature programmed reaction and transient response method. The results indicated that the formation of H2O and CO2 was the competitive reaction for the surface oxygen species, CH4 was produced via the hydrogenation of carbon species step by step, and C2 products were formed by the polymerization of surface-active carbon species (-CH2-). Hydrogen assisted the dissociation of CO. The hydrogenation of surface carbon species was the rate-limiting step in the hydrogenation of CO over CeO2-Co/SiO2 catalyst. The investigation of total pressure, gas hourly space velocity (GHSV), and product distribution using nitrogen-rich synthesis gas as feedstock over a laboratory scale fixed-bed reactor indicated that total pressure and GHSV had a significant effect on the catalytic performance of CeO2-Co/SiO2 catalyst. The removal of heat and control of the reaction temperature were extremely critical steps, which required lower GHSV and appropriate CO conversion to avoid the deactivation of the catalyst. The feedstock of nitrogen-rich synthesis gas was favorable to increase the conversion of CO, but there was a shift of product distribution toward the light hydrocarbon. The nitrogen-rich synthesis gas was feasible for F-T synthesis for the utilization of remote natural gas.

  19. On The Protection by The Combination of CeO2 Nanoparticles and Sodium Selenite on Human Lymphocytes against Chlorpyrifos-Induced Apoptosis In Vitro

    Directory of Open Access Journals (Sweden)

    Sahar Pedram

    2015-07-01

    Full Text Available Objective: Chlorpyrifos (CP as an organophosphorus pesticide is thought to induce oxidative stress in human cells via producing reactive oxygen species (ROS that leads to the presence of pathologic conditions due to apoptosis along with acetylcholinesterase (AChE inhibition.This study aimed to evaluate the apoptotic effects of CP and to assess the protective potential of CeO2 nanoparticle (CNP and sodium selenite (SSe by measuring cascades of apoptosis, oxidative stress, inflammation, and AChE inhibition in human isolated lymphocytes. Materials and Methods: In the present experimental study, we examined the anti-oxidative and AChE activating potential of CNP and SSe in CP-treated human lymphocytes. Therefore, the lymphocytes were isolated and exposed to CP, CP+CNP, CP+SSe, and CP+CNP+SSe after a three-day incubation. Then tumor necrosis factor-alpha (TNF-α release, myeloperoxidase (MPO activity, thiobarbituric acid-reactive substances (TBARS levels as inflammatory/oxidative stress indices along with AChE activity were assessed. In addition, the apoptotic process was measured by flow cytometry. Results: Results showed a significant reduction in the mortality rate, TNF-α, MPO activity, TBARS, and apoptosis rate in cells treated with CNP, SSe and their combination. Interestingly, both CNP and SSe were able to activate AChE which is inhibited by CP. The results supported the synergistic effect of CNP/SSe combination in the prevention of apoptosis along with oxidative stress and inflammatory cascade. Conclusion: CP induces apoptosis in isolated human lymphocytes via oxidative stress and inflammatory mediators. CP firstly produces ROS, which leads to membrane phospholipid damage. The beneficial effects of CNP and SSe in reduction of CP-induced apoptosis and restoring AChE inhibition relate to their anti-oxidative potentials.

  20. DNA damage and oxidative stress induced by CeO2 nanoparticles in human dermal fibroblasts: Evidence of a clastogenic effect as a mechanism of genotoxicity.

    Science.gov (United States)

    Benameur, Laila; Auffan, Mélanie; Cassien, Mathieu; Liu, Wei; Culcasi, Marcel; Rahmouni, Hidayat; Stocker, Pierre; Tassistro, Virginie; Bottero, Jean-Yves; Rose, Jérôme; Botta, Alain; Pietri, Sylvia

    2015-01-01

    The broad range of applications of cerium oxide (CeO2) nanoparticles (nano-CeO2) has attracted industrial interest, resulting in greater exposures to humans and environmental systems in the coming years. Their health effects and potential biological impacts need to be determined for risk assessment. The aims of this study were to gain insights into the molecular mechanisms underlying the genotoxic effects of nano-CeO2 in relation with their physicochemical properties. Primary human dermal fibroblasts were exposed to environmentally relevant doses of nano-CeO2 (mean diameter, 7 nm; dose range, 6 × 10(-5)-6 × 10(-3) g/l corresponding to a concentration range of 0.22-22 µM) and DNA damages at the chromosome level were evaluated by genetic toxicology tests and compared to that induced in cells exposed to micro-CeO2 particles (mean diameter, 320 nm) under the same conditions. For this purpose, cytokinesis-blocked micronucleus assay in association with immunofluorescence staining of centromere protein A in micronuclei were used to distinguish between induction of structural or numerical chromosome changes (i.e. clastogenicity or aneuploidy). The results provide the first evidence of a genotoxic effect of nano-CeO2, (while not significant with micro-CeO2) by a clastogenic mechanism. The implication of oxidative mechanisms in this genotoxic effect was investigated by (i) assessing the impact of catalase, a hydrogen peroxide inhibitor, and (ii) by measuring lipid peroxidation and glutathione status and their reversal by application of N-acetylcysteine, a precusor of glutathione synthesis in cells. The data are consistent with the implication of free radical-related mechanisms in the nano-CeO2-induced clastogenic effect, that can be modulated by inhibition of cellular hydrogen peroxide release.

  1. Contribution of energetically reactive surface features to the dissolution of CeO2 and ThO2 analogues for spent nuclear fuel microstructures.

    Science.gov (United States)

    Corkhill, Claire L; Myllykylä, Emmi; Bailey, Daniel J; Thornber, Stephanie M; Qi, Jiahui; Maldonado, Pablo; Stennett, Martin C; Hamilton, Andrea; Hyatt, Neil C

    2014-08-13

    In the safety case for the geological disposal of nuclear waste, the release of radioactivity from the repository is controlled by the dissolution of the spent fuel in groundwater. There remain several uncertainties associated with understanding spent fuel dissolution, including the contribution of energetically reactive surface sites to the dissolution rate. In this study, we investigate how surface features influence the dissolution rate of synthetic CeO2 and ThO2, spent nuclear fuel analogues that approximate as closely as possible the microstructure characteristics of fuel-grade UO2 but are not sensitive to changes in oxidation state of the cation. The morphology of grain boundaries (natural features) and surface facets (specimen preparation-induced features) was investigated during dissolution. The effects of surface polishing on dissolution rate were also investigated. We show that preferential dissolution occurs at grain boundaries, resulting in grain boundary decohesion and enhanced dissolution rates. A strong crystallographic control was exerted, with high misorientation angle grain boundaries retreating more rapidly than those with low misorientation angles, which may be due to the accommodation of defects in the grain boundary structure. The data from these simplified analogue systems support the hypothesis that grain boundaries play a role in the so-called "instant release fraction" of spent fuel, and should be carefully considered, in conjunction with other chemical effects, in safety performance assessements for the geological disposal of spent fuel. Surface facets formed during the sample annealing process also exhibited a strong crystallographic control and were found to dissolve rapidly on initial contact with dissolution medium. Defects and strain induced during sample polishing caused an overestimation of the dissolution rate, by up to 3 orders of magnitude.

  2. Synergy of CuO and CeO2 combination for mercury oxidation under low-temperature selective catalytic reduction atmosphere

    KAUST Repository

    Li, Hailong

    2016-07-19

    Synergy for low temperature Hg0 oxidation under selective catalytic reduction (SCR) atmosphere was achieved when copper oxides and cerium oxides were combined in a CuO-CeO2/TiO2 (CuCeTi) catalyst. Hg0 oxidation efficiency as high as 99.0% was observed on the CuCeTi catalyst at 200 °C, even the gas hourly space velocity was extremely high. To analyze the synergistic effect, comparisons of catalyst performance in the presence of different SCR reaction gases were systematically conducted over CuO/TiO2 (CuTi), CeO2/TiO2 (CeTi) and CuCeTi catalysts prepared by sol-gel method. The interactions between copper oxides and cerium oxides in CuCeTi catalyst yielded more surface chemisorbed oxygen, and facilitated the conversion of gas-phase O2 to surface oxygen, which are favorable for Hg0 oxidation. Copper oxides in the combination interacted with NO forming more chemisorbed oxygen for Hg0 oxidation in the absence of gas-phase O2. Cerium oxides in the combination promoted Hg0 oxidation through enhancing the transformations of NO to NO2. In the absence of NO, NH3 exhibited no inhibitive effect on Hg0 oxidation, because enough Lewis acid sites due to the combination of copper oxides and cerium oxides scavenged the competitive adsorption between NH3 and Hg0. In the presence of NO, although NH3 lowered Hg0 oxidation rate through inducing reduction of oxidized mercury, complete recovery of Hg0 oxidation activity over the CuCeTi catalyst was quickly achieved after cutting off NH3. This study revealed the synergistic effect of the combination of copper oxides and cerium oxides on Hg0 oxidation, and explored the involved mechanisms. Such knowledge would help obtaining maximum Hg0 oxidation co-benefit from SCR units in coal-fired power plants.

  3. Structural characterization of CeO(2)-ZrO(2)/TiO(2) and V(2)O(5)/CeO(2)-ZrO(2)/TiO(2) mixed oxide catalysts by XRD, Raman spectroscopy, HREM, and other techniques.

    Science.gov (United States)

    Reddy, Benjaram M; Lakshmanan, Pandian; Khan, Ataullah; López-Cartes, Carlos; Rojas, Teresa C; Fernandez, Asunción

    2005-02-10

    Structural characteristics of CeO(2)-ZrO(2)/TiO(2) (CZ/T) and V(2)O(5)/CeO(2)-ZrO(2)/TiO(2) (V/CZ/T) mixed oxide catalysts have been investigated using X-ray diffraction (XRD), BET surface area, Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HREM) techniques. The CeO(2)-ZrO(2) (1:1 mole ratio) solid solution was deposited over a finely powdered TiO(2) support by a deposition precipitation method. A nominal 5 wt % V(2)O(5) was impregnated over the calcined (773 K) CZ/T mixed oxide carrier by a wet impregnation technique. The obtained CZ/T and V/CZ/T samples were further subjected to thermal treatments from 773 to 1073 K to understand the dispersion and temperature stability of these materials. In the case of CZ/T samples, the XRD results suggest the formation of different cubic and tetragonal Ce-Zr-oxide phases, Ce(0.75)Zr(0.25)O(2), Ce(0.6)Zr(0.4)O(2), Ce(0.5)Zr(0.5)O(2), and Ce(0.16)Zr(0.84)O(2) in varying proportions depending on the treatment temperature. With increasing calcination temperature from 773 to 1073 K, the intensity of the lines pertaining to cubic Ce(0.6)Zr(0.4)O(2) and Ce(0.5)Zr(0.5)O(2) phases increased at the expense of cubic Ce(0.75)Zr(0.25)O(2), indicating more incorporation of zirconia into the ceria lattice. The TiO(2) was mainly in the anatase form whose crystallite size also increased with increasing treatment temperature. A better crystallization and more incorporation of zirconia into the ceria lattice was noted when CZ/T was impregnated with V(2)O(5). However, no crystalline V(2)O(5) could be seen from both XRD and RS measurements. In particular, a preferential formation of CeVO(4) compound and an intense tetragonal Ce(0.16)Zr(0.84)O(2) phase were noted beyond 873 K. The HREM results indicate, in the case of CZ/T samples, a well-dispersed Ce-Zr-oxide of the size approximately 5 nm over the bigger crystals ( approximately 40 nm) of TiO(2) when treated at 873 K. The exact structural features of these crystals as determined by digital diffraction analysis of experimental images reveal that the Ce-Zr-oxides are mainly in the cubic fluorite geometry and the TiO(2) is in anatase form. A better crystallization of Ce-Zr-oxides ( approximately 8 nm) over the surface of bigger crystals of TiO(2) was noted at 1073 K. A further enhancement in the crystallite size and zirconia-rich tetragonal phase was noted in the case of V/CZ/T samples. Further, the structure of CeVO(4) formed was also clearly identified in conformity with XRD and RS results.

  4. Effect of palladium precursor on the performance of nanorods CeO2-supported palladium catalyst for toluene catalytic combustion%钯前驱体对纳米棒 CeO2载钯催化剂催化甲苯燃烧性能的影响

    Institute of Scientific and Technical Information of China (English)

    谷广锋; 王红培; 韩玉香; 万海勤; 郑寿荣; 许昭怡

    2015-01-01

    针对挥发性有机物污染日益严重问题,本文采用水热法制备了纳米棒二氧化铈,并以其为载体,通过浸渍法制备了不同前驱体的 Pd/CeO2催化剂。采用透射电子显微镜、X 射线衍射、X 射线光电子能谱和氢气程序升温还原等手段对催化剂进行了表征,并在微型固定床反应器上评价了催化剂催化甲苯的燃烧性能。结果表明:在采用不同前驱体制备的 Pd/CeO2催化剂中, Pd 均以 Pd2+的形式存在于纳米棒状 CeO2表面;在以硝酸钯和氯化钯为前驱体的 Pd/CeO2催化剂中,前者具有更低的氢气还原温度,同时在甲苯催化燃烧反应中显示出更低的 t50和 t90,分别为219和236℃。结果表明,以硝酸钯为前驱体的催化剂具有更高的催化活性。%For the problem of volatile organic compounds pollution increasing seriously,palladium catalysts with various precur-sors supported on CeO2 nanorods were prepared by impregnation method.These catalysts were characterized using transmission electron microscopy (TEM),X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS)and H2 temperature pro-grammed reduction.The catalytic performance of these catalysts for toluene combustion was evaluated in a fixed-bed microreac-tor.The results show that palladium highly dispersed on the CeO2 nanorods surface as Pd2+ states in all the Pd/CeO2 catalysts with various precursors.Pd-N/CeO2 (palladium nitrate as precursor)shows a lower reduction temperature than that of Pd-C/CeO2 (palladium chloride as precursor),and show a lower t50 and t90 at 219 and 236 ℃,respectively,in toluene catalytic combus-tion,indicating that Pd-N/CeO2 possesses higher catalytic activity than that over Pd-C/CeO2 .

  5. CeO2对铌硅基超高温合金硅化物渗层组织及抗氧化性能的影响%Effect of CeO2 on microstructure and oxidation resistance of silicide coatings prepared on Nb­silicide­based ultrahigh temperature alloy

    Institute of Scientific and Technical Information of China (English)

    张艺; 郭喜平

    2013-01-01

      采用Si­CeO2包埋共渗工艺于1150℃在铌硅基超高温合金表面制备Si­Ce共渗层,分析渗剂中CeO2粉含量对共渗层组织、相组成及高温抗氧化性能的影响。结果表明:Si­Ce 共渗层的组织、结构与单独渗硅层的相似,由(Nb, X)Si2(X表示Ti、Hf和Cr)外层、(Ti, Nb)5Si4过渡层和富Al扩散层组成。EDS分析结果表明,Ce在共渗层中的分布不均匀,而在由原基体合金中的(Nb, X)5Si3块转变而成的富Hf (Nb, X)Si2相中含量较高。渗剂中添加CeO2不仅起到了细化渗层组织的作用,而且起到了明显的催渗作用,当渗剂中CeO2粉含量为3%(质量分数)时催渗效果更显著。Si­Ce共渗层及单独渗硅层经1250℃氧化50 h后的氧化膜均主要由TiO2与SiO2组成。但Si­Ce共渗层试样的氧化膜中TiO2棒更细小,并且在SiO2基体中的分布也更均匀,因而能显著改善氧化膜的粘附性与致密性,进而提高Si­Ce共渗层的高温抗氧化性能。%Si­Ce co­deposition coatings were prepared on an Nb­silicide­based ultrahigh temperature alloy by pack cementation processes at 1 150℃for 8 h. The effects of CeO2 content in pack mixtures on the microstructure, constituent phases and high temperature oxidation resistance of the coatings were studied. The results show that all coatings prepared with different contents of CeO2 in the pack mixtures are mainly composed of a (Nb, X)Si2 (X represents Ti, Hf and Cr) outer layer, a (Ti, Nb)5Si4 transitional layer and an Al­rich diffusion zone, which are similar to that of purely siliconized coatings. EDS analysis reveals that the distribution of Ce in the co­deposition coatings is not uniform. The content of Ce in the Hf­rich (Nb, X)Si2 phase transferred from (Nb, X)5Si3 in the base alloy is higher than that in other phases. The addition of CeO2 in the pack mixtures not only refines the microstructure of the coatings, but also obviously catalyzes the coating growth, especially when 3%CeO2 (mass fraction) is added in the pack mixtures. Both scales formed on the Si­Ce co­deposition coating and purely siliconized coating after oxidation at 1 250℃for 50 h are mainly composed of TiO2 and SiO2. However, much finer TiO2 rods are observed distributing evenly in the scale of the Si­Ce co­deposition coating after oxidation. Thus, the Si­Ce co­deposition coatings enhance the high temperature oxidation resistance due to the improved compactness of the protective oxide scale.

  6. Workshop on moisture buffer capacity

    DEFF Research Database (Denmark)

    2003-01-01

    Summary report of a Nordtest workshop on moisture buffer capacity held at Copenhagen August 21-22 2003......Summary report of a Nordtest workshop on moisture buffer capacity held at Copenhagen August 21-22 2003...

  7. Catalytic Oxidation of Propene over Pd Catalysts Supported on CeO2, TiO2, Al2O3 and M/Al2O3 Oxides (M = Ce, Ti, Fe, Mn

    Directory of Open Access Journals (Sweden)

    Sonia Gil

    2015-04-01

    Full Text Available In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2 and TiO2 in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn when added to a Pd/Al2O3 catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2 adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2 as the support was less easily reducible, due to the stabilization effect of CeO2 over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3 catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3 catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2 showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO experiments.

  8. Effect of CeO2 on the Property of Zn-Ni/CeO2 Composite Coating%CeO2对Zn-Ni/CeO2复合镀层的影响

    Institute of Scientific and Technical Information of China (English)

    郑振; 李宁; 黎德育; 孟繁宇

    2012-01-01

    采用电沉积方法,通过向镀液中加入不同粒径的CeO2颗粒,制得Zn-Ni/微米CeO2复合镀层和Zn-Ni/纳米CeO2复合镀层,研究了CeO2粒子的大小和加入量对镀层微观形貌、相组成、CeO2在镀层中的复合量以及镀层耐蚀性的影响.结果表明:大量加入CeO2,可使镀层呈现块状的“饼干”结构,并能提高镀层的耐蚀性,此外还可以抑制Ni的沉积,加入10 g/L纳米CeO2时,镀层的合金相主要为Ni2Zn11相,其它Zn-Ni合金相则较少;相比之下,在提高镀层CeO2复合量方面,微米级CeO2效果较好,在提高镀层耐蚀性方面,纳米级CeO2的效果较好.%The Ni-Zn/micro-CeO2 composite material and Ni-Zn/nano-CeO2 composite material were produced by electrodeposition method through adding micro- and nano-CeO2 particles in the Zn-Ni plating bath. The effects of the diameter and the concentration of the CeO2 particles on the microtopography, phase component, CeO2 content and the corrosion resistance of the Ni-Zn coating were studied. The result shows that when the concentration of the CeO2 particles is high, the Ni deposition is inhibited; The composite coatings are characterized with laminate morphology with good corrosion resistance. When the concentration of the nano-CeO2 particles is 10 g/L, the major alloy phase is Ni2Zn11. Compared with the nano-composite coating, the CeO2 content is larger in the micro-CeO2 composite coating. But the corrosion resistance of the nano-CeO2 composite coating is larger than that of the micro-CeO2 ones.

  9. Restriction endonucleases digesting DNA in PCR buffer

    Institute of Scientific and Technical Information of China (English)

    LIU Xue-dong; ZHENG Dong; ZHOU Yan-na; MAO Wei-wei; MA Jian-zhang

    2005-01-01

    Six commonly used restriction endonucleases (Res) (Acc I, Ban II, EcoR I, Hind III, Sac I, Sca I) were tested for their ability to directly digest DNA completely in the Polymerase Chain Reaction (PCR) buffers. The results showed that: with the requirement for additional magnesium supplemented as activator, Res, except EcoR I appeared star activity, completely digested unmethylated lambda DNA after overnight incubation in PCR buffer and functioned as equally well as in recommended Restriction Enzyme Buffer provided with each enzyme; all Res tested completely digested PCR products in PCR buffer, it implied digestion of PCR products may often be performed directly in the PCR tube without the requirement for any precipitation or purification steps; and the concentration of MgCl2 from 2.5 mmol·L-1 to 10 mmol·L-1 did not significantly affect activity of Res in PCR buffer. This simplified method for RE digestion of PCR products could have applications in restriction fragment length polymorphism (RFLP) analysis and single-stranded conformational polymorphism (SSCP) analysis of large PCR products. However, usage of this procedure for cloning applications needs further data.

  10. 稀土元素 Gd 掺杂 CeO2(111)面储释氧性能的第一性原理研究%First principles study of the oxygen storage/release properties for the Gd doped CeO2 (111) surface

    Institute of Scientific and Technical Information of China (English)

    常培荣

    2015-01-01

    本文采用第一性原理平面波超软赝势方法,研究了Gd掺杂CeO2改性材料应用于固体氧化物电池电解质时的表面储释氧性能.对比研究了三种表面覆盖率Ce1-xGdxO2(x=0,0.10,0.15)下掺杂元素Gd对CeO2的晶体结构、电子结构、氧缺陷形成过程以及表面积碳过程的影响.计算给出了相应掺杂比例下的氧缺陷形成能以及晶体表面吸附石墨烯的吸附能;结果表明:随着掺杂量的增大,氧缺陷形成能减小,晶体表面对石墨烯的吸附能增大;分析掺杂前后改性催化材料的电子结构的变化;说明Gd掺杂会导致CeO2晶体表面结构畸变收缩,有效活化表面氧,同时利用化学平衡原理证明了Gd掺杂后的催化材料可以有效抑制表面碳沉积.从理论的角度解释了Gd掺杂CeO2改性材料在固体氧化物电解质应用中的优势.%A first-principles plane-wave pseudopotential method was used to investigate the Oxygen Storage/Re-lease Properties of a new type of modified catalytic materials-Gd doped CeO2 for applications in the Solid oxide fuel cells.A comparative study was carried out using three differently doped materials, Ce1-x Gdx O2 ( x =0, 0.10, 0.15.The effects of doped element Gd on ceria 111 surface.Such as electronic structure, crystal struc-ture, formation of oxygen defect, and surface carbon deposition were studied.The energies of oxygen defect for-mation and adsorption on graphene surface under different doping ratios were obtained through calculation.The results indicate that the energy of oxygen defect formation decreased with the doping ratio increasing, while the energy of the crystal surface adsorbing graphene increases with the increase in doping ratio.While the energy of adsorption on graphene surface increase with the increase in doping ratio.According to the variation in the elec-tronic and atomic structures before and after the doping Gd, the doping caused the distortion and contraction of crystal surface structure.Resulting in the efficient activation of surface oxygen atoms.Simultaneously, the Gd-doped catalytic materials effectively restrained the surface carbon deposition, as explained by the principle of chemical equilibrium.Thus, Gd-doped CeO2 materials are advantageous as an electrolyte in solid oxide fuel cells.

  11. Catalytic oxidation of volatile organic compounds (n-hexane, benzene, toluene, o-xylene promoted by cobalt catalysts supported on γ-Al2O3-CeO2

    Directory of Open Access Journals (Sweden)

    R. Balzer

    2014-09-01

    Full Text Available Cobalt catalysts supported on γ-alumina, ceria and γ-alumina-ceria, with 10 or 20%wt of cobalt load, prepared by the wet impregnation method and characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, field emission transmission electron microscopy (FETEM, N2 adsorption-desorption isotherms (BET/BJH methods, energy-dispersive X-ray spectroscopy (EDX, X-ray photoemission spectroscopy (XPS, O2-chemisorption and temperature programmed reduction (TPR were used to promote the oxidation of volatile organic compounds (n-hexane, benzene, toluene and o-xylene. For a range of low temperatures (50-350 °C, the activity of the catalysts with a higher cobalt load (20% wt was greater than that of the catalysts with a lower cobalt load (10% wt. The Co/γ-Al2O3-CeO2 catalytic systems presented the best performances. The results obtained in the characterization suggest that the higher catalytic activity of the Co20/γ-Al2O3-CeO2 catalyst may be attributed to the higher metal content and amount of oxygen vacancies, as well as the effects of the interaction between the cobalt and the alumina and cerium oxides.

  12. Investigation of formaldehyde oxidation over Co3O4-Ce2 and Au/Co3O4-CeO2 catalysts at room temperature: effective removal and determination of reaction mechanism.

    Science.gov (United States)

    Ma, Chunyan; Wang, Donghui; Xue, Wenjuan; Dou, Baojuan; Wang, Hailin; Hao, Zhengping

    2011-04-15

    Formaldehyde is regarded as the major indoor pollutant emitted from widely used building and decorative materials in airtight buildings, which should be eliminated under indoor environmental conditions. We report here catalytic oxidation process of formaldehyde over mesoporous Co(3)O(4), Co(3)O(4)-CeO(2), Au/Co(3)O(4), and Au/Co(3)O(4)-CeO(2) catalysts and their excellent catalytic performances at room temperature. These catalysts were prepared by a "nanocasting" method with the mesostructure generated from SBA-15 silica with 2D structure. The adsorbed surface species in the formaldehyde oxidation process are analyzed, and some key steps in the oxidation pathway, active sites, and intermediate species are proposed. Among the detected species, some kinds of formate species formed on the catalysts were indentified as intermediates, which further transformed into bicarbonate or carbonate and which decomposed to carbon dioxide. The role of the mesoporous Co(3)O(4) and the gold nanoparticles in the mechanism are also revealed.

  13. Development of Xe and Kr empirical potentials for CeO2, ThO2, UO2 and PuO2, combining DFT with high temperature MD

    Science.gov (United States)

    Cooper, M. W. D.; Kuganathan, N.; Burr, P. A.; Rushton, M. J. D.; Grimes, R. W.; Stanek, C. R.; Andersson, D. A.

    2016-10-01

    The development of embedded atom method (EAM) many-body potentials for actinide oxides and associated mixed oxide (MOX) systems has motivated the development of a complementary parameter set for gas-actinide and gas-oxygen interactions. A comprehensive set of density functional theory (DFT) calculations were used to study Xe and Kr incorporation at a number of sites in CeO2, ThO2, UO2 and PuO2. These structures were used to fit a potential, which was used to generate molecular dynamics (MD) configurations incorporating Xe and Kr at 300 K, 1500 K, 3000 K and 5000 K. Subsequent matching to the forces predicted by DFT for these MD configurations was used to refine the potential set. This fitting approach ensured weighted fitting to configurations that are thermodynamically significant over a broad temperature range, while avoiding computationally expensive DFT-MD calculations. The resultant gas potentials were validated against DFT trapping energies and are suitable for simulating combinations of Xe and Kr in solid solutions of CeO2, ThO2, UO2 and PuO2, providing a powerful tool for the atomistic simulation of conventional nuclear reactor fuel UO2 as well as advanced MOX fuels.

  14. Evidence of Coulomb correction and spinorbit coupling in rare-earth dioxides CeO 2, PrO 2 and TbO 2: An ab initio study

    KAUST Repository

    Kanoun, Mohammed

    2012-04-01

    The current study investigates the structural, elastic, electronic and optical properties of CeO 2, PrO 2 and TbO 2 using the full potential (linearized) augmented plane wave plus local orbital method within the WuCohen generalized gradient approximation (GGA) with Hubbard (U) correction and spinorbit coupling (SOC). The GGAU implementation lead us to describe correctly the relativistic effect on 4f electrons for CeO 2. We clarify that the inclusion of the Hubbard U parameter and the spinorbit coupling are responsible for the ferromagnetic insulating of PrO 2 and TbO 2. The magnetic description is achieved by the spin-density contours and magnetic moment calculations, where we show the polarization of oxygen atoms from the rare earth atoms. The mechanical stability is shown via the elastic constants calculations. The optical properties, namely the dielectric function and the reflectivity are calculated for radiation up to 12 eV, giving interesting optoelectronic properties to these dioxides. © 2011 Elsevier B.V. All rights reserved.

  15. Development of Xe and Kr empirical potentials for CeO2, ThO2, UO2 and PuO2, combining DFT with high temperature MD.

    Science.gov (United States)

    Cooper, M W D; Kuganathan, N; Burr, P A; Rushton, M J D; Grimes, R W; Stanek, C R; Andersson, D A

    2016-10-12

    The development of embedded atom method (EAM) many-body potentials for actinide oxides and associated mixed oxide (MOX) systems has motivated the development of a complementary parameter set for gas-actinide and gas-oxygen interactions. A comprehensive set of density functional theory (DFT) calculations were used to study Xe and Kr incorporation at a number of sites in CeO2, ThO2, UO2 and PuO2. These structures were used to fit a potential, which was used to generate molecular dynamics (MD) configurations incorporating Xe and Kr at 300 K, 1500 K, 3000 K and 5000 K. Subsequent matching to the forces predicted by DFT for these MD configurations was used to refine the potential set. This fitting approach ensured weighted fitting to configurations that are thermodynamically significant over a broad temperature range, while avoiding computationally expensive DFT-MD calculations. The resultant gas potentials were validated against DFT trapping energies and are suitable for simulating combinations of Xe and Kr in solid solutions of CeO2, ThO2, UO2 and PuO2, providing a powerful tool for the atomistic simulation of conventional nuclear reactor fuel UO2 as well as advanced MOX fuels.

  16. CeOHCO3和CeO2束状纳米结构的制备及表征%Preparation and Characterization of Crystalline CeOHCO3 and CeO2 with Bundle-like Nanostructures

    Institute of Scientific and Technical Information of China (English)

    张晓娟; 张胜义; 田玉鹏; 金葆康; 吴杰颖

    2008-01-01

    The cantaloupe-like particles of CeOHCO3 were synthesized in aqueous solution by using cetyhrimethylammonium bromide (CTAB) as soft template. Then, the bunchiness rods of CeO2 were obtained by calcining CeOHCO3 at 450 ℃. The results of thermogravimetric/differential thermal analysis reveal that an endothermic reaction with decomposition is involved in the transformation process from CeOHCO3 to CeO2. By scanning electron microscopy and X-ray diffraction analysis, it is found that the orthorhombic phase CeOHCO3 particles are constituted of short nanorods with diameters ranging from several tens nm to over 100 nm, and the cubic phase CeO2 rods are composed of small particles with diameter ca. 15 nm. From the results of UV-Vis absorption and photoluminescence analysis, it is found that the CeO2 possess abundant defects, and the band gaps of the CeO2 and CeOHCO3 are ca. 2.70 eV and 3.87 eV, respectively.

  17. Development of a single-run analytical method for the detection of ten multiclass emerging contaminants in agricultural soil using an acetate-buffered QuEChERS method coupled with LC-MS/MS.

    Science.gov (United States)

    Lee, Young-Jun; Choi, Jeong-Heui; Abd El-Aty, A M; Chung, Hyung Suk; Lee, Han Sol; Kim, Sung-Woo; Rahman, Md Musfiqur; Park, Byung-Jun; Kim, Jang-Eok; Shin, Ho-Chul; Shim, Jae-Han

    2017-01-01

    This study was undertaken to develop and validate a single multiresidue method for the monitoring of ten multiclass emerging contaminants, viz. ceftiofur, clopidol, florfenicol, monensin, salinomycin, sulfamethazine, sulfathiazole, sulfamethoxazole, tiamulin, and tylosin in agricultural soil. Samples were extracted using an acetate-buffered, modified quick, easy, cheap, effective, rugged, and safe method followed by liquid chromatography with tandem mass spectrometric analysis in positive ion mode. Separation on an Eclipse Plus C18 column was conducted in gradient elution mode using a mobile phase of methanol (A) and distilled water (B), each containing 0.1% formic acid and 5 mM ammonium formate. The linearity of the matrix-matched calibrations, expressed as determination coefficients, was good, with R(2) ≥ 0.9908. The limits of quantification were in the range 0.05-10 μg/kg. Blank soil samples spiked with 4 × and 20 × the limit of quantification provided recovery rates of 60.2-120.3% (except sulfamethoxazole spiked at 4 × the limit of quantification, which gave 131.9%) with a relative standard deviation < 13% (except clopidol spiked at 20 × the limit of quantification, which gave 25.2%). This method was successfully applied to the monitoring of 51 field-incurred agricultural loamy-sand soil samples collected from 17 provincial areas throughout the Korean Peninsula. The detected and quantified drugs were clopidol (≤ 4.8 μg/kg), sulfathiazole (≤ 7.7 μg/kg), sulfamethazine (≤ 6.6 μg/kg), tiamulin (≤ 10.0 μg/kg), and tylosin (≤ 5.3 μg/kg). The developed method is simple and versatile, and can be used to monitor various classes of veterinary drugs in soil.

  18. Study on methylene blue photodegradation using CeO2 nanoparticle as catalysts%纳米CeO2粒子光催化降解亚甲基蓝的研究

    Institute of Scientific and Technical Information of China (English)

    田志茗; 勾金玲; 黄伟

    2016-01-01

    CeO2 nanoparticles were prepared by a simple precipitation method and calcinated at 600 ℃. CeO2 nanoparticles were characterized by thermogravimetric analysis, Fourier transform infrared spectroscopy (FT- IR), X- ray diffraction (XRD), N2 adsorption- desorption, scanning electron microscopy (SEM). The photodeg⁃radation of methylene blue catalyzed by CeO2 nanoparticles was studied under UV and sunlight irradiation. The optimum reaction conditions of photodegradation were that the initial concentration of methylene blue was 5.0 mg/L, the initial pH=11, the dosage of CeO2 nanoparticles catalyst calcinated at 600℃was 1.0 g/L. The remov⁃al rate of methylene blue was 87.05% within 60 min under UV irradiation of 300 W. The results indicated that the photodegradation of methylene blue catalyzed by CeO2 fol owed a pseudo first order kinetics. The photoca⁃talysis reactions fit the heterogeneous catalytic kinetic equation Langmuir- Hinshelwood kinetic model. In this case the rate constant for the surface reaction k was 0.138 5 mg/(L·min) and the adsorption equilibrium con⁃stant Kdye was 0.399 7 L/mg.%采用共沉淀法并在600℃焙烧制备纳米CeO2光催化剂,利用热重分析、傅立叶变换红外光谱(FT-IR)、X射线衍射(XRD)、N2吸附-脱附、扫描电子显微镜(SEM)等方法对纳米CeO2粒子进行了表征,并研究了纳米CeO2粒子催化剂对亚甲基蓝溶液的光催化降解行为。结果表明,在300 W汞灯照射下,对于初始质量浓度为5.0 mg/L和初始pH=11的亚甲基蓝溶液,加入600℃煅烧的纳米CeO21.0 g/L,反应60 min,亚甲基蓝降解率可达87.05%。该光催化降解反应表现为一级动力学反应,反应速率服从多相催化动力学方程Langmuir-Hinshelwood方程,光催化剂表面反应速率常数k为0.1385 mg/(L·min),吸附平衡常数Kdye为0.3997 L/mg。

  19. Fabrication of 5 cm long epitaxial Sm{sub 0.2}Ce{sub 0.8}O{sub 1.9-x} single buffer layer on textured Ni-5%W substrate for YBCO coated conductors via dip-coating PACSD method

    Energy Technology Data Exchange (ETDEWEB)

    Lei, M.; Wang, W.T.; Pu, M.H.; Yang, X.S.; He, L.J. [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Cheng, C.H. [Science and Engineering, University of New South Wales, Sydney 2052, New South Wales (Australia); Zhao, Y., E-mail: yzhao@home.swjtu.edu.cn [Key Laboratory of Magnetic Levitation and Maglev Trains (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)] [Science and Engineering, University of New South Wales, Sydney 2052, New South Wales (Australia)

    2011-11-15

    Epitaxial Sm{sub 0.2}Ce{sub 0.8}O{sub 1.9-x} single buffer layer for YBCO coated conductors was deposited via fluorine-free dip-coating CSD. Flat, dense and crack-free SCO films with sharp (2 0 0) c-axis texture were obtained by carefully controlling the processing. YBCO thin films with a homogeneous surface microstructure were deposited on the SCO-buffered NiW substrate via CSD approach. Five centimeters long epitaxial Sm{sub 0.2}Ce{sub 0.8}O{sub 1.9-x} (SCO) single buffer layer for YBCO coated conductors was deposited via dip-coating polymer-assisted chemical solution deposition (PACSD) approach on bi-axially textured Ni-5%W (2 0 0) alloy substrate. The film formation and texture evolution were investigated using X-ray diffraction and scanning electron microscopy. Flat, dense and crack-free SCO films with sharp (2 0 0) c-axis texture were obtained by way of carefully controlling the concentration of precursor solution, withdrawing speed, annealing temperature and dwelling time. On consideration of both microstructure and texture, epitaxial SCO single buffer layers were fabricated using precursor solution of 0.3 M cationic concentration, the withdrawing speed of 10 mm/min and heat treatment at 1100 deg. C in Ar-5%H{sub 2} mixture gas for 0.5 h. Epitaxial YBCO thin films with a homogeneous surface microstructure were deposited on the SCO-buffered NiW substrate via dip-coating PACSD approach. The PACSD approach was a promising way to fabricate long and low-cost YBCO coated conductors.

  20. Buffer capacity of biologics--from buffer salts to buffering by antibodies.

    Science.gov (United States)

    Karow, Anne R; Bahrenburg, Sven; Garidel, Patrick

    2013-01-01

    Controlling pH is essential for a variety of biopharmaceutical process steps. The chemical stability of biologics such as monoclonal antibodies is pH-dependent and slightly acidic conditions are favorable for stability in a number of cases. Since control of pH is widely provided by added buffer salts, the current study summarizes the buffer characteristics of acetate, citrate, histidine, succinate, and phosphate buffers. Experimentally derived values largely coincide with values calculated from a model that had been proposed in 1922 by van Slyke. As high concentrated protein formulations become more and more prevalent for biologics, the self-buffering potential of proteins becomes of relevance. The current study provides information on buffer characteristics for pH ranges down to 4.0 and up to 8.0 and shows that a monoclonal antibody at 50 mg/mL exhibits similar buffer capacity as 6 mM citrate or 14 mM histidine (pH 5.0-6.0). Buffer capacity of antibody solutions scales linearly with protein concentration up to more than 200 mg/mL. At a protein concentration of 220 mg/mL, the buffer capacity resembles the buffer capacity of 30 mM citrate or 50 mM histidine (pH 5.0-6.0). The buffer capacity of monoclonal antibodies is practically identical at the process relevant temperatures 5, 25, and 40°C. Changes in ionic strength of ΔI=0.15, in contrast, can alter the buffer capacity up to 35%. In conclusion, due to efficient self-buffering by antibodies in the pH range of favored chemical stability, conventional buffer excipients could be dispensable for pH stabilization of high concentrated protein solutions.

  1. Mechanisms of buffer therapy resistance.

    Science.gov (United States)

    Bailey, Kate M; Wojtkowiak, Jonathan W; Cornnell, Heather H; Ribeiro, Maria C; Balagurunathan, Yoganand; Hashim, Arig Ibrahim; Gillies, Robert J

    2014-04-01

    Many studies have shown that the acidity of solid tumors contributes to local invasion and metastasis. Oral pH buffers can specifically neutralize the acidic pH of tumors and reduce the incidence of local invasion and metastatic formation in multiple murine models. However, this effect is not universal as we have previously observed that metastasis is not inhibited by buffers in some tumor models, regardless of buffer used. B16-F10 (murine melanoma), LL/2 (murine lung) and HCT116 (human colon) tumors are resistant to treatment with lysine buffer therapy, whereas metastasis is potently inhibited by lysine buffers in MDA-MB-231 (human breast) and PC3M (human prostate) tumors. In the current work, we confirmed that sensitive cells utilized a pH-dependent mechanism for successful metastasis supported by a highly glycolytic phenotype that acidifies the local tumor microenvironment resulting in morphological changes. In contrast, buffer-resistant cell lines exhibited a pH-independent metastatic mechanism involving constitutive secretion of matrix degrading proteases without elevated glycolysis. These results have identified two distinct mechanisms of experimental metastasis, one of which is pH-dependent (buffer therapy sensitive cells) and one which is pH-independent (buffer therapy resistant cells). Further characterization of these models has potential for therapeutic benefit.

  2. Effect of Testing Media on Proton Conductivity of SPEEK Membranes Modified with Nanometer CeO2%测试介质对纳米CeO2改性SPEEK膜质子电导率的影响

    Institute of Scientific and Technical Information of China (English)

    童菊英; 郭强; 赵正平; 董云凤; 李丹; 李夏

    2011-01-01

    The membranes of sulfonated polyether ether ketone(SPEEK) with the degree of sulfonation ( DS) of 48. 3% , doped with nanometer cerium oxide ( CeO2) were prepared for direct methanol fuel cell application by solution casting technique. The proton conductivity of SPEEK/CeO2 composite membranes increased with the increasing of temperature and the contrary regular pattern occurred under the two testing media compared with pure SPEEK membrane. The conductivity of SPEEK/CeO2 composite membrane was IS times higher than that of pure SPEEK membrane in testing medium with 1 mol/L hydrochloric acid as the electrolyte, but reduced to about 40% in the water vapour. Fourier transform infrared (FOR) spectroscopy revealed a certain coordination existing between oxygen atom in -SO3H groups and cerium atom in the CeO2. X-ray diffraction(XRD) results demonstrate that, whether the SPEEK/CeO2 composite membrane or the composite membrane immersed with 1 mol/L hydrochloric acid for 4 h, the crystal structure of CeO2 in SPEEK/CeO2 composite membrane has no obvious change, which indicates that the coordination exists only in two solid-phase interfaces. Scanning electron microscopy (SEM) shows that modified/unmodified membranes has no net structure or microphase separation. Therefore, the proton can be transported through jumping between -SO3H groups in membranes. Acid solution is more advantageous to proton jumping between -SO3H groups in membranes than water vapour.%采用纳米氧化铈( CeO2)改性磺化度48.3%的磺化聚醚醚酮(SPEEK),通过溶液浇铸法制备用于直接甲醇燃料电池的质子交换膜.在两种介质中测试改性膜的电导率均随温度的升高而增大,与未改性膜相比却大小正好相反:在l mol/L以盐酸溶液为电解液的测试介质中,改性膜的电导率是未改性膜的15倍,在水蒸气测试介质中,却仅为40%.红外光谱分析表明,CeO2中的铈原子与-SO3H基团中的氧原子发生配位作用.X射线衍射仪(XRD)分析可见,当复合膜浸入l mol/L盐酸4h前后,纳米CeO2的晶体结构未见明显变化,表明所发生的配位作用仅处于CeO2和SPEEK两个固相界面上.扫描电子显微镜(SEM)观察改性膜和未改性膜均无网络结构和微相分离,质子在膜内通过-SO3H基团之间的跃迁传导,酸溶液介质远比水蒸气有利于质子在纳米CeO2改性SPEEK膜内磺酸基团之间的跃迁.

  3. Catalytic ethanolysis and gasification of kraft lignin into aromatic alcohols and H2-rich gas over Rh supported on La2O3/CeO2-ZrO2.

    Science.gov (United States)

    Yang, Jing; Zhao, Liang; Liu, Chunze; Wang, Yuanyuan; Dai, Liyi

    2016-10-01

    Efficient catalytic ethanolysis and gasification of kraft lignin were conducted over a versatile supported catalyst Rh/La2O3/CeO2-ZrO2 to give high-value aromatic alcohols and H2-rich gas. The removal of phenolic hydroxyl group was the most prevalent reaction, and importantly, almost no phenols, undesired char and saturating the aromatic ring were detected. Meanwhile, the feedstock and solvent both played key roles in H2 generation that contributed to the hydrodeoxygenation of liquid components and made the whole catalytic process out of H2 supply. Reusability tests of catalyst indicated that the crystalline phase transition and agglomeration of support, the loss of noble metal Rh and carbon deposition were the possible reasons for its deactivation in supercritical ethanol. Comparing with water, methanol and isopropanol system, ethanol was the only effective solvent for the depolymerization process.

  4. Preparation of CeO2/CaAl-LDHs/AC and its environmental applications%二氧化铈/钙铝水滑石/活性炭的制备及环境应用

    Institute of Scientific and Technical Information of China (English)

    谢非; 李静; 晋冠平

    2016-01-01

    Ce-doped CaAl/layered double hydroxide was coated at activated carbon(CeO2/CaAl- LDHs/AC) byco-precipitation method with the aid of ultrasound. The products was characterized by field emission scanning electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. Flower-like layer structure CeO2/CaAl-LDHs was well distributed on the surface of active carbon with good thermostability. The adsorption of Cr(Ⅵ),Pb(Ⅱ),fluoride and malachite green by CeO2/CaAl-LDHs/AC were investigated respectively in aqueous solution. All the adsorption processes agree with the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of Cr(Ⅵ),Pb(II), fluoride and malachite green are 83.06mg/g,131.58mg/g,61.20mg/g and 420.17mg/g at pH=7.0,45℃ and 2h,respectively.%采用超声辅助共沉淀法,制备了二氧化铈/钙铝水滑石/活性炭复合材料(CeO2/CaAl-LDHs/AC)。通过场发射扫描电子显微镜、X 射线衍射、X 射线光电子能谱、傅里叶变换红外光谱和热重分析技术,对CeO2/CaAl-LDHs/AC 的形貌、组成和结构进行了表征。结果发现:花样片层状的 CeO2/CaAl-LDHs 材料均匀地分布在活性炭上。考察了CeO2/CaAl-LDHs/AC对水溶液中铬(Ⅵ)、铅(Ⅱ)、氟和孔雀绿的吸附性能。此类污染物的吸附过程均符合准二阶动力学模型和 Langmuir 等温模型;在 pH=7、45℃和吸附时间2h 条件下, CeO2/CaAl-LDHs/AC 可成功用于铬(Ⅵ)、铅(Ⅱ)、氟和孔雀绿的吸附去除,最大吸附量分别为83.06mg/g、131.58mg/g、61.20mg/g和420.17mg/g。

  5. CeO2-ZrO2-La2O3-Al2O3 composite oxide and its supported palladium catalyst for the treatment of exhaust of natural gas engined vehicles

    Institute of Scientific and Technical Information of China (English)

    Xiaoyu Zhang; Enyan Long; Yile Li; Jiaxiu Guo; Lijuan Zhang; Maochu Gong; Minghua Wang; Yaoqiang Chen

    2009-01-01

    Composite supports CeO2-ZrO2-Al2O3 (CZA) and CeO2-ZrO2-Al2O3-La2O3 (CZALa) were prepared by co-precipitation method. Palladium catalysts were prepared by impregnation and their purification ability for CH4, CO and NOx in the mixture gas simulated the exhaust from natural gas vehicles (NGVs) operated under stoichiometric condition was investigated. The effect of La2O3 on the physicochemical properties of supports and catalysts was characterized by various techniques. The characterizations with X-ray diffraction (XRD) and Raman spectroscopy revealed that the doping of La2O3 restrained effectively the sintering of crystallite particles, maintained the crystallite particles in nanoscale and stabilized the crystal phase after calcination at 1000 ℃. The results of N2-adsorption, H2-temperature-programmed reduction (H2-TPR) and oxygen storage capacity (OSC) measurements indicated that La2O3 improved the textural properties, reducibility and OSC of composite supports. Activity testing results showed that the catalysts exhibit excellent activities for the simultaneous removal of methane, CO and NOx in the simulated exhaust gas. The catalysts supported on CZALa showed remarkable thermal stability and catalytic activity for the three pollutants, especially for NOx. The prepared palladium catalysts have high ability to remove NOx, CH4 and CO, and they can be used as excellent catalysts for the purification of exhaust from NGVs operated under stoichiometric condition. The catalysts reported in this work also have significant potential in industrial application because of their high performance and low cost.

  6. Investigation of active-buffer pulse tube refrigerator

    Science.gov (United States)

    Zhu, Shaowei; Kakimi, Yasuhiro; Matsubara, Yoichi

    An active-buffer pulse tube refrigerator, which is a GM type pulse tube refrigerator, is described in this paper. Two or more buffers are connected at the hot end of the pulse tube through on/off valves. The main purpose of this method is to increase the efficiency. A numerical method is introduced to analyse the working process. To understand the basic mechanism, an ideal cycle is also introduced. With a prototype single stage active-buffer pulse tube refrigerator, a cooling capacity of 166 W and a percent Carnot of 13% at 80 K have been obtained.

  7. Electrodialysis operation with buffer solution

    Science.gov (United States)

    Hryn, John N.; Daniels, Edward J.; Krumdick, Greg K.

    2009-12-15

    A new method for improving the efficiency of electrodialysis (ED) cells and stacks, in particular those used in chemical synthesis. The process entails adding a buffer solution to the stack for subsequent depletion in the stack during electrolysis. The buffer solution is regenerated continuously after depletion. This buffer process serves to control the hydrogen ion or hydroxide ion concentration so as to protect the active sites of electrodialysis membranes. The process enables electrodialysis processing options for products that are sensitive to pH changes.

  8. Oxygen Enrichment Effect of CeO2 to the Cathode Performance of Proton Exchange Membrane Fuel Cell%CeO2的富氧性能对质子交换膜燃料电池阴极的影响

    Institute of Scientific and Technical Information of China (English)

    侯向理; 徐洪峰; 董建华; 孙昕

    2006-01-01

    应用溶胶法和浸渍法向质子交换膜燃料电池阴极Pt/C催化剂添加CeO2,透射电子显微镜(TEM)分析和循环伏安测试表明:对由上述两种方法制备的各含5%CeO2的Pt/C催化剂,其粒径、形态分布以及CeO2在催化剂表面的覆盖度都不相同.单电池测试结果发现,二氧化铈的富氧作用表现明显,在以溶胶法制得的CeO2-Pt/C催化剂中,3% CeO2含量的催化剂呈现最佳的性能,而由浸渍法制得的CeO2-Pt/C,则以1%CeO2含量的性能最好,但对比之下,不如溶胶法制备的含3% CeO2的催化剂.

  9. Programmable pH buffers

    Science.gov (United States)

    Gough, Dara Van; Huber, Dale L.; Bunker, Bruce C.; Roberts, Mark E.

    2017-01-24

    A programmable pH buffer comprises a copolymer that changes pK.sub.a at a lower critical solution temperature (LCST) in water. The copolymer comprises a thermally programmable polymer that undergoes a hydrophobic-to-hydrophilic phase change at the LCST and an electrolytic polymer that exhibits acid-base properties that are responsive to the phase change. The programmable pH buffer can be used to sequester CO.sub.2 into water.

  10. k(+)-buffer: An Efficient, Memory-Friendly and Dynamic k-buffer Framework.

    Science.gov (United States)

    Vasilakis, Andreas-Alexandros; Papaioannou, Georgios; Fudos, Ioannis

    2015-06-01

    Depth-sorted fragment determination is fundamental for a host of image-based techniques which simulates complex rendering effects. It is also a challenging task in terms of time and space required when rasterizing scenes with high depth complexity. When low graphics memory requirements are of utmost importance, k-buffer can objectively be considered as the most preferred framework which advantageously ensures the correct depth order on a subset of all generated fragments. Although various alternatives have been introduced to partially or completely alleviate the noticeable quality artifacts produced by the initial k-buffer algorithm in the expense of memory increase or performance downgrade, appropriate tools to automatically and dynamically compute the most suitable value of k are still missing. To this end, we introduce k(+)-buffer, a fast framework that accurately simulates the behavior of k-buffer in a single rendering pass. Two memory-bounded data structures: (i) the max-array and (ii) the max-heap are developed on the GPU to concurrently maintain the k-foremost fragments per pixel by exploring pixel synchronization and fragment culling. Memory-friendly strategies are further introduced to dynamically (a) lessen the wasteful memory allocation of individual pixels with low depth complexity frequencies, (b) minimize the allocated size of k-buffer according to different application goals and hardware limitations via a straightforward depth histogram analysis and (c) manage local GPU cache with a fixed-memory depth-sorting mechanism. Finally, an extensive experimental evaluation is provided demonstrating the advantages of our work over all prior k-buffer variants in terms of memory usage, performance cost and image quality.

  11. Buffer gas acquisition and storage

    Science.gov (United States)

    Parrish, Clyde F.; Lueck, Dale E.; Jennings, Paul A.

    2001-02-01

    The acquisition and storage of buffer gases (primarily argon and nitrogen) from the Mars atmosphere provides a valuable resource for blanketing and pressurizing fuel tanks and as a buffer gas for breathing air for manned missions. During the acquisition of carbon dioxide (CO2), whether by sorption bed or cryo-freezer, the accompanying buffer gases build up in the carbon dioxide acquisition system, reduce the flow of CO2 to the bed, and lower system efficiency. It is this build up of buffer gases that provide a convenient source, which must be removed, for efficient capture of CO2. Removal of this buffer gas barrier greatly improves the charging rate of the CO2 acquisition bed and, thereby, maintains the fuel production rates required for a successful mission. Consequently, the acquisition, purification, and storage of these buffer gases are important goals of ISRU plans. Purity of the buffer gases is a concern e.g., if the CO2 freezer operates at 140 K, the composition of the inert gas would be approximately 21 percent CO2, 50 percent nitrogen, and 29 percent argon. Although there are several approaches that could be used, this effort focused on a hollow-fiber membrane (HFM) separation method. This study measured the permeation rates of CO2, nitrogen (N2), and argon (Ar) through a multiple-membrane system and the individual membranes from room temperature to 193 K and 10 kPa to 300 kPa. Concentrations were measured with a gas chromatograph. The end result was data necessary to design a system that could separate CO2, N2, and Ar. .

  12. Buffer Gas Acquisition and Storage

    Science.gov (United States)

    Parrish, Clyde F.; Lueck, Dale E.; Jennings, Paul A.; Callahan, Richard A.; Delgado, H. (Technical Monitor)

    2001-01-01

    The acquisition and storage of buffer gases (primarily argon and nitrogen) from the Mars atmosphere provides a valuable resource for blanketing and pressurizing fuel tanks and as a buffer gas for breathing air for manned missions. During the acquisition of carbon dioxide (CO2), whether by sorption bed or cryo-freezer, the accompanying buffer gases build up in the carbon dioxide acquisition system, reduce the flow of CO2 to the bed, and lower system efficiency. It is this build up of buffer gases that provide a convenient source, which must be removed, for efficient capture Of CO2 Removal of this buffer gas barrier greatly improves the charging rate of the CO2 acquisition bed and, thereby, maintains the fuel production rates required for a successful mission. Consequently, the acquisition, purification, and storage of these buffer gases are important goals of ISRU plans. Purity of the buffer gases is a concern e.g., if the CO, freezer operates at 140 K, the composition of the inert gas would be approximately 21 percent CO2, 50 percent nitrogen, and 29 percent argon. Although there are several approaches that could be used, this effort focused on a hollow-fiber membrane (HFM) separation method. This study measured the permeation rates of CO2, nitrogen (ND, and argon (Ar) through a multiple-membrane system and the individual membranes from room temperature to 193K and 10 kpa to 300 kPa. Concentrations were measured with a gas chromatograph that used a thermoconductivity (TCD) detector with helium (He) as the carrier gas. The general trend as the temperature was lowered was for the membranes to become more selective, In addition, the relative permeation rates between the three gases changed with temperature. The end result was to provide design parameters that could be used to separate CO2 from N2 and Ar.

  13. A Popularity-Aware Buffer Management System to Stored Packet Memory in Massage Transmission Grade in Delay Tolerant Network

    Directory of Open Access Journals (Sweden)

    Jagruti Ramabhai Patel ,

    2014-02-01

    Full Text Available A delay-tolerant network is a network designed so that momentary or flashing communication problems and limitations have the least possible unpleasant impact. As the storage-carry-forward paradigm is adopted to transfer messages in DTNs, buffer management schemes greatly influence the performance of routing protocols when nodes have limited buffer space. Two major issues should be considered to achieve data delivery in such challenging networking environments: a routing strategy for the network and a buffer management policy for each node in the network. The routing strategy determines which messages should be forwarded when nodes meet and the buffer management policy determines which message is purged when the buffer overflows in a node. This study proposes an enhanced buffer management policy that utilizes message properties. For maximization of the message deliveries and minimization of the average delay, two utility functions are proposed on the basis of message properties, particularly the number of replicas, the age and the remaining time-to-live(TTL. Simulation results show that our buffer management scheme canimprove delivery ratio and has relative lower overhead ratio compared with other buffer management schemes. In this scheme several type of buffered policies, null buffered , single copy buffered ,infinite buffered etc. Our work in null buffered policies there are no massage are available in buffered after massage send. In case massage send and this massage are discarded and buffered store only single copy of massage than retransmitted it.

  14. New pH-buffering system for media utilized during gamete and embryo manipulations for assisted reproduction.

    Science.gov (United States)

    Swain, Jason E; Pool, Thomas B

    2009-06-01

    Maintenance of stable pH is important for optimizing gamete and embryo culture. One method to stabilize pH entails using zwitterionic buffers in IVF handling media used outside the laboratory incubator. Current handling media utilize single buffers, such as MOPS or HEPES. However, the use of a single buffer limits the ability to adjust the range of buffering capacity. Furthermore, changes in temperature alter buffering of these compounds. Therefore, traditional IVF handling media utilizing a single buffer may not provide ideal pH buffering. This study reports that combining multiple buffers, such as HEPES, MOPS and DIPSO, into a single medium in various ratios gives the ability to shift the effective buffering range to cover a specific pH. Additionally, by combining various buffers, it is possible to expand pH buffering over a range of temperatures, while simultaneously reducing the absolute concentration of individual buffers, thereby reducing or alleviating toxicity concerns. This report verifies that DIPSO, MOPS and HEPES, and their combinations, support embryo development. Therefore, utilization of bi- and tri-buffered media, containing a mixture of HEPES, MOPS or DIPSO, offers advantages compared with media containing HEPES or MOPS alone, and may be used for procedures such as oocyte retrieval, intracytoplasmic sperm injection, embryo transfer and cryopreservation.

  15. An investigation of the effects of CeO2 crystal planes on the aerobic oxidative synthesis of imines from alcohols and amines%纳米二氧化铈催化制备亚胺

    Institute of Scientific and Technical Information of China (English)

    张志鑫; 王业红; 王敏; 吕建民; 李利花; 张哲; 李名润; 蒋景阳; 王峰

    2015-01-01

    近年来,金属氧化物的晶面效应及其独特的催化性能引起研究者的广泛关注.其中,二氧化铈(CeO2)因具有储放氧性质、易于形成氧空位等特点,在诸多领域得到应用,尤其是作为催化剂,可用作活性相、载体、复合催化材料等. CeO2的晶面效应主要由于晶面上氧空位的性质引起的.目前,这方面的研究主要集中在高温条件下氧空位的动态转化过程,如水汽变换反应、有机物脱除等.但是高温下CeO2中氧空位的活泼性,增加了晶面效应的复杂性.因此,利用低温液相有机反应作为探针,研究晶面效应是一种可靠的解决方案.我们近些年的工作研究了CeO2不同晶面上的酸性及催化水解性能,在本研究中,我们提出在温和条件下, ;采用有机探针反应,研究不同晶面的氧化还原性质.亚胺类化合物作为一类重要的含氮有机中间体,在生物、农药、医药等领域中具有重要应用.传统的亚胺合成方法是将醛类化合物或酮类化合物与胺类在酸催化剂的作用下直接缩合.近年来出现了新的亚胺合成方法,例如通过胺类氧化脱氢、炔烃的氢胺化、醇胺脱氢/氧化偶联等,其中醇胺脱氢/氧化偶联的方法因具有原料廉价易得、过程清洁等优点,而成为研究热点.最近, Masazumi Tamura等研究发现CeO2能够在温和条件下高效催化醇胺氧化偶联制亚胺,通过一系列表征发现CeO2的高活性主要由于其氧空位中存在丰富的活性氧物种.然而, CeO2的晶面效应及其在此反应中的催化性能,以及不同晶面上的氧化还原性质还有待进一步的研究.本文研究了CeO2的晶面效应及其在醇胺氧化偶联制亚胺反应中的催化性能.在温和的反应条件下(60 oC), CeO2能够高效催化苯甲醇与苯胺反应制备亚胺,并且对底物具有很好的普适性,在催化一系列醇与胺氧化偶联制亚胺的反应中,对于大部分底物,醇类化合物的转化率可达89%以上,亚胺类化合物的选择性可达90%以上.通过水热合成法分别制备了棒状CeO2、立方体CeO2和八面体CeO2,并通过X射线衍射、透射电子显微镜和高分辨透射电子显微镜确证了其结构和形貌,结果表明三种形貌的CeO2均为纯相的CeO2,其中棒状CeO2暴露(110)和(100)晶面,立方体CeO2暴露(100)晶面,八面体CeO2暴露(111)晶面.并以苯甲醇氧化反应和苯甲醇与苯胺反应为探针研究了其催化性能.结果发现:不同形貌的CeO2具有显著不同的催化活性,其中棒状CeO2表现出最优异的催化性能,立方体CeO2和八面体CeO2次之.通过Raman光谱表征了不同形貌CeO2的氧空位性质并比较了它们的氧空位浓度.结果发现:棒状CeO2的氧空位浓度相对值(A595/A462)为0.077,高于立方体CeO2和八面体CeO2.通过比较分析计算可知,在CeO2(110),(100)和(111)三种晶面中,(110)晶面因其具有最多的氧空位而表现出最高的催化活性和优异的氧化还原性质,(110)晶面上亚胺的生成速率为4.618 mmol/(g·h),分别为(100)晶面和(111)晶面上的32倍和49倍.该研究有助于提高认识CeO2基催化材料的低温氧化还原性质.%We herein report the effects of CeO2 crystal planes on the oxidative coupling of alcohols and amines to form imines. CeO2 exhibits significant catalytic activity under mild reaction conditions (60 °C) during the synthesis of 13 different imines, giving>89%conversions and>90%selectivities. The crystal planes of CeO2 greatly affect the catalytic performance. Among the crystal planes investigat-ed (the (110), (100) and (111) planes), the (110) plane shows the strongest redox ability and thus the best catalytic activity, generating a 97%yield of the imine at 60 °C in 2 h, because it contains the highest concentration of oxygen vacancies.

  16. Development of a Single Ion Pair HPLC Method for Analysis of Terbinafine, Ofloxacin, Ornidazole, Clobetasol, and Two Preservatives in a Cream Formulation: Application to In Vitro Drug Release in Topical Simulated Media-Phosphate Buffer Through Rat Skin.

    Science.gov (United States)

    Dewani, Anil P; Bakal, Ravindra L; Kokate, Pranjali G; Chandewar, Anil V; Patra, Srdhanjali

    2015-01-01

    Present work reports an HPLC method with UV detection for quantification of terbinafine, ofloxacin, ornidazole, and clobetasol in a cream formulation along with two preservatives methyl and propyl paraben. The chromatographic separation and quantification was achieved by an octyl bonded column and a gradient elution program involving an ion-pairing reagent, hexanesulfonic acid (0.2%, pH modified to 2.7 using orthophosphoric acid) and acetonitrile. The method was simple and devoid of buffer salts and therefore advantageous for system and column life. The three step gradient program was initiated with 30% (v/v) acetonitrile for the first 5 min and ramped linearly to 60% in the next 7 min. The mobile phase remained constant for the next 11 min and then concluded at 30% (v/v) of acetonitrile. Flow rate throughout was 0.8 mL/min, and all the signals were monitored at 243 nm. The method was applied for assay of a cream formulation and its in vitro permeation studies to determine the penetration profile of the four drugs and two preservatives. A marketed cream formulation was selected for the permeation study, which was carried out using a diffusion cell consisting of topical simulated media, phosphate buffer (pH=6.8) solution containing 1% sodium lauryl sulfate as a receiver medium.

  17. Thermophysical tests of buffer materials

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, H. [ITC, Tokyo (Japan); Taniguchi, Wataru

    1999-03-01

    Thermodynamic properties of buffer materials were measured for putting in order thermodynamic constants to be used in the near-field thermal analysis. The thermal diffusivity and thermal conductivity were measured as functions of the water content and temperature to deduce the specific heat. The thermal conductivity and specific heat varied significantly as the water content changed. Obtained values of the specific heat agreed well the expected values calculated based on the constituents of the buffer material. Temperature dependence of the thermodynamic constants was found small below 90degC. From the findings, the thermal conductivity and specific heat of the buffer material were formulated as functions of the water content. Thermodynamic study of powdery bentonite was carried out as well with a purpose of use for filling apertures in the artificial barrier. (H. Baba)

  18. ACETIC ACID AND A BUFFER

    DEFF Research Database (Denmark)

    2009-01-01

    The present invention relates to a composition comprising : a) 0.01-20% wt/wt acetic acid and b) a physiologically tolerable buffer capable of maintaining acetic acid at a pH in the range of 2-7; and use of such a composition as an antimicrobial agent.......The present invention relates to a composition comprising : a) 0.01-20% wt/wt acetic acid and b) a physiologically tolerable buffer capable of maintaining acetic acid at a pH in the range of 2-7; and use of such a composition as an antimicrobial agent....

  19. A Capital Adequacy Buffer Model

    NARCIS (Netherlands)

    D.E. Allen (David); M.J. McAleer (Michael); R.J. Powell (Robert); A.K. Singh (Abhay)

    2013-01-01

    markdownabstract__Abstract__ In this paper, we develop a new capital adequacy buffer model (CABM) which is sensitive to dynamic economic circumstances. The model, which measures additional bank capital required to compensate for fluctuating credit risk, is a novel combination of the Merton structur

  20. Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports

    Directory of Open Access Journals (Sweden)

    Bernay Cifuentes

    2015-11-01

    Full Text Available CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51 at a gaseous space velocity of 70,600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2, which showed the best performance in the stability test, also produced the highest H2 yield above 600 °C, followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM, XPS, and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions, as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.