Sample records for ceo2 single buffer

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


    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. Biaxially aligned YSZ and CeO2 buffer layers on hastelloy prepared by magnetron IBAD

    Full text: The development of high-current, flexible superconducting YBCO tapes is based on a metal substrates overcoated with a biaxially aligned oxide buffer layer to serve as a template for the epitaxial growth of c-axis oriented Yba2Cu3O7 thin films. A secondary function of the buffer is to act as a diffusion barrier to metal species to prevent them from poisoning the superconducting film. Widely studied oxide buffer layers include yttria-stabilised zirconia (YSZ) and cerium oxide (CeO2) produced by ion-beam-assisted deposition (IBAD). We have combined IBAD with magnetron sputtering to deposit biaxially aligned YSZ and CeO2 on Hastelloy C276 substrates held at room temperature. The ion beam is directed at 55deg to the normal of the film plane. In addition, we achieved room temperature epitaxial growth of CeO2 films on IBAD YSZ films by bias sputtering to form biaxially aligned CeO2/YSZ bilayers. The crystalline quality and inplane orientation of the films (200 nm thick) were investigated by x-ray diffraction techniques including ω and φ scans and pole figures. The IBAD YSZ and CeO2 films have a (111) pole in the ion beam direction with a full width at half maximum, FWHM = 24 - 30 deg; the CeO2/YSZ bilayer is similarly aligned with FWHM = 32 deg

  3. Effective thickness of CeO2 buffer layer for YBCO coated conductor by advanced TFA-MOD process

    YBCO films were fabricated on PLD-CeO2/IBAD-Gd2Zr2O7/Hastelloy substrates using the advanced TFA-MOD process. The effective thickness of the CeO2 buffer layer for obtaining high Ic was investigated in short samples of YBCO films. The CeO2 buffer layer was epitaxially grown on an IBAD-Gd2Zr2O7 template tape with 18 deg. of Δφ by a reel-to-reel PLD system. The in-plane grain alignment of PLD-CeO2 buffer layers rapidly improved with the thickness and saturated at a critical thickness of 0.8 μm. The size of CeO2 grains was about 1 μm at the saturated thickness of Δφ. YBCO films with the thickness of 1 μm were deposited by the TFA-MOD on the CeO2 buffer layer with different thickness films. Improvement of the CeO2 in-plane grain alignment resulted in increase of Ic. The Ic values of 250-290 A were obtained with the CeO2 layer thicker than 0.8 μm. The CeO2 thickness, at which the intensity ratio of the BaCeO3 was saturated, corresponded to the critical thickness. From the view points of achieving higher production rates and to obtain the CeO2 Δφ value of 5 deg. as well as considering the reaction between YBCO and CeO2, the optimum thickness of the CeO2 buffer layer on the IBAD-Gd2Zr2O7 with 18 deg. of Δφ was found to be at least 0.8 μm

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

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


    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 of...... small CeO2 nanoparticles resulted in the growth of CeO2 nanocrystals with an irregular truncated octahedral shape and pores extending along the 〈110〉 directions. Oxygen vacancies were found on the crystal surfaces and internal walls of the pores by scanning transmission electron microscopy and electron...... energy-loss spectroscopy. The oxygen vacancies might play an important role in oxygen diffusion in the crystals and the catalytic activities of single-crystalline porous CeO 2 structures. © 2011 American Chemical Society....

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


    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.

  6. Chemical approach to the deposition of textured CeO2 buffer layers based on sol gel dip coating

    The widespread use of vacuum techniques for the development of coated conductors, in which buffer and superconducting (REBa2Cu3O7-δ) layers are deposited epitaxially on a substrate, is well established in the research environment. However, obtaining uninterrupted deposition at high speed, increasing flexibility in composition and in film thickness and attaining independence of geometric constraints are areas in which many vacuum techniques will need sustained development in order to answer industrial demands. This work describes the deposition of textured CeO2 buffer layers based on sol gel dip coating under atmospheric environment and from aqueous precursor materials. Research has been performed towards the deposition of CeO2-buffer layers using the amorphous citrate method on sapphire substrates and Ni-W foils. Coating is performed using the dip-coating technique, which allows extension to a continuous system. The withdrawal speed and the thermal treatment have been optimised in order to obtain highly oriented (001) layers exhibiting a smooth and crack-free morphology both on ceramic and metallic substrates. From the results it was concluded that sintering atmosphere and sintering temperature play a crucial role in the growth mechanism. This study describes the structural and morphological analysis of the thin layer with special attention to the difference between ceramic and metallic substrates. (orig.)

  7. Deposition of CeO 2/YSZ buffer layer on Hastelloy substrates for MOD process of YBa 2Cu 3O 7- x film

    Fuji, Hiroshi; Honjo, Tetsuji; Nakamura, Yuichi; Izumi, Teruo; Takeshi, Araki; Hirabayashi, Izumi; Shiohara, Yuh; Iijima, Yasuhiro; Takeda, Kaoru


    Trifluoroacetate metalorganic deposition (TFA-MOD) process is expected as a low cost process for mass production of coated conductors because it is a non-vacuum process. In order to apply the technique to fabrication of coated conductors, suitable buffer layers have to be considered to achieve a high orientation of superconducting layer and prevention of the reaction with metal substrate. The combination of CeO 2 on IBAD-YSZ is considered as an effective buffer for TFA-MOD process expecting to satisfy a high acid resistivity and high crystal grain alignment. The CeO 2 buffer layer was deposited on IBAD-YSZ/Hastelloy substrates by RF magnetron sputtering. From XRD analysis, the CeO 2 buffer layer showed very good in-plane alignment on YSZ-IBAD buffer layer. In a holding time of 1 h, the suitable maximum heat treatment temperature was found to be from 750°C to 775°C for TFA-Y123 on metal substrate. The Jc- B property of Y123 on CeO 2/YSZ/Hastelloy shows the Jc values of 1.4 MA/cm 2 at 77.3 K, 0 T and more than 10 5 A/cm 2 at 77.3 K, 2 T. The high performance under high magnetic field was confirmed.

  8. Structural and electrical properties of SrTiO3 films grown on CeO2 buffered sapphire

    The physical properties of complex oxides like ferroelectric Perovskite are strongly connected with their composition, structure and structural imperfections. Lattice constants and thermal properties of substrate materials and deposited films are usually different. In the case of thin epitaxial films this difference can be used for engineering of properties of ferroelectric materials via mechanical strain due to changing of film thickness and preparation conditions. In the present work we report on results of measuring the strain of both in buffer CeO2 and STO films on r-cut sapphire. Ferroelectric films were deposited by PLD. Different types of strain lead to various structural modifications in films. The resulting type of distortion and defects are investigated by high-resolution X-ray analysis. Electrical properties of STO films of various thicknesses are measured using planar capacitors in a wide frequencies range. It is shown that in the thinner films the stress is compensated by misfit dislocations generated during growth and a deformation of the STO lattice. With increasing film thickness cracks develop in two crystalline directions, i.e. along the [1210] and, additionally, the [1010] directions of r-cut sapphire. The strained films show a strong modification of temperature dependence of the dielectric permittivity.

  9. An all chemical solution deposition approach for the growth of highly textured CeO2 cap layers on La2Zr2O7-buffered long lengths of biaxially textured Ni-W substrates for YBCO-coated conductors

    A reel-to-reel, dip coating process has been developed to continuously deposit epitaxial La2Zr2O7 (LZO) and CeO2 on 5 m long cube-textured {100} (001)Ni tapes. Recent results for La2Zr2O7 and CeO2 buffer layers deposited on long lengths of Ni substrate for the realization of YBa2Cu3O7-x (YBCO)-coated conductors are presented. The major achievement is the development of a new all chemical solution deposition (CSD) process leading to the formation of highly textured buffer layers at moderate annealing temperatures. Reproducible highly textured, dense and crack-free LZO buffer layers and CeO2 cap layers were obtained for annealing temperatures as low as 900 deg. C in a reducing atmosphere (Ar-5 at.%-H2). The thickness of the LZO buffer layers was determined to be (200 ± 10) nm per single coating; prepared cerium oxide layers showed a thickness of 60 nm ± 10 nm. Pulsed laser deposition (PLD) was used to grow YBCO films on these substrates. A Tc0 of T = 90.5 K and ΔTc = 1.4 K was obtained on PLD-YBCO/CSD-CeO2 /CSD-LZO/Ni-5 at.% W, which shows the outstanding features of this new buffer layer architecture processed by CSD. The large layer thickness combined with low annealing temperatures is the main advantage of this new process for low-cost buffer layer deposition on Ni-RABiTS (rolling-assisted biaxially textured substrates)

  10. Growth and Characterization of Doped CeO2 Buffers on Ni-W Substrates for Coated Conductors Using Metal Organic Deposition Method

    WANG Yao; ZHOU Lian; YU Zeming; LI Chengshan; LI Jinshan; JIN Lihu; LU Yafen


    CeO2 and Ce0 8Mo2O2-d films (M =Mn,Y,Gd,Sin,Nd and La) with (001) preferred orientation have been prepared on biaxially textured Ni-W substrates by metal organic decomposition (MOD) method.The factors influencing the formation of cracks on the surface of these CeO2 and doped CeO2 films on Ni-W substrates were explored by X-ray diffraction (XRD),scanning electron microscopy (SEM) analysis,atomic force microscopy (AFM) and differential scanning calorimetry (DSC).The results indicate that many factors,such as the change of the ionic radii of doping cations,the transformation of crystal structure and the formation of oxygen vacancies in lattices at high annealing temperature,may be related to the formation of cracks on the surface of these films.However,the crack formation shows no dependence on the crystal lattice mismatch degree of the films with Ni-W substrates.Moreover,the suppression of surface cracks is related to the change of intrinsic elasticity of CeO2 film with doping of cations with a larger radius.SEM and AFM investigations of Ce08Mo2O2-d(M =Y,Gd,Sm,Nd and La) films reveal the dense,smooth and crack-free microstructure,and their lattice parameters match well with that of YBCO,illuminating that they are potentially suitable to be as buffer layer,especially as cap layer in multi-layer architecture of buffer layer for coated conductors.

  11. TEM investigation of irradiation damage in single crystal CeO2

    In order to understand the evolution of radiation damage in oxide nuclear fuel, 150-1000 keV Kr ions were implanted into single crystal CeO2, as a simulation of fluorite ceramic UO2, while in situ transmission electron microscopy (TEM) observations were carried out. Two characteristic defect structures were investigated: dislocation/dislocation loops and nano-size gas bubbles. The growth behavior of defect clusters induced by 1 MeV Kr ions up to doses of 5 x 1015 ions/cm2 were followed at 600 deg. C and 800 deg. C. TEM micrographs clearly show the development of defect structures: nucleation of dislocation loops, transformation to extended dislocation lines, and the formation of tangled dislocation networks. The difference in dislocation growth rates at 600 deg. C and 800 deg. C revealed the important role which Ce-vacancies play in the loop formation process. Bubble formation, studied through 150 keV Kr implantations at room temperature and 600 deg. C, might be influenced by either the mobility of metal-vacancies correlated with at threshold temperature or the limitation of gas solubility as a function of temperature.

  12. Angular properties of pure and Ca-substituted YBa2Cu3O7-δ superconducting thin films grown on SrTiO3 and CeO2 buffered Al2O3 substrates

    In this work transport properties of superconducting 10 at.% Ca-substituted YBCO thin films grown on (1 0 0)-SrTiO3 single crystal substrate (STO) and superconducting pure and 10 at.% Ca-substituted YBCO thin films grown on CeO2 buffered Al2O3 substrates (CAO) have been analyzed as a function of the temperature, applied magnetic field and angle between magnetic field direction and the direction normal to the film surfaces. Particularly, the angular analysis provides an easy way to discriminate between isotropic point defects and correlated pinning sites. Despite the intragrain pinning mechanisms remained unaffected by Ca substitution, a detrimental effect on grain boundary properties clearly emerged for 10 at.% Ca concentration. This effect is enhanced in sample grown on CeO2 buffered sapphire where a more disturbed grain boundary is expected resulting in an enhancement of the correlated pinning, already observed in pure YBCO films grown on CAO, and in a reduction of the intrinsic pinning efficiency

  13. Influence of the Ion-to-Atom Ratio on the Structure of CeO2 Buffer Layer by Ion Beam Assisted E-Beam Evaporation

    Kim, Chang Su; Jo, Sung Jin; Kim, Woo Jin; Koo, Won Hoe; Baik, Hong Koo; Lee, Se Jong


    Using ion-beam assisted e-beam evaporation with the ion beam directed at 55° to the normal of the film plane, (200) oriented CeO2 films with biaxial texture were deposited on Hastelloy C276 substrates at room temperature. The crystalline quality and in-plane orientation of films was investigated by X-ray diffraction 2θ-scan and Φ-scan, atomic force microscopy (AFM). It was shown that the in-plane and out-of-plane textures of the CeO2 films were controlled by the deposition parameters. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO2 films have been successfully grown on Hastelloy C276.

  14. Chemical solution deposition (CSD) of CeO2 and La2Zr2O7 buffer layers on cube textured NiW substrates

    We present results of crack free layers of CeO2 and La2Zr2O7 deposited by means of CSD on cube textured Ni-4 at.% W substrates. EBSD-data show histograms with very good inplane- and out-of-plane textures and were used to simulate the critical current density in the YBCO layer. The surface roughness, a sensitive feature for good deposition results, was analyzed with a profilometer. In the CSD process we applied, the 2, 4-pentanedionates of the metal cations in glacial acetic acid and methanol served as starting substances

  15. Improved textured La2Zr2O7 buffer layers on bi-axially textured Ni–W substrates using CeO2 seed layers for YBa2Cu3O7−x coated conductors

    La2Zr2O7 (LZO) buffer layers were deposited on bi-axially textured Ni–W substrates with CeO2 seed layer by radio-frequency magnetron sputtering for the large-scale application of YBa2Cu3O7−x (YBCO) coated conductors. The microstructure and surface morphology of LZO buffer layers were studied by X-ray diffraction, optical microscopy, field emission scanning electron microscopy and atomic force microscopy. The influences of substrate temperature and oxygen partial pressure on the microstructure and surface morphology of LZO buffer layers were discussed. It was found that epitaxial LZO films were preferentially c-axis oriented without microcracks, with no degradation of crystallographic texture and with high surface crystallinity. Crack-free and strong c-axis aligned LZO films with no random orientation were obtained at relatively low substrate temperatures of 600–800 °C and in flowing 40 Pa gas mixtures of Ar–O2 with an effective oxygen partial pressure of 0.1–20 Pa. In addition, LZO films grown in low oxygen partial pressure have a smoother surface than films in higher oxygen partial pressure. Then, we fabricated YBCO coated conductors on the high-quality LZO buffer layers by pulsed laser deposition. The critical current density Jc = 2.25 MA/cm2 and critical current Ic = 180 A/cm of 0.8-μm-thick YBCO film at 77 K, self field were obtained. The magnetic field and angular dependences of critical current per width were discussed. Highly textured LZO films grown on CeO2 seed layer were suitable as a buffer layer for the growth of YBCO coated conductors with high currents. - Highlights: • La2Zr2O7 (LZO) films were firstly fabricated by magnetron sputtering. • We firstly used the buffer architecture LZO/CeO2 (seed). • We firstly fabricated YBa2Cu3O7+x films directly on LZO films

  16. Faceting of (001) CeO2 Films: The Road to High Quality TFA-YBa2Cu3O7 Multilayers

    CeO2 films are technologically important as a buffer layer for the integration of superconducting YBa2Cu3O7 films on biaxially textured Ni substrates. The growth of YBa2Cu3O7 layers on the CeO2 cap layers by the trifluoroacetate (TFA) route remains a critical issue. To improve the accommodation of YBa2Cu3O7 on CeO2, surface conditioning or CeO2 is required. In this work we have applied ex-situ post-processes at different atmospheres to the CeO2 layers deposited on YSZ single crystals using rf sputtering. XPS analysis showed that post-annealing CeO2 layer in Ar/H2/H2O catalyses in an unexpected way the growth of (001)- terraces. We also report on the growth conditions of YBa2Cu3O7-TFA on CeO2 buffered YSZ single crystal grown by chemical solution deposition and we compare them with those leading to optimized YBa2Cu3O7-TFA films on LaAlO3 single crystals. Critical currents up to 1.6 MA/cm2 at 77 K have been demonstrated in 300 nm thick YBa2Cu3O7 layers on CeO2/YSZ system. The optimized processing conditions have then been applied to grow YBa2Cu3O7-TFA films on Ni substrates having vacuum deposited cap layers of CeO2

  17. Template electrosynthesis of CeO2 nanotubes

    Nanotube arrays of CeO2 were produced in a single step by potentiostatic electrochemical deposition from a non-aqueous electrolyte, using anodic alumina membrane templates. The CeO2 nanotubes showed a polycrystalline structure, and they were assembled in the membrane nanochannels. The nanotubes had somewhat uniform diameters, with an average external value of about 210 nm, and a maximum length of about 60 μm; the latter parameter was controlled by the electrodeposition time. Each single nanotube was found to consist of crystalline grains having a size of about 3 nm. Raman analysis shows that these CeO2 nanotubes are suitable for catalytic applications

  18. Pulsed electron deposition (PED) of single buffer layer for 'low-cost' YBCO coated conductors

    The challenge for the commercialization of YBCO Coated Conductors (CC) is the development of a low cost manufacturing process to allow for a cheap, fast and continuous deposition of superconducting coatings with high electrical performance. We are currently investigating 2 ways to reduce the CC production costs: i) reducing the complexity of the CC architecture, by growing a single buffer layer based on doped CeO2, and ii) utilizing a new reel-to-reel apparatus for long length CC processing, equipped with a cheap and reliable deposition system (PED, Pulsed Electron Deposition). In this work we report on the successful continuous deposition of very thick (up to 700 nm) doped-CeO2 single buffer layers on biaxially textured Ni-5at%W substrates by PED. XRD patterns display complete orientation and very good texture quality of our samples (FWHM out-of-plane values of ∼ 6 deg.), over 20 cm length. Optical and electron microscopy show a dense and crack-free film surface and dielectric strength measurement confirms excellent insulating properties. Preliminary results indicate that the simplified single buffer layer structure could be a reliable solution for the reduction of HTS CC production costs

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

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


    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, while RF magnetron sputtering...... made by fitting the thermal parameters in the model with and without an additional CeO2 layer were found to be in agreement with the experimental observations....

  20. Transport properties of pure and doped CeO2

    The oxides that crystallize in the fluorite structure are noted for their ability to accommodate a high degree of disorder on the oxygen sublattice. Cerium oxide is a semiconductor and ionically- conductor oxide with important electrical and chemical applications as a solid oxide fuel cell electrolyte, a catalyst for gas phase oxidation and reduction reactions, and as an oxygen buffer in the automotive 3-way catalyst. Polycrystalline samples of different grain size were prepared by uniaxial hot pressing and their sintering behavior was investigated, at various temperatures and pressures. The cerium dioxide has been prepared by this way and characterized by X-ray diffraction and transmission electron microscopy (SEM). Measurements of electronic conductivity have confirmed that electron transport in CeO2-x proceeds via a small polaron process. The electrical properties of CeO2-UO2 solid solutions are examined as a function of temperature (600 deg. C - 1400 deg. C), oxygen partial pressure (10 - 22 - 1 atm), and Ce/U ratio (CeO2- 1.65% UO2, CeO2- 5% UO2). The PO2 values were controlled by mixing Ar-O2 and CO2-H2 or Ar-H2, gases in appropriate proportions. Electrical conductivity data obtained for U-doped CeO2 solid solution were shown to be in good agreement with predictions and thereby enable derivation of a number of key parameters, including those controlling generation of oxygen Frenkel defects, doubly ionized vacancies and electrons by reduction, and electron mobilities. (authors)

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

    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. - Highlights: • The catalysts were synthesized via a facile thermal decomposition method which was simple, fast and feasible method. • Degradation of methylene blue and real effluent were carried out under visible light. • The photocatalytic activity of nanocomposite materials is higher than that of single phase material

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

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


    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.

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

    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

  4. The mechanism of the nano-CeO2 films deposition by electrochemistry method as coated conductor buffer layers

    Highlights: • Crack-free CeO2 film thicker than 200 nm was prepared on NiW substrate by ED method. • Different electrochemical processes as hydroxide/metal mechanisms were identified. • The CeO2 precursor films deposited by ED method were in nano-scales. - Abstract: Comparing with conventional physical vapor deposition methods, electrochemistry deposition technique shows a crack suppression effect by which the thickness of CeO2 films on Ni–5 at.%W substrate can reach a high value up to 200 nm without any cracks, make it a potential single buffer layer for coated conductor. In the present work, the processes of CeO2 film deposited by electrochemistry method are detailed investigated. A hydroxide reactive mechanism and an oxide reactive mechanism are distinguished for dimethyl sulfoxide and aqueous solution, respectively. Before heat treatment to achieve the required bi-axial texture performance of buffer layers, the precursor CeO2 films are identified in nanometer scales. The crack suppression for electrochemistry deposited CeO2 films is believed to be attributed to the nano-effects of the precursors

  5. Facile hydrothermal synthesis of CeO2 nanopebbles

    N Sabari Arul; D Mangalaraj; Jeong In Han


    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.

  6. Convenient synthesis of CeO2 nanotubes

    A simple and facile route was used in the fabrication of CeO2 nanotubes within anodic alumina membrane. A piece of membrane was first immersed into Ce(NO3)3 aqueous solution under ambient conditions. After dried at 50 deg. C and thermally calcined at 150 deg. C and 550 deg. C, CeO2 nanotubes can be easily synthesized. The characterization with electron microscopy and X-ray diffraction indicated that CeO2 nanotubes were composed of tiny well-crystalline CeO2 nanoparticles

  7. Structural, morphological, Raman, optical, magnetic, and antibacterial characteristics of CeO2 nanostructures

    Fazal Abbas; Javed Iqbal; Tariq Jan; Noor Badshah; Qaisar Mansoor; Muhammad Ismail


    In this study, CeO2nanostructures were synthesized by a soft chemical method. A hydrothermal treatment was observed to lead to an interesting morphological transformation of the nanoparticles into homogeneous microspheres composed of nanosheets with an average thickness of 40 nm. Structural analysis revealed the formation of a single-phase cubic fluorite structure of CeO2for both samples. A Raman spectroscopic study confirmed the XRD results and furthermore indicated the presence of a large number of oxygen vacancies in the nanosheets. These oxygen vacancies led to room-temperature ferromagnetism (RTFM) of the CeO2 nanosheets with enhanced magnetic characteristics. Amazingly, the nanosheets exhibited substantially greater antibacterial activity than the nanoparticles. This greater antibacte-rial activity was attributed to greater exposure of high-surface-energy polar surfaces and to the presence of oxygen vacancies.

  8. Structural, morphological, Raman, optical, magnetic, and antibacterial characteristics of CeO2 nanostructures

    Abbas, Fazal; Iqbal, Javed; Jan, Tariq; Badshah, Noor; Mansoor, Qaisar; Ismail, Muhammad


    In this study, CeO2 nanostructures were synthesized by a soft chemical method. A hydrothermal treatment was observed to lead to an interesting morphological transformation of the nanoparticles into homogeneous microspheres composed of nanosheets with an average thickness of 40 nm. Structural analysis revealed the formation of a single-phase cubic fluorite structure of CeO2 for both samples. A Raman spectroscopic study confirmed the XRD results and furthermore indicated the presence of a large number of oxygen vacancies in the nanosheets. These oxygen vacancies led to room-temperature ferromagnetism (RTFM) of the CeO2 nanosheets with enhanced magnetic characteristics. Amazingly, the nanosheets exhibited substantially greater antibacterial activity than the nanoparticles. This greater antibacterial activity was attributed to greater exposure of high-surface-energy polar surfaces and to the presence of oxygen vacancies.

  9. Signature of room temperature ferromagnetism in Mn doped CeO2 nanoparticles

    We report structural and magnetic properties of Mn doped CeO2 nanoparticles using X-ray diffraction (XRD), field emission transmission electron microscopy (FE-TEM) and dc magnetization measurements. XRD results infer that all the samples have single phase nature and lattice parameters decrease with Mn doping. The particle size calculated using XRD and TEM analysis was found to decrease with Mn doping. Field cooled magnetization measurement shows that the transition temperature is above room temperature. Magnetic hysteresis loop studies indicate that undoped and Mn doped CeO2 nanoparticles show weak ferromagnetic behavior at room temperature.

  10. Non-Stoichiometry of UO2-CeO2: The System UO2-CeO2-CeO1.5 at 900 to 1200°C

    This investigation covers the substoichiometric fluorite (UO2-CeO2) phase, that is, the behaviour of the system U1-yCe1-yO2+x. Though UO2 and CeO2 are completely miscible, and in the CeO2-CeO1-5 system the fluorite phase extends to CeO1.72 , the UO2-CeO2-CeO1.5 system is characterized by a large two-phase region, where two fluorite- type structures, one CeO2-rich, the other UO2-rich, coexist. Only in the UO2-rich corner of the ternary system is a noticeable single-phase region present. This is in contrast to the CeO2-UO2-UO267 system where a large single-phase region exists. The oxygen activity as a function of composition x was measured in U1-yCe1-yO2+x (y = 0.15 and 0.35) at 900°C, using H2/H2O and metal/metal oxide equilibria. In all cases the oxygen activity increases extremely rapidly with decreasing x; the behaviour of the system resembles that of dilute solutions of UO2+X in ThO2. Both systems can be explained by assuming defect complexes: a vacancy bound to two Ce3+, an interstitial oxygen bound to two U5+. (author)

  11. Facile synthesis of ferromagnetic Ni doped CeO2 nanoparticles with enhanced anticancer activity

    Abbas, Fazal; Jan, Tariq; Iqbal, Javed; Ahmad, Ishaq; Naqvi, M. Sajjad H.; Malik, Maaza


    NixCe1-xO2 (where x = 0, 0.01, 0.03, 0.05 and 0.07) nanoparticles were synthesized by soft chemical method and were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, UV-vis absorption spectroscopy and vibrating sample magnetometer (VSM). XRD and Raman results indicated the formation of single phase cubic fluorite structure for the synthesized nanoparticles. Ni dopant induced excessive structural changes such as decrease in crystallite size as well as lattice constants and enhancement in oxygen vacancies in CeO2 crystal structure. These structural variations significantly influenced the optical and magnetic properties of CeO2 nanoparticles. The synthesized NixCe1-xO2 nanoparticles exhibited room temperature ferromagnetic behavior. Ni doping induced effects on the cytotoxicity of CeO2 nanoparticles were examined against HEK-293 healthy cell line and SH-SY5Y neuroblastoma cancer cell line. The prepared NixCe1-xO2 nanoparticles demonstrated differential cytotoxicity. Furthermore, anticancer activity of CeO2 nanoparticles observed to be significantly enhanced with Ni doping which was found to be strongly correlated with the level of reactive oxygen species (ROS) production. The prepared ferromagnetic NixCe1-xO2 nanoparticles with differential cytotoxic nature may be potential for future targeted cancer therapy.


    Hu Ximing; Qu Jing; Wang Binqiang; Wu Jiangxing


    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.

  13. Three-Dimensional Structure of CeO2 Nanocrystals

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


    Visualization of three-dimensional (3D) structures of materials at the nanometer scale can shed important information on the performance of their applications and provide insight into the growth mechanism of shape-controlled nanomaterials. In this paper, the 3D structures and growth pathway of CeO2...... samples synthesized under different conditions. The homogeneous growth environment in solution with polyvinylpyrrolidone (PVP) molecules led to the formation of regular octahedral CeO2 nanocrystals with small {001} facet truncations. When the PVP surfactant was removed, the aggregation of regular...... truncated octahedral CeO2 particles through a lattice matched interface generated irregular compressed truncated octahedral CeO2 nanoparticles. The formation of this irregular shape is attributed to the lower surface diffusion and slow incorporation of atoms on surfaces by step attachment of the fused...

  14. CeO2 nanoparticles for high performance supercapacitor electrode

    Cerium Oxide plays a vital role in rising technologies for energy-related applications. In this study, CeO2 nanoparticles have been successfully synthesized by microwave irradiation method and its capacitance performance is further investigated. Prepared nanoparticles were analysed by X-Ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). X-ray diffraction analysis confirms that CeO2 Nanoparticles in cubic phase and the grain size was calculated to be 15 nm using Debye-Scherrer formula. The FTIR spectrum of the CeO2 exhibits the stretching vibration of Ce-O at about 601 cm-1. The SEM analysis shows the irregular spherical morphology with some of the particles agglomerated. Electrochemical characterization of the sample was performed using a standard three electrode cell configuration. Cyclic Voltammogram (CV) and galvanostatic (GV) charge-discharge measurements demonstrated that the CeO2 electrode exhibited superior capacitive properties in 1 M Na2SO4 aqueous solution within the potential range -0.2V to 1.5V The discharge curves are linear in the total range of potential with constant slopes at a constant current of 0.9 A/g showing perfect capacitive behavior. These findings can open up new opportunities for CeO2 nanoparticles in constructing the high-performance electrochemical supercapacitors as well as other energy storage devices. (author)

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

    Anushree, Sharma, C.; Kumar, S.


    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.

  16. Reel-to-reel continuous simultaneous double-sided deposition of highly textured CeO2 templates for YBa2Cu3O7-δ coated conductors

    A reel-to-reel system which allows simultaneous two-sided deposition of epitaxial CeO2 buffer layers on long length biaxially textured Ni-5 at.%W tape with direct current (dc) reactive magnetron sputtering is described. Deposition is accomplished through two opposite symmetrical sputtering guns with a radiation heater. Meter-long double-sided epitaxial CeO2 buffer layers have been produced for the first time on textured metal substrates in a run using a reel-to-reel process with a speed of about 1.2 m h-1. The CeO2 films were characterized by means of x-ray diffraction (XRD) and atomic force microscopy (AFM). The samples exhibited good epitaxial growth with the c-axis perpendicular to the substrate surface for both sides. Full width at half maximum (FWHM) values of the out-of-plane and in-plane orientation for both sides were 3.20 and 3.10, 5.30 and 5.10, respectively. AFM observations revealed a smooth, dense and crack-free surface morphology. In addition, x-ray scans have been performed as a function of length to determine the crystallographic consistency of the epitaxial CeO2 over the length. Subsequently anyttria-stabilized zirconia (YSZ) barrier and CeO2 cap layers were deposited to complete the CeO2/YSZ/CeO2 structure via the same process. Epitaxial YBa2Cu3O7-δ (YBCO) films grown by dc sputtering on the short prototype CeO2/YSZ/CeO2/NiW conductors yielded self-field critical current densities (Jc) as high as 1.3 MA cm-2 at 77 K. An Ic value of 113 A cm-1 was obtained for double-sided YBCO coated conductors

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

    Nam, Joo-Youn


    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.

  18. Electrochemical and structural analysis of the RE3+:CeO2 nanopowders from combustion synthesis

    Highlights: • Rare earth elements doped ceria were synthesized by citrate nitrate auto-combustion method. • XRD revealed that they crystallize as single-phase cubic fluorite structure. • PL, FTIR and RAMAN studies were carried to analyze the existence of functional groups. • The morphology of the nanoparticles and compacts were analyzed by SEM and HRTEM. • Cyclic voltammetry (CV) for RE3+:CeO2 were measured and compared. - Abstract: The reported article deals with the synthesis and characterization of rare earth ions doped ceria (RE3+:CeO2) nanopowders from citrate nitrate auto-combustion route. The crystalline nature and lattice planes of the nanocrystalline RE3+:CeO2 powders were analyzed by X-ray diffraction (XRD) and Selected Area Electron Diffraction (SAED) profile fit. The excited state absorption (ESA) and energy transfer up-conversion (ETU) were studied by photoluminescence (PL) measurement. The spectroscopic properties of the powders were studied using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. The surface morphology, average size, distribution and orientation of the lattice planes of the nanoparticles were studied by using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The size of RE3+:CeO2 nanoparticles were found to be in the range from 15 to 30 nm which has good agreement with the HRTEM results. The changes in current density with increasing sweep scan potential of the doped ceria powders were studied by cyclic voltammetry (CV) analysis. The specific capacitance range of the rare earths doped ceria of Er:CeO2, Pr:CeO2, Yr:CeO2 and Nd:CeO2 were calculated as (12.9–86.5), (20–72.4), (80–375) and (0.92–4.22) respectively

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

    Phuong Thi Mai Pham


    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.

  20. Investigation on the magnetic behaviour of CeO2 nanoparticles prepared by co-precipitation method

    Cerium oxide (CeO2) nanoparticles have been extensively studied owing to their potential in the fields of polishing powders, catalysts, gas sensors and electrode materials for solid oxide fuel cells. Numerous techniques have been proposed to synthesize nano-sized CeO2 particles with promising control of properties. Among them, due to the simple process, easy scale-up and low cost, the precipitation technique attracts more attention. In recent years, magnetic study on bulk and nanocrystalline CeO2 is gaining more interest in order to have a profound understanding of its magnetic origin. In this paper, we report the investigation of structural, optical and magnetic properties of nanocrystalline CeO2 synthesized by co-precipitation method. Phase analysis of the samples was done using X-Ray Diffraction (XRD) technique, which confirms the single phase formation of cubic CeO2. Transmission electron microscopy (TEM) images clearly illustrate the nanocrystalline nature (∼ 20 nm) and a uniform particle size distribution. The band gap, calculated using UV-Vis reflectance spectroscopy, was found to be 3.4 eV which is slightly greater than that of its bulk counterpart. Magnetization data was recorded using vibrating sample magnetometer (VSM) with a maximum applied field of ± 7 kOe. M-H curve of CeO2 nanoparticles presents a clear diamagnetic behaviour at room temperature in contrary to the earlier studies; the reason for which is discussed in detail based on the significant role of oxygen vacancies. (author)

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

    Zipkes, Christoph; Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael


    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...

  2. Effects of doping CeO2/TiO2 on structure and properties of silicate glass

    Highlights: • Doping CeO2 results in depolymerization and narrowed Qn distribution. • Co-doping CeO2 and TiO2 favors enhanced network and broader Qn distribution. • Cerium acts as modifier and titanium as intermediate in glass network structure. • Adding CeO2/TiO2 results in decreased optical band gap. • Doping-induced structural modifications affect mechanical properties. - Abstract: In order to elucidate the effects of doping CeO2/TiO2 on the structure and physical properties of silicate glass, glasses with composition 72SiO2–3Al2O3–10Na2O–10K2O–5CaO doped with varied ratios of CeO2/TiO2 were synthesized by melt-quenching method and were characterized by X-ray diffraction, infrared and Raman spectrometry, UV–Visible spectrophotometry and micro-indentations. X-ray diffraction conforms the amorphous state of doped glasses. The spectroscopic analysis reveals that doping CeO2 alone results in depolymerization of glass network and narrowed distribution of Qn (Si–O tetrahedral with n bridging oxygen atoms), while doping TiO2 singly or combined with CeO2 favors the enhanced polymerization of network and regains a broader Qn distribution relative to doping CeO2 alone. It is proposed that doped cerium and titanium in glass exists in multivalent state and the former in presence of trivalent state preferentially acts as modifier inducing network depolymerization, whilst the latter in form of tetrahedral tends to interconnect network units as intermediate. Doped cerium in trivalent state contributes mainly to the red-shift of absorption edge while titanium suppresses such change of absorption band. Either adding cerium alone or co-doping with titanium will result in decreased optical band gap due to the structural modifications. The relatively loosened structure due to depolymerization induced by cerium is responsible for the decline in hardness and E-modulus but rising in fracture toughness, whereas network compactness by virtue of interconnectivity of

  3. Mg Doping Induced Effects on Structural, Optical, and Electrical Properties as Well as Cytotoxicity of CeO2 Nanostructures

    Iqbal, Javed; Jan, Tariq; Awan, M. S.; Naqvi, Sajjad Haider; Badshah, Noor; ullah, Asmat; Abbas, Fazzal


    Here, Mg x Ce1- x O2 (where x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) nanostructures have been successfully synthesized by using a simple, easy, and cost-effective soft chemical method. X-ray diffraction (XRD) patterns substantiate the single-phase formation of a CeO2 cubic fluorite structure for all samples. Infrared spectroscopy results depict the presence of peaks only related to Ce-O bonding, which confirms the XRD results. It has been observed via ultraviolet (UV)-visible spectroscopy that Mg doping has tuned the optical band gap of CeO2 significantly. The electrical conductivity of CeO2 nanostructures has been found to increase with Mg doping, which is attributed to enhancement in carrier concentration due to the different valance states of dopant and host ions. Selective cytotoxic behavior of Mg x Ce1- x O2 nanostructures has been determined for neuroblastoma (SH-SY5Y) cancerous and HEK-293 healthy cells. Both doped and undoped CeO2 nanostructures have been found to be toxic for cancer cells and safe toward healthy cells. This selective toxic behavior of the synthesized nanostructures has been assigned to the different levels of reactive oxygen species (ROS) generation in different types of cells. This makes the synthesized nanostructures a potential option for cancer therapy in the near future.

  4. Optical properties of CeO2 thin films

    S Debnath; M R Islam; M S R Khan


    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.

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

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


    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.

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

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


    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. The Effect of CeO2 Antireflection Layer on the Optical Properties of Thermochromic VO2 Film for Smart Window System

    Koo, Hyun; Shin, Dongmin; Bae, Sung-Hwan; Ko, Kyeong-Eun; Chang, Se-Hong; Park, Chan


    CeO2-VO2 bilayer structure was fabricated to investigate the effect of depositing CeO2 film on the optical properties of VO2 film for smart window application. CeO2 was employed as an antireflection (AR) layer material of VO2 film because of its advantages which include high transparency in the visible-near infrared range and high refractive index. All the films were deposited on soda-lime glass substrate by pulsed laser deposition method. Optical calculations were carried out using transfer-matrix method for the purpose of designing CeO2-VO2 bilayer structure with enhanced integrated luminous transmittance (T lum) and switching efficiency (ΔT sol). The optical constants of VO2 and CeO2 films needed for the optical calculation were measured by spectroscopic ellipsometer. The curve of T lum the shape of which depends on the thickness of CeO2 layer, was calculated in each VO2 sample, which showed two maxima. The samples were divided into two groups; one for the highest enhancement of T lum and the other for balanced enhancement between T lum and ΔT sol. The sample with the structure of ~60 nm CeO2 AR layer on 39-nm thick VO2 film showed large increase of T lum (~27%) with ΔT sol of ~5%, which is the largest increase in T lum reported so far. Two samples in the other group showed the balanced enhancement in T lum (~57, ~50%) and ΔT sol (~9, ~10.5%). The effect of CeO2 AR layer on the optical properties of VO2 film was confirmed with the optical calculation and the experimental results. CeO2-VO2 bilayer structure showed notable improvement of optical properties compared to the single VO2 film, indicating that CeO2 layer can be effectively used as the antireflection layer while working as a protective layer that can prevent the oxidation of VO2 layer as well.

  8. Comparator circuits with local ramp buffering for a column-parallel single slope ADC

    Milkov, Mihail M.


    A comparator circuit suitable for use in a column-parallel single-slope analog-to-digital converter comprises a comparator, an input voltage sampling switch, a sampling capacitor arranged to store a voltage which varies with an input voltage when the sampling switch is closed, and a local ramp buffer arranged to buffer a global voltage ramp applied at an input. The comparator circuit is arranged such that its output toggles when the buffered global voltage ramp exceeds the stored voltage. Both DC- and AC-coupled comparator embodiments are disclosed.

  9. Ab initio thermodynamic evaluation of Pd atom interaction with CeO(2) surfaces.

    Mayernick, Adam D; Janik, Michael J


    Palladium supported on ceria is an effective catalytic material for three-way automotive catalysis, catalytic combustion, and solid-oxide fuel cell (SOFC) anodes. The morphology, oxidation state, and particle size of Pd on ceria affect catalytic activity and are a function of experimental conditions. This work utilizes ab initio thermodynamics using density functional theory (DFT) (DFT+U) methods to evaluate the stability of Pd atoms, PdO(x) species, and small Pd particles in varying configurations on CeO(2) (111), (110), and (100) single crystal surfaces. Over specific oxygen partial pressure and temperature ranges, palladium incorporation to form a mixed surface oxide is thermodynamically favorable versus other single Pd atom states on each ceria surface. For example, Pd atoms may incorporate into Ce fluorite lattice positions in a Pd(4+) oxidation state on the CeO(2) (111) surface. The ceria support shifts the transition between formal Pd oxidation states (Pd(0), Pd(2+), Pd(4+)) relative to bulk palladium and stabilizes certain oxidized palladium species on each surface. We show that temperature, oxygen pressure, and cell potential in a SOFC can influence the stable states of palladium supported on ceria surfaces, providing insight into structural stability during catalytic operation. PMID:19725615

  10. Investigating the mechanism of ferromagnetic exchange interaction in non-doped CeO2 with regard to defects and electronic structure

    Highlights: ► Hydrogenation induces ferromagnetism in paramagnetic CeO2 matrix. ► “Switch” action of ferromagnetism between hydrogenation and re-heating in CeO2. ► Ferromagnetism shows close relation with oxygen vacancies in magnetic dielectrics. ► The F+ centers play key role in ferromagnetism in CeO2. - Abstract: We report a systematic structural, electronic, and magnetic investigation on occurrence of ferromagnetism and its “switch” action in non-doped bulk ceria (CeO2). The magnetization measurements establish that the pristine CeO2 having a paramagnetic ground state can be driven to a ferromagnetic state at room temperature, when hydrogenated at 600 °C. The observed H-induced ferromagnetism is closely related to the oxygen vacancies and the Ce valence state. X-ray photoemission results depict that Ce ions reduce from 4+ to 3+ state along with creation of oxygen vacancies during the ferromagnetic transition. A parallel variation of carrier concentration, revealed by resistance measurements, seems to be a secondary effect of the oxygen vacancies creation. The F+ centers, i.e. the electrons in singly occupied oxygen vacancies, seem to play the key role in establishing the ferromagnetism in CeO2, in the framework of bound magnetic polaron model. The exchange mechanism shows a “switch” action such that one could remove the oxygen vacancies through re-heating the H2-treated CeO2 and the ferromagnetism is subsequently vanished.

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

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


    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.

  12. Application of nanostructured Ca doped CeO2 for ultraviolet filtration

    Calcium doped CeO2 nanoparticles with doping concentrations between 0 and 50 mol% were synthesized by a co-precipitation method for ultraviolet filtration application. Below 20 mol% doping concentration, the samples were single-phase. From 30 mol%, CaCO3 appears as a secondary phase. The calculated CeO2 mean crystallite size was 9.3 nm for the pure and 5.7 nm for the 50 mol% Ca-doped sample. Between 250 and 330 nm, the absorbance increased for the 10, 30, and 40 mol% Ca-doped samples compared to the pure one. The band-gap was found to be 3.20 eV for the undoped, and between 3.36 and 3.51 eV for the doped samples. The blue shifts are attributed to the quantum confinement effect. X-ray photoelectron spectroscopy showed that the Ce3+ atomic concentration in the pure sample was higher than that of the 20 mol% Ca-doped sample.


    Naveen Ravela


    Full Text Available This paper presents the determination of buffer size for machines in single and multi row Flexible Manufacturing System (FMS for the best layout obtained by genetic algorithm (GA throughsimulation. To maximize the operating performance of FMS, many parameters must be considered, including the part types, sequencing, cost of transport between workstations, distance between machinesand buffer sizes. Of the various critical factors, following three are considered for analysis: (1 minimizing the buffer size (2 minimizing the blocking and (3 maximizing the machine utilization.Simulation enables more efficient planning of the whole FMS, easy modifications before implementation on the real system. The software package FLEXSIM is used to develop the simulation model. A model ofa optimum layout FMS obtained by GA that may contain a number of machines, input and output buffers, capturing part types flow quantities, part routes, from the database and AGV’s used as a meansof transport, is built by FLEXSIM software. Analysis is done on the model to determine the optimum buffer size for the machines. Thus by performing simulation on the model optimum buffer size in theindividual rows are established.

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

    Shan Wenjuan; Guo Hongjuan; Liu Chang; Wang Xiaonan


    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.

  15. A new single buffer layer for YBCO coated conductors prepared by chemical solution deposition

    Li Guo [Key Laboratory of Advanced Technologiesof Materials (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Pu Minghua [Key Laboratory of Advanced Technologiesof Materials (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Du Xiaohua [Key Laboratory of Advanced Technologiesof Materials (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhang Yanbing [Key Laboratory of Advanced Technologiesof Materials (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhou Huaming [Key Laboratory of Advanced Technologiesof Materials (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China); Zhao Yong [Key Laboratory of Advanced Technologiesof Materials (Ministry of Education of China), Superconductivity R and D Center (SRDC), Mail Stop 165, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)]. E-mail:


    A new single buffer layer YBiO{sub 3} has been proposed for YBCO coated conductors. Highly c-axis oriented YBiO{sub 3} buffer layer has been deposited on single crystal LaAlO{sub 3} by a low-cost chemical solution deposition method in a temperature range as low as 730-800 C in air. A very dense, smooth, pinhole-free morphology has been observed for YBiO{sub 3} buffer layer. Dense, homogeneous and epitaxially grown YBCO film has been obtained with its onset critical temperature 90 K and J {sub c} (77 K, 0 T) = 3.1 MA/cm{sup 2}. The addition of Bi{sub 2}O{sub 3}, which melts at around 817 C, has been argued to be responsible for the densification as well as low-process temperature of YBiO{sub 3} buffer layer. These results offer an alternative to prepare desirable buffer layer(s) for YBCO coated conductors via a cost-effective and easily scalable route.0.

  16. A new single buffer layer for YBCO coated conductors prepared by chemical solution deposition

    A new single buffer layer YBiO3 has been proposed for YBCO coated conductors. Highly c-axis oriented YBiO3 buffer layer has been deposited on single crystal LaAlO3 by a low-cost chemical solution deposition method in a temperature range as low as 730-800 C in air. A very dense, smooth, pinhole-free morphology has been observed for YBiO3 buffer layer. Dense, homogeneous and epitaxially grown YBCO film has been obtained with its onset critical temperature 90 K and J c (77 K, 0 T) = 3.1 MA/cm2. The addition of Bi2O3, which melts at around 817 C, has been argued to be responsible for the densification as well as low-process temperature of YBiO3 buffer layer. These results offer an alternative to prepare desirable buffer layer(s) for YBCO coated conductors via a cost-effective and easily scalable route

  17. Collective magnetic response of CeO2 nanoparticles

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


    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, 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.

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

    Sumanta Kumar Meher; G Ranga Rao


    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.

  19. Photocatalytic degradation mechanisms of CeO2/Tb2O3 nanotubes

    Highlights: • CeO2/Tb2O3 nanotubes have been synthesized using the surfactant free co-precipitation method. • HRTEM images, XPS spectra, and EDAX profiles showed that the as-synthesized samples were CeO2/Tb2O3 nanotubes. • Photocatalytic activity of the synthesized catalysts was evaluated by degrading Methylene blue under visible light irradiation. • Estimated rate constants for the CeO2 nanoparticles and the CeO2/Tb2O3 nanotubes were 0.0134 and 0.0317 min−1, respectively. • Photodegradation efficiency of CeO2/Tb2O3 nanotubes was 93% after 75 min. - Abstract: CeO2/Tb2O3 nanotubes (NTs) have been synthesized using the surfactant free co-precipitation method. High resolution transmission electron microscopy (HRTEM) images, X-ray spectroscopy (XPS) spectra, and energy dispersive X-ray (EDAX) profiles showed that the as-synthesized samples were CeO2/Tb2O3 NTs. The photocatalytic activity of the synthesized catalysts was evaluated by degrading Methylene blue (MB) under visible light irradiation. The fitting of the absorbance maximum as a function of time showed that the photodegradation of the MB followed pseudo-first-order reaction kinetics. The estimated rate constants for the CeO2 NPs and the CeO2/Tb2O3 NTs were found to be 0.0134 and 0.0317 min−1, respectively. The photodegradation efficiency of CeO2/Tb2O3 nanotubes was 93% after 75 min, which was found to be higher than those of CeO2 NPs (66%)

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

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


    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.

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

    The immersion of a single ion confined by a radiofrequency (RF) 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 RF 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 atom-ion mass ratio, trap geometry, differential cross-section and non-uniform neutral atom density distribution. Experimental results are well reproduced by our model considering only elastic collisions. 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.

  2. Preparation and characterizations of platinum electrocatalysts supported on thermally treated CeO2–C composite support for polymer electrolyte membrane fuel cells

    Highlights: • CeO2–C composite support was prepared by a sol-gel approach with an average particle size of 2.5 nm. • The crystallinity of ceria was tuned by thermal treatment from 400 °C to 600 °C. • Well correlated Pt–ceria interaction was found for the Pt electrocatalysts in PEMFCs. - Abstract: A sol–gel approach was used to synthesize highly dispersed carbon-supported ceria composite support (CeO2–C) having an average particle size of 2.5 nm with sodium citrate as a ligand. The CeO2–C composite was then heated in N2 atmosphere at different temperatures to induce crystallinity variation. Pt electrocatalysts were prepared by the conventional ethylene glycol method using the thermally treated composite support (CeO2–C-T) and then characterized by X-ray diffraction and transmission electron microscopy. Electrochemical evaluations of Pt/CeO2–C-T catalytic activity were performed for methanol oxidation and oxygen reduction reactions. An optimized heating temperature was found at 550 °C for CeO2–C, and Pt/CeO2–C-550 demonstrated the highest mass activity of 0.71 A mg−1 for methanol oxidation (∼100% that of Pt/C-JM from Johnson Matthey) and 17 mV more positive shift of the half-wave potential for oxygen reduction relative to that of Pt/C–JM. The maximum power density of the membrane electrode assembly (MEA) with Pt/CeO2–C-550 cathode catalyst in a H2/air polymer electrolyte membrane fuel cell was 678 mW cm−2, which was 7% higher than that of MEA prepared with Pt/C–JM under identical operating conditions. Heating CeO2–C at 550 °C induced increased crystallinity without sacrificing particle agglomeration, which was beneficial for Pt dispersion (reduced particle size). Meanwhile catalytic activity was further enhanced because of Pt–metal oxide interactions and the known oxygen buffer capability of CeO2

  3. Anomalous compressive behavior in CeO2 nanocubes under high pressure

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


    is found to be 10 GPa for 4.7 nm and 16 GPa for 5.6 nm CeO2 nanocubes. The particle size dependence of the threshold pressure for the hardening of CeO2 nanoparticles is quite unusual. First-principles electronic calculations show that the increased bulk modulus of the nanocrystal is due...

  4. Preparation and performance of CeO2 hollow spheres and nanoparticles

    ZHANG Wenwen; CHEN Donghui


    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.

  5. Electrochemical determination of dopamine based on electrospun CeO2/Au composite nanofibers

    An electrochemical method for the detection of dopamine based on a glass carbon electrode modified with electrospun CeO2/Au composite nanofibers was investigated in this article. The CeO2/Au composite nanofibers were prepared by the electrospinning technique and then annealed in air. The CeO2/Au composite nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. Cyclic voltammetry (CV) showed that the electrospun CeO2/Au composite nanofibers modified carbon glass electrode exhibited an excellent electrocatalytic response to the dopamine (DA). The detection limit (S/N = 3) was as low as 0.056 μM and the sensitivity could reach 127 μA mM−1 cm−2. All these demonstrated that the electrospun CeO2/Au composite nanofibers were good electrocatalyst for the oxidation of dopamine

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

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


    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.

  7. Far-infrared spectroscopic study of CeO2 nanocrystals

    We present the far-infrared reflectivity spectra of 5 nm-sized pure and copper-doped Ce1−xCuxO2−y (x = 0; 0.01 and 0.10) nanocrystals measured at room temperature in the 50–650 cm−1 spectral range. Reflectivity spectra were analyzed using the factorized form of the dielectric function, which includes the phonon and the free carriers contribution. Four oscillators with TO energies of approximately 135, 280, 370, and 490 cm−1 were included in the fitting procedure. These oscillators represent local maxima of the CeO2 phonon density of states, which is also calculated using the density functional theory. The lowest energy oscillator represents TA(L)/TA(X) phonon states, which become infrared-active Eu modes at the L and X points of the Brillouin zone (BZ). The second oscillator originates from TO(Γ) phonon states. The oscillator at ∼400 cm−1 originates from Raman mode phonon states, which at the L point of BZ also becomes infrared-active Eu mode. The last oscillator describes phonons with dominantly LO(Γ) infrared mode character. The appearance of phonon density of states related oscillators, instead of single F2uinfrared-active mode in the far-infrared reflectivity spectra, is a consequence of the nanosized dimension of the CeO2 particles. The best fit spectra are obtained using the generalized Bruggeman model for inhomogeneous media, which takes into account the nanocrystal volume fraction and the pore shape

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

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


    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 ...

  9. Bio diesel synthesis from pongamia pinnata oil over modified CeO2 catalysts

    This study investigates the use of CeO2, ZrO2, Mg O and CeO2-ZrO2, CeO2-Mg O, CeO2-ZrO2-Mg O mixed oxides as solid base catalysts for the transesterification of Pongamia pinnata oil with methanol to produce bio diesel. SO42-/CeO2 and SO42-/CeO2-ZrO2 were also prepared and used as solid acid catalysts for esterification of Pongamia pinnata oil (P-oil) to reduce the % of free fatty acid (FFA) in P-oil. The oxide catalysts were prepared by an incipient wetness impregnation method and characterized by techniques such as NH3-Tpd for surface acidity, CO2-Tpd for surface basicity and powder X-ray diffraction for crystallinity. The effect of nature of the catalyst, methanol to P-oil molar ratio and reaction time in esterification as well as in transesterification was investigated. The catalytic materials were reactive d and reused for five reaction cycles and the results showed that the ceria based catalysts have reasonably good reusability both in esterification and transesterification reaction. The test results also revealed that the CeO2-ZrO2 modified with Mg O could have potential for use in the large scale bio diesel production. (Author)

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

    Chunjie Wang


    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.

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

    Surendra, T V; Roopan, Selvaraj Mohana


    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. PMID:27236047

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

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


    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

  13. Violet/blue photoluminescence from CeO2 thin film


    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. Oxygen storage and catalytic NO removal promoted by CeO2-containing mixed oxides

    CeO2-ZrO2 mixed oxides show improved redox properties as compared to CeO2 which makes them important innovative materials for three-way catalysts. The origin of this effect and the structural/redox correlation are discussed. The influence of the improved redox capacities on the reduction of NO by CO catalyzed by Rh/CeO2-ZrO2 catalysts is reported and evidence for an active role of the CeO2-ZrO2 support in NO activation is presented. (orig.)

  15. Self-template hydrothermal synthesis of CeO2 hollow nanospheres

    CeO2 hollow nanospheres were synthesized by a low-cost and environmentally benign one-pot hydrothermal route. Templates, surfactants, or other auxiliaries were not used in the route. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and nitrogen adsorption–desorption measurements were used to characterize the products. The average diameter of hollow spheres, with shells of approximately 30 nm, was about 300 nm. The formation of these hollow spheres involved a transformation from Ce(OH)CO3 solid spheres to CeO2 hollow nanospheres. The CeO2 hollow nanospheres exhibited a higher catalytic activity on CO oxidation than CeO2 nano-octahedrons.

  16. Room-temperature synthesis and characterization of porous CeO2 thin films

    CeO2 thin films with hexagonal-shaped pores were successfully prepared by a facile electrodeposition at room temperature combined with an etching process. By using electrodeposited ZnO nanorods as a soft template, the morphology, and microstructure of the CeO2 could be controlled. TEM observation indicated that as-prepared CeO2 film is composed of nanocrystals with average size of several nanometers, while XPS analysis showed the coexistence of Ce3+ and Ce4+ in the film. The photoluminescence properties of CeO2 films were measured, which showed much higher sensitivity compared to bare substrate. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

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


    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.

  18. Design and characterization of nanoknife with buffering beam for in situ single-cell cutting

    A novel nanoknife with a buffering beam is proposed for single-cell cutting. The nanoknife was fabricated from a commercial atomic force microscopy (AFM) cantilever by focused-ion-beam (FIB) etching technique. The material identification of the nanoknife was determined using the energy dispersion spectrometry (EDS) method. It demonstrated that the gallium ion pollution of the nanoknife can be ignored during the etching processes. The buffering beam was used to measure the cutting force based on its deformation. The spring constant of the beam was calibrated based on a referenced cantilever by using a nanomanipulation approach. The tip of the nanoknife was designed with a small edge angle 5 deg. to reduce the compression to the cell during the cutting procedure. For comparison, two other nanoknives with different edge angles, i.e. 25 deg. and 45 deg., were also prepared. An in situ single-cell cutting experiment was performed using these three nanoknives inside an environmental scanning electron microscope (ESEM). The cutting force and the sample slice angle for each nanoknife were evaluated. It showed the compression to the cell can be reduced when using the nanoknife with a small edge angle 5 deg. Consequently, the nanoknife was capable for in situ single-cell cutting tasks.

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

    Woźniak Marcin


    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.


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


    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.

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

    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


    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. PMID:25768267

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

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


    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.

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

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


    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.

  4. Structural, morphological and electrical properties of spray deposited nano-crystalline CeO2 thin films

    Research highlights: → Nanocrystalline, uniform, dense, and adherent cerium oxide (CeO2) thin films have been successfully deposited by a simple and cost effective spray pyrolysis technique. CeO2 films were deposited at low substrate and annealing temperatures of 350 deg. C and 500 deg. C, respectively. The deposited film showed high oxygen ion conductivity of 5.94 x 10-3 S cm-1 at 350 deg. C. This is due to the fact that in nano-crystalline materials grain boundaries have high defect densities and the atoms there have high mobility. Due to its nano-crystalline nature, the deposited ceria material will have high sinterability, high surface area and hence can have various applications such as in intermediate temperature solid oxide fuel cell, gas sensors, electrochromic smart window devices, in corrosion protection and catalysis. - Abstract: Nanocrystalline, uniform, dense, and adherent cerium oxide (CeO2) thin films have been successfully deposited by a simple and cost effective spray pyrolysis technique. CeO2 films were deposited at low substrate and annealing temperatures of 350 deg. C and 500 deg. C, respectively. Films were characterized by differential thermal analysis, X-ray diffraction, scanning electron microscopy, atomic force microscopy; two probe resistivity method and impedance spectroscopy. X-ray diffraction analysis revealed the formation of single phase, well crystalline thin films with cubic fluorite structure. Crystallite size was found to be in the range of 10-15 nm. AFM showed formation of smooth films with morphological grain size 27 nm. Films were found to be highly resistive with room temperature resistivity of the order of 107 Ω cm. Activation energy was calculated and found to be 0.78 eV. The deposited film showed high oxygen ion conductivity of 5.94 x 10-3 S cm-1 at 350 deg. C. Thus, the deposited material shows a potential application in intermediate temperature solid oxide fuel cells (IT-SOFC) and might be useful for μ-SOFC and

  5. The influence of CeO2 on the corrosion resistance of laser remelted alloy spray coatings on steel

    The main compositions of iron-base amorphous self-fluxing alloy powders of 150 mesh, used in this work, are Fe, Cr, Ni, W, Mo, B, Si and C. The ranges of each element in at% are (65-70)Fe, (3-5)Cr, (2-4)Ni, (2-4)W, (1-2)Mo, (10-14)B, (4-7)Si and (2-3)C. The atomic ratio of metal-metalloid is about 80:20, so this alloy is abbreviated as M80X20. The material on which coatings were deposited is 1020 steel, austenitized for 1h at 880 C, water quenched, and tempered at 180 C for 1h. This heat treatment resulted in a low carbon martensite structure with a hardness of HRC35-45. After cleaning, shot blasting and preheating the steel to about 200 C, the authors sprayed a thin Ni-Al alloy layer of about 0.1--0.15mm in thickness onto the specimen by means of an oxygen-acetylene torch to provide better bonding of the coating with substrate. Then the M80X20 and M80X20+8%CeO2 alloy coatings were sprayed to a thickness of about 0.6--0.8mm. The CeO2 was added as particles of 200 mesh, injected into the spray, and became a component of the alloy coating. A single pass remelting process for the coating was then conducted by means of a 3kW CO2 laser. Corrosion tests gave the following results: (1) The addition of rare earth (8%CeO2) can improve the corrosion resistance of the laser-remelted M80X20 alloy layer remarkably, resulting in an obvious decrease of the values of ip and i'p, and hence significant improvement of passivation. (2) The addition of rare earth (8%CeO2) lowers the corrosion rate (the corrosion rate is reduced to approximately one-third of that without rare earth) of the laser remelted M80X20 alloy coating and also changes the corrosion morphology

  6. Synthesis of nanocrystalline CeO2 particles by different emulsion methods

    Cerium oxide nanoparticles were synthesized using three different methods of emulsion: (1) reversed micelle (RM); (2) emulsion liquid membrane (ELM); and (3) colloidal emulsion aphrons (CEAs). Ammonium cerium nitrate and polyoxyethylene-4-lauryl ether (PE4LE) were used as cerium and surfactant sources in this study. The powder was calcined at 500 °C to obtain CeO2. The effect of the preparation procedure on the particle size, surface area, and the morphology of the prepared powders were investigated. The obtained powders are highly crystalline, and nearly spherical in shape. The average particle size and the specific surface area of the powders from the three methods were in the range of 4–10 nm and 5.32–145.73 m2/g, respectively. The CeO2 powders synthesized by the CEAs are the smallest average particle size, and the highest surface area. Finally, the CeO2 prepared by the CEAs using different cerium sources and surfactant types were studied. It was found that the surface tensions of cerium solution and the type of surfactant affect the particle size of CeO2. - Graphical Abstract: The emulsion droplet size distribution and the TEM images of CeO2 prepared by different methods: reversed micelle (RM), emulsion liquid membrane (ELM) and colloidal emulsion aphrons (CEAs). Highlights: ► Nano-sized CeO2 was successfully prepared by three different emulsion methods. ► The colloidal emulsion aphrons method producing CeO2 with the highest surface area. ► The surface tensions of a cerium solution have slightly effect on the particle size. ► The size control could be interpreted in terms of the adsorption of the surfactant.

  7. Influence of the deposition techniques on the quality of the epitaxial buffer layers on textured Ni substrates

    In order to fabricate high temperature superconducting tapes for power applications, the authors have analyzed different buffer layer architectures grown on textured Ni substrates suitable for YBCO deposition. Due to its optimal lattice matching the studied structures present as top layer a CeO2 film. The deposition of CeO2 on Ni substrates was performed by pulsed laser ablation and by e-beam evaporation at different temperatures. The films obtained by the two deposition techniques have not optimal structural properties, having a polycrystalline component. The misorientation of CeO2 is probably due to the formation of NiO at the interface between the film and the substrate during the deposition process even if no oxygen is introduced. In order to prevent Ni oxidation an intermediate 2000 angstrom Pd thick film was deposited by e-beam. Furthermore, the lattice mismatch between Pd and CeO2 is smaller than that between Ni and CeO2. The Pd layer inhibits nickel oxide formation and improves the CeO2 epitaxial growth: the XRD pattern contains only the (001) peaks of Pd and CeO2. SEM analysis on CeO2/Pd/Ni shows a smooth surface free of cracks, contrary to that observed for CeO2/Ni structure

  8. Ultraviolet spectra of CeO2 nano-particles

    Full text: Quantum size effect is generally expected in nanometer size materials. The effect has been observed in many metal clusters and semiconducting nano-particles, but seldom in oxides, because the size control of crystalline oxides is generally difficult due to the ionic bond character. CeO2 (ceria) is one of the rare-earth oxides and the size effect is worth studying from the viewpoint of an ultraviolet (u.v.) spectroscopy and applications. This report describes the first observation of a blue shift of u.v. spectra in ceria nano-particles of 2-5 nm in diameter with its deviation within 20%. A ceria aqueous sol (pH ≅ 2.5) having particle sizes under 6 nm in diameter was produced by ultrafiltration with a polyether sulfone membrane (SIP-1013, Asahi Chemical Industry Co.) from an original ceria aqueous sol (pH ≅ 1.5) having particle sizes extending over a wide range. Obtained sol contains a high concentration of Ce3+ ions because of the high acidity. In order to separate ceria particles from Ce3+ ions and fractionate the particle size, two kinds of anion-type surfactants were used in microemulsification process with toluene and water. One is sodium dodecylbenzene sulfonate (SD-BS) which is 2 nm in length and another is sodium octyl sulfonate (SOS) which is 1.2 nm in length. U.v. spectroscopic measurements and high resolution transmission electron microscopic (HRTEM) observations were performed for (SOS)t , (SOS+SOS)t , and (SDBS+SOS+SDBS)t , where (SOS)t is a ceria suspension in toluene obtained by an emulsification with SOS surfactant, (SOS+SOS)t indicates the same product obtained by the further emulsification with SOS for an aqueous phase of the emulsion with SOS, and (SDBS+SOS+SDBS)t means that obtained by an additional emulsification with SDBS for an aqueous phase obtained by two successive emulsifications with SDBS and SOS. Optical density data for (SOS)t , (SOS+SOS)t , and (SDBS+SOS+SDBS)t show absorption edges at 4076 Angstroms, 3997 Angstroms, and 3921 Angstroms, respectively. A computer analysis of HRTEM images for (SOS)t , (SOS+SOS)t , and (SDBS+SOS+SDBS)t indicates the size distribution of ceria particles 3.90 ± 0.77 nm, 2.76 ± 0.59 nm, and 2.19 ± 0.37 nm, respectively. These results reveal a blue shift of the absorption edge with decreasing particle sizes and may provide information on the complicated orbital characters and valencies of rare-earth oxides. We are investigating now the cause of the blue shift

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

    Zafar, Ammar


    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.

  10. Anisotropic thermopower of the antiferromagnetic Kondo semiconductor CeOs2Al10 doped with 5d electrons and holes

    The thermopower S and electrical resistivity ρ of Ce(Os1−xIrx)2Al10 and Ce(Os1−yRey)2Al10 single crystals have been measured to understand the properties of the unusual antiferromagnetic order at TN = 28.5 K in the orthorhombic Kondo semiconductor CeOs2Al10. Opening of a gap in the hybridized band of CeOs2Al10 manifests in the activation-type increase of ρ(T) along the principal axes on cooling below 60 K, whereby Sa(T) and Sc(T) exhibit shallow minima. Below TN, Sa(T) and Sc(T) jump by a few µV/K, whereas Sb(T) sharply decreases from 30 to −7 µV/K, suggesting a loss of a part of the Fermi surface of the hybridized band. The large maximum in Sb(T) between 100 and 40 K is suddenly suppressed by doping 5d electrons and holes at a few % level. With further doping of 5d electrons and holes, respectively, the hybridization gap behaviors of both S(T) and ρ(T) change to those of metallic Kondo system and valence fluctuating system. (author)

  11. Fabrication and properties of epitaxial buffer layers on nonmagnetic textured Ni based alloy substrates

    Biaxially aligned YBCO thick films on oxide buffered metallic substrates is a promising route toward the fabrication of superconducting tapes operating at liquid nitrogen temperature. The role of buffer layer is to reduce the lattice mismatch between the substrate and the YBCO film, to adapt the thermal expansion coefficient, to hamper the diffusion of Ni in YBCO film and to prevent the oxidation of the metallic substrate surface. This paper presents a study regarding CeO2 buffer layer deposition on a new nonmagnetic (001)[100] textured Ni-V alloy substrates. The deposition of CeO2 was performed by both pulsed laser ablation and e-beam evaporation techniques. The θ-2θ X-ray diffraction pattern mainly exhibits the (00 ell) peaks of CeO2, indicating that the films are epitaxially grown with the c axis perpendicular to the substrate. Rocking curves through the CeO2 (002) peak have a FWHM of about 6 degree. The SEM studies have shown that the surface is smooth, continuous and free of cracks. Texture analysis reveals a good in-plane orientation for the ablated CeO2 film, whereas the electron beam evaporated CeO2 shows two textures in the growth plane. Further efforts are focused on the deposition of YBCO thick film on the as buffered nonmagnetic metallic substrate

  12. CeO2-covered nanofiber for highly efficient removal of phosphorus from aqueous solution.

    Ko, Young Gun; Do, Taegu; Chun, Youngsang; Kim, Choong Hyun; Choi, Ung Su; Kim, Jae-Yong


    The lowering phosphorus concentration of lakes or rivers using adsorbents has been considered to be the most effective way to prevent water eutrophication. However, the development of an adsorbent is still challenging because conventional adsorbents have not shown a sufficient phosphorus adsorption capacity (0.3-2.0mmol/g) to treat industrial, agricultural or domestic wastewater at a large scale. Herein, a novel and effective strategy to remove phosphorus efficiently with a CeO2-covered nanofiber is shown. The CeO2-covered nanofiber was synthesized through (1) amine group immobilization onto an electrospun polyacrylonitrile nanofiber and (2) adsorption of Ce(3+) on it. The CeO2-covered nanofiber played a role in catching phosphate ions in an aqueous solution by the oxidation, reduction, and ion-exchange of adsorbed Ce(3+) on the nanofiber from CeO2 to CePO4, and enabled remarkable phosphate adsorption capacity of the nanofiber (ca. 17.0mmol/g) at the range of ca. pH 2-6. Our strategy might be the most feasible method to efficiently lower the phosphorus concentration in lakes or rivers owing to the easy and inexpensive preparation of CeO2-covered nanofiber at an industrial scale, with a high phosphate adsorption capacity. PMID:26795705

  13. Facet-Controlled CeO2 Nanocrystals for Oxidative Coupling of Methane.

    Sun, Yongnan; Shen, Yue; Song, Jianjun; Ba, Rongbin; Huang, Shuangshuang; Zhao, Yonghui; Zhang, Jun; Sun, Yuhan; Zhu, Yan


    Whether the catalysts of the high temperature reaction such methane oxidation coupling has a structure-sensitive catalytic behavior or not, it is discussed and confirmed the shape-specific impact on methane activity by designing the catalysts with different crystal facets exposed. CeO2 nanowires enclosed by {110} and {100} planes show the higher CH4 conversion and higher C2 hydrocarbons (C2H4 and C2H6) selectivity, compared with particle CeO2 rounded by {111} and {100} planes, suggesting that CeO2 (110) surface favors the activation of CH4. Encouraged by the result, to control facet-controlled synthesis of catalysts for tailoring the catalytic properties at high temperature, the CeO2 (110) surface is chosen as doped sites to form the doped catalyst such as Ca doped CeO2 nanowires for OCM reaction, enhancing C2 hydrocarbons selectivity dramatically and suppressing the deep oxidation product (CO and CO2) selectivity. PMID:27483809

  14. Effect of samarium doping on electrodeposited CeO2 thin film

    Samarium-doped cerium oxide (CeO2:Sm) and undoped cerium oxide (CeO2) thin films were fabricated by electrodeposition on biaxially textured Ni-3% W substrates. The electrodeposited layers were annealed for several hours at temperatures ranging from 910 to 980 C. The resulting crystalline films were investigated by XRD and SEM. The CeO2 crystallite size was correlated to the formation of microcrack in CeO2 and CeO2:Sm using the Scherrer equation of XRD analysis. Crack-free films with an average grain size of about 28 nm were obtained for both Ce0.92Sm0.08O2-δ and Ce0.8Sm0.2O2-δ films. Sm doping strongly affects the crystallite size, crystal structure, texture, and crack formation in ceria films. The lattice parameter a increases and crystallite size is reduced with increased Sm doping. All electrodeposited films are highly biaxially textured. When compared to Ni-based substrates, improvements in the out-of-plane and in-plane texture in ceria- and Sm-doped ceria films were achieved. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Flowerlike CeO2 microspheres coated with Sr2Fe1.5Mo0.5Ox nanoparticles for an advanced fuel cell

    Liu, Yanyan; Tang, Yongfu; Ma, Zhaohui; Singh, Manish; He, Yunjuan; Dong, Wenjing; Sun, Chunwen; Zhu, Bin


    Flowerlike CeO2 coated with Sr2Fe1.5Mo0.5Ox (Sr-Fe-Mo-oxide) nanoparticles exhibits enhanced conductivity at low temperatures (300-600 oC), e.g. 0.12 S cm-1 at 600 oC, this is comparable to pure ceria (0.1 S cm-1 at 800 oC). Advanced single layer fuel cell was constructed using the flowerlike CeO2/Sr-Fe-Mo-oxide layer attached to a Ni-foam layer coated with the conducting transition metal oxide. Such fuel cell has yielded a peak power density of 802 mWcm-2 at 550 oC. The mechanism of enhanced conductivity and cell performance were analyzed. These results provide a promising strategy for developing advanced low-temperature SOFCs.

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

    Rodrigo F. Silva


    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%.

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

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


    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.

  18. Enhanced infrared emissivity of CeO2 coatings by La doping

    Pure CeO2 and La doped CeO2 (LDC) coatings were prepared on nickel-based substrates by electron beam physical vapor deposition at 1173 K. The infrared emissivity in 2.5–25 μm of LDC coatings was enhanced with the increase of La concentration at high temperature 873–1273 K. Compared to the undoped CeO2 coating, the infrared emissivity of 16.7% LDC coating increases by 55%, and reaches up to 0.9 at 873 K. The enhancement of doped coatings’ emissivity is attributed to the increasing lattice absorption and free-carrier absorption. The high emissivity LDC coatings show a promising potential in high temperature application.

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

    Ruishu Shang


    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.

  20. Preparation and Characterization of Graphite Powder Covered with CeO2


    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.

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


    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.

  2. The redox behaviour of CuO-ZrO2-CeO2 mixed oxides catalysts

    The redox behavior of CuO-ZrO2-CeO2 mixed oxide catalysts has been studied. It is found that the composition of the mixed oxides and thermal treatment could affect the reducibility of the samples, and that reduced CuO-ZrO2-CeO2 mixed oxides are oxidised easily. The experimental results also show that there is strong interaction between CuO and CeO2-ZrO2 mixed oxide, and that the interaction promotes both the reduction of CuO and CeO2 in mixed oxides as well as the catalytic activity for CO oxidation. (author)

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

    刘坚; 赵震; 徐春明; 段爱军; 姜桂元


    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...

  4. Effects of sintering on Y2O3-doped CeO2

    M. Tavafoghi Jahromi


    Full Text Available Purpose: Having high electrical conductivity, Y2O3-doped CeO2 is a good candidate for various high temperature electrochemical devices, such as solid oxide fuel cells and oxygen gas sensor. However, its inferior mechanical properties compared to its competitors, e.g. ZrO2-based electrolytes, has restricted its usage.Design/methodology/approach: The present work evaluates the sintering behavior and mechanical properties of CeO2, and aims to enhance the mechanical properties and sinterability while restricting the grain growth by doping with Y2O3.Findings: The relative density, rather than the Y2O3 concentration, was the most important factor that affected the mechanical properties of CeO2. Increase of density resulted in higher hardness and elastic modulus, and lower the fracture toughness of CeO2. In the optimum condition, the KIC of 5.1 MPa.m1/2, nanohardness of 13.0 GPa, and elastic modulus of 371.5 GPa were obtained for the undoped CeO2 (density = 98.00% sintered at 1700°C.Research limitations/implications: This study does not include sintering at higher temperatures. It is also worth investigating formation of oxygen vacancy or Ce2O3 material in the Y2O3-doped CeO2.Practical implications: It is noteworthy that in this study, the high temperature calcination of mixed powders is avoided in order to keep yitria as a second phase (not as a solute in the ceria matrix. This enables yitria to be more effective to suppress the grain growth.Originality/value: The objectives are to improve the mechanical properties and to reveal the effects of various parameters, such as density, grain size, and yitria doping on the nano/micro indentation behavior of ceria material.

  5. Effect of CeO2 addition on electrical and optical properties of lithium borate glasses

    Rare earth (RE) ions play an important role in modern technology as an active ion in many optical materials. RE-doped glasses were used in many optical devices because of abundant number of the absorption and emission bands arising from the transitions between the RE elements energy levels. Among all rare earth, glasses containing CeO2 are extensively studied for scintillating applications. Radiation length of CeO2 containing lithium silicate glasses decreases and absorption edge in transmittance shift towards longer wavelength. In the present study an attempt has been made to verify similar results in borate containing glasses. Therefore glass series 15Li2O-xCeO2-(85''x)B2O3 where x= 0.25, 0.5, 0.75, 1 mol% was prepared by conventional melt quench technique. Their electrical and optical properties have been investigated. It is observed that the conductivity of these glasses decreases while density, glass transition temperature and refractive index increases with the addition of CeO2. The conductivity of the glasses is mostly controlled by the activation energy. Since the lithium fraction in the present series is kept constant, the decrease in conductivity for glasses may be attributed to the reduction in the number of available vacant sites for the mobile lithium ions when boron is substituted with CeO2. The radiation length was determined using density values and it was found to decrease with the addition of CeO2. The absorption coefficient a were determined near the absorption edge of different photon energy for all glass samples and plot of (αhν)1/2 Vs. hν (Tauc's plot) is shown. It is observed that the optical band gap energy (EgOpt) decreases with the addition of CeO2

  6. Effects of sintering on Y2O3-doped CeO2

    M. Tavafoghi Jahromi; M.J. Tan


    Purpose: Having high electrical conductivity, Y2O3-doped CeO2 is a good candidate for various high temperature electrochemical devices, such as solid oxide fuel cells and oxygen gas sensor. However, its inferior mechanical properties compared to its competitors, e.g. ZrO2-based electrolytes, has restricted its usage.Design/methodology/approach: The present work evaluates the sintering behavior and mechanical properties of CeO2, and aims to enhance the mechanical properties and sinterability w...


    Livia Vittori Antisari; Serena Carbone; Alberto Fabrizi; Antonietta Gatti; Gilmo Vianello


    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 i...

  8. CeO2-stabilized tetragonal ZrO2 polycrystals (Ce-TZP ceramics)

    This work presents the development and the characterization of CeO2-stabilized tetragonal ZrO2 polycrystals (Ce-TZP ceramics), since it is considered candidate material for applications as structural high performance ceramics. Sintered ceramics were fabricated from mixtures of powders containing different CeO2 content prepared by conventional and nonconventional techniques. These powders and their resultant sintered ceramics were specified by chemical and physical characterization, compactation state and mechanical properties. The chemical characteristics were determined by chemical analysis and the physical characteristics were evaluated by phase content, particle and agglomerate size and aspect, and powder porosity. (author)

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

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


    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. PMID:27475371

  10. Fabrication of Y1-xRE xBa2Cu3O y films on single crystalline substrates and IBAD buffered metallic tapes by advanced TFA-MOD process

    We fabricated Y1-xSm xBa2Cu3O y and YSm xBa2Cu3O y (YSmBCO) films on SrTiO3 (STO) single crystalline substrates and IBAD buffered metallic tapes (PLD-CeO2/IBAD-GZO/Hastelloy) by the advanced TFA-MOD process by mixing TFA salts of Y, Sm, Ba and Cu naphthenate, and tried to improve the superconductivity properties compared with those of the pure YBa2Cu3O7-δ (YBCO). As a result, J c values of Y1-xSm xBa2Cu3O y films with x = 0.05 or 0.3, which were fabricated on STO substrates, were improved under the high magnetic fields compared with those of the YBCO without substitution. However, Sm segregation was detected near the STO substrate which was obtained by the TEM-EDS (transmission electron microscopy-energy-dispersive X-ray spectroscopy) analysis. On the other hand, Y1-xSm xBa2Cu3O y films with x = 0.05 and YSm xBa2Cu3O y films with x = 0.3, which were fabricated on IBAD buffered metallic substrates, also improved I c value under the high magnetic fields compared with those of the YBCO without substitution. Moreover, from the TEM-EDS analysis, Y or Sm segregation was not found. The difference in the Sm segregation behavior between the film on STO and CeO2 buffered substrates could be explained by the difference in the ratios of the misfit parameters between YBCO/substrate and SmBCO/substrate. Additionally, it was considered that the above phenomenon might be unique in the MOD system and could not be observed in the PLD system, because of the difference in the crystal growth mechanism. In the film of YSm0.3Ba2Cu3O y, we observed the grains of (Y, Sm)2O3 and (Y, Sm)2Cu2O5 by TEM observation. We will further investigate the origin of pinning centers

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

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


    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.

  12. Magnetic manipulation by resistance switching in CeO2/PrBa2Cu3O7−δ/Pt heterostructure: The role of oxygen vacancies

    Pronounced bipolar resistance switching with a good retention property has been observed in CeO2/PrBa2Cu3O7−δ/Pt heterostructure. The low resistance state and high resistance state exhibited distinguished ferromagnetic signals, as compared to the nearly non-magnetic initial state. It is found that the migration of the oxygen vacancies under electric field is mainly responsible for the electric and the magnetic changes. The modified interfacial electronic structure by the oxygen vacancy migration and the trapping/detrapping of the carriers leads to the resistance switching. The exchange interaction of the hydrogen-like orbitals formed around the singly occupied oxygen vacancies in CeO2 is accounting for the emerged and modulated ferromagnetic signals. Temperature dependence of resistance in the low resistance state follows a variable range hopping law, further confirming that the amount of oxygen vacancies in the CeO2 layer directly affects the hydrogen-like orbital radius, which determines the strength of the ferromagnetic coupling

  13. 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

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


    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 on the...

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


    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.

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

    牟广宇; 魏清莲; 黄永民


    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.

  16. Ag nanocrystals anchored CeO2/graphene nanocomposite for enhanced supercapacitor applications

    Highlights: • Quasi spherical Ag and CeO2 nanoparticles were decorated on rGO matrix. • The Ag/CeO2/rGO nanocomposite exhibits specific capacitance of 710 F g−1. • Ag plays an imperative role in improving the electrochemical performance. - Abstract: A novel ternary Ag decorated CeO2/reduced graphene oxide (rGO) nanocomposite was synthesized by a facile hydrothermal method with polyvinylpyrrolidone (PVP) as surface directing agent and was designed as an electrode material for supercapacitors application. The structure and morphology of the nanocomposites were analyzed by X-ray diffraction analysis (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The synergistic effect between the CeO2 nanoparticles wrapped rGO matrix with Ag nanoparticles gives rise to a nanostructure, empowering the material with enhanced electrochemical performance. The electrochemical characterization was performed using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopic studies in 3 M KOH aqueous electrolyte. The nanocomposite electrode materials possess a high specific capacitance of 710.42 F g−1 at an applied current density of 0.2 A g−1, which was nearly two fold higher than CeO2/rGO nanocomposite. This work endows a new route for building Ag/CeO2/rGO ternary nanocomposite which will have some impact on the exploitation of novel ternary electrode materials for supercapacitor applications

  17. Characterization of thin CeO2 films electrochemically deposited on HOPG

    Graphical abstract: - Highlights: • Preparation of proton exchange membrane fuel cells catalyst using electrochemical thin film deposition. • Electrodeposition thin films of CeO2 on HOPG substrates. • The samples were characterized by in-situ AFM and ex-situ XPS. • XPS results reveal that the electrochemically deposited cerium oxide films are stoichiometric. • Exposing the films to ambient air, cracking structures are formed. - Abstract: Electrodeposition is widely used for industrial applications to deposit thin films, coatings, and adhesion layers. Herein, CeO2 thin films were deposited on a highly oriented pyrolytic graphite (HOPG) substrate by cathodic electrodeposition. The influence of the deposition parameters on the yield and on the film morphology is studied and discussed. Morphology and composition of the electrodeposited films were characterized by in-situ atomic force microscopy (AFM), scanning electron microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). By AFM we show that the thickness of CeO2 films can be controlled via the Ce3+ concentration in solution and the deposition time. After exposing the films to ambient air, cracking structures are formed, which were analyzed by AFM in detail. The chemical composition of the deposits was analyzed by XPS indicating the formation of nearly stoichiometric CeO2

  18. Enhanced spectral emissivity of CeO2 coating with cauliflower-like microstructure

    Highlights: ► Cauliflower-like microstructured CeO2 coating is prepared on Ni based substrate. ► The infrared emissive property at high temperature is investigated. ► Rough CeO2 coating shows high emissivity, that is, 0.9 at 873 K and 0.87 at 1073 K. ► The emissivity enhancement mechanisms for the rough CeO2 coating are discussed. - Abstract: Cerium dioxide is a transparent oxide with high refractive index (from 1.6 to 2.5 at 633 nm) in the visible and near-IR spectral regions. However, little attention has been paid to its optical property in mid-IR (2.5–25 μm). Here we report that the cauliflower-like microstructured CeO2 coating deposited by electron beam physical vapor deposition technique shows high emissivity up to 0.9 at 873 K in the mid-IR spectral region. The high emissivity is attributed to the coupling between free propagating waves and space-variant polarizations caused by the cauliflower-like microstructure. This high emissivity coating shows a potential application in high temperature components.

  19. Long-term aging of a CeO2 based nanocomposite used for wood protection

    A multi-scale methodology was used to characterize the long-term behavior and chemical stability of a CeO2-based nanocomposite used as UV filter in wood stains. ATR-FTIR and 13C NMR demonstrated that the citrate coated chelates with Ce(IV) through its central carboxyl- and its α-hydroxyl- groups at the surface of the unaged nanocomposite. After 42 days under artificial daylight, the citrate completely disappeared and small amount of degradation products remained attached to the surface even after 112 days. Moreover, the release/desorption of the citrate layer led to a surface reorganization of the nano-sized CeO2 core observed by XANES (Ce L3-edge). Such a surface and structural transformation of the commercialized nanocomposite could have implications in term of fate, transport, and potential impacts towards the environment. - Highlights: • Organic coating of the nano-composite is degradated after 1.5 month. • Structural reorganization of the nano-sized CeO2 core over aging. • Potential implications in term of exposure and impact towards biological organisms. - The long-term aging of a CeO2 nanocomposite lead to surface chemistry and structural changes in aquatic environments

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

    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. Daylight photocatalysis performance of biomorphic CeO2 hollow fibers prepared with lens cleaning paper as biotemplate

    Highlights: ► A novel, simple and eco-friendly approach for hierarchical, biomorphic CeO2 hollow fibers with mesoporous tube walls is presented by using paper as template. ► The biomorphic CeO2 fibers was composed of nanosheets with bimodal pore-size mesoporous distribution and exhibited high light-harvesting under sunlight irradiation. ► The CeO2 microfibers biomimicking the natural plant structures have promising application for photodegradation of organic pollutants in water. -- Abstract: Hierarchical, biomorphic CeO2 hollow fibers with mesoporous tube walls have been fabricated using lens cleaning paper as biotemplates. After sintered at 550 °C in air, the cellulosic fibers of paper were converted into micro-tubes composing of CeO2 crystallites with grain size about 8 nm. The photocatalytic activity of the CeO2 fibers was evaluated by photodegradation efficiency of methylene blue in aqueous solution under daylight irradiation. The characterized results show that the CeO2 fibers faithfully replicated micro-fibrous structure derived from original template and possessed dramatic enhanced photocatalytic activity compared with bulk CeO2. This simple biotemplate method provides a cost-effective and eco-friendly route to obtain high performance photocatalysts.

  2. Graphite oxide-mediated synthesis of porous CeO2 quadrangular prisms and their high-efficiency adsorptive performance

    Graphical abstract: - Highlights: • Porous CeO2 quadrangular prisms have been prepared via graphite oxide-mediated synthesis. • Dual-pore hierarchical systems are formed with the pore distributions around 4 nm and 30 nm. • Porous CeO2 exhibits a rapid adsorption to Rhodamine B with a removal efficiency of ∼99%. • Porous CeO2 retains the same performances in different pH solutions. - Abstract: We report a graphite oxide-mediated approach for synthesizing porous CeO2 through a facile hydrothermal process followed by thermal annealing in air. The phase structure, morphology, microstructure and porosity of the products have been revealed by a combination of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N2 adsorption. The as-prepared CeO2 products show well-defined quadrangular prism morphology, and they are composed of interconnected nanoparticles with diameters around 30–100 nm. In particular, the dual-pore hierarchical systems are created in the CeO2 quadrangular prisms with the pore distributions around 4 nm and 30 nm. The dye sorption capacity of the porous CeO2 is investigated, which exhibits a rapid adsorption to rhodamine B with a high removal efficiency of ∼99%. Moreover, the CeO2 absorbent retains the same performances in different pH solutions

  3. Degradation reduction of polymer electrolyte membranes using CeO2 as a free-radical scavenger in catalyst layer

    Highlights: • CeO2 was added to the electrode to improve the chemical stability of the membrane. • The durability of the MEAs with CeO2 in cathode and anode was compared. • Accelerated durability tests, gas crossover and SEM were conducted. -- Abstract: Ceria nanoparticles were added to the electrodes of proton exchange membrane fuel cells as free-radical scavengers to minimize the degradation of membrane electrode assembly (MEA) components. Accelerated durability tests were performed at low humidity under open circuit voltage (OCV) conditions, and the results were compared with traditional MEAs without CeO2. Gas crossover was monitored during the durability test, and the MEAs were examined by SEM before and after the durability test. The results showed that adding CeO2 as free-radical scavengers to the electrode greatly improves the chemical stability of the membrane. The degradation rate of the MEA with CeO2 in the anode was similar to that of the MEA with CeO2 in the cathode. The fuel cell with CeO2 in the cathode showed better MEA performance that the fuel cell with CeO2 in the anode

  4. Design of the speedup buffer for the single-flux-quantum network switch

    We have designed a speedup buffer (SB) that is indispensable for realizing a high-throughput network switch based on single-flux-quantum (SFQ) technology. The SB performs the rate conversion from 10 to 40 Gbps for the packet data streams fed into the Banyan switch. This approach can reduce the packet-blocking rate, resulting in an increased throughput for the network switch. The SB is composed of a 1:3 stream demultiplexer (SDMUX), three variable-bit-length shift registers (VLSRs) and a 3:1 stream multiplexer, coupled with a controller. We have successfully demonstrated the 1:3 SDMUX and the VLSR. As for the VLSR, we confirmed high-speed operation up to 55 GHz. We have also designed the SB using these components. The SB is a large-scale circuit composed of 11 663 Josephson junctions on a 3.8 x 3.8 mm2 area. So far, partial operations have been demonstrated experimentally

  5. Surface status and reduction behavior of porous ceria (CeO2) via amended EISA method

    Highlights: • Multi-scale porous CeO2 can be synthesized by EISA method using P123 as the template. • Step-by-step reduction is found through deconvolving the TPR curves. • Calcinations the precursor to at least 600 °C can obtain CeO2 with clean surface. - Abstract: Ceria (CeO2) powder with multi-scale porosity was synthesized by evaporation induced self-assembly (EISA) strategy using tri-block copolymer (P123) as the template. The product was characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), and N2 adsorption–desorption isotherms. Reducing property and repeatability were tested by temperature programmed H2 reduction (TPR). Oxygen storage capacity (OSC) was calculated according to the Gaussian–Lorentz deconvolving to the TPR curves. The results showed that the product possessed multi-scale porosity, sizes of the pores were in the ranges of ∼40 μm, ∼2 μm and <0.3 μm, respectively. Specific surface area of the porous CeO2 was 32.5 m2/g. Mechanism in the reduction of surface, near surface and inner parts of porous CeO2 were discussed. Carbonate groups remained on the surface when CeO2 were calcined below 600 °C. The initial H2-TPR yielded an OSC of 383 mol O2/g, which was attributed to oxygen release from the surface nanocrystals, (near) surface sites as well as the inner parts. While the repeated tests showed an OSC of 418 mol O2/g, which was associated with the diminished reaction before 620 °C and the enhanced reduction around 782 °C. A schematic was proposed for the preparation of CeO2 with multi-scale porosity in the amended EISA strategy, based on the characterization results, and the strategy may provide a candidate to obtain catalyst with excellent properties

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

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


    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.

  7. Crack growth resistance of Al2O3-ZrO2(nano (12 mol% CeO2 ceramics

    M. Szutkowska


    a single edge notched beam (SENB enabled measurement of the R-curve. In presented work a new load-relaxation method was worked out for determination susceptibility tested ceramics to slow crack growth.

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

    Shi Hong Zhang et al


    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 unde...

  9. Effect of annealing temperature on oxygen vacancy concentrations of nanocrystalline CeO2 film

    Highlights: • Nanocrystalline CeO2 films were prepared by a facile sol–gel spin coating method. • Oxygen vacancy concentrations can be controlled by annealing temperatures. • The films show perfect thermal stability at various annealing temperatures. • PL, XPS and Raman spectra are obviously affected by oxygen vacancy concentrations. - Abstract: Nanocrystalline CeO2 films with around 250 nm thickness were deposited on Si (0 0 1) substrates by a facile sol–gel process with spin coating method. The films are of cubic fluorite structure, and some lattice distortions exist in the film. The phase stability and small change in lattice parameter at different annealing temperatures indicate the good thermal stability of the nanocrystalline CeO2 films. The average grain-size and surface roughness of the films increase with the increase of annealing temperature. The content of Ce3+ and oxygen vacancy is very high in the nanocrystalline CeO2 films, while, the films still remain cubic phase regardless of its high level non-stoichiometric composition. All the annealed samples show two emission bands, and the defect peak centered at ∼500 nm shows a red-shift. The intensity of the green-emission band increases with the increasing annealing temperature, which might result from the increasing concentration of oxygen vacancies caused by the valence transition from Ce4+ to Ce3+, and it has also been confirmed by the X-ray photoelectron spectroscopy results. This work demonstrates that oxygen vacancy plays an important role on the properties of the nanocrystalline CeO2 film, and it also provides a possible way to control the concentration of oxygen vacancies

  10. Preparation and characterization of α-Fe2O3-CeO2 composite

    In our previous study we attempted to see the effect of cerium doping (Ce/Fe ratio 0.015 to 0.074) on goethite matrix and conversion of doped goethite to hematite. In the present communication, nano-structured α-Fe2O3-CeO2 composite with Fe/Ce weight ratio as 1.1 has been synthesized by calcination of goethite-cerium hydroxide precursor prepared by co-precipitation method. It was observed that co-precipitation of cerium along with iron in hydroxide medium resulted in hindering the formation of crystalline order as the precursor formed showed poorly crystallized goethite and almost no crystallinity in Ce(OH)4. Calcination of the precursor at 400 deg. C showed the formation of hematite together with a broad peak corresponding to cerium oxide whereas at 800 deg. C, two distinct phases of α-Fe2O3 and CeO2 were observed. The Moessbauer spectra showed the presence of a paramagnetic component both for the precursor as well as for the sample calcined at 400 deg. C but on raising the calcination temperature to 800 deg. C, the paramagnetic component disappeared and the spectrum corresponding to pure α-Fe2O3 phase was observed. The microstructure of the product obtained by calcining at 800 deg. C showed rod like structure (30 to 50 nm width and 300 to 500 nm length) of α-Fe2O3 having equi-dimensional CeO2 particles on and around the surface. Besides the rods, equi-dimensional particles and agglomerates corresponding to CeO2 were also observed. The results show that co-precipitation followed by calcinations gives nanorods hematite with CeO2 particles bonded to its surface

  11. A comparison of different lysis buffers to assess allele dropout from single cells for preimplantation genetic diagnosis.

    Thornhill, A R; McGrath, J A; Eady, R A; Braude, P R; Handyside, A H


    Single cell polymerase chain reaction (PCR) for preimplantation genetic diagnosis (PGD) requires high efficiency and accuracy. Allele dropout (ADO), the random amplification failure of one of the two parental alleles, remains the most significant problem in PCR-based PGD testing since it can result in serious misdiagnosis for compound heterozygous or autosomal dominant conditions. A number of different strategies (including the use of lysis buffers to break down the cell and make the DNA accessible) have been employed to combat ADO with varying degrees of success, yet there is still no consensus among PGD centres over which lysis buffer should be used (ESHRE PGD Consortium, 1999). To address this issue, PCR amplification of three genes (CFTR, LAMA3 and PKP1) at different chromosomal loci was investigated. Single lymphocytes from individuals heterozygous for mutations within each of the three genes were collected and lysed in either alkaline lysis buffer (ALB) or proteinase K/SDS lysis buffer (PK). PCR amplification efficiencies were comparable between alkaline lysis and proteinase K lysis for PCR products spanning each of the three mutated loci (DeltaF508 in CFTR 90% vs 88%; R650X in LAMA3 82% vs 78%; and Y71X in PKP1 91% vs 87%). While there was no appreciable difference between ADO rates between the two lysis buffers for the LAMA3 PCR product (25% vs 26%), there were significant differences in ADO rates between ALB and PK for the CFTR PCR product (0% vs 23%) and the PKP1 PCR product (8% vs 56%). Based on these results, we are currently using ALB in preference to PK/SDS buffer for the lysis of cells in clinical PGD. PMID:11438956

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

    Berton Marcos A.C.


    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.

  13. The use of buffer pellets to pseudo hot seed (RE)-Ba-Cu-O-(Ag) single grain bulk superconductors

    Shi, Yunhua; Namburi, Devendra Kumar; Zhao, Wen; Durrell, John H.; Dennis, Anthony R.; Cardwell, David A.


    Reliable seeding of the superconducting (RE)Ba2Cu3O7-δ (RE-123) phase is a critical step in the melt growth of large, single grain, (RE)BaCuO ((RE)BCO) bulk superconductors. Recent improvements to the top seeded melt growth (TSMG) processing technique, which is an established method of fabricating bulk (RE)BCO superconductors, based on the use of a buffer layer between the seed and green body preform, has significantly improved the reliability of the single grain growth process. This technique has been used successfully for the primary TSMG and infiltration melt growth of all compositions within the ((RE)BCO-Ag) family of materials (where RE = Sm, Gd and Y), and in recycling processes. However, the mechanism behind the improved reliability of the melt process is not understood fully and its effect on the superconducting properties of the fully processed single grains is not clear. In this paper, we investigate the effect of the use of a buffer pellet between the seed and green body on the microstructure, critical current, critical temperature and trapped field of the bulk superconductor. We conclude that the introduction of the buffer pellet evolves the melt growth process towards that observed in the technologically challenging hot seeding technique, but has the potential to yield high quality single grain samples but by a commercially viable melt process.

  14. Synthesis and electrochemical properties of CeO2 nanoparticle modified TiO2 nanotube arrays

    In this paper, a cerium dioxide (CeO2) modified titanium dioxide (TiO2) nanotube array film was fabricated by electrodeposition of CeO2 nanoparticles onto an anodized TiO2 nanotube array. The structural investigation by X-ray diffraction, scanning electron microscopy and transmission electron microscopy indicated that the CeO2 nanoparticles grew uniformly on the walls of the TiO2 nanotubes. The composite was composed of cubic-phase CeO2 crystallites and anatase-phase TiO2 after annealing at 450 oC. The cyclic voltammetry and chronoamperometric charge/discharge measurement results indicated that the CeO2 modification obviously increased the charge storage capacity of the TiO2 nanotubes. The charge transfer process at the surface, that is, the pseudocapacitance, was the dominate mechanism of the charge storage in CeO2-modified TiO2 nanotubes. The greater number of surface active sites resulting from uniform application of the CeO2 nanoparticles to the well-aligned TiO2 nanotubes contributed to the enhancement of the charge storage density.

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

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


    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.

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

    D. Channei


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

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


    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

  18. Resistive switching behaviour of highly epitaxial CeO2 thin film for memory application

    We report on the remarkable potential of highly epitaxial and pure (001)-oriented CeO2 thin films grown on conducting Nb-doped SrTiO3 (NSTO) substrates by laser molecular beam epitaxy for nonvolatile memory application. Resistive switching (RS) devices with the structure of Au/epi-CeO2/NSTO exhibit reversible and steady bipolar RS behaviour with large high/low resistance ratio and a narrow dispersion of the resistance values. Detailed analysis of the conduction mechanisms reveals that the trapping/detrapping processes and oxygen vacancies migration play important roles in the switching behaviour. In the light of XPS measurement results, the CeO2/NSTO interface with oxygen vacancies or defects is responsible for the RS effect. Furthermore, a model is proposed to explain this resistance switching behaviour. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Texture development of CeO2 thin films deposited by ion beam assisted deposition

    CeO2 thin films were prepared on amorphous quartz glass substrates by the ion beam assisted deposition (IBAD) technique at room temperature. In order to control both the in-plane and out-of-plane texture of the films, a special geometrical arrangement of the ion sources, the target, and the substrate was used. A new concept, considering the role of reflected particles from the target, which we call self-IBAD, was introduced. The structural properties of the CeO2 films were investigated by x-ray diffraction. Good biaxially textured films were obtained with out-of-plane mosaic spreads of 3.0 deg. and in-plane alignment of 10.8 deg. C

  20. Magnetic properties in nitrogen-doped CeO2 from first-principles calculations

    The electronic structures and magnetic properties of N-doped CeO2 crystals have been investigated by first-principles calculations based on density functional theory with and without U. The results demonstrate a magnetic moment of 1.00μB per N obtained from all schemes. Predictions based on both LSDA and GGA calculations with and without U capture a half-metallic ground state for the N-doped CeO2 system. Several doped configurations calculations within LSDA demonstrate that there exist robust ferromagnetic couplings between these local magnetic moments, which mainly stem from Hund's rule coupling. The hole-mediated long-range double exchange mechanism is responsible for the predicted ferromagnetism. It turns out that the percolation concentration needed to establish the collective ferromagnetism is at a few percent. However, further test calculations show that a weakly half-metallic ground state is predicted by GGA+U for this system.

  1. Erosion-Corrosion Property of CeO2-Modified HVOF WC-Co Coating

    Liu, Yan; Hang, Zongqiu; Chen, Hui; Ceng, Shengbo; Gou, Guoqing; Wang, Xiaomin; Tu, Mingjing; Wu, Xiangyang


    Rare-earth elements have been widely used in materials manufacturing to improve hardness and toughness. In this work, conventional, nanostructured, and CeO2-modified WC-12Co powders were sprayed using high-velocity oxygen flame spraying. The erosion-corrosion behavior and interaction of erosion and corrosion of the coatings in 3.5 wt.% NaCl solution were investigated. In situ observation was employed to analyze the failure mechanism. The results showed that the CeO2-modified WC-12Co coating possessed the best erosion-corrosion resistance, while the lowest corrosion resistance was exhibited by the conventional WC-12Co coating. The results also suggested that the erosion-corrosion mechanism in the three coatings was dominated by corrosion-accelerated erosion. However, the extent of acceleration of erosion by corrosion differed.

  2. Electrodeposition of Ni-La2O3/CeO2 nanocomposite and its catalytic applications

    Ni-La2O3/CeO2 nanocomposite film was prepared by electrodeposition method. Nanosized La2O3(20-50 nm) and CeO2 (20-50 nm) particles were dispersed into a conventional watt's nickel electrolyte bath. Electrodeposited film was characterized by SEM, EDS, XRD and AFM. The resulting film was used as a cathode for hydrogen evolution reaction and it shows better catalytic activity. Microhardness, corrosion resistance studies, and catalytic activity towards methanol oxidation were also carried out. The synergism of La2O3 and CeO2 in nickel matrix significantly enhances the catalytic activities. (author)

  3. Microwave sintering of ZrO2-12 mol% CeO2

    Sintering of ZrO2-12 mol% CeO2 was accelerated by microwave processing at 2.45 GHz as compared with conventional firing. However, the size of the ''microwave effect'' was significantly smaller than that which was previously observed for microwave sintering of ZrO2-8 mol% Y2O3. The difference in the effect that the microwave field had on the two zirconia systems is interpreted in terms of their ionic conductivities

  4. Oxygen vacancy-assisted coupling and enolization of acetaldehyde on CeO2(111).

    Calaza, Florencia C; Xu, Ye; Mullins, David R; Overbury, Steven H


    The temperature-dependent adsorption and reaction of acetaldehyde (CH(3)CHO) on a fully oxidized and a highly reduced thin-film CeO(2)(111) surface have been investigated using a combination of reflection-absorption infrared spectroscopy (RAIRS) and periodic density functional theory (DFT+U) calculations. On the fully oxidized surface, acetaldehyde adsorbs weakly through its carbonyl O interacting with a lattice Ce(4+) cation in the η(1)-O configuration. This state desorbs at 210 K without reaction. On the highly reduced surface, new vibrational signatures appear below 220 K. They are identified by RAIRS and DFT as a dimer state formed from the coupling of the carbonyl O and the acyl C of two acetaldehyde molecules. This dimer state remains up to 400 K before decomposing to produce another distinct set of vibrational signatures, which are identified as the enolate form of acetaldehyde (CH(2)CHO¯). Furthermore, the calculated activation barriers for the coupling of acetaldehyde, the decomposition of the dimer state, and the recombinative desorption of enolate and H as acetaldehyde are in good agreement with previously reported TPD results for acetaldehyde adsorbed on reduced CeO(2)(111) [Chen et al. J. Phys. Chem. C 2011, 115, 3385]. The present findings demonstrate that surface oxygen vacancies alter the reactivity of the CeO(2)(111) surface and play a crucial role in stabilizing and activating acetaldehyde for coupling reactions. PMID:23020248

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

    Zhao, He; Zhang, Guangming; Zhang, Quanling


    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. PMID:24369902

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

    Oman ZUAS


    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:

  7. Ferromagnetism induced by oxygen and cerium vacancies above the percolation limit in CeO2

    Fernandes, V.; Schio, P.; de Oliveira, A. J. A.; Ortiz, W. A.; Fichtner, P.; Amaral, L.; Graff, I. L.; Varalda, J.; Mattoso, N.; Schreiner, W. H.; Mosca, D. H.


    We studied the structural, chemical and magnetic properties of non-doped ceria (CeO2) thin films electrodeposited on silicon substrates. Experimental results confirm that the observed room temperature ferromagnetism is driven by both cerium and oxygen vacancies. We investigated ceria films presenting vacancy concentrations well above the percolation limit. Irradiation experiments with neon ions were employed to generate highly oxygen defective CeO2 - δ structures. X-ray photoelectron spectroscopy and x-ray absorption near-edge structure spectroscopy were used to estimate the concentration of Ce3 + sites in the films, which can reach up to 50% of Ce3 + replacing Ce4 + , compared to a stoichiometric CeO2 structure. Despite the increment of structural disorder, we observe that the saturation magnetization continuously increases with Ce3 + concentration. Our experiments demonstrate that the ferromagnetism observed in ceria thin films, highly disordered and oxygen-deficient, preserving the fluorite-type structure only in a nanometer scale, remains intrinsically stable at room temperature.

  8. Ferromagnetism induced by oxygen and cerium vacancies above the percolation limit in CeO2

    We studied the structural, chemical and magnetic properties of non-doped ceria (CeO2) thin films electrodeposited on silicon substrates. Experimental results confirm that the observed room temperature ferromagnetism is driven by both cerium and oxygen vacancies. We investigated ceria films presenting vacancy concentrations well above the percolation limit. Irradiation experiments with neon ions were employed to generate highly oxygen defective CeO2-δ structures. X-ray photoelectron spectroscopy and x-ray absorption near-edge structure spectroscopy were used to estimate the concentration of Ce3+ sites in the films, which can reach up to 50% of Ce3+ replacing Ce4+, compared to a stoichiometric CeO2 structure. Despite the increment of structural disorder, we observe that the saturation magnetization continuously increases with Ce3+ concentration. Our experiments demonstrate that the ferromagnetism observed in ceria thin films, highly disordered and oxygen-deficient, preserving the fluorite-type structure only in a nanometer scale, remains intrinsically stable at room temperature.

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

    Oman ZUAS


    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:

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

    YAN Kai; ZHEN Qiang; Song Xiwen


    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.

  11. Thermodynamic modeling of the CeO2–CoO nano-phase diagram

    Highlights: • The CeO2–CoO nano-phase diagram was modeled thermodynamically. • The surface energies of the solution phases were modeled with Butler’s equation. • The present work agreed with the experimental work on the nanoparticle sintering. -- Abstract: A nano-phase diagram of the CeO2–CoO system was modeled thermodynamically with experimental data available in the literatures. The surface energies of CeO2 and CoO unavailable in the literatures were estimated reasonably on the thermodynamic basis. Butler’s model was used to describe the surface energy and the surface composition of the solution phases and then the nano interaction parameters on the particle radius were assessed through the multiple linear regression method. A consistent set of optimized interaction parameters in the present system was derived for describing the Gibbs energy of liquid, fluorite, and halite solution phases as a function of particle radius. The eutectic temperatures calculated in the present work interpreted well the experimental data for the unusual low sintering temperature of the nanoparticles with the tri-modal particle size distribution. Furthermore, with the aid of the present result, the microstructure evolution in the CGO–CoO system during the nanoparticle sintering was described reasonably. It is concluded that the present modeling will be a good guide for the condition of the liquid phase sintering to obtain the rapid densification of the nanoparticles at lower temperatures

  12. Photocatalytic activity of mixture of ZrO2/SnO2, ZrO2/CeO2 and SnO2/CeO2 nanoparticles

    Highlights: ► The formation of tetragonal and monoclinic phases of SnO2, CeO2 and ZrO2 nanoparticles calcined at 550 °C. ► The photocatalytic activity is obtained as SnO2/ZrO2 > CeO2/ZrO2 > SnO2/CeO2 > ZrO2 > SnO2 > CeO2. ► The photocatalytic activity of mixture of ZrO2/SnO2 (4:1) > Zr0.8Sn0.2O2 nanocomposite. ► The complete degradation of 2-nitrophenol at 45 min at presence of ZrO2/SnO2 (4:1) and H2O2. - Abstract: The ZrO2, SnO2 and CeO2 nanoparticles synthesized by sol–gel procedure and calcined at 550 °C. The prepared nanoparticles characterized by X-ray diffraction spectroscopy, transmission electron microscopy and IR spectrophotometry. The structure of prepared nanoparticles were tetragonal and monoclinic as confirmed from the XRD patterns. The photocatalytic activity of ZrO2, SnO2, CeO2 nanoparticles and the mixture of 1:1 of ZrO2/SnO2, ZrO2/CeO2 and SnO2/CeO2 studied in 2-nitrophenol degradation reaction. The order of photocatalytic activity is ZrO2/SnO2 > ZrO2/CeO2 > SnO2/CeO2 > ZrO2 > SnO2 > CeO2. Among mixtures of ZrO2/SnO2, the mixture with weight ratio of 4:1 showed the highest photocatalytic activity. The results indicated the ZrO2 nanoparticles with the more band-gap energy had an important role in photocatalytic activity. The mixture of ZrO2/SnO2 (4:1) is also indicated the higher photocatalytic activity in comparison to Zr0.8Sn0.2O2 nanocomposite. The complete degradation of 2-nitrophenol was obtained at time 45 min in the presence of hydrogen peroxide (0.1 g/L) and the mixture of ZrO2/SnO2 (4:1).

  13. pH buffering of single rat skeletal muscle fibers in the in vivo environment.

    Tanaka, Yoshinori; Inagaki, Tadakatsu; Poole, David C; Kano, Yutaka


    Homeostasis of intracellular pH (pHi) has a crucial role for the maintenance of cellular function. Several membrane transporters such as lactate/H(+) cotransporter (MCT), Na(+)/H(+) exchange transporter (NHE), and Na(+)/HCO3 (-) cotransporter (NBC) are thought to contribute to pHi regulation. However, the relative importance of each of these membrane transporters to the in vivo recovery from the low pHi condition is unknown. Using an in vivo bioimaging model, we pharmacologically inhibited each transporter separately and all transporters together and then evaluated the pHi recovery profiles following imposition of a discrete H(+) challenge loaded into single muscle fibers by microinjection. The intact spinotrapezius muscle of adult male Wistar rats (n = 72) was exteriorized and loaded with the fluorescent probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein-acetoxymethyl ester (10 μM). A single muscle fiber was then loaded with low-pH solution [piperazine-N,N'-bis(2-ethanesulfonic acid) buffer, pH 6.5, ∼2.33 × 10(-3) μl] by microinjection over 3 s. The rats were divided into groups for the following treatments: 1) no inhibitor (CONT), 2) MCT inhibition (by α-Cyano-4-hydroxyciannamic acid; 4 mM), 3) NHE inhibition (by ethylisopropyl amiloride; 0.5 mM), 4) NBC inhibition (by DIDS; 1 mM), and 5) MCT, NHE, and NBC inhibition (All blockade). The fluorescence ratio (F500 nm/F445 nm) was determined from images captured during 1 min (60 images/min) and at 5, 10, 15, and 20 min after injection. The pHi at 1-2 s after injection significantly decreased from resting pHi (ΔpHi = -0.73 ± 0.03) in CONT. The recovery response profile was biphasic, with an initial rapid and close-to-exponential pHi increase (time constant, τ: 60.0 ± 7.9 s). This initial rapid profile was not affected by any pharmacological blockade but was significantly delayed by carbonic anhydrase inhibition. In contrast, the secondary, more gradual, return toward baseline that restored CONT pHi to


    Livia Vittori Antisari


    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.

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

    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

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

    Shi Hong Zhang et al


    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.

  17. Integration of atomic layer deposition CeO2 thin films with functional complex oxides and 3D patterns

    We present a low-temperature, < 300 °C, ex-situ integration of atomic layer deposition (ALD) ultrathin CeO2 layers (3 to 5 unit cells) with chemical solution deposited La0.7Sr0.3MnO3 (LSMO) functional complex oxides for multilayer growth without jeopardizing the morphology, microstructure and physical properties of the functional oxide layer. We have also extended this procedure to pulsed laser deposited YBa2Cu3O7 (YBCO) thin films. Scanning force microscopy, X-ray diffraction, aberration corrected scanning transmission electron microscopy and macroscopic magnetic measurements were used to evaluate the quality of the perovskite films before and after the ALD process. By means of microcontact printing and ALD we have prepared CeO2 patterns using an ozone-robust photoresist that will avoid the use of hazardous lithography processes directly on the device components. These bilayers, CeO2/LSMO and CeO2/YBCO, are foreseen to have special interest for resistive switching phenomena in resistive random-access memory. - Highlights: • Integration of atomic layer deposition (ALD) CeO2 layers on functional complex oxides • Resistive switching is identified in CeO2/La0.7Sr0.3MnO3 and CeO2/YBa2Cu3O7 bilayers. • Study of the robustness of organic polymers for area-selective ALD • Combination of ALD and micro-contact printing to obtain 3D patterns of CeO2

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

    Brown, R. D.


    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.

  19. Microstructure and thermal cycling behavior of CeO2 coatings deposited by the electron beam physical vapor technique

    Excellent thermal shock resistance is required for thermal protection coatings experiencing high/low temperature cycles. In this paper, the pure ceria oxide coatings were deposited by electron beam physical vapor technique at different power densities. The grain orientation, morphology, hardness and thermal cycling oxidation behavior of CeO2 coatings were systematically studied. The deposition power density has remarkable influence on the preferred crystal orientation and morphology of the coatings. The heating–cooling test cycles from 1000 °C to room temperature indicate that the CeO2 coatings with the columnar structure show excellent thermal shock resistance. The hardness of the CeO2 coating varies with thermal cycling. - Highlights: • Electron-beam physical vapor deposited CeO2 coatings show preferred orientation. • Surface morphology of CeO2 coatings is deeply influenced by the deposition power. • CeO2 coatings with columnar structure exhibit excellent thermal shock resistance. • The hardness increases initially and then decreases during thermal cycling

  20. CTAB assisted hydrothermal synthesis, controlled conversion and CO oxidation properties of CeO2 nanoplates, nanotubes, and nanorods

    In this work, CeO2 nanoplates were synthesized by a hydrothermal reaction assisted by hexadecyltrimethylammonium bromide (CTAB) at 100-160 deg. C. The size of nanoplates was around 40 nm. Further experiment showed that the controlled conversion of nanoplates into nanotubes, and nanorods can be realized by changing the reaction time, temperature, and CTAB/Ce3+ ratio value. X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption measurements were employed to characterize the samples. The CO oxidation properties of nanorods, nanoplates, and nanotubes were investigated. An enhanced catalytic activity has been found for CO oxidation by using CeO2 nanoplates as compared with CeO2 nanotubes and nanorods, and the crystal surfaces (100) of CeO2 nanoplates were considered to play an important role in determining their catalytic oxidation properties. - Graphical abstract: CeO2 nanoplates were synthesized by hydrothermal reactions assisted by CTAB, and the controlled conversion of nanoplates into nanotubes, and nanorods were realized by changing the CTAB/Ce3+ ratio value, reaction time, and temperature. An excellent catalytic activity is found for CO oxidation using CeO2 nanoplates due to their exposed surface (100)

  1. Synthesis of mesoporous Bi2O3/CeO2 microsphere for photocatalytic degradation of Orange II dye

    Graphical abstract: - Highlights: • Bi2O3/CeO2 microspheres were successfully synthesized by a hydrothermal procedure. • Bi2O3/CeO2 microspheres were used to remove wastewater pollutant containing azo dye. • The activity of Bi2O3/CeO2 is synergically enhanced compared to its pristine forms. - Abstract: We report on the visible-light responsive porous assembly of Bi2O3/CeO2 microspheres, which were synthesized via a simple hydrothermal reaction between Bi(NO3)3·5H2O and Ce(NO3)3·6H2O in the presence of ethylene glycol and ethanol. Systematic structural (X-ray diffraction (XRD)), morphological (field emission scanning electron microscopy (FE-SEM) and transmission electron microscopic (TEM)), BET surface area and diffuse reflectance spectral (DRS) analyses were carried out to characterize the formed product. The effects of experimental parameters on the microstructural and morphological behavior of Bi2O3/CeO2 composites were discussed. The semiconductor material as obtained was evaluated as a heterogeneous photocatalyst for the photolytic degradation of an azo dye in water and the degradation was found to follow pseudo-first-order rate kinetics. The study compares the rate constants of the new hybrid catalyst to a pristine Bi2O3 and CeO2, which has excellent catalytic properties under visible light irradiation for the degradation of Orange II dye

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

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


    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.

  3. O/W/O double emulsion-assisted synthesis and catalytic properties of CeO 2 hollow microspheres

    Zhang, DongEn; Xie, Qing; Wang, MingYan; Zhang, XiaoBo; Li, ShanZhong; Han, GuiQuan; Ying, AiLing; Chen, AiMei; Gong, JunYan; Tong, ZhiWei


    CeO 2 hollow microspheres have been fabricated through a simple thermal decomposition of precursor approach. The precursor with an average size of 10 μm was prepared in a reverse microemulsions containing Ce(NO 3) 3·6H 2O and CO(NH 2) 2 at 160 °C. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), selected area electron diffraction (SAED) and scanning electron microscopy (SEM). The possible formation mechanism of hollow spheres was discussed. In addition, the CeO 2 hollow microspheres modified glassy carbon electrode exhibit excellent sensing performance towards methyl orange, which provide a new application of CeO 2 hollow spheres. The catalytic activity of CeO 2 hollow spheres on the thermal decomposition of ammonium perchlorate (AP) also was investigated by TGA. The catalytic performance of CeO 2 hollow spheres is superior to that of commercial CeO 2 powder.

  4. Simultaneous removal of elemental mercury and NO from flue gas by V2O5-CeO2/TiO2 catalysts

    Zhang, Xunan; Li, Caiting; Zhao, Lingkui; Zhang, Jie; Zeng, Guangming; Xie, Yin'e.; Yu, Ming'e.


    A series of Ce-doped V2O5/TiO2 catalysts synthesized by an ultrasound assisted impregnation method were employed to investigate simultaneous removal of elemental mercury (Hg0) and NO in lab-scale experiments. Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffractogram (XRD), and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize the samples. Compared to TiO2 support, the catalytic performance of CeO2 doped on both TiO2 and V2O5/TiO2 catalysts have been improved. Remarkably, 1%V2O5-10% CeO2/TiO2 (V1Ce10Ti) exhibited the highest Hg0 oxidation efficiency of 81.55% at 250 °C with a desired NO removal efficiency under the same condition. Both the NO conversion and Hg0 oxidation efficiency were enhanced in the presence of O2. The activity was inhibited by the injection of NH3 with the increase of NH3/NO. When in the presence of 400 ppm SO2, Hg0 oxidation was slightly affected. Furthermore, Hg0 removal behavior under both oxidation and selective catalytic reduction (SCR) condition over V1Ce10Ti were well investigated to further probe into the feasibility of one single unit for multi-pollutants control in industry application. The existence of the redox cycle of V4+ + Ce4+ ↔ V5+ + Ce3+ in V2O5-CeO2/TiO2 catalyst could not only greatly improve the NO conversion, but also promote the oxidation of Hg0.

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

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


    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. PMID:24956769

  6. Potential rare-earth modified CeO2 catalysts for soot oxidation. Part 2. Characterisation and catalytic activity with NO + O2

    Ceria (CeO2) and rare-earth modified ceria (CeReOx with Re = La3+, Pr3+/4+, Sm3+, Y3+) supports and Pt impregnated supports are studied for the soot oxidation under a loose contact with the catalyst with the feed gas, containing NO + O2. The catalysts are characterised by XRD, H2-TPR, DRIFT and Raman spectroscopy. Among the single component oxides, CeO2 is significantly more active compared with the other lanthanide oxides used in this study. Doping CeO2 with Pr3+/4+ and La3+ improved, however, the soot oxidation activity of the resulting solid solutions. This improvement is correlated with the surface area in the case of CeLaOx and to the surface area and redox properties of CePrOx catalyst. The NO conversion to NO2 over these catalysts is responsible for the soot oxidation activity. If the activity per unit surface area is compared CePrOx is the most active one. This indicates that though La3+ can stabilise the surface area of the catalyst in fact it decreases the soot oxidation activity of Ce4+. The lattice oxygen participates in NO conversion to NO2 and the rate of this lattice oxygen transfer is much faster on CePrOx. In general, the improvement of the soot oxidation is observed over the Pt impregnated CeO2 and CeReOx catalysts, and can be correlated to the presence of Pt . The surface reduction of the supports in the presence of Pt occurred below 100 C. The surface redox properties of the support in the Pt catalysts do not have a significant role in the NO to NO2 conversion. In spite of the lower surface area, the Pt/CeYOx and Pt/CeO2 catalysts are found to be more active due to larger Pt crystal sizes. The presence of Pt also improved the CO conversion to CO2 over these catalysts. The activation energy for the soot oxidation with NO + O2 is found to be around 50 kJ/mol. (author)

  7. Structure, bonding, and catalytic activity of monodisperse, transition-metal-substituted CeO2 nanoparticles.

    Elias, Joseph S; Risch, Marcel; Giordano, Livia; Mansour, Azzam N; Shao-Horn, Yang


    We present a simple and generalizable synthetic route toward phase-pure, monodisperse transition-metal-substituted ceria nanoparticles (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni, Cu). The solution-based pyrolysis of a series of heterobimetallic Schiff base complexes ensures a rigorous control of the size, morphology and composition of 3 nm M0.1Ce0.9O2-x crystallites for CO oxidation catalysis and other applications. X-ray absorption spectroscopy confirms the dispersion of aliovalent (M(3+) and M(2+)) transition metal ions into the ceria matrix without the formation of any bulk transition metal oxide phases, while steady-state CO oxidation catalysis reveals an order of magnitude increase in catalytic activity with copper substitution. Density functional calculations of model slabs of these compounds confirm the stabilization of M(3+) and M(2+) in the lattice of CeO2. These results highlight the role of the host CeO2 lattice in stabilizing high oxidation states of aliovalent transition metal dopants that ordinarily would be intractable, such as Cu(3+), as well as demonstrating a rational approach to catalyst design. The current work demonstrates, for the first time, a generalizable approach for the preparation of transition-metal-substituted CeO2 for a broad range of transition metals with unparalleled synthetic control and illustrates that Cu(3+) is implicated in the mechanism for CO oxidation on CuO-CeO2 catalysts. PMID:25406101

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

    Chunjie Wang; Aihua Zhang; Hamid Reza Karimi


    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 in...

  9. Interface-engineered resistive switching: CeO(2) nanocubes as high-performance memory cells.

    Younis, Adnan; Chu, Dewei; Mihail, Ionsecu; Li, Sean


    We reported a novel and facile approach to fabricate self-assembled CeO2 nanocube-based resistive-switching memory device. The device was found to exhibit excellent bipolar resistive-switching characteristics with a high resistance state (HRS/OFF) to low resistance state (LRS/ON) ratio of 10(4), better uniformity, and stability up to 480 K. The presence of oxygen vacancies and their role was discussed to explain the resistive-switching phenomenon in the fabricated devices. Further, the effect of the film thickness on carrier concentrations and estimated electric field strength with the switching (OFF/ON) ratio were also discussed. PMID:24028707

  10. Defect and transport properties of nanocrystalline CeO2-x

    It is shown that unique defect thermodynamics and transport properties result for oxides of a few nanometers crystallite size. Fully-dense CeO2-x polycrystals of ∼10 nm grain size were synthesized, and their electrical properties compared with those of samples coarsened from the same material. The nanocrystals showed reduced grain boundary resistance, 104 higher electronic conductivity, and less than one-half the heat of reduction of its coarse-grained counterpart. These properties are attributed to a dominant role of interfacial defect formation. copyright 1996 American Institute of Physics

  11. Theory of multiplet structure in 4d core photoabsorption spectra of CeO2

    Detailed analysis of 4d core x-ray photoabsorption spectra (4d-XAS) in CeO2 is made with the impurity Anderson model by incorporating the solid-state effect of hybridization between 4f and valence-band states into the atomic calculation of multiplet structures. The hybridization effect plays an essential role in the multiplet structure observed in the prethreshold region of 4d-XAS. The effect of the finite width of the valence band, as well as that of the core-hole potential, is discussed. The multiplet structures in α- and γ-Ce are also calculated for the sake of comparison


    JERÔNIMO, Carlos Enrique de Medeiros; FERNANDES, Hermano Gomes; SOUSA, João Fernandes


    The search for alternatives for the treatment of industrial effluents, especially high toxicity is one of the main difficulties of the industrial treatment systems. This work aims to use potassium as a promoter of electrons for the oxidation to the catalyst by impregnating it MnO2/CeO2 to degrade the effluent coming from the processing of cashew nuts in the presence of oxygen. The experiments were performed in a slurry bed reactor. In the experiments were kept constant initial concentratio...

  13. Photoluminescent properties of Eu3+ doped electrospun CeO2 nanofibers

    Fang, Dong; Zhang, Min; Luo, Zhiping; Cao, Tingting; Wang, Qing; Zhou, Zhi; Jiang, Ming; Xiong, Chuanxi


    In this study, CeO2 nanofibers and that doped with Eu3+ were prepared via a facile electrospinning route and annealed at different temperatures ranging from 500 to 900 °C. Their structures were investigated using X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Photoluminescence properties of the nanofibers were studied in detail. It was found that the nanofibers with Eu% concentration of 0.67 mol.% and annealed at 700 °C exhibited the highest intensities of the luminescence peaks between 550 and 650 nm.

  14. Study of Crystal Defect Behaviors in CeO2-Based Electrolyte

    Ma Zhifang; Liang Guangchuan; Liang Jinsheng


    The defect behaviors, such as fundamental point defect, defect pair formation and oxygen vacancy migration in ceria, were studied on the basis of energy minimization calculations. The result shows that anion Frenkel disorder is the preferred intrinsic disorder, and it is easier to be dissolved in CeO2 for CaO and SrO than for MgO and BaO via an oxygen vacancy compensation mechanism. The association energy of an oxygen vacancy with a substitutional cation depends on dopant cation radius. The favorable migration route for oxygen vacancy with the lowest migration energy is from the second neighbor site to another one.

  15. Thermodynamic modeling of the CeO2-CoO phase diagram

    A thermodynamic modeling of the CeO2-CoO phase diagram was performed with recent experimental data. The excess Gibbs energies of the solution phases were described on the basis of the simple regular solution. A consistent set of optimized interaction parameters was derived for describing the Gibbs energy of each phase in this system leading to a good fit between calculation and experimental data. The liquidus, solidus, and solvus curves were calculated and also the lattice stabilities of the components were evaluated

  16. Structural characterization and photocatalytic behaviors of doped CeO2 nanoparticles

    Ceria nanoparticles doped by different transition metals were prepared by the reverse coprecipitation method via the reaction of Ce(NO3)3 aqueous solution, where different metal cation was dissolved, to NH3.H2O aqueous solution. The doped ceria nanoparticles were sythesized and characterized using X-ray diffraction, transmission electron microscopy, Fourier transformation infrared spectroscopy, ultraviolet and visible spectroscopy. It was found that the doped ceria nanoparticles with transition metals could apparently shift the ultraviolet and visible absorption band of CeO2 towards a visible range and significantly improve their optical activity.

  17. Sorption of Cd(II) on CeO2 Resin and Its Solvent-Elution Pattern

    Capability of CeO2 resin as chemical separator component and its immobilization potential to cadmium can be exploited for utilization of the resin in the separation of Cd-In matrices. The separation of Cd-In matrices is important for improving and mastering production technology of 111/115m In using high-enriched 112/114 Cd targets. The phenomena on the sorption of Cd(11) on CeO2 resin and its solvent elution pattern were studied using CeO2 synthesized from reaction between Ce(SO4)2 and NH4OH. A series of Cd(11) standard solution was treated with the activated resin in the both static and dynamic systems. The Cd(11) content of the solution after the treatment was the determined by UV-spectrophotometry for measuring Cd (11)-sorption capacity. The solvent elution pattern was observed by fractional elution from CeO2 column followed by UV-spectrophotometric determination to the fractions giving positive test for Cd(11). It was found that the treatment of the resin with 10% NH4OH solution increases the Cd(11)-sorption capacity of the resin compared to the treatment with water or 1M HCI solution. A sharp elution patter with quantitative yield of Cd(11) recovery (more than 94%) was found by elution using 5, 10 or 20% NH4OH solution. Key words : CeO2 resin, hydrous cerium oxide, radioisotope 111/115m In, separation of Cd-In matrices, sorption of Cd(11) on CeO2 resin , elution profile of Cd(11) on CeO2 resin, Cd(11) measurement by means of UV spectrophotometry

  18. Sub-solidus phase equilibria in the CeO2-ThO2-ZrO2 system

    The phase relations in the CeO2-ThO2-ZrO2 system have been established after slowly cooling the samples from 1400 deg. C. Ceria has been used as a surrogate material in place of plutonia. The various phase boundaries were delineated by refining the powder XRD data. Thoria and ceria were shown to form an ideal solid solution in the complete homogeneity range. About 5 and 20 mol.% of zirconia can be dissolved, under the heating conditions used in the present investigations, in the lattice of thoria and ceria, respectively. In the ZrO2-Th0.5Ce0.5O2 system, 10 mol.% zirconia was found to get incorporated in the lattice of Th0.5Ce0.5O2. The (Th0.5Zr0.5)1-xCexO2 system shows the formation of single-phase solid solutions from x≥0.70. Thorium rich compositions in (Ce0.5Zr0.5)1-xThxO2 system were also found to be cubic solid solution. In addition, a number of other phases like t-ZrO2, various two-phase and multi-phase regions could also be identified in this pseudo-ternary system

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

    Isabel van Driessche


    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.

  20. Portable Enzyme-Paper Biosensors Based on Redox-Active CeO2 Nanoparticles.

    Karimi, A; Othman, A; Andreescu, S


    Portable, nanoparticle (NP)-enhanced enzyme sensors have emerged as powerful devices for qualitative and quantitative analysis of a variety of analytes for biomedicine, environmental applications, and pharmaceutical fields. This chapter describes a method for the fabrication of a portable, paper-based, inexpensive, robust enzyme biosensor for the detection of substrates of oxidase enzymes. The method utilizes redox-active NPs of cerium oxide (CeO2) as a sensing platform which produces color in response to H2O2 generated by the action of oxidase enzymes on their corresponding substrates. This avoids the use of peroxidases which are routinely used in conjunction with glucose oxidase. The CeO2 particles serve dual roles, as high surface area supports to anchor high loadings of the enzyme as well as a color generation reagent, and the particles are recycled multiple times for the reuse of the biosensor. These sensors are small, light, disposable, inexpensive, and they can be mass produced by standard, low-cost printing methods. All reagents needed for the analysis are embedded within the paper matrix, and sensors stored over extended periods of time without performance loss. This novel sensor is a general platform for the in-field detection of analytes that are substrates for oxidase enzymes in clinical, food, and environmental samples. PMID:27112400

  1. Clustering of Oxygen Vacancies at CeO2(111): Critical Role of Hydroxyls.

    Wu, Xin-Ping; Gong, Xue-Qing


    By performing density functional theory calculations corrected by an on site Coulomb interaction, we find that the defects at the CeO_{2}(111) surface observed by the scanning tunneling microscopy (STM) measurements of Esch et al. [Science 309, 752 (2005)] are not mere oxygen vacancies or fluorine impurities as suggested by Kullgren et al. [Phys. Rev. Lett. 112, 156102 (2014)], but actually the hydroxyl-vacancy combined species. Specifically, we show that hydroxyls play a critical role in the formation and propagation of oxygen vacancy clusters (VCs). In the presence of neighboring hydroxyls, the thermodynamically unstable VCs can be significantly stabilized, and the behaviors of oxygen vacancies become largely consistent with the STM observations. In addition to the clarification of the long term controversy on the surface defect structures of CeO_{2}(111), the "hydroxyl-vacancy model" proposed in this work emphasizes the coexistence of hydroxyls and oxygen vacancies, especially VCs, which is important for understanding the catalytic and other physicochemical properties of reducible metal oxides. PMID:26967428

  2. Combustion synthesis of nanocrystalline ceria (CeO2) powders by a dry route

    In this study, ceria (CeO2) powders were synthesized with 50 g per batch via a combustion technique using two kinds of starting materials-urea [(NH2)2CO] (as a fuel) and ceric ammonium nitrate [Ce(NH4)2(NO3)6] (acting as both the source of cerium ion and an oxidizer). The starting materials were mixed thoroughly without adding water, and then ignited in the air at room temperature. It underwent a self-combustion process with a large amount of smoke, a voluminous loose product. The as-synthesized powders were characterized by X-ray diffraction (XRD) analysis, transmission electron microscope (TEM), scanning electron microscope (SEM), CHN elemental analyzer, surface area measurements, and sinterability. Experimental results revealed that the nanocrystalline CeO2 powders with low impurity content (2/g and ∼25 nm, respectively, through the stoichiometric fuel/oxidizer ratio reaction. The powder, when cold pressed and sintered in the air at 1250 deg. C for 1 h, was measured to attain the sintered density ∼92% of theoretical density having submicron grain size. In addition, the thermal decomposition and combustion process of the reactant mixture were investigated using thermogravimetry (TG), differential scanning calorimetry (DSC), and mass spectrometry (MS) techniques simultaneously. Based on the results of thermal analysis, a possible mechanism concerning the combustion reaction is proposed

  3. Synthesis of morphology-controllable mesoporous Co3O4 and CeO2

    Recently, extensive works have been devoted to the morphology control of mesoporous materials with respect to their use in various applications. In this paper, we used two kinds of mesoporous silica, SBA-15 rods and spheres as hard templates to synthesize morphology-controllable mesoporous metal oxides. By carefully controlling the loading of metal precursors in the mesopores of the hard template, mesoporous Co3O4 and CeO2 with different morphologies, such as micrometer-sized rod, hollow sphere, saucer-like sphere, and solid sphere were conveniently obtained. The structural properties of these materials were characterized by XRD, BET, SEM and TEM. In addition, it is found that the differences observed in the textural properties of the two mesoporous metal oxides nanocasted from the same template can be attributed to the properties of metal precursors and the interaction between metal oxide and SiO2. Thus-obtained mesoporous metal oxides with such special morphologies may have a potential application in the field of environmental catalytic oxidation. - Graphical Abstract: Mesoporous Co3O4 and CeO2 with different morphologies, such as micrometer-sized rod, hollow sphere, saucer-like sphere, and solid sphere were synthesized by nanocasting.

  4. Surface potentials of (111), (110) and (100) oriented CeO2-x thin films

    Wardenga, Hans F.; Klein, Andreas


    Differently oriented CeO2 thin films were prepared by radio frequency magnetron sputter deposition from a nominally undoped CeO2 target. (111), (110) and (100) oriented films were achieved by deposition onto Al2O3(0001)/Pt(111), MgO(110)/Pt(110) and SrTiO3:Nb(100) substrates, respectively. Epitaxial growth is verified using X-ray diffraction analysis. The films were analyzed by in situ photoelectron spectroscopy to determine the ionization potential, work function, Fermi level position and Ce3+ concentration at the surface in dependence of crystal orientation, deposition conditions and post-deposition treatment in reducing and oxidizing atmosphere. We observed a very high variation of the work function and ionization potential of more than 2 eV for all surface orientations, while the Fermi level varies by only 0.3 eV within the energy gap. The work function generally decreases with increasing Ce3+ surface concentration but comparatively high Ce3+ concentrations remain even after strongly oxidizing treatments. This is related to the presence of subsurface oxygen vacancies.

  5. Simulation and experimental study of rheological properties of CeO2-water nanofluid

    Loya, Adil; Stair, Jacqueline L.; Ren, Guogang


    Metal oxide nanoparticles offer great merits over controlling rheological, thermal, chemical and physical properties of solutions. The effectiveness of a nanoparticle to modify the properties of a fluid depends on its diffusive properties with respect to the fluid. In this study, rheological properties of aqueous fluids (i.e. water) were enhanced with the addition of CeO2 nanoparticles. This study was characterized by the outcomes of simulation and experimental results of nanofluids. The movement of nanoparticles in the fluidic media was simulated by a large-scale molecular thermal dynamic program (i.e. LAMMPS). The COMPASS force field was employed with smoothed particle hydrodynamic potential (SPH) and discrete particle dynamics potential (DPD). However, this study develops the understanding of how the rheological properties are affected due to the addition of nanoparticles in a fluid and the way DPD and SPH can be used for accurately estimating the rheological properties with Brownian effect. The rheological results of the simulation were confirmed by the convergence of the stress autocorrelation function, whereas experimental properties were measured using a rheometer. These rheological values of simulation were obtained and agreed within 5 % of the experimental values; they were identified and treated with a number of iterations and experimental tests. The results of the experiment and simulation show that 10 % CeO2 nanoparticles dispersion in water has a viscosity of 2.0-3.3 mPas.

  6. Electrical and microstructural properties of Yb-doped CeO2

    B. Matović


    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.

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

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


    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.

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

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


    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.

  9. Microstructure and fatigue behaviors of a biomedical Ti–Nb–Ta–Zr alloy with trace CeO2 additions

    The new β-type Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy containing trace amounts of CeO2 additions has been designed as a biomedical implant with improved fatigue properties achieved by keeping Young's modulus to a low value. The results show that the microstructure is refined by the addition of CeO2; the β grain size becomes a little larger when Ce content increases from 0.05% to 0.10%. This occurs because dispersed CeO2 particles can act as nucleation sites for β grains; thus, the effect of rare earth oxides on microstructure refinement mainly depends on the size and dispersion of the rare earth oxides. Young's moduli of TNTZ with CeO2 additions are maintained as low as those of TNTZ without CeO2, while the fatigue limit is highly improved. The 0.10% Ce alloy exhibits the best fatigue strength among the experimental alloys; its fatigue strength is increased by 66.7% compared to that of pure TNTZ. The mechanism by which rare earth oxides affect fatigue performance is dominated by dispersion strengthening. The stiff rare earth oxides can hinder the movement of dislocations, resulting in resistance to the formation of fatigue cracks. Rare earth oxides also change the crack propagation direction and the crack propagation route, effectively decreasing the crack propagation rate

  10. Slow light enhanced near infrared luminescence in CeO2: Er3+, Yb3+ inverse opal photonic crystals

    Highlights: • CeO2: Er3+, Yb3+ photonic crystals was prepared. • Near infrared emission in the CeO2: Er3+, Yb3+ inverse opal was obtained. • Near infrared emission was enhanced by slow light effect of photonic crystals. - Abstract: The surface plasmon resonances of metal nanoparticles and energy transfer between rare earth ions were used widely to enhance the near infrared emission of rare earth ions. In this paper, a new method for near infrared emission enhancement of rare-earth is reported. The CeO2: Er3+, Yb3+ inverse opals with the photonic band gaps at the 500 and 450 nm were prepared by using polystyrene colloidal crystal as templates, and their near infrared emission properties were investigated. The results show that the near infrared emission property of the CeO2: Er3+, Yb3+ inverse opals depends on the overlapped extend between the excited light and photonic band gap. The near infrared emission located at the 1540 nm of the CeO2: Er3+, Yb3+ inverse opals have been enhanced obviously when the wavelength of the excitation light overlapped with photonic band gaps edge, which is attributed to the slow light effect of photonic crystals. The enhancement of near infrared emission may be important for the development of infrared laser and amplifiers for optical communication

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

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


    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. PMID:23352517

  12. Near-infrared luminescence of Tm3+-doped CeO2 films based on silicon substrates

    CeO2/Tm2O3 multilayer films were deposited on silicon substrates by electron-beam evaporation. Tm3+ ions were doped in CeO2 after the films were annealed in oxygen atmosphere at 1000 C. The doping concentration of Tm3+ varies in the range of 0.1-3 mol%. A series of near-infrared emission peaks were observed under the excitation of 330 nm, which correspond to 1G4-3H5, 3H4-3H6, 1G4-3H4, 3H5-3H6, 3F2-3H5, 3H4-3F4, 1G4-3F3,2 and 3F4-3H6 transitions of Tm3+, respectively. The dominant transition of 3H4-3H6 near 805 nm was within optical transmission window. The luminescence properties and the crystal structure of CeO2:Tm3+ films were investigated by excitation and emission spectroscopy and X-ray diffraction. Meanwhile, the substitution process of Ce4+ by Tm3+ was illustrated, and lattice expansion of the matrix CeO2 gave rise to the increase in FWHM of CeO2 diffraction peaks. In addition, the effect of Tm3+ concentration on photoluminescence was also studied, and the optimal concentration of Tm3+ was 0.5 mol%. (orig.)

  13. Exploration of CeO2 nanoparticles as a chemi-sensor and photo-catalyst for environmental applications

    CeO2 nanoparticles were synthesized hydrothermally and utilized as redox mediator for the fabrication of efficient ethanol chemi-sensor. The developed chemi-sensor showed an excellent performance for electrocatalytic oxidization of ethanol by exhibiting higher sensitivity (0.92 μA·cm-2·mM-1) and lower limit of detection (0.124 ± 0.010 mM) with the linear dynamic range of 0.17 mM-0.17 M. CeO2 nanoparticles have been characterized by field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), Raman spectrum, Fourier transform infrared spectroscopy (FTIR), and UV-visible absorption spectrum which revealed that the synthesized CeO2 is an aggregated form of optically active spherical nanoparticles with the range of 15-36 nm (average size of ∼ 25 ±10 nm) and possessing well crystalline cubic phase. Additionally, CeO2 performed well as a photo-catalyst by degrading amido black and acridine orange. - Research highlights: → CeO2 nanoparticles. → Sensitive ethanol chemi-sensor. → Efficient photo-catalyst. → Degradation of environmental pollutant. → Environmental safety.

  14. Aggregation kinetics of CeO2 nanoparticles in KCl and CaCl2 solutions: measurements and modeling

    To characterize the environmental transport and health risks of CeO2 nanoparticles (NPs), it is important to understand their aggregation behavior. This study investigates the aggregation kinetics of CeO2 NPs in KCl and CaCl2 solutions using time-resolved dynamic light scattering (TR-DLS). The initial hydrodynamic radius of CeO2 NPs measured by DLS was approximately 95 nm. Attachment efficiencies were derived both from aggregation data and predictions based on the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The deviations of the DLVO predictions were corrected by employing the extended DLVO (EDLVO) theory. The critical coagulation concentration (CCC) of CeO2 NPs at pH = 5.6 is approximately 34 mM for KCl and 9.5 mM for CaCl2. Furthermore, based on the EDLVO theory and the von Smoluchowski’s population balance equation, a model accounting for diffusion-limited aggregation (DLA) kinetics was established. For the reaction-limited aggregation (RLA) kinetics, a model that takes fractal geometry into account was established. The models fitted the experimental data well and proved to be useful for predicting the aggregation kinetics of CeO2 NPs.

  15. Different synthesis protocols for Co3O4 -CeO2 catalysts--part 1: influence on the morphology on the nanoscale.

    Yang, Jingxia; Lukashuk, Liliana; Akbarzadeh, Johanna; Stöger-Pollach, Michael; Peterlik, Herwig; Föttinger, Karin; Rupprechter, Günther; Schubert, Ulrich


    Co3 O4 -modified CeO2 (Co/Ce 1:4) was prepared by a combination of sol-gel processing and solvothermal treatment. The distribution of Co was controlled by means of the synthesis protocol to yield three different morphologies, namely, Co3 O4 nanoparticles located on the surface of CeO2 particles, coexistent Co3 O4 and CeO2 nanoparticles, or Co oxide structures homogeneously distributed within CeO2 . The effect of the different morphologies on the properties of Co3 O4 -CeO2 was investigated with regard to the crystallite phase(s), particle size, surface area, and catalytic activity for CO oxidation. The material with Co3 O4 nanoparticles finely dispersed on the surface of CeO2 particles had the highest catalytic activity. PMID:25384333

  16. Anolyte recirculation effects in buffered and unbuffered single-chamber air-cathode microbial fuel cells.

    Zhang, Liang; Zhu, Xun; Kashima, Hiroyuki; Li, Jun; Ye, Ding-ding; Liao, Qiang; Regan, John M


    Two identical microbial fuel cells (MFCs) with a floating air-cathode were operated under either buffered (MFC-B) or bufferless (MFC-BL) conditions to investigate anolyte recirculation effects on enhancing proton transfer. With an external resistance of 50 Ω and recirculation rate of 1.0 ml/min, MFC-BL had a 27% lower voltage (9.7% lower maximal power density) but a 64% higher Coulombic efficiency (CE) than MFC-B. MFC-B had a decreased voltage output, batch time, and CE with increasing recirculation rate resulting from more oxygen transfer into the anode. However, increasing the recirculation rate within a low range significantly enhanced proton transfer in MFC-BL, resulting in a higher voltage output, a longer batch time, and a higher CE. A further increase in recirculation rate decreased the batch time and CE of MFC-BL due to excess oxygen transfer into anode outweighing the proton-transfer benefits. The unbuffered MFC had an optimal recirculation rate of 0.35 ml/min. PMID:25514399

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

    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.

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

    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.


    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

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

    SUN Qingchi; LU Cuimin; ZHOU Hua


    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.

  20. A photoemission study of the interaction of Ga with CeO2(1 1 1) thin films

    The interaction of gallium with CeO2(1 1 1) layers was studied using standard and resonant photoelectron spectroscopy, by means of both a laboratory X-ray source and tunable synchrotron light. Firstly a 1.5-nm thick CeO2 film was grown on a Cu(1 1 1) substrate. Secondly Ga was deposited in six steps up to a thickness of 0.35 nm, at room temperature. The interaction of gallium with the oxide layer induced partial CeO2 reduction, and gallium oxidation. The photoemission data suggest that a mixed Ga-Ce-O oxide was established similarly to the Sn-Ce-O case for Sn deposited on cerium oxide layers. As a consequence, gallium-induced weakening of Ce-O bonds provides a higher number of active sites on the surface that play a major role in its catalytic behaviour

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

    Chyuan Haur Kao


    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.

  2. A study on the growth kinetics of CeO2-modified aluminide coating and its computer fitting

    A CeO2-modified aluminide coating was obtained by composite electro-deposition Ni and CeO2 particles on 20 steel with different holding time using pack cementation. The growth kinetics curve was given with computer fitting by measuring the thickness of the layer. Scanning electronic microscopy and X-ray energy dispersive spectrometry were used to analyze the microstructure and components of the layer. The results showed that the content of CeO2 was up to 5.21 wt.% in the rich area of NiAl coatings, which restrain the interdiffusion between the coating and the base during the oxidation process at high temperature. Meanwhile, the growth curve obtained could offer an important basis to forecasting and controlling the depth of the coating

  3. The effect of CeO2 support upon activity and selectivity of Ru and Co Fischer Tropsh catalysts

    Some CeO2 supported Ru and Co catalysts with 5% metal loading were prepared by impregnation methods, and characterised by temperature programmed reduction techniques (TPR). Their catalytic activities and selectivities were tested in H2 + CO reactions and compared with a Ru on SiO2 catalyst in the range of 1-9 atmospheres at 2600C. Ru/SiO2 and Co/SiO2 catalysts gave CH4 only at 1 atm., and = 70% CH4 at 9 atms., whilst CeO2 supported Ru and Co gave significantly smaller quantities (20-80%) of CH4 over the same pressure range

  4. Highly Enhanced Concentration and Stability of Reactive Ce^3+ on Doped CeO_2 Surface Revealed In Operando

    Chueh, William C.; McDaniel, Anthony H.; Grass, Michael E.; Hao, Yong; Jabeen, Naila; Liu, Zhi; Haile, Sossina M.; McCarty, Kevin F.; Bluhm, Hendrik; El Gabaly, Farid


    Trivalent cerium ions in CeO_2 are the key active species in a wide range of catalytic and electro-catalytic reactions. We employed ambient pressure X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy to quantify simultaneously the concentration of the reactive Ce^3+ species on the surface and in the bulk of Sm-doped CeO_2(100) in hundreds of millitorr of H2–H2O gas mixtures. Under relatively oxidizing conditions, when the bulk cerium is almost entirely in the 4+ oxida...

  5. Ultrasonic-induced synthesis of high surface area colloids CeO2-ZrO2

    The nanostructures of high surface area ceria-zirconia colloids have been successfully synthesized via a sonochemical method in the presence of polyethylene glycol 600. Their structural characteristics have been investigated using powder XRD, FESEM, BET surface area, TG, and other techniques. The average size of CeO2-ZrO2 nanoparticles is estimated to be 3.7 nm using Debye-Scherrer's equation. The BET analysis indicates that colloids CeO2-ZrO2 have a remarkably high surface area of 226 m2 g-1.

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

    Panpan Guan


    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.

  7. Solvothermal synthesis, electrochemical and photocatalytic properties of monodispersed CeO2 nanocubes

    Cubic-like CeO2 nanocrystals were successfully synthesized through an improved-toluene solvothermal process using hexadecylamine (HAD) as a capping agent and CeCl3.7H2O as a precursor at 180 deg. C for 24 h. These nanocubes are about 10 nm in size, and have a tendency to assemble into 2D superstructure. The obtained samples were characterized by means of X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). It was found that the water content, the concentration of ligand and kinds of aliphatic amine played important roles in the formation of the novel morphology. A possible formation mechanism was proposed based on the controlling reaction parameters. The electrochemical and photocatalytic properties of the as-synthesized samples exhibited the size/shape-dependent properties and potential applications.

  8. Crystallization and crystal growth of CeO2 under hydrothermal conditions

    This study deals with the effect of several mineralizers on the crystallization and the crystal growth of CeO2 under hydrothermal conditions. The starting material was hydrous ceria precipitate from Ce(NO3)3.6H2O solution with 3N NH4OH. The precipitate was repeatedly washed, and then dried. Distilled water or a solution of KF, LiCl, LiBr, K2CO3, LiNO3, Li2SO4 or NaOH was used as a mineralizer. The results for each mineralizer are shown as crystallite size at various temperatures, the crystallites being examined by X-ray powder diffraction and scanning electron microscopy. The results are discussed. (U.K.)

  9. Atomic structures and oxygen dynamics of CeO2 grain boundaries

    Feng, Bin; Sugiyama, Issei; Hojo, Hajime; Ohta, Hiromichi; Shibata, Naoya; Ikuhara, Yuichi


    Material performance is significantly governed by grain boundaries (GBs), a typical crystal defects inside, which often exhibit unique properties due to the structural and chemical inhomogeneity. Here, it is reported direct atomic scale evidence that oxygen vacancies formed in the GBs can modify the local surface oxygen dynamics in CeO2, a key material for fuel cells. The atomic structures and oxygen vacancy concentrations in individual GBs are obtained by electron microscopy and theoretical calculations at atomic scale. Meanwhile, local GB oxygen reduction reactivity is measured by electrochemical strain microscopy. By combining these techniques, it is demonstrated that the GB electrochemical activities are affected by the oxygen vacancy concentrations, which is, on the other hand, determined by the local structural distortions at the GB core region. These results provide critical understanding of GB properties down to atomic scale, and new perspectives on the development strategies of high performance electrochemical devices for solid oxide fuel cells.

  10. A Single-Phase Photovoltaic Inverter Topology With a Series-Connected Energy Buffer

    Pierquet, Brandon J.; Perreault, David J.


    Module integrated converters (MICs) have been under rapid development for single-phase grid-tied photovoltaic applications. The capacitive energy storage implementation for the double-line-frequency power variation represents a differentiating factor among existing designs. This paper introduces a new topology that places the energy storage block in a series-connected path with the line interface block. This design provides independent control over the capacitor voltage, soft-switching for al...

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

    Highlights: • The citric acid capping significantly reduced the ζ potential values. • As the amount of CA increased, thicker the layer surrounding the CeO2 NPs. • CeO2/CA NPs had better distribution and small particle size than bare CeO2 NPs. • CeO2/CA NPs decrease the Ce uptake by radish seedlings. -- Abstract: 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 50 mg/L, 100 mg/L, and 200 mg/L. Deionized water and CA at 100 mg/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 200 mg/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. Buffer-Gas Cooling of a Single Ion in a Multipole Radio Frequency Trap Beyond the Critical Mass Ratio

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


    We theoretically investigate the dynamics of a trapped ion immersed in a spatially localized buffer gas. For a homogeneous buffer gas, the ion's energy distribution reaches a stable equilibrium only if the mass of the buffer gas atoms is below a critical value. This limitation can be overcome by using multipole traps in combination with a spatially confined buffer gas. Using a generalized model for elastic collisions of the ion with the buffer-gas atoms, the ion's energy distribution is numerically determined for arbitrary buffer-gas distributions and trap parameters. Three regimes characterized by the respective analytic form of the ion's equilibrium energy distribution are found. Final ion temperatures down to the millikelvin regime can be achieved by adiabatically decreasing the spatial extension of the buffer gas and the effective ion trap depth (forced sympathetic cooling).

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

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


    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. PMID:26030478

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

    Ma, Lin; Tian, Hui; Yue, Zhao;


    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. On a...... microlevel, the CeO2 film epitaxially grows well on top of the Ni5W tape. A continuous, smooth, and crack-free morphology was observed on the CeO2 film and the fraction of low-angle grain boundaries (≤ 10°) is about 98 %. This process is a potential possibility for producing long-length textured CeO2/Ni5W...

  15. Enhanced photocatalytic activity of CeO2 using β-cyclodextrin on visible light assisted decoloration of methylene blue.

    Pitchaimuthu, Sakthivel; Velusamy, Ponnusamy


    An attempt has been made to enhance the photocatalytic activity of CeO(2) for visible light assisted decoloration of methylene blue (MB) dye in aqueous solutions by β-cyclodextrin (β-CD). The inclusion complexation patterns between host and guest (i.e., β-CD and MB) have been confirmed with UV-visible spectral data. The interaction between CeO(2) and β-CD has also been characterized by field emission scanning electron microscopy analysis. The photocatalytic activity of the catalyst under visible light was investigated by measuring the photodegradation of MB in aqueous solution. The effects of key operational parameters such as initial dye concentration, initial pH, CeO(2) concentration as well as illumination time on the decolorization extents were investigated. Among the processing parameters, the pH of the reaction solution played an important role in tuning the photocatalytic activity of CeO(2). The maximum photodecoloration rate was achieved at basic pH (pH 11). Under the optimum operational conditions, approximately 99.6% dye removal was achieved within 120 min. The observed results indicate that the decolorization of the MB followed a pseudo-first order kinetics. PMID:24434976

  16. CeO2 catalysed soot oxidation. The role of active oxygen to accelerate the oxidation conversion

    The influence of CeO2 in the acceleration of NOx-assisted soot oxidation has been studied in flow-reactor equipment by comparing two catalyst configurations, namely: (1) Pt upstream of soot and (2) Pt upstream of CeO2-soot. The role of CeO2 has been elucidated by means of DRIFT spectroscopy coupled with mass spectrometry and TAP reactor experiments. It was found that CeO2 has the potential to accelerate the oxidation rate of soot due to its active oxygen storage. The formation of active oxygen is initiated by NO2 in the gas phase. A synergetic effect is observed as a result of surface nitrate decomposition, which results in gas phase NO2 and desorption of active oxygen. Stored oxygen is postulated to exist in the form of surface peroxide or super oxide. Active oxygen is likely to play a role on the acceleration of soot oxidation and to contribute more than desorbed NO2 or NO2 from surface nitrate decomposition

  17. Optimization of CeO2-ZrO2 mixed oxide catalysts for ethyl acetate combustion

    Dimitrov, M.; Ivanova, R.; Štengl, Václav; Henych, Jiří; Kovacheva, D.; Tsoncheva, T.


    Roč. 47, č. 1 (2015), s. 323-329. ISSN 0324-1130 Institutional support: RVO:61388980 Keywords : nanosized CeO2-ZrO2 * mixed oxide phase * ethyl acetate combustion Subject RIV: CA - Inorganic Chemistry Impact factor: 0.201, year: 2014

  18. Co3O4-CeO2 mixed oxide-based catalytic materials for diesel soot oxidation

    Dhakad, M.; Mitshuhashi, T.; Rayalu, S.; Doggali, P.; Bakardjieva, Snejana; Šubrt, Jan; Fino, D.; Haneda, H.; Labhsetwar, N.


    Roč. 132, 1-4 (2008), s. 188-193. ISSN 0920-5861 R&D Projects: GA MŠk LC523 Institutional research plan: CEZ:AV0Z40320502 Keywords : soot oxidation * diesel particulate * Co3O4-CeO2 type mixed oxide Subject RIV: CA - Inorganic Chemistry Impact factor: 3.004, year: 2008

  19. Hydrogenated CeO2-xSx mesoporous hollow spheres for enhanced solar driven water oxidation.

    Xiao, Yuting; Chen, Yajie; Xie, Ying; Tian, Guohui; Guo, Shien; Han, Taoran; Fu, Honggang


    A facile route for the fabrication of hydrogenated sulfur-doped CeO2 (H-CeO2-xSx) mesoporous hollow spheres is reported. The spheres exhibited excellent photocatalytic activity due to the synergistic effect of the higher sulfur doping level and hydrogen post-treatment. PMID:26741276

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

    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...

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

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


    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. PMID:24266202

  2. Synergic effect of the TiO2-CeO2 nanoconjugate system on the band-gap for visible light photocatalysis

    Graphical abstract: - Highlights: • Nanostructured TiO2-CeO2 films are successfully synthesized by combining of sputtering and electrophoresis methods. • Synergic effect of CeO2 on TiO2 band gap was demonstrated, CeO2 diminishes it from 3.125 to 2.74. • Morphologic characterization of the nanoconjugate TiO2-CeO2 films by different microscopy techniques. - Abstract: The TiO2-CeO2 photocatalytic system in films is proposed here, in order to obtain photocatalytic systems that can be excited by solar light. The films were obtained through the electrophoretic deposition (EPD) of TiO2-CeO2 gel on sputtered Ti Corning glass substrates. The synergic effect of CeO2 in TiO2 films was analyzed as a function of the optical band gap reduction at different concentrations (1, 5, 10, and 15 mol%). The effect of two thermal treatments was also evaluated. The lowest band gap value was obtained for the sample with 5 mol% ceria that was thermally treated at 700 °C. The nanostructured films were characterized by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high angle annular dark field (HAADF), high resolution transmission electron microscopy (HRTEM), and atomic force microscopy (AFM). The nanocomposites were formed by TiO2 and CeO2 nanoparticles in the anatase and fluorite type phases, respectively

  3. The effects of CeO2 addition on crystallization behavior and pore size in microporous calcium titanium phosphate glass ceramics

    Highlights: ► We prepare a phosphate glass ceramic in the system of CaO–TiO2–P2O5 and add 2 to 6 mol% CeO2 to it. We determine the optimum percentage of CeO2 addition. ► We study phase separation, suitable time and temperature for crystallization in the microporous Calcium Titanium Phosphate Glass Ceramics utilizing DTA, SEM and XRD. ► We investigate on pore size utilizing BET and SEM techniques before and after CeO2 addition. ► CeO2 increases the pore size in the Calcium Titanium Phosphate Glass Ceramics. -- Abstract: In this research the effect of the addition of CeO2 to microporous Calcium Titanium Phosphate glass ceramics was studied. Different molar percentages of CeO2 were added to three samples of a base glass whose composition was P2O5 30, CaO 45, TiO2 25 (mol%). The first sample had 2 mol% CeO2, the second sample had 4 mol% CeO2, and the third sample had 6 mol% CeO2. The fourth sample did not contain any CeO2. The glass samples were melted and crystallized to bulk glass ceramics by a conventional method. Differential Thermal Analysis (DTA) was utilized to determine the appropriate nucleation and crystallization temperatures. Among the samples, the DTA curve of the sample which had 2 mol% CeO2 had the sharpest crystallization peak. Therefore, this sample was chosen to prepare the glass ceramics. Using X-ray Diffraction (XRD) it was found that in all samples β-Ca3(PO4)2 and CaTi4(PO4)6 were the major phases. The β-Ca3(PO4)2 phase was dissolved away by soaking the glass ceramics in HCl, leaving a porous skeleton of CaTi4(PO4)6. CeO2 addition increased the glass transition temperature and decreased the crystallization time and temperature. It was shown that CeO2 addition resulted in an increase in the mean pore diameter while the specific surface area decreased. The median pore diameter and specific surface area were determined as 27 nm and 14 m2/g, respectively, for the sample containing 2 mol% CeO2.

  4. Pyridine-thermal synthesis and high catalytic activity of CeO2/CuO/CNT nanocomposites

    Carbon nanotubes (CNTs) were controllably coated with the uninterrupted CuO and CeO2 composite nanoparticles by a facile pyridine-thermal method and the high catalytic performance for CO oxidation was also found. The obtained nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction as well as X-ray photoelectron spectroscopy. It is found that the CuO/CeO2 composite nanoparticles are distributed uniformly on the surface of CNTs and the shell of CeO2/CuO/CNT nanocomposites is made of nanoparticles with a diameter of 30-60 nm. The possible formation mechanism is suggest as follows: the surface of CNTs is modified by the pyridine due to the π-π conjugate role so that the alkaline of pyridine attached on the CNT surface is more enhanced as compared to the one in the bulk solvent, and thus, these pyridines accept the proton from the water molecular preferentially, which result in the formation of the OH- ions around the surface of CNTs. Subsequently, the metal ions such as Ce3+ and Cu2+ in situ react with the OH- ions and the resultant nanoparticles deposit on the surface of CNTs, and finally the CeO2/CuO/CNT nanocomposites are obtained. The T50 depicting the catalytic activity for CO oxidation over CeO2/CuO/CNT nanocomposites can reach ∼113 deg. C, which is much lower than that of CeO2/CNT or CuO/CNT nanocomposites or CNTs.

  5. Controlled fabrication and enhanced photocatalystic performance of BiVO4@CeO2 hollow microspheres for the visible-light-driven degradation of rhodamine B

    Graphical abstract: - Highlights: • m-BiVO4@CeO2 hollow microspheres were firstly fabricated. • m-BiVO4@CeO2 was used for photocatalytic degradation of rhodamine B. • The photocatalytic activity of heterogeneous hollow microspheres is enhanced. • Photocatalytic mechanism on m-BiVO4@CeO2 by visible light irradiation was proposed. • Efficient separation of photoexcited charges results in enhanced catalytic activity. - Abstract: m-BiVO4@CeO2 hollow microspheres have been fabricated by a facile low-temperature co-precipitation method and subsequent annealing process. The composition, morphology and size of the as-fabricated m-BiVO4@CeO2 hollow microspheres were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The vibrational features and the electronic state of the as-obtained m-BiVO4@CeO2 hollow microspheres were studied by Raman spectra and X-ray photoelectron spectroscopy (XPS). Band-gap energy of the as-prepared m-BiVO4@CeO2 hollow microspheres was evaluated by UV–vis spectrum. The visible-light-driven photocatalystic performances were evaluated by degradation for RhB dye molecules, demonstrating that the as-fabricated m-BiVO4@CeO2 hollow microspheres exhibit the enhanced photocatalystic activity, compared to the obtained pure m-BiVO4 microspheres. The separation of photoinduced electron–hole pairs and transfer between CeO2 and BiVO4 has been discussed in detail, in order to have in-depth understanding on the enhanced photocatalytic performance. The results indicate that the enhanced photocatalystic activity of the as-fabricated m-BiVO4@CeO2 hollow microspheres is attributed to the efficient separation of the photoexcited electrons and holes

  6. An ultrasensitive electrochemical sensor for simultaneous determination of xanthine, hypoxanthine and uric acid based on Co doped CeO2 nanoparticles.

    Lavanya, N; Sekar, C; Murugan, R; Ravi, G


    A novel electrochemical sensor has been fabricated using Co doped CeO2 nanoparticles for selective and simultaneous determination of xanthine (XA), hypoxanthine (HXA) and uric acid (UA) in a phosphate buffer solution (PBS, pH5.0) for the first time. The Co-CeO2 NPs have been prepared by microwave irradiation method and characterized by Powder XRD, Raman spectroscopy, HRTEM and VSM measurements. The electrochemical behaviours of XA, HXA and UA at the Co-CeO2 NPs modified glassy carbon electrode (GCE) were studied by cyclic voltammetry and square wave voltammetry methods. The modified electrode exhibited remarkably well-separated anodic peaks corresponding to the oxidation of XA, HXA and UA over the concentration range of 0.1-1000, 1-600 and 1-2200μM with detection limits of 0.096, 0.36, and 0.12μM (S/N=3), respectively. For simultaneous detection by synchronous change of the concentrations of XA, HXA and UA, the linear responses were in the range of 1-400μM each with the detection limits of 0.47, 0.26, and 0.43μM (S/N=3), respectively. The fabricated sensor was further applied to the detection of XA, HXA and UA in human urine samples with good selectivity and high reproducibility. PMID:27157753

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

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


    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...... epitaxially grown CeO2 buffer layer was 95 % (<10°), and the FWHM values of phi-scan and omega-scan being 6.98° and 5.92°, respectively....

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

    Uzunoglu, Aytekin; Stanciu, Lia A


    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. PMID:26851092

  9. A 1,2-propylene oxide sensor utilizing cataluminescence on CeO2 nanoparticles.

    Liu, Hongmei; Zhang, Yantu; Zhen, Yanzhong; Ma, Yuan; Zuo, Weiwei


    A simple and sensitive gas sensor was proposed for the determination of 1,2-propylene oxide (PO) based on its cataluminescence (CTL) by oxidation in the air on the surface of CeO2 nanoparticles. The luminescence characteristics and optimal conditions were investigated in detail. Under optimized conditions, the linear range of the CTL intensity versus the concentration of PO was 10-150 ppm, with a correlation coefficient (r) of 0.9974 and a limit of detection (S/N = 3) of 0.9 ppm. The relative standard deviation for 40 ppm PO was 1.2% (n = 7). There was no or only weak response to common foreign substances including acetone, formaldehyde, ethyl acetate, acetic acid, chloroform, propanol, carbon tetrachloride, ether and methanol. There was no significant change in the catalytic activity of the sensor for 100 h. The proposed method was simple and sensitive, with a potential of detecting PO in the environment and industry. PMID:24802092

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

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


    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.

  11. Biogenic synthesis and catalysis of porous CeO2 hollow microspheres

    CHEN Feng; WANG Wei; CHEN Zhigang; WANG Taibin


    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.

  12. Enhanced transport of CeO2 nanoparticles in porous media by macropores.

    Fang, Jing; Wang, Min-hao; Lin, Dao-hui; Shen, Bing


    This is the first study to investigate the effect of macropores on the transport of CeO2 nanoparticles (nCeO2) in quartz sand and soil. The artificial macropore types are the vertical continuous macropore (O-O), and the vertical discontinuous macropore (O-C). The results indicated that the mobility of nCeO2 was significantly enhanced by the macropore in both quartz sand and soil, and the enhancement was greater in the continuous macropore than in the discontinuous macropore. Compared with the homogeneous column, both the O-O and O-C macropores in quartz sand favored an earlier breakthrough and a larger initial effluent recovery rate of nCeO2. However, there was little influence on the plateau concentration and the total effluent recovery rate. In soil, both types of macropores significantly shortened nCeO2 breakthrough time, and favored a higher plateau concentration, and a larger initial and total effluent recovery rate. The O-O macropore which accounted for only 1% of the total pore volume had doubly increased the total mobility of nCeO2 in soil; even the mobility was increased by 30% with the O-C macropore. It was found that the effect of preferential flow on nCeO2 transport was greater in soil than it was in quartz sand. PMID:26584072

  13. Role of defect interaction in boundary mobility and cation diffusivity of CeO2

    Grain boundary mobility of CeO2 containing 0.1% and 1.0% trivalent dopant cations (Sc, Yb, Y, Gd, and La, in order of increasing ionic radius) has been measured. At the lower dopant concentration (intrinsic regime), mobility is controlled by grain boundary diffusion of host cations, whereas at the higher dopant concentration (extrinsic regime), mobility is controlled by solute drag through the lattice. The effect of trivalent dopants is closely associated with their ability to provide and to interact with oxygen vacancies. Evidence consistent with an interstitial mechanism for cation diffusion has been found which is remarkably affected by the presence of oxygen vacancies. Ce diffusion is enhanced by free oxygen vacancies in the system, while dopant diffusion is suppressed if a dopant-associated oxygen vacancy is not present. A bare Sc cation however, appears to be a fast-diffusing species, due to its highly distorted local environment, while Y at 1.0% emerges as the most effective grain growth suppressant

  14. Chemical composition and corrosion protection of silane films modified with CeO2 nanoparticles

    The present work aims at understanding the role of CeO2 nanoparticles (with and without activation in cerium(III) solutions) used as fillers for hybrid silane coatings applied on galvanized steel substrates. The work reports the improved corrosion protection performance of the modified silane films and discusses the chemistry of the cerium-activated nanoparticles, the mechanisms involved in the formation of the surface coatings and its corrosion inhibition ability. The anti-corrosion performance was investigated using electrochemical impedance spectroscopy (EIS), the scanning vibrating electrode technique (SVET) and d.c. potentiodynamic polarization. The chemical composition of silanised nanoparticles and the chemical changes of the silane solutions due to the presence of additives were studied using X-ray photoelectron spectroscopy (XPS) and nuclear magnetic resonance spectroscopy (NMR), respectively. The NMR and XPS data revealed that the modified silane solutions and respective coatings have enhanced cross-linking and that silane-cerium bonds are likely to occur. Electrochemical impedance spectroscopy showed that the modified coatings have improved barrier properties and the SVET measurements highlight the corrosion inhibition effect of ceria nanoparticles activated with Ce(III) ions. Potentiodynamic polarization curves demonstrate an enhanced passive domain for zinc, in the presence of nanoparticles, in solutions simulating the cathodic environment.

  15. Diffusion Barriers Block Defect Occupation on Reduced CeO_{2}(111).

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


    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 CeO_{2-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. PMID:27341245

  16. Catalytic propane reforming mechanism over Mn-Doped CeO2 (111)

    Krcha, Matthew D.; Janik, Michael J.


    MnOx/CeOx mixed oxide systems exhibit encouraging hydrocarbon oxidation activity, without the inclusion of a noble metal. Using density functional theory (DFT) methods, we examined the oxidative reforming path of propane over the Mn-doped CeO2 (1 1 1) surface. A plausible set of elementary reaction steps are identified for conversion of propane to CO/CO2 and H2/H2O over the oxide surface. The rate-limiting reaction process may vary with redox conditions, with C-H dissociation limiting under more oxidizing conditions and more complex reaction sequences, including surface re-oxidation, limiting under highly reducing conditions. The possibility of intermediate desorption from the surface during the reforming process is low, with desorption energies of the intermediates being much less favorable than further surface reactions until CO/CO2 products are formed. The reforming paths over Mn-doped ceria are similar to those previously identified over Zr-doped ceria. The extent of surface reduction and the electronic structure of the surface intermediates are examined.

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

    Jin Huiming; Zhang Linnan; Liu Xiaojun


    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.

  18. Diesel/biodiesel soot oxidation with CeO2 and CeO2-ZrO2- modified cordierites: a facile way of accounting for their catalytic ability in fuel combustion processes

    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%. (author)

  19. Properties and structure of SPEEK proton exchange membrane doped with nanometer CeO2 and treated with high magnetic field


    Full Text Available The membranes of sulfonated polyetheretherketone(SPEEK doped with rare earth metal oxide nanometer cerium oxide (CeO2 were prepared for direct methanol fuel cell (DMFC application, which was treated by parallel or perpendicular high magnetic field of 6 Teslas (T at 100°C. The proton conductivity of membrane specimens increased with temperature raised from 20 to 60°C and decreased with increasing CeO2 contents. The proton conductivity of membrane specimens under treatment with high magnetic field was better than that without treatment. The membrane specimens treated with perpendicular magnetic field demonstrated better proton conductivity than those treated with parallel magnetic field. The methanol permeation coefficient of membrane specimens decreased with increasing CeO2 contents and furthermore reduced by about 20% after treated with perpendicular high magnetic field. The water uptake of membrane specimens decreased with CeO2 doping, but would not be influenced by the magnetic field. Fourier transform infrared spectroscopy (FTIR and small-angle X-ray scattering (SAXS revealed certain reaction between oxygen anion in sulfonic groups and cerium cation in the CeO2 which dispersed evenly in the membranes but formed small conglomerates as shown by the atomic force microscopy (AFM images. X-ray diffraction (XRD proved the stability of the crystal structure of the nanometer CeO2 in polymer membranes, indicating that the reaction occurred only at the interface between SPEEK resin and CeO2 particles.

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

    Li Xingeng; Wang Xuegang; He Jiawen


    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.

  1. Electrochemical properties of Atomic layer deposition processed CeO2 as a protective layer for the molten carbonate fuel cell cathode

    Highlights: • Nano-structured CeO2-coated Ni by Atomic Layer Deposition, crystalline as-deposited. • Progressive transformation into a complex surface stable in molten carbonates. • Lower Ni solubility with CeO2 protective coating. • Feasibility of CeO2 coating in Molten Carbonate Fuel Cell cathode conditions. - Abstract: In order to increase the lifetime and performance of the molten carbonate fuel cell, it is compulsory to control the corrosion and dissolution of the state of the art porous nickel oxide cathode. A protective coating constituted by more stable oxides appears to be the best approach. Previous research on CeO2 coatings obtained by DC reactive magnetron sputtering to protect the Molten carbonate fuel cell cathode gave promising results but it was necessary to improve the coating adhesion. In this paper Atomic Layer Deposition, producing high quality, homogeneous and conformal layers, was used to obtain thin layers of CeO2 (20 nm and 120 nm) deposited over porous nickel. CeO2-Ni coated samples were tested as cathodes in Li2CO3-K2CO3 (62-38 mol %) eutectic mixture under standard cathode atmosphere (CO2/air 30:70 vol. %). Structural and morphological characterizations of the nickel coated cathode before and after electrochemical tests in the molten carbonate melt are reported together with the Open Circuit Potential evolution all over 230 h for both the bare porous nickel and the CeO2-coated samples

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

    Sumittra Charojrochkul


    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.

  3. Zn(2+)-cyclen-based complex enable a selective detection of single-stranded thymine-rich DNA in aqueous buffer.

    Zhu, Zece; Wang, Sheng; Wei, Danqing; Yang, Chuluo


    It is a big challenge to develop fluorescent probes for selective detection of DNA with specific sequences in aqueous buffers. We report a new tetraphenylethene-based Zn(2+)-cyclen complex (TPECyZn), and a chemo-sensing ensemble of the Zn complex with phenol red. TPECyZn showed significant fluorescence enhancement upon binding to thymine-rich DNA in HEPES buffers. But its selectivity was not high enough to eliminate the interference from some random DNA. By constructing the chemo-sensing ensemble of TPECyZn with phenol red, the background fluorescence was eliminated due to the energy transfer from TPECyZn to phenol red. Moreover, this chemo-sensing ensemble revealed high selectivity in detecting thymine-rich single-stranded DNA over other DNA in aqueous buffer. It can detect poly deoxythymidylic acid sequence as short as 2 nt. This detection in aqueous media makes this probe feasible in real application. PMID:27288711

  4. Combined removal of diesel soot particulates and NOx over CeO2–ZrO2 mixed oxides

    Atribak, Idriss; Bueno López, Agustín; García García, Avelina


    CeO2 and Ce–Zr mixed oxides with different Ce:Zr ratios were prepared; characterised by Raman spectroscopy, XRD, TEM, N2 adsorption at −196 ◦C, and H2-TPR; and tested for soot oxidation under NOx/O2. Among the different mixed oxides, Ce0.76Zr0.24O2 provided the best results. Ce0.76Zr0.24O2 presented greater activity than pure CeO2 for soot oxidation by NOx/O2 when both catalysts were calcined at 500 ◦C (soot oxidation rates at 500 ◦C are 14.9 and 11.4 μgsoot/s, respectively), and ...

  5. Inelastic neutron scattering studies of hydrated CuO, ZnO and CeO2 nanoparticles

    Highlights: • INS spectra of hydrated CeO2, ZnO, and CuO nanoparticles are presented. • The heat capacities for the nanoparticle hydration layers have been calculated. • The chemistry of the particles influences the thermodynamic properties of the water. - Abstract: In this contribution we demonstrate how the vibrational density of states (VDOS) for water confined to the surface of CeO2, CuO and ZnO nanoparticles can be determined from high-resolution, low-temperature, inelastic neutron scattering (INS) spectra. These VDOS have been employed in the calculation of the isochoric heat capacities (0–300 K) and room temperature vibrational entropies of the nanoparticle hydration layers. The results from this analysis clearly demonstrate that the structure and chemical composition of the metal oxide nanoparticles has a notable effect on the thermodynamic properties of their hydration layers

  6. Effect of oxidizer to fuel molar ratio on particle size and DC conductivity of CeO2 nanoparticles

    Harish, B. M.; Rajeeva, M. P.; Naveen, C. S.; Chaturmukha, V. S.; Avinash, B. S.; Jayanna, H. S.; Lamani, Ashok R.


    Cerium oxide nanoparticles were synthesized by solution combustion method with varying the oxidizer (cerium nitrate hexa hydrate) to fuel (Glycine) molar ratio. The prepared samples were characterized by UV-visible spectrometer, X-ray diffractometer (XRD), Scanning electron microscope (SEM) and Energy dispersive X-Ray analysis (EDAX). XRD pattern reveals the formation of cubic fluorite structure of CeO2. It was observed that finest crystallites were found at extreme fuel-deficient condition and it is good enough to produce favorable powder characteristics. The average crystallite size was found to be 14.46 nm to 21.57 nm. The temperature dependent dc conductivity was carried out using Keithley source meter between the temperature range from 300K to 573K. From this study it was found that the conductivity increases with increase of temperature due to semiconducting behavior of CeO2 and it decreases with particle size due to increase in the energy band gap.

  7. Study of the growth of biaxially textured CeO2 films during ion-beam-assisted deposition

    Biaxially textured CeO2 films were deposited on Hastelloy C276 substrates at room temperature using ion-beam-assisted e-beam evaporation with the ion beam directed at 55 deg. to the normal of the film plane. The crystalline structure and in-plane orientation of films were investigated by x-ray diffraction 2θ-scan and φ-scan. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO2 films have been successfully grown on Hastelloy C276

  8. Study of the growth of biaxially textured CeO2 films during ion-beam-assisted deposition

    Kim, Chang Su; Jo, Sung Jin; Jeong, Soon Moon; Kim, Woo Jin; Baik, Hong Koo; Lee, Se Jong; Song, Kie Moon


    Biaxially textured CeO2 films were deposited on Hastelloy C276 substrates at room temperature using ion-beam-assisted e-beam evaporation with the ion beam directed at 55° to the normal of the film plane. The crystalline structure and in-plane orientation of films were investigated by x-ray diffraction 2θ-scan and phgr-scan. The orientation of the films was studied as a function of ion-to-atom ratio and film thickness. The ion-to-atom ratio was varied by independently adjusting the deposition rate and the ion current density. Under optimum condition, (200) textured CeO2 films have been successfully grown on Hastelloy C276.

  9. Heteroepitaxy of Ir films on silicon with a ceria/yttria stabilized zirconia buffer layer

    Heteroepitaxial Ir films on Si(001) with a double ceria/yttria stabilized zirconia heteroepitaxial buffer layer were grown by magnetron sputtering. As-deposited CeO2 films covered with {111} faceted pyramids resulted in iridium films with the [001] axis normal to the substrate plane. The buffered substrates annealed at 1115 °C have a smooth surface; Ir films on such substrates have the (111) orientation and consist of grains turned at 90° toward each other. - Highlights: ► Heteroepitaxial Ir films on CeO2[001] film surface grow in two orientations. ► The surface of the as-grown CeO2 films is the {111} facets of the pyramids. ► Ir films deposited on this surface has [001] orientation. ► Annealing at 1115 °C of CeO2 films results in an atomically smooth surface. ► Ir films deposited on smooth surface have [111] orientation.

  10. Aspect Ratio Plays a Role in the Hazard Potential of CeO2 Nanoparticles in Mouse Lung and Zebrafish Gastrointestinal Tract

    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.


    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) ...