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Sample records for hydrogen-free ceo2 doped

  1. Optical characterization of hydrogen-free CeO2 doped DLC films deposited by unbalanced magnetron sputtering

    International Nuclear Information System (INIS)

    Zhang Zhenyu; Zhou Hongxiu; Guo Dongming; Gao Hang; Kang Renke

    2008-01-01

    A novel kind of hydrogen-free CeO 2 doped diamond-like carbon (DLC) films with thickness of 180-200 nm were deposited on silicon by unbalanced magnetron sputtering. Reduced reflectance and increased lifetime are expected with respect to pure DLC films, making these coatings good candidates as optical protective coatings for IR windows and solar cells. X-ray photoelectron spectroscopy confirms that CeO 2 is formed within the DLC films. Auger electron spectroscopy exhibits that the C, O, and Ce elements distribute uniformly across the film thickness, and C element diffuses into the Si substrate at the interface between the substrate and film. AFM shows that nanoparticles with diameter of around 50 nm are formed on the surface of deposited films, whose surface roughness is in the range of 1.3-2.3 nm. Raman spectra show the CeO 2 doped DLC films are amorphous DLC films, and both the G frequency and relative intensity ratio I D /I G are higher than those of pure DLC films. The photoluminescence of CeO 2 doped DLC films is obviously more intense than that of a pure DLC film, which indicates a promising potential as optical protective films for solar cells and IR window

  2. Initial Reduction of CO2 on Pd-, Ru-, and Cu-Doped CeO2(111) Surfaces: Effects of Surface Modification on Catalytic Activity and Selectivity.

    Science.gov (United States)

    Guo, Chen; Wei, Shuxian; Zhou, Sainan; Zhang, Tian; Wang, Zhaojie; Ng, Siu-Pang; Lu, Xiaoqing; Wu, Chi-Man Lawrence; Guo, Wenyue

    2017-08-09

    Surface modification by metal doping is an effective treatment technique for improving surface properties for CO 2 reduction. Herein, the effects of doped Pd, Ru, and Cu on the adsorption, activation, and reduction selectivity of CO 2 on CeO 2 (111) were investigated by periodic density functional theory. The doped metals distorted the configuration of a perfect CeO 2 (111) by weakening the adjacent Ce-O bond strength, and Pd doping was beneficial for generating a highly active O vacancy. The analyses of adsorption energy, charge density difference, and density of states confirmed that the doped metals were conducive for enhancing CO 2 adsorption, especially for Cu/CeO 2 (111). The initial reductive dissociation CO 2 → CO* + O* on metal-doped CeO 2 (111) followed the sequence of Cu- > perfect > Pd- > Ru-doped CeO 2 (111); the reductive hydrogenation CO 2 + H → COOH* followed the sequence of Cu- > perfect > Ru- > Pd-doped CeO 2 (111), in which the most competitive route on Cu/CeO 2 (111) was exothermic by 0.52 eV with an energy barrier of 0.16 eV; the reductive hydrogenation CO 2 + H → HCOO* followed the sequence of Ru- > perfect > Pd-doped CeO 2 (111). Energy barrier decomposition analyses were performed to identify the governing factors of bond activation and scission along the initial CO 2 reduction routes. Results of this study provided deep insights into the effect of surface modification on the initial reduction mechanisms of CO 2 on metal-doped CeO 2 (111) surfaces.

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

    Science.gov (United States)

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

    2015-12-21

    A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Room-temperature ferromagnetism in pure and Co doped CeO2 powders

    International Nuclear Information System (INIS)

    Wen Qiye; Zhang Huaiwu; Song Yuanqiang; Yang Qinghui; Zhu Hao; Xiao, John Q

    2007-01-01

    We report the room-temperature (RT) ferromagnetism (FM) observed in pure and Co doped CeO 2 powder. An insulating nonmagnetic CeO 2 single crystal, after grinding into fine powder, shows an RT-FM with a small magnetization of 0.0045 emu g -1 . However, the CeO 2 powder became paramagnetic after oxygen annealing, which strongly suggests an oxygen vacancy meditated FM ordering. Furthermore, by doping Co into CeO 2 powder the FM can significantly enhance through a F-centre exchange (FCE) coupling mechanism, in which both oxygen vacancies and magnetic ions are involved. As the Co content increases, the FM of Co doped CeO 2 initially increases to a maximum 0.47 emu g -1 , and then degrades very quickly. The complex correlation between the Co content and saturation magnetization was well interpreted by supposing the coexistence of three subsets of Co ions in CeO 2 . Our results reveal that the large RT-FM observed in Co doped CeO 2 powder originates from a combination effect of oxygen vacancies and transition metal doping

  5. Preparation of Mn doped CeO_2 nanoparticles with enhanced ferromagnetism

    International Nuclear Information System (INIS)

    Ravi, S.; Winfred Shashikanth, F.

    2017-01-01

    Spherical-like CeO_2 and Mn-doped CeO_2 using 6-aminohexanoic acid as surfactant exhibit enhanced ferromagnetism. The optical absorption spectra reveal a red shift with a band gap of 2.51 eV. The mechanics of ferromagnetism and the red shift were analyzed. These results provide a promising platform for developing a dilute magnetic semiconductor in spintronics. - Highlights: • Pure and Mn-doped CeO_2 is prepared with aminohexanoic acid as capping. • They exhibit wide optical absorption with red-shift in their band gap. • Mn-doped CeO_2 nanoparticle exhibit hysteresis at room temperature. • Results were promising to use in spintronics and opto-electronics field.

  6. Design of high quality doped CeO2 solid electrolytes with nanohetero structure

    International Nuclear Information System (INIS)

    Mori, T.; Ou, D.R.; Ye, F.; Drennan, J.

    2006-01-01

    Doped cerium (CeO 2 ) compounds are fluorite related oxides which show oxide ionic conductivity higher than yttria-stabilized zirconia in oxidizing atmosphere. As a consequence of this, a considerable interest has been shown in application of these materials for low (400-650 o C) temperature operation of solid oxide fuel cells (SOFCs). In this paper, our experimental data about the influence of microstructure at the atomic level on electrochemical properties were reviewed in order to develop high quality doped CeO 2 electrolytes in fuel cell applications. Using this data in the present paper, our original idea for a design of nanodomain structure in doped CeO 2 electrolytes was suggested. The nanosized powders and dense sintered bodies of M doped CeO 2 (M:Sm,Gd,La,Y,Yb, and Dy) compounds were fabricated. Also nanostructural features in these specimens were introduced for conclusion of relationship between electrolytic properties and domain structure in doped CeO 2 . It is essential that the electrolytic properties in doped CeO 2 solid electrolytes reflect in changes of microstructure even down to the atomic scale. Accordingly, a combined approach of nanostructure fabrication, electrical measurement and structure characterization was required to develop superior quality doped CeO 2 electrolytes in the fuel cells. (author)

  7. Room temperature ferromagnetism in Fe-doped CeO2 nanoparticles.

    Science.gov (United States)

    Maensiri, Santi; Phokha, Sumalin; Laokul, Paveena; Seraphin, Supapan

    2009-11-01

    RT ferromagnetism was observed in nanoparticles of Fe-doped CeO2 (i.e., Ce(0.97)Fe(0.03)O2) synthesized by a sol-gel method. The undoped and Fe-doped CeO2 were characterized by XRD, Raman spectroscopy, TEM, and VSM. The undoped samples and Ce(0.97)Fe(0.03)O2 precursor exhibit a diamagnetic behavior. The 673 K-calcined Ce(0.97)Fe(0.03)O2 sample is paramagnetic whereas 773 and 873 K-calcined Ce(0.97)Fe(0.03)O2 samples are ferromagnetism having the magnetizations of 4.65 x 10(-3) emu/g and 6.20 x 10(-3) emu/g at 10 kOe, respectively. Our results indicate that the ferromagnetic property is intrinsic to the Fe-doped CeO2 system and is not a result of any secondary magnetic phase or cluster formation.

  8. Structural, morphological and optical properties of spray deposited Mn-doped CeO2 thin films

    International Nuclear Information System (INIS)

    Pavan Kumar, CH.S.S.; Pandeeswari, R.; Jeyaprakash, B.G.

    2014-01-01

    Highlights: • Spray deposited undoped and Mn-doped CeO 2 thin films were polycrystalline. • Complete changeover of surface morphology upon 4 wt% Mn doping. • 4 wt% Mn-doped CeO 2 thin film exhibited a hydrophobic nature. • Optical band-gap decreases beyond 2 wt% Mn doping. - Abstract: Cerium oxide and manganese (Mn) doped cerium oxide thin films on glass substrates were prepared by home built spray pyrolysis system. The effect of Mn doping on the structural, morphological and optical properties of CeO 2 films were studied. It was found that both the undoped and doped CeO 2 films were polycrystalline in nature but the preferential orientation and grain size changed upon doping. Atomic force micrograph showed a complete changeover of surface morphology from spherical to flake upon doping. A water contact angle result displayed the hydrophobic nature of the doped CeO 2 film. Optical properties indicated an increase in band-gap and a decrease in transmittance upon doping owing to Moss–Burstein effect and inverse Moss–Burstein effects. Other optical properties such as refractive index, extinction coefficient and dielectric constant as a function of doping were analysed and reported

  9. Investigating the effect of Mn-doped CeO2 nanoparticles by co-precipitation method

    International Nuclear Information System (INIS)

    Prabaharan, D.D.M.; Sadaiyandi, K.; Mahendran, M.; Sagadevan, Suresh

    2018-01-01

    The paper exhibits a detailed study about the synthesis and characterization in analysis of structural, morphological, optical and electrical investigations of pure and Mn-doped Cerium oxide (CeO 2 ) nanoparticles which were synthesized by co-precipitation technique. Phase formation of the prepared sample was analyzed with powder X-ray diffraction (PXRD) examines, scanning electron microscopy (SEM) examination. The PXRD comes about affirmed partial crystallinity having cubic phases and the crystallite sizes of the pure and Mn-doped Cerium oxide (CeO 2 ) were estimated by utilizing Debye-Scherrer's formula and they were calculated to be 12 and 14 nm individually. SEM pictures revealed that the particles were profoundly accumulated and were of permeable nature. The optical properties of pure and Mn-doped CeO 2 were ascertained by using UV-visible absorption spectrum. The estimated band gap values for the pure and the Mn-doped CeO 2 nanoparticles were observed to be 2.7 and 2.6 eV, respectively, utilizing UV-Vis spectroscopy. At different frequencies and temperatures the dielectric properties of the Mn-doped Cerium oxide (CeO 2 ) nanoparticles, for example, the dielectric consistent, the dielectric loss and the AC conductivity, were studied. (orig.)

  10. Application of nanostructured Ca doped CeO2 for ultraviolet filtration

    International Nuclear Information System (INIS)

    Truffault, Laurianne; Ta, Minh-Tri; Devers, Thierry; Konstantinov, Konstantin; Harel, Valerie; Simmonard, Cyriaque; Andreazza, Caroline; Nevirkovets, Ivan P.; Pineau, Alain; Veron, Olivier; Blondeau, Jean-Philippe

    2010-01-01

    Calcium doped CeO 2 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%, CaCO 3 appears as a secondary phase. The calculated CeO 2 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 Ce 3+ atomic concentration in the pure sample was higher than that of the 20 mol% Ca-doped sample.

  11. Synthesis of Mn-doped CeO 2 nanorods and their application as ...

    Indian Academy of Sciences (India)

    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 ...

  12. Study of effect of co-doping on CIE coordinates of strontium cerium oxide phosphor (Sr_2CeO_4)

    International Nuclear Information System (INIS)

    Zambare, Pradip Z.; Ahirrao, P.B.; Chaudhari, D.B.; Zambare, A.P.; Mahajan, O.H.

    2016-01-01

    The phosphors Sr_2CeO_4 doped europium and gadolinium were synthesized by modified solid state diffusion method. From emission spectra, the CIE coordinates (x, y) of x% Eu"3"+ and 0.5 %Gd"3"+ doped Sr_2CeO_4 phosphors was calculated. In present paper, we investigate luminescence properties and colorimetric study of Sr_2CeO_4 doped 0.5% Gd"3"+, x% Eu"3"+. The phosphors Sr_2CeO_4 doped europium and gadolinium were successfully synthesized by modified solid state diffusion method. X-ray diffraction (XRD) profile confirms the orthorhombic nature of Eu"3"+ and 0.5% Gd"3"+ doped Sr_2CeO_4 phosphors. In addition, scanning electron Microscopy (SEM), Fourier-Transformation IR spectroscopy (FTIR), was also used to study the synthesized phosphors

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

    KAUST Repository

    Li, Jing; Chen, Fangping; Jin, Guanping; Feng, Xiaoshuang; Li, Xiaoxuan

    2015-01-01

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

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

    KAUST Repository

    Li, Jing

    2015-07-01

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

  15. Investigation of the physical, optical, and photocatalytic properties of CeO2/Fe-doped InVO4 composite

    Science.gov (United States)

    Chaison, Jindaporn; Wetchakun, Khatcharin; Wetchakun, Natda

    2017-12-01

    The CeO2/Fe-doped InVO4 composites with various Fe concentrations (0.5, 1.0, 2.0, 5.0 and 6.0 mol%) was synthesized by homogeneous precipitation and hydrothermal methods. The as-synthesized samples were characterized by powder X-ray diffraction (XRD), Brunauer Emmett and Teller (BET)-specific surface area, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and UV-visible diffuse reflectance spectroscopy (DRS). Fe-doping into InVO4 crystal induces the distortion of the crystalline structure, the transformation of InVO4 morphology, and the new energy subband level generation of Fe between the CB and VB edge of InVO4. The electron excitation from the VB to Fe orbitals results in the decreased band gap and the extended absorption of visible-light, and thus enhances its photocatalytic performance. Visible-light-driven photocatalytic degradation of Rhodamine B (RhB) dye in water was used to evaluate the photocatalytic performance of CeO2/Fe-doped InVO4 composites. The results revealed that there is an optimum Fe (5.0 mol %) doping level. The composite with the optimum doping level obtains high photocatalytic activity of CeO2/Fe-doped InVO4 composite compared to pure CeO2 and pure InVO4 host. The increase of photocatalytic activity of CeO2/Fe-doped InVO4 composite was ascribed to the surface area, crystal defect, and band gap energy. Moreover, the photocatalytic enhancement is also because iron ions act as a trapping site, which results in the higher separation efficiency of photogenerated electrons and holes pairs in the CeO2/InVO4 composite. The evaluation of radical scavengers confirmed that hydroxyl radical was the main active species during the photodegradation of RhB. These synergistic effects are responsible for the enhanced photocatalytic activity of CeO2/Fe-doped InVO4 composite. Furthermore, the possible enhanced photocatalytic mechanism

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

    Directory of Open Access Journals (Sweden)

    Chunjie Wang

    2014-01-01

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

  17. Electronic structure study of Co doped CeO2 nanoparticles using X-ray absorption fine structure spectroscopy

    International Nuclear Information System (INIS)

    Kumar, Shalendra; Gautam, Sanjeev; Song, T.K.; Chae, Keun Hwa; Jang, K.W.; Kim, S.S.

    2014-01-01

    Highlights: • The electronic structural of Co–CeO 2 nanoparticles is investigated using XAFS. • Ce M 5,4 , Ce L 3 and O K edge NEXAFS reveal that the Ce-ions are in +4 valence state. • The NEXAFS spectrum performed at Co L3,2-edge confirms Co-ion in 2+ state. • The EXAFS analysis also show that Co ions are occupying Ce position in doped CeO 2 . • The distances between Ce–O and Ce–Ce/Co in all shells decreases with Co doping. - Abstract: We investigated the electronic structure of well characterized Co doped CeO 2 nanoparticles using X-ray absorption fine structure (XAFS) spectroscopy. Near edge X-ray absorption fine structure (NEXAFS) spectra at Ce M 5,4 , Ce L 3 and O K-edge conclude that the Ce-ions are in +4 valence state in pure as well as in Co doped CeO 2 nanoparticles. The local structure around Ce-atom in Co doped CeO 2 nanoparticles was also determined using extended X-ray absorption fine structure (EXAFS) spectroscopy at Ce L 3 edge. The EXAFS analysis suggest that the inter-atomic distance of Ce–O, Ce–Ce/Co decreases with Co doping, which indicate a contraction of the lattice. The decease in Ce–O distance also reflect that there is a formation of oxygen vacancies in CeO 2 matrix. The Debye–Waller factor also shows the consistent behaviour for all the coordination shells. The atomic multiplet calculations for Co L 3,2 -edge was performed to determine the valence state, symmetry and field splitting, which reflect that Co-ions are in 2+ state and substituted at Ce-site with crystal field splitting of 10Dq=-0.57eV. The XAFS measurements reveal that the Co-ions occupy the Ce position in the CeO 2 host matrix and create a oxygen vacancy

  18. A comparative study of the magnetization in transition metal ion doped CeO2, TiO2 and SnO2 nanoparticles

    Science.gov (United States)

    Apostolov, A. T.; Apostolova, I. N.; Wesselinowa, J. M.

    2018-05-01

    Using the microscopic s-d model taking into account anharmonic spin-phonon interactions we have studied the magnetic properties of Co and Cu ion doped CeO2 and TiO2 nanoparticles and compared them with those of SnO2. By Co-doping there is a maximum in the magnetization M(x) curve for all nanoparticles observed in the most transition metal doped ones. The s-d interaction plays an important role by the decrease of M at higher dopant concentration. We have discussed the magnetization in dependence of different model parameters. By small Cu-ion doping there are some differences. In CeO2M decreases with the Cu-concentration, whereas in TiO2 and SnO2M increases. For higher Cu dopant concentrations M(X) decreases in TiO2 nanoparticles. We obtain room temperature ferromagnetism also in Zn doped CeO2, TiO2 and SnO2 nanoparticles, i.e. in non-transition metal ion doped ones. The different behavior of M in Co and Cu doped nanoparticles is due to a combination effect of multivalent metal ions, oxygen vacancies, different radius of cation dopants, connection between lattice and magnetism, as well as competition between the s-d and d-d ferromagnetic or antiferromagnetic interactions.

  19. Inhibition of Neuroblastoma cancer cells viability by ferromagnetic Mn doped CeO_2 monodisperse nanoparticles mediated through reactive oxygen species

    International Nuclear Information System (INIS)

    Abbas, Fazal; Jan, Tariq; Iqbal, Javed; Haider Naqvi, M. Sajjad; Ahmad, Ishaq

    2016-01-01

    Here we report the Mn doping induced effects on structural, Raman, optical, magnetic and anticancer properties of CeO_2 nanoparticles prepared via soft chemical route. Structural and microstructural results infer that the synthesized nanoparticles have single phase cubic fluorite structure of CeO_2 and that Mn doping results in enhancement of the structural defects. Scanning electron microscopy results reveal the formation of monodisperse nanoparticles having average particle size ranging from 30 to 41 nm. The optical absorbance spectroscopy analysis discloses the band gap energy tailoring of CeO_2 nanoparticles via Mn doping. Room temperature ferromagnetism (RTFM) has been found in both as-prepared and Mn doped CeO_2 nanoparticles. This RTFM of the synthesized nanoparticles have been attributed to the Mn ions and surface defects such as oxygen vacancies. Finally, the influence of Mn dopant on the cell viability and reactive oxygen species (ROS) generation levels of CeO_2 nanoparticles in the presence of healthy and cancerous cells have been studied. It has been observed that the differential cytotoxicity of the synthesized nanoparticles is strongly correlated with level of ROS generation. - Highlights: • Mn doped CeO_2 nanoparticles with cubic fluorite structure were synthesized. • Mn dopant significantly tailored the band gap of CeO_2 nanoparticles. • The synthesized nanoparticles exhibited room temperature ferromagnetic behavior. • The cytotoxicity of these nanoparticles was reported for the first time. • The synthesized nanoparticles exhibited differential cytotoxicity.

  20. Confined NaAlH4 nanoparticles inside CeO2 hollow nanotubes towards enhanced hydrogen storage.

    Science.gov (United States)

    Gao, Qili; Xia, Guanglin; Yu, Xuebin

    2017-10-05

    NaAlH 4 has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO 2 hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH 4 nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH 4 inside CeO 2 HNTs, synthesized via the infiltration of molten NaAlH 4 into the CeO 2 HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO 2 HNTs-catalyzed NaAlH 4 . The onset dehydrogenation temperature of the NaAlH 4 @CeO 2 composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO 2 HNTs-catalyzed NaAlH 4 , respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH 4 under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO 2 HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH 4 NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH 4 .

  1. Ethanol Sensor of CdO/Al2O3/CeO2 Obtained from Ce-DOPED Layered Double Hydroxides with High Response and Selectivity

    Science.gov (United States)

    Xu, Dongmei; Guan, Meiyu; Xu, Qinghong; Guo, Ying; Wang, Yao

    2013-04-01

    In this paper, Ce-doped CdAl layered double hydroxide (LDH) was first synthesized and the derivative CdO/Al2O3/CeO2 composite oxide was prepared by calcining Ce-doped CdAl LDH. The structure, morphology and chemical state of the Ce doped CdAl LDH and CdO/Al2O3/CeO2 were also investigated by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), solid state nuclear magnetic resonance (SSNMR), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The gas sensing properties of CdO/Al2O3/CeO2 to ethanol were further studied and compared with CdO/Al2O3 prepared from CdAl LDH, CeO2 powder as well as the calcined Ce salt. It turns out that CdO/Al2O3/CeO2 sensor shows best performance in ethanol response. Besides, CdO/Al2O3/CeO2 possesses short response/recovery time (12/72 s) as well as remarkable selectivity in ethanol sensing, which means composite oxides prepared from LDH are very promising in gas sensing application.

  2. Study of the defect structure of ''pure'' and doped nonstoichiometric CeO2. Final report, January 1, 1965--May 31, 1977

    International Nuclear Information System (INIS)

    Blumenthal, R.N.

    1977-11-01

    The defect structure and transport properties of defects in nonstoichiometric oxides was studied based on their electrical and thermodynamic behavior. Similar studies were also made on doped-nonstoichiometric oxides to determine the effect of the ionic radii, valence and concentration of the dopant cation on the nonstoichiometric defect structure and the transport properties of these defects. The thermodynamic and electrical property study on ''pure'' and doped-nonstoichiometric CeO 2 /sub -x/ is reviewed. The combined study of the electrical conductivity, ionic transference, and thermodynamic measurements initiated on CaO-doped CeO 2 as a function of temperature, oxygen pressure and CaO content is discussed. The results of similar measurements on CeO 2 doped with other oxides (e.g., ThO 2 , Ta 2 O 5 , etc.) which have cations with different valences and ionic radii are also discussed. The primary objective of these studies was to determine the effect of ionic radii, valence and concentration of the dopant cation on (1) the nonstoichiometric behavior, (2) the thermodynamic quantities ΔantiH/sub O 2 / and ΔantiS/sub O 2 /, (3) the nonstoichiometric defect structure, (4) the electronic and ionic conductivities, and (5) the mobility of electrons and oxygen vacancies in doped CeO 2 /sub -x/

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

    Science.gov (United States)

    Heydari, Hamid; Gholivand, Mohammad Bagher

    2017-03-01

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

  4. Hydrocracking of cumene over Ni/Al 2O 3 as influenced by CeO 2 doping and γ-irradiation

    Science.gov (United States)

    El-Shobaky, G. A.; Doheim, M. M.; Ghozza, A. M.

    2004-01-01

    Cumene hydrocracking was carried out over pure and doped Ni/Al 2O 3 solids and also, on these solids after exposure to different doses of γ-rays between 0.4 and 1.6 MGy. The dopant concentration was varied between 1 and 4 mol% CeO 2. Pure and doped samples were subjected to heat treatment at 400°C and cumene hydrocracking reaction was carried out using various solids at temperatures between 250°C and 400°C by means of micropulse technique. The results showed that both CeO 2 doping and γ-irradiation of the investigated system brought about an increase in its specific surface area. γ-irradiation of pure samples increased their catalytic activities effectively. However, the doping caused a decrease in the catalytic activity. γ-irradiation of the doped samples brought about a net decrease in the catalytic activity. The catalytic reaction products over different investigated solids were ethylbenzene as a major product together with different amounts of toluene, benzene and C 1-C 3 gaseous hydrocarbons. The selectivity towards the formation of various reaction products varies with the reaction temperature, doping and γ-irradiation.

  5. Electrical and microstructural properties of Yb-doped CeO2

    Directory of Open Access Journals (Sweden)

    B. Matović

    2014-06-01

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

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

    Directory of Open Access Journals (Sweden)

    Oman ZUAS

    2013-12-01

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

  7. Towards understanding the electronic structure of Fe-doped CeO2 nanoparticles with X-ray spectroscopy.

    Science.gov (United States)

    Wang, Wei-Cheng; Chen, Shih-Yun; Glans, Per-Anders; Guo, Jinghua; Chen, Ren-Jie; Fong, Kang-Wei; Chen, Chi-Liang; Gloter, Alexandre; Chang, Ching-Lin; Chan, Ting-Shan; Chen, Jin-Ming; Lee, Jyh-Fu; Dong, Chung-Li

    2013-09-21

    This study reports on the electronic structure of Fe-doped CeO2 nanoparticles (NPs), determined by coupled X-ray absorption spectroscopy and X-ray emission spectroscopy. A comparison of the local electronic structure around the Ce site with that around the Fe site indicates that the Fe substitutes for the Ce. The oxygen K-edge spectra that originated from the hybridization between cerium 4f and oxygen 2p states are sensitive to the oxidation state and depend strongly on the concentration of Fe doping. The Ce M(4,5)-edges and the Fe L(2,3)-edges reveal the variations of the charge states of Ce and Fe upon doping, respectively. The band gap is further obtained from the combined absorption-emission spectrum and decreased upon Fe doping, implying Fe doping introduces vacancies. The oxygen vacancies are induced by Fe doping and the spectrum reveals the charge transfer between Fe and Ce. Fe(3+) doping has two major effects on the formation of ferromagnetism in CeO2 nanoparticles. The first, at an Fe content of below 5%, is that the formation of Fe(3+)-Vo-Ce(3+) introduces oxygen deficiencies favoring ferromagnetism. The other, at an Fe content of over 5%, is the formation of Fe(3+)-Vo-Fe(3+), which favors antiferromagnetism, reducing the Ms. The defect structures Fe(3+)-Vo-Ce(3+) and Fe(3+)-Vo-Fe(3+) are crucial to the magnetism in these NPs and the change in Ms can be described as the effect of competitive interactions of magnetic polarons and paired ions.

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

    DEFF Research Database (Denmark)

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

    1994-01-01

    Samples of CeO2 doped with oxides such as CaO and Gd2O3 were prepared. Their conductivities and expansions onreduction were measured at 1000°C, and the thermal expansion coefficients in the range 50 to 1000°C were determined. Theionic and electronic conductivity were derived from curves of total ...

  9. Enhancement of photocatalytic properties of TiO2 nanoparticles doped with CeO2 and supported on SiO2 for phenol degradation

    International Nuclear Information System (INIS)

    Hao, Chunjing; Li, Jing; Zhang, Zailei; Ji, Yongjun; Zhan, Hanhui; Xiao, Fangxing; Wang, Dan; Liu, Bin; Su, Fabing

    2015-01-01

    Highlights: • CeO 2 -TiO 2 /SiO 2 composites were prepared via a facile co-precipitation method. • Introduction of SiO 2 support increases the dispersion of CeO 2 -TiO 2 . • CeO 2 -TiO 2 /SiO 2 exhibits an enhanced photocatalytic efficiency for phenol degradation. • Ce 3+ /Ce 4+ pair coexisting in CeO 2 improves electron–hole pairs separation efficiency. - Abstract: A series of CeO 2 -TiO 2 and CeO 2 -TiO 2 /SiO 2 composites were prepared with TiCl 4 and Ce (NO 3 ) 3 ·6H 2 O as precursors via a facile co-precipitation method. The obtained samples were characterized by various techniques such as X-ray diffraction (XRD), nitrogen adsorption (N 2 -BET), Fourier transformation infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis spectroscopy measurements. The results indicated that TiO 2 doped with CeO 2 and supported on SiO 2 could reduce the crystallite size, inhibit the phase transformation, enhance the thermal stability, and effectively extend the spectral response from UV to visible range. When applied to the phenol photodegradation on a homemade batch reactor with an external cooling jacket, the CeO 2 -TiO 2 /SiO 2 catalysts exhibited significantly enhanced photodegradation efficiency in comparison with commercial Degussa P25 and CeO 2 -TiO 2 . The unique catalytic properties of CeO 2 -TiO 2 /SiO 2 were ascribed to improved electron–hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce 3+ /Ce 4+ , as well as high dispersion of active component of CeO 2 -TiO 2 as a result of the introduction of SiO 2 support. Furthermore, the catalysts can be easily recovered from the reaction solution by centrifugation and reused for four cycles without significant loss of activity

  10. Hydrogen in oxygen-free, phosphorus-doped copper-Charging techniques, hydrogen contents and modelling of hydrogen diffusion and depth profile

    International Nuclear Information System (INIS)

    Martinsson, Aasa; Sandstroem, Rolf; Lilja, Christina

    2013-01-01

    In Sweden spent nuclear fuel is planned to be disposed of by encapsulating in cast iron inserts protected by a copper shell. The copper can be exposed to hydrogen released during corrosion processes in the inserts. If the hydrogen is taken up by the copper, it could lead to hydrogen embrittlement. Specimens from oxygen-free copper have been hydrogen charged using two different methods. The purpose was to investigate how hydrogen could be introduced into copper in a controlled way. The thermal charging method resulted in a reduction of the initial hydrogen content. After electrochemical charging of cylindrical specimens, the measured hydrogen content was 2.6 wt. ppm which should compared with 0.6 wt. ppm before charging. The retained hydrogen after two weeks was reduced by nearly 40%. Recently the paper 'Hydrogen depth profile in phosphorus-doped, oxygen-free copper after cathodic charging' (Martinsson and Sandstrom, 2012) has been published. The paper describes experimental results for bulk specimens as well as presenting a model. Almost all the hydrogen is found to be located less than 100 μm from the surface. This model is used to interpret the experimental results on foils in the present report. Since the model is fully based on fundamental equations, it can be used to analyse what happens in new situations. In this report the effect of the charging intensity, the grain size, the critical nucleus size for hydrogen bubble formation as well as the charging time are analysed

  11. Hydrogen in oxygen-free, phosphorus-doped copper - Charging techniques, hydrogen contents and modelling of hydrogen diffusion and depth profile

    Energy Technology Data Exchange (ETDEWEB)

    Martinsson, Aasa [Swerea KIMAB, Kista (Sweden); Sandstroem, Rolf [Swerea KIMAB, Kista (Sweden); Div. of Materials Science and Engineering, KTH Royal Institute of Technology, Stockholm (Sweden); Lilja, Christina [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)

    2013-01-15

    In Sweden spent nuclear fuel is planned to be disposed of by encapsulating in cast iron inserts protected by a copper shell. The copper can be exposed to hydrogen released during corrosion processes in the inserts. If the hydrogen is taken up by the copper, it could lead to hydrogen embrittlement. Specimens from oxygen-free copper have been hydrogen charged using two different methods. The purpose was to investigate how hydrogen could be introduced into copper in a controlled way. The thermal charging method resulted in a reduction of the initial hydrogen content. After electrochemical charging of cylindrical specimens, the measured hydrogen content was 2.6 wt. ppm which should compared with 0.6 wt. ppm before charging. The retained hydrogen after two weeks was reduced by nearly 40%. Recently the paper 'Hydrogen depth profile in phosphorus-doped, oxygen-free copper after cathodic charging' (Martinsson and Sandstrom, 2012) has been published. The paper describes experimental results for bulk specimens as well as presenting a model. Almost all the hydrogen is found to be located less than 100 {mu}m from the surface. This model is used to interpret the experimental results on foils in the present report. Since the model is fully based on fundamental equations, it can be used to analyse what happens in new situations. In this report the effect of the charging intensity, the grain size, the critical nucleus size for hydrogen bubble formation as well as the charging time are analysed.

  12. Kinetic Monte Carlo model of defect transport and irradiation effects in La-doped CeO2

    International Nuclear Information System (INIS)

    Oaks, Aaron; Yun Di; Ye Bei; Chen Weiying; Stubbins, James F.

    2011-01-01

    A generalized Kinetic Monte Carlo code was developed to study oxygen mobility in UO 2 type nuclear fuels, using lanthanum doped CeO 2 as a surrogate material. Molecular Statics simulations were performed using interatomic potentials for CeO 2 developed by Gotte, Minervini, and Sayle to calculate local configuration-dependent oxygen vacancy migration energies. Kinetic Monte Carlo simulations of oxygen vacancy diffusion were performed at varying lanthanum dopant concentrations using the developed generalized Kinetic Monte Carlo code and the calculated configuration-dependent migration energies. All three interatomic potentials were found to confirm the lanthanum trapping effect. The results of these simulations were compared with experimental data and the Gotte potential was concluded to yield the most realistic diffusivity curve.

  13. Photoluminescent properties of Sr2CeO4: Eu3+ and Sr2CeO4: Eu2+ phosphors suitable for near ultraviolet excitation

    International Nuclear Information System (INIS)

    Suresh, K.; Poornachandra Rao, N.V.; Murthy, K.V.R.

    2014-01-01

    Powder phosphors of 1 mol% Eu 3+ - and Eu 2+ -doped strontium cerium oxide (Sr 2 CeO 4 ) were synthesized by standard solid-state reaction method. Eu 3+ - and Eu 2+ -doped Sr 2 CeO 4 phosphors fired at 1100 ℃ for 2 h were analysed by X-ray diffraction (XRD) and photoluminescence (PL) techniques. The XRD patterns confirm that the obtained phosphors are a single phase of Sr 2 CeO 4 composed of orthorhombic structure. Room temperature PL excitation spectrum of air-heated Sr 2 CeO 4 : Eu phosphor has exhibited bands at 260, 280 and 350 nm. Whereas the excitation spectrum of Sr 2 CeO 4 : Eu phosphor heated under reducing (carbon) atmosphere exhibited single broadband range from 260 to 390 nm. The (PL) emission peaks of both the phosphors at 467 (blue), 537 (green) and 616 nm (red) generate white light under 260, 280 and 350 nm excitation wavelengths. The Commission International de l'Eclairage (CIE) colour coordinates conforms that these phosphors emitting white light. The results reveal that these phosphors are multifunctional phosphors which emit white light under these excitations that they could be used as white components for display and lamp devices and as well as possible good light-conversion phosphor LEDs under near-ultraviolet (nUV) chip. (author)

  14. Study of the defect structure of ''pure'' and doped nonstoichiometric CeO2

    International Nuclear Information System (INIS)

    Blumenthal, R.N.

    1975-09-01

    Electrical conductivity and thermogravimetric measurements were made on Ta 2 O 5 -doped nonstoichiometric CeO 2 (i.e. Ce/sub 1-y/Ta/sub y/O/sub 2-x/ ) as a function of temperature and oxygen partial pressure. Over a limited range of temperature and nonstoichiometry, the isothermal dependence of the electrical conductivity on nonstoichiometry may be described by the equation sigma = A + Bx, where A is the electronic conductivity associated with the electronic defects produced by doping CeO 2 with Ta 2 O 5 . The electronic conductivity resulting from the nonstoichiometric defect reaction O/sup x/ + 2Ce/sub Ce//sup x/ = V 0 + 2Ce'sub Ce/ + 1 / 2 O 2 (g) is equal to Bx. The ionic conductivity may be described by the relation sigma/sub i/ = B[y+x]eμ'/sub V 0 / exp (--E/sub i//kT), and the electronic conductivity by the isothermal expressions sigma/sub e/ proportional to P/sub O 2 //sup -1/4/ and sigma/sub e/ proportional to x; x less than 3 x 10 -2 . These results are consistent with defect models involving doubly ionized oxygen vacancies. An empirical expression (i.e. Δ anti H/sub O 2 / proportional to y/2 or z/4) was obtained relating the dependence of Δ anti H/sub O 2 / on the dopant concentration of lower valent foreign cations (e.g. y/2 for Ce/sub 1-y/M/sub y/O/sub 2-y-x/ and z/4 for Ce/sub 1-z/M/sub z/O/sub 2-z/2-x/ where M = Ca, Sr and M' = Y, La). (auth)

  15. Infrared to visible upconversion luminescence in Er3+/Yb3+ co-doped CeO2 inverse opal

    International Nuclear Information System (INIS)

    Yang, Zhengwen; Wu, Hangjun; Liao, Jiayan; Li, Wucai; Song, Zhiguo; Yang, Yong; Zhou, Dacheng; Wang, Rongfei; Qiu, Jianbei

    2013-01-01

    Highlights: • UC emission of Er 3+ was modified by introducing the structure of inverse opal. • Color tuning of CeO 2 :Yb, Er inverse opal was realized by inhibition of UC emission. • Two-photon excitation processes were observed in CeO 2 :Yb, Er inverse opal. -- Abstract: Infrared to visible upconversion luminescence has been investigated in Er 3+ /Yb 3+ co-doped CeO 2 inverse opal. Under the excitation of 980 nm diode lasers, visible emissions centered at 525, 547, 561, 660 and 680 nm are observed, which are assigned to the Er 3+ transitions of 2 H 11/2 → 4 I 15/2 (525 nm), 4 S 3/2 → 4 I 15/2 (547, 561 nm), 4 F 9/2 → 4 I 15/2 (660 and 680 nm), respectively. The effect of photonic band gap on the upconversion luminescence intensity was also obtained. Additionally, the upconversion luminescence mechanism was studied. The dependence of Er 3+ upconversion emission intensity on pump power reveals that it is a two-photon excitation process

  16. Isolated centres versus defect associates in Sm3+-doped CeO2: a spectroscopic investigation

    International Nuclear Information System (INIS)

    Tiseanu, Carmen; Avram, Daniel; Cojocaru, Bogdan; Parvulescu, Vasile I; Vela-Gonzalez, Andrea V; Sanchez-Dominguez, Margarita

    2013-01-01

    The interactions between Sm 3+ and oxygen vacancies in CeO 2 are probed by the use of tuneable laser excited time-resolved photoluminescence and Raman spectroscopies. It is found that Sm 3+ (with doping concentrations of 0.1, 0.3, 1 and 5 wt%) substitutes largely for Ce 4+ in sites with cubic symmetry and the corresponding emission is sensitized via the Ce 4+ –O 2− charge-transfer band of CeO 2 . It is established from the photoluminescence spectra measured at long delay after the laser pulse that the local environment around cubic Sm 3+ centres is not changed with concentration and ceria size. In addition to cubic symmetry Sm 3+ centres, low-symmetry Sm 3+ centres tentatively assigned to the Sm 3+ –oxygen vacancy associates of nearest-neighbour type are also observed. Their emission is preferentially excited via the weak f–f absorption transitions of Sm 3+ . A relatively strong concentration-induced quenching of Sm 3+ emission was inferred from the decrease in the average emission lifetimes from 2.1 ms (0.1 wt%) to 0.87 ms (5 wt%). The local environments of Sm 3+ and Eu 3+ in CeO 2 are also compared on the basis of their emission spectra and decays. (paper)

  17. Sintering Studies of Ga-Doped CeO2 (Ga-Doped PuO2 Surrogate) for Mixed Oxide Nuclear Fuel

    International Nuclear Information System (INIS)

    Haertling, C.; Huling, J.; Park, Y.S.

    1999-01-01

    Sintering studies of CeO 2 and CeO 2 + 2 wt. % Ga 2 O 3 were completed. Firing temperatures studied were 1250-1650 C with 2 to 4 hour firing soak times in air. Powders fabricated by three methods (as-received, attrition-mill and nitrite-derived) were studied. Attrition-milled CeO 2 improved densities as compared with as-received CeO 2 . Attrition-milled CeO 2 with 2 wt.% Ga 2 O 3 showed decreased densities with increasing temperatures. As-received CeO 2 with 2 wt.% Ga 2 O 3 showed a opposite trend, increasing in density with increased firing temperature. Two pellet preparation methods were studied, a one-step-press method and a two-step-press method. The two-step-press method showed greater densities at lower firing temperatures and times as compared with the one-step-press method, however for CeO 2 + 2 wt.% Ga 2 O 3 , the two methods gave equivalent results at 1650 C, 6 hr. firing conditions

  18. Tuning the hybridization and magnetic ground state of electron and hole doped CeOs2Al10 : An x-ray spectroscopy study

    Science.gov (United States)

    Chen, Kai; Sundermann, Martin; Strigari, Fabio; Kawabata, Jo; Takabatake, Toshiro; Tanaka, Arata; Bencok, Peter; Choueikani, Fadi; Severing, Andrea

    2018-04-01

    Here we present linear and circular polarized soft x-ray absorption spectroscopy (XAS) data at the Ce M4 ,5 edges of the electron (Ir) and hole-doped (Re) Kondo semiconductor CeOs2Al10 . Both substitutions have a strong impact on the unusual high Néel temperature TN=28.5 K, and also the direction of the ordered moment in case of Ir. The substitution dependence of the linear dichroism is weak thus validating the crystal-field description of CeOs2Al10 being representative for the Re and Ir substituted compounds. The impact of electron and hole doping on the hybridization between conduction and 4 f electrons is related to the amount of f0 in the ground state and reduction of x-ray magnetic circular dichroism. A relationship of c f -hybridization strength and enhanced TN is discussed. The direction and doping dependence of the circular dichroism strongly supports the idea of strong Kondo screening along the crystallographic a direction.

  19. Hydrogen Production from Gasification of Palm Kernel Shell in the Presence of Fe/ CeO_2 Catalysts

    International Nuclear Information System (INIS)

    Anita Ramli; Mas Fatiha Mohamad; Suzana Yusup; Taufiq, Y.Y.H.

    2016-01-01

    Bio hydrogen is a renewable source of clean fuel and energy which can be derived from biomass. One of the suitable candidate as a source of biomass is palm kernel shell (PKS). Our initial work shows that bio hydrogen may be produced from PKS in the presence of zeolite supported catalysts. The potential of using cerium oxide (CeO_2) supported catalysts for the production of bio hydrogen from PKS is explored in this work using 2.5 - 10 % Fe loading. The catalysts were prepared by incipient wetness impregnation method and calcined at 500 degree Celsius for 16 h. The physicochemical properties of these catalysts were characterized using BET and XRD. The catalysts were tested in dry and steam gasification of PKS at 700 degree Celsius using PKS feeding rate of 2 g h"-"1 under N_2 atmosphere with biomass to catalyst ratio of 3:1 (wt/ wt). Steam to biomass ratio of 3.5:1 (wt/ wt) was used in steam gasification reaction. The gaseous products were analyzed using an on-line gas chromatography equipped with thermal conductivity detectors (TCD) and fitted with Molsieve 5A and Hayesep Q columns. Result shows that 2.5 % Fe/ CeO_2 gave the highest hydrogen production in both the dry and steam gasification of PKS. (author)

  20. Sr2CeO4: Electronic and structural properties

    International Nuclear Information System (INIS)

    Rocha, Leonardo A.; Schiavon, Marco A.; Nascimento, Clebio S.; Guimarães, Luciana; Góes, Márcio S.; Pires, Ana M.; Paiva-Santos, Carlos O.

    2014-01-01

    Highlights: • Sr 2 CeO 4 it was obtained from the heat treatment of Ce 3+ -doped strontium oxalate. • Rietveld analysis made it possible to obtain information about crystalline structure. • Experimental band gap value was compared with theoretical obtained by Sparkle/PM7. • The materials obtained shows intense photoluminescence and scintillator properties. - Abstract: This work presents on the preparation and photoluminescent properties of Sr 2 CeO 4 obtained from the heat treatment of Ce(III)-doped strontium oxalate (10, 25 and 33 mol%). The oxalate precursors were heat treated at 1100 °C for 12 h. The structure of this photoluminescent material was evaluated by the Rietveld method. The route used in this work to prepare the materials showed to be viable when compared to other synthesis reported in the literature. The Sr 2 CeO 4 material showed a broad and intense band emission with a maximum around 485 nm. The quantitative phase analysis showed that the Sr 2 CeO 4 photoluminescent phase is the majority one compared to the impurity phases of SrCeO 3 and SrCO 3 . From all results it was possible to verify a complete elimination of the CeO 2 phase for the sample obtained from the heat treatment of oxalate precursor containing 33 mol% of cerium(III). The material showed excellent properties for possible candidate as scintillator materials, and in the improvement of efficiency of solar cells when excited in the UV–vis region. The CIE chromaticity diagram it is also reported in this work

  1. Sm-doped CeO2 single buffer layer for YBCO coated conductors by polymer assisted chemical solution deposition (PACSD) method

    International Nuclear Information System (INIS)

    Li, G.; Pu, M.H.; Sun, R.P.; Wang, W.T.; Wu, W.; Zhang, X.; Yang, Y.; Cheng, C.H.; Zhao, Y.

    2008-01-01

    An over 150 nm thick Sm 0.2 Ce 0.8 O 1.9-x (SCO) single buffer layer has been deposited on bi-axially textured NiW (2 0 0) alloy substrate. Highly in-plane and out-of-plane oriented, dense, smooth and crack free SCO single layer has been obtained via a polymer-assisted chemical solution deposition (PACSD) approach. YBCO thin film has been deposited equally via a PACSD route on the SCO-buffered NiW, the as grown YBCO yielding a sharp transition at T c0 = 87 K as well as J c (0 T, 77 K) ∼ 1 MA/cm 2 . These results indicates that RE (lanthanides other than Ce) doping may be an effective approach to improve the critical thickness of solution derived CeO 2 film, which renders it a promising candidate as single buffer layer for YBCO coated conductors

  2. Photocatalytic performance of TiO2 catalysts modified by H3PW12O40, ZrO2 and CeO2

    Institute of Scientific and Technical Information of China (English)

    CAI Tiejun; LIAO Yuchao; PENG Zhenshan; LONG Yunfei; WEI Zongyuan; DENG Qian

    2009-01-01

    The binary composite photo-catalysts CeO2/TiO2, ZrO2/TiO2 and the ternary composite photo-catalysts H3PW12O40-CeO2/TiO2,H2PW12O40-ZrO2/TiO2 were prepared by sol-gel method. The catalysts were characterized by thermogravimetric-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The photocatalyfic elimination of methanol was used as model reaction to evaluate the photocatalytic activity of the composite catalysts under ultraviolet light irradiation. The effects of doped content, activation temperature, time, initial concentration of methanol and gas flow rate on the catalytic activity were investigated. The results showed that after doping a certain amount of CeO2 and ZrO2, crystaniTation process of TiO2 was restrained, particles of catalysts are smaller and more uniform. Doping ZrO2 not only significantly improved the catalytic activity, but also increased thermal stability. Doping H3PW12O40 also enhanced the catalytic activity. The catalytic activities of binary and ternary composite photocatalysts were significantly higher than tin-doped TiO2. The dynamics law of photocatalytic reaction over the binary CeO2/TiO2 and ZrO2/TiO2 catalysts has been studied. The activation energy 15.627 and 15.631 kJ/mol and pre-exponential factors 0.5176 and 0.9899 s-1 over each corresponding catalyst were obtained. This reaction accords to the first order dynamics law.

  3. Characteristics of hydrogen co-doped ZnO : Al thin films

    International Nuclear Information System (INIS)

    Lee, S H; Lee, T S; Lee, K S; Cheong, B; Kim, W M; Kim, Y D

    2008-01-01

    ZnO films co-doped with H and Al (HAZO) were prepared by sputtering ZnO targets containing 1 wt% Al 2 O 3 on Corning glass at a substrate temperature of 150 deg. C with Ar and H 2 /Ar gas mixtures. The effects of hydrogen addition to Al-doped ZnO (AZO) films with low Al content on the electrical, the optical and the structural properties of the as-grown films as well as the vacuum- and air-annealed films were examined. Secondary ion mass spectroscopy analysis showed that the hydrogen concentration increased with increasing H 2 in sputter gas. For the as-deposited films, the free carrier number increased with increasing H 2 . The Hall mobility increased at low hydrogen content, reaching a maximum before decreasing with a further increase of H 2 content in sputter gas. Annealing at 300 deg. C resulted in the removal of hydrogen, causing a decrease in the carrier concentration. It was shown that hydrogen might exist as single isolated interstitial hydrogen bound with oxygen, thereby acting like an anionic dopant. Also, it was shown that the addition of hydrogen to ZnO films doped with low metallic dopant concentration could yield transparent conducting films with very low absorption loss as well as with proper electrical properties, which is suitable for thin film solar cell applications

  4. Application of hydrogen-doped In2O3 transparent conductive oxide to thin-film microcrystalline Si solar cells

    International Nuclear Information System (INIS)

    Koida, Takashi; Sai, Hitoshi; Kondo, Michio

    2010-01-01

    Hydrogen-doped In 2 O 3 (IO:H) films with high electron mobility and improved near-infrared (NIR) transparency have been applied as a transparent conducting oxide (TCO) electrode in substrate-type hydrogenated microcrystalline silicon (μc-Si:H) solar cells. The incorporation of IO:H, instead of conventional Sn-doped In 2 O 3 , improved the short-circuit current density (J sc ) and the resulting conversion efficiency. Optical analysis of the solar cells and TCO films revealed that the improvement in J sc is due to the improved spectral sensitivity in the visible and NIR wavelengths by reduction of absorption loss caused by free carriers in the TCO films.

  5. Dopant induced variations in microstructure and optical properties of CeO2 nanoparticles

    International Nuclear Information System (INIS)

    Mohanty, Bhaskar Chandra; Lee, Jong Won; Yeon, Deuk-Ho; Jo, Yeon-Hwa; Kim, Jong Hak; Cho, Yong Soo

    2011-01-01

    Research highlights: → Dopant (Zr 4+ , La 3+ , and Ca 2+ ) induced phase stability, and changes in microstructure and optical properties of CeO 2 nanoparticles have been studied. → The nanoparticles were prepared by hydrothermal synthesis of nitrate solutions. → The results show modification of the unit cell parameter by -0.39, +0.83 and +0.16% for doping of 20% Zr 4+ , La 3+ , and Ca 2+ , respectively. → For each batch prepared, nanoparticles with a narrow size distribution of 5-15 nm have been obtained. These particles are single crystals mostly having polygonal two-dimensional projections. → UV-visible spectra of doped particles exhibit shift of the absorption edge and absorption peak with respect to those of the undoped ones and has been attributed to compensation of Ce 3+ and decreasing crystallite size as result of doping. -- Abstract: Nanocrystalline CeO 2 particles doped in the range of 0-20% of Ca 2+ , La 3+ , and Zr 4+ have been prepared from hydrothermal synthesis of nitrate solutions at 200 o C and the influences of the dopants on microstructure and optical properties of the nanoparticles have been investigated. The unit cell parameter is found to be modified by -0.39, +0.83 and +0.16% for doping of 20% Zr 4+ , La 3+ , and Ca 2+ , respectively. For each batch prepared, nanoparticles with a narrow size distribution of 5-15 nm have been obtained. A high-resolution transmission electron microscopy investigation reveals that these particles are single crystals mostly having hexagonal, square or circular two-dimensional projections. UV-visible spectra of doped powders exhibit shift of the absorption edge and absorption peak with respect to those of the undoped CeO 2 particles and has been attributed to compensation of Ce 3+ and decreasing crystallite size as result of doping.

  6. An insight into the dopant selection for CeO2-based resistive-switching memory system: a DFT and experimental study

    Science.gov (United States)

    Hussain, Fayyaz; Imran, Muhammad; Rana, Anwar Manzoor; Khalil, R. M. Arif; Khera, Ejaz Ahmad; Kiran, Saira; Javid, M. Arshad; Sattar, M. Atif; Ismail, Muhammad

    2018-03-01

    The aim of this study is to figure out better metal dopants for CeO2 for designing highly efficient non-volatile memory (NVM) devices. The present DFT work involves four different metals doped interstitially and substitutionally in CeO2 thin films. First principle calculations involve electron density of states (DOS) and partial density of states (PDOS), and isosurface charge densities are carried out within the plane-wave density functional theory using GGA and GGA + U approach by employing the Vienna ab initio simulation package VASP. Isosurface charge density plots confirmed that interstitial doping of Zr and Ti metals truly assists in generating conduction filaments (CFs), while substitutional doping of these metals cannot do so. Substitutional doping of W may contribute in generating CFs in CeO2 directly, but its interstitial doping improves conductivity of CeO2. However, Ni-dopant is capable of directly generating CFs both as substitutional and interstitial dopants in ceria. Such a capability of Ni appears acting as top electrode in Ni/CeO2/Pt memory devices, but its RS behavior is not so good. On inserting Zr layer to make Ni/Zr:CeO2/Pt memory stacks, Ni does not contribute in RS characteristics, but Zr plays a vital role in forming CFs by creating oxygen vacancies and forming ZrO2 interfacial layer. Therefore, Zr-doped devices exhibit high-resistance ratio of 104 and good endurance as compared to undoped devices suitable for RRAM applications.

  7. ROS mediated malignancy cure performance of morphological, optical, and electrically tuned Sn doped CeO2 nanostructures

    Science.gov (United States)

    Abbas, Fazal; Iqbal, Javed; Maqbool, Qaisar; Jan, Tariq; Ullah, Muhammad Obaid; Nawaz, Bushra; Nazar, Mudassar; Naqvi, M. S. Hussain; Ahmad, Ishaq

    2017-09-01

    To grapple with cancer, implementation of differentially cytotoxic nanomedicines have gained prime attention of the researchers across the globe. Now, ceria (CeO2) at nanoscale has emerged as a cut out therapeutic agent for malignancy treatment. Keeping this in view, we have fabricated SnxCe1-xO2 nanostructures by facile, eco-friendly, and biocompatible hydrothermal method. Structural examinations via XRD and FT-IR spectroscopy have revealed single phase cubic-fluorite morphology while SEM analysis has depicted particle size ranging 30-50nm for pristine and doped nanostructures. UV-Vis spectroscopy investigation explored that Sn doping significantly tuned the band gap (eV) energies of SnxCe1-xO2 nanostructures which set up the base for tremendous cellular reactive oxygen species (ROS) generations involved in cancer cells' death. To observe cytotoxicity, synthesized nanostructures were found selectively more toxic to neuroblastoma cell lines as compared to HEK-293 healthy cells. This study anticipates that SnxCe1-xO2 nanostructures, in future, might be used as nanomedicine for safer cancer therapy.

  8. ROS mediated malignancy cure performance of morphological, optical, and electrically tuned Sn doped CeO2 nanostructures

    Directory of Open Access Journals (Sweden)

    Fazal Abbas

    2017-09-01

    Full Text Available To grapple with cancer, implementation of differentially cytotoxic nanomedicines have gained prime attention of the researchers across the globe. Now, ceria (CeO2 at nanoscale has emerged as a cut out therapeutic agent for malignancy treatment. Keeping this in view, we have fabricated SnxCe1-xO2 nanostructures by facile, eco-friendly, and biocompatible hydrothermal method. Structural examinations via XRD and FT-IR spectroscopy have revealed single phase cubic-fluorite morphology while SEM analysis has depicted particle size ranging 30-50nm for pristine and doped nanostructures. UV-Vis spectroscopy investigation explored that Sn doping significantly tuned the band gap (eV energies of SnxCe1-xO2 nanostructures which set up the base for tremendous cellular reactive oxygen species (ROS generations involved in cancer cells’ death. To observe cytotoxicity, synthesized nanostructures were found selectively more toxic to neuroblastoma cell lines as compared to HEK-293 healthy cells. This study anticipates that SnxCe1-xO2 nanostructures, in future, might be used as nanomedicine for safer cancer therapy.

  9. Defect Study of MgO-CaO Material Doped with CeO2

    Directory of Open Access Journals (Sweden)

    Han Zhang

    2013-01-01

    Full Text Available MgO-CaO refractories were prepared using analytical reagent chemicals of Ca(OH2 and Mg(OH2 as starting materials and CeO2 as dopant, then sintered at 1650°C for 3 h. The effect of CeO2 powders on the defect of MgO-CaO refractories was investigated. The sample characterizations were analyzed by the techniques of XRD and SEM. According to the results, with the addition of CeO2, the lattice constant of CaO increased, and the bulk density of the samples increased while apparent porosity decreased. The densification of MgO-CaO refractories was promoted obviously. In the sintering process, MgO grains grew faster than CaO, pores at the MgO-CaO grain boundaries decreased while pores in the MgO grains increased gradually, and no pores were observed in the CaO grains. The nature of the CeO2 promoting densification lies in the substitution and solution with CaO. Ce4+ approaches into CaO lattices, which enlarges the vacancy concentration of Ca2+ and accelerates the diffusion of Ca2+.

  10. Spray deposited CeO2–TiO2 counter electrode for electrochromic ...

    Indian Academy of Sciences (India)

    Abstract. 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. Precur- sor solution containing cerium nitrate hexahydrate (Ce(NO3)2·6H2O) and titanium ...

  11. Luminescent and morphological study of Sr2CeO4 blue phosphor prepared from oxalate precursors

    International Nuclear Information System (INIS)

    Ferrari, Jefferson L.; Pires, Ana M.; Serra, Osvaldo A.; Davolos, Marian R.

    2011-01-01

    Luminescent and morphological studies of Sr 2 CeO 4 blue phosphor prepared from cerium-doped strontium oxalate precursor are reported. Powder samples were prepared from 5 and 25 mol% Ce 3+ -doped strontium oxalate as well as from a mechanical mixture of strontium oxalate and cerium oxalate at a 4:1 ratio, respectively. All the samples were characterized by XRD, IR, PLS, and SEM. The luminescent and structural properties of the Sr 2 CeO 4 material are little affected by the SrCO 3 remaining from precursors. The Sr 2 CeO 4 material consists in one-dimensional chains of edge-sharing CeO 6 octahedra that are linked together by Sr 2+ ions. The carbonate ion might be associated with oxygen ions of the linear chain, and also with the oxygen atoms located in the equatorial position, which consequently affects the charge transfer bands between O 2- and Ce 4+ . As observed by SEM, the morphological changes are related to each kind of precursor and thermal treatment, along with irregular powder particles within the size range 0.5-2 μm.

  12. Far-infrared spectroscopic study of CeO2 nanocrystals

    Science.gov (United States)

    Popović, Z. V.; Grujić-Brojčin, M.; Paunović, N.; Radonjić, M. M.; Araújo, V. D.; Bernardi, M. I. B.; de Lima, M. M.; Cantarero, A.

    2015-01-01

    We present the far-infrared reflectivity spectra of 5 nm-sized pure and copper-doped Ce1- x Cu x O2- 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 E u 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 E u 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 F 2uinfrared-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.

  13. Hydrogen storage properties of the Zintl phase alloy SrAl{sub 2} doped with TiF{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Yunfeng, E-mail: yfzhu@njut.edu.c [College of Materials Science and Engineering, Nanjing University of Technology, 5 Xinmofan Road, Nanjing 210009 (China); Zhang Wei; Liu Zhibing; Li Liquan [College of Materials Science and Engineering, Nanjing University of Technology, 5 Xinmofan Road, Nanjing 210009 (China)

    2010-03-04

    In this paper, the structural and hydrogenation characteristics of TiF{sub 3}-doped Zintl phase alloy SrAl{sub 2} were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and hydrogenation measurements. The results show that the hydrogenation kinetics of the Zintl phase alloy SrAl{sub 2} is improved greatly after doping with TiF{sub 3}. By adjusting the doping amount and ball milling time, the optimal doping conditions were obtained. The catalytic mechanism of TiF{sub 3} for the hydrogenation of SrAl{sub 2} was also investigated. SrAl{sub 2} does not react with TiF{sub 3} during the ball milling process. However, it reacts with TiF{sub 3} to form SrAl{sub 2}H{sub 2}, SrF{sub 2}, SrAl{sub 4} and Ti during the hydrogenation process, among which Ti plays an important role in the hydrogenation kinetics of SrAl{sub 2}.

  14. High power density cell using nanostructured Sr-doped SmCoO3 and Sm-doped CeO2 composite powder synthesized by spray pyrolysis

    Science.gov (United States)

    Shimada, Hiroyuki; Yamaguchi, Toshiaki; Suzuki, Toshio; Sumi, Hirofumi; Hamamoto, Koichi; Fujishiro, Yoshinobu

    2016-01-01

    High power density solid oxide electrochemical cells were developed using nanostructure-controlled composite powder consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) for electrode material. The SSC-SDC nano-composite powder, which was synthesized by spray pyrolysis, had a narrow particle size distribution (D10, D50, and D90 of 0.59, 0.71, and 0.94 μm, respectively), and individual particles were spherical, composing of nano-size SSC and SDC fragments (approximately 10-15 nm). The application of the powder to a cathode for an anode-supported solid oxide fuel cell (SOFC) realized extremely fine cathode microstructure and excellent cell performance. The anode-supported SOFC with the SSC-SDC cathode achieved maximum power density of 3.65, 2.44, 1.43, and 0.76 W cm-2 at 800, 750, 700, and 650 °C, respectively, using humidified H2 as fuel and air as oxidant. This result could be explained by the extended electrochemically active region in the cathode induced by controlling the structure of the starting powder at the nano-order level.

  15. Far-infrared spectroscopic study of CeO2 nanocrystals

    International Nuclear Information System (INIS)

    Popović, Z. V.; Grujić-Brojčin, M.; Paunović, N.; Radonjić, M. M.; Araújo, V. D.; Bernardi, M. I. B.; Lima, M. M. de; Cantarero, A.

    2015-01-01

    We present the far-infrared reflectivity spectra of 5 nm-sized pure and copper-doped Ce 1−x Cu x O 2−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 CeO 2 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 E u 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 E u 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 F 2u infrared-active mode in the far-infrared reflectivity spectra, is a consequence of the nanosized dimension of the CeO 2 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

  16. Dose-Dependent Effects of CeO2 on Microstructure and Antibacterial Property of Plasma-Sprayed TiO2 Coatings for Orthopedic Application

    Science.gov (United States)

    Zhao, Xiaobing; Liu, Gaopeng; Zheng, Hai; Cao, Huiliang; Liu, Xuanyong

    2015-02-01

    Titanium and its alloys have been used extensively for orthopedic and dental implants. Although these devices have achieved high rates of success, two major complications may be encountered: the lack of osseointegration and the biomaterial-related infection. Accordingly, cerium oxide (CeO2)-doped titanium oxide (TiO2) materials were coated on titanium by an atmospheric plasma spraying (APS) technique. The phase structures, morphologies, and surface chemical states of the obtained coatings were characterized by x-ray diffraction, scanning electron microscopy, and x-ray photoelectron spectroscopy techniques. The in vitro antibacterial and cytocompatibility of the materials were studied with Staphylococcus aureus ( S. aureus, ATCC25923) and osteoblast precursor cell line MC3T3-E1. The results indicated that the addition of CeO2 shifts slightly the diffraction peaks of TiO2 matrix to low angles but does not change its rutile phase structure. In addition, the CeO2/TiO2 composite coatings possess dose-dependent corrosion resistance and antimicrobial properties. And doping of 10 wt.% CeO2 exhibits the highest activity against S. aureus, improved corrosion resistance, and competitive cytocompatibility, which argues a promising option for balancing the osteogenetic and antibacterial properties of titanium implants.

  17. Superior hydrogen storage kinetics of MgH2 nanoparticles doped with TiF3

    International Nuclear Information System (INIS)

    Xie, L.; Liu, Y.; Wang, Y.T.; Zheng, J.; Li, X.G.

    2007-01-01

    MgH 2 nanoparticles were obtained by hydriding ultrafine magnesium particles which were prepared by hydrogen plasma-metal reaction. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the obtained sample is almost pure MgH 2 phase, without residual magnesium and with an average particle size of ∼300 nm. Milled with 5 wt.% TiF 3 as a doping precursor in a hydrogen atmosphere, the sample desorbed 4.5 wt.% hydrogen in 6 min under an initial hydrogen pressure of ∼0.001 bar at 573 K and absorbed 4.2 wt.% hydrogen in 1 min under ∼20 bar hydrogen at room temperature. Compared with MgH 2 micrometer particles doped with 5 wt.% TiF 3 under the same conditions as the MgH 2 nanoparticles, it is suggested that decrease of particle size is beneficial for enhancing absorption capacity at low temperatures, but has no effect on desorption. In addition, the catalyst was mainly responsible for improving the sorption kinetics and its catalytic mechanism is discussed

  18. Eu and Sr2CeO4 : Eu phosphors suitable for near ultraviolet excitation

    Indian Academy of Sciences (India)

    Administrator

    The study on white light phosphors suitable for near- ultraviolet (nUV) ... Rare earth ion-doped phosphors have been used in varied fields ... practical applications. .... by naked eyes. ... induced by Sr2CeO4 host matrix (Arunachalam Laxmanan.

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

    Science.gov (United States)

    Zenerino, Arnaud; Boutard, Tifenn; Bignon, Cécile; Amigoni, Sonia; Josse, Denis; Devers, Thierry; Guittard, Frédéric

    2015-01-01

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

  20. Synthesis of cerium and nickel doped titanium nanofibers for hydrolysis of sodium borohydride.

    Science.gov (United States)

    Tamboli, Ashif H; Gosavi, S W; Terashima, Chiaki; Fujishima, Akira; Pawar, Atul A; Kim, Hern

    2018-07-01

    A recyclable titanium nanofibers, doped with cerium and nickel doped was successfully synthesized by using sol-gel and electrospinning method for hydrogen generation from alkali free hydrolysis of NaBH 4 . The resultant nanocomposite was characterized to find out the structural and physical-chemical properties by a series of analytical techniques such as FT-IR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), SEM (scanning electron microscope), EDX (energy-dispersive X-ray spectroscopy),N 2 adsorption-desorption and BET (Brunauer-Emmett-Teller), etc. The results revealed that cerium and nickel nanoparticles were homogeneously distributed on the surface of the TiO 2 nanofibers due to having similar oxidation state and atomic radium of TiO 2 nanofibers with CeO 2 and NiO for the effective immobilization of metal ions. The NiO doped catalyst showed superior catalytic performance towards the hydrolysis reaction of NaBH 4 at room temperature. These catalysts have ability to produce 305 mL of H 2 within the time of 160 min at room temperature. Additionally, reusability test revealed that the catalyst is active even after five runs of hydrolytic reaction, implying the as-prepared NiO doped TiO 2 nanofibers could be considered as a potential candidate catalyst for portable hydrogen fuel system such as PEMFC (proton exchange membrane fuel cells). Copyright © 2018 Elsevier Ltd. All rights reserved.

  1. Mn-doped NiP2 nanosheets as an efficient electrocatalyst for enhanced hydrogen evolution reaction at all pH values

    Science.gov (United States)

    Wang, Xiaodeng; Zhou, Hongpeng; Zhang, Dingke; Pi, Mingyu; Feng, Jiajia; Chen, Shijian

    2018-05-01

    Developing stable and high-efficiency hydrogen generation electrocatalysts, particularly for the cathode hydrogen evolution reaction (HER), is an urgent challenge in energy conversion technologies. In this work, we have successfully synthesized Mn-doped NiP2 nanosheets on carbon cloth (Mn-NiP2 NSs/CC), which behaves as a higher efficient three dimensional HER electrocatalyst with better stability at all pH values than pure NiP2. Electrochemical tests demonstrate that the catalytic activity of NiP2 is enhanced by Mn doping. In 0.5 M H2SO4, this Mn-NiP2 NSs/CC catalyst drives 10 mA cm-2 at an overpotential of 69 mV, which is 20 mV smaller than pure NiP2. To achieve the same current density, it demands overpotentials of 97 and 107 mV in 1.0 M KOH and phosphate-buffered saline (PBS), respectively. Compared with pure NiP2, higher HER electrocatalytic performance for Mn-NiP2 NSs/CC can be attributed to its lower thermo-neutral hydrogen adsorption free energy, which is supported by density functional theory calculations.

  2. Hydrogen Solubility in Pr-doped and Un-doped YSZ for One Chamber Fuel Cell

    DEFF Research Database (Denmark)

    Bay, Lasse; Horita, T.; Sakai, N.

    1998-01-01

    SIMS analysis. Doping of Pr in the YSZ resulted in a higher intensity of the D ion, which indicated that hydrogen solubility was raised by the doping. The solubility of hydrogen in the electrolyte may affect the performance of one chamber fuel cells. (C) 1998 Elsevier Science B.V. All rights reserved.......Yttria-stabilised zirconia electrolytes (YSZ and Pr-doped YSZ) and yttria-doped strontium cerate (SYC) were tested in a one chamber fuel cell fed with a mixture of methane and air at 1223 K. The obtained performances were 4 mW cm(-2), 3 mW cm(-2), 2.5 mW cm(-2), and 0.15 mW cm(-2) for SYC, 1.8 mol...

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

    Directory of Open Access Journals (Sweden)

    Arnaud Zenerino

    2015-01-01

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

  4. Hydrogen storage capacity of lithium-doped KOH activated carbons

    International Nuclear Information System (INIS)

    Minoda, Ai; Oshima, Shinji; Iki, Hideshi; Akiba, Etsuo

    2014-01-01

    Highlights: • The hydrogen adsorption of lithium-doped KOH activated carbons has been studied. • Lithium doping improves their hydrogen adsorption affinity. • Lithium doping is more effective for materials with micropores of 0.8 nm or smaller. • Lithium reagent can alter the pore structure, depending on the raw material. • Optimizing the pore size and functional group is needed for better hydrogen uptake. - Abstract: The authors have studied the hydrogen adsorption performance of several types of lithium-doped KOH activated carbons. In the case of activated cokes, lithium doping improves their hydrogen adsorption affinity from 5.02 kg/m 3 to 5.86 kg/m 3 at 303 K. Hydrogen adsorption density increases by around 17% after lithium doping, likely due to the fact that lithium doping is more effective for materials with micropores of 0.8 nm or smaller. The effects of lithium on hydrogen storage capacity vary depending on the raw material, because the lithium reagent can react with the material and alter the pore structure, indicating that lithium doping has the effect of plugging or filling the micropores and changing the structures of functional groups, resulting in the formation of mesopores. Despite an observed decrease in hydrogen uptake, lithium doping was found to improve hydrogen adsorption affinity. Lithium doping increases hydrogen uptake by optimizing the pore size and functional group composition

  5. CeO2-ZrO2 ceramic compounds

    International Nuclear Information System (INIS)

    Melo, F.C.L.; Cairo, C.A.C.; Devezas, T.C.; Nono, M.C.A.

    1988-01-01

    In order to study the mechanical properties of tetragonal polycrystal zirconia stabilized with ceria various powder compositions with different CeO 2 content were made. Modulus of rupture for those compounds was measured. Tetragonal retained phase was determined for samples of CeO 2 -ZrO 2 ceramics with and without superficial mechanical treatment. The experimental results allowed us to evaluate the effects of CeO 2 content and sintering temperature in the mechanical properties and tetragonal transformed phase (t→ m) in ceramics of CeO 2 -ZrO 2 systems. (author) [pt

  6. Role of CeO2 promoter in NiO/α-Al2O3 catalyst for dry reforming of methane

    Science.gov (United States)

    Loc, Luu Cam; Phuong, Phan Hong; Tri, Nguyen

    2017-09-01

    A series of Ni/α-Al2O3 (NiAl) catalysts promoted by CeO2 was prepared by co-impregnation methods with content of (NiO+CeO2) being in the range of 10-30 wt%. The NiO:CeO2 weight ratio was fluctuated at 1:1, 1:2 and 1:3. Several techniques, including X-ray powder diffraction (XRD), Hydrogen temperature-programmed reduction (H2-TPR), and transmission electron microscopy (TEM) were used to investigate catalysts' physico-chemical properties. The activity of these catalysts in dry reforming of CH4 was investigated at temperature range of 550-800 °C. The results revealed that the most suitable CeO2 promoted Ni catalyst contained 20 wt% of (NiO+CeO2) and NiO:CeO2 weight ratio of 1:2. The best catalytic performance of catalyst [20(1Ni2Ce)Al] due to a better reducibility resulted in a higher amount of free small particle NiO. At 700 °C and CH4:CO2 molar ratio of 1:1, the conversion of CH4 and CO2 on the most suitable CeO2 promoted Ni catalyst reached 86% and 67%, respectively; H2 and CO selectivity of 90% and H2:CO molar ratio of 1.15 were obtained. Being similar to MgO [1], promoter CeO2 could improve catalytic activity of Ni/α-Al2O3 catalyst at a lower range of temperature. Besides, both MgO and CeO2 had a great impact on improving coke resistance of Ni catalysts. At higher temperature, the role of CeO2 as well as MgO in preventing coke formation on catalyst was clarified by temperature-programmed oxidation (TPO) technique. Coke amount formed after 30-h TOS on 20(1Ni2Ce) catalyst was found to be 22.18 mgC/gcat, being less than on non-promoted catalyst (36.75 mgC/gcat), but more than on 20(1Ni2Mg)Al one (5.25 mgC/gcat).

  7. Solid state speciation of uranium and its local structure in Sr2CeO4 using photoluminescence spectroscopy

    Science.gov (United States)

    Sahu, M.; Gupta, Santosh K.; Jain, D.; Saxena, M. K.; Kadam, R. M.

    2018-04-01

    An effort was taken to carry our speciation study of uranium ion in technologically important cerate host Sr2CeO4 using time resolved photoluminescence spectroscopy. Such studies are not relevant only to nuclear industry but can give rich insight into fundamentals of 5f electron chemistry in solid state systems. In this work both undoped and varied amount of uranium doped Sr2CeO4 compound is synthesized using complex polymerization method and is characterized systematically using X-ray diffraction (XRD), Raman spectroscopy, photoluminescence spectroscopy and scanning electron microscopy (SEM). Both XRD and Raman spectroscopy confirmed the formation of pure Sr2CeO4 which has tendency to decompose peritectically to SrCeO3 and SrO at higher temperature. Uranium doping is confirmed by XRD. Uranium exhibits a rich chemistry owing to its variable oxidation state from +3 to +6. Each of them exhibits distinct luminescence properties either due to f-f transitions or ligand to metal charge transfer (LMCT). We have taken Sr2CeO4 as a model host lattice to understand the photophysical characteristics of uranium ion in it. Emission spectroscopy revealed the stabilization of uranium as U (VI) in the form of UO66- (octahedral uranate) in Sr2CeO4. Emission kinetics study reflects that uranate ions are not homogeneously distributed in Sr2CeO4 and it has two different environments due to its stabilization at both Sr2+ as well as Ce4+ site. The lifetime population analysis interestingly pinpointed that majority of uranate ion resided at Ce4+ site. The critical energy-transfer distance between the uranate ion was determined based on which the concentration quenching mechanism was attributed to electric multipolar interaction. These studies are very important in designing Sr2CeO4 based optoelectronic material as well exploring it for actinides studies.

  8. Promoting effect of CeO 2 on cyclohexanol conversion over CeO 2

    Indian Academy of Sciences (India)

    Abstract. CeO2-ZnO materials were prepared by amorphous citrate process and characterized by TGA, XRD, UV-DRS and surface area measurements. TGA showed that the citrate precursors decompose in the range 350-550°C producing CeO2-containing catalytic materials. XRD and DRS results indicated the formation of ...

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

    International Nuclear Information System (INIS)

    Venkatesh; Sathgatta Z, M. S.; Manjunatha, S.; Thammannigowda V, V.

    2014-01-01

    This study investigates the use of CeO 2 , ZrO 2 , Mg O and CeO 2 -ZrO 2 , CeO 2 -Mg O, CeO 2 -ZrO 2 -Mg O mixed oxides as solid base catalysts for the transesterification of Pongamia pinnata oil with methanol to produce bio diesel. SO 4 2- /CeO 2 and SO 4 2- /CeO 2 -ZrO 2 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 NH 3 -Tpd for surface acidity, CO 2 -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 CeO 2 -ZrO 2 modified with Mg O could have potential for use in the large scale bio diesel production. (Author)

  10. Superior hydrogen storage kinetics of MgH{sub 2} nanoparticles doped with TiF{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Xie, L. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Liu, Y. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Wang, Y.T. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Zheng, J. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Li, X.G. [Beijing National Laboratory for Molecular Sciences (BNLMS), State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China) and College of Engineering, Peking University, Beijing 100871 (China)]. E-mail: xgli@pku.edu.cn

    2007-08-15

    MgH{sub 2} nanoparticles were obtained by hydriding ultrafine magnesium particles which were prepared by hydrogen plasma-metal reaction. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results show that the obtained sample is almost pure MgH{sub 2} phase, without residual magnesium and with an average particle size of {approx}300 nm. Milled with 5 wt.% TiF{sub 3} as a doping precursor in a hydrogen atmosphere, the sample desorbed 4.5 wt.% hydrogen in 6 min under an initial hydrogen pressure of {approx}0.001 bar at 573 K and absorbed 4.2 wt.% hydrogen in 1 min under {approx}20 bar hydrogen at room temperature. Compared with MgH{sub 2} micrometer particles doped with 5 wt.% TiF{sub 3} under the same conditions as the MgH{sub 2} nanoparticles, it is suggested that decrease of particle size is beneficial for enhancing absorption capacity at low temperatures, but has no effect on desorption. In addition, the catalyst was mainly responsible for improving the sorption kinetics and its catalytic mechanism is discussed.

  11. Potassium doped MWCNTs for hydrogen storage enhancement

    International Nuclear Information System (INIS)

    Adabi Qomi, S.; Gashtasebi, M.; Khoshnevisan, B.

    2012-01-01

    Here we have used potassium doped MWCNTs for enhancement of hydrogen storage process. XRD and SEM images have confirmed the doping of potassium. For studying the storage process a hydrogenic battery set up has been used. In the battery the working electrode has been made of the silver foam deposited by the doped MWCNTs electrophoretically.

  12. CO2 methanation on the catalyst of Ni/MCM-41 promoted with CeO2.

    Science.gov (United States)

    Wang, Xiaoliu; Zhu, Lingjun; Liu, Yincong; Wang, Shurong

    2018-06-01

    CO 2 as a raw feed combined with renewable hydrogen for the production of useful chemicals and alternative energy products is one of the solutions to environmental and energy problems. In this study, a series of Ni-xCeO 2 /MCM-41 catalysts with a nickel content of 20wt% were prepared through deposition precipitation method for CO 2 methanation. Different characterization methods, including BET, XRD, TEM, SEM, H 2 -TPR and H 2 -TPD were applied to help explore the influence mechanism of CeO 2 on Ni/MCM-41 in CO 2 methanation. It was found that all CeO 2 -promoted catalysts exhibited enhanced catalytic activity when compared to Ni/MCM-41. The catalyst modified with 20wt% CeO 2 showed the best catalytic performance, with CO 2 conversion and CH 4 selectivity of 85.6% and 99.8%, respectively, at the temperature of 380°C under atmospheric pressure. The synergetic effects among Ni 0 active sites, the promoter and the support, including nickel dispersion improvement and increased CO 2 adsorption sites due to the addition of CeO 2 , were considered as important factors for high reactivity of the promoted catalysts. The stability test showed that the promoted catalyst maintained its high reactivity after 30h. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Chemiluminescent Diagnostics of Free-Radical Processes in an Abiotic System and in Liver Cells in the Presence of Nanoparticles Based on Rare-Earth Elements nReVO4:Eu3+ (Re = Gd, Y, La) and CeO2

    Science.gov (United States)

    Averchenko, E. A.; Kavok, N. S.; Klochkov, V. K.; Malyukin, Yu. V.

    2014-11-01

    We have used luminol-dependent chemiluminescence with Fenton's reagent to study the effect of nanoparticles based on rare-earth elements of different sizes and shapes on free-radical processes in abiotic and biotic cell-free systems, and also in isolated cells in vitro. We have estimated the effects of rare-earth orthovanadate nanoparticles of spherical (GdYVO4:Eu3+, 1-2 nm), spindle-shaped (GdVO4:Eu3+, 25 ×8 nm), and rod-shaped (LaVO4:Eu3+, 57 × (6-8) nm) nanoparticles and spherical CeO2 nanoparticles (sizes 1-2 nm and 8-10 nm). We have shown that in contrast to the abiotic system, in which all types of nanoparticles exhibit antiradical activity, in the presence of biological material, extra-small spherical (1-2 nm) nanoparticles of both types exhibit pro-oxidant activity, and also enhance pro-oxidant induced oxidative stress (for the pro-oxidants hydrogen peroxide and tert-butyl hydroperoxide). The effect of rare-earth orthovanadate spindle and rod shaped nanoparticles in this system was neutral; a moderate antioxidant effect was exhibited by 8-10 nm CeO2 nanoparticles.

  14. Synthesis and characterization of Sr2CeO4: Eu3+ phosphor by different forms

    International Nuclear Information System (INIS)

    Murthy, K.V.R.; Rao, Ch. Atchyutha; Suresh, K.; Ratna Kumar, B.W.; Nageswara Rao, B.; Poornachandra Rao, N.V.; Subba Rao, B.

    2011-01-01

    High temperature solid state reaction method was explored to synthesize undoped Sr 2 CeO 4 and Eu 3+ RE doped Sr 2 CeO 4 phosphor using inorganic materials taking in three different forms like, form (i) Strontium Carbonate (SrCO 3 ), Cerium Oxide (CeO 2 ), (ii) Strontium Nitrate (Sr(NO 3 ) 2 ), Cerium Oxide (CeO 2 ) and (iii) Strontium Nitrate (Sr(NO 3 ) 2 ), Cerium Nitrate (Ce(NO 3 ) 3 .6(NH 2 .CO.NH 2 ) in stoichiometric proportions of Sr:Ce as 2:1 and ground into a fine powder using agate mortar and pestle about an hour. The grounded samples were placed in an alumina crucible and fired at 1200 deg C for 3 hours in a muffle furnace with a heating rate of 5 deg C/min. To investigate the crystal structure, phase, morphology and luminescent properties of the synthesized phosphors XRD, SEM, Photoluminescence (PL) spectra, TL and CIE techniques were used. The Photoluminescence (PL) emission and excitation spectra were measured by Spectrofluorophotometer (SHIMADZU, RF-5301 PC) using Xenon lamp as excitation source. To identify the crystal phase, XRD analysis was carried out with a powder diffractometer (Rigaku-D/max 2500) using CuKα radiation. The microstructures of the samples were studied using a scanning electron microscopy (SEM) (XL 30 CP Philips). All the analysis was recorded at room temperature. We have compared the results of the prepared samples by different forms. From the XRD analysis it was found that the prepared phosphors are mostly in single phase of Sr 2 CeO 4 with an orthorhombic structure. From the XRD data, using Scherrer's formula the calculated average crystallite size is (i) ∼ 28 nm (ii) ∼ 9 nm (iii) ∼ 7 nm using FWHM. This indicates that, the prepared phosphors via high temperature solid state reaction method is in nano size. Sr 2 CeO 4 exhibits photoluminescence due to the charge transfer (CT) mechanism. The sample displays a broad excitation spectrum range from ∼ 220 to 400 nm. Under 350 nm excitation, the undoped Sr 2 CeO 4 shows

  15. Boron-doped hydrogenated Al{sub 3} clusters: A material for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Muz, İskender, E-mail: iskender.muz@nevsehir.edu.tr [Faculty of Education, Department of Science Education, Nevsehir Haci Bektas Veli University, 50300, Nevsehir (Turkey); Atiş, Murat [Kayseri Vocational School, Electricity and Energy Department, Erciyes University, 38300, Kayseri (Turkey)

    2016-05-15

    The energetic and structural stabilities of Al{sub 3}BH{sub 2n} (n = 0–6) clusters are investigated using ab initio calculations. Structural isomers are found using the stochastic search method to search for minima structures, followed by B3LYP optimizations; single-point CCSD(T) calculations are performed to compute relative energies. Chemical bonding analysis is also performed using the adaptive natural density partitioning method to investigate the chemical bonding in the clusters and to elucidate their structural evolution. Our results and analyses indicate that the stability of the boron-doped hydrogenated Al{sub 3} clusters increases as more hydrogen molecules are adsorbed, whereas the H{sub 2} loss energy decreases. The results are in good agreement with available theoretical findings. - Highlights: • The boron-doped hydrogenated Al{sub 3} clusters are generated using stochastic search method. • The energetic and structural stabilities are investigated in detail. • The chemical bonding analysis is performed by using AdNDP analysis. • The doping by boron allows development of better aluminum-based metal hydrides.

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

    DEFF Research Database (Denmark)

    Omar, Shobit; Bonanos, Nikolaos

    2010-01-01

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

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

    International Nuclear Information System (INIS)

    Huang Jianping; Li Yibin; He Xiaodong; Song Guangping; Fan Chenglei; Sun Yue; Fei Weidong; Du Shanyi

    2012-01-01

    Highlights: ► Cauliflower-like microstructured CeO 2 coating is prepared on Ni based substrate. ► The infrared emissive property at high temperature is investigated. ► Rough CeO 2 coating shows high emissivity, that is, 0.9 at 873 K and 0.87 at 1073 K. ► The emissivity enhancement mechanisms for the rough CeO 2 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 CeO 2 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.

  18. Hydrogen adsorption in doped porous carbons

    International Nuclear Information System (INIS)

    L Balan; L Duclaux; S Los

    2005-01-01

    Full text of publication follows: Hydrogen is a clean fuel that will be used in automotive transport when the problem of storage will be solved. The difficulties of H 2 storage (available space, security and performance, etc...) require a material that can store 5 weight % of hydrogen. Research is focused on new materials that can assume the constraints imposed by the automotive applications. Among these materials, the nano-structured carbons (nano-fibers and single walled carbon nano-tubes) were claimed to be promising by numerous authors [1-3]. The more promising carbon materials for hydrogen adsorption are those having micropores (i. e. single walled carbon nano-tubes and activated carbon), for which the energy of sorption of hydrogen molecules is theoretically higher [7-8]. Presently, the best performance of hydrogen adsorption was found in super-activated microporous carbons sorbing 5 weight % at 77 K, and almost 0.5 % at room temperature and 6 MPa [9]. Up to now, the performance of these materials can still be improved as the known mechanism of sorption in these carbon materials: physi-sorption controlled by Van der Waals attractive forces through London interaction is efficient at cryogenic temperatures (77 K) where the interaction between adsorbent and adsorbate becomes stronger. One way to improve the attractive interaction between adsorbent and molecule is to increase the forces due to the interaction of electrical field and induced dipole of the molecule. This can be theoretically tailored in carbon materials through the electron charge transfer by electron donors who can provide an increase in the electrical field at the surface of the adsorbent. Then, the doping of carbon substrates, appearing to be a promising method to increase the energy of adsorption has been proposed in recent papers as a solution to obtain good hydrogen adsorption properties at appropriate temperatures close to room temperatures [10-12]. Thus, we have studied the adsorption

  19. Hydrogen adsorption in doped porous carbons

    International Nuclear Information System (INIS)

    Balan, L.; Duchaux, L.; Los, S.

    2005-01-01

    Full text of publication follows: Hydrogen is a clean fuel that will be used in automotive transport when the problem of storage will be solved. The difficulties of H 2 storage (available space, security and performance, etc...) require a material that can store 5 weight % of hydrogen. Research is focused on new materials that can assume the constraints imposed by the automotive applications. Among these materials, the nano-structured carbons (nano-fibers and single walled carbon nano-tubes) were claimed to be promising by numerous authors [1-3]. The more promising carbon materials for hydrogen adsorption are those having micropores (i. e. single walled carbon nano-tubes and activated carbon), for which the energy of sorption of hydrogen molecules is theoretically higher [7- 8]. Presently, the best performance of hydrogen adsorption was found in super-activated micro-porous carbons sorbing 5 weight % at 77 K, and almost 0.5 % at room temperature and 6 MPa [9]. Up to now, the performance of these materials can still be improved as the known mechanism of sorption in these carbon materials: physisorption controlled by Van der Waals attractive forces through London interaction is efficient at cryogenic temperatures (77 K) where the interaction between adsorbent and adsorbate becomes stronger. One way to improve the attractive interaction between adsorbent and molecule is to increase the forces due to the interaction of electrical field and induced dipole of the molecule. This can be theoretically tailored in carbon materials through the electron charge transfer by electron donors who can provide an increase in the electrical field al the surface of the adsorbent. Then, the doping of carbon substrates, appearing to be a promising method to increase the energy of adsorption has been proposed in recent papers as a solution to obtain good hydrogen adsorption properties at appropriate temperatures close to room temperatures [10-12]. Thus, we have studied the adsorption

  20. Oxygen- and Lithium-Doped Hybrid Boron-Nitride/Carbon Networks for Hydrogen Storage.

    Science.gov (United States)

    Shayeganfar, Farzaneh; Shahsavari, Rouzbeh

    2016-12-20

    Hydrogen storage capacities have been studied on newly designed three-dimensional pillared boron nitride (PBN) and pillared graphene boron nitride (PGBN). We propose these novel materials based on the covalent connection of BNNTs and graphene sheets, which enhance the surface and free volume for storage within the nanomaterial and increase the gravimetric and volumetric hydrogen uptake capacities. Density functional theory and molecular dynamics simulations show that these lithium- and oxygen-doped pillared structures have improved gravimetric and volumetric hydrogen capacities at room temperature, with values on the order of 9.1-11.6 wt % and 40-60 g/L. Our findings demonstrate that the gravimetric uptake of oxygen- and lithium-doped PBN and PGBN has significantly enhanced the hydrogen sorption and desorption. Calculations for O-doped PGBN yield gravimetric hydrogen uptake capacities greater than 11.6 wt % at room temperature. This increased value is attributed to the pillared morphology, which improves the mechanical properties and increases porosity, as well as the high binding energy between oxygen and GBN. Our results suggest that hybrid carbon/BNNT nanostructures are an excellent candidate for hydrogen storage, owing to the combination of the electron mobility of graphene and the polarized nature of BN at heterojunctions, which enhances the uptake capacity, providing ample opportunities to further tune this hybrid material for efficient hydrogen storage.

  1. Doped phosphorene for hydrogen capture: A DFT study

    Science.gov (United States)

    Zhang, Hong-ping; Hu, Wei; Du, Aijun; Lu, Xiong; Zhang, Ya-ping; Zhou, Jian; Lin, Xiaoyan; Tang, Youhong

    2018-03-01

    Hydrogen capture and storage is the core of hydrogen energy application. With its high specific surface area, direct bandgap, and variety of potential applications, phosphorene has attracted much research interest. In this study, density functional theory (DFT) is utilized to study the interactions between doped phosphorenes and hydrogen molecules. The effects of different dopants and metallic or nonmetallic atoms on phosphorene/hydrogen interactions is systematically studied by adsorption energy, electron density difference, partial density of states analysis, and Hirshfeld population. Our results indicate that the metallic dopants Pt, Co, and Ni can help to improve the hydrogen capture ability of phosphorene, whereas the nonmetallic dopants have no effect on it. Among the various metallic dopants, Pt performs very differently, such that it can help to dissociate H2 on phosphorene. Specified doped phosphorene could be a promising candidate for hydrogen storage, with behaviors superior to those of intrinsic graphene sheet.

  2. New Pathways and Metrics for Enhanced, Reversible Hydrogen Storage in Boron-Doped Carbon Nanospaces

    Energy Technology Data Exchange (ETDEWEB)

    Pfeifer, Peter [University of Missouri; Wexler, Carlos [University of Missouri; Hawthorne, M. Frederick [University of Missouri; Lee, Mark W. [University of Missouri; Jalistegi, Satish S. [University of Missouri

    2014-08-14

    This project, since its start in 2007—entitled “Networks of boron-doped carbon nanopores for low-pressure reversible hydrogen storage” (2007-10) and “New pathways and metrics for enhanced, reversible hydrogen storage in boron-doped carbon nanospaces” (2010-13)—is in support of the DOE's National Hydrogen Storage Project, as part of the DOE Hydrogen and Fuel Cells Program’s comprehensive efforts to enable the widespread commercialization of hydrogen and fuel cell technologies in diverse sectors of the economy. Hydrogen storage is widely recognized as a critical enabling technology for the successful commercialization and market acceptance of hydrogen powered vehicles. Storing sufficient hydrogen on board a wide range of vehicle platforms, at energy densities comparable to gasoline, without compromising passenger or cargo space, remains an outstanding technical challenge. Of the main three thrust areas in 2007—metal hydrides, chemical hydrogen storage, and sorption-based hydrogen storage—sorption-based storage, i.e., storage of molecular hydrogen by adsorption on high-surface-area materials (carbons, metal-organic frameworks, and other porous organic networks), has emerged as the most promising path toward achieving the 2017 DOE storage targets of 0.055 kg H2/kg system (“5.5 wt%”) and 0.040 kg H2/liter system. The objective of the project is to develop high-surface-area carbon materials that are boron-doped by incorporation of boron into the carbon lattice at the outset, i.e., during the synthesis of the material. The rationale for boron-doping is the prediction that boron atoms in carbon will raise the binding energy of hydro- gen from 4-5 kJ/mol on the undoped surface to 10-14 kJ/mol on a doped surface, and accordingly the hydro- gen storage capacity of the material. The mechanism for the increase in binding energy is electron donation from H2 to electron-deficient B atoms, in the form of sp2 boron-carbon bonds. Our team is proud to have

  3. Atomic layer deposition of high-mobility hydrogen-doped zinc oxide

    NARCIS (Netherlands)

    Macco, B.; Knoops, H.C.M.; Verheijen, M.A.; Beyer, W.; Creatore, M.; Kessels, W.M.M.

    2017-01-01

    In this work, atomic layer deposition (ALD) has been employed to prepare high-mobility H-doped zinc oxide (ZnO:H) films. Hydrogen doping was achieved by interleaving the ZnO ALD cycles with H2 plasma treatments. It has been shown that doping with H2 plasma offers key advantages over traditional

  4. Promoting Effect of CeO2 Addition on Activity and Catalytic Stability in Steam Reforming of Methane over Ni/Al2O3

    International Nuclear Information System (INIS)

    Rakib, A.; Gennequin, C.; Ringot, S.; Aboukais, A.; Abi-Aad, E.; Dhainaut, T.

    2011-01-01

    Hydrogen production by steam reforming of methane was studied over Ni catalysts supported on CeO 2 , Al 2 O 3 and CeO 2 -Al 2 O 3 . These catalysts were prepared using the impregnation method and characterized by XRD. The effect of CeO2 promoter on the catalytic performance of Ni/Al 2 O 3 catalyst for methane steam reforming reaction was investigated. In fact, CeO 2 had a positive effect on the catalytic activity in this reaction. Experimental results demonstrated that Ni/CeO 2 -Al 2 O 3 catalyst showed excellent catalytic activity and high reaction performance. In addition, the effects of reaction temperature and metal content on the conversion of CH 4 and H 2 /CO ratio were also investigated. Results indicated that CH4 conversion increased significantly with the increase of the reaction temperature and metal content. (author)

  5. A DFT investigation on group 8B transition metal-doped silicon carbide nanotubes for hydrogen storage application

    Science.gov (United States)

    Tabtimsai, Chanukorn; Ruangpornvisuti, Vithaya; Tontapha, Sarawut; Wanno, Banchob

    2018-05-01

    The binding of group 8B transition metal (TMs) on silicon carbide nanotubes (SiCNT) hydrogenated edges and the adsorption of hydrogen molecule on the pristine and TM-doped SiCNTs were investigated using the density functional theory method. The B3LYP/LanL2DZ method was employed in all calculations for the considered structural, adsorption, and electronic properties. The Os atom doping on the SiCNT is found to be the strongest binding. The hydrogen molecule displays a weak interaction with pristine SiCNT, whereas it has a strong interaction with TM-doped SiCNTs in which the Os-doped SiCNT shows the strongest interaction with the hydrogen molecule. The improvement in the adsorption abilities of hydrogen molecule onto TM-doped SiCNTs is due to the protruding structure and the induced charge transfer between TM-doped SiCNT and hydrogen molecule. These observations point out that TM-doped SiCNTs are highly sensitive toward hydrogen molecule. Moreover, the adsorptions of 2-5 hydrogen molecules on TM-doped SiCNT were also investigated. The maximum storage number of hydrogen molecules adsorbed on the first layer of TM-doped SiCNTs is 3 hydrogen molecules. Therefore, TM-doped SiCNTs are suitable to be sensing and storage materials for hydrogen gas.

  6. Lithium doping on covalent organic framework-320 for enhancing hydrogen storage at ambient temperature

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Liangzhi, E-mail: 15004110853@163.com; Liu, Qing

    2016-12-15

    Density Functional Theory (DFT) combines with grand canonical Monte Carlo (GCMC) simulations are performed to explore the effect of Li doping on the hydrogen storage capability of COF-320. The results show that the interaction energy between the H{sub 2} and the Li-doped COF-320 is about three times higher than that of pristine COF-320. GCMC simulations are employed to study the hydrogen uptake of Li-doped COF-320 at ambient temperature, further confirm that the lithium doping can improve the hydrogen uptake at ambient temperature. Our results demonstrate that Li-doped COFs have good potential in the field of hydrogen storage. - Graphical abstract: Fig. 1. The optimized cluster model used here to represent the COF-320 and possible adsorption sites (A, B, C) for adsorption of metals in the COF-320. The dangling bonds are terminated by H atoms. C, H, and N atoms are shown as gray, white, and blue colors, respectively. Fig. 2. The adsorption isotherm of H{sub 2} in the pristine and Li-doped COF-320 at 298 K. - Highlights: • The binding sites of single and two lithium atoms in COF-320 were studied. • The interaction energy between the H{sub 2} and the Li-doped COF-320 is about three times higher than that of pristine COF-320. • H{sub 2} uptakes on the Li-doped COFs obtain significant improvement at ambient temperature. • Lithium-doping is a successful strategy for improving hydrogen uptake.

  7. Lithium doping on covalent organic framework-320 for enhancing hydrogen storage at ambient temperature

    International Nuclear Information System (INIS)

    Xia, Liangzhi; Liu, Qing

    2016-01-01

    Density Functional Theory (DFT) combines with grand canonical Monte Carlo (GCMC) simulations are performed to explore the effect of Li doping on the hydrogen storage capability of COF-320. The results show that the interaction energy between the H 2 and the Li-doped COF-320 is about three times higher than that of pristine COF-320. GCMC simulations are employed to study the hydrogen uptake of Li-doped COF-320 at ambient temperature, further confirm that the lithium doping can improve the hydrogen uptake at ambient temperature. Our results demonstrate that Li-doped COFs have good potential in the field of hydrogen storage. - Graphical abstract: Fig. 1. The optimized cluster model used here to represent the COF-320 and possible adsorption sites (A, B, C) for adsorption of metals in the COF-320. The dangling bonds are terminated by H atoms. C, H, and N atoms are shown as gray, white, and blue colors, respectively. Fig. 2. The adsorption isotherm of H 2 in the pristine and Li-doped COF-320 at 298 K. - Highlights: • The binding sites of single and two lithium atoms in COF-320 were studied. • The interaction energy between the H 2 and the Li-doped COF-320 is about three times higher than that of pristine COF-320. • H 2 uptakes on the Li-doped COFs obtain significant improvement at ambient temperature. • Lithium-doping is a successful strategy for improving hydrogen uptake.

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

    International Nuclear Information System (INIS)

    Gedam, R.S.; Ramteke, D.D.

    2011-01-01

    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 CeO 2 are extensively studied for scintillating applications. Radiation length of CeO 2 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 15Li 2 O-xCeO 2 -(85''x)B 2 O 3 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 CeO 2 . 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 CeO 2 . The radiation length was determined using density values and it was found to decrease with the addition of CeO 2 . 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 (E g Opt ) decreases with the addition of CeO 2

  9. Formation and nitrile hydrogenation performance of Ru nanoparticles on a K-doped Al2O3 surface.

    Science.gov (United States)

    Muratsugu, Satoshi; Kityakarn, Sutasinee; Wang, Fei; Ishiguro, Nozomu; Kamachi, Takashi; Yoshizawa, Kazunari; Sekizawa, Oki; Uruga, Tomoya; Tada, Mizuki

    2015-10-14

    Decarbonylation-promoted Ru nanoparticle formation from Ru3(CO)12 on a basic K-doped Al2O3 surface was investigated by in situ FT-IR and in situ XAFS. Supported Ru3(CO)12 clusters on K-doped Al2O3 were converted stepwise to Ru nanoparticles, which catalyzed the selective hydrogenation of nitriles to the corresponding primary amines via initial decarbonylation, the nucleation of the Ru cluster core, and the growth of metallic Ru nanoparticles on the surface. As a result, small Ru nanoparticles, with an average diameter of less than 2 nm, were formed on the support and acted as efficient catalysts for nitrile hydrogenation at 343 K under hydrogen at atmospheric pressure. The structure and catalytic performance of Ru catalysts depended strongly on the type of oxide support, and the K-doped Al2O3 support acted as a good oxide for the selective nitrile hydrogenation without basic additives like ammonia. The activation of nitriles on the modelled Ru catalyst was also investigated by DFT calculations, and the adsorption structure of a nitrene-like intermediate, which was favourable for high primary amine selectivity, was the most stable structure on Ru compared with other intermediate structures.

  10. A computational study on the hydrogen adsorption capacity of various lithium-doped boron hydrides.

    Science.gov (United States)

    Pan, Sudip; Giri, Santanab; Chattaraj, Pratim K

    2012-02-05

    An aromatic boron hydride B(3)H(3)(2-) and its various Li/Li(+) doped isomers have been studied at the B3LYP/6-311+G(d) and M06/6-311+G(d) levels of theory to assess their hydrogen storage potential. Different types of interaction energies, reaction enthalpies and reaction electrophilicities associated with the hydrogen adsorption process suggest that B(3)H(3)(2-) itself and some of its Li-decorated analogues may turn out to be effective hydrogen storage material. Nucleus independent chemical shift and conceptual density functional theory based reactivity descriptors lend additional support. The temperature-pressure phase diagram identifies the temperature-pressure zone where the reaction Gibbs free energy for the hydrogen adsorption is negative making it a thermodynamically feasible process. Copyright © 2011 Wiley Periodicals, Inc.

  11. The influence of CeO2 on the microstructure and electrical behaviour of ZnO-Bi2O3 based varistors

    International Nuclear Information System (INIS)

    Lei Ming; Li Shengtao; Jiao Xiaodong; Li Jianying; Alim, Mohammad A

    2004-01-01

    The processing-microstructure-property relations have been studied in order to understand the role of the addition of CeO 2 (up to 0.9 mole%) in the ZnO-Bi 2 O 3 based varistor recipe. The microstructural investigation suggests that CeO 2 is segregated at the corners of the ZnO grains in addition to the existence of the Zn 7 Sb 2 O 12 spinel phase. However, the α -spinel phase was observed instead of the β -spinel phase that is usually found in most commercial and laboratory ZnO-Bi 2 O 3 based varistors. The α -spinel phase is more stable than the β -spinel phase and does not transform to the pyrochlore phase during the cooling process. The most significant effect of the CeO 2 particles is the ZnO grain refinement owing to the pinning effect of the grain growth. The average grain size decreases from 7.8 to 5.7 μm when compared to the 0.9 mole% CeO 2 -added sample against the CeO 2 -free sample. This grain refinement results in a significantly enhanced breakdown field when compared to the CeO 2 -free sample. The coefficient of nonlinearity of the current-voltage (I-V) characteristics is found to be nearly identical for the CeO 2 added varistor materials. However, when a slower cooling cycle (1 deg. C min -1 instead of 4 deg. C min -1 ) is used in the sintering process, these varistor materials exhibited a high nonlinear coefficient (α = 29 ± 5) as extracted from the I-V behaviour

  12. In Situ Fluorine Doping of TiO2 Superstructures for Efficient Visible-Light Driven Hydrogen Generation.

    Science.gov (United States)

    Zhang, Peng; Tachikawa, Takashi; Fujitsuka, Mamoru; Majima, Tetsuro

    2016-03-21

    With the aid of breakthroughs in nanoscience and nanotechnology, it is imperative to develop metal oxide semiconductors through visible light-driven hydrogen generation. In this study, TiOF2 was incorporated as an n-type F-dopant source to TiO2 mesocrystals (TMCs) with visible-light absorption during the topotactic transformation. The crystal growth, structural change, and dynamic morphological evolution, from the initial intermediate NH4 TiOF3 to HTiOF3, TiOF2, and F-doped TMCs, were verified through in situ temperature-dependent techniques to elucidate the doping mechanism from intermediate TiOF2. The visible-light efficiencies of photocatalytic hydrogen were dependent on the contents of the dopant as compared with the pure TMC and a controled reference. Using femtosecond time-resolved diffuse reflectance spectroscopy, the charge-transfer dynamics were monitored to confirm the improvement of charge separation after doping. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Hydrogen evolution by a metal-free electrocatalyst

    KAUST Repository

    Zheng, Yao

    2014-04-28

    Electrocatalytic reduction of water to molecular hydrogen via the hydrogen evolution reaction may provide a sustainable energy supply for the future, but its commercial application is hampered by the use of precious platinum catalysts. All alternatives to platinum thus far are based on nonprecious metals, and, to our knowledge, there is no report about a catalyst for electrocatalytic hydrogen evolution beyond metals. Here we couple graphitic-carbon nitride with nitrogen-doped graphene to produce a metal-free hybrid catalyst, which shows an unexpected hydrogen evolution reaction activity with comparable overpotential and Tafel slope to some of well-developed metallic catalysts. Experimental observations in combination with density functional theory calculations reveal that its unusual electrocatalytic properties originate from an intrinsic chemical and electronic coupling that synergistically promotes the proton adsorption and reduction kinetics. © 2014 Macmillan Publishers Limited. All rights reserved.

  14. Hydrogen Doping into MoO3 Supports toward Modulated Metal-Support Interactions and Efficient Furfural Hydrogenation on Iridium Nanocatalysts.

    Science.gov (United States)

    Xie, Lifang; Chen, Ting; Chan, Hang Cheong; Shu, Yijin; Gao, Qingsheng

    2018-03-16

    As promising supports, reducible metal oxides afford strong metal-support interactions to achieve efficient catalysis, which relies on their band states and surface stoichiometry. In this study, in situ and controlled hydrogen doping (H doping) by means of H 2 spillover was employed to engineer the metal-support interactions in hydrogenated MoO x -supported Ir (Ir/H-MoO x ) catalysts and thus promote furfural hydrogenation to furfuryl alcohol. By easily varying the reduction temperature, the resulting H doping in a controlled manner tailors low-valence Mo species (Mo 5+ and Mo 4+ ) on H-MoO x supports, thereby promoting charge redistribution on Ir and H-MoO x interfaces. This further leads to clear differences in H 2 chemisorption on Ir, which illustrates its potential for catalytic hydrogenation. As expected, the optimal Ir/H-MoO x with controlled H doping afforded high activity (turnover frequency: 4.62 min -1 ) and selectivity (>99 %) in furfural hydrogenation under mild conditions (T=30 °C, PH2 =2 MPa), which means it performs among the best of current catalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Toward transparent nanocomposites based on polystyrene matrix and PMMA-grafted CeO2 nanoparticles.

    Science.gov (United States)

    Parlak, Onur; Demir, Mustafa M

    2011-11-01

    The association of transparent polymer and nanosized pigment particles offers attractive optical materials for various potential and existing applications. However, the particles embedded into polymers scatter light due to refractive index (RI) mismatch and reduce transparency of the resulting composite material. In this study, optical composites based on polystyrene (PS) matrix and poly(methyl methacrylate) (PMMA)-grafted CeO(2) hybrid particles were prepared. CeO(2) nanoparticles with an average diameter of 18 ± 8 nm were precipitated by treating Ce(NO(3))·6H(2)O with urea in the presence of a polymerizable surfactant, 3-methacyloxypropyltrimethoxy silane. PMMA chains were grafted on the surface of the nanoparticles upon free radical in situ solution polymerization. While blending of unmodified CeO(2) particles with PS resulted in opaque films, the transparency of the composite films was remarkably enhanced when prepared by PMMA-grafted CeO(2) hybrid particles, particularly those having a PMMA thickness of 9 nm. The improvement in transparency is presumably due to the reduction in RI mismatch between CeO(2) particles and the PS matrix when using PMMA chains at the interface.

  16. Modeling of a CeO2 thermochemistry reduction process for hydrogen production by solar concentrated energy

    Science.gov (United States)

    Valle-Hernández, Julio; Romero-Paredes, Hernando; Arancibia-Bulnes, Camilo A.; Villafan-Vidales, Heidi I.; Espinosa-Paredes, Gilberto

    2016-05-01

    In this paper the simulation of the thermal reduction for hydrogen production through the decomposition of cerium oxide is presented. The thermochemical cycle for hydrogen production consists of the endothermic reduction of CeO2 at high temperature, where concentrated solar energy is used as a source of heat; and of the subsequent steam hydrolysis of the resulting cerium oxide to produce hydrogen. For the thermochemical process, a solar reactor prototype is proposed; consisting of a cubic receptacle made of graphite fiber thermally insulated. Inside the reactor a pyramidal arrangement with nine tungsten pipes is housed. The pyramidal arrangement is made respect to the focal point where the reflected energy is concentrated. The solar energy is concentrated through the solar furnace of high radiative flux. The endothermic step is the reduction of the cerium oxide to lower-valence cerium oxide, at very high temperature. The exothermic step is the hydrolysis of the cerium oxide (III) to form H2 and the corresponding initial cerium oxide made at lower temperature inside the solar reactor. For the modeling, three sections of the pipe where the reaction occurs were considered; the carrier gas inlet, the porous medium and the reaction products outlet. The mathematical model describes the fluid mechanics; mass and energy transfer occurring therein inside the tungsten pipe. Thermochemical process model was simulated in CFD. The results show a temperature distribution in the solar reaction pipe and allow obtaining the fluid dynamics and the heat transfer within the pipe. This work is part of the project "Solar Fuels and Industrial Processes" from the Mexican Center for Innovation in Solar Energy (CEMIE-Sol).

  17. Micelle-Template Synthesis of Nitrogen-Doped Mesoporous Graphene as an Efficient Metal-Free Electrocatalyst for Hydrogen Production

    Science.gov (United States)

    Huang, Xiaodan; Zhao, Yufei; Ao, Zhimin; Wang, Guoxiu

    2014-12-01

    Synthesis of mesoporous graphene materials by soft-template methods remains a great challenge, owing to the poor self-assembly capability of precursors and the severe agglomeration of graphene nanosheets. Herein, a micelle-template strategy to prepare porous graphene materials with controllable mesopores, high specific surface areas and large pore volumes is reported. By fine-tuning the synthesis parameters, the pore sizes of mesoporous graphene can be rationally controlled. Nitrogen heteroatom doping is found to remarkably render electrocatalytic properties towards hydrogen evolution reactions as a highly efficient metal-free catalyst. The synthesis strategy and the demonstration of highly efficient catalytic effect provide benchmarks for preparing well-defined mesoporous graphene materials for energy production applications.

  18. Facile hydrothermal synthesis of CeO 2 nanopebbles

    Indian Academy of Sciences (India)

    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 ...

  19. Comparative study of reversible hydrogen storage in alkali-doped fulleranes

    Energy Technology Data Exchange (ETDEWEB)

    Teprovich, Joseph A.; Knight, Douglas A.; Peters, Brent [Clean Energy Directorate – Savannah River National Laboratory, Aiken, SC 29801 (United States); Zidan, Ragaiy, E-mail: ragaiy.zidan@srnl.doe.gov [Clean Energy Directorate – Savannah River National Laboratory, Aiken, SC 29801 (United States)

    2013-12-15

    Highlights: ► Catalytic effect of alkali metals of fullerane formation. ► Hydrogen storage properties of alkali metal hydrides and fullerene composites. ► Novel intercalation of Na and Li in the fullerene lattice. ► Reversible phase transformation of C{sub 60} from fcc to bcc upon de/rehydrogenation. ► Potential to enable to the formation of other carbon based hydrogen storage systems. -- Abstract: In this report we describe and compare the hydrogen storage properties of lithium and sodium doped fullerenes prepared via a solvent-assisted mixing process. For the preparation of these samples either NaH or LiH was utilized as the alkali metal source to make material based on either a Na{sub 6}C{sub 60} or Li{sub 6}C{sub 60}. Both of the alkali-doped materials can reversibly absorb and desorb hydrogen at much milder conditions than the starting materials used to make them (decomposition temperatures of NaH > 420 °C, LiH > 670 °C, and fullerane > 500 °C). The hydrogen storage properties of the materials were compared by TGA, isothermal desorption, and XRD analysis. It was determined that the sodium-doped material can reversibly store 4.0 wt.% H{sub 2} while the lithium doped material can reversibly store 5.0 wt.% H{sub 2} through a chemisorption mechanism indicated by the formation and measurement of C–H bonds. XRD analysis of the material demonstrated that a reversible phase transition between fcc and bcc occurs depending on the temperature at which the hydrogenation is performed. In either system the active hydrogen storage material resembles a hydrogenated fullerene (fullerane)

  20. Comparative study of reversible hydrogen storage in alkali-doped fulleranes

    International Nuclear Information System (INIS)

    Teprovich, Joseph A.; Knight, Douglas A.; Peters, Brent; Zidan, Ragaiy

    2013-01-01

    Highlights: ► Catalytic effect of alkali metals of fullerane formation. ► Hydrogen storage properties of alkali metal hydrides and fullerene composites. ► Novel intercalation of Na and Li in the fullerene lattice. ► Reversible phase transformation of C 60 from fcc to bcc upon de/rehydrogenation. ► Potential to enable to the formation of other carbon based hydrogen storage systems. -- Abstract: In this report we describe and compare the hydrogen storage properties of lithium and sodium doped fullerenes prepared via a solvent-assisted mixing process. For the preparation of these samples either NaH or LiH was utilized as the alkali metal source to make material based on either a Na 6 C 60 or Li 6 C 60 . Both of the alkali-doped materials can reversibly absorb and desorb hydrogen at much milder conditions than the starting materials used to make them (decomposition temperatures of NaH > 420 °C, LiH > 670 °C, and fullerane > 500 °C). The hydrogen storage properties of the materials were compared by TGA, isothermal desorption, and XRD analysis. It was determined that the sodium-doped material can reversibly store 4.0 wt.% H 2 while the lithium doped material can reversibly store 5.0 wt.% H 2 through a chemisorption mechanism indicated by the formation and measurement of C–H bonds. XRD analysis of the material demonstrated that a reversible phase transition between fcc and bcc occurs depending on the temperature at which the hydrogenation is performed. In either system the active hydrogen storage material resembles a hydrogenated fullerene (fullerane)

  1. Effect of cerium oxide doping on the performance of CaO-based sorbents during calcium looping cycles.

    Science.gov (United States)

    Wang, Shengping; Fan, Shasha; Fan, Lijing; Zhao, Yujun; Ma, Xinbin

    2015-04-21

    A series of CaO-based sorbents were synthesized through a sol-gel method and doped with different amounts of CeO2. The sorbent with a Ca/Ce molar ratio of 15:1 showed an excellent absorption capacity (0.59 gCO2/g sorbent) and a remarkable cycle durability (up to 18 cycles). The admirable capture performance of CaCe-15 was ascribed to its special morphology formed by the doping of CeO2 and the well-distributed CeO2 particles. The sorbents doped with CeO2 possessed a loose shell-connected cross-linking structure, which was beneficial for the contact between CaO and CO2. CaO and CeO2 were dispersed homogeneously, and the existence of CeO2 also decreased the grain size of CaO. The well-dispersed CeO2, which could act as a barrier, effectively prevented the CaO crystallite from growing and sintering, thus the sorbent exhibited outstanding stability. The doping of CeO2 also improved the carbonation rate of the sorbent, resulting in a high capacity in a short period of time.

  2. Electron-doping by hydrogen in transition-metal dichalcogenides

    Science.gov (United States)

    Oh, Sehoon; Im, Seongil; Choi, Hyoung Joon

    Using first-principles calculations, we investigate the atomic and electronic structures of 2H-phase transition-metal dichalcogenides (TMDC), 2H-MX2, with and without defects, where M is Mo or W and X is S, Se or Te. We find that doping of atomic hydrogen on 2H-MX2 induces electron doping in the conduction band. To understand the mechanism of this electron doping, we analyze the electronic structures with and without impurities. We also calculate the diffusion energy barrier to discuss the spatial stability of the doping. Based on these results, we suggest a possible way to fabricate elaborately-patterned circuits by modulating the carrier type of 2H-MoTe2. We also discuss possible applications of this doping in designing nano-devices. This work was supported by NRF of Korea (Grant No. 2011-0018306) and KISTI supercomputing center (Project No. KSC-2016-C3-0052).

  3. Kinetics of hydrogen reduction of titanium-doped molybdenum dioxide

    International Nuclear Information System (INIS)

    He, Qian; Marin-Flores, Oscar; Hu, Shuozhen; Scudiero, Louis; Ha, Su; Norton, M. Grant

    2015-01-01

    Ti-doped MoO 2 was synthesized to broaden the oxygen-to-carbon ratio operating range of MoO 2 for partial oxidation of long-chain hydrocarbons by increasing the redox stability. The structure modification causes the hydrogen reduction mechanism to change from three-dimensional nuclei growth with an activation energy of 61.3 kJ mol −1 to a three-dimensional hydrogen diffusion limited model with an activation energy of 317.9 kJ mol −1 . Because of the enhanced redox stability, Ti-doped MoO 2 has potential as an alternative anode in direct liquid-fed solid oxide fuel cells

  4. Stability aspects of hydrogen-doped indium oxide

    OpenAIRE

    Jost, Gabrielle; Hamri, Alexander Nordin; Köhler, Florian; Hüpkes, Jürgen

    2015-01-01

    Transparent conductive oxides play an important role as contact layers in various opto-electronic devices such as solar cells or LEDs. Whilst crystalline materials e.g. zinc oxide (ZnO), tin oxide (Sn2O3) or tin doped indium oxide (ITO) have already been vastly investigated and applied [1] hydrogen doped indium oxide (In2O3:H) entered the scene a while ago as a new material with a superior trade-off between electrical and optical performance. In2O3:H is commonly deposited at room temperature...

  5. CeO2-TiO2 Photocatalyst: Ionic Liquid-Mediated Synthesis, Characterization, and Performance for Diisopropanolamine Visible Light Degradation

    Directory of Open Access Journals (Sweden)

    Jagath Retchahan Sivalingam

    2018-01-01

    Full Text Available CeO2-TiO2 photocatalyst with Ce:Ti molar ratio of 1:9 was synthesized via co-precipitation method in the presence of 1-ethyl-3-methyl imidazolium octylsulfate, [EMIM][OctSO4] (CeO2-TiO2-IL. The ionic liquid acts as a templating agent for particle growth. The CeO2-TiO2 and TiO2 photocatalysts were also synthesized without any ionic liquid for comparison. Calcination was conducted on the as-synthesized materials at 400˚C for 2 h. The photocatalysts were characterized using diffuse reflectance UV-Vis spectroscopy (DR-UV-Vis, field emission scanning electron microscopy (FESEM, X-ray powder diffraction (XRD, and surface area and pore size analyzer (SAP. The presence of CeO2 has changed the optical property of TiO2. It has extended the absorption edge of TiO2 from UV to visible region. The calculated band gap energy decreased from 2.82 eV (TiO2 to 2.30 eV (CeO2-TiO2-IL. The FESEM morphology showed that samples forms aggregates and the surface smoothens when ionic liquid was added. The average crystallite size of TiO2, CeO2-TiO2, and CeO2-TiO2-IL were 20.8 nm, 5.5 nm, and 4 nm. In terms of performance, photodegradation of 1000 ppm of diisopropanolamine (DIPA was conducted in the presence of hydrogen peroxide (H2O2 and visible light irradiation which was provided by a 500 W halogen lamp. The best performance was displayed by CeO2-TiO2-IL calcined at 400˚C. It was able to remove 82.0% DIPA and 54.8% COD after 6 h reaction.  Copyright © 2018 BCREC Group. All rights reserved Received: 26th July 2017; Revised: 22nd October 2017; Accepted: 29th October 2017; Available online: 22nd January 2018; Published regularly: 2nd April 2018 How to Cite: Sivalingam, J.R., Kait, C.F., Wilfred, C.D. (2018. CeO2-TiO2 Photocatalyst: Ionic Liquid-Mediated Synthesis, Characterization, and Performance for Diisopropanolamine Visible Light Degradation. Bulletin of Chemical Reaction Engineering & Catalysis, 13 (1: 170-178 (doi:10.9767/bcrec.13.1.1396.170-178

  6. Tunable flux pinning landscapes achieved by functional ferromagnetic Fe2O3:CeO2 vertically aligned nanocomposites in YBa2Cu3O7−δ thin films

    International Nuclear Information System (INIS)

    Tsai, Chen-Fong; Huang, Jijie; Lee, Joon-Hwan; Khatkhatay, Fauzia; Chen, Li; Chen, Aiping; Su, Qing; Wang, Haiyan

    2015-01-01

    Highlights: • Functional ferromagnetic (Fe 2 O 3 ) x :(CeO 2 ) 1−x vertically aligned nanocomposites (VAN). • An ordered arrangement of ferromagnetic Fe 2 O 3 nanoinclusions. • Significant in-field improvement of J c (H//c) in both VAN nanolayer capped and buffered samples. • T c above 90 K and the J c sf maximized at 3.07 MA/cm 2 (75 K) and 9.2 MA/cm 2 (65 K) for 30% Fe 2 O 3 sample. - Abstract: Functional ferromagnetic (Fe 2 O 3 ) x :(CeO 2 ) 1−x vertically aligned nanocomposite (VAN) layers were deposited as either buffer or cap layers for YBa 2 Cu 3 O 7−δ (YBCO) thin films. The composition of Fe 2 O 3 dopants in the VAN nanolayers is controlled at 10%, 30% and 50% in order to create different arrangements of Fe 2 O 3 and CeO 2 nanopillars and therefore to tune the flux pining landscapes. The composition variation provides tunable and ordered arrangements of magnetic nanodopants and interfacial defects as pinning centers in the YBCO thin films. The superconducting property measurements show that most doped samples obtain a T c above 90 K and the J c sf measured at 75 K and 65 K maximized at 3.07 MA/cm 2 and 9.2 MA/cm 2 for 30% Fe 2 O 3 VAN doped sample. As the temperature decreased to 5 K, the sample with 50% Fe 2 O 3 VAN doped sample show the best pinning effect due to pronounced magnetic pinning effects. This work demonstrates the tunable density of magnetic pinning centers can be achieved by VAN to meet the specific pinning requirement

  7. Photocatalytic Hydrogen or Oxygen Evolution from Water over S- or N-Doped TiO2 under Visible Light

    Directory of Open Access Journals (Sweden)

    Kazumoto Nishijima

    2008-01-01

    Full Text Available S- or N-doping of TiO2 powder having an anatase or rutile phase extended the photocatalytic activity for water oxidation and reduction under UV light and visible light irradiation. For the reduction of water, anatase-doped TiO2 showed higher level of activity than that of doped TiO2 having a rutile phase using ethanol as an electron donor. Furthermore, the activity level of S-doped TiO2 for hydrogen evolution was higher than that of N-doped TiO2 photocatalysts under visible light. Photocatalytic oxidation of water on doped TiO2 having a rutile phase proceeded with fairly high efficiency when Fe3+ ions were used as electron acceptors compared to that on doped TiO2 having an anatase phase. In addition, water splitting under visible light irradiation was achieved by construction of a Z-scheme photocatalysis system employing the doped TiO2 having anatase and rutile phases for H2 and O2 evolution and the I−/IO3− redox couple as an electron relay.

  8. Theoretical investigation on the alkali-metal doped BN fullerene as a material for hydrogen storage

    International Nuclear Information System (INIS)

    Venkataramanan, Natarajan Sathiyamoorthy; Belosludov, Rodion Vladimirovich; Note, Ryunosuke; Sahara, Ryoji; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2010-01-01

    Graphical abstract: First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. Adsorption of alkali atoms involves a charge transfer process, creating positively-charged alkali atoms and this polarizes the H 2 molecules and increases their binding energy. The maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 H 2 were adsorbed in molecular form. - Abstract: First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. The alkali atom adsorption takes place near the six tetragonal bridge sites available on the cage, thereby avoiding the notorious clustering problem. Adsorption of alkali atoms involves a charge transfer process, creating positively charged alkali atoms and this polarizes the H 2 molecules thereby, increasing their binding energy. Li atom has been found to adsorb up to three hydrogen molecules with an average binding energy of 0.189 eV. The fully doped Li 6 B 36 N 36 cluster has been found to hold up to 18 hydrogen molecules with the average binding energy of 0.146 eV. This corresponds to a gravimetric density of hydrogen storage of 3.7 wt.%. Chemisorption on the Li 6 B 36 N 36 has been found to be an exothermic reaction, in which 60 hydrogen atoms chemisorbed with an average chemisorption energy of -2.13 eV. Thus, the maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 hydrogen molecules were adsorbed in molecular form.

  9. Facile Synthesis of Boron-doped Graphene Nanosheets with Hierarchical Microstructure at Atmosphere Pressure for Metal-free Electrochemical Detection of Hydrogen Peroxide

    International Nuclear Information System (INIS)

    Yeh, Min-Hsin; Li, Yan-Sheng; Chen, Guan-Lin; Lin, Lu-Yin; Li, Ta-Jen; Chuang, Hui-Min; Hsieh, Cheng-Yu; Lo, Shen-Chuan; Chiang, Wei-Hung; Ho, Kuo-Chuan

    2015-01-01

    Graphical abstract: Display Omitted -- Highlights: • B-doped graphene nanosheets (BGNs) were used as a catalyst for sensing H 2 O 2 . • BGNs were synthesized by an atmospheric-pressure carbothermal reaction. • BGNs with hierarchical microstructure provide more electron transport pathways. • B atoms act as the active sites by transferring charges to neighboring C atoms. • Electrocatalytic ability of BGNs was characterized by a rotating disk electrode. -- Abstract: Hydrogen peroxide (H 2 O 2 ) is an essential mediator for most of the oxidative biological reactions in enzyme-based biosensor systems, such as glucose oxidase, cholesterol oxidase, and alcohol oxidase. Synthesis of new catalysts to detect the concentration of H 2 O 2 more precisely is indispensable for enzyme-based electrochemical biosensors. In this study, boron-doped graphene nanosheets (BGNs) with 2.2 atomic percentage (at%) boron doping level and a hierarchical microstructure were synthesized by an atmospheric-pressure carbothermal reaction as a noble-metal free catalyst for sensing H 2 O 2 . The isolated boron atoms on the BGNs surface act as the electrocatalytic sites by transferring charges to neighbor carbon atoms, and the hierarchical microstructure provides multidimensional electron transport pathways for charge transfer and therefore enhances the electrocatalytic ability. BGNs possess a higher reduction current in the cyclic voltammetry (CV) measurement than that of pristine graphene nanosheets (GNs) over the detection range of 0.0 to 10.0 mM at −0.4 V (vs. Ag/AgCl). The BGNs modified electrochemical sensor shows a linear range from 1.0 to 20.0 mM of H 2 O 2 with a sensitivity of 266.7 ± 3.8 μA mM −1 cm −2 and limit of detection (LOD) of 3.8 μM at a signal-to-noise (S/N) ratio of 3. The beneficial hierarchical microstructure and the synergetic effects arising from doping boron in GNs accomplish the better performance of the BGNs modified electrochemical sensor

  10. Effects of calcium doping on the superconducting properties of top-seeded melt growth processed Y1.5Ba2-xCaxCu3Oy superconductors

    International Nuclear Information System (INIS)

    Park, S.D.; Kim, H.J.; Park, B.J.; Han, Y.H.; Jun, B.-H.; Lee, J.S.; Kim, C.-J.

    2011-01-01

    We study effects of calcium doping in melt processed Y123 superconductors. We examine a superconducting transition temperature and current density. A transition temperature and current density decreases by calcium doping. Calcium doping leads to coarseing of Y211 particles. Y211 refining effect by CeO 2 is disappreared by calcium doping. The effect of calcium doping on the superconducting properties of top seeded melt growth (TSMG) processed Y 1.5 Ba 2-x Ca x Cu 3 O y superconductors was studied in terms of calcium content (X ca ). YBa 2-x Ca x Cu 3 O 7-δ (X ca = 0, 0.005, 0.01, 0.02, 0.04, 0.1, 0.3) powders were synthesized by the powder calcination method. YBa 2-x Ca x Cu 3 O 7-δ powders were mixed with 0.25 mole Y 2 O 3 powder and 1 wt.% CeO 2 as Y 2 BaCuO 5 (Y211) refiner, and finally made into Y 1 . 5 Ba 2-x Ca x Cu 3 O y (Y1.5) + 1 wt.% CeO 2 composition. The single Y123 growth on the top surface was observed up to X ca = 0.1, while the multiple Y123 growth was observed at X ca ≥ 0.1. The superconducting transition temperature (T c ) and critical current density (J c ) of TSMG processed Y1.5 samples were inversely proportional to X ca . The Y211 size increased with increasing X ca due to the enhancement of Y211 coarsening by calcium doping. No Y211 refining effect by CeO 2 was observed in the calcium doped samples. The T c and J c decrease by calcium doping are likely to be due to the calcium incorporation with the Y123 lattice and formation of coarse Y211 particles.

  11. Synthesis and Characterization of Highly Sensitive Hydrogen (H2 Sensing Device Based on Ag Doped SnO2 Nanospheres

    Directory of Open Access Journals (Sweden)

    Zhaorui Lu

    2018-03-01

    Full Text Available In this paper, pure and Ag-doped SnO2 nanospheres were synthesized by hydrothermal method and characterized via X-ray powder diffraction (XRD, field emission scanning electron microscopy (FESEM, energy dispersive spectroscopy (EDS, and X-ray photoelectron spectra (XPS, respectively. The gas sensing performance of the pure, 1 at.%, 3 at.%, and 5 at.% Ag-doped SnO2 sensing devices toward hydrogen (H2 were systematically evaluated. The results indicated that compared with pure SnO2 nanospheres, Ag-doped SnO2 nanospheres could not only decrease the optimum working temperature but also significantly improve H2 sensing such as higher gas response and faster response-recovery. Among all the samples, the 3 at.% Ag-doped SnO2 showed the highest response 39 to 100 μL/L H2 at 300 °C. Moreover, its gas sensing mechanism was discussed, and the results will provide reference and theoretical guidance for the development of high-performance SnO2-based H2 sensing devices.

  12. Effect of CeO2 and Y2O3 on microstructure, bioactivity and degradability of laser cladding CaO-SiO2 coating on titanium alloy.

    Science.gov (United States)

    Li, H C; Wang, D G; Chen, C Z; Weng, F

    2015-03-01

    To solve the lack of strength of bulk biomaterials for load-bearing applications and improve the bioactivity of titanium alloy (Ti-6Al-4V), CaO-SiO2 coatings on titanium alloy were fabricated by laser cladding technique. The effect of CeO2 and Y2O3 on microstructure and properties of laser cladding coating was analyzed. The cross-section microstructure of ceramic layer from top to bottom gradually changes from cellular-dendrite structure to compact cellular crystal. The addition of CeO2 or Y2O3 refines the microstructure of the ceramic layer in the upper and middle regions. The refining effect on the grain is related to the kinds of additives and their content. The coating is mainly composed of CaTiO3, CaO, α-Ca2(SiO4), SiO2 and TiO2. Y2O3 inhibits the formation of CaO. After soaking in simulated body fluid (SBF), the calcium phosphate layer is formed on the coating surface, indicating the coating has bioactivity. After soaking in Tris-HCl solution, the samples doped with CeO2 or Y2O3 present a lower weight loss, indicating the addition of CeO2 or Y2O3 improves the degradability of laser cladding sample. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Defect studies of ZnO single crystals electrochemically doped with hydrogen

    Science.gov (United States)

    Čížek, J.; Žaludová, N.; Vlach, M.; Daniš, S.; Kuriplach, J.; Procházka, I.; Brauer, G.; Anwand, W.; Grambole, D.; Skorupa, W.; Gemma, R.; Kirchheim, R.; Pundt, A.

    2008-03-01

    Various defect studies of hydrothermally grown (0001) oriented ZnO crystals electrochemically doped with hydrogen are presented. The hydrogen content in the crystals is determined by nuclear reaction analysis and it is found that already 0.3at.% H exists in chemically bound form in the virgin ZnO crystals. A single positron lifetime of 182ps is detected in the virgin crystals and attributed to saturated positron trapping at Zn vacancies surrounded by hydrogen atoms. It is demonstrated that a very high amount of hydrogen (up to ˜30at.%) can be introduced into the crystals by electrochemical doping. More than half of this amount is chemically bound, i.e., incorporated into the ZnO crystal lattice. This drastic increase of the hydrogen concentration is of marginal impact on the measured positron lifetime, whereas a contribution of positrons annihilated by electrons belonging to O-H bonds formed in the hydrogen doped crystal is found in coincidence Doppler broadening spectra. The formation of hexagonal shape pyramids on the surface of the hydrogen doped crystals by optical microscopy is observed and discussed.

  14. Al2O3 doped TiO2 ceramic waste forms

    International Nuclear Information System (INIS)

    Uno, Masayoshi; Kinoshita, Hajime; Sakai, Etsuro; Ikeda, Akira; Matsumoto, Y.; Yamanaka, Shinsuke

    1999-01-01

    Melting of the mixture of Nd 2 O 3 , CeO 2 , SrO, TiO 2 and Al 2 O 3 at 1673 K for 1 hour produced one RE 2 Ti 3 O 9 phase compound. Differential Scanning Calorimetry (DSC) measurement showed that the melting temperature of this compound was 1646 K. Density of the alumina doped oxide was higher than that of the oxide obtained by the pressing and sintering without alumina. Vickers hardness of the oxide obtained by the pressing and sintering was 5.3 GPa and nearly same as that of glass waste. That of the alumina doped oxide was around 7 GPa. 7 days Soxhlet leach test (MCC-5) followed by Inductively Coupled Plasma Spectrometry (ICP) showed that normalized leaching rate of Ti for the oxide obtained by the pressing and sintering was 5.54 x 10 -3 kg/m 2 and that for the alumina doped oxide was 2.24 x 10 -3 kg/m 2 . The value of Sr for the pressed and sintered sample was 0.034 x 10 -3 kg/m 2 but that for alumina doped sample was below the detection limit (0.01 x 10 -3 kg/m 2 ). Al was not detected from the leachate of the alumina doped sample. (author)

  15. Facile hydrothermal synthesis of CeO2 nanopebbles

    Indian Academy of Sciences (India)

    Administrator

    However, to the best of our knowledge the reports on the synthesis of CeO2 ... The base pressure of the XAS chamber was in the range of 10–8 Pa. A Shimadzu ... scopy was investigated to confirm the crystalline quality of CeO2 nanopebbles.

  16. Tuning hydrogen storage in lithium-functionalized BC2N sheets by doping with boron and carbon.

    Science.gov (United States)

    Qiu, Nian-xiang; Zhang, Cheng-hua; Xue, Ying

    2014-10-06

    First-principles calculations are used to explore the strong binding of lithium to boron- and carbon-doped BC2N monolayers (BC2NBC and BC2NCN, respectively) without the formation of lithium clusters. In comparison to BC2N and BC2NCB, lithium-decorated BC2NBC and BC2NCN systems possess stronger s-p and p-p hybridization and, hence, the binding energy is higher. Lithium becomes partially positively charged by donating electron density to the more electronegative atoms of the sheet. Attractive van der Waals interactions are responsible for binding hydrogen molecules around the lithium atoms. Each lithium atom can adsorb three hydrogen molecules on both sides of the sheet, with an average hydrogen binding energy of approximately 0.2 eV, which is in the range required for practical applications. The BC2NBC-Li and BC2NCN-Li complexes can serve as high-capacity hydrogen-storage media with gravimetric hydrogen capacities of 9.88 and 9.94 wt %, respectively. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Facile fabrication of Si-doped TiO2 nanotubes photoanode for enhanced photoelectrochemical hydrogen generation

    Science.gov (United States)

    Dong, Zhenbiao; Ding, Dongyan; Li, Ting; Ning, Congqin

    2018-04-01

    Photoelectrochemical (PEC) water splitting based doping modified one dimensional (1D) titanium dioxide (TiO2) nanostructures provide an efficient method for hydrogen generation. Here we first successfully fabricated 1D Si-doped TiO2 (Ti-Si-O) nanotube arrays through anodizing Ti-Si alloys with different Si amount, and reported the PEC properties for water splitting. The Ti-Si-O nanotube arrays fabricated on Ti-5 wt.% Si alloy and annealed at 600 °C possess higher PEC activity, yielding a higher photocurrent density of 0.83 mA/cm2 at 0 V vs. Ag/AgCl. The maximum photoconversion efficiency was 0.54%, which was 2.7 times the photoconversion efficiency of undoped TiO2.

  18. Homogeneously dispersed CeO2 nanoparticles on exfoliated hexaniobate nanosheets

    Science.gov (United States)

    Marques, Thalles M. F.; Strayer, Megan E.; Ghosh, Anupama; Silva, Alexandre; Ferreira, Odair P.; Fujisawa, Kazunori; Alves da Cunha, Jose R.; Abreu, Guilherme J. P.; Terrones, Mauricio; Mallouk, Thomas E.; Viana, Bartolomeu C.

    2017-12-01

    Hexaniobate nanosheets derived from the parent compound K4Nb6O17 have been decorated with CeO2 nanoparticles by ion exchange with aqueous cerium (IV) solution. Very homogeneous CeO2 nanoparticle decoration of the hexaniobate sheets can be achieved by this method and the resulting composites may absorb visible light. HRTEM images show that ∼3.0 nm diameter CeO2 nanoparticles adhere to hexaniobate nanosheets that are exfoliated and then restacked prior to Ce deposition. The interfacial interaction between CeO2 nanoparticles and nanosheets would be due to an electrostatic attraction mechanism. Raman and XRD measurements have given strong evidence that CeO2 nanoparticles have fluorite structure. EDS, FTIR and XPS results suggest almost complete exchange of TBA+ and K+ by Ce4+. Cerium ion exchange on the acid exchanged parent compound, H2.9K1.1Nb6O17, revealed that the extent of Ce ion exchange is much greater in case of nanosheets, which may be rationalized by the larger surface area available after exfoliation. XPS measurements show that the ratio of Ce4+/Ce3+ is around 4.4, in agreement with the formation of fluorite structure (CeO2). Thus, these CeO2 nanoparticle/nanosheet composites may be useful for catalytic processes.

  19. Hydrogen Storage Characteristics of CNT doped NaAlH4

    International Nuclear Information System (INIS)

    Pukazhselvan, D.; Sterlin Leo Hudson, M.; Bipin Kumar Gupta; Srivastava, O.N.

    2006-01-01

    The current Hydrogen based energy infrastructure required a high energy density consumer friendly hydrogen storage media. Although the desired goals for the hydrogen fueled vehicular transport has not yet met by any hydrogen storage material, complex Sodium Alanate is said to be a promising candidate under this demand due to its high hydrogen storage capacity and the thermodynamically permissible reversible hydrogen storage capacity. However its poor sorption behavior under moderate conditions (NaAlH 4 →Na 3 AlH 6 ; 3.7 wt % vs 50 hrs at ∼170 C and Na 3 AlH 6 →NaH; 1.85 wt % vs 30 hrs at ∼220 C) urges their limited uses in ages. But these limitations can be removed by using catalysts particularly transition elements but the location of catalyst in NaAlH 4 matrix and the possible mechanism is not yet clearly understood. The aim of the present investigation is to improve the overall sorption characteristics of NaAlH 4 by a new light weighted high surface area (1315 sq mtr/gm) material (CNT) admixing and to obtain a best doping level to NaAlH 4 . So far only Ti has been attempted as a suitable catalyst. It is believed that the high surface area of CNT can provide an additional solid-gas (H 2 ) surface/interface and it can produce thermal contact between grains (thermal conductivity Kth of MWCNT: 3000 w/k and Kth of NaAlH 4 : 0.32 w/k) for stimulating their thermally activated dissociation in NaAlH 4 . In parallel with this approach XRD of NaAlH 4 reveals that there was no change in lattice structure after doping by CNT, SEM picture depicts that CNT precipitation in grain surfaces. Catalytic concentration of various mole % of x values finds that x = 8 is the best doping level as it gives 3.3 wt % of hydrogen within 2 hrs. The comparative sorption behavior with Ti:NaAlH 4 also shows CNTs as an optimum alternative catalyst to NaAlH 4 and besides this CNT doped desorbed ingredients shown good re-hydrogenation behavior(3.7 wt % at 8. cycle and 4.2 wt % maximum at

  20. A synthesis method for cobalt doped carbon aerogels with high surface area and their hydrogen storage properties

    Energy Technology Data Exchange (ETDEWEB)

    Tian, H.Y.; Buckley, C.E. [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U 1987, Perth 6845, WA (Australia); CSIRO National Hydrogen Materials Alliance, CSIRO Energy Centre, 10 Murray Dwyer Circuit, Steel River Estate, Mayfield West, NSW 2304 (Australia); Sheppard, D.A.; Paskevicius, M. [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U 1987, Perth 6845, WA (Australia); Hanna, N. [CSIRO Process Science and Engineering, Waterford, WA (Australia)

    2010-12-15

    Carbon aerogels doped with nanoscaled Co particles were prepared by first coating activated carbon aerogels using a wet-thin layer coating process. The resulting metal-doped carbon aerogels had a higher surface area ({proportional_to}1667 m{sup 2} g{sup -1}) and larger micropore volume ({proportional_to}0.6 cm{sup 3} g{sup -1}) than metal-doped carbon aerogels synthesised using other methods suggesting their usefulness in catalytic applications. The hydrogen adsorption behaviour of cobalt doped carbon aerogel was evaluated, displaying a high {proportional_to}4.38 wt.% H{sub 2} uptake under 4.6 MPa at -196 C. The hydrogen uptake capacity with respect to unit surface area was greater than for pure carbon aerogel and resulted in {proportional_to}1.3 H{sub 2} (wt. %) per 500 m{sup 2} g{sup -1}. However, the total hydrogen uptake was slightly reduced as compared to pure carbon aerogel due to a small reduction in surface area associated with cobalt doping. The improved adsorption per unit surface area suggests that there is a stronger interaction between the hydrogen molecules and the cobalt doped carbon aerogel than for pure carbon aerogel. (author)

  1. Influence of mineralizer agents on the growth of crystalline CeO2 nanospheres by the microwave-hydrothermal method

    International Nuclear Information System (INIS)

    Deus, R.C.; Cilense, M.; Foschini, C.R.; Ramirez, M.A.; Longo, E.; Simões, A.Z.

    2013-01-01

    Cystalline ceria (CeO 2 ) nanoparticles have been synthesized by a simple and fast microwave-assisted hydrothermal (MAH) under NaOH, KOH, and NH 4 OH mineralizers added to a cerium ammonium nitrate aqueous solution. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transformed-IR and Raman spectroscopies. Rietveld refinement reveals a cubic structure with a space group Fm3m while infrared data showed few traces of nitrates. Field emission scanning microcopy (FEG-SEM) revealed a homogeneous size distribution of nanometric CeO 2 nanoparticles. The MAH process in KOH and NaOH showed most effective to dehydrate the adsorbed water and decrease the hydrogen bonding effect leaving a weakly agglomerated powder of hydrated ceria. TEM micrographs of CeO 2 synthesized under MAH conditions reveal particles well-dispersed and homogeneously distributed. The MAH enabled cerium oxide to be synthesized at 100 °C for 8 min.

  2. Highly stable hydrogenated gallium-doped zinc oxide thin films grown by DC magnetron sputtering using H2/Ar gas

    International Nuclear Information System (INIS)

    Takeda, Satoshi; Fukawa, Makoto

    2004-01-01

    The effects of water partial pressure (P H 2 O ) on electrical and optical properties of Ga-doped ZnO films grown by DC magnetron sputtering were investigated. With increasing P H 2 O , the resistivity (ρ) of the films grown in pure Ar gas (Ar-films) significantly increased due to the decrease in both free carrier density and Hall mobility. The transmittance in the wavelength region of 300-400 nm for the films also increased with increasing P H 2 O . However, no significant P H 2 O dependence of the electrical and optical properties was observed for the films grown in H 2 /Ar gas mixture (H 2 /Ar-films). Secondary ion mass spectrometry (SIMS) and X-ray diffraction (XRD) analysis revealed that hydrogen concentration in the Ar-films increased with increasing P H 2 O and grain size of the films decreases with increasing the hydrogen concentration. These results indicate that the origin of the incorporated hydrogen is attributed to the residual water vapor in the coating chamber, and that the variation of ρ and transmittance along with P H 2 O of the films resulted from the change in the grain size. On the contrary, the hydrogen concentration in H 2 /Ar-films was almost constant irrespective of P H 2 O and the degree of change in the grain size of the films versus P H 2 O was much smaller than that of Ar-films. These facts indicate that the hydrogen primarily comes from H 2 gas and the adsorption species due to H 2 gas preferentially adsorb to the growing film surface over residual water vapor. Consequently, the effects of P H 2 O on the crystal growth are reduced

  3. Nitrogen-Doped Graphene for Photocatalytic Hydrogen Generation.

    Science.gov (United States)

    Chang, Dong Wook; Baek, Jong-Beom

    2016-04-20

    Photocatalytic hydrogen (H2 ) generation in a water splitting process has recently attracted tremendous interest because it allows the direct conversion of clean and unlimited solar energy into the ideal energy resource of H2 . For efficient photocatalytic H2 generation, the role of the photocatalyst is critical. With increasing demand for more efficient, sustainable, and cost-effective photocatalysts, various types of semiconductor photocatalysts have been intensively developed. In particular, on the basis of its superior catalytic and tunable electronic properties, nitrogen-doped graphene is a potential candidate for a high-performance photocatalyst. Nitrogen-doped graphene also offers additional advantages originating from its unique two-dimensional sp(2) -hybridized carbon network including a large specific surface area and exceptional charge transport properties. It has been reported that nitrogen-doped graphene can play diverse but positive functions including photo-induced charge acceptor/meditator, light absorber from UV to visible light, n-type semiconductor, and giant molecular photocatalyst. Herein, we summarize the recent progress and general aspects of nitrogen-doped graphene as a photocatalyst for photocatalytic H2 generation. In addition, challenges and future perspectives in this field are also discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Influence of metal doping of a MOF-74 framework on hydrogen adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Botas, J.A.; Calleja, G.; Orcajo, M.G. [Rey Juan Carlos Univ., Madrid (Spain). Dept. of Chemical and Energy Technology; Sanchez-Sanchez, M. [CSIC, Madrid (Spain). Inst. de Catalisis y Petroleoquimica

    2010-07-01

    Microporous Metal-Organic Framework (MOF) adsorbents are considered an interesting option for hydrogen storage. Due to their porous nature and unusually high surface areas, these materials show an exceptional H{sub 2} uptake. Unfortunately, their interaction with H{sub 2} molecules is weak, so cryogenic temperatures are required to reach competitive H{sub 2} storage capacities. In this sense, the presence of coordinatively unsaturated and exposed metal centers in some MOF frameworks could increase the affinity for H{sub 2} through stronger metal-H{sub 2} interactions. In this preliminary work, the effect of doping a Zn{sup 2+}-MOF-74 framework with Co{sup 2+}, Cu{sup 2+} and Mg{sup 2+} on its adsorption properties for H{sub 2} has been studied. Characterization studies suggest that the samples prepared have actually the MOF-74 structure, in which the different tested heteroatom ions have been successfully incorporated. The differences in H{sub 2} adsorption at 77 K and 87 K between the MOF-74 samples doped with the mentioned divalent metal ions were discussed as a function of their free pore volume and amount of metal incorporation. (orig.)

  5. Synthesis by sol-gel and characterization of catalysts Ag/Al2O3- CeO2 for the elimination of nitric oxide

    International Nuclear Information System (INIS)

    Zayas R, M.L.

    2005-01-01

    The environmental pollution is one from the big problems to solve at the present time, because the quality of the alive beings life is affected. For such reason, more clean and economic technologies are required, that it conduces to develop new catalytic alternatives to diminish the nitrogen oxides that due to its chemical processes in the environment contribute considerably in the air pollution. The main objective of the present work, is the preparation and characterization of catalytic materials with base of silver supported in simple and mixed aluminium oxides (Al 2 O 3 ) and Cerium oxide (CeO 2 ), and its catalytic evaluation that through of the reduction of nitric oxide (NO) using hydrogen (H 2 ) as reducer agent. It was synthesized alumina (Al 2 O 3 ) and Cerium oxide (CeO 2 ) and mixed oxides (Al 2 O 3 - CeO 2 ), by the sol-gel method and the cerium oxide (CeO 2 ) by precipitation of the cerium nitrate (III) hexa hydrated. The oxides were stabilized thermally at 900 C by 5 hr. The catalysts were prepared by impregnation using silver nitrate (AgNO 3 ), the nominal concentration of Ag was of 5% in weight. The catalysts were reduced at 400 C by 2 hr, in hydrogen flow of 60 cc/min. The characterization of the catalytic materials was carried out through different techniques as: nitrogen adsorption to determine the surface area BET, scanning electron microscopy (SEM) to observe the final morphology of the catalysts, X-ray diffraction (XRD) to identify the crystalline phases of the catalytic materials, Infrared spectroscopy (DRIFT) to know the structural characterization of the catalysts, reduction to programmed temperature (TPR) to evidence the interaction metal-support. The catalytic properties of the catalysts were evaluated in the model reaction NO + H 2 , to determine the activity and selectivity. The results indicate that the preparation technique, the precursors and the thermal treatments that underwent these materials influence in the catalyst and by

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

    Directory of Open Access Journals (Sweden)

    Chunjie Wang

    2014-01-01

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

  7. Influence of screening effect on hydrogen passivation of hole silicon

    CERN Document Server

    Aleksandrov, O V

    2002-01-01

    The simulation of hole silicon passivation during hydrogen diffusion with account of hydrogen-acceptor pairs formation, internal electrical field and screening effect has been carried out. Screening by free carriers of hydrogen and acceptor ions results in shortening their interaction radii and slacking the concentration dependence of hydrogen diffusivity at high level of silicon doping. The consistency of simulated and experimental profiles of holes and hydrogen-acceptor pairs is reached in a broad band of doping levels from 4 x 10 sup 1 sup 4 to 1.2 x 10 sup 2 sup 0 cm sup - sup 3 at the pair binding energy of 0.70-0.79 eV while the radius of the Coulomb interaction of hydrogen and boron ions is equal to 35 A under low doping and decrease with increasing doping level

  8. Preparation of epitaxial YBa2Cu3O7-y films on CeO2-buffered yttria-stabilized zirconia substrates by fluorine-free metalorganic deposition

    International Nuclear Information System (INIS)

    Tsukada, Kenichi; Yamaguchi, Iwao; Sohma, Mitsugu; Kondo, Wakichi; Kamiya, Kunio; Kumagai, Toshiya; Manabe, Takaaki

    2007-01-01

    Epitaxial YBa 2 Cu 3 O 7-y (YBCO) films of 120-550 nm thickness have been prepared by fluorine-free metalorganic deposition using a metal acetylacetonate-based coating solution on yttria-stabilized zirconia (YSZ) substrates with an evaporated CeO 2 buffer layer. The YBCO films were highly (0 0 1)-oriented by X-ray diffraction θ-2θ scanning and φ scanning. The YBCO films 120-400 nm in thickness demonstrated high critical current densities (J c ) with an average in excess of 3 MA/cm 2 at 77 K using an inductive method. In particular, a 210-nm-thick film showed a J c of 4.5 MA/cm 2 . These excellent properties are attributed to the high crystallinity, small in-plane fluctuation due to high epitaxy and to the microstructure free from grain boundaries in the YBCO films. Further increase of film thickness increased the fraction of irregularities, i.e., precipitates and micropores, in the film surfaces, resulting in lower J c values

  9. Structural analysis of nickel doped cerium oxide catalysts for fuel reforming in solid oxide fuel cells

    Science.gov (United States)

    Cavendish, Rio

    As world energy demands increase, research into more efficient energy production methods has become imperative. Heterogeneous catalysis and nanoscience are used to promote chemical transformations important for energy production. These concepts are important in solid oxide fuel cells (SOFCs) which have attracted attention because of their potential to provide an efficient and environmentally favorable power generation system. The SOFC is also fuel-flexible with the ability to run directly on many fuels other than hydrogen. Internal fuel reforming directly in the anode of the SOFC would greatly reduce the cost and complexity of the device. Methane is the simplest hydrocarbon and a main component in natural gas, making it useful when testing catalysts on the laboratory scale. Nickel (Ni) and gadolinium (Gd) doped ceria (CeO 2) catalysts for potential use in the SOFC anode were synthesized with a spray drying method and tested for catalytic performance using partial oxidation of methane and steam reforming. The relationships between catalytic performance and structure were then investigated using X-ray diffraction, transmission electron microscopy, and environmental transmission electron microscopy. The possibility of solid solutions, segregated phases, and surface layers of Ni were explored. Results for a 10 at.% Ni in CeO2 catalyst reveal a poor catalytic behavior while a 20 at.% Ni in CeO2 catalyst is shown to have superior activity. The inclusion of both 10 at.% Gd and 10 at.% Ni in CeO2 enhances the catalytic performance. Analysis of the presence of Ni in all 3 samples reveals Ni heterogeneity and little evidence for extensive solid solution doping. Ni is found in small domains throughout CeO2 particles. In the 20 at.% Ni sample a segregated, catalytically active NiO phase is observed. Overall, it is found that significant interaction between Ni and CeO2 occurs that could affect the synthesis and functionality of the SOFC anode.

  10. Inverse CeO2sbnd Fe2O3 catalyst for superior low-temperature CO conversion efficiency

    Science.gov (United States)

    Luo, Yongming; Chen, Ran; Peng, Wen; Tang, Guangbei; Gao, Xiaoya

    2017-09-01

    The paper presents a rational design of highly efficient and affordable catalysts for CO oxidation with a low operating temperature. A series of ceria-iron catalysts were inversely built via a co-precipitation method. The catalytic activity of low-temperature CO oxidation was much higher with CeO2-modified Fe2O3 (CeO2sbnd Fe2O3) than with Fe2O3-modified CeO2 (Fe2O3sbnd CeO2). In particular, the 7.5% CeO2sbnd Fe2O3 catalyst had the highest activity, reaching 96.17% CO conversion at just 25 °C. Catalyst characterization was carried out to explore the cause of the significantly different CO conversion efficiencies between the Fe2O3sbnd CeO2 and Fe2O3sbnd CeO2 catalysts. HRTEM showed a significant inhomogeneous phase in 7.5% CeO2sbnd Fe2O3 with small CeO2 nanoparticles highly dispersed on the rod-shaped Fe2O3 surface. Furthermore, the 7.5% CeO2sbnd Fe2O3 composite catalyst exhibited the highest ratios of Fe2+/Fe3+ and Ce3+/Ce4+ as well as the largest pore volume. These properties are believed to benefit the CO conversion in 7.5% CeO2sbnd Fe2O3.

  11. Fabrication, structure, and enhanced photocatalytic properties of hierarchical CeO2 nanostructures/TiO2 nanofibers heterostructures

    International Nuclear Information System (INIS)

    Cao, Tieping; Li, Yuejun; Wang, Changhua; Wei, Liming; Shao, Changlu; Liu, Yichun

    2010-01-01

    Combining the versatility of electrospinning technique and hydrothermal growth of nanostructures enabled the fabrication of hierarchical CeO 2 /TiO 2 nanofibrous mat. The as-prepared hierarchical heterostructure consisted of CeO 2 nanostructures growing on the primary TiO 2 nanofibers. Interestingly, not only were secondary CeO 2 nanostructures successfully grown on TiO 2 nanofibers substrates, but also the CeO 2 nanostructures were uniformly distributed without aggregation on TiO 2 nanofibers. By selecting different alkaline source, CeO 2 /TiO 2 heterostructures with CeO 2 nanowalls or nanoparticles were facilely fabricated. The photocatalytic studies suggested that the CeO 2 /TiO 2 heterostructures showed enhanced photocatalytic efficiency of photodegradation of dye pollutants compared with bare TiO 2 nanofibers under UV light irradiation.

  12. Green chemical approach towards the synthesis of CeO2 doped with seashell and its bacterial applications intermediated with fruit extracts.

    Science.gov (United States)

    Arasu, Mariadas Valan; Thirumamagal, R; Srinivasan, M P; Al-Dhabi, Naif Abdullah; Ayeshamariam, A; Saravana Kumar, D; Punithavelan, N; Jayachandran, M

    2017-08-01

    Nanomaterials of CeO 2 with A. vera were synthesized by using simple chemical method. Grapes drops are used as an oxidizing agent. Structural and morphological studies of nanomaterials of cerium oxide (CeO 2 ), were studied for combustion method of preparation. The precursor solution was initialized by a hydrothermal reaction. Cerium hydroxyl carbonate precursors which involves cerium (III) nitrate Ce(NO 3 ) 3 . 6 H 2 O with (1.0M) of seashell powder, 3% A. vera, extracts, grapes and pomegranate drops and this complex solution was used to produce the CeO 2 powder particles. We have prepared another sample with 5% of Aloe vera extract and found that 3% Aloe vera extract has lesser grain size and enhanced band gap values, so the article explained the sample analysis of combination with 3% extract of Aloe vera. The product has the rod pattern which was the unusual features appear to originate from the unique crystal chemistry aspects. From the optical absorption spectrum, it has been shown that the CeO 2 rods have 3.847eV of direct band gap energy. The minimum inhibitory concentration (MIC) values of the synthesized compounds exhibited activity towards various microbial pathogens such as B. subtilis (15μg/mL), S. aureus (50μg/mL), S. epidermidis (20μg/mL), E. faecalis (25μg/mL) and towards E. coli (100μg/mL), K. pneumoniae (50μg/mL) and P. aeruginosa (75μg/mL) respectively. The tests on bacterial activities confirmed that the CeO 2 rods are suitable hand for the biological applications. The seashell structure and the phytochemical contents of A. vera might enhance its bacterial activities. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Eu2+-doped OH− free calcium aluminosilicate glass: A phosphor for smart lighting

    International Nuclear Information System (INIS)

    Lima, S.M.; Andrade, L.H.C.; Rocha, A.C.P.; Silva, J.R.; Farias, A.M.; Medina, A.N.; Baesso, M.L.; Nunes, L.A.O.; Guyot, Y.; Boulon, G.

    2013-01-01

    In this paper, a broad emission band from Eu 2+ -doped OH − free calcium aluminosilicate glass is reported. By changing the excitation wavelengths, the results showed it is possible to tune the emission from green to orange, what combined with the scattered light from the same blue LED used for excitation, provided a color rendering index of 71 and a correlated color temperature of 6550 K. Our preliminary tests indicate this material as a promising phosphor towards the development of smart lighting devices. -- Highlights: • We report a broad emission band from Eu 2+ -doped OH − free calcium aluminosilicate glass. • The maximum emission peak can be tune from green to orange region. • The test with a LED provided a color rendering index of 71 and a correlated color temperature of 6550 K

  14. Inverted opal luminescent Ce-doped silica glasses

    Directory of Open Access Journals (Sweden)

    R. Scotti

    2006-01-01

    Full Text Available Inverted opal Ce-doped silica glasses (Ce : Si molar ratio 1 ⋅ 10−3 were prepared by a sol-gel method using opals of latex microspheres as templates. The rare earth is homogeneously dispersed in silica host matrix, as evidenced by the absence of segregated CeO2, instead present in monolithic Ce-doped SG with the same cerium content. This suggests that the nanometric dimensions of bridges and junctions of the host matrix in the inverted opal structures favor the RE distribution avoiding the possible segregation of CeO2.

  15. Quasi-zero-dimensional cobalt-doped CeO2 dots on Pd catalysts for alcohol electro-oxidation with enhanced poisoning-tolerance.

    Science.gov (United States)

    Tan, Qiang; Zhu, Haiyan; Guo, Shengwu; Chen, Yuanzhen; Jiang, Tao; Shu, Chengyong; Chong, Shaokun; Hultman, Benjamin; Liu, Yongning; Wu, Gang

    2017-08-31

    Deactivation of an anode catalyst resulting from the poisoning of CO ad -like intermediates is one of the major problems for methanol and ethanol electro-oxidation reactions (MOR & EOR), and remains a grand challenge towards achieving high performance for direct alcohol fuel cells (DAFCs). Herein, we report a new approach for the preparation of ultrafine cobalt-doped CeO 2 dots (Co-CeO 2 , d = 3.6 nm), which can be an effective anti-poisoning promoter for Pd catalysts towards MOR and EOR in alkaline media. Compared to Pd/CeO 2 and pure Pd, the hybrid Pd/Co-CeO 2 nanocomposite catalyst exhibited a much enhanced activity and remarkable anti-poisoning ability for both MOR and EOR. The nanocomposite catalyst showed much higher mass activity (4×) than a state-of-the-art PtRu catalyst. The promotional mechanism was elucidated using extensive characterization and density-functional theory (DFT). A bifunctional effect of the Co-CeO 2 dots was discovered to be due to (i) an enhanced electronic interaction between Co-CeO 2 and Pd dots and (ii) the increased oxygen storage capacity of Co-CeO 2 dots to facilitate the oxidation of CO ad . Therefore, the Pd/Co-CeO 2 nanocomposite appears to be a promising catalyst for advanced DAFCs with low cost and high performance.

  16. Enhanced photocatalytic activity for H2 evolution under irradiation of UV-vis light by Au-modified nitrogen-doped TiO2.

    Science.gov (United States)

    Zhao, Weirong; Ai, Zhuyu; Dai, Jiusong; Zhang, Meng

    2014-01-01

    Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV-vis light, respectively. The samples were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectroscopy (PL), and photoelectrochemical characterizations. DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV-vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2). This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR) effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of TiO2 and increased the utilization of solar energy, greatly

  17. Enhanced photocatalytic activity for H2 evolution under irradiation of UV-vis light by Au-modified nitrogen-doped TiO2.

    Directory of Open Access Journals (Sweden)

    Weirong Zhao

    Full Text Available BACKGROUND PURPOSE: Photocatalytic water splitting for hydrogen evolution is a potential way to solve many energy and environmental issues. Developing visible-light-active photocatalysts to efficiently utilize sunlight and finding proper ways to improve photocatalytic activity for H2 evolution have always been hot topics for research. This study attempts to expand the use of sunlight and to enhance the photocatalytic activity of TiO2 by N doping and Au loading. METHODS: Au/N-doped TiO2 photocatalysts were synthesized and successfully used for photocatalytic water splitting for H2 evolution under irradiation of UV and UV-vis light, respectively. The samples were characterized using X-ray diffraction (XRD, transmission electron microscopy (TEM, X-ray photoelectron spectroscopy (XPS, UV-vis diffuse reflectance spectroscopy (DRS, photoluminescence spectroscopy (PL, and photoelectrochemical characterizations. RESULTS: DRS displayed an extension of light absorption into the visible region by doping of N and depositing with Au, respectively. PL analysis indicated electron-hole recombination due to N doping and an efficient inhibition of electron-hole recombination due to the loaded Au particles. Under the irradiation of UV light, the photocatalytic hydrogen production rate of the as-synthesized samples followed the order Au/TiO2 > Au/N-doped TiO2 > TiO2 > N-doped TiO2. While under irradiation of UV-vis light, the N-TiO2 and Au/N-TiO2 samples show higher H2 evolution than their corresponding nitrogen-free samples (TiO2 and Au/TiO2. This inconsistent result could be attributed to the doping of N and the surface plasmonic resonance (SPR effect of Au particles extending the visible light absorption. The photoelectrochemical characterizations further indicated the enhancement of the visible light response of Au/N-doped TiO2. CONCLUSION: Comparative studies have shown that a combination of nitrogen doping and Au loading enhanced the visible light response of

  18. Optical properties of CeO 2 thin films

    Indian Academy of Sciences (India)

    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 ...

  19. The influence of Ti doping and annealing on Ce_2Ti_2O_7 flash memory devices

    International Nuclear Information System (INIS)

    Kao, Chyuan Haur; Chen, Su Zhien; Luo, Yang; Chiu, Wang Ting; Chiu, Shih Wei; Chen, I Chien; Lin, Chan-Yu; Chen, Hsiang

    2017-01-01

    Highlights: • Ce_2Ti_2O_7 flash memories have been fabricated. • Material quality can be improved by annealing. • The memory performance can be enhanced by Ti doping. • Ti doping and annealing can reinforce crystallization. - Abstract: In this research, a CeO_2 film with Ti doping was used as a trapping layer in metal oxide high-K-oxide-Si (MOHOS)-type memory devices. Since incorporation of Ti atoms into the film could fix dangling bonds and defects, the Ce_2Ti_2O_7 trapping layer with annealing treatment could have a larger memory window and a faster programming/erasing speed. To confirm the origin, multiple material analyses indicate that annealing at an appropriate temperature and Ti doping could enhance crystallization. The Ce_2Ti_2O_7-based memory device is promising for future industrial flash memory applications.

  20. Influence of screening effect on hydrogen passivation of hole silicon

    International Nuclear Information System (INIS)

    Aleksandrov, O.V.

    2002-01-01

    The simulation of hole silicon passivation during hydrogen diffusion with account of hydrogen-acceptor pairs formation, internal electrical field and screening effect has been carried out. Screening by free carriers of hydrogen and acceptor ions results in shortening their interaction radii and slacking the concentration dependence of hydrogen diffusivity at high level of silicon doping. The consistency of simulated and experimental profiles of holes and hydrogen-acceptor pairs is reached in a broad band of doping levels from 4 x 10 14 to 1.2 x 10 20 cm -3 at the pair binding energy of 0.70-0.79 eV while the radius of the Coulomb interaction of hydrogen and boron ions is equal to 35 A under low doping and decrease with increasing doping level [ru

  1. Facile preparation of self-healing superhydrophobic CeO2 surface by electrochemical processes

    Science.gov (United States)

    Nakayama, Katsutoshi; Hiraga, Takuya; Zhu, Chunyu; Tsuji, Etsushi; Aoki, Yoshitaka; Habazaki, Hiroki

    2017-11-01

    Herein we report simple electrochemical processes to fabricate a self-healing superhydrophobic CeO2 coating on Type 304 stainless steel. The CeO2 surface anodically deposited on flat stainless steel surface is hydrophilic, although high temperature-sintered and sputter-deposited CeO2 surface was reported to be hydrophobic. The anodically deposited hydrophilic CeO2 surface is transformed to hydrophobic during air exposure. Specific accumulation of contaminant hydrocarbon on the CeO2 surface is responsible for the transformation to hydrophobic state. The deposition of CeO2 on hierarchically rough stainless steel surface produces superhydrophobic CeO2 surface, which also shows self-healing ability; the surface changes to superhydrophilic after oxygen plasma treatment but superhydrophobic state is recovered repeatedly by air exposure. This work provides a facile method for preparing a self-healing superhydrophobic surface using practical electrochemical processes.

  2. Highly porous CeO2 nanostructures prepared via combustion synthesis for supercapacitor applications

    DEFF Research Database (Denmark)

    Kadirvelayutham, Prasanna; Santhoshkumar, P.; Jo, Yong Nam

    2017-01-01

    We report highly porous CeO2 nanostructures (CeO2 NSs) suitable for supercapacitor applications, synthesized using a fast and cost effective combustion approach. Due to its prominent valence states of Ce3+/Ce4+, CeO2 has emerged as a promising pseudocapacitive material. The drawback of using CeO2...... as a supercapacitor electrode is its poor electrical conductivity. We overcame this drawback of CeO2 by creating oxygen vacancies on its surface, which act to enhance its electrical conductivity. The physical interpretation of the as-synthesized CeO2 NSs shows that they have dense active sites and diffusion pathways...... that enhance the performance of the electrode in a supercapacitor. Electrodes prepared using the synthesized CeO2 NSs exhibited the initial specific capacitance of 134.6 F g-1 and superior cycling stability of 92.5% after 1000 cycles at a constant current density of 1 A g-1, indicating their potential...

  3. Morphologically controlled synthesis, structural and optical properties of CeO2/SnO2 nanocomposites

    Directory of Open Access Journals (Sweden)

    S. Usharani

    2017-09-01

    Full Text Available CeO2/SnO2 nanocomposites with different dimensional nanostructures were synthesized by a wet chemical method, using various surfactants such as SDS, CTAB and Triton X-100. The prepared CeO2/SnO2 samples were analyzed by X-ray diffraction (XRD, Fourier transform infrared (FTIR, Transmission electron microscopy (TEM, UV-Diffuse Reflectance Spectroscopy (UV-DRS, and Photoluminescence (PL spectroscopy. The XRD patterns reveal the presence of a mixed phase of SnO2 and CeO2; The TEM analysis showed the mixed morphology of uniformly dispersed spherical with ellipsoidal shape in the SDS assisted CeO2/SnO2 nanocomposites; whereas the nanostructure with spherical with hexagonal shapes was observed for the Triton X-100 assisted CeO2/SnO2 nanocomposites. The one dimensional (1D nanorod like structure observed for the CTAB assisted CeO2/SnO2 nanocomposites shows CTAB acting as a face-specific capping agent to form rod-shaped micelles. The room temperature photoluminescence emission studies of the CeO2/SnO2 nanocomposites showed strong peaks in the UV region, and several peaks in the visible region, which are likely to have originated from the oxygen vacancies and are potential materials for optoelectronic device applications. The UV results showed the absorption edges shifted to a high energy region and the blue shifts that occurred in all the samples.

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

    DEFF Research Database (Denmark)

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

    2012-01-01

    Single-crystalline porous CeO2 nanocrystals, with sizes of ∼20 nm and pore diameters of 1-2 nm, were synthesized successfully using a hydrothermal method. Using electron tomography, we imaged the three-dimensional structure of the pores in the nanocrystals and found that the oriented aggregation ...... 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. Hydrogen doping of Indium Tin Oxide due to thermal treatment of hetero-junction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ritzau, Kurt-Ulrich, E-mail: kurt-ulrich.ritzau@ise.fraunhofer.de [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstrasse 2, 79110 Freiburg (Germany); Behrendt, Torge [Infineon Technologies, Max-Planck-Straße 5, 59581 Warstein (Germany); Palaferri, Daniele [Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot, Sorbonne Paris Cité, CNRS—UMR 7162, 75013 Paris (France); Bivour, Martin; Hermle, Martin [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstrasse 2, 79110 Freiburg (Germany)

    2016-01-29

    Indium Tin Oxide (ITO) layers in silicon hetero junction solar cells change their electrical and optical properties when exposed to temperature treatments. Hydrogen which effuses from underlying amorphous silicon layers is identified to dope the ITO layer. This leads to an additional increase in conductivity. In this way an almost isolating ITO can become degenerately doped through temperature treatments. The resulting carrier density in the range of 10{sup 20} cm{sup −3} leads to a substantial increase in free carrier absorption, which in turn leads to an increased parasitic absorption in the cell device. Thus hydrogen effusion in silicon hetero-junction (SHJ) solar cells does not only affect the degradation of amorphous silicon (a-Si:H) passivation of crystalline silicon (c-Si), but also the electrical and optical properties of both front and back ITO layers. This leads to the further design rule for SHJ solar cells, meaning that ITO properties have to be optimized in the state after modification during temperature treatment. - Highlights: • ITO is additionally doped by heat treatment of silicon hetero-junction solar cells. • The discovered effect turns an almost isolating ITO into a degenerately doped TCO. • TCO properties have to be considered as measured in the final cell.

  6. Computational study of pristine and titanium-doped sodium alanates for hydrogen storage applications

    Science.gov (United States)

    Dathar, Gopi Krishna Phani

    formalism as implemented in CASTEP (Cambridge Serial Total Energy Package) is used to study the structure and energetics of pristine and Ti-doped sodium alanates. From investigations of various models of sodium alanates with Ti dopants, it is shown that the difference between the energy required for Ti→SNa (Ti-substituted Na at the lattice site on the surface) and Ti→TI (Ti placed on top of the surface interstitial SI site) is 0.003 eV atom-1, and is minimal compared to other models. Since less energy is required for Ti→S Na and Ti→TI, these two sites (SNa and T I) would be preferred by the Ti dopants. In Ti→SNa model, Ti is coordinated to two aluminum and seven hydrogen atoms resulting in the possible formation of a TiAl2H7 complex. At elevated temperatures (423 and 448 K), the number of aluminum atoms coordinating with titanium in the complex increase from two (at distances in the 2.6-2.7 A range) to five (at distances in the 2.6-2.7 A range). Besides the formation of a Ti-Al-H complex, Al-Al association (with a 2.97 A bond length) is also seen from the DFT-MD results. In the case of Ti→TI, Ti is coordinated to two aluminum and two hydrogen atoms resulting in the possible formation of a TiAl2H2 complex. TiAl2 H2 complex becomes TiAl3H6 and TiAl 3H7 at elevated temperatures of 423 and 448 K, respectively. The investigation of thermodynamics pathways in Ti-doped sodium alanates illustrates a three step reaction pathway to the formation of TiAl3 (Ti and AlH3 after the first reaction, TiAl after the second and finally TiAl3). This investigation also suggests aluminum in its +3 oxidation state present in aluminum hydride species is responsible in the formation of Ti-Al alloys. From kinetics studies, the proposed mechanism is related to transition from AlH4- to AlH6 3-. The rate limiting step is determined to be associated with hydrogen evolution from association of AlH3 species nucleating aluminum phase. This step is 15 kJ/mol higher than the nearest highest

  7. Thermochemical reactivity of 5–15 mol% Fe, Co, Ni, Mn-doped cerium oxides in two-step water-splitting cycle for solar hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Gokon, Nobuyuki, E-mail: ngokon@eng.niigata-u.ac.jp [Center for Transdisciplinary Research, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181 (Japan); Suda, Toshinori [Graduate School of Science and Technology, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan); Kodama, Tatsuya [Department of Chemistry & Chemical Engineering, Faculty of Engineering, Niigata University, 8050 Ikarashi 2-nocho, Niigata 950-2181 (Japan)

    2015-10-10

    Highlights: • 5–15 mol% M-doped ceria are examined for thermochemical two-step water-splitting. • 5 mol% Fe- and Co-doped ceria have stoichiometric production of oxygen and hydrogen. • 10–15 mol% Fe- and Mn-doped ceria showed near-stoichiometric production. - Abstract: The thermochemical two-step water-splitting cycle using transition element-doped cerium oxide (M–CeO{sub 2−δ}; M = Fe, Co, Ni, Mn) powders was studied for hydrogen production from water. The oxygen/hydrogen productivity and repeatability of M–CeO{sub 2−δ} materials with M doping contents in the 5–15 mol% range were examined using a thermal reduction (TR) temperature of 1500 °C and water decomposition (WD) temperatures in the 800–1150 °C range. The temperature, steam partial pressure, and steam flow rate in the WD step had an impact on the hydrogen productivity and production rate. 5 mol% Fe- and Co-doped CeO{sub 2−δ} enhances hydrogen productivity by up to 25% on average compared to undoped CeO{sub 2}, and shows stable repeatability of stoichiometric oxygen and hydrogen production for the cyclic thermochemical two-step water-splitting reaction. In addition, 5 mol% Mn-doped CeO{sub 2−δ}, 10 and 15 mol% Fe- and Mn-doped CeO{sub 2−δ} show near stoichiometric reactivities.

  8. Nanoporous materials for hydrogen storage and H2/D2 isotope separation

    International Nuclear Information System (INIS)

    Oh, Hyunchul

    2014-01-01

    This thesis presents a study of hydrogen adsorption properties at RT with noble metal doped porous materials and an efficient separation of hydrogen isotopes with nanoporous materials. Most analysis is performed via thermal desorption spectra (TDS) and Sieverts-type apparatus. The result and discussion is presented in two parts; Chapter 4 focuses on metal doped nanoporous materials for hydrogen storage. Cryogenic hydrogen storage by physisorption on porous materials has the advantage of high reversibility and fast refuelling times with low heat evolution at modest pressures. At room temperature, however, the physisorption mechanism is not abEle to achieve enough capacity for practical application due to the weak van der Waals interaction, i.e., low isosteric heats for hydrogen sorption. Recently, the ''spillover'' effect has been proposed by R. Yang et al. to enhance the room temperature hydrogen storage capacity. However, the mechanism of this storage enhancement by decoration of noble metal particles inside high surface area supports is not yet fully understood and still under debate. In this chapter, noble metal (Pt / Pd) doped nanoporous materials (i.e. porous carbon, COFs) have been investigated for room temperature hydrogen storage. Their textural properties and hydrogen storage capacity are characterized by various analytic techniques (e.g. SEM, HRTEM, XRD, BET, ICP-OES, Thermal desorption spectra, Sievert's apparatus and Raman spectroscopy). Firstly, Pt-doped and un-doped templated carbons possessing almost identical textural properties were successfully synthesized via a single step wet impregnation method. This enables the study of Pt catalytic activities and hydrogen adsorption kinetics on porous carbons at ambient temperature by TDS after H 2 /D 2 gas exposure and PCT measurement, respectively. While the H 2 adsorption kinetics in the microporous structure is enhanced by Pt catalytic activities (spillover), only a small enhancement of the hydrogen

  9. Electrochemical Hydrogen Storage in Facile Synthesized Co@N-Doped Carbon Nanoparticle Composites.

    Science.gov (United States)

    Zhou, Lina; Qu, Xiaosheng; Zheng, Dong; Tang, Haolin; Liu, Dan; Qu, Deyang; Xie, ZhiZhong; Li, Junsheng; Qu, Deyu

    2017-11-29

    A Co@nitrogen-doped carbon nanoparticle composite was synthesized via a facile molecular self-assembling procedure. The material was used as the host for the electrochemical storage of hydrogen. The hydrogen storage capacity of the material was over 300 mAh g -1 at a rate of 100 mAg -1 . It also exhibited superior stability for storage of hydrogen, high rate capability, and good cyclic life. Hybridizing metallic cobalt nanoparticle with nitrogen-doped mesoporous carbon is found to be a good approach for the electrochemical storage of hydrogen.

  10. Improving hydrogen storage in Ni-doped carbon nanospheres

    Energy Technology Data Exchange (ETDEWEB)

    Zubizarreta, L.; Menendez, J.A.; Pis, J.J.; Arenillas, A. [Instituto Nacional del Carbon, CSIC, Apartado 73, 33080 Oviedo (Spain)

    2009-04-15

    The effect of nickel distribution and content in Ni-doped carbon nanospheres on hydrogen storage capacity under conditions of moderate temperature and pressure was studied. It was found that the nickel distribution, obtained by using different doping techniques and conditions, has a noticeable influence on hydrogen storage capacity. The samples with the most homogeneous nickel distribution, obtained by pre-oxidising the carbon nanospheres, displayed the highest storage capacity. In addition, storage capacity is influenced by the amount of nickel. It was found a higher storage capacity in samples containing 5 wt.% of Ni. This is due to the greater interactions between the nickel and the support that produce a higher activation of the solid through a spillover effect. (author)

  11. Heteroaggregation, transformation and fate of CeO2 nanoparticles in wastewater treatment

    International Nuclear Information System (INIS)

    Barton, Lauren E.; Auffan, Melanie; Olivi, Luca; Bottero, Jean-Yves; Wiesner, Mark R.

    2015-01-01

    Wastewater Treatment Plants (WWTPs) are a key pathway by which nanoparticles (NPs) enter the environment following release from NP-enabled products. This work considers the fate and exposure of CeO 2 NPs in WWTPs in a two-step process of heteroaggregation with bacteria followed by the subsequent reduction of Ce(IV) to Ce(III). Measurements of NP association with solids in sludge were combined with experimental estimates of reduction rate constants for CeO 2 NPs in Monte Carlo simulations to predict the concentrations and speciation of Ce in WWTP effluents and biosolids. Experiments indicated preferential accumulation of CeO 2 NPs in biosolids where reductive transformation would occur. Surface functionalization was observed to impact both the distribution coefficient and the rates of transformation. The relative affinity of CeO 2 NPs for bacterial suspensions in sludge appears to explain differences in the observed rates of Ce reduction for the two types of CeO 2 NPs studied. - Highlights: • We combine experimental and computational methods to track CeO 2 NPs through WWTPs. • We investigate the importance of environmental transformations on NP exposure. • We estimate the concentrations of CeO 2 NPs and reductive transformation byproducts. - CeO 2 nanoparticles that are released to the waste stream will preferentially associate with the solid phase (∼96%), where they will undergo significant transformation (∼50%)

  12. Enhancing optical gains in Si nanocrystals via hydrogenation and cerium ion doping

    International Nuclear Information System (INIS)

    Wang, Dong-Chen; Li, Yan-Li; Song, Sheng-Chi; Guo, Wen-Ping; Lu, Ming; Chen, Jia-Rong

    2014-01-01

    We report optical gain enhancements in Si nanocrystals (Si-NCs) via hydrogenation and Ce 3+ ion doping. Variable stripe length technique was used to obtain gains. At 0.3 W/cm 2 pumping power density of pulsed laser, net gains were observed together with gain enhancements after hydrogenation and/or Ce 3+ ion doping; gains after loss corrections were between 89.52 and 341.95 cm −1 ; and the photoluminescence (PL) lifetime was found to decrease with the increasing gain enhancement. At 0.04 W/cm 2 power density, however, no net gain was found and the PL lifetime increased with the increasing PL enhancement. The results were discussed according to stimulated and spontaneous excitation and de-excitation mechanisms of Si-NCs.

  13. Synthesis of nanocrystalline CeO2 particles by different emulsion methods

    International Nuclear Information System (INIS)

    Supakanapitak, Sunisa; Boonamnuayvitaya, Virote; Jarudilokkul, Somnuk

    2012-01-01

    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 CeO 2 . 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 m 2 /g, respectively. The CeO 2 powders synthesized by the CEAs are the smallest average particle size, and the highest surface area. Finally, the CeO 2 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 CeO 2 . - Graphical Abstract: The emulsion droplet size distribution and the TEM images of CeO 2 prepared by different methods: reversed micelle (RM), emulsion liquid membrane (ELM) and colloidal emulsion aphrons (CEAs). Highlights: ► Nano-sized CeO 2 was successfully prepared by three different emulsion methods. ► The colloidal emulsion aphrons method producing CeO 2 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.

  14. Investigations on Cs-free alternative materials for negative hydrogen ion formation

    Energy Technology Data Exchange (ETDEWEB)

    Kurutz, Uwe

    2017-01-19

    inherently present volume processes for negative hydrogen ions which allows for assessing a material's direct and indirect impact on the negative ion density. Furthermore, two reference cases are investigated: an in-situ caesiated stainless steel sample and a pure stainless steel sample, where the former represents the current most efficient direct pathway and the latter provides insight into the negative ion background determined by the volume processes. Different materials known from literature to produce negative ions either directly or indirectly, like pure tantalum and tungsten, different boron-doped and non-doped diamond samples as well as two materials characterized by an intrinsic low work function (a molybdenum sample doped with lanthanum and a lanthanum hexaboride sample) have been investigated. The investigations showed that compared to the pure stainless steel reference sample neither tantalum, tungsten nor any of the diamond samples result in an increment of the negative ion density. Furthermore, all diamond materials show clear indications for plasma induced erosion (modified surface structure and reduced sample weight) and they significantly influence the plasma volume by an adverse effect on the negative ion production. In contrast, both samples with intrinsically low work function result in an increased negative ion density of up to 60 % compared to the stainless steel reference. This enhancement is still significantly lower than the enhancing effect measured for Cs evaporation, which leads to an increment of up to a factor of 2.5, attributable to the still higher work functions of about 3 eV compared to 2.1 eV for Cs. In conclusion, following investigations on Cs-free alternative materials should be focused on low work function materials.

  15. Investigations on Cs-free alternative materials for negative hydrogen ion formation

    International Nuclear Information System (INIS)

    Kurutz, Uwe

    2017-01-01

    present volume processes for negative hydrogen ions which allows for assessing a material's direct and indirect impact on the negative ion density. Furthermore, two reference cases are investigated: an in-situ caesiated stainless steel sample and a pure stainless steel sample, where the former represents the current most efficient direct pathway and the latter provides insight into the negative ion background determined by the volume processes. Different materials known from literature to produce negative ions either directly or indirectly, like pure tantalum and tungsten, different boron-doped and non-doped diamond samples as well as two materials characterized by an intrinsic low work function (a molybdenum sample doped with lanthanum and a lanthanum hexaboride sample) have been investigated. The investigations showed that compared to the pure stainless steel reference sample neither tantalum, tungsten nor any of the diamond samples result in an increment of the negative ion density. Furthermore, all diamond materials show clear indications for plasma induced erosion (modified surface structure and reduced sample weight) and they significantly influence the plasma volume by an adverse effect on the negative ion production. In contrast, both samples with intrinsically low work function result in an increased negative ion density of up to 60 % compared to the stainless steel reference. This enhancement is still significantly lower than the enhancing effect measured for Cs evaporation, which leads to an increment of up to a factor of 2.5, attributable to the still higher work functions of about 3 eV compared to 2.1 eV for Cs. In conclusion, following investigations on Cs-free alternative materials should be focused on low work function materials.

  16. Density functional theory study of hydrogenation mechanism in Fe-doped Mg(0 0 0 1) surface

    International Nuclear Information System (INIS)

    Wu Guangxin; Zhang Jieyu; Wu Yongquan; Li Qian; Chou Kuochih; Bao Xinhua

    2009-01-01

    Using density functional theory (DFT) in combination with nudged elastic band (NEB) method, the dissociative chemisorptions and diffusion processes of hydrogen on both pure and Fe-doped Mg(0 0 0 1) surfaces are studied. Firstly, the dissociation pathway of H 2 and the relative barrier were investigated. The calculated dissociation barrier (1.08 eV) of hydrogen molecule on a pure Mg(0 0 0 1) surface is in good agreement with comparable experimental and theoretical studies. For the Fe-doped Mg(0 0 0 1) surface, the activated barrier decreases to 0.101 eV due to the strong interaction between the s orbital of H and the d orbital of Fe. Then, the diffusion processes of atomic hydrogen on pure and Fe-doped Mg(0 0 0 1) are presented. The obtained diffusion barrier to the first subsurface is 0.45 eV and 0.98 eV, respectively. Finally, Chou method was used to investigate the hydrogen sorption kinetic mechanism of pure MgH 2 and Mg mixed with 5 at.% Fe atoms composites. The obtained activation energies are 0.87 ± 0.02 and 0.31 ± 0.01 eV for H 2 dissociation on the pure surface and H atom diffusion in Fe-doped Mg surfaces, respectively. It suggests that the rate-controlling step is dissociation of H 2 on the pure Mg surface while it is diffusion of H atom in the Fe-doped Mg surface. And both of fitting data are matching well with our calculation results.

  17. Low-cost fabrication of highly sensitive room temperature hydrogen sensor based on ordered mesoporous Co-doped TiO2 structure

    Science.gov (United States)

    Li, Zhong; Haidry, Azhar Ali; Wang, Tao; Yao, Zheng Jun

    2017-07-01

    The development of cost-effective gas sensors with improved sensing properties and minimum power consumption for room temperature hydrogen leakage monitoring is in increasing demand. In this context, this report focus on the facile fabrication of ordered mesoporous TiO2 via evaporation-induced self-assembly route. With the controlled doping threshold (3%Co-TiO2), the output resistance change to 1000 ppm H2 is ˜4.1 × 103 with the response time of 66 s. The sensor response exhibits power law dependence with an increase in the hydrogen concentration, where the power law coefficient was found not only specific to the kind of target gas but also related to temperature. Further, the effect of structure integrity with doping level and humidity on sensing characteristics is interpreted in terms of variation in surface potential eVS and depletion region w caused by the adsorption of molecular oxygen O2-.

  18. Tritium-doping enhancement of polystyrene by ultraviolet laser and hydrogen plasma irradiation for laser fusion experiments

    Energy Technology Data Exchange (ETDEWEB)

    Iwasa, Yuki, E-mail: iwasa-y@ile.osaka-u.ac.jp [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Yamanoi, Kohei; Iwano, Keisuke; Empizo, Melvin John F.; Arikawa, Yasunobu; Fujioka, Shinsuke; Sarukura, Nobuhiko; Shiraga, Hiroyuki; Takagi, Masaru; Norimatsu, Takayoshi; Azechi, Hiroshi [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Noborio, Kazuyuki; Hara, Masanori; Matsuyama, Masao [Hydrogen Isotope Research Center, Organization for Promotion of Research, University of Toyama, 3190 Gofuku, Toyama 930-8555 (Japan)

    2016-11-15

    Highlights: • Tritium-doped polystyrene films are fabricated by the Wilzbach method with UV laser and hydrogen plasma irradiation. • The 266-nm laser-irradiated, 355-nm laser-irradiated, and hydrogen plasma-irradiated polystyrene films exhibit higher PSL intensities and specific radioactivities than the non-irradiated sample. • Tritium doping by UV laser irradiation can be largely affected by the laser wavelength because of polystyrene’s absorption. • Hydrogen plasma irradiation results to a more uniform doping concentration even at low partial pressure and short irradiation time. • UV laser and plasma irradiations can be utilized to fabricate tritium-doped polystyrene shell targets for future laser fusion experiments. - Abstract: We investigate the tritium-doping enhancement of polystyrene by ultraviolet (UV) laser and hydrogen plasma irradiation. Tritium-doped polystyrene films are fabricated by the Wilzbach method with UV laser and hydrogen plasma. The 266-nm laser-irradiated, 355-nm laser-irradiated, and hydrogen plasma-irradiated polystyrene films exhibit higher PSL intensities and specific radioactivities than the non-irradiated sample. Tritium doping by UV laser irradiation can be largely affected by the laser wavelength because of polystyrene’s absorption. In addition, UV laser irradiation is more localized and concentrated at the spot of laser irradiation, while hydrogen plasma irradiation results to a more uniform doping concentration even at low partial pressure and short irradiation time. Both UV laser and plasma irradiations can nevertheless be utilized to fabricate tritium-doped polystyrene targets for future laser fusion experiments. With a high doping rate and efficiency, a 1% tritium-doped polystyrene shell target having 7.6 × 10{sup 11} Bq g{sup −1} specific radioactivity can be obtained at a short period of time thereby decreasing tritium consumption and safety management costs.

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

    International Nuclear Information System (INIS)

    Chu, Dewei; Masuda, Yoshitake; Ohji, Tatsuki; Kato, Kazumi

    2012-01-01

    CeO 2 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 CeO 2 could be controlled. TEM observation indicated that as-prepared CeO 2 film is composed of nanocrystals with average size of several nanometers, while XPS analysis showed the coexistence of Ce 3+ and Ce 4+ in the film. The photoluminescence properties of CeO 2 films were measured, which showed much higher sensitivity compared to bare substrate. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Highly efficient hydrogen evolution based on Ni3S4@MoS2 hybrids supported on N-doped reduced graphene oxide

    Science.gov (United States)

    Xu, Xiaobing; Zhong, Wei; Wu, Liqian; Sun, Yuan; Wang, Tingting; Wang, Yuanqi; Du, Youwei

    2018-01-01

    Hydrogen evolution reaction (HER) through water splitting at low overpotential is an appealing technology to produce renewable energy, wherein the design of stable electrocatalysts is very critical. To achieve optimal electrochemical performance, a highly efficient and stable noble-metal-free HER catalyst is synthesized by means of a facile hydrothermal co-synthesis. It consists of Ni3S4 nanosheets and MoS2 nanolayers supported on N-doped reduced graphene oxide (Ni3S4/MoS2@N-rGO). The optimized sample provides a large amount of active sites that benefit electron transfer in 3D conductive networks. Thanks to the strong synergistic effect in the catalyst network, we achieved a low overpotential of 94 mV, a small Tafel slope of 56 mV/dec and remarkable durability in an acidic medium.

  1. Hydrogenation of Lactic Acid to 1,2-propanediol over Ru-based catalysts

    NARCIS (Netherlands)

    Liu, K.; Huang, X.; Pidko, E.A.; Hensen, E.J.M.

    2018-01-01

    The catalytic hydrogenation of lactic acid to 1,2-propanediol with supported Ru catalysts in water was investigated. The influence of catalyst support (activated carbon, γ-Al2O3, SiO2, TiO2, and CeO2) and promoters (Pd, Au, Mo, Re, Sn) on the catalytic performance was evaluated. Catalytic tests

  2. Selectivity enhancement of indium-doped SnO2 gas sensors

    International Nuclear Information System (INIS)

    Salehi, A.

    2002-01-01

    Indium doping was used to enhance the selectivity of SnO 2 gas sensor. Both indium-doped and undoped SnO 2 gas sensors fabricated with different deposition techniques were investigated. The changes in the sensitivity of the sensors caused by selective gases (hydrogen and wood smoke) ranging from 500 to 3000 ppm were measured at different temperatures from 50 to 300 deg. C. The sensitivity peaks of the samples exhibit different values for selective gases with a response time of approximately 0.5 s. Thermally evaporated indium-doped SnO 2 gas sensor shows a considerable increase in the sensitivity peak of 27% in response to wood smoke, whereas it shows a sensitivity peak of 7% to hydrogen. This is in contrast to the sputter deposited indium-doped SnO 2 gas sensor, which exhibits a much lower sensitivity peak of approximately 2% to hydrogen and wood smoke compared to undoped SnO 2 gas sensors fabricated by chemical vapor deposition and spray pyrolysis. Scanning electron microscopy shows that different deposition techniques result in different porosity of the films. It is observed that the thermally evaporated indium-doped SnO 2 gas sensor shows high porosity, while the sputtered sample exhibits almost no porosity

  3. Effect of nitrogen doping of graphene oxide on hydrogen and hydroxyl adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Min, Byeong June; Jeong, Hae Kyung [Daegu University, Kyungsan (Korea, Republic of)

    2014-05-15

    We investigate how nitrogen-doping affects the hydrogen (H) and the hydroxyl (OH) adsorption on graphene oxide (GO) and on nitrogen-doped GO (NGO) via pseudopotential plane wave density functional calculations within the local spin density approximation. We find that the nitrogen doping brings about drastic changes in the hydrogen and the hydroxyl adsorption energetics, but its effects depend sensitively on the nitrogen configuration in NGO. The H and the OH adsorption energies are comparable only for pyrrolic NGO. In GO and quarternary NGO, the H adsorption energy is greater than the OH adsorption energy while the trend is reversed in pyridinic NGO. Also, the OH adsorption process is less affected by nitrogen-doping than the H adsorption is.

  4. Methyllithium-Doped Naphthyl-Containing Conjugated Microporous Polymer with Enhanced Hydrogen Storage Performance.

    Science.gov (United States)

    Xu, Dan; Sun, Lei; Li, Gang; Shang, Jin; Yang, Rui-Xia; Deng, Wei-Qiao

    2016-06-01

    Hydrogen storage is a primary challenge for using hydrogen as a fuel. With ideal hydrogen storage kinetics, the weak binding strength of hydrogen to sorbents is the key barrier to obtain decent hydrogen storage performance. Here, we reported the rational synthesis of a methyllithium-doped naphthyl-containing conjugated microporous polymer with exceptional binding strength of hydrogen to the polymer guided by theoretical simulations. Meanwhile, the experimental results showed that isosteric heat can reach up to 8.4 kJ mol(-1) and the methyllithium-doped naphthyl-containing conjugated microporous polymer exhibited an enhanced hydrogen storage performance with 150 % enhancement compared with its counterpart naphthyl-containing conjugated microporous polymer. These results indicate that this strategy provides a direction for design and synthesis of new materials that meet the US Department of Energy (DOE) hydrogen storage target. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Novel nanostructured CeO 2 as efficient catalyst for energy and ...

    Indian Academy of Sciences (India)

    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 ...

  6. The effect of dissolved hydrogen on the dissolution of 233U doped UO2(s) high burn-up spent fuel and MOX fuel

    International Nuclear Information System (INIS)

    Carbol, P.; Spahiu, K.

    2005-03-01

    In this report the results of the experimental work carried out in a large EU-research project (SFS, 2001-2004) on spent fuel stability in the presence of various amounts of near field hydrogen are presented. Studies of the dissolution of 233 U doped UO 2 (s) simulating 'old' spent fuel were carried out as static leaching tests, autoclave tests with various hydrogen concentrations and electrochemical tests. The results of the leaching behaviour of a high burn-up spent fuel pellet in 5 M NaCl solutions in the presence of 3.2 bar H 2 pressure and of MOX fuel in dilute synthetic groundwater under 53 bar H 2 pressure are also presented. In all the experimental studies carried out in this project, a considerable effect of hydrogen in the dissolution rates of radioactive materials was observed. The experimental results obtained in this project with a-doped UO 2 , high burn-up spent fuel and MOX fuel together with literature data give a reliable background to use fractional alteration/dissolution rates for spent fuel of the order of 10 -6 /yr - 10 -8 /yr with a recommended value of 4x10 -7 /yr for dissolved hydrogen concentrations above 10 -3 M and Fe(II) concentrations typical for European repository concepts. Finally, based on a review of the experimental data and available literature data, potential mechanisms of the hydrogen effect are also discussed. The work reported in this document was performed as part of the Project SFS of the European Commission 5th Framework Programme under contract no FIKW-CT-2001-20192 SFS. It represents the deliverable D10 of the experimental work package 'Key experiments using a-doped UO 2 and real spent fuel', coordinated by SKB with the participation of ITU, FZK-INE, ENRESA, CIEMAT, ARMINES-SUBATECH and SKB

  7. Simple Hydrogen Plasma Doping Process of Amorphous Indium Gallium Zinc Oxide-Based Phototransistors for Visible Light Detection.

    Science.gov (United States)

    Kang, Byung Ha; Kim, Won-Gi; Chung, Jusung; Lee, Jin Hyeok; Kim, Hyun Jae

    2018-02-28

    A homojunction-structured amorphous indium gallium zinc oxide (a-IGZO) phototransistor that can detect visible light is reported. The key element of this technology is an absorption layer composed of hydrogen-doped a-IGZO. This absorption layer is fabricated by simple hydrogen plasma doping, and subgap states are induced by increasing the amount of hydrogen impurities. These subgap states, which lead to a higher number of photoexcited carriers and aggravate the instability under negative bias illumination stress, enabled the detection of a wide range of visible light (400-700 nm). The optimal condition of the hydrogen-doped absorption layer (HAL) is fabricated at a hydrogen partial pressure ratio of 2%. As a result, the optimized a-IGZO phototransistor with the HAL exhibits a high photoresponsivity of 1932.6 A/W, a photosensitivity of 3.85 × 10 6 , and a detectivity of 6.93 × 10 11 Jones under 635 nm light illumination.

  8. Hydrogen generation from decomposition of hydrous hydrazine over Ni-Ir/CeO2 catalyst

    Directory of Open Access Journals (Sweden)

    Hongbin Dai

    2017-02-01

    Full Text Available The synthesis of highly active and selective catalysts is the central issue in the development of hydrous hydrazine (N2H4·H2O as a viable hydrogen carrier. Herein, we report the synthesis of bimetallic Ni-Ir nanocatalyts supported on CeO2 using a one-pot coprecipitation method. A combination of XRD, HRTEM and XPS analyses indicate that the Ni-Ir/CeO2 catalyst is composed of tiny Ni-Ir alloy nanoparticles with an average size of around 4 nm and crystalline CeO2 matrix. The Ni-Ir/CeO2 catalyst exhibits high catalytic activity and excellent selectivity towards hydrogen generation from N2H4·H2O at mild temperatures. Furthermore, in contrast to previously reported Ni-Pt catalysts, the Ni-Ir/CeO2 catalyst shows an alleviated requirement on alkali promoter to achieve its optimal catalytic performance.

  9. Bulk modulus of CeO2 and PrO2-An experimental and theoretical study

    International Nuclear Information System (INIS)

    Gerward, L.; Staun Olsen, J.; Petit, L.; Vaitheeswaran, G.; Kanchana, V.; Svane, A.

    2005-01-01

    The high-pressure structural behaviour of CeO 2 and PrO 2 has been investigated by synchrotron X-ray diffraction at pressures up to 20 and 35 GPa, respectively. The experiments are accompanied by first principles calculations using the self-interaction corrected local spin density (SIC-LSD) approximation. The experimental values for the zero-pressure bulk modulus of CeO 2 and PrO 2 are 220(9) and 187(8) GPa, respectively. Our calculations reproduce the lattice constants with good accuracy, but find identical bulk modulii for CeO 2 (176.9 GPa) and PrO 2 (176.8 GPa)

  10. Preparation and characterization of CeO2 highly dispersed on activated carbon

    International Nuclear Information System (INIS)

    Serrano-Ruiz, J.C.; Ramos-Fernandez, E.V.; Silvestre-Albero, J.; Sepulveda-Escribano, A.; Rodriguez-Reinoso, F.

    2008-01-01

    A new material constituted by cerium dioxide highly dispersed on activated carbon (CeO 2 /AC) was prepared by an impregnation method using cerium(III) nitrate as CeO 2 precursor. In order to evaluate the degree of ceria dispersion on the carbon support, CeO 2 /AC was characterized by a number of techniques: thermogravimetry coupled with a mass spectrometer (TG-MS), N 2 adsorption at 77 K, temperature-programmed desorption (TPD), temperature-programmed reduction (TPR) and transmission electron microscopy (TEM). The analysis of the decomposition process under inert atmosphere indicated that cerium nitrate decomposes at 440-460 K, with the evolution of NO. Furthermore, this process produces an additional oxidation of the carbon surface (with evolution of N 2 O) and the subsequent onset of new oxygen surface groups, detected by means of temperature-programmed desorption. The ceria deposition process takes place with a decrease in the N 2 adsorption capacity of the starting carbon support, and the analysis of the pore size distribution showed that the majority of ceria particles are situated at the most internal part of the carbon porosity. The temperature-programmed reduction profile of CeO 2 /AC was very different to that shown by unsupported CeO 2 , with only one continuous reduction process at low temperatures (800-900 K). Finally, TEM pictures gave direct evidence that ceria is highly dispersed on the carbon surface, with a narrow CeO 2 particle distribution centred around 3 nm

  11. Formation of qualified BaHfO3 doped Y0.5Gd0.5Ba2Cu3O7-δ film on CeO2 buffered IBAD-MgO tape by self-seeding pulsed laser deposition

    Science.gov (United States)

    Liu, Linfei; Wang, Wei; Yao, Yanjie; Wu, Xiang; Lu, Saidan; Li, Yijie

    2018-05-01

    Improvement in the in-filed transport properties of REBa2Cu3O7-δ (RE = rare earth elements, REBCO) coated conductor is needed to meet the performance requirements for various practical applications, which can be accomplished by introducing artificial pinning centers (APCs), such as second phase dopant. However, with increasing dopant level the critical current density Jc at 77 K in zero applied magnetic field decreases. In this paper, in order to improve Jc we propose a seed layer technique. 5 mol% BaHfO3 (BHO) doped Y0.5Gd0.5Ba2Cu3O7-δ (YGBCO) epilayer with an inserted seed layer was grown on CeO2 buffered ion beam assisted deposition MgO (IBAD-MgO) tape by pulsed laser deposition. The effect of the conditions employed to prepare the seed layer, including tape moving speed and chemical composition, on the quality of 5 mol% BHO doped YGBCO epilayer was systematically investigated by X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) observations. It was found that all the samples with seed layer have higher Jc (77 K, self-field) than the 5 mol% BHO doped YGBCO film without seed layer. The seed layer could inhibit deterioration of the Jc at 77 K and self-filed. Especially, the self-seed layer (5 mol% BHO doped YGBCO seed layer) was more effective in improving the crystal quality, surface morphology and superconducting performance. At 4.2 K, the 5 mol% BHO doped YGBCO film with 4 nm thick self-seed layer had a very high flux pinning force density Fp of 860 GN/m3 for B//c under a 9 T field, and more importantly, the peak of the Fp curve was not observed.

  12. A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays.

    Science.gov (United States)

    Liao, Yulong; Yuan, Botao; Zhang, Dainan; Wang, Xiaoyi; Li, Yuanxun; Wen, Qiye; Zhang, Huaiwu; Zhong, Zhiyong

    2018-04-03

    In this paper, a facile method was proposed to load CeO 2 nanoparticles (NPs) on anodic TiO 2 nanotube (NT) arrays, which leads to a formation of CeO 2 /TiO 2 heterojunctions. Highly ordered anatase phase TiO 2 NT arrays were fabricated by using anodic oxidation method, then these individual TiO 2 NTs were used as tiny "nano-containers" to load a small amount of Ce(NO 3 ) 3 solutions. The loaded anodic TiO 2 NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO 3 ) 3 would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO 3 ) 3 , cubic crystal CeO 2 NPs were obtained and successfully loaded into the anodic TiO 2 NT arrays. The prepared CeO 2 /TiO 2 heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO 2 /TiO 2 films, which could be very useful for environmental and energy-related areas.

  13. Molecular adsorption of hydrogen peroxide on N- and Fe-doped titania nanoclusters

    Energy Technology Data Exchange (ETDEWEB)

    Mohajeri, Afshan, E-mail: amohajeri@shirazu.ac.ir; Dashti, Nasimeh Lari

    2017-06-15

    Highlights: • The stability and electronic properties of N/Fe-doped (TiO{sub 2}){sub n} clusters with n = 5,6 were studied. • The adsorption H{sub 2}O{sub 2} on the surface of doped clusters has been investigated. • This is the first report of H{sub 2}O{sub 2} adsorption onto the (TiO{sub 2}){sub n} cluster in the presence of metal and non-metal dopants. • The effect of N and Fe dopants on interaction strength was studied. - Abstract: Titanium dioxide (titania) nanoparticles have been extensively investigated for photocatalytic applications such as the decomposition and adsorption of pollutant and undesirable compound in air and waste water. In this context, the present article reports the molecular adsorption of hydrogen peroxide on the surface of doped titania clusters. Density functional theory calculations were performed to investigate the structures and electronic properties of two nanoscale (TiO{sub 2}){sub n} clusters (n = 5,6) modified by nitrogen and iron dopants. The relative stability of all possible N-doped and Fe-doped isomers has been compared with each other and with the parent cluster. It was found that the Fe-doped clusters are in general more stable than the N-doped counterparts. Moreover, after N/Fe doping an enhanced in the magnetization of the clusters is observed. In the second part, we have investigated different modes of H{sub 2}O{sub 2} adsorption on the lowest-energy isomers of doped clusters. In almost all the cases, the adsorptions on the doped clusters are found to be less exothermic than on the corresponding undoped parent cluster. Our results highlight the essential role of charge transfer into the interaction between H{sub 2}O{sub 2} and doped (TiO{sub 2}){sub n} clusters, especially for Fe-doped clusters.

  14. Structure and properties of PbO2-CeO2 anodes on stainless steel

    International Nuclear Information System (INIS)

    Song, Yuehai; Wei, Gang; Xiong, Rongchun

    2007-01-01

    The lack of ideal anodes with excellent activity and stability is one of the critical problems in electrochemical oxidation for organic wastewater treatment. It is reported in this paper that the PbO 2 -CeO 2 films electrodeposited on stainless steel were used as catalytic electrodes for treating antibiotic wastewater. The PbO 2 -CeO 2 films on stainless steel were proved to be high stability, good activity and relatively low cost. Because of these properties, the films are more attractive than any other electrocatalytic materials among conventional dimensionally stable anodes (DSA). Experimental results showed that the PbO 2 -CeO 2 electrode has a service life of 1100 h in 3 M H 2 SO 4 solution under a current density of 1 A cm -2 at 35 o C, compared with 300 h for PbO 2 under the same conditions. The X-ray diffraction (XRD) patterns and SEM images indicated that the PbO 2 -CeO 2 films on stainless steel have a dense structure and the preferred crystalline orientation on the substrate surface was changed. Color and chemical oxygen demand (COD) of antibiotics wastewater were studied by electrolysis by using these electrodes as anode and stainless steel as cathode. The results indicated that the anodes have excellent activity in antibiotic wastewater treatment. The PbO 2 -CeO 2 electrodes have high chemical stability which contributed by the superstable nature of the electrode, dense microstructure, good conductivity and the improvement of bonding with the stainless steel during electrodeposition

  15. Sulfur-doped graphene via thermal exfoliation of graphite oxide in H2S, SO2, or CS2 gas.

    Science.gov (United States)

    Poh, Hwee Ling; Šimek, Petr; Sofer, Zdeněk; Pumera, Martin

    2013-06-25

    Doping of graphene with heteroatoms is an effective way to tailor its properties. Here we describe a simple and scalable method of doping graphene lattice with sulfur atoms during the thermal exfoliation process of graphite oxides. The graphite oxides were first prepared by Staudenmaier, Hofmann, and Hummers methods followed by treatments in hydrogen sulfide, sulfur dioxide, or carbon disulfide. The doped materials were characterized by scanning electron microscopy, high-resolution X-ray photoelectron spectroscopy, combustible elemental analysis, and Raman spectroscopy. The ζ-potential and conductivity of sulfur-doped graphenes were also investigated in this paper. It was found that the level of doping is more dramatically influenced by the type of graphite oxide used rather than the type of sulfur-containing gas used during exfoliation. Resulting sulfur-doped graphenes act as metal-free electrocatalysts for an oxygen reduction reaction.

  16. Internal friction and Young's modulus measurements in Zr-2.5Nb alloy doped with hydrogen

    International Nuclear Information System (INIS)

    Ritchie, I.G.; Pan, Z.-L.

    1992-01-01

    The presence of hydrides is an important factor in assessing the potential for delayed hydride cracking in Zr-2.5Nb alloys, and consequently, the terminal solid solubility (TSS) of hydrogen in the material is an important parameter. In pure zirconium doped with hydrogen, the TSS is marked by a dissolution peak of internal friction on heating and a truncated precipitation peak associated with hydride nucleation on cooling. These phenomena occur only at low frequencies and are accompanied in torsion pendulum studies by autotwisting of the sample (or zero-point drift) that stops abruptly at the TSS. Neither the dissolution/precipitation peaks nor the autotwisting phenomena are observed in Zr-2.5Nb. However, the TSS is also marked by an abrupt change in the slope of Young's modulus as a function of temperature. This phenomenon is observed regardless of the frequency (in the range 1 Hz to 120 kHz) and in both pure zirconium and Zr-2.5Nb alloys. The reasons for the absence of the dissolution/precipitation peak in Zr-2.5Nb alloys are discussed and the use of Young's modulus changes to investigate the TSS of hydrogen and the hysteresis between heat-up and cool-down TSS curves is demonstrated. (author)

  17. Structural analysis of CuO / CeO2-based catalytic materials intended for PROX reaction: Part I

    International Nuclear Information System (INIS)

    Neiva, L.S.; Simoes, A.N.; Bispo, A.; Ribeiro, M.A.; Gama, L.

    2011-01-01

    This work relates the synthesis process of CuO/CeO 2 catalytic materials by a combustion reaction method as well as it introduces a structural analysis of the developed material, this structural analysis had as main focus to evaluate the influence of the doping substance (CuO) when being incorporated in the hostess matrix structure that is CeO 2 . The CuO/CeO catalytic materials developed in this work are destined to preferential oxidation of CO reaction (PROX). The developed materials were characterized by XRD, SEM and textural complete analysis by the BET method. According to the results, the CuO incorporation changed crystallinity of the structure of the catalytic materials. On the other hand, the morphologic and textural characteristics did not showed significant differences regarding the presence of the doping substance (CuO) in the structure of the developed materials. The porosity of the structures of the developed catalytic materials belongs to the type macroporous. (author)

  18. A high resolution EELS study of free-carrier variations in H2+/H+ bombarded (100)GaAs

    International Nuclear Information System (INIS)

    Dubois, L.H.; Schwartz, G.P.

    1984-01-01

    High resolution electron energy loss spectroscopy (EELS) has been used to examine whether thermal recovery of the near-surface free-carrier concentration in Te-doped (100) GaAs is accomplished following low energy (250--1500 eV) hydrogen ion bombardment. For hydrogen ion impact energies below 500 eV, the nominal bulk free-carrier density is recovered by annealing at 725 K for 2 h. For comparable ion doses, the net free-carrier concentration decreases monotonically at higher impact energies under similar annealing conditions. The threshold for damage retention occurs close to the value of transmitted energy which is necessary to create either a Ga or an As interstitial point defect

  19. F-centre luminescence in nanocrystalline CeO2

    International Nuclear Information System (INIS)

    Aškrabić, S; Dohčević-Mitrović, Z D; Araújo, V D; Ionita, G; De Lima, M M Jr; Cantarero, A

    2013-01-01

    Nanocrystalline CeO 2 powders were synthesized by two cost-effective methods: the self-propagating room temperature (SPRT) method and the precipitation method. Differently prepared samples exhibited different temperature-dependent photoluminescence (PL) in the ultraviolet and visible regions. The PL signals originated from different kinds of oxygen-deficient defect centres with or without trapped electrons (F 0 , F + or F ++ centres). The temperature-dependent PL spectra were measured using different excitation lines, below (457, 488 and 514 nm) or comparable (325 nm) to the ceria optical band gap energy, in order to investigate the positions of intragap localized defect states. Evidence for the presence of F + centres was supported by the signals observed in electron paramagnetic resonance (EPR) measurements. Based on PL and EPR measurements it was shown that F + centres dominate in the CeO 2 sample synthesized by the SPRT method, whereas F 0 centres are the major defects in the CeO 2 sample synthesized by the precipitation method. The luminescence from F ++ states, as shallow trap states, was registered in both samples. Energy level positions of these defect states in the ceria band gap were proposed. (paper)

  20. F-centre luminescence in nanocrystalline CeO2

    Science.gov (United States)

    Aškrabić, S.; Dohčević-Mitrović, Z. D.; Araújo, V. D.; Ionita, G.; de Lima, M. M., Jr.; Cantarero, A.

    2013-12-01

    Nanocrystalline CeO2 powders were synthesized by two cost-effective methods: the self-propagating room temperature (SPRT) method and the precipitation method. Differently prepared samples exhibited different temperature-dependent photoluminescence (PL) in the ultraviolet and visible regions. The PL signals originated from different kinds of oxygen-deficient defect centres with or without trapped electrons (F0, F+ or F++ centres). The temperature-dependent PL spectra were measured using different excitation lines, below (457, 488 and 514 nm) or comparable (325 nm) to the ceria optical band gap energy, in order to investigate the positions of intragap localized defect states. Evidence for the presence of F+ centres was supported by the signals observed in electron paramagnetic resonance (EPR) measurements. Based on PL and EPR measurements it was shown that F+ centres dominate in the CeO2 sample synthesized by the SPRT method, whereas F0 centres are the major defects in the CeO2 sample synthesized by the precipitation method. The luminescence from F++ states, as shallow trap states, was registered in both samples. Energy level positions of these defect states in the ceria band gap were proposed.

  1. Evaluation of candidate Stirling engine heater tube alloys after 3500 hours exposure to high pressure doped hydrogen or helium

    Science.gov (United States)

    Misencik, J. A.; Titran, R. H.

    1984-01-01

    The heater head tubes of current prototype automotive Stirling engines are fabricated from alloy N-155, an alloy which contains 20 percent cobalt. Because the United States imports over 90 percent of the cobalt used in this country and resource supplies could not meet the demand imposed by automotive applications of cobalt in the heater head (tubes plus cylinders and regenerator housings), it is imperative that substitute alloys free of cobalt be identified. The research described herein focused on the heater head tubes. Sixteen alloys (15 potential substitutes plus the 20 percent Co N-155 alloy) were evaluated in the form of thin wall tubing in the NASA Lewis Research Center Stirling simulator materials diesel fuel fired test rigs. Tubes filled with either hydrogen doped with 1 percent CO2 or with helium at a gas pressure of 15 MPa and a temperature of 820 C were cyclic endurance tested for times up to 3500 hr. Results showed that two iron-nickel base superalloys, CG-27 and Pyromet 901 survived the 3500 hr endurance test. The remaining alloys failed by creep-rupture at times less than 3000 hr, however, several other alloys had superior lives to N-155. Results further showed that doping the hydrogen working fluid with 1 vol % CO2 is an effective means of reducing hydrogen permeability through all the alloy tubes investigated.

  2. Polarity driven morphology of CeO2(1 0 0) islands on Cu(1 1 1)

    International Nuclear Information System (INIS)

    Stetsovych, O.; Beran, J.; Dvořák, F.; Mašek, K.; Mysliveček, J.; Matolín, V.

    2013-01-01

    Thin ceria films supported by metal substrates represent important model systems for reactivity studies in heterogeneous catalysis. Here we report the growth study of the polar CeO 2 (1 0 0) phase as part of a mixed CeO 2 (1 1 1)–CeO 2 (1 0 0) thin film supported by Cu(1 1 1). The two ceria phases grow on different areas of the substrate, what allows a reliable growth characterization of the CeO 2 (1 0 0) islands on Cu(1 1 1). Scanning tunneling microscopy measurements reveal CeO 2 (1 0 0) to grow in the form of highly dispersed three dimensional (3D) islands on a CeO 2 (1 0 0) interfacial layer. The CeO 2 (1 0 0) islands exhibit a 2 × 2 surface reconstruction. The presence of the surface reconstruction together with the highly dispersed growth of CeO 2 (1 0 0) islands corresponds to the requirement for compensation of the surface dipole moment on the CeO 2 (1 0 0). CeO 2 (1 0 0) islands are further characterized by reflection high energy electron diffraction yielding their epitaxial relations with respect to the Cu(1 1 1) substrate. The growth of well characterized CeO 2 (1 0 0) islands supported by Cu(1 1 1) represents a starting point for developing a novel template for structure-related reactivity studies of ceria based model catalysts.

  3. Hydrogen storage in pure and Li-doped carbon nanopores: combined effects of concavity and doping.

    Science.gov (United States)

    Cabria, I; López, M J; Alonso, J A

    2008-04-14

    Density functional calculations are reported for the adsorption of molecular hydrogen on carbon nanopores. Two models for the pores have been considered: (i) The inner walls of (7,7) carbon nanotubes and (ii) the highly curved inner surface of nanotubes capped on one end. The effect of Li doping is investigated in all cases. The hydrogen physisorption energies increase due to the concavity effect inside the clean nanotubes and on the bottom of the capped nanotubes. Li doping also enhances the physisorption energies. The sum of those two effects leads to an increase by a factor of almost 3 with respect to the physisorption in the outer wall of undoped nanotubes and in flat graphene. Application of a quantum-thermodynamical model to clean cylindrical pores of diameter 9.5 A, the diameter of the (7,7) tube, indicates that cylindrical pores of this size can store enough hydrogen to reach the volumetric and gravimetric goals of the Department of Energy at 77 K and low pressures, although not at 300 K. The results are useful to explain the experiments on porous carbons. Optimizations of the pore size, concavity, and doping appear as promising alternatives for achieving the goals at room temperature.

  4. Interaction of Pd single atoms with different CeO2 crystal planes: A first-principles study

    Science.gov (United States)

    He, Bingling; Wang, Jinlong; Ma, Dongwei; Tian, Zhixue; Jiang, Lijuan; Xu, Yan; Cheng, Sujun

    2018-03-01

    The adsorption of single Pd atoms on the various CeO2 surfaces, including (111), (110), and (100), has been studied based on the first-principles calculations. It is found that, according to the calculated adsorption energy, interaction strength between Pd and the three CeO2 surfaces follows the order of (100) > (110) > (111). Interestingly, the effect of the electron localization on the surface Ce ions due to the Pd adsorption on its adsorption stability is more significant for the (110) surface than that for the (111) and (100) surfaces. We also find that the formal oxidation states of Pd0, Pdδ+ (δ < 1) and Pd1+ may appear on the CeO2 (111) surface, and Pdδ+ (δ < 1) and Pd1+ could coexist on the CeO2 (100) surfaces. However, under suitable conditions the CeO2 (110) surface may be covered with Pd2+ ions. Present theoretical results clearly suggest that the interaction between Pd and CeO2 nanocrystals significantly depends on the crystal planes of CeO2. It is expected that our study will give useful insights into the effect of CeO2 crystal plane on the physicochemical and catalytic properties of CeO2 supported Pd catalyst.

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

    International Nuclear Information System (INIS)

    Coll, M; Gazquez, J; Sandiumenge, F; Pomar, A; Puig, T; Obradors, X; Espinos, J P; Gonzalez-Elipe, A R

    2006-01-01

    CeO 2 films are technologically important as a buffer layer for the integration of superconducting YBa 2 Cu 3 O 7 films on biaxially textured Ni substrates. The growth of YBa 2 Cu 3 O 7 layers on the CeO 2 cap layers by the trifluoroacetate (TFA) route remains a critical issue. To improve the accommodation of YBa 2 Cu 3 O 7 on CeO 2 , surface conditioning or CeO 2 is required. In this work we have applied ex-situ post-processes at different atmospheres to the CeO 2 layers deposited on YSZ single crystals using rf sputtering. XPS analysis showed that post-annealing CeO 2 layer in Ar/H 2 /H 2 O catalyses in an unexpected way the growth of (001)- terraces. We also report on the growth conditions of YBa 2 Cu 3 O 7 -TFA on CeO 2 buffered YSZ single crystal grown by chemical solution deposition and we compare them with those leading to optimized YBa 2 Cu 3 O 7 -TFA films on LaAlO 3 single crystals. Critical currents up to 1.6 MA/cm 2 at 77 K have been demonstrated in 300 nm thick YBa 2 Cu 3 O 7 layers on CeO 2 /YSZ system. The optimized processing conditions have then been applied to grow YBa 2 Cu 3 O 7 -TFA films on Ni substrates having vacuum deposited cap layers of CeO 2

  6. Catalytic hydrolysis of COS over CeO_2 (110) surface: A density functional theory study

    International Nuclear Information System (INIS)

    Song, Xin; Ning, Ping; Wang, Chi; Li, Kai; Tang, Lihong; Sun, Xin

    2017-01-01

    Graphical abstract: CeO_2 decreases the maximum energy barrier by 76.15 kcal/mol. H_2O plays a role as a bridge in the process of joint adsorption. Catalytic effect of CeO_2 in the hydrolysis of COS is mainly reflected on the C−O channel. - Highlights: • H_2O is easier adsorbed on the CeO_2 (110) surface than COS. • When COS and H_2O jointly adsorb on the CeO_2 (110) surface, the H_2O molecule plays a role as a bridge. • Ce−O−H bond can enhance the adsorption effect. • Catalytic effect of CeO_2 in the hydrolysis of COS is mainly reflected on the C−O channel. - Abstract: Density functional theory (DFT) calculations were performed to investigate the reaction pathways for catalytic hydrolysis of COS over CeO_2 (110) surface using Dmol"3 model. The thermodynamic stability analysis for the suggested routes of COS hydrolysis to CO_2 and H_2S was evaluated. The absolute values of adsorption energy of H_2O-CeO_2 are higher than that of COS-CeO_2. Meanwhile, the adsorption energy and geometries show that H_2O is easier adsorbed on the surface of CeO_2 (110) than COS. H_2O plays a role as a bridge in the process of joint adsorption. H_2O forms more Ce−O−H groups on the CeO_2 (110) surface. CeO_2 decreases the maximum energy barrier by 76.15 kcal/mol. The migration of H from H_2O to COS is the key for the hydrolysis reaction. C−O channel is easier to occur than C−S channel. Experimental result shows that adding of CeO_2 can increase COS removal rate and prolong the 100% COS removal rate from 180 min to 210 min. The difference between Fe_2O_3 and CeO_2 for the hydrolysis of COS is characterized in the atomic charge transfer and the formation of H−O bond and H−S bond. The transfer effect of H in H_2O to S in COS over CeO_2 decreases the energy barriers of hydrolysis reaction, and enhances the reaction activity of COS hydrolysis.

  7. Eu{sup 2+}-doped OH{sup −} free calcium aluminosilicate glass: A phosphor for smart lighting

    Energy Technology Data Exchange (ETDEWEB)

    Lima, S.M., E-mail: smlima@uems.br [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul, C. P. 351, CEP 79804-970 Dourados, MS (Brazil); Andrade, L.H.C.; Rocha, A.C.P. [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul, C. P. 351, CEP 79804-970 Dourados, MS (Brazil); Silva, J.R.; Farias, A.M.; Medina, A.N.; Baesso, M.L. [Departamento de Física, Universidade Estadual de Maringá, Av. Colombo 5790, 87020-900 Maringá, PR (Brazil); Nunes, L.A.O. [Instituto de Física de São Carlos, Universidade de São Paulo, 13560-970 São Carlos, SP (Brazil); Guyot, Y.; Boulon, G. [Laboratoire de Physico-Chimie des Matériaux Luminescents, Université de Lyon 1, UMR 5620 CNRS, 69622 Villeurbanne (France)

    2013-11-15

    In this paper, a broad emission band from Eu{sup 2+}-doped OH{sup −} free calcium aluminosilicate glass is reported. By changing the excitation wavelengths, the results showed it is possible to tune the emission from green to orange, what combined with the scattered light from the same blue LED used for excitation, provided a color rendering index of 71 and a correlated color temperature of 6550 K. Our preliminary tests indicate this material as a promising phosphor towards the development of smart lighting devices. -- Highlights: • We report a broad emission band from Eu{sup 2+}-doped OH{sup −} free calcium aluminosilicate glass. • The maximum emission peak can be tune from green to orange region. • The test with a LED provided a color rendering index of 71 and a correlated color temperature of 6550 K.

  8. Morphology, structure and optical properties of hydrothermally synthesized CeO2/CdS nanocomposites

    Science.gov (United States)

    Mohanty, Biswajyoti; Nayak, J.

    2018-04-01

    CeO2/CdS nanocomposites were synthesized using a two-step hydrothermal technique. The effects of precursor concentration on the optical and structural properties of the CeO2/CdS nanoparticles were systematically studied. The morphology, composition and the structure of the CeO2/CdS nanocomposite powder were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectrum analysis (EDXA) and X-ray diffraction (XRD), respectively. The optical properties of CeO2/CdS nanocomposites were studied by UV-vis absorption and photoluminescence (PL) spectroscopy. The optical band gaps of the CeO2/CdS nanopowders ranged from 2.34 eV to 2.39 eV as estimated from the UV-vis absorption. In the room temperature photoluminescence spectrum of CeO2/CdS nanopowder, a strong blue emission band was observed at 400 nm. Since the powder shows strong visible luminescence, it may be used as a blue phosphor in future. The original article published with this DOI was submitted in error. The correct article was inadvertently left out of the original submission. This has been rectified and the correct article was published online on 16 April 2018.

  9. Vertically aligned nitrogen doped (Sn,Nb)O_2 nanotubes – Robust photoanodes for hydrogen generation by photoelectrochemical water splitting

    International Nuclear Information System (INIS)

    Patel, Prasad Prakash; Hanumantha, Prashanth Jampani; Velikokhatnyi, Oleg I.; Datta, Moni Kanchan; Gattu, Bharat; Poston, James A.; Manivannan, Ayyakkannu; Kumta, Prashant N.

    2016-01-01

    Graphical abstract: - Highlights: • Nb and N co-doping provides excellent optoelectronic properties for SnO_2 NTs. • The optoelectronic properties of doped SnO_2 are studied by first principles study. • (Sn_0_._9_5Nb_0_._0_5)O_2:N-600 NTs exhibits superior ABPE (4.1%) to date. • Excellent photoelectrochemical stability of (Sn_0_._9_5Nb_0_._0_5)O_2:N-600 NTs. - Abstract: Hydrogen generation from photoelectrochemical (PEC) water splitting is on the forefront of clean energy generation landscape. The efficiency of PEC system is dependent on the engineering of semiconductors with tailored narrow band gap coupled with superior photoelectrochemical activity and desired stability vital for the commercialization of PEC water splitting cells. We report herein the study of vertically aligned Nb and N doped SnO_2 nanotubes (NTs), i.e., (Sn_0_._9_5Nb_0_._0_5)O_2:N NTs for PEC water splitting. (Sn_0_._9_5Nb_0_._0_5)O_2 NTs was selected for co-doping with nitrogen by systematic analysis of applied bias photon-to-current efficiency of various Nb doped SnO_2 (x = 0–0.1) compositions. Consequently, excellent photoelectrochemical stability and the highest efficiency of 4.1% is obtained for (Sn_0_._9_5Nb_0_._0_5)O_2:N-600 NTs never observed for other known TiO_2, ZnO, and Fe_2O_3 systems to date. Additionally, theoretical first principles study provides understanding of Nb and N co-doping on the electronic structure and band gap of SnO_2 semiconductor, further corroborating results of the experimental study.

  10. A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions

    Science.gov (United States)

    Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

    2015-08-01

    A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique

  11. Influence of hydrogen impurities on p-type resistivity in Mg-doped GaN films

    International Nuclear Information System (INIS)

    Yang, Jing; Zhao, Degang; Jiang, Desheng; Chen, Ping; Zhu, Jianjun; Liu, Zongshun; Le, Lingcong; He, Xiaoguang; Li, Xiaojing; Zhang, Y. T.; Du, G. T.

    2015-01-01

    The effects of hydrogen impurities on p-type resistivity in Mg-doped GaN films were investigated. It was found that hydrogen impurities may have the dual role of passivating Mg Ga acceptors and passivating donor defects. A decrease in p-type resistivity when O 2 is introduced during the postannealing process is attributed to the fact that annealing in an O 2 -containing environment can enhance the dissociation of Mg Ga -H complexes as well as the outdiffusion of H atoms from p-GaN films. However, low H concentrations are not necessarily beneficial in Mg-doped GaN films, as H atoms may also be bound at donor species and passivate them, leading to the positive effect of reduced compensation

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

    International Nuclear Information System (INIS)

    Andrade Nono, M.C. de.

    1990-12-01

    This work presents the development and the characterization of CeO 2 -stabilized tetragonal ZrO 2 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 CeO 2 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)

  13. Characterization and synergetic antibacterial properties of ZnO and CeO2 supported by halloysite

    Science.gov (United States)

    Shu, Zhan; Zhang, Yi; Ouyang, Jing; Yang, Huaming

    2017-10-01

    A novel antibacterial nanocomposite, CeO2-ZnO/HNTs was prepared by a homogeneous co-precipitation method in ethanol solution. ZnO and CeO2 nanoparticles with sizes of approximately 8 and 4 nm, respectively, were dispersively precipitated onto the surface of halloysite nanotubes (HNTs). HNTs served as a template for reducing the agglomeration of ZnO nanoparticles and improving the interface reactions between the nanocomposite and bacteria cells. CeO2 nanoparticles were introduced to suppress the recombination of electron-hole pairs, and narrow the energy gap of ZnO nanoparticles. The synergistic effects of ZnO, CeO2 nanoparticles and HNTs led to the superior antibacterial activity of the CeO2-ZnO/HNTs nanocomposite against gram-negative Escherichia coli.

  14. Irradiation effects in UO2 and CeO2

    International Nuclear Information System (INIS)

    Ye, Bei; Oaks, Aaron; Kirk, Mark; Yun, Di; Chen, Wei-Ying; Holtzman, Benjamin; Stubbins, James F.

    2013-01-01

    Single crystal CeO 2 , as a surrogate material to UO 2 , was irradiated with 500 keV xenon ions at 800 °C while being observed using in situ transmission electron microscopy (TEM). Experimental results show the formation and growth of defect clusters including dislocation loops and cavities as a function of increasing atomic displacement dose. At high dose, the dislocation loop structure evolves into an extended dislocation line structure, which appears to remain stable to the high dose levels examined in this study. A high concentration of cavities was also present in the microstructure. Despite high atomic displacement doses, the specimen remained crystalline to a cumulated dose of 5 × 10 15 ions/cm 2 , which is consistent with the known stability of the fluorite structure under high dose irradiation. Kinetic Monte Carlo calculations show that oxygen mobility is substantially higher in hypo-stoichiometric UO 2 /CeO 2 than hyper-stoichiometric systems. This result is consistent with the ability of irradiation damage to recover even at intermediate irradiation temperatures

  15. Hydrogen storage in N- and B-doped graphene decorated by small platinum clusters: A computational study

    Science.gov (United States)

    Chen, I.-Nan; Wu, Shiuan-Yau; Chen, Hsin-Tsung

    2018-05-01

    In this work, we perform density functional theory (DFT) calculations to investigate the hydrogen adsorption on Pt4 cluster supported on pristine, B-, and N-doped graphene sheets. It is found that the doping B or N atom in the graphene could enhance the interaction between the Pt4 cluster and the supporting substrate. The first H2 molecule is found to be dissociative chemisorption on the three substrates. Further, dissociative and molecular adsorption of multiple H2 molecules are co-adsorbed on the three substrates. In addition, the interaction between Pt4(H2)x and the substrate is illustrated for the stability of Pt4(H2)x on the substrate. AIMD simulation is also performed to verify the stability and hydrogen storage. Accordingly, the B-graphene is predicted to be the most potential materials for hydrogen storage among these three materials.

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

    Science.gov (United States)

    Zhang, Shi Hong; Li, Ming Xi; Yoon, Jae Hong; Cho, Tong Yul; Zhu He, Yi; Lee, Chan Gyu

    2008-07-01

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

    Directory of Open Access Journals (Sweden)

    Shi Hong Zhang et al

    2008-01-01

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

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

    International Nuclear Information System (INIS)

    Contreras-García, M.E.; García-Benjume, M. Lorena; Macías-Andrés, Víctor I.; Barajas-Ledesma, E.; Medina-Flores, A.; Espitia-Cabrera, M.I.

    2014-01-01

    Graphical abstract: - Highlights: • Nanostructured TiO 2 -CeO 2 films are successfully synthesized by combining of sputtering and electrophoresis methods. • Synergic effect of CeO 2 on TiO 2 band gap was demonstrated, CeO 2 diminishes it from 3.125 to 2.74. • Morphologic characterization of the nanoconjugate TiO 2 -CeO 2 films by different microscopy techniques. - Abstract: The TiO 2 -CeO 2 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 TiO 2 -CeO 2 gel on sputtered Ti Corning glass substrates. The synergic effect of CeO 2 in TiO 2 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 TiO 2 and CeO 2 nanoparticles in the anatase and fluorite type phases, respectively

  19. Cyclic etching of tin-doped indium oxide using hydrogen-induced modified layer

    Science.gov (United States)

    Hirata, Akiko; Fukasawa, Masanaga; Nagahata, Kazunori; Li, Hu; Karahashi, Kazuhiro; Hamaguchi, Satoshi; Tatsumi, Tetsuya

    2018-06-01

    The rate of etching of tin-doped indium oxide (ITO) and the effects of a hydrogen-induced modified layer on cyclic, multistep thin-layer etching were investigated. It was found that ITO cyclic etching is possible by precisely controlling the hydrogen-induced modified layer. Highly selective etching of ITO/SiO2 was also investigated, and it was suggested that cyclic etching by selective surface adsorption of Si can precisely control the etch rates of ITO and SiO2, resulting in an almost infinite selectivity for ITO over SiO2 and in improved profile controllability.

  20. Optical and structural properties of nanostructured CeO2:Tb3+ film

    International Nuclear Information System (INIS)

    Ansari, Anees A.; Singh, S.P.; Malhotra, B.D.

    2011-01-01

    Nanostructured CeO 2 :Tb 3+ film has been fabricated on glass substrate through sol-gel technique via dip-coating process. (NH 4 ) 2 Ce(NO 3 ) 6 , Tb(NO 3 ) 3 .6H 2 O, ethylene glycol have been used as precursors for sol preparation. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV/VIS and photoluminescence (PL) spectral studies have been employed to analyze the structural and optical properties of the film. XRD pattern has been used to analyze the crystallite nature and calculated particle size by Scherrer equation of nanostructured CeO 2 :Tb 3+ film, found in the range 3-4 nm. SEM image has been observed to analyze the surface topography of the film which is well porous, highly agglomerated and uniformly distributed nanoparticles on the film surface. Optical band gap of nanostructured CeO 2 :Tb 3+ film has been estimated as 3.57 eV. A significant enhancement in band shape of CeO 2 :Tb 3+ spectrum has been observed in PL spectra, showed their promising usages as optical materials in optoelectronic devices.

  1. Some aspects of hydrogen plasma treatment of anti-modulation doped near surface GaAs/AlGaAs single quantum well structures

    International Nuclear Information System (INIS)

    Bumai, Yu.A.; Gobsch, G.; Goldhahn, R.; Stein, N.; Golombek, A.; Nakov, V.; Cheng, T.S.

    1999-01-01

    The MBE grown anti-modulation doped GaAs/AlGaAs structures with near surface single quantum wells were exposed to a DC hydrogen plasma (∼400 eV) and investigated using PL, PLE and PR spectroscopy at 5 K. Strong acceptor related free to bound transition (FB) dominates for quantum well related PL but excitonic features are still observed in PLE spectra. After hydrogen plasma treatment the PL intensity of FB transition from quantum well was strongly increased for above AlGaAs band gap excitation and was unchanged for below AlGaAs one. These results are consistent with atomic hydrogen passivation of deep defects in AlGaAs barriers. At the same time radiative excitonic recombination was quenched by hydrogenation. PLE and PR spectra indicate on a strong increase of electric field in subsurface region of the structure after hydrogenation. The increase of electric field in anti-modulation doped structure after hydrogen plasma treatment is supposed to be due to passivation by atomic hydrogen of surface states that leads to unpinning of Fermi level from mid gap to carbon acceptor level position in GaAs cap layer. It causes the further band bending and surface electric field increase that strongly suppress excitonic recombination in near surface quantum wells

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

    Directory of Open Access Journals (Sweden)

    Berton Marcos A.C.

    2001-01-01

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

  3. Continuous hydrogenation of ethyl levulinate to γ-valerolactone and 2-methyl tetrahydrofuran over alumina doped Cu/SiO2 catalyst: the potential of commercialization

    Science.gov (United States)

    Zheng, Junlin; Zhu, Junhua; Xu, Xuan; Wang, Wanmin; Li, Jiwen; Zhao, Yan; Tang, Kangjian; Song, Qi; Qi, Xiaolan; Kong, Dejin; Tang, Yi

    2016-01-01

    Hydrogenation of levulinic acid (LA) and its esters to produce γ-valerolactone (GVL) and 2-methyl tetrahydrofuran (2-MTHF) is a key step for the utilization of cellulose derived LA. Aiming to develop a commercially feasible base metal catalyst for the production of GVL from LA, with satisfactory activity, selectivity, and stability, Al2O3 doped Cu/SiO2 and Cu/SiO2 catalysts were fabricated by co-precipitation routes in parallel. The diverse physio-chemical properties of these two catalysts were characterized by XRD, TEM, dissociative N2O chemisorptions, and Py-IR methods. The catalytic properties of these two catalysts were systematically assessed in the continuous hydrogenation of ethyl levulinate (EL) in a fixed-bed reactor. The effect of acidic property of the SiO2 substrate on the catalytic properties was investigated. To justify the potential of its commercialization, significant attention was paid on the initial activity, proper operation window, by-products control, selectivity, and stability of the catalyst. The effect of reaction conditions, such as temperature and pressure, on the performance of the catalyst was also thoroughly studied. The development of alumina doped Cu/SiO2 catalyst strengthened the value-chain from cellulose to industrially important chemicals via LA and GVL. PMID:27377401

  4. Carbon Dioxide-Free Hydrogen Production with Integrated Hydrogen Separation and Storage.

    Science.gov (United States)

    Dürr, Stefan; Müller, Michael; Jorschick, Holger; Helmin, Marta; Bösmann, Andreas; Palkovits, Regina; Wasserscheid, Peter

    2017-01-10

    An integration of CO 2 -free hydrogen generation through methane decomposition coupled with hydrogen/methane separation and chemical hydrogen storage through liquid organic hydrogen carrier (LOHC) systems is demonstrated. A potential, very interesting application is the upgrading of stranded gas, for example, gas from a remote gas field or associated gas from off-shore oil drilling. Stranded gas can be effectively converted in a catalytic process by methane decomposition into solid carbon and a hydrogen/methane mixture that can be directly fed to a hydrogenation unit to load a LOHC with hydrogen. This allows for a straight-forward separation of hydrogen from CH 4 and conversion of hydrogen to a hydrogen-rich LOHC material. Both, the hydrogen-rich LOHC material and the generated carbon on metal can easily be transported to destinations of further industrial use by established transport systems, like ships or trucks. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Enhanced hydrogen storage on Li-doped defective graphene with B substitution: A DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yanan [School of Chemical Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Chu, Wei, E-mail: chuwei1965@scu.edu.cn [School of Chemical Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Jing, Fangli [School of Chemical Engineering, Sichuan University, Chengdu 610065, Sichuan (China); Zheng, Jian [State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Mianyang, 621010 (China); Sun, Wenjing [China-America Cancer Research Institute, Key Laboratory for Medical Molecular Diagnostics of Guangdong Province, Guangdong Medical University, Dongguan, Guangdong 523808 (China); Xue, Ying [Key Laboratory Green Chemistry & Technology of Ministry of Education (MOE), College of Chemistry, Sichuan University, Chengdu 610064, Sichuan (China)

    2017-07-15

    Highlights: • Li atoms were found to be well dispersed on defective structures without clustering. • First H{sub 2} with five different initial configurations on Li/MV, Li/DV, Li/BMV, Li/BDV were explored in order. • Each system could bind up to three H{sub 2} molecules with hydrogen average adsorption energies close to the range of 0.2–0.4 eV. • H{sub 2} molecules bind with systems through weak electrostatic interaction between Li cation and induced H{sub 2} dipole. • H{sub 2} adsorption and desorption on the studied systems can process under ambient conditions. - Abstract: The characteristics of hydrogen adsorption on Li-doped defective graphene systems were investigated using density functional theory (DFT) calculations. Four types of defective structures were selected. Li atoms were well dispersed on the defective graphene without clustering, evidenced by the binding energy value between Li and defective graphene than that of Li-Li{sub x}. Additionally, as the amount of adsorbed H{sub 2} molecules increase, the H{sub 2} molecules show tilting configuration toward the Li adatom. This is beneficial for more hydrogen adsorption under the electrostatic interaction. On these four stable structures, there were up to three polarized H{sub 2} molecules adsorbed on per Li adatom, with the average hydrogen adsorption energy in the range of approximately 0.2–0.4 eV. These results provide new focus on the nature of Li-doped defective graphene with sometimes B substitution medium, which could be considered as a promising candidate for hydrogen storage.

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

    Science.gov (United States)

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

    2015-05-05

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

  7. Photocatalytic degradation mechanisms of self-assembled rose-flower-like CeO2 hierarchical nanostructures

    International Nuclear Information System (INIS)

    Sabari Arul, N.; Mangalaraj, D.; Whan Kim, Tae

    2013-01-01

    Hierarchical rose-flower-like CeO 2 nanostructures were formed by using solvothermal and thermal annealing processes. The CeCO 3 OH thin film was transformed into CeO 2 roses due to thermal annealing. CeO 2 nanostructured roses exhibited excellent photocatalytic activity with a degradation rate of 65% for the azo dye acid orange 7 (AO7) under ultraviolet illumination. The fitting of the absorbance maximum versus time showed that the degradation of AO7 obeyed pseudo-first-order reaction kinetics. The enhancement of the photocatalytic activity for the CeO 2 roses was attributed to the high adsorptivity resulting from the surface active sites and special 4f electron configuration.

  8. Photochemical Hydrogen Doping Induced Embedded Two-Dimensional Metallic Channel Formation in InGaZnO at Room Temperature.

    Science.gov (United States)

    Kim, Myeong-Ho; Lee, Young-Ahn; Kim, Jinseo; Park, Jucheol; Ahn, Seungbae; Jeon, Ki-Joon; Kim, Jeong Won; Choi, Duck-Kyun; Seo, Hyungtak

    2015-10-27

    The photochemical tunability of the charge-transport mechanism in metal-oxide semiconductors is of great interest since it may offer a facile but effective semiconductor-to-metal transition, which results from photochemically modified electronic structures for various oxide-based device applications. This might provide a feasible hydrogen (H)-radical doping to realize the effectively H-doped metal oxides, which has not been achieved by thermal and ion-implantation technique in a reliable and controllable way. In this study, we report a photochemical conversion of InGaZnO (IGZO) semiconductor to a transparent conductor via hydrogen doping to the local nanocrystallites formed at the IGZO/glass interface at room temperature. In contrast to thermal or ionic hydrogen doping, ultraviolet exposure of the IGZO surface promotes a photochemical reaction with H radical incorporation to surface metal-OH layer formation and bulk H-doping which acts as a tunable and stable highly doped n-type doping channel and turns IGZO to a transparent conductor. This results in the total conversion of carrier conduction property to the level of metallic conduction with sheet resistance of ∼16 Ω/□, room temperature Hall mobility of 11.8 cm(2) V(-1) sec(-1), the carrier concentration at ∼10(20) cm(-3) without any loss of optical transparency. We demonstrated successful applications of photochemically highly n-doped metal oxide via optical dose control to transparent conductor with excellent chemical and optical doping stability.

  9. Hydrogen diffusion and microstructure in undoped and boron-dope hydrogenated amorphous silicon: An IR and SIMS study

    International Nuclear Information System (INIS)

    Mitra, S.

    1991-01-01

    Hydrogenated amorphous silicon (a-Si:H) prepared by rf sputtering of a polycrystalline Si target at various rf powers 50 ≤ P ≤ 550 W (0.27--2.97 W/cm 2 ), target to substrate distance 1 ≤ d ≤ 2 double-prime, and varying hydrogen partial pressures. Doping was accomplished by introducing diborane (B 2 H 6 ) in the plasma. Hydrogen diffusion was studied from the depth profiles obtained from the SIMS on multilayered a-Si:H/a-Si:(H,D)/a-Si:H samples. The properties of the samples were characterized by IR absorption, optical gap measurements and ESR. IR yielded quantitative and qualitative information total hydrogen content and the nature of the hydrogen bonding, respectively. Hence the hydrogen microstructure of the samples could be varied in a systematic manner and monitored from the hydrogen vibrational modes. The ESR gave information on the number of paramagnetic defects per unit volume in the samples. The IR absorption of both as-deposited and annealed samples were closely monitored and the results clearly demonstrate a strong correlation between hydrogen diffusion and its microstructure. It is shown that microvoids in a-Si:H play a critical role in the process of diffusion by inducing deep hydrogen trapping sites that render them immobile. Consequently, as the microvoid density increases beyond a critical density hydrogen diffusion is totally quenched. The diffusion results are discussed both in the context of multiple trapping transport of hydrogen in an exponential distribution of trapping sites and the floating bond model

  10. A comparative investigation of SO2 oxidative transfer over CuO with a CeO2 surface

    Science.gov (United States)

    Liu, Yifeng; Shen, Benxian; Pi, Zhipeng; Chen, Hua; Zhao, Jigang

    2017-04-01

    To further improve the catalytic desulfurization function of the Mg-Al spinel sulfur transfer agent in a fluid catalytic cracking (FCC) unit, the reaction paths of SO2 oxidation by O2 over the metal oxide surface of CuO (111) and CeO2 (111) were investigated. In reference to the fact that SO2 reacting with O2 over CuO was a Mars-van Krevelen cycle, a similar reaction law for SO2 oxidation over CeO2 was also verified by characterization methods (e.g., IR, XPS). Meanwhile, the molecular simulation results indicated that the rate-control step of SO2 oxidation over CeO2 (111) and CuO (111) was a SO3 desorption step. The lower energy barrier in the rate-control step corresponded to better catalytic performance; hence, it could explain the reason that CeO2 had a better sulfur oxidization transfer performance than CuO.

  11. Can Cu(II) ions be doped into the crystal structure of potassium hydrogen tartrate?

    OpenAIRE

    Srinivasan, Bikshandarkoil R.; Remesh, H.

    2015-01-01

    The differing binding preferences of the hydrogen tartrate ligand (HC4H4O6)- namely {\\mu}7-octadentate mode for potassium ion and bidentate mode for cupric ion rules out the doping (incorporation) of any Cu(II) ion into the crystal structure of potassium hydrogen tartrate. Hence, the claim of growth of copper doped potassium hydrogen tartrate viz. K0.96Cu0.04C4H5O6 by Mathivanan and Haris, Indian J Pure App Phys 51 (2013) 851-859 is untenable.

  12. CO2 Laser annealing of n-doped hydrogenated amorphous silicon

    International Nuclear Information System (INIS)

    Bertolotti, M.; Ferrari, A.; Evangelisti, F.; Fiorini, P.; Proietti, M.G.

    1985-01-01

    Low power CO 2 laser annealing of n-doped a-Si:H is reported. Conductivity and its activation energy, photoconductivity, absorption coefficient and dependence of photoconductivity on light power show changes which can be interpreted as due to a better doping efficiency

  13. Plasma-assisted adsorption of elemental mercury on CeO2/TiO2 at low temperatures

    Science.gov (United States)

    Liu, Lu; Zheng, Chenghang; Gao, Xiang

    2017-11-01

    Mercury is a kind of pollutants contained in flue gas which is hazardous for human beings. In this work, CeO2 was packed in the discharge zone of a plasma reactor to adsorb elemental mercury at low temperatures. Plasma-catalyst reactor can remove Hg0 efficiently with CeO2/TiO2 catalysts packed in the discharge zone. The Hg0 concentration continued to decrease gradually when the plasma was turned on, but not sank rapidly. This tendency was different with other catalysts. The treatment of plasma to CeO2/TiO2 catalysts has a promotion effect on the adsorption of Hg0. Plasma has the effect of changing the surface properties of the catalysts and the changes would restitute if the condition changed. The long-running test demonstrated that this method is an effective way to remove Hg0. The removal efficiency remained at above 99% throughout 12 hours when plasma had been turned on (15kV, 0.5 g packed CeO2/TiO2).

  14. Synthesis and physico-chemical characterization of CeO2/ZrO2-SO42- mixed oxides

    International Nuclear Information System (INIS)

    Hernandez E, J. M.; Silva R, R.; Garcia A, R.; Garcia S, L. A.; Handy, B. E.; Cardenas G, G.; Cueto H, A.

    2012-01-01

    Environmentally friendly solid-acid catalysts CeO 2 /ZrO 2 -SO 4 2- were prepared by the sol gel method varying CeO 2 content (10, 20 and 30 wt %) and using sulfation in situ, maintaining the sulfate ions amount present in the materials at 20 wt %. ZrO 2 and ZrO 2 -SO 4 2- were also prepared for comparison proposes using the same synthesis method. The materials were characterized by X-ray diffraction, nitrogen physisorption, potentiometric titration with n-butylamine, decomposition of 2-propanol and n-pentane isomerization. The specific surface area of ZrO 2 -SO 4 2- was high (160 m 2 /g) compared with the unmodified ZrO 2 (80 m 2 /g), however this area decreased with increasing the CeO 2 content (37-100 m 2 /g). There was no significant effect of CeO 2 on the tetragonal structure of ZrO 2 -SO 4 2- . The variation of acid sites amount runs parallel to the change of specific surface area. The acid sites amount decreased with increasing cerium oxide content. The decomposition of 2-propanol results fundamentally in the formation of dehydration products such as propylene and diisopropyl ether, both involving acid sites. In addition, a good performance during the n-pentane isomerization was observed for these materials. The selectivity towards isopentane reaches 84% when the Pt/CeO 2 /ZrO 2 -SO 4 2- catalyst with the highest CeO 2 content was used. (Author)

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

    International Nuclear Information System (INIS)

    Qian, Junchao; Chen, Feng; Wang, Fang; Zhao, Xiaobing; Chen, Zhigang

    2012-01-01

    Highlights: ► A novel, simple and eco-friendly approach for hierarchical, biomorphic CeO 2 hollow fibers with mesoporous tube walls is presented by using paper as template. ► The biomorphic CeO 2 fibers was composed of nanosheets with bimodal pore-size mesoporous distribution and exhibited high light-harvesting under sunlight irradiation. ► The CeO 2 microfibers biomimicking the natural plant structures have promising application for photodegradation of organic pollutants in water. -- Abstract: Hierarchical, biomorphic CeO 2 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 CeO 2 crystallites with grain size about 8 nm. The photocatalytic activity of the CeO 2 fibers was evaluated by photodegradation efficiency of methylene blue in aqueous solution under daylight irradiation. The characterized results show that the CeO 2 fibers faithfully replicated micro-fibrous structure derived from original template and possessed dramatic enhanced photocatalytic activity compared with bulk CeO 2 . This simple biotemplate method provides a cost-effective and eco-friendly route to obtain high performance photocatalysts.

  16. Metal-doped sodium aluminium hydrides as potential new hydrogen storage materials

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanovic, B. [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany); Brand, R.A. [Department of Physics, Gerhard-Mercator-Universitaet GH Duisburg, D-47048, Duisburg (Germany); Marjanovic, A.; Schwickardi, M.; Toelle, J. [Max-Planck-Institut fuer Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470, Muelheim an der Ruhr (Germany)

    2000-04-28

    Thermodynamics and kinetics of the reversible dissociation of metal-doped NaAlH{sub 4} as a hydrogen (or heat) storage system have been investigated in some detail. The experimentally determined enthalpies for the first (3.7 wt% of H) and the second dissociation step of Ti-doped NaAlH{sub 4} (3.0 wt% H) of 37 and 47 kJ/mol are in accordance with low and medium temperature reversible metal hydride systems, respectively. Through variation of NaAlH{sub 4} particle sizes, catalysts (dopants) and doping procedures, kinetics as well as the cyclization stability within cycle tests have been substantially improved with respect to the previous status [B. Bogdanovic, M. Schwickardi (1997)]. In particular, using combinations of Ti and Fe compounds as dopants, a cooperative (synergistic) catalytic effect of the metals Ti and Fe in enhancing rates of both de- and rehydrogenation of Ti/Fe-doped NaAlH{sub 4} within cycle tests, reaching a constant storage capacity of {proportional_to}4 wt% H{sub 2}, has been demonstrated. By means of {sup 57}Fe Moessbauer spectroscopy of the Ti/Fe-doped NaAlH{sub 4} before and throughout a cycle test, it has been ascertained that (1) during the doping procedure, nanosize metallic Fe particles are formed from the doping agent Fe(OEt){sub 2} and (2) already after the first dehydrogenation, the nanosize Fe particles with NaAlH{sub 4} present are probably transformed into an Fe-Al-alloy which throughout the cycle test remains practically unchanged. (orig.)

  17. Comparison of effective relative dielectric permittivities obtained by three independent ways for CeO2-Sm2O3 films prepared by EB-PVD (+IBAD) techniques

    International Nuclear Information System (INIS)

    Kundracik, F.; Neilinger, P.; Hartmanova, M.; Nadazdy, V.; Mansilla, C.

    2011-01-01

    Ceria, as material with relatively high dielectric permittivity, ε r , and ability to form films on the Si substrate, is a candidate for the gate dielectrics in the MOS devices. Doping with suitable e.g. trivalent rare earth oxides and suitable treatment after deposition (preparation) can improve their properties, e.g. ionic conductivity, dielectric permittivity and mechanical hardness. In this work, the dielectric properties of CeO 2 + Sm 2 O 3 films prepared by electron beam physical vapour deposition (EB-PVD) and some of them simultaneously also by the Ar + ionic beam assisted deposition (IBAD) techniques are analysed. (authors)

  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

    Directory of Open Access Journals (Sweden)

    Rodrigo F. Silva

    2011-01-01

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

  19. Conductive Boron-Doped Graphene as an Ideal Material for Electrocatalytically Switchable and High-Capacity Hydrogen Storage.

    Science.gov (United States)

    Tan, Xin; Tahini, Hassan A; Smith, Sean C

    2016-12-07

    Electrocatalytic, switchable hydrogen storage promises both tunable kinetics and facile reversibility without the need for specific catalysts. The feasibility of this approach relies on having materials that are easy to synthesize, possessing good electrical conductivities. Graphitic carbon nitride (g-C 4 N 3 ) has been predicted to display charge-responsive binding with molecular hydrogen-the only such conductive sorbent material that has been discovered to date. As yet, however, this conductive variant of graphitic carbon nitride is not readily synthesized by scalable methods. Here, we examine the possibility of conductive and easily synthesized boron-doped graphene nanosheets (B-doped graphene) as sorbent materials for practical applications of electrocatalytically switchable hydrogen storage. Using first-principle calculations, we find that the adsorption energy of H 2 molecules on B-doped graphene can be dramatically enhanced by removing electrons from and thereby positively charging the adsorbent. Thus, by controlling charge injected or depleted from the adsorbent, one can effectively tune the storage/release processes which occur spontaneously without any energy barriers. At full hydrogen coverage, the positively charged BC 5 achieves high storage capacities up to 5.3 wt %. Importantly, B-doped graphene, such as BC 49 , BC 7 , and BC 5 , have good electrical conductivity and can be easily synthesized by scalable methods, which positions this class of material as a very good candidate for charge injection/release. These predictions pave the route for practical implementation of electrocatalytic systems with switchable storage/release capacities that offer high capacity for hydrogen storage.

  20. Mesoscopic quantum effects in a bad metal, hydrogen-doped vanadium dioxide

    Science.gov (United States)

    Hardy, Will J.; Ji, Heng; Paik, Hanjong; Schlom, Darrell G.; Natelson, Douglas

    2017-05-01

    The standard treatment of quantum corrections to semiclassical electronic conduction assumes that charge carriers propagate many wavelengths between scattering events, and succeeds in explaining multiple phenomena (weak localization magnetoresistance (WLMR), universal conductance fluctuations, Aharonov-Bohm oscillations) observed in polycrystalline metals and doped semiconductors in various dimensionalities. We report apparent WLMR and conductance fluctuations in H x VO2, a poor metal (in violation of the Mott-Ioffe-Regel limit) stabilized by the suppression of the VO2 metal-insulator transition through atomic hydrogen doping. Epitaxial thin films, single-crystal nanobeams, and nanosheets show similar phenomenology, though the details of the apparent WLMR seem to depend on the combined effects of the strain environment and presumed doping level. Self-consistent quantitative analysis of the WLMR is challenging given this and the high resistivity of the material, since the quantitative expressions for WLMR are derived assuming good metallicity. These observations raise the issue of how to assess and analyze mesoscopic quantum effects in poor metals.

  1. Hydrogen desorption reactions of Li-N-H hydrogen storage system: Estimation of activation free energy

    International Nuclear Information System (INIS)

    Matsumoto, Mitsuru; Haga, Tetsuya; Kawai, Yasuaki; Kojima, Yoshitsugu

    2007-01-01

    The dehydrogenation reactions of the mixtures of lithium amide (LiNH 2 ) and lithium hydride (LiH) were studied under an Ar atmosphere by means of temperature programmed desorption (TPD) technique. The dehydrogenation reaction of the LiNH 2 /LiH mixture was accelerated by addition of 1 mol% Ti(III) species (k = 3.1 x 10 -4 s -1 at 493 K), and prolonged ball-milling time (16 h) further enhanced reaction rate (k = 1.1 x 10 -3 s -1 at 493 K). For the hydrogen desorption reaction of Ti(III) doped samples, the activation energies estimated by Kissinger plot (95 kJ mol -1 ) and Arrhenius plot (110 kJ mol -1 ) were in reasonable agreement. The LiNH 2 /LiH mixture without Ti(III) species, exhibited slower hydrogen desorption process and the kinetic traces deviated from single exponential behavior. The results indicated the Ti(III) additives change the hydrogen desorption reaction mechanism of the LiNH 2 /LiH mixture

  2. Structural, magnetic and electronic structural properties of Mn doped CeO2 nanoparticles

    Science.gov (United States)

    Kumari, Kavita; Vij, Ankush; Hashim, Mohd.; Chae, K. H.; Kumar, Shalendra

    2018-05-01

    Nanoparticles of Ce1-xMnxO2, (x=0.0, 0.01, and 0.05) have been synthesized by using co-precipitation method, and then characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), near edge x-ray absorption fine structure (NEXAFS) spectroscopy and dc magnetization measurements. XRD results clearly showed that the all the samples have single phase nature and exclude the presence of any secondary phase. The average particle size calculated using XRD TEM measurements found to decrease with increase in Mn doping in the range of 4.0 - 9.0 nm. The structural parameters such as strain, interplaner distance and lattice parameter is observed to decrease with increase in doping. The morphology of Ce1-xMnxO2 nanoparticles measured using TEM micrographs indicate that nanoparticle have spherical shape morphology. Magnetic hysteresis curve for Ce1-xMnxO2, (x = 0.0, 0.01, and 0.05) confirms the ferromagnetic ordering room temperature. The value of saturation magnetization is observed to decrease with increase in temperature from 10 K to 300 K. The NEXAFS spectra measured at Ce M4,5 edge reveals that Ce-ions are in +4 valance state.

  3. Magnetism mediated by a majority of [Fe³⁺ + VO²⁻] complexes in Fe-doped CeO₂ nanoparticles.

    Science.gov (United States)

    Paidi, V K; Ferreira, N S; Goltz, D; van Lierop, J

    2015-08-26

    We examine the role of Fe(3+) and vacancies (V(O)) on the magnetism of Fe-doped CeO2 nanoparticles. Magnetic nanoparticles of Ce(100-x)Fe(x)O2 (x  =  0, 0.26, 1.82, 2.64, 5.26, 6.91, and 7.22) were prepared by a co-precipitation method, and their structural, compositional and magnetic properties were investigated. The CeO2 nanoparticles had a mixed valance of Ce(4+) and Ce(3+) ions, and doping introduced Fe(3+) ions. The decrease in Ce(3+) and increase in Fe(3+) concentrations indicated the presence of more [Fe(3+) + V(O)(2-)] complexes with Fe loading in the particles. Charge neutralization, Fe(3+) + V(O)(2-) + 2Ce(4+) ↔ 2Ce(3+) + Fe(3+), identified the impact of V(O) on the magnetism, where our results suggest that the Fe-doped CeO2 nanoparticle magnetism is mediated by a majority of [Fe(3+) + V(O)(2-)]-Ce(3+) -[Fe(3+) + V(O)(2-)] complexes.

  4. An open aperture z-scan study of Sr2CeO4 blue phosphor

    International Nuclear Information System (INIS)

    Seema, R.; Sandeep, C.S. Suchand; Philip, Reji; Kalarikkal, Nandakumar

    2011-01-01

    Highlights: → Sr 2 CeO 4 blue phosphor has been prepared by a solid state reaction method. → The XRD study confirms that the structure of the system is orthorhombic. → The TEM reveals that Sr 2 CeO 4 is composed of elongated spherical structures of length ∼0.2-0.6 μm. → The FFT of TEM, XRD peaks and the JCPDS values are compared, from which the Sr 2 CeO 4 phase is reconfirmed. → A z-scan measurement gives the effective two-photon absorption coefficient to be 3.9 x 10 -11 m/W. - Abstract: Sr 2 CeO 4 blue phosphor has been prepared by the solid-state reaction method. The X-ray diffraction (XRD) study confirms the structure of the system to be orthorhombic. High resolution electron transmission microscopy reveals that Sr 2 CeO 4 prepared by the solid state reaction method is composed of elongated spherical structures of length ∼0.2-0.6 μm and width ∼90-150 nm. The excitation spectrum shows a broad band which peaks at 275 nm. The emission spectrum shows a broad band which peaks at 467 nm when excited at 275 nm. The emission band is assigned to the energy transfer between the molecular orbital of the ligand and charge transfer (CT) state of the Ce 4+ ion. The Commission International de l'Eclairage (CIE) co-ordinates are x = 0.15, and y = 0.23. The nonlinear absorption behavior of Sr 2 CeO 4 has been investigated using the open aperture z-scan technique. The calculated effective two-photon absorption coefficient shows that the Sr 2 CeO 4 blue phosphor is a promising optical limiting material.

  5. Cooperative CEO Identity and Efficient Governance: Member or Outside CEO?

    NARCIS (Netherlands)

    Q.X. Liang (Qiao Xin); G.W.J. Hendrikse (George)

    2012-01-01

    textabstractA principal-agent model is formulated to capture the efficiency of cooperatives with a member CEO and cooperatives with an employed outsider as CEO. Results of the model show that the incentive strength regarding the member CEO is stronger compared to that of the outside CEO in order to

  6. Influence of dopant concentration on spectroscopic properties of Sr2CeO4:Yb nanocrystals

    Science.gov (United States)

    Stefanski, M.; Kędziorski, A.; Hreniak, D.; Strek, W.

    2017-12-01

    Optical properties of Sr2CeO4:Yb nanocrystals synthesized via Pechini's method are reported. The samples were characterized by X-ray diffraction data measurements. The unit cell parameters were determined using Rietveld refinement. It was found that they decreased with increasing amount of Yb ions. The absorption, excitation, emission spectra and luminescence decay profiles of the Sr2CeO4:Yb nanocrystals were investigated. It was observed that optical properties were strongly dependent on Yb concentration. It was found that Yb3+-O2- charge transfer transitions have great influence on the absorption spectra. It can be seen in the emission spectra that in addition to standard bands/lines corresponding to Ce-O metal-to-ligand charge transfer of Sr2CeO4 and f-f transitions of Yb3+, there is emission band centered at 744 nm. Its intensity depends on the concentration of the dopant. Recorded decay times become shorter with increasing dopant concentration due to the Yb3+ concentration quenching. Excitation spectra indicate the energy transfer from Ce-O charge transfer states to Yb3+2F5/2 state. The issue of appearance of down-conversion process in Sr2CeO4:Yb nanocrystals is considered.

  7. Effect of hydrogen doping on the properties of Al and F co-doped ZnO films for thin film silicon solar cell applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fang-Hsing, E-mail: fansen@dragon.nchu.edu.tw; Yang, Tung-Hsin

    2016-04-30

    Aluminum and fluorine co-doped zinc oxide (AFZO) thin films were prepared in Ar + H{sub 2} atmospheres by rf magnetron sputtering at room temperature. The structural, electrical, and optical properties of the prepared films were investigated using X-ray diffraction, scanning electron microscopy, atomic force microscopy, Hall-effect measurement, X-ray photoelectron spectroscopy, and ultraviolet–visible spectrometry, and their dependence on deposition atmosphere (i.e. H{sub 2} / (H{sub 2} + Ar) ratio) was studied. The resulting films showed a (0 0 2) diffraction peak, indicating a typical wurtzite structure, and the optimal film crystallinity was obtained with the H{sub 2} / (H{sub 2} + Ar) ratio of 3%. The electrical resistivity of AFZO films decreased to 9.16 × 10{sup −4} Ω-cm, which was lower than ZnO:Al and ZnO:F films due to double doping effect of Al and F. The resistivity further decreased to below 5 × 10{sup −4} Ω-cm for the AFZO film with the H{sub 2} / (H{sub 2} + Ar) ratio of 3%–5%. All the films regardless of hydrogen content displayed high transmittances (> 92%) in the visible wavelength range. Applying the developed AFZO films as front transparent electrodes, amorphous Si thin film solar cells were fabricated and the open-circuit voltage, fill factor, and efficiency of the cell with the hydrogenated AFZO film were improved in contrast to those without the hydrogenated film. - Highlights: • H{sub 2} doping improves optoelectronic properties of Al, F co-doped ZnO (AFZO) films. • Resistivity of AFZO films decreases to 4.4 × 10{sup −4} Ω-cm with the 3% H{sub 2}/(Ar + H{sub 2}) ratio. • AFZO films show high average visible transmittances of above 92%. • Efficiency of a-Si thin film solar cells is improved by AFZO:H as front electrode.

  8. Hydrogen storage material and process using graphite additive with metal-doped complex hydrides

    Science.gov (United States)

    Zidan, Ragaiy [Aiken, SC; Ritter, James A [Lexington, SC; Ebner, Armin D [Lexington, SC; Wang, Jun [Columbia, SC; Holland, Charles E [Cayce, SC

    2008-06-10

    A hydrogen storage material having improved hydrogen absorbtion and desorption kinetics is provided by adding graphite to a complex hydride such as a metal-doped alanate, i.e., NaAlH.sub.4. The incorporation of graphite into the complex hydride significantly enhances the rate of hydrogen absorbtion and desorption and lowers the desorption temperature needed to release stored hydrogen.

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

    International Nuclear Information System (INIS)

    Chang, Ling; Wang, Fengxian; Xie, Dong; Zhang, Jun; Du, Gaohui

    2013-01-01

    Graphical abstract: - Highlights: • Porous CeO 2 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 CeO 2 exhibits a rapid adsorption to Rhodamine B with a removal efficiency of ∼99%. • Porous CeO 2 retains the same performances in different pH solutions. - Abstract: We report a graphite oxide-mediated approach for synthesizing porous CeO 2 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 N 2 adsorption. The as-prepared CeO 2 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 CeO 2 quadrangular prisms with the pore distributions around 4 nm and 30 nm. The dye sorption capacity of the porous CeO 2 is investigated, which exhibits a rapid adsorption to rhodamine B with a high removal efficiency of ∼99%. Moreover, the CeO 2 absorbent retains the same performances in different pH solutions

  10. Generation of hydrogen free radicals from water for fuels by electric field induction

    International Nuclear Information System (INIS)

    Nong, Guangzai; Chen, Yiyi; Li, Ming; Zhou, Zongwen

    2015-01-01

    Highlights: • Hydrogen free radicals are generated from water splitting. • Hydrogen fuel is generated from water by electric field induction. • Hydrocarbon fuel is generated from CO_2 and water by electric field induction. - Abstract: Water is the most abundant resource for generating hydrogen fuel. In addition to dissociating H"+ and "−OH ions, certain water molecules dissociate to radicals under an electric field are considered. Therefore, an electric field inducing reactor is constructed and operated to generate hydrogen free radicals in this paper. Hydrogen free radicals begin to be generated under a 1.0 V electric field, and increasing the voltage and temperature increases the number of hydrogen free radicals. The production rate of hydrogen free radicals is 0.245 mmol/(L h) at 5.0 V and room temperature. The generated hydrogen free radicals are converted to polymer fuel and hydrogen fuel at production rates of 0.0093 mmol/(L h) and 0.0038 mmol/(L h) respectively, under 5.0 V and 0.25 mA. The results provide a way to generate hydrogen free radicals, which might be used to generate hydrocarbon fuel in industrial manufacture.

  11. Development and characterization of nickel catalysts supported in CeO2-ZrO2-Al2O3, CeO2-La2O3-Al2O3 e ZrO2-La2O3-Al2O3 matrixes evaluated for methane reforming reactions

    International Nuclear Information System (INIS)

    Abreu, Amanda Jordão de

    2012-01-01

    Nowadays, the methane reforming is large interest industrial for the take advantage of these gas in production the hydrogen and synthesis gas (syngas). Among in the reactions of methane stand of the reactions steam reforming and carbon dioxide reforming of methane. The main catalysts uses in the methane reforming is Ni/Al 2 O 3 . However, the supported-nickel catalyst is susceptible to the deactivation or the destruction by coke deposition. The carbon dissolves in the nickel crystallite and its diffuses through the nickel, leading for formation of the carbon whiskers, which results in fragmentation of the catalyst. Modification of such catalysts, like incorporation of suitable promoters, is desirable to achieve reduction of the methane hydrogenolysis and/or promotion of the carbon gasification. Catalysts 5%Ni/Al 2 O 3 supported on solid solutions formed by ZrO 2 -CeO 2 , La 2 O 3 and CeO 2 -ZrO 2 -La 2 O 3 were prepared, characterized and evaluated in reactions steam and carbon dioxide reforming and partial oxidation of methane with objective the value effect loading solution solid in support. The supports were prepared by co-precipitation method and catalysts were prepared by impregnation method and calcined at 500 deg C. The supports and catalysts were characterized by Nitrogen Adsorption, method -rays diffraction (XRD), X-rays dispersive spectroscopy (XDS), spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR) to and temperature programmed reduction (TPR), Raman Spectroscopy, X-ray absorption spectroscopy and Thermogravimetric Analysis. After all the catalytic reactions check which the addition of solid solution is beneficial for Ni/Al 2 O 3 catalysts and the best catalysts are Ni/CeO 2 -La 2 O 3 -Al 2 O 3 . (author)

  12. Enhanced hydrogen storage properties of MgH2 co-catalyzed with K2NiF6 and CNTs.

    Science.gov (United States)

    Sulaiman, N N; Ismail, M

    2016-12-06

    The composite of MgH 2 /K 2 NiF 6 /carbon nanotubes (CNTs) is prepared by ball milling, and its hydrogenation properties are studied for the first time. MgH 2 co-catalyzed with K 2 NiF 6 and CNTs exhibited an improvement in the onset dehydrogenation temperature and isothermal de/rehydrogenation kinetics compared with the MgH 2 -K 2 NiF 6 composite. The onset dehydrogenation temperature of MgH 2 doped with 10 wt% K 2 NiF 6 and 5 wt% CNTs is 245 °C, which demonstrated a reduction of 25 °C compared with the MgH 2 + 10 wt% K 2 NiF 6 composite. In terms of rehydrogenation kinetics, MgH 2 doped with 10 wt% K 2 NiF 6 and 5 wt% CNTs samples absorbed 3.4 wt% of hydrogen in 1 min at 320 °C, whereas the MgH 2 + 10 wt% K 2 NiF 6 sample absorbed 2.6 wt% of hydrogen under the same conditions. For dehydrogenation kinetics at 320 °C, the MgH 2 + 10 wt% K 2 NiF 6 + 5 wt% CNTs sample released 3.3 wt% hydrogen after 5 min of dehydrogenation. By contrast, MgH 2 doped with 10 wt% K 2 NiF 6 released 3.0 wt% hydrogen in the same time period. The apparent activation energy, E a , for the dehydrogenation of MgH 2 doped with 10 wt% K 2 NiF 6 reduced from 100.0 kJ mol -1 to 70.0 kJ mol -1 after MgH 2 was co-doped with 10 wt% K 2 NiF 6 and 5 wt% CNTs. Based on the experimental results, the hydrogen storage properties of the MgH 2 /K 2 NiF 6 /CNTs composite is enhanced because of the catalytic effects of the active species of KF, KH and Mg 2 Ni that are formed in situ during dehydrogenation, as well as the unique structure of CNTs.

  13. The effect of dissolved hydrogen on the dissolution of {sup 233}U doped UO{sub 2}(s) high burn-up spent fuel and MOX fuel

    Energy Technology Data Exchange (ETDEWEB)

    Carbol, P. [Inst. for Transuranium Elements, Karlsruhe (Germany); Spahiu, K. (ed.) [and others

    2005-03-01

    In this report the results of the experimental work carried out in a large EU-research project (SFS, 2001-2004) on spent fuel stability in the presence of various amounts of near field hydrogen are presented. Studies of the dissolution of {sup 233}U doped UO{sub 2}(s) simulating 'old' spent fuel were carried out as static leaching tests, autoclave tests with various hydrogen concentrations and electrochemical tests. The results of the leaching behaviour of a high burn-up spent fuel pellet in 5 M NaCl solutions in the presence of 3.2 bar H{sub 2} pressure and of MOX fuel in dilute synthetic groundwater under 53 bar H{sub 2} pressure are also presented. In all the experimental studies carried out in this project, a considerable effect of hydrogen in the dissolution rates of radioactive materials was observed. The experimental results obtained in this project with a-doped UO{sub 2}, high burn-up spent fuel and MOX fuel together with literature data give a reliable background to use fractional alteration/dissolution rates for spent fuel of the order of 10{sup -6}/yr - 10{sup -8}/yr with a recommended value of 4x10{sup -7}/yr for dissolved hydrogen concentrations above 10{sup -3} M and Fe(II) concentrations typical for European repository concepts. Finally, based on a review of the experimental data and available literature data, potential mechanisms of the hydrogen effect are also discussed. The work reported in this document was performed as part of the Project SFS of the European Commission 5th Framework Programme under contract no FIKW-CT-2001-20192 SFS. It represents the deliverable D10 of the experimental work package 'Key experiments using a-doped UO{sub 2} and real spent fuel', coordinated by SKB with the participation of ITU, FZK-INE, ENRESA, CIEMAT, ARMINES-SUBATECH and SKB.

  14. The effect of dissolved hydrogen on the dissolution of {sup 233}U doped UO{sub 2}(s) high burn-up spent fuel and MOX fuel

    Energy Technology Data Exchange (ETDEWEB)

    Carbol, P [Inst. for Transuranium Elements, Karlsruhe (Germany); Spahiu, K [and others

    2005-03-01

    In this report the results of the experimental work carried out in a large EU-research project (SFS, 2001-2004) on spent fuel stability in the presence of various amounts of near field hydrogen are presented. Studies of the dissolution of {sup 233}U doped UO{sub 2}(s) simulating 'old' spent fuel were carried out as static leaching tests, autoclave tests with various hydrogen concentrations and electrochemical tests. The results of the leaching behaviour of a high burn-up spent fuel pellet in 5 M NaCl solutions in the presence of 3.2 bar H{sub 2} pressure and of MOX fuel in dilute synthetic groundwater under 53 bar H{sub 2} pressure are also presented. In all the experimental studies carried out in this project, a considerable effect of hydrogen in the dissolution rates of radioactive materials was observed. The experimental results obtained in this project with a-doped UO{sub 2}, high burn-up spent fuel and MOX fuel together with literature data give a reliable background to use fractional alteration/dissolution rates for spent fuel of the order of 10{sup -6}/yr - 10{sup -8}/yr with a recommended value of 4x10{sup -7}/yr for dissolved hydrogen concentrations above 10{sup -3} M and Fe(II) concentrations typical for European repository concepts. Finally, based on a review of the experimental data and available literature data, potential mechanisms of the hydrogen effect are also discussed. The work reported in this document was performed as part of the Project SFS of the European Commission 5th Framework Programme under contract no FIKW-CT-2001-20192 SFS. It represents the deliverable D10 of the experimental work package 'Key experiments using a-doped UO{sub 2} and real spent fuel', coordinated by SKB with the participation of ITU, FZK-INE, ENRESA, CIEMAT, ARMINES-SUBATECH and SKB.

  15. Hydrogenation of gold-related levels in silicon by electrolytic doping

    International Nuclear Information System (INIS)

    Pearton, S.J.; Hansen, W.L.; Haller, E.E.; Kahn, J.M.

    1984-01-01

    The deep gold-related donor and acceptor levels in silicon have been neutralized to several μm depth by introducing atomic hydrogen using an electrolytic method. Using phosphoric or sulfuric acid as the electrolyte, it is possible to dope the crystalline silicon with hydrogen at elevated temperatures (200--280 0 C) allowing direct comparison with other means of introduction, such as hydrogen plasma exposure. We find the electrolytic method is not as efficient as plasma treatment for the same conditions, possibly due to oxide formation during the immersion in the acid

  16. Improved Dehydrogenation Properties of 2LiNH2-MgH2 by Doping with Li3AlH6

    Directory of Open Access Journals (Sweden)

    Shujun Qiu

    2017-01-01

    Full Text Available Doping with additives in a Li-Mg-N-H system has been regarded as one of the most effective methods of improving hydrogen storage properties. In this paper, we prepared Li3AlH6 and evaluated its effect on the dehydrogenation properties of 2LiNH2-MgH2. Our studies show that doping with Li3AlH6 could effectively lower the dehydrogenation temperatures and increase the hydrogen content of 2LiNH2-MgH2. For example, 2LiNH2-MgH2-0.1Li3AlH6 can desorb 6.43 wt % of hydrogen upon heating to 300 °C, with the onset dehydrogenation temperature at 78 °C. Isothermal dehydrogenation testing indicated that 2LiNH2-MgH2-0.1Li3AlH6 had superior dehydrogenation kinetics at low temperature. Moreover, the release of byproduct NH3 was successfully suppressed. Measurement of the thermal diffusivity suggests that the enhanced dehydrogenation properties may be ascribed to the fact that doping with Li3AlH6 could improve the heat transfer for solid–solid reaction.

  17. Investigation of low-resistivity from hydrogenated lightly B-doped diamond by ion implantation

    Directory of Open Access Journals (Sweden)

    Cui Xia Yan et al

    2008-01-01

    Full Text Available We have implanted boron (B ions (dosage: 5×1014 cm-2 into diamond and then hydrogenated the sample by implantating hydrogen ions at room temperature. A p-type diamond material with a low resistivity of 7.37 mΩ cm has been obtained in our experiment, which suggests that the hydrogenation of B-doped diamond results in a low-resistivity p-type material. Interestingly, inverse annealing, in which carrier concentration decreased with increasing annealing temperature, was observed at annealing temperatures above 600 °C. In addition, the formation mechanism of a low-resistivity material has been studied by density functional theory calculation using a plane wave method.

  18. PALLADIUM DOPED TIN OXIDE BASED HYDROGEN GAS SENSORS FOR SAFETY APPLICATIONS

    International Nuclear Information System (INIS)

    Kasthurirengan, S.; Behera, Upendra; Nadig, D. S.

    2010-01-01

    Hydrogen is considered to be a hazardous gas since it forms a flammable mixture between 4 to 75% by volume in air. Hence, the safety aspects of handling hydrogen are quite important. For this, ideally, highly selective, fast response, small size, hydrogen sensors are needed. Although sensors based on different technologies may be used, thin-film sensors based on palladium (Pd) are preferred due to their compactness and fast response. They detect hydrogen by monitoring the changes to the electrical, mechanical or optical properties of the films. We report the development of Pd-doped tin-oxide based gas sensors prepared on thin ceramic substrates with screen printed platinum (Pt) contacts and integrated nicrome wire heaters. The sensors are tested for their performances using hydrogen-nitrogen gas mixtures to a maximum of 4%H 2 in N 2 . The sensors detect hydrogen and their response times are less than a few seconds. Also, the sensor performance is not altered by the presence of helium in the test gas mixtures. By the above desired performance characteristics, field trials of these sensors have been undertaken. The paper presents the details of the sensor fabrication, electronic circuits, experimental setup for evaluation and the test results.

  19. FeS2-doped MoS2 nanoflower with the dominant 1T-MoS2 phase as an excellent electrocatalyst for high-performance hydrogen evolution

    International Nuclear Information System (INIS)

    Zhao, Xue; Ma, Xiao; Lu, Qingqing; Li, Qun; Han, Ce; Xing, Zhicai; Yang, Xiurong

    2017-01-01

    Well-established methods to improve the hydrogen evolution reaction (HER) performances include, but are not limited to, tailoring the morphology and electronic structure of transition metal dichalcogenides (TMDs), and doping of earth abundant chemicals such as iron pyrite FeS 2 into existing TMDs. In this work, MoS 2 nanoflowers with the majority being octahedral MoS 2 (1T-MoS 2 ) and doped with FeS 2 were prepared and applied to HER. The as-prepared catalysts were characterized by X-ray absorption fine structure at the K-edge of Mo, S, and Fe to probe the local electronic structures. The resulting nanomaterial was identified to be FeS 2 doped MoS 2 nanoflower (denoted as Fe-MoS 2 NF) with 66% 1T-MoS 2 which was the metallic phase and could drastically boost the HER properties. The Fe-MoS 2 NF exhibited high HER performance with a Tafel slope of 82 mV dec −1 and it needs 136 mV to achieve a current density of 10 mA cm −2 . The synthesis of Fe-MoS 2 NF with refined morphology and active electronic structure is expected to open a new era for improving the catalytic activity and stability of MoS 2 .

  20. Hydrophilic CeO2 nanocubes protect pancreatic β-cell line INS-1 from H2O2-induced oxidative stress

    Science.gov (United States)

    Lyu, Guang-Ming; Wang, Yan-Jie; Huang, Xue; Zhang, Huai-Yuan; Sun, Ling-Dong; Liu, Yan-Jun; Yan, Chun-Hua

    2016-04-01

    Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at the highest dose of 200 μg mL-1 over the time scale of 72 h, while being able to protect INS-1 cells from H2O2-induced cytotoxicity even after protein adsorption. It is also noteworthy that nanoceria with a smaller hydrodynamic radius exhibit stronger antioxidant and anti-apoptotic effects, which is consistent with their H2O2 quenching capability in biological systems. These findings suggest that nanoceria can be used as an excellent antioxidant for controlling oxidative stress-induced pancreatic β-cell damage.Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at

  1. Synthesis of feather-like CeO2 microstructures and enzymatic electrochemical catalysis for trichloroacetic acid

    Science.gov (United States)

    Xiao, Xin; Zhang, Dong En; Zhang, Fan; Gong, Jun Yan; Zhang, Xiao Bo; Wang, Yi Hui; Ma, Juan Juan; Tong, Zhi Wei

    Novel feather-like CeO2 microstructures were achieved by a thermal decomposition approach of Ce(OH)CO3 precursor. The Ce(OH)CO3 was obtained from a solvothermal method employing Ce(NO3)3.6H2O with C6H12N4 and C16H33(CH3)3NBr (CTAB) at 190∘C in a water-PEG-200 mixed solution. The feather-like CeO2 dendrite was obtained by thermal conversion of the feather-like Ce(OH)CO3 at 650∘C in air. A reasonable growth mechanism was proposed with the soft-template effect of PEG-200. The electrochemical behavior and enzyme activity of myoglobin (Mb) immobilized on CeO2-Nafion modified glassy carbon electrode (GCE) are demonstrated by cyclic voltammetric measurements. The results indicate that CeO2 can obviously promote the direct electron transfer between the Mb redox centers and the electrode. The Mb on CeO2-Nafion behaves as an elegant performance on the electrochemical reduction of trichloroacetic acid (TCA) from 0.32μM to 2.28μM. The detection limit is estimated to be 0.08μM.

  2. Rational design of octahedron and nanowire CeO2@MnO2 core-shell heterostructures with outstanding rate capability for asymmetric supercapacitors.

    Science.gov (United States)

    Zhu, Shi Jin; Jia, Jia Qi; Wang, Tian; Zhao, Dong; Yang, Jian; Dong, Fan; Shang, Zheng Guo; Zhang, Yu Xin

    2015-10-14

    Two kinds of novel CeO2@MnO2 nanostructures have been synthesized via a self-assembly strategy. The as-prepared CeO2 nanowire@MnO2 nanostructures exhibited unprecedented pseudocapacitance performance (255 F g(-1)) with outstanding rate capability. A new mechanism based on the synergistic effect between CeO2 and MnO2 was proposed to interpret this phenomenon. When assembled as an asymmetric supercapacitor, an energy density of 27.5 W h kg(-1) with a maximum power density of 1.6 kW kg(-1) was achieved for CeO2 nanowire@MnO2 nanostructures.

  3. Ultraviolet-visible electroluminescence from metal-oxide-semiconductor devices with CeO2 films on silicon

    International Nuclear Information System (INIS)

    Lv, Chunyan; Zhu, Chen; Wang, Canxing; Li, Dongsheng; Ma, Xiangyang; Yang, Deren

    2015-01-01

    We report on ultraviolet-visible (UV-Vis) electroluminescence (EL) from metal-oxide-semiconductor (MOS) devices with the CeO 2 films annealed at low temperatures. At the same injection current, the UV-Vis EL from the MOS device with the 550 °C-annealed CeO 2 film is much stronger than that from the counterpart with the 450 °C-annealed CeO 2 film. This is due to that the 550 °C-annealed CeO 2 film contains more Ce 3+ ions and oxygen vacancies. It is tentatively proposed that the recombination of the electrons in multiple oxygen-vacancy–related energy levels with the holes in Ce 4f 1 energy band pertaining to Ce 3+ ions leads to the UV-Vis EL

  4. 3D hierarchical dandelion-like NiCo{sub 2}O{sub 4}/N-doped carbon/Ni foam for an effective binder-free supercapacitor electrode

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xiaoyang; Hong, Wei; Zhao, Huilin; Song, Yahui; Qiu, Haixia, E-mail: haixiaqiuls@163.com; Gao, Jianping

    2017-01-15

    In this work, the 3D hierarchical dandelion-like NiCo{sub 2}O{sub 4}/N-doped carbon/Ni foam has been developed by introducing PANI as the precursor of N-doped carbon. Meanwhile, the NiCo{sub 2}O{sub 4}/N-doped carbon/Ni foam with a novel 3D hierarchical dandelion-like structure was verified by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy, etc. In addition, the NiCo{sub 2}O{sub 4}/N-doped carbon/Ni foam was directly used as a binder-free supercapacitor electrode and its performances were investigated by cycle voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy. The results show that the obtained NiCo{sub 2}O{sub 4}/N-doped carbon/Ni foam electrode owns good electrochemical performances, such as high specific capacitance (864 F/g at 1 A/g) and good cycling stability, owing to the porous feature from its novel 3D hierarchical dandelion-like structure. - Highlights: • The 3D hierarchical dandelion-like NiCo{sub 2}O{sub 4}/N-doped carbon/Ni foam was prepared. • It can be directly used as a binder-free supercapacitor electrode. • It owns good electrochemical performances.

  5. CEOS precipitation constellation

    Science.gov (United States)

    Neeck, Steven P.; Oki, Riko

    2007-10-01

    The outcomes of the 19th Committee on Earth Observing Satellites (CEOS) Plenary held in London in November 2005, recognized that the CEOS Implementation Plan for Space-Based Observations for Global Earth Observation System of Systems (GEOSS) should: - identify the supply of space-based observations required to satisfy the requirements expressed by the 10-year implementation plan for GEOSS; and - propose an innovative process whereby the many disparate types of Earth observing programs funded by CEOS Member agencies might contribute to the supply of the required observations. The CEOS Task Force charged with drafting the CEOS Implementation Plan for Space-Based Observations for GEOSS focused its early efforts on the creation of a 'new planning process' which would satisfy the various criteria demanded by member space agencies, and which would hopefully encourage a new phase of specificity and focus in the multi-lateral co-operation efforts undertaken by space agencies under the CEOS umbrella - resulting in improved engagement of all CEOS Members and real implementation results. The CEOS Constellations is the title given to this new process, and four pilot studies have been initiated in order to pioneer and test the concept. The Japan Aerospace Exploration Agency (JAXA) and the National Aeronautics and Space Administration (NASA) were selected as the lead agencies for the study of the development of a CEOS Precipitation Constellation with the support of other CEOS space agency and user community participants. The goals, approach, and anticipated outcomes for the study will be discussed.

  6. CO2-free hydrogen as a substitute to fossil fuels: What are the targets? Prospective assessment of the hydrogen market attractiveness

    International Nuclear Information System (INIS)

    Mansilla, C.; Avril, S.; Imbach, J.; Le Duigou, A.

    2012-01-01

    Hydrogen is usually presented as a promising energy carrier that has a major role to play in low carbon mobility, through the use of fuel cells. However, such a market is not expected in the short term. In the meantime, hydrogen may also contribute to reduce carbon emissions in diverse sectors: oil refining, low carbon mobility through the industrial deployment of advanced bio-fuels, natural gas consumption, and methanol production. According to the targeted market, objective costs are rather different; and so is the reachable mitigated CO 2 amount. This paper assesses the dynamics of these markets' attractiveness, in order to provide target costs for CO 2 -free hydrogen production. The potential of the markets of hydrogen as a fuel and hydrogen for the biomass-to-liquid production is highlighted, as they could represent significant volumes by 2050, as well as interesting perspectives for CO 2 emission reduction. However the targets are very sensitive to the CO 2 price, thus highlighting the requirement for economic instruments in order to facilitate the penetration of such technologies. Hydrogen is then highlighted as a key player of the energy system in the years to come, as the connection of the energy and mobility sectors. (authors)

  7. Structural, luminescence and photophysical properties of novel trimetallic nanocomposite CeO2·ZnO·ZnAl2O4

    International Nuclear Information System (INIS)

    Subhan, Md Abdus; Ahmed, Tanzir; Sarker, Prosenjit; Pakkanen, Tuula T.; Suvanto, Mika; Horimoto, Masahiro; Nakata, Hiroyasu

    2014-01-01

    A novel trimetallic nanocomposite was prepared at a temperature of around 220 °C using co-precipitation of their carbonates from aqueous solutions of the metal nitrates. The morphology of the composite was investigated with scanning electron microscopy (SEM). The X-ray, FTIR and SEM/EDS analyses data indicate that as-synthesized composite which was heated at around 220 °C exists in a nanosized form consisting of crystalline Zn 6 Al 2 (OH) 16 CO 3 ·4H 2 O and CeO 2 . Annealing at temperatures between 400 and 920 °C converts the as-synthesized composite to CeO 2 ·ZnO·ZnAl 2 O 4 multi-metal oxide consisting of crystalline CeO 2 , ZnO and semicrystalline ZnAl 2 O 4 . Photoluminescence (PL) spectra of the as-synthesized sample showed emissions at 440 and 590 nm. PL spectra of CeO 2 ·ZnO·ZnAl 2 O 4 annealed at 920 °C was recorded and three sharp lines were observed at 627 nm (1.98 eV), 530 nm (2.34 eV) and 465 nm (2.67 eV) with broad peaks at 540 nm (2.3 eV) and 400 nm (3.1 eV). These sharp lines resemble to those of CeO 2 and the broad peaks originate from ZnO. The indirect band gap of the as-synthesized composite was found to be 2.44 eV. The luminescence lifetime at 4 K was measured to be 38 μs. -- Highlights: • A novel trimetallic nanocomposite, CeO 2 ·ZnO·ZnAl 2 O 4 has been synthesized and characterized. • At around 220 °C as-synthesized samples exist in crystalline Zn 6 Al 2 (OH) 16 CO 3 ·4H 2 O and CeO 2 . • Annealing at temperatures between 400 and 920 °C converts the composite to CeO 2 ·ZnO·ZnAl 2 O 4 . • The luminescence lifetime of the composite at 4 K was measured to be 38 μs. • PL of CeO 2 ·ZnO·ZnAl 2 O 4 shows three sharp peaks at 627 nm, 530 nm and 465 nm

  8. Degradation of some ceria electrolytes under hydrogen contact nearby anode in solid oxide fuel cells (SOFCs

    Directory of Open Access Journals (Sweden)

    Malta Luiz Fernando Brum

    2004-01-01

    Full Text Available This work is concerned with thermodynamic analysis of the stability of some ceria electrolytes under contact with hydrogen gas nearby anode in fuel cells. It was considered the following types of ceria-electrolytes: pure ceria, strontium-doped ceria, calcium-doped ceria and calcium-bismuth-doped ceria. The equilibrium Log (pH2O/pH2 vs. T diagrams were constructed for x = 0.1 and 0.01, where x is the fraction of initial ceria converted to Ce2O3 (proportional to the ratio between activities of Ce3+ and Ce4+ in the ceria electrolyte, which is proportional to the fraction of electronic conduction in the electrolyte at a given temperature. The predictions of the diagrams are as follows: (a Ce1.9Ca0.1Bi0.8O5.1 and Ce0.9Sr0.1O1.9 are less stable than pure ceria for the whole temperature range (from 0 to 1000 °C; (b Ce0.9Ca0.1O1.9 is more stable than pure ceria below about 650 °C for x = 0.1 and below about 400 °C for x = 0.01; (c at each temperature in the considered range the pressure ratio pH2O(g/pH2(g has to be higher than thermodynamically predicted in order to keep CeO2 stable in the electrolyte contacting hydrogen gas. Thermodynamic predictions are entirely capable of explaining experimental data published on the subject (irreversible cell degradation in the case of SrO-doped ceria; weight loss from doped-ceria electrolyte above 700 °C; oxygen gas release during sintering of ceria.

  9. Dehydrogenation of Surface-Oxidized Mixtures of 2LiBH4 + Al/Additives (TiF3 or CeO2

    Directory of Open Access Journals (Sweden)

    Juan Luis Carrillo-Bucio

    2017-11-01

    Full Text Available Research for suitable hydrogen storage materials is an important ongoing subject. LiBH4–Al mixtures could be attractive; however, several issues must be solved. Here, the dehydrogenation reactions of surface-oxidized 2LiBH4 + Al mixtures plus an additive (TiF3 or CeO2 at two different pressures are presented. The mixtures were produced by mechanical milling and handled under welding-grade argon. The dehydrogenation reactions were studied by means of temperature programmed desorption (TPD at 400 °C and at 3 or 5 bar initial hydrogen pressure. The milled and dehydrogenated materials were characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD, and Fourier transformed infrared spectroscopy (FT-IR The additives and the surface oxidation, promoted by the impurities in the welding-grade argon, induced a reduction in the dehydrogenation temperature and an increase in the reaction kinetics, as compared to pure (reported LiBH4. The dehydrogenation reactions were observed to take place in two main steps, with onsets at 100 °C and 200–300 °C. The maximum released hydrogen was 9.3 wt % in the 2LiBH4 + Al/TiF3 material, and 7.9 wt % in the 2LiBH4 + Al/CeO2 material. Formation of CeB6 after dehydrogenation of 2LiBH4 + Al/CeO2 was confirmed.

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

    Science.gov (United States)

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

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Xin Gui

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

  12. CEO performance appraisal: review and recommendations.

    Science.gov (United States)

    Newman, J F; Tyler, L; Dunbar, D M

    2001-01-01

    CEO performance appraisal (PA) is very valuable to an organization, but the chances of obtaining a PA of high quality decrease as executive responsibility increases. The realities of CEO PA are that it: (1) is inevitable; (2) is creative and complex; (3) involves politics; and (4) has a significant effect on the organization and the executive. PA is conducted for legal and social requirements, to enhance communication, to provide opportunities for improvement, and to relate performance to compensation. This article discusses several problems with chief executive officer (CEO) PA and the contemporary approaches that seek to improve it. Three fundamental areas for evaluation are identified: (1) organizational success; (2) areawide health status; and (3) professional role fulfillment. These provide an outline for successful healthcare PA. In addition to a discussion of the strategic considerations behind a successful CEO PA system, several recommendations are offered for the implementation of the annual evaluation process. The final goal of CEO PA is to link its results to CEO incentive compensation. It is strongly recommended that some portion of the CEO's salary directly hinge on his performance in two critical areas: organizational effectiveness and community health status.

  13. DEVELOPMENT OF DOPED NANOPOROUS CARBONS FOR HYDROGEN STORAGE

    Energy Technology Data Exchange (ETDEWEB)

    Lueking, Angela D.; Li, Qixiu; Badding, John V.; Fonseca, Dania; Gutierrez, Humerto; Sakti, Apurba; Adu, Kofi; Schimmel, Michael

    2010-03-31

    Hydrogen storage materials based on the hydrogen spillover mechanism onto metal-doped nanoporous carbons are studied, in an effort to develop materials that store appreciable hydrogen at ambient temperatures and moderate pressures. We demonstrate that oxidation of the carbon surface can significantly increase the hydrogen uptake of these materials, primarily at low pressure. Trace water present in the system plays a role in the development of active sites, and may further be used as a strategy to increase uptake. Increased surface density of oxygen groups led to a significant enhancement of hydrogen spillover at pressures less than 100 milibar. At 300K, the hydrogen uptake was up to 1.1 wt. % at 100 mbar and increased to 1.4 wt. % at 20 bar. However, only 0.4 wt% of this was desorbable via a pressure reduction at room temperature, and the high lowpressure hydrogen uptake was found only when trace water was present during pretreatment. Although far from DOE hydrogen storage targets, storage at ambient temperature has significant practical advantages oner cryogenic physical adsorbents. The role of trace water in surface modification has significant implications for reproducibility in the field. High-pressure in situ characterization of ideal carbon surfaces in hydrogen suggests re-hybridization is not likely under conditions of practical interest. Advanced characterization is used to probe carbon-hydrogen-metal interactions in a number of systems and new carbon materials have been developed.

  14. Synthesis of nanostructured mixed oxide CeO2-Mn2O3 and investigation of their sorption ability for arsenic, ammoniac, iron, manganese

    International Nuclear Information System (INIS)

    Luu Minh Dai; Dao Ngoc Nhiem; Duong Thi Lim

    2012-01-01

    The nanostrutured mixed oxide CeO 2 -Mn 2 O 3 have been synthesised at low temperature (350 o C) by the combustion of gel prepared from polyvinyl alcohol (PVA), Ce (NO 3 ) 4 and Mn(No 3 ) 3 , CeO 2 -Mn 2 O 3 characterizations were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET (Brunauce-Emmet-Teller) measurements. The phase of CeO 2 -Mn 2 O 3 , with large specific surface ares 65.3 m 2 /g was obtained at 350 o C for 2 hours. The nanostructured CeO 2 -Mn 2 O 3 has been investigated for removing iron, manganese, arsenic and ammoniac from water. The sorption characteristics of the nanostrutured CeO 2 -Mn 2 O 3 for AS(V), NH4 + , Fe(III), Mn(II) according to the langmuir isotherm. The sorption capacities of nanostrutured CeO 2 -Mn 2 O 3 are 57.10 mg As(V)g; 154.54 mg NH4 + /g; 72.97 mg Fe(III)/g; 60.27 Mn(II) / g. (author)

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

    International Nuclear Information System (INIS)

    Vanitha, M.; Keerthi; Cao, P.; Balasubramanian, N.

    2015-01-01

    Highlights: • Quasi spherical Ag and CeO 2 nanoparticles were decorated on rGO matrix. • The Ag/CeO 2 /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 CeO 2 /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 CeO 2 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 CeO 2 /rGO nanocomposite. This work endows a new route for building Ag/CeO 2 /rGO ternary nanocomposite which will have some impact on the exploitation of novel ternary electrode materials for supercapacitor applications

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

    International Nuclear Information System (INIS)

    Coll, M.; Palau, A.; Gonzalez-Rosillo, J.C.; Gazquez, J.; Obradors, X.; Puig, T.

    2014-01-01

    We present a low-temperature, < 300 °C, ex-situ integration of atomic layer deposition (ALD) ultrathin CeO 2 layers (3 to 5 unit cells) with chemical solution deposited La 0.7 Sr 0.3 MnO 3 (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 YBa 2 Cu 3 O 7 (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 CeO 2 patterns using an ozone-robust photoresist that will avoid the use of hazardous lithography processes directly on the device components. These bilayers, CeO 2 /LSMO and CeO 2 /YBCO, are foreseen to have special interest for resistive switching phenomena in resistive random-access memory. - Highlights: • Integration of atomic layer deposition (ALD) CeO 2 layers on functional complex oxides • Resistive switching is identified in CeO 2 /La 0.7 Sr 0.3 MnO 3 and CeO 2 /YBa 2 Cu 3 O 7 bilayers. • Study of the robustness of organic polymers for area-selective ALD • Combination of ALD and micro-contact printing to obtain 3D patterns of CeO 2

  17. Study of the growth of CeO2 nanoparticles onto titanate nanotubes

    Science.gov (United States)

    Marques, Thalles M. F.; Ferreira, Odair P.; da Costa, Jose A. P.; Fujisawa, Kazunori; Terrones, Mauricio; Viana, Bartolomeu C.

    2015-12-01

    We report the study of the growth of CeO2 nanoparticles on the external walls and Ce4+ intercalation within the titanate nanotubes. The materials were fully characterized by multiple techniques, such as: Raman spectroscopy, infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The ion exchange processes in the titanate nanotubes were carried out using different concentrations of Ce4+ in aqueous solution. Our results indicate that the growth of CeO2 nanoparticles grown mediated by the hydrolysis in the colloidal species of Ce and the attachment onto the titanate nanotubes happened and get it strongly anchored to the titanate nanotube surface by a simple electrostatic interaction between the nanoparticles and titanate nanotubes, which can explain the small size and even distribution of nanoparticles on titanate supports. It was demonstrated that it is possible to control the amount and size of CeO2 nanoparticles onto the nanotube surface, the species of the Ce ions intercalated between the layers of titanate nanotubes, and the materials could be tuned for using in specific catalysis in according with the amount of CeO2 nanoparticles, their oxygen vacancies/defects and the types of Ce species (Ce4+ or Ce3+) present into the nanotubes.

  18. Physical properties of nanostructured CeO2 thin films grown by SILAR method

    Science.gov (United States)

    Khan, Ishaque Ahmed; Belkhedkar, M. R.; Salodkar, R. V.; Ubale, A. U.

    2018-05-01

    Nanostructured CeO2 thin films have been deposited by Successive Ionic Layer Adsorption and Reaction (SILAR) method onto glass substrate using (CeNO3)3 6H2O and NaOH as cationic and anionic precursors respectively. The structural and morphological characterizations were carried out by means of X-ray diffraction, FTIR, FESEM and EDX studies. The highly resistive (1010 Ω cm) semiconducting CeO2 film exhibits 2.95 eV optical band gap.

  19. Preparation and corrosion resistance studies of nanometric sol-gel-based CeO2 film with a chromium-free pretreatment on AZ91D magnesium alloy

    International Nuclear Information System (INIS)

    Zhang Shiyan; Li Qing; Chen Bo; Yang Xiaokui

    2010-01-01

    Magnesium alloy, although valuable, is reactive and requires protection before it can be applied in many fields. In this study, a novel protective environmental-friendly gradient coating was performed on AZ91D magnesium alloy by non-chromate surface treatments, which consisted of phytic acid chemical conversion coating and the sol-gel-based CeO 2 thin film. The surface morphologies, microstructure and composition of the coatings were investigated by scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. The effects of the concentration, layers, temperature of heat treatment of CeO 2 sol on the anti-corrosion properties of the gradient coating for magnesium were also investigated. The results showed that the gradient coating was mainly composed of crystalline CeO 2 . According to the results of electrochemical tests, the corrosion resistance of AZ91D magnesium alloy was found to be greatly improved by means of this new environmental-friendly surface treatment.

  20. Hydrogen-boron complexes in heavily boron-doped silicon treated with high concentration of hydrogen atoms

    International Nuclear Information System (INIS)

    Fukata, N.; Fukuda, S.; Sato, S.; Ishioka, K.; Kitajima, M.; Hishita, S.; Murakami, K.

    2006-01-01

    The formation of hydrogen (H)-related complexes was investigated in boron (B)-doped Si treated with high concentration of H. The isotope shifts of H-related Raman peaks by replacement of H to deuterium and 1 B to 11 B clearly showed the formation of the B-H complexes in which H directly bonds to B in Si. The results of the resistivity measurements suggested that the B acceptors are passivated via the formation of the B-H complexes, as well as the well-known passivation center in B-doped Si, namely, H-B passivation center

  1. Photocatalytic degradation effect of malachite green and catalytic hydrogenation by UV-illuminated CeO2/CdO multilayered nanoplatelet arrays: Investigation of antifungal and antimicrobial activities.

    Science.gov (United States)

    Maria Magdalane, C; Kaviyarasu, K; Judith Vijaya, J; Jayakumar, C; Maaza, M; Jeyaraj, B

    2017-04-01

    CeO 2 /CdO multi-layered nanoplatelet arrays have been synthesized by sol-gel method at two different temperatures using Citrus limonum fruit extract and the effect of particle size on the photocatalytic performance is studied. The particle size and phases was analysed by X-ray diffraction pattern (XRD) which brought out the formation of cubic phase in the synthesized samples. Field Emission Scanning electron microscopy (FESEM) revealed the surface morphology and made up of cumulative form of platelet shaped arrays with an average size of 10nm. The elemental composition and the purity of the nanomaterials were confirmed by Energy Dispersive X-ray spectroscopy (EDX). CeO 2 /CdO multilayered binary metal oxide nanoplatelet arrays were formed which was further explored with Fourier transform infrared spectroscopy (FTIR), it reveals that the nanocomposites contain CeO and CdO bonds. Determination of the direct and indirect bandgap energy of the nanoplatelet arrays was carried out by UV-Vis-DRS studies. In MG degradation, both the hole (h + ) and hydroxyl radical (OH) played a major role than the superoxide radical (O 2 - ). Possible photo degradation mechanisms are proposed and discussed in this article. CeO 2 /CdO multi-layered nanoplatelet arrays showed antibacterial activity and among the tested ones, it showed better growth inhibition towards P. aeruginosa MTCC73. Thus, this greener synthetic procedure was a highly effective method due to low-cost, highly effective UV light responsive material for environmental safety. Copyright © 2017. Published by Elsevier B.V.

  2. A nano-engineered graphene/carbon nitride hybrid for photocatalytic hydrogen evolution

    Institute of Scientific and Technical Information of China (English)

    Xiaobo Li; Yao Zheng; Anthony F.Masters; Thomas Maschmeyer

    2016-01-01

    A metal-free photocatalytic hydrogen evolution system was successfully fabricated using heteroatom doped graphene materials as electron-transfer co-catalysts and carbon nitride as a semiconductor.The catalytic role of graphene is significantly dependent on the heteroatom dopant of the graphene,such as O,S,B,N doped/undoped graphene co-catalysts,and N-graphene shows the best catalytic hydrogen evolution rate.

  3. Properties of Ce-doped ITO films deposited on polymer substrate by DC magnetron sputtering

    International Nuclear Information System (INIS)

    Kang, Y.M.; Kwon, S.H.; Choi, J.H.; Cho, Y.J.; Song, P.K.

    2010-01-01

    Ce-doped indium tin oxide (ITO:Ce) films were deposited on flexible polyimide substrates by DC magnetron sputtering using ITO targets containing various CeO 2 contents (CeO 2 : 0, 0.5, 3.0, 4.0, 6.0 wt.%) at room temperature and post-annealed at 200 o C. The crystallinity of the ITO films decreased with increasing Ce content, and it led to a decrease in surface roughness. In addition, a relatively small change in resistance in dynamic stress mode was obtained for ITO:Ce films even after the annealing at high temperature (200 o C). The minimum resistivity of the amorphous ITO:Ce films was 3.96 x 10 -4 Ωcm, which was deposited using a 3.0 wt.% CeO 2 doped ITO target. The amorphous ITO:Ce films not only have comparable electrical properties to the polycrystalline films but also have a crystallization temperature > 200 o C. In addition, the amorphous ITO:Ce film showed stable mechanical properties in the bended state.

  4. Palladium on Nitrogen-Doped Mesoporous Carbon: A Bifunctional Catalyst for Formate-Based, Carbon-Neutral Hydrogen Storage.

    Science.gov (United States)

    Wang, Fanan; Xu, Jinming; Shao, Xianzhao; Su, Xiong; Huang, Yanqiang; Zhang, Tao

    2016-02-08

    The lack of safe, efficient, and economical hydrogen storage technologies is a hindrance to the realization of the hydrogen economy. Reported herein is a reversible formate-based carbon-neutral hydrogen storage system that is established over a novel catalyst comprising palladium nanoparticles supported on nitrogen-doped mesoporous carbon. The support was fabricated by a hard template method and nitridated under a flow of ammonia. Detailed analyses demonstrate that this bicarbonate/formate redox equilibrium is promoted by the cooperative role of the doped nitrogen functionalities and the well-dispersed, electron-enriched palladium nanoparticles. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Interchange core/shell assembly of diluted magnetic semiconductor CeO2 and ferromagnetic ferrite Fe3O4 for microwave absorption

    Directory of Open Access Journals (Sweden)

    Jiaheng Wang

    2017-05-01

    Full Text Available Core/shell-structured CeO2/Fe3O4 and Fe3O4/CeO2 nanocapsules are prepared by interchange assembly of diluted magnetic semiconductor CeO2 and ferromagnetic ferrite Fe3O4 as the core and the shell, and vice versa, using a facile two-step polar solvothermal method in order to utilize the room-temperature ferromagnetism and abundant O-vacancies in CeO2, the large natural resonance in Fe3O4, and the O-vacancy-enhanced interfacial polarization between CeO2 and Fe3O4 for new generation microwave absorbers. Comparing to Fe3O4/CeO2 nanocapsules, the CeO2/Fe3O4 nanocapsules show an improved real permittivity of 3–10% and an enhanced dielectric resonance of 1.5 times at 15.3 GHz due to the increased O-vacancy concentration in the CeO2 cores of larger grains as well as the O-vacancy-induced enhancement in interfacial polarization between the CeO2 cores and the Fe3O4 shells, respectively. Both nanocapsules exhibit relatively high permeability in the low-frequency S and C microwave bands as a result of the bi-magnetic core/shell combination of CeO2 and Fe3O4. The CeO2/Fe3O4 nanocapsules effectively enhance permittivity and permeability in the high-frequency Ku band with interfacial polarization and natural resonance at ∼15 GHz, thereby improving absorption with a large reflection loss of -28.9 dB at 15.3 GHz. Experimental and theoretical comparisons with CeO2 and Fe3O4 nanoparticles are also made.

  6. Development of sulfur- and nitrogen- free hydrogen odorants - An important step toward a safe hydrogen society -

    International Nuclear Information System (INIS)

    Nakamura, N.; Oshikawa, K.; Hasegawa, H.; Le Lay, M.; Iwase, M.; Braun, N.A.; Eilers, J.; Walz, A.; Vogt, M.; Herr, M.

    2006-01-01

    We have developed four sulfur-free and nitrogen-free odorants, which can be effectively used to odorize hydrogen. The odors were described through an olfactory test as alarming, strange, and chemical, giving sense of danger to the person who smells the odor. The safety of the material has been assessed and has been shown to be safe for usage. Testing the stability of odorized hydrogen in 80 MPa pressurized state, it was shown for a period of 13 weeks that the odorant retained its warning odor. Using the odorized hydrogen, FC duration test at 0.2 A/cm 2 was carried out for over 900 h without significant decrease in performance or the detectable degradation of MEA. The outlet of the fuel cell had no warning odor, suggesting deodorization on the catalyst. Use of activated charcoal as an adsorbent showed that the deodorization could be effectively carried out, ensuring that normal operation conditions are not perceived as a hydrogen leakage. (authors)

  7. Erbium-doped fiber ring laser with SMS modal interferometer for hydrogen sensing

    Science.gov (United States)

    Zhang, Ya-nan; Zhang, Lebin; Han, Bo; Peng, Huijie; Zhou, Tianmin; Lv, Ri-qing

    2018-06-01

    A hydrogen sensor based on erbium-doped fiber ring laser with modal interferometer is proposed. A single mode-multimode-single mode (SMS) modal interferometer structure coated with Pd/WO3 film is used as the sensing head, due to that it is easy to be fabricated and low cost. The sensing structure is inserted into an erbium-doped fiber ring laser in order to solve the problem of spectral confusion and improve the detection limit of the hydrogen sensor based on the SMS modal interferometer. The SMS sensing structure is acted as a fiber band-pass filter. When hydrogen concentration around the sensor is changed, it will induce the refractive index and strain variations of the Pd/WO3 film, and then shift the resonant spectrum of the SMS modal interferometer as well as the laser wavelength of the fiber ring laser. Therefore, the hydrogen concentration can be measured by monitoring the wavelength shift of the laser, which has high intensity and narrow full width half maximum. Experimental results demonstrate that the sensor has high sensitivity of 1.23 nm/%, low detection limit of 0.017%, good stability and excellent repeatability.

  8. The translocation and distribution of CeO2 nanoparticles in plants (Soybeans, Chili, Eggplant and Tomato)

    Science.gov (United States)

    Li, Teng; Dai, Yanhui

    2018-02-01

    Intensive production of CeO2 nanoparticles (NPs) would lead to their release into the environment. While their use in commercial goods is constantly increasing, location of NPs in plant is still poorly documented. In this study we determined the translocation of CeO2-NPs in four plants (Soybeans, Tomato, Chili and Eggplant) grown in natural conditions. The plants were digged out 1/4 roots into 2000 mg/L CeO2-NPs solution during the blossoming period. After being exposed for one month, the contents of Ce in plant tissues were measured by inductively coupled plasma mass spectrometry (ICP-MS). There was more Ce in the leaf of treated plants than in control plants. The contents of Ce in leaf tissues was different. This research offers vital information about the translocation and distribution of CeO2-NPs in higher plants.

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

    Directory of Open Access Journals (Sweden)

    Ruishu Shang

    2016-03-01

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

  10. Scintillation property of rare earth-free SnO-doped oxide glass

    OpenAIRE

    Masai, Hirokazu; Yanagida, Takayuki; Fujimoto, Yutaka; Koshimizu, Masanori; Yoko, Toshinobu

    2012-01-01

    The authors have demonstrated scintillation of rare earth (RE)-free Sn-doped oxide glass by excitation of ionizing radiation. It is notable that light emission is attained for RE-free transparent glass due to s[2]-sp transition of Sn[2+] centre and the emission correlates with the excitation band at 20 eV. We have also demonstrated that excitation band of emission centre can be tuned by the chemical composition of the host glass. The present result is valuable not only for design of RE-free i...

  11. Ultrathin nitrogen-doped graphitized carbon shell encapsulating CoRu bimetallic nanoparticles for enhanced electrocatalytic hydrogen evolution

    Science.gov (United States)

    Xu, You; Li, Yinghao; Yin, Shuli; Yu, Hongjie; Xue, Hairong; Li, Xiaonian; Wang, Hongjing; Wang, Liang

    2018-06-01

    Design of highly active and cost-effective electrocatalysts is very important for the generation of hydrogen by electrochemical water-splitting. Herein, we report the fabrication of ultrathin nitrogen-doped graphitized carbon shell encapsulating CoRu bimetallic nanoparticles (CoRu@NCs) and demonstrate their promising feasibility for efficiently catalyzing the hydrogen evolution reaction (HER) over a wide pH range. The resultant CoRu@NC nanohybrids possess an alloy–carbon core–shell structure with encapsulated low-ruthenium-content CoRu bimetallic alloy nanoparticles (10–30 nm) as the core and ultrathin nitrogen-doped graphitized carbon layers (2–6 layers) as the shell. Remarkably, the optimized catalyst (CoRu@NC-2 sample) with a Ru content as low as 2.04 wt% shows superior catalytic activity and excellent durability for HER in acidic, neutral, and alkaline conditions. This work offers a new method for the design and synthesis of non-platium-based electrocatalysts for HER in all-pH.

  12. Hydrogenation of furfural at the dynamic Cu surface of CuOCeO2/Al2O3 in vapor phase packed bed reactor

    Science.gov (United States)

    The hydrogenation of furfural to furfuryl alcohol over a CuOCeO2/'-Al2O3 catalyst in a flow reactor is reported. The catalyst was prepared by the wet impregnation of Cu onto a CeO2/'-Al2O3 precursor. The calcined catalyst was then treated with HNO3 to remove surface CuO resulting in a mixed CuCe oxi...

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

    International Nuclear Information System (INIS)

    Auffan, Melanie; Masion, Armand; Labille, Jerome; Diot, Marie-Ange; Liu, Wei; Olivi, Luca; Proux, Olivier; Ziarelli, Fabio; Chaurand, Perrine; Geantet, Christophe; Bottero, Jean-Yves; Rose, Jerome

    2014-01-01

    A multi-scale methodology was used to characterize the long-term behavior and chemical stability of a CeO 2 -based nanocomposite used as UV filter in wood stains. ATR-FTIR and 13 C 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 CeO 2 core observed by XANES (Ce L 3 -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 CeO 2 core over aging. • Potential implications in term of exposure and impact towards biological organisms. - The long-term aging of a CeO 2 nanocomposite lead to surface chemistry and structural changes in aquatic environments

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

    Science.gov (United States)

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

    This article reports the green fabrication of cerium oxide nanoparticles (CeO 2 NPs) using Olea europaea leaf extract and their applications as effective antimicrobial agents. O. europaea leaf extract functions as a chelating agent for reduction of cerium nitrate. The resulting CeO 2 NPs exhibit pure single-face cubic structure, which is examined by X-ray diffraction, with a uniform spherical shape and a mean size 24 nm observed through scanning electron microscopy and transmission electron microscopy. Ultraviolet-visible spectroscopy confirms the characteristic absorption peak of CeO 2 NPs at 315 nm. Fourier transform infrared spectroscopy reflects stretching frequencies at 459 cm -1 , showing utilization of natural components for the production of NPs. Thermal gravimetric analysis predicts the successful capping of CeO 2 NPs by bioactive molecules present in the plant extract. The antimicrobial studies show significant zone of inhibition against bacterial and fungal strains. The higher activities shown by the green synthesized NPs than the plant extract lead to the conclusion that they can be effectively used in biomedical application. Furthermore, reduction of cerium salt by plant extract will reduce environmental impact over chemical synthesis.

  15. Effects of CeO2 nanoparticles on sludge aggregation and the role of extracellular polymeric substances – Explanation based on extended DLVO

    International Nuclear Information System (INIS)

    You, Guoxiang; Hou, Jun; Wang, Peifang; Xu, Yi; Wang, Chao; Miao, Lingzhan; Lv, Bowen; Yang, Yangyang; Luo, Hao

    2016-01-01

    The extended DLVO (XDLVO) theory was applied to elucidate the potential effects of CeO 2 nanoparticles (CeO 2 NPs) on sludge aggregation and the role of extracellular polymeric substances (EPS). In this study, seven different concentrations of CeO 2 NPs were added to activated sludge cultured in sequencing batch reactors (SBRs) and compared with a control test that received no CeO 2 NPs. After exposure to 50 mg/L CeO 2 NPs, a negligible change (p>0.1) occurred in the sludge volume index (SVI), whereas the flocculability and aggregation of the sludge decreased by 18.8% and 11.2%, respectively, resulting in a high effluent turbidity. The XDLVO theory demonstrated that the adverse effects of the CeO 2 NPs on sludge aggregation were due to an enhanced barrier energy. Compared to the van der Waals energies (W A ) and the electric double layer (W R ), the acid-base interaction (W AB ) markedly changed for the various concentrations of CeO 2 NPs. The EPS played a decisive role in the sludge surface characteristics, as the removal of EPS equals to the negative effects induced by 5–10 mg/L CeO 2 NPs on the sludge flocculability and aggregation. The presence of CeO 2 NPs induced negative contributions to the tight boundary EPS (TB-EPS) and core bacteria while positive contributions to the total interaction energy of the loose boundary EPS (LB-EPS). - Highlights: • CeO 2 NPs adversely affected the flocculability and aggregation of the sludge. • The presence of CeO 2 NPs increased the energy barrier and led to a stable suspension. • The removal of EPS equals to the negative effects induced by 5–10 mg/L CeO 2 NPs. • The acid-base interaction was dominate and markedly changed for the CeO 2 NPs. • CeO 2 NPs induced negative contributions to the TB-EPS while positive to the LB-EPS.

  16. Free standing graphene oxide film for hydrogen peroxide sensing

    Science.gov (United States)

    Ranjan, Pranay; Balakrishnan, Jayakumar; Thakur, Ajay D.

    2018-05-01

    We report hydrogen peroxide (H2O2)sensing using free standing graphene oxide thin films prepared using a cost effective scalable approach. Such sensors may find application in pharmaceutical and food processing industries.

  17. Magnetic ordered mesoporous Fe3O4/CeO2 composites with synergy of adsorption and Fenton catalysis

    Science.gov (United States)

    Li, Keyan; Zhao, Yongqin; Song, Chunshan; Guo, Xinwen

    2017-12-01

    Magnetic Fe3O4/CeO2 composites with highly ordered mesoporous structure and large surface area were synthesized by impregnation-calcination method, and the mesoporous CeO2 as support was synthesized via the hard template approach. The composition, morphology and physicochemical properties of the materials were characterized by XRD, SEM, TEM, XPS, Raman spectra and N2 adsorption/desorption analysis. The mesoporous Fe3O4/CeO2 composite played a dual-function role as both adsorbent and Fenton-like catalyst for removal of organic dye. The methylene blue (MB) removal efficiency of mesoporous Fe3O4/CeO2 was much higher than that of irregular porous Fe3O4/CeO2. The superior adsorption ability of mesoporous materials was attributed to the abundant oxygen vacancies on the surface of CeO2, high surface area and ordered mesoporous channels. The good oxidative degradation resulted from high Ce3+ content and the synergistic effect between Fe and Ce. The mesoporous Fe3O4/CeO2 composite presented low metal leaching (iron 0.22 mg L-1 and cerium 0.63 mg L-1), which could be ascribed to the strong metal-support interactions for dispersion and stabilization of Fe species. In addition, the composite can be easily separated from reaction solution with an external magnetic field due to its magnetic property, which is important to its practical applications.

  18. Effects of hydrogen on Mn-doped GaN: A first principles calculation

    International Nuclear Information System (INIS)

    Wu, M.S.; Xu, B.; Liu, G.; Lei, X.L.; Ouyang, C.Y.

    2013-01-01

    First-principles calculations based on spin density functional theory are performed to study the effects of H on the structural, electronic and magnetic properties of the Mn-doped GaN dilute magnetic semiconductors. Our results show that the interstitial H atom prefers to bond with N atom rather than Mn atom, which means that H favors to form the N–H complex rather than Mn–H complex in the Mn-doped GaN. After introducing one H atom in the system, the total magnetic moment of the Mn-doped GaN increases by 25%, from 4.0μ B to 5.0μ B . The physics mechanism of the increase of magnetic moment after hydrogenation in Mn-doped GaN is discussed

  19. Phase Transformation and Lattice Parameter Changes of Non-trivalent Rare Earth-Doped YSZ as a Function of Temperature

    Science.gov (United States)

    Jiang, Shengli; Huang, Xiao; He, Zhang; Buyers, Andrew

    2018-05-01

    To examine the effect of doping/co-doping on high-temperature phase compositions of YSZ, stand-alone YSZ and CeO2 and Nb2O5 co-doped YSZ samples were prepared using mechanical alloy and high-temperature sintering. XRD analysis was performed on these samples from room temperature to 1100 °C. The results show that the structure for the co-doped samples tends to be thermally stable when the test temperature is higher than a critical value. Monoclinic phase was dominant in Nb2O5 co-doped YSZ at temperatures lower than 600 °C, while for the YSZ and CeO2 co-doped YSZ, cubic/tetragonal phase was dominant in the whole test temperature range. The lattice parameters for all the samples increase with increasing test temperature generally. The lattice parameters for the two non-trivalent rare earth oxides co-doped YSZ show that the lattice parameter a for the cubic phase of the Ce4+ co-doped YSZ is consistently greater than that of 7YSZ which is related to the presence of larger radius of Ce4+ in the matrix. The lattice parameters a, b, c for the monoclinic phase of Ce4+ co-doped YSZ are much closer to each other than that of the Nb5+ co-doped YSZ, indicating the former has better tendency to form cubic/tetragonal phase, which is desired for vast engineering applications.

  20. Perceptions of hospital CEOs about the effects of CEO turnover.

    Science.gov (United States)

    Khaliq, Amir A; Thompson, David M; Walston, Stephen L

    2006-01-01

    Empirical evidence is scarce on chief executive officer (CEO) turnover in U.S. hospitals, with potentially serious implications for many of these organizations. This study, based on a nationwide survey of CEOs at non-federal general surgical and medical community hospitals conducted in the spring of 2004, reports the perceptions of hospital CEOs regarding the circumstances and impact of CEO turnover on U.S. hospitals. In the opinion of the respondents, the impact includes competitors taking advantage of turnover by luring employees and physicians away from the target hospital, significantly increasing the likelihood of other senior executives leaving the hospital, and many of the important strategic activities being delayed or cancelled altogether. Interestingly, the perceptions of CEOs regarding the effects of turnover do not seem to differ regardless of voluntary or involuntary circumstances of turnover. However, there is a notable bias in emphasizing the perceived negative implications of respondents' own departures and allegedly positive effects of their predecessors' departures.

  1. Surface Reduced CeO2 Nanowires for Direct Conversion of CO2 and Methanol to Dimethyl Carbonate: Catalytic Performance and Role of Oxygen Vacancy

    Directory of Open Access Journals (Sweden)

    Zhongwei Fu

    2018-04-01

    Full Text Available Ultralong 1D CeO2 nanowires were synthesized via an advanced solvothermal method, surface reduced under H2 atmosphere, and first applied in direct synthesis of dimethyl carbonate (DMC from CO2 and CH3OH. The micro morphologies, physical parameters of nanowires were fully investigated by transmission electron microscopy (TEM, X-ray diffraction (XRD, N2 adsorption, X-ray photoelectron spectrum (XPS, and temperature-programmed desorption of ammonia/carbon dioxide (NH3-TPD/CO2-TPD. The effects of surface oxygen vacancy and acidic/alkaline sites on the catalytic activity was explored. After reduction, the acidic/alkaline sites of CeO2 nanowires can be dramatically improved and evidently raised the catalytic performance. CeO2 nanowires reduced at 500 °C (CeO2_NW_500 exhibited notably superior activity with DMC yield of 16.85 mmol gcat−1. Furthermore, kinetic insights of initial rate were carried out and the apparent activation energy barrier of CeO2_NW_500 catalyst was found to be 41.9 kJ/mol, much tiny than that of CeO2_NW catalyst (74.7 KJ/mol.

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

    Directory of Open Access Journals (Sweden)

    Chyuan Haur Kao

    2015-09-01

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

  3. The CEO's real legacy.

    Science.gov (United States)

    Freeman, Kenneth W

    2004-11-01

    The literature on CEO succession planning is nearly unanimous in its advice: Begin early, look first inside your company for exceptional talent, see that candidates gain experience in all aspects of the business, and help them develop the skills they will need in the top job. It all makes sense and sounds pretty straightforward. Nevertheless, the list of CEOs who last no more than a few years on the job continues to grow. Implicit in many, if not all, of these unceremonious departures is the absence of an effective CEO succession plan. The problem is, most boards simply don't want to talk about CEO succession: Why rock the boat when things are going well? Why risk offending the current CEO? Meanwhile, most CEOs can't imagine that anyone could adequately replace them. In this article, Kenneth W. Freeman, the retired CEO of Quest Diagnostics, discusses his own recent handoff experience (Surya N. Mohapatra became chief executive in May 2004) and offers his approach to succession planning. He says it falls squarely on the incumbent CEO to put ego aside and initiate and actively manage the process of selecting and grooming a successor. Aggressive succession planning is one of the best ways for CEOs to ensure the long-term health of the company, he says. Plus, thinking early and often about a successor will likely improve the chief executive's performance during his tenure. Freeman advocates the textbook rules for succession planning but adds to that list a few more that apply specifically to the incumbent CEO: Insist that the board become engaged in succession planning, look for a successor who is different from you, and make the successor's success your own. After all, Freeman argues, the CEO's true legacy is determined by what happens after he leaves the corner office.

  4. Effects of nitrogen content in monocrystalline nano-CeO2 on the degradation of dye in indoor lighting

    International Nuclear Information System (INIS)

    Sun, Dongfeng; Gu, Mingjie; Li, Ruixing; Yin, Shu; Song, Xiaozhen; Zhao, Bin; Li, Chengqiang; Li, Junping; Feng, Zhihai; Sato, Tsugio

    2013-01-01

    Azo dyes are an abundant class of synthetic dyes, however their complex structure makes them difficult to biologically degrade. We sought to degrade acid orange 7 (AO7) using nitrogen-doped nano-CeO 2 , which is a promising alternative photocatalyst to nitrogen-doped TiO 2 . Nitrogen-doped monocrystalline CeO 2 nanoparticles with various nitrogen contents were synthesized solvothermally at 120 o C from Ce(NO 3 ) 3 ·6H 2 O, triethanolamine, and ethanol. The CeO 2 monocrystals were between 7 and 8 nm in diameter. Nitrogen was shown to be incorporated into CeO 2 lattice from the results of the lattice parameter calculations, X-ray photoelectron spectroscopy analysis and elemental analysis. The degradation of AO7 in water was investigated using a domestic 10 W compact fluorescent lamp. The degradation efficiency of AO7 by monocrystalline CeO 2 increased with increasing nitrogen content, reaching 97.6% for the sample with a N:Ce molar ratio of 0.3.

  5. Improve electrochemical performance of CeO2 surface modification LiNi0.80Co0.15Al0.05O2 cathode material

    Science.gov (United States)

    Xia, Shubiao; Zhang, Yingjie; Dong, Peng; Zhang, Yannan

    2014-06-01

    Lithium ion battery cathode material LiNi0.8Co0.15Al0.05O2 cathode has successfully prepared by co-precipitation. CeO2 surface modification has improved LiNi0.80Co0.15Al0.05O2 electrochemical performance use sol-gel method and subsequent heat treatment at 600 °C for 5 h. Different to other conventional coating material, CeO2 coating layer can not only inhibit the reaction of the electrode and the electrolyte, but also can reduce the impedance of electron transfer due to its high conductivity, and inhibit the production of Ni2+ because of its high oxidation. The surface-modified and pristine LiNi0.80Co0.15Al0.05O2 powders are characterized by XRD, SEM, TEM, XPS, CV and DSC. When CeO2 coating is 0.02% (mole ratio), contrast to pristine NCA, the CeO2-coated NCA cathode exhibits no decrease in its initial specific capacity of 184 mAh g -1 (at 0.2 C) and excellent capacity retention (86% of its initial capacity at 1 C) between 2.75 and 4.3 V after 100 cycles. The results indicate that the CeO2 surface treatment should be an effective way to improve cycle properties due to CeO2 inhibit the electrodes and the electrolyte side effects.

  6. Hydrogen storage behaviors of Ni-doped graphene Oxide/MIL-101 hybrid composites.

    Science.gov (United States)

    Lee, Seul-Yi; Park, Soo-Jin

    2013-01-01

    In this work, Ni-doped graphene oxide/MIL-101 hybrid composites (Ni--GO/MIL) were prepared to investigate their hydrogen storage behaviors. Ni--GO/MIL was synthesized by adding Ni--GO in situ during the synthesis of MIL-101 using a hydrothermal process, which was conducted by conventional convection heating with Cr(III) ion as a metal center and telephthalic acid as organic ligands. The crystalline structures and morphologies were measured by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The specific surface area and micropore volume were investigated by N2/77 K adsorption isotherms using the Brunauer-Emmett-Teller (BET) method and Dubinin-Radushkevic (D-R) equation, respectively. The hydrogen storage capacity was investigated by BEL-HP at 77 K and 1 bar. The obtained results show that Ni--GO/MIL presents new directions for achieving novel hybrid materials with higher hydrogen storage capacity.

  7. Enhancement of room temperature ferromagnetic behavior of rf sputtered Ni-CeO_2 thin films

    International Nuclear Information System (INIS)

    Murugan, R.; Vijayaprasath, G.; Mahalingam, T.; Ravi, G.

    2016-01-01

    Highlights: • Ni-CeO_2 thin films deposited by using rf Magnetron sputtering with different concentrations of Ni. • Deposited thin films have single crystalline and uniform surface morphology. • Photoluminescence and micro-Raman spectra were interpreted for Ni-CeO_2 thin films. • XPS spectra confirmed Ni ions were present in the doped CeO_2 thin films. • Ni ions induced ferromagnetic behavior of Ni-CeO_2 films were confirmed through VSM. - Abstract: Ni-doped CeO_2 thin films were prepared under Ar"+ atmosphere on glass substrates using rf magnetron sputtering. To assess the properties of the prepared thin films, the influence of various amounts of Ni dopant on structural, morphological, optical, vibrational, compositional and magnetic properties of the CeO_2 films were studied by using X-Ray diffraction (XRD), atomic force microscope (AFM), photoluminescence (PL), micro-Raman, X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). XRD patterns for all the samples revealed the expected CeO_2 cubic fluorite-type structure and Ni ions were uniformly distributed in the samples. AFM images of the prepared samples indicate high dense, columnar structure with uniform distribution of CeO_2. Room-temperature photoluminescence (PL) and micro-Raman spectroscopic studies revealed an increase of oxygen vacancies with higher concentration of Ni in CeO_2. XPS results confirm the presence of Ni_2_p, O_1_s and Ce and depict that cerium is present as both Ce"4"+ and Ce"3"+ oxidation states in Ce_1_−_xNi_xO_2 (x = 15%) thin film. Field dependent magnetization measurements revealed a paramagnetic behavior for pure CeO_2, while a ferromagnetic behavior appeared when Ni is doped in CeO_2 films. Doping dependent magnetization measurements suggest that the observed ferromagnetism is due to the presence of metallic Ni clusters with nanometric size and broad size distribution.

  8. Photoemission properties of Eu-doped Zr1- x Ce x O2 (x = 0-0.2) nanoparticles prepared by hydrothermal method

    Science.gov (United States)

    Ozawa, Masakuni; Matsumoto, Masashi; Hattori, Masatomo

    2018-01-01

    Photoluminescent Eu-doped ZrO2 and Zr1- x Ce x O2 (x = 0-0.2) nanoparticles were prepared by a hydrothermal method. X-ray diffraction and Raman spectra indicated the formation of tetragonal crystals of ZrO2 and its solid solutions with a grain size of less than 10 nm diameter after heat treatment at 400 °C. The photoemission spectra of Zr1- x Ce x O2:Eu3+ nanocrystalline samples showed the typical emission of Eu3+ ions assigned to 5D0 → 7F1 (590 nm) and 5D0 → 7F2 (610 nm) transitions and additional emissions of 5D0 → 7F J with higher J of 3-5. Increasing the CeO2 concentration reduced the emission intensity, and the emission peak shift was affected by a local lattice distortion, i.e., CeO2 concentration. The present study provided fundamental knowledge that is expected to enable the fabrication of ZrO2-based nanocrystal phosphor materials and a measure for controlling the emission peak shift and intensity in oxide fluorite-based phosphor.

  9. Effect of MoS2 on hydrogenation storage properties of LiBH4

    International Nuclear Information System (INIS)

    Liang, Dan; Han, Shumin; Wang, Jiasheng; Zhang, Wei; Zhao, Xin; Zhao, Ziyang

    2014-01-01

    The hydrogen storage properties of LiBH 4 ball milled with 20 wt% MoS 2 have been investigated. It shows that the LiBH 4 doped with MoS 2 exhibits favorable hydrogenation and dehydrogenation properties in terms of decomposition temperature and hydriding/dehydriding reversibility. The sample with MoS 2 starts to release hydrogen at 230 °C and has a decrease of 80 °C in contrast with pristine LiBH 4 . Furthermore, for the second cycle, the LiBH 4 with MoS 2 maintains a reversible hydrogen storage capacity of about 8.0 wt% which is almost identical with the first cycle under 5 MPa at 550 °C. Analyzed by the XRD and the FTIR results, LiBH 4 can be regenerated after re-hydrogenation under a relatively mild condition by adding MoS 2 . The improvement of the hydrogenation and dehydrogenation properties mainly results from the formation of Li 2 S and MoB 2 during ball milling. -- Graphical abstract: Hydrogen absorption curves of LiBH 4 doped with MoS 2 for five cycles at 400 °C. Highlights: • The hydrogen absorption capacity is nearly the same for 5 cycles at 400 °C. • The sample with MoS 2 starts to release hydrogen at 230 °C. • The coexistence of MoB 2 and Li 2 S catalyzes the decomposition of LiBH 4

  10. Microstructure and high-temperature tribological properties of Si-doped hydrogenated diamond-like carbon films

    Science.gov (United States)

    Zhang, Teng Fei; Wan, Zhi Xin; Ding, Ji Cheng; Zhang, Shihong; Wang, Qi Min; Kim, Kwang Ho

    2018-03-01

    Si-doped DLC films have attracted great attention for use in tribological applications. However, their high-temperature tribological properties remain less investigated, especially in harsh oxidative working conditions. In this study, Si-doped hydrogenated DLC films with various Si content were synthesized and the effects of the addition of Si on the microstructural, mechanical and high-temperature tribological properties of the films were investigated. The results indicate that Si doping leads to an obvious increase in the sp3/sp2 ratio of DLC films, likely due to the silicon atoms preferentially substitute the sp2-hybridized carbon atoms and augment the number of sp3 sites. With Si doping, the mechanical properties, including hardness and adhesion strength, were improved, while the residual stress of the DLC films was reduced. The addition of Si leads to higher thermal and mechanical stability of DLC films because the Si atoms inhibit the graphitization of the films at an elevated temperature. Better high-temperature tribological properties of the Si-DLC films under oxidative conditions were observed, which can be attributed to the enhanced thermal stability and formation of a Si-containing lubricant layer on the surfaces of the wear tracks. The nano-wear resistance of the DLC films was also improved by Si doping.

  11. Evaluation of Pd Nanoparticle-Decorated CeO2-MWCNT Nanocomposite as an Electrocatalyst for Formic Acid Fuel Cells

    Science.gov (United States)

    Saleem, Junaid; Safdar Hossain, SK.; Al-Ahmed, Amir; Rahman, Ateequr; McKay, Gordon; Hossain, Mohammed M.

    2018-04-01

    In this work, CeO2-modified Pd/CeO2-carbon nanotube (CNT) electrocatalyst for the electro-oxidation of formic acid has been investigated. The support CNT was first modified with different amounts (5-30 wt.%) of CeO2 using a precipitation-deposition method. The electrocatalysts were developed by dispersing Pd on the CeO2-CNT supports using the borohydride reduction method. The synthesized electrocatalysts were analyzed for composition, morphology and electronic structure using x-ray diffraction (XRD), scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM/EDX), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) techniques. The formation of Pd nanoparticles on the CeO2-CNT support was confirmed using TEM. The activity of Pd/CeO2-CNT and of Pd-CNT samples upon oxidation of formic acid was evaluated by using carbon monoxide stripping voltammetry, cyclic voltammetry, and chronoamperometry. The addition of moderate amounts of cerium oxide (up to 10 wt.%) significantly improved the activity of Pd/CeO2-CNT compared to the unmodified Pd-CNT. Pd/10 wt.% CeO2-CNT showed a current density of 2 A mg-1, which is ten times higher than that of the unmodified Pd-CNT (0.2 A mg-1). Similarly, the power density obtained for Pd/10 wt.% CeO2-CNT in an air-breathing formic acid fuel cell was 6.8 mW/cm2 which is two times higher than Pd-CNT (3.2 mW/cm2), thus exhibiting the promotional effects of CeO2 to Pd/CeO2-CNT. A plausible justification for the improved catalytic performance and stability is provided in the light of the physical characterization results.

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

    International Nuclear Information System (INIS)

    Farooq, Muhammad; Ramli, Anita; Subbarao, Duvvuri

    2012-01-01

    The physical and chemical properties of a catalyst play a vital role in various industrial applications. Molybdenum catalysts supported on γ-Al 2 O 3 and γ-Al 2 O 3 -CeO 2 mixed oxides with varying loading of CeO 2 (5, 10, 15, 20 wt% with respect to γ-Al 2 O 3 ) were prepared by wet impregnation method. The physiochemical properties of these synthesized Mo catalysts were studied with various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX) and X-ray fluorescence spectrometer (XRF). The results showed that the addition of CeO 2 into the support affected the binding energies of the elements and reducibility of the metal oxides formed after calcination of catalyst samples due to the change in metal-support interaction. Further, the characterization techniques showed that the active metal was well dispersed on the surface of support material.

  13. Voluntary transition of the CEO: owner CEOs' sense of self before, during and after transition.

    Science.gov (United States)

    Byrnes, Randy T; Taylor, Scott N

    2015-01-01

    This inductive study explores how former business owner chief executive officers (CEOs) experience sense of self during voluntary separation and transition from their company. Our inquiry engaged 16 CEOs who ran companies ranging in size from 15 to 500 employees as they detailed their stories of walking away from roles as owner CEOs. We developed a coding scheme to analyze themes manifested in the narratives. We also analyzed the former CEOs' narratives using a stage and valence model depicting both the continuum of the separation experience and the characterization of each stage as a positive or negative state of being. The diverse yet synchronous stories resulted in three implications for current owner CEOs, professionals who advise CEOs, and future research on CEOs' careers. First, the CEOs often failed to allocate sufficient time and effort to prepare for an identity shift following the sale of their company or transition into retirement. Second, the CEOs experienced a diminished sense of self and dissatisfaction with the exit event. Third, the majority of the CEOs demonstrated an ability to work through the adverse and unanticipated states of being into a positive sense of self.

  14. Improving the Efficiency of DASC by Adding CeO2/CuO Hybrid Nanoparticles in Water

    Science.gov (United States)

    Midhun Mohan, V.; Sajeeb, A. M.

    Solar energy is the abundantly available source of renewable energy with least impact on environment. Direct absorption solar collector (DASC) is the commonly used device to absorb heat directly from sun and make use of it for different heating applications. In the past, many experiments have been done to increase the efficiency of DASC using nanofluids. In this paper, an examination of solar collector efficiency for hybrid CeO2/CuO-water (0.1% by volume) nanofluid under various flow rates and proportions of CeO2/CuO nanoparticles is investigated. The experiments were conducted at flow rates spanning from 20cc/min to 100cc/min and with CeO2/CuO nanoparticles proportions of 1:0, 1:0.5, 1:1, 0.5:1 and 0:1. The efficiency increases from 16.5% to 51.6% when the flow rate is increased from 20cc/min to 100cc/min for hybrid CeO2/CuO (1:1)-water nanofluid. The results also showed an increase in efficiency of 13.8%, 18.1%, 24.3%, 24.9% and 26.1% with hybrid combination of CeO2/CuO at ratios 1:0, 1:0.5, 1:1, 0.5:1 and 0:1, respectively, in comparison with water at a flow rate of 100cc/min.

  15. Electrochemically deposited Cu{sub 2}O cubic particles on boron doped diamond substrate as efficient photocathode for solar hydrogen generation

    Energy Technology Data Exchange (ETDEWEB)

    Mavrokefalos, Christos K. [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom); Hasan, Maksudul, E-mail: maksudul.hasan@chem.ox.ac.uk [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom); Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Rohan, James F. [Tyndall National Institute, University College Cork, Lee Maltings, Cork (Ireland); Compton, Richard G. [Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QZ, England (United Kingdom); Foord, John S., E-mail: john.foord@chem.ox.ac.uk [Department of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford, OX1 3TA, England (United Kingdom)

    2017-06-30

    Highlights: • Fabrication of low-cost photocathode by electrochemical method is described. • Boron-doped diamond is presented as catalyst support. • NiO nanoparticles on Cu{sub 2}O surface enhances photocurrent and electrode stability. • Synergy of metallic interaction between Cu and Ni leads to high efficiency. - Abstract: Herein, we report a novel photocathode for the water splitting reaction. The electrochemical deposition of Cu{sub 2}O particles on boron doped diamond (BDD) electrodes and the subsequent decoration with NiO nanoparticles by a dip coating method to act as co-catalyst for hydrogen evolution reaction is described. The morphology analysis by scanning electron microscope (SEM) revealed that Cu{sub 2}O particles are cubic and decorated sporadically with NiO nanoparticles. X-ray photoelectron spectroscopy (XPS) confirmed the electronic interaction at the interface between Cu{sub 2}O and NiO through a binding energy shift of the main Cu 2p peak. The photoelectrochemical (PEC) performance of NiO-Cu{sub 2}O/BDD showed a much higher current density (−0.33 mA/cm{sup 2}) and photoconversion efficiency (0.28%) compared to the unmodified Cu{sub 2}O/BDD electrode, which are only −0.12 mA/cm{sup 2} and 0.06%, respectively. The enhancement in PEC performance is attributable to the synergy of NiO as an electron conduction mediator leading to the enhanced charge separation and transfer to the reaction interface for hydrogen evolution as evidenced by electrochemical impedance spectroscopy (EIS) and charge carrier density calculation. Stability tests showed that the NiO nanoparticles loading content on Cu{sub 2}O surface is a crucial parameter in this regard.

  16. CEO Icon to GOP Hopeful: A Quantitative Analysis Exploring Politically Motivated Celebrity CEOs

    OpenAIRE

    Crighton, Lindsay

    2011-01-01

    This study examined the perceptions of celebrity CEOs potentially transitioning to political candidates. Using Carly Fiorina's campaign for Senator of California, this study identified how young voters perceive celebrity CEOs as politicians, their identification of celebrity CEOs, and the evaluations of CEOs and their companies. Results indicate a more favorable evaluation of Fiorina resulted in a more favorable reaction to Hewlett- Packard. Results also confirm the use of media messages to p...

  17. Temperature dependent dual hydrogen sensor response of Pd nanoparticle decorated Al doped ZnO surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, D.; Barman, P. B.; Hazra, S. K., E-mail: surajithazra@yahoo.co.in [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat, Solan, Himachal Pradesh-173234 (India); Dutta, D. [IC Design and Fabrication Centre, Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata-700032 (India); Kumar, M.; Som, T. [SUNAG Laboratory, Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India)

    2015-10-28

    Sputter deposited Al doped ZnO (AZO) thin films exhibit a dual hydrogen sensing response in the temperature range 40 °C–150 °C after surface modifications with palladium nanoparticles. The unmodified AZO films showed no response in hydrogen in the temperature range 40 °C–150 °C. The operational temperature windows on the low and high temperature sides have been estimated by isolating the semiconductor-to-metal transition temperature zone of the sensor device. The gas response pattern was modeled by considering various adsorption isotherms, which revealed the dominance of heterogeneous adsorption characteristics. The Arrhenius adsorption barrier showed dual variation with change in hydrogen gas concentration on either side of the semiconductor-to-metal transition. A detailed analysis of the hydrogen gas response pattern by considering the changes in nano palladium due to hydrogen adsorption, and semiconductor-to-metal transition of nanocrystalline Al doped ZnO layer due to temperature, along with material characterization studies by glancing incidence X-ray diffraction, atomic force microscopy, and transmission electron microscopy, are presented.

  18. Effect study of the support in nickel and cobalt catalysts for obtaining hydrogen from ethanol steam reforming

    International Nuclear Information System (INIS)

    Silva, Sirlane Gomes da

    2013-01-01

    A range of oxide-supported metal catalysts have been investigated for the steam reforming of ethanol for the production of hydrogen and subsequent application in fuel cells. The catalysts were synthesized by the co-precipitation and internal gelification methods using cobalt and nickel as active metals supported on aluminum, zirconium, lanthanum and cerium oxides. After prepared and calcined at 550 Cº the solids were fully characterized by different techniques such as X-rays diffraction(DRX), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy, nitrogen adsorption (B.E.T), temperature-programmed reduction in H2 (TPR-H2) and thermogravimetric analysis. The catalytic tests were performed in a monolithic quartz reactor and submitted to different thermodynamic conditions of steam reforming of ethanol at temperatures varying from 500º C to 800 ºC. The product gas streams from the reactor were analyzed by an on-line gas chromatograph. The cobalt/nickel catalyst supported on a ceria-lanthania mixture (Co 10% / Ni 5% - CeO 2 La 2 O 3 ) showed good catalytic performance in hydrogen selectivity reaching a concentration greater than 65%, when compared to other catalytic systems such as: Co 10% / Ni5% - CeO 2 ; Co 10% / Ni 5% - CeO 2 ZrO 2 ; Co 10% / Ni 5% - ZrO 2 ; Co 10% / Ni 5% - La 2 O 3 ; Co 10% / Ni 5% - CeO 2 La 2 O 3 /K 2% ; Co 10 % / Ni 5% - CeO 2 La 2 O 3 / Na 2% ; Ni 10% / Co 5% - CeO 2 La 2 O 3 ; Co-Al 2 O 3 e Co-Al 2 O 3 CeO 2 . (author)

  19. Determinants of CEO Turnover in Publicand Private Firms in Denmark - CEO and Firm Characteristics

    DEFF Research Database (Denmark)

    Sponholtz, Carina

    In this study we are the first to draw on longitudinal matched employer-employee data to study CEO turnover. Using this data we contribute tothe existing literature by examining the e¤ect of previously unstudied in-dividual characteristics on CEO turnover. Additionally, we are able toexamine CEO...... turnover. Finally, the inverse relationshipbetween firm performance and CEO turnover only exists in LLL firms(larger limited liability firms, both publicly and privately held), whereagency costs are assumed and found to be highest.In this study we are the first to draw on longitudinal matched employer-employee...... turnover across a variety of firm types that di¤er with re-spect to the corporate governance issues they face. Our simple methodol-ogy to define CEO turnover results in turnover rates similar to those foundpreviously. Our results indicate that CEO characteristics are an important factor in explaining CEO...

  20. Effect of CeO2 on TiC Morphology in Ni-Based Composite Coating

    Science.gov (United States)

    Cai, Yangchuan; Luo, Zhen; Chen, Yao

    2018-03-01

    The TiC/Ni composite coating with different content of CeO2 was fabricated on the Cr12MoV steel by laser cladding. The microstructure of cladding layers with the different content of CeO2 from the bottom to the surface is columnar crystal, cellular crystal, and equiaxed crystal. When the content of CeO2 is 0 %, the cladding layer has a coarse and nonuniform microstructure and TiC particles gathering in the cladding layer, and then the wear resistance was reduced. Appropriate rare-earth elements refined and homogenised the microstructure and enhanced the content of carbides, precipitated TiC particles and original TiC particles were spheroidised and refined, the wear resistance of the cladding layer was improved significantly. Excessive rare-earth elements polluted the grain boundaries and made the excessive burning loss of TiC particles that reduced the wear resistance of the cladding layer.

  1. Effects of palladium on the optical and hydrogen sensing characteristics of Pd-doped ZnO nanoparticles

    Directory of Open Access Journals (Sweden)

    Anh-Thu Thi Do

    2014-08-01

    Full Text Available The effect of palladium doping of zinc oxide nanoparticles on the photoluminescence (PL properties and hydrogen sensing characteristics of gas sensors is investigated. The PL intensity shows that the carrier dynamics coincides with the buildup of the Pd-related green emission. The comparison between the deep level emission and the gas sensing response characteristics allows us to suggest that the dissociation of hydrogen takes place at PdZn-vacancies ([Pd 2+(4d9]. The design of this sensor allows for a continuous monitoring in the range of 0–100% LEL H2 concentration with high sensitivity and selectivity.

  2. Environmentally friendly synthesis of CeO2 nanoparticles for the catalytic oxidation of benzyl alcohol to benzaldehyde and selective detection of nitrite.

    Science.gov (United States)

    Tamizhdurai, P; Sakthinathan, Subramanian; Chen, Shen-Ming; Shanthi, K; Sivasanker, S; Sangeetha, P

    2017-04-13

    Cerium oxide nanoparticles (CeO 2 NPs) are favorable in nanotechnology based on some remarkable properties. In this study, the crystalline CeO 2 NPs are successfully prepared by an efficient microwave combustion (MCM) and conventional route sol-gel (CRSGM) methods. The structural morphology of the as-prepared CeO 2 NPs was investigated by various spectroscopic and analytical techniques. Moreover, the XRD pattern confirmed the formation of CeO 2 NPs as a face centered cubic structure. The magnetometer studies indicated the low saturation magnetization (23.96 emu/g) of CeO 2 NPs for weak paramagnetic and high saturation magnetization (32.13 emu/g) of CeO 2 NPs for super paramagnetic. After that, the oxidation effect of benzyl alcohol was investigated which reveals good conversion and selectivity. Besides, the CeO 2 NPs modified glassy carbon electrode (GCE) used for the detection of nitrite with linear concentration range (0.02-1200 μM), low limit of detection (0.21 μM) and higher sensitivity (1.7238 μAμM -1 cm -2 ). However, the CeO 2 NPs modified electrode has the fast response, high sensitivity and good selectivity. In addition, the fabricated electrode is applied for the determination of nitrite in various water samples. Eventually, the CeO 2 NPs can be regarded as an effective way to enhance the catalytic activity towards the benzyl alcohol and nitrite.

  3. Hydrogenation Properties of TiFe Doped with Zirconium

    Directory of Open Access Journals (Sweden)

    Catherine Gosselin

    2015-11-01

    Full Text Available The goal of this study was to optimize the activation behaviour of hydrogen storage alloy TiFe. We found that the addition of a small amount of Zr in TiFe alloy greatly reduces the hydrogenation activation time. Two different procedural synthesis methods were applied: co-melt, where the TiFe was melted and afterward re-melted with the addition of Zr, and single-melt, where Ti, Fe and Zr were melted together in one single operation. The co-melted sample absorbed hydrogen at its maximum capacity in less than three hours without any pre-treatment. The single-melted alloy absorbed its maximum capacity in less than seven hours, also without pre-treatment. The reason for discrepancies between co-melt and single-melt alloys was found to be the different microstructure. The effect of air exposure was also investigated. We found that the air-exposed samples had the same maximum capacity as the argon protected samples but with a slightly longer incubation time, which is probably due to the presence of a dense surface oxide layer. Scanning electron microscopy revealed the presence of a rich Zr intergranular phase in the TiFe matrix, which is responsible for the enhanced hydrogenation properties of these Zr-doped TiFe alloys.

  4. One-step and low-temperature synthesis of iodine-doped graphene and its multifunctional applications for hydrogen evolution reaction and electrochemical sensing

    International Nuclear Information System (INIS)

    Chu, Ke; Wang, Fan; Zhao, Xiao-lin; Wei, Xiao-ping; Wang, Xin-wei; Tian, Ye

    2017-01-01

    Iodine (I) has emerged as a powerful heteroatom dopant for efficiently tailoring the electrocatalytic properties of graphene. However, the preparation methods of I-doped graphene (I-G) and its electrocatalysis applications remain largely unexplored. Herein, a one-step and low-temperature hydrothermal approach was developed for the successful synthesis of I-G with a high I-doping level (0.52 at.%). The resulting I-G was then applied as a metal-free catalyst for hydrogen evolution reaction (HER) and electrochemical sensing. It was shown that the I-G exhibited a dramatically enhanced HER activity compared to undoped graphene, attributed to the critical role of I-doping in offering large exposed active sites and high electron transfer capability. Furthermore, I-G also displayed attractive sensing performances for highly sensitive and selective detection of dopamine. These findings demonstrate that the hydrothermally synthesized I-G can be a promising electrocatalyst for multifunctional applications in water-splitting and electrochemical sensing.

  5. Enhancing hydrogen spillover and storage

    Science.gov (United States)

    Yang, Ralph T [Ann Arbor, MI; Li, Yingwel [Ann Arbor, MI; Lachawiec, Jr., Anthony J.

    2011-05-31

    Methods for enhancing hydrogen spillover and storage are disclosed. One embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the hydrogen receptor to ultrasonification as doping occurs. Another embodiment of the method includes doping a hydrogen receptor with metal particles, and exposing the doped hydrogen receptor to a plasma treatment.

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

    Science.gov (United States)

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

    2015-03-01

    Cerium oxide nanoparticles (CeO2 NPs) are used as diesel fuel additives to catalyze oxidation. Phenanthrene is a major component of diesel exhaust particles and one of the most common pollutants in the environment. This study aimed at determining the effect of CeO2 NPs on the toxicity of phenanthrene in Lufa 2.2 standard soil for the isopod Porcellionides pruinosus and the springtail Folsomia candida. Toxicity tests were performed in the presence of CeO2 concentrations of 10, 100 or 1000mg Ce/kg dry soil and compared with results in the absence of CeO2 NPs. CeO2 NPs had no adverse effects on isopod survival and growth or springtail survival and reproduction. For the isopods, LC50s for the effect of phenanthrene ranged from 110 to 143mg/kg dry soil, and EC50s from 17.6 to 31.6mg/kg dry soil. For the springtails, LC50s ranged between 61.5 and 88.3mg/kg dry soil and EC50s from 52.2 to 76.7mg/kg dry soil. From this study it may be concluded that CeO2 NPs have a low toxicity and do not affect toxicity of phenanthrene to isopods and springtails. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. Lithium decoration of three dimensional boron-doped graphene frameworks for high-capacity hydrogen storage

    International Nuclear Information System (INIS)

    Wang, Yunhui; Meng, Zhaoshun; Liu, Yuzhen; You, Dongsen; Wu, Kai; Lv, Jinchao; Wang, Xuezheng; Deng, Kaiming; Lu, Ruifeng; Rao, Dewei

    2015-01-01

    Based on density functional theory and the first principles molecular dynamics simulations, a three-dimensional B-doped graphene-interconnected framework has been constructed that shows good thermal stability even after metal loading. The average binding energy of adsorbed Li atoms on the proposed material (2.64 eV) is considerably larger than the cohesive energy per atom of bulk Li metal (1.60 eV). This value is ideal for atomically dispersed Li doping in experiments. From grand canonical Monte Carlo simulations, high hydrogen storage capacities of 5.9 wt% and 52.6 g/L in the Li-decorated material are attained at 298 K and 100 bars

  8. Engineering Pyrite-Type Bimetallic Ni-Doped CoS2 Nanoneedle Arrays over a Wide Compositional Range for Enhanced Oxygen and Hydrogen Electrocatalysis with Flexible Property

    Directory of Open Access Journals (Sweden)

    Guowei He

    2017-11-01

    Full Text Available The development of cheap and efficient catalytic electrodes is of great importance, to promote the sluggish overall water-splitting systems associated with the large-scale application of clean and renewable energy technologies. In this work, we report the controlled synthesis of pyrite-type bimetallic Ni-doped CoS2 nanoneedle (NN arrays supported on stainless steel (SS (designated as NixCo1−xS2 NN/SS, 0 ≤ x ≤ 1 and the related compositional influence on electrocatalytic efficiencies for the oxygen and hydrogen evolution reaction (OER/HER. Impressively, the Ni0.33Co0.67S2 NN/SS displays superior activity and faster kinetics for catalyzing OER (low overpotential of 286 mV at 50 mA cm−2; Tafel value of 55 mV dec−1 and HER (low overpotential of 350 mV at 30 mA cm−2; Tafel value of 76 mV dec−1 than those of counterparts with other Ni/Co ratios and also monometallic Ni- or Co-based sulfides, which is attributed to the optimized balance from the improved electron transfer capability, increased exposure of electrocatalytic active sites, and favorable dissipation of gaseous products over the nanoneedle surface. Furthermore, the conductive, flexible SS support and firmly attached in-situ integrated feature, result in the flexibility and remarkable long-term stability of as-prepared binder-free Ni0.33Co0.67S2 NN/SS electrode. These results demonstrate element-doping could be an efficient route at the atomic level to design new materials and further optimize the surface physicochemical properties for enhancing the overall electrochemical water splitting activity.

  9. Nanocrystalline Sr2CeO4 thin films grown on silicon by laser ablation

    International Nuclear Information System (INIS)

    Perea, Nestor; Hirata, G.A.

    2006-01-01

    Blue-white luminescent Sr 2 CeO 4 thin films were deposited by using pulsed laser ablation (λ = 248 nm wavelength) on 500 deg. C silicon (111) substrates under an oxygen pressure of 55 mTorr. High-resolution electron transmission microscopy, electron diffraction and X-ray diffraction analysis revealed that the films were composed of nanocrystalline Sr 2 CeO 4 grains of the order of 20-30 nm with a preferential orientation in the (130) crystallographic direction. The excitation and photoluminescence spectra measured on the films maintained the characteristic emission of bulk Sr 2 CeO 4 however, the emission peak appeared narrower and blue-shifted as compared to the luminescence spectrum of the target. The blue-shift and a preferential crystallographic orientation during the growth formation of the film is related to the nanocrystalline nature of the grains due to the quantum confinement behavior and surface energy minimization in nanostructured systems

  10. In situ DRIFTS investigation of NH3-SCR reaction over CeO2/zirconium phosphate catalyst

    Science.gov (United States)

    Zhang, Qiulin; Fan, Jie; Ning, Ping; Song, Zhongxian; Liu, Xin; Wang, Lanying; Wang, Jing; Wang, Huimin; Long, Kaixian

    2018-03-01

    A series of ceria modified zirconium phosphate catalysts were synthesized for selective catalytic reduction of NO with ammonia (NH3-SCR). Over 98% NOx conversion and 98% N2 selectivity were obtained by the CeO2/ZrP catalyst with 20 wt.% CeO2 loading at 250-425 °C. The interaction between CeO2 and zirconium phosphate enhanced the redox abilities and surface acidities of the catalysts, resulting in the improvement of NH3-SCR activity. The in situ DRIFTS results indicated that the NH3-SCR reaction over the catalysts followed both Eley-Rideal and Langmuir-Hinshelwood mechanisms. The amide (sbnd NH2) groups and the NH4+ bonded to Brønsted acid sites were the important intermediates of Eley-Rideal mechanism.

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

    Science.gov (United States)

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

    2014-07-01

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

  12. A facile synthesis for cauliflower like CeO2 catalysts from Ce-BTC precursor and their catalytic performance for CO oxidation

    Science.gov (United States)

    Zhang, Xiaodong; Hou, Fulin; Yang, Yang; Wang, Yuxin; Liu, Ning; Chen, Dan; Yang, Yiqiong

    2017-11-01

    The paper presents a novel and facile method for preparing cauliflowerlike CeO2 through direct decomposition of cerium based metal-organic framework (MOF) Ce-BTC (BTC = 1,3,5-benzenetricarboxylic acid) straw in air. Several analytical tools such as Scanning electron microscopy (SEM), X-ray diffraction (XRD), Thermogravimetric (TG), N2 adsorption-desorption, Temperature programmed reduction (TPR), Raman, X-ray photoelectron spectroscopic (XPS) and Photoluminescence (PL) have been used to characterize Ce-BTC and CeO2. The Ce-BTC calcined at 500 °C (CeO2-500) maintains the morphology of its template ;Ce-BTC; and forms a special cauliflower-like structure. XRD patterns showed that the catalyst has a perfect CeO2 crystal structure and has a smaller particle size. The prepared CeO2 cauliflowers exhibit excellent catalytic activities, long-term stability, and cycling stability for CO oxidation. The improved catalytic activities could be attributed to porous nanorods of CeO2 cauliflowers, which provide more active sites and oxygen vacancy for CO oxidation.

  13. Redox behavior of a low-doped Pr-CeO_2(111) surface. A DFT+U study

    International Nuclear Information System (INIS)

    Milberg, Brian; Juan, Alfredo; Irigoyen, Beatriz

    2017-01-01

    Highlights: • Pr doping facilitates oxygen donation due to the easy formation of Pr"3"+/Pr"4"+ and Ce"3"+/Ce"4"+ redox couples. • Pr doping also favors the formation of superoxide (O_2"−) radicals on surface O-holes. • CO can be oxidized by superoxide radical forming a CO_2 molecule floating on the surface. • CO can also interact on the (O_2"−)/Pr"3"+ interphase and forms weakly adsorbed carbonate-type intermediates. - Abstract: In this work, we investigated the redox behavior (donation and replenishing of oxygen) of a low praseodymium (Pr)-doped CeO_2(111) surface. We considered a 3.7 at.% Pr doping and performed density functional calculations using the GGA formalism with the ‘U’ correction on Ce(4f) and Pr(4f) orbitals. Our results indicate that Pr doping promotes oxygen donation by lowering the energy necessary to form surface anionic vacancies. When the Ce_0_._9_6_3Pr_0_._0_3_7O_2(111) surface donates one oxygen, the two excess electrons locate on Pr and Ce cations and reduce them to Pr"3"+ and Ce"3"+ ones. Praseodymium doping also favors the activation of O_2 molecule on surface O-holes, leading to formation of a superoxide (O_2"−) radical as well as to reoxidation of the Ce"3"+ cation to Ce"4"+ one. Additionally, we used the CO molecular adsorption for testing the reactivity of those superoxide species. The calculations expose the ability of these radicals to oxidize CO forming a CO_2 molecule floating on the surface. However, when the superoxide is in the immediate vicinity of Pr dopant a carbonate-type species is formed. Our theoretical results may help to gain insight into redox properties and improved catalytic performance of low-doped Pr-CeO_2 solids.

  14. Adsorption of hydrogen in Scandium/Titanium decorated nitrogen doped carbon nanotube

    Energy Technology Data Exchange (ETDEWEB)

    Mananghaya, Michael, E-mail: mikemananghaya@gmail.com [De La Salle University, 2401 Taft Ave, 0922, Manila (Philippines); DLSU STC Laguna Boulevard, LTI Spine Road Barangays Biñan and Malamig, Biñan City, Laguna (Philippines); DOST-ASTHRDP, PCIEERD, Gen. Santos Ave., Bicutan, Taguig City 1631 (Philippines); Belo, Lawrence Phoa; Beltran, Arnel [De La Salle University, 2401 Taft Ave, 0922, Manila (Philippines); DLSU STC Laguna Boulevard, LTI Spine Road Barangays Biñan and Malamig, Biñan City, Laguna (Philippines)

    2016-09-01

    Nitrogen doped Carbon Nanotube with divacancy (4ND-CN{sub x}NT) that is decorated with Scandium and Titanium as potential hydrogen storage medium using the pseudo potential density functional method was investigated. Highly localized states near the Fermi level, which are derived from the nitrogen defects, contribute to strong Sc and Ti bindings, which prevent metal aggregation and improve the material stability. A detailed Comparison of the Hydrogen adsorption capability with promising system-weight efficiency of Sc over Ti was elucidated when functionalized with 4ND-CN{sub x}NT. Finally, the (Sc/4ND){sub 10}-CN{sub x}CNT composite material has a thermodynamically favorable adsorption and consecutive adsorption energy for ideal reversible adsorption and desorption of hydrogen at room temperature such that it can hold at least 5.8 wt% hydrogen molecules at the LDA and GGA level. - Highlights: • Carbon Nanotube with divacancy (4ND-CN{sub x}NT) decorated with Sc and Ti. • Nitrogen defects, contribute to strong Sc and Ti bindings. • H{sub 2} and (Sc/4ND){sub 10}-CN{sub x}CNT has a favorable adsorption. • 5.8 wt% adsorption at the LDA and GGA level.

  15. Ag-doped TiO2 hollow microspheres with visible light response by template-free route for removal of tetracycline hydrochloride from aqueous solution

    Science.gov (United States)

    Zhang, Jian; Li, Xuanhua; Peng, Meiling; Tang, Yuanyuan; Ke, Anqi; Gan, Wei; Fu, Xucheng; Hao, Hequn

    2018-06-01

    In this study, Ag-doped TiO2 hollow microspheres were synthesized by a template-free route, and their photocatalytic performance and catalytic mechanism were investigated. The hollow microspheres were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy and UV–vis spectroscopy. Ag-doped hollow TiO2 microspheres exhibited excellent photocatalytic performance for tetracycline hydrochloride (TC) in water. TC degradation follows pseudo first-order kinetics, and hydroxyl radical (OH·) and holes (h+) were active substances in the photocatalytic reaction.

  16. Nanoscale Optimization and Statistical Modeling of Photoelectrochemical Water Splitting Efficiency of N-Doped TiO2 Nanotubes

    KAUST Repository

    Isimjan, Tayirjan T.; Trifkovic, Milana; Abdullahi, Inusa; Rohani, Sohrab M F; Ray, Ajay

    2014-01-01

    Highly ordered nitrogen-doped titanium dioxide (N-doped TiO2) nanotube array films with enhanced photo-electrochemical water splitting efficiency (PCE) for hydrogen generation were fabricated by electrochemical anodization, followed by annealing

  17. Time-Dependent Density Functional Theory Analysis of Triphenylamine-Functionalized Graphene Doped with Transition Metals for Photocatalytic Hydrogen Production.

    Science.gov (United States)

    Mota, Elder A V; Neto, Abel F G; Marques, Francisco C; Mota, Gunar V S; Martins, Marcelo G; Costa, Fabio L P; Borges, Rosivaldo S; Neto, Antonio M J C

    2018-07-01

    The electronic structures and optical properties of triphenylamine-functionalized graphene (G-TPA) doped with transition metals, using water as a solvent, were theoretically investigated to verify the efficiency of photocatalytic hydrogen production with the use of transition metals. This study was performed by Density Functional Theory and Time-dependent Density Functional Theory through Gaussian 09W software, adopting the B3LYP functional for all structures. The 6-31g(d) basis set was used for H, C and N atoms, and the LANL2DZ basis set for transition metals using the Effective Core Potentials method. Two approaches were adopted: (1) using single metallic dopants (Ni, Pd, Fe, Os and Pt) and (2) using combinations of Ni with the other dopants (NiPd, NiPt, NiFe and NiOs). The DOS spectra reveal an increase of accessible states in the valence shell, in addition to a gap decrease for all dopants. This doping also increases the absorption in the visible region of solar radiation where sunlight is most intense (400 nm to 700 nm), with additional absorption peaks. The results lead us to propose the G-TPA structures doped with Ni, Pd, Pt, NiPt or NiPd to be novel catalysts for the conversion of solar energy for photocatalytic hydrogen production, since they improve the absorption of solar energy in the range of interest for solar radiation; and act as reaction centers, reducing the required overpotential for hydrogen production from water.

  18. Photocatalytic performance of Cu-doped TiO2 nanofibers treated by the hydrothermal synthesis and air-thermal treatment

    Science.gov (United States)

    Wu, Ming-Chung; Wu, Po-Yeh; Lin, Ting-Han; Lin, Tz-Feng

    2018-02-01

    Series of transition metal-doped TiO2 (metal/TiO2) is prepared by combining the hydrothermal synthesis and air-thermal treatment without any reduction process. The selected transition metal precursors, including Ag, Au, Co, Cr, Cu, Fe, Ni, Pd, Pt, Y, and Zn, were individually doped into TiO2 nanofibers to evaluate the photocatalytic degradation activity and photocatalytic hydrogen generation. Consider the photocatalytic performance of these synthesized metal/TiO2 under UV-A irradiation, copper doped TiO2 nanofibers (Cu/TiO2 NFs) was chosen for further study due to its extraordinary reactivity. Systematical studies were spread to optimize the doping concentration and the calcination condition for much higher photocatalytic activity Cu/TiO2 NFs. In the photocatalytic degradation test, 0.5 mol%-Cu/TiO2 NFs calcined at 650 °C exhibits the highest activity, which is even higher than commercial TiO2-AEROXIDE® TiO2 P25 under UV-A irradiation. The synthesized 0.5 mol%-Cu/TiO2-650 NFs also have the capability in the photocatalytic hydrogen production. The hydrogen evolution rates are 200 μmol/g·h under UV-A irradiation and 280 μmol/g·h under UV-B irradiation. The density of state calculated by CASTEP for Cu/TiO2 indicates that Cu doping contributes to the states near valence band edge and narrows the band gap. The disclosed process in this study is industrial safe, convenient and cost-effective. We further produce a significant amount of TiO2-based catalysts without any hydrogen reduction treatment.

  19. Electrochemical properties of N-doped hydrogenated amorphous carbon films fabricated by plasma-enhanced chemical vapor deposition methods

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Yoriko; Furuta, Masahiro; Kuriyama, Koichi; Kuwabara, Ryosuke; Katsuki, Yukiko [Division of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 1677-1 Yoshida, Yamaguchi-shi, Yamaguchi 753-8512 (Japan); Kondo, Takeshi [Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510 (Japan); Fujishima, Akira [Kanagawa Advanced Science and Technology (KAST), 3-2-1, Sakato, Takatsu-ku, Kawasaki-shi, Kanagawa 213-0012 (Japan); Honda, Kensuke, E-mail: khonda@yamaguchi-u.ac.j [Division of Environmental Science and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 1677-1 Yoshida, Yamaguchi-shi, Yamaguchi 753-8512 (Japan)

    2011-01-01

    Nitrogen-doped hydrogenated amorphous carbon thin films (a-C:N:H, N-doped DLC) were synthesized with microwave-assisted plasma-enhanced chemical vapor deposition widely used for DLC coating such as the inner surface of PET bottles. The electrochemical properties of N-doped DLC surfaces that can be useful in the application as an electrochemical sensor were investigated. N-doped DLC was easily fabricated using the vapor of nitrogen contained hydrocarbon as carbon and nitrogen source. A N/C ratio of resulting N-doped DLC films was 0.08 and atomic ratio of sp{sup 3}/sp{sup 2}-bonded carbons was 25/75. The electrical resistivity and optical gap were 0.695 {Omega} cm and 0.38 eV, respectively. N-doped DLC thin film was found to be an ideal polarizable electrode material with physical stability and chemical inertness. The film has a wide working potential range over 3 V, low double-layer capacitance, and high resistance to electrochemically induced corrosion in strong acid media, which were the same level as those for boron-doped diamond (BDD). The charge transfer rates for the inorganic redox species, Fe{sup 2+/3+} and Fe(CN){sub 6}{sup 4-/3-} at N-doped DLC were sufficiently high. The redox reaction of Ce{sup 2+/3+} with standard potential higher than H{sub 2}O/O{sub 2} were observed due to the wider potential window. At N-doped DLC, the change of the kinetics of Fe(CN){sub 6}{sup 3-/4-} by surface oxidation is different from that at BDD. The rate of Fe(CN){sub 6}{sup 3-/4-} was not varied before and after oxidative treatment on N-doped DLC includes sp{sup 2} carbons, which indicates high durability of the electrochemical activity against surface oxidation.

  20. Investigation of charge compensation in indium-doped tin dioxide by hydrogen insertion via annealing under humid conditions

    International Nuclear Information System (INIS)

    Watanabe, Ken; Ohsawa, Takeo; Ross, Emily M.; Adachi, Yutaka; Haneda, Hajime; Sakaguchi, Isao; Takahashi, Ryosuke; Bierwagen, Oliver; White, Mark E.; Tsai, Min-Ying; Speck, James S.; Ohashi, Naoki

    2014-01-01

    The behavior of hydrogen (H) as an impurity in indium (In)-doped tin dioxide (SnO 2 ) was investigated by mass spectrometry analyses, with the aim of understanding the charge compensation mechanism in SnO 2 . The H-concentration of the In-doped SnO 2 films increased to (1–2) × 10 19  cm −3 by annealing in a humid atmosphere (WET annealing). The electron concentration in the films also increased after WET annealing but was two orders of magnitude less than their H-concentrations. A self-compensation mechanism, based on the assumption that H sits at substitutional sites, is proposed to explain the mismatch between the electron- and H-concentrations

  1. Theoretical perspective on the electronic, magnetic and optical properties of Zn-doped monolayer SnS{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Lili; Zhou, Wei; Liu, Yanyu; Yu, Dandan [Department of Applied Physics, Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Faculty of Science, Tianjin University, Tianjin 300072 (China); Liang, Yinghua [College of Chemical Engineering, North China University of Science and Technology, Tangshan 063009 (China); Wu, Ping, E-mail: pingwu@tju.edu.cn [Department of Applied Physics, Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Faculty of Science, Tianjin University, Tianjin 300072 (China)

    2016-12-15

    Highlights: • The Zn doping in monolayer SnS{sub 2} is energetically favored under S-rich condition. • The room temperature ferromagnetism can be realized in Zn-doped monolayer SnS{sub 2}. • The Zn doping enhances the effective utilization in the near-infrared light region. • The Zn doping could lead to the red shift of absorption edge in monolayer SnS{sub 2}. • The Zn-doped monolayer SnS{sub 2} is active for both the oxygen and hydrogen evolution. - Abstract: The electronic, magnetic and optical properties of Zn-doped monolayer SnS{sub 2} have been theoretically investigated with the density functional theory. Numerical results reveal that monolayer SnS{sub 2} can be easily synthesized by cleaving its bulk crystal. Besides, the Zn doping in monolayer SnS{sub 2} is energetically favored under the S-rich with respect to the Sn-rich condition. The doped system exhibits the magnetic ground states due to the formation of defect states above the Fermi level, which are introduced by the hybridization between S-3p states and a small amount of Sn-4d states. The room temperature ferromagnetism can also be realized in Zn-doped monolayer SnS{sub 2}. The injection of Zn can enhance the absorption efficiency of solar spectrum, especially in the near-infrared light region. Moreover, the Zn doping can enhance the photocatalytic activity for both the oxygen and hydrogen evolution reactions in the monolayer SnS{sub 2}.

  2. Near-infrared free carrier absorption in heavily doped silicon

    International Nuclear Information System (INIS)

    Baker-Finch, Simeon C.; McIntosh, Keith R.; Yan, Di; Fong, Kean Chern; Kho, Teng C.

    2014-01-01

    Free carrier absorption in heavily doped silicon can have a significant impact on devices operating in the infrared. In the near infrared, the free carrier absorption process can compete with band to band absorption processes, thereby reducing the number of available photons to optoelectronic devices such as solar cells. In this work, we fabricate 18 heavily doped regions by phosphorus and boron diffusion into planar polished silicon wafers; the simple sample structure facilitates accurate and precise measurement of the free carrier absorptance. We measure and model reflectance and transmittance dispersion to arrive at a parameterisation for the free carrier absorption coefficient that applies in the wavelength range between 1000 and 1500 nm, and the range of dopant densities between ∼10 18 and 3 × 10 20  cm −3 . Our measurements indicate that previously published parameterisations underestimate the free carrier absorptance in phosphorus diffusions. On the other hand, published parameterisations are generally consistent with our measurements and model for boron diffusions. Our new model is the first to be assigned uncertainty and is well-suited to routine device analysis

  3. A facile approach to fabrication of novel CeO2–TiO2 core–shell nanocomposite leads to excellent UV-shielding ability and lower catalytic activity

    International Nuclear Information System (INIS)

    Bahadur, Newaz Mohammed; Kurayama, Fumio; Furusawa, Takeshi; Sato, Masahide; Siddiquey, Iqbal Ahmed; Hossain, Md. Mufazzal; Suzuki, Noboru

    2013-01-01

    This study reports the development of a fast and facile route for the synthesis of novel CeO 2 –TiO 2 core–shell nanocomposite particles using microwave (MW) irradiation of the mixture of commercial CeO 2 , titanium-tetra-n-butoxide (TBOT) and aqueous ammonia. Solutions of TBOT in ethanol and ammonia were mixed with dispersed CeO 2 nanoparticles in ethanol, and the mixture was rapidly MW irradiated at 70 °C for 2 min. The resulting nanocomposite particles were characterized in terms of phase, shell thickness, composition, surface charge, morphology, and chemical state of the elements by XRD, TEM, XPS, SEM, Zeta potential analyzer, XRF, and FT-IR. Conventional methods of the synthesis of CeO 2 –TiO 2 nanocomposite require a long time, and TiO 2 is rarely found as a coated material. In contrast, the MW method was able to synthesize CeO 2 –TiO 2 core–shell nanocompsite particles within a very short time. CeO 2 –TiO 2 nanocomposite particles were fairly unaggregated with an average titania layer thickness of 2–5 nm. The obtained nanocomposites retained the crystalline cubic phase of CeO 2 , and the phase of coated TiO 2 was amorphous. The catalytic activities of uncoated and TiO 2 -coated CeO 2 nanoparticles for the oxidation of organic compounds were evaluated by the degradation study of methylene blue in air atmosphere at 403 K. The enhanced UV-shielding ability and visible transparency of the nanocomposite obtained by UV visible spectroscopic measurements suggested that the core–shell material has novel characteristics for using as a sunscreen material.

  4. Ending the CEO succession crisis.

    Science.gov (United States)

    Charan, Ram

    2005-02-01

    The CEO succession process is broken. Many companies have no meaningful succession plans, and few of the ones that do are happy with them. CEO tenure is shrinking; in fact, two out of five CEOs fail in their first 18 months. It isn't just that more CEOs are being replaced; it's that they're being replaced badly. The problems extend to every aspect of CEO succession: internal development programs, board supervision, and outside recruitment. While many organizations do a decent job of nurturing middle managers, few have set up the comprehensive programs needed to find the half-dozen true CEO candidates out of the thousands of leaders in their midst. Even more damaging is the failure of boards to devote enough attention to succession. Search committee members often have no experience hiring CEOs; lacking guidance, they supply either the narrowest or the most general of requirements and then fail to vet eitherthe candidates or the recruiters. The result is that too often new CEOs are plucked from the well-worn Rolodexes of a remarkably small number of recruiters. These candidates may be strong in charisma but may lack critical skills or otherwise be a bad fit with the company. The resulting high turnover is particularly damaging, since outside CEOs often bring in their own teams, can cause the company to lose focus, and are especially costly to be rid of. Drawing on over 35 years of experience with CEO succession, the author explains how companies can create a deep pool of internal candidates, how boards can consistently align strategy and leadership development, and how directors can get their money's worth from recruiters. Choosing a CEO should be not one decision but an amalgam ofthousands of decisions made by many people every day over years.

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

    Czech Academy of Sciences Publication Activity Database

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

    2015-01-01

    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: 0.229, year: 2015

  6. Chemisorption of a hydrogen adatom on metal doped α-Zr (0 0 0 1 surfaces in a vacuum and an implicit solvation environment

    Directory of Open Access Journals (Sweden)

    Cheng Zeng

    2017-12-01

    Full Text Available First-principles calculations have been carried out to investigate the adsorption of a hydrogen adatom on 24 metal doped α-Zr (0 0 0 1 surfaces in both a vacuum and an implicit solvation environment. The dopant are the elements in the 4th and 5th periods in the periodic table. Doping elements at the tail of the 4th and 5th periods can significantly reduce the hydrogen pickup in a vacuum environment. A weighted d-band center theory is used to analyze the doping effect. On the other hand, the hydrogen adsorption energies in water are relatively lower for all doped slabs and the surface adsorption of hydrogen adatom is stronger than that in a vacuum environment, especially, for the slabs with doping elements at the tail of the 4th and 5th periods. In the solvation environment, electronegativity difference affects the adsorption. Doping elements Ag, Ga, Ge, Sn, and Sb can reduce the hydrogen pickup in vacuum, while Ag and Cu can reduce the hydrogen pickup of the zirconium alloys in solvent environment.

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

    DEFF Research Database (Denmark)

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

    2016-01-01

    The effect on the thermal parameters of superconducting transition-edge bolometers produced on a single crystalline SrTiO3 (STO) substrate with and without a CeO2 buffer layer was investigated. Metal-organic deposition was used to deposit the 20-nm CeO2 buffer layer, whereas RF magnetron sputtering...

  8. Interactions of atomic hydrogen with amorphous SiO2

    Science.gov (United States)

    Yue, Yunliang; Wang, Jianwei; Zhang, Yuqi; Song, Yu; Zuo, Xu

    2018-03-01

    Dozens of models are investigated by the first-principles calculations to simulate the interactions of an atomic hydrogen with a defect-free random network of amorphous SiO2 (a-SiO2) and oxygen vacancies. A wide variety of stable configurations are discovered due to the disorder of a-SiO2, and their structures, charges, magnetic moments, spin densities, and density of states are calculated. The atomic hydrogen interacts with the defect-free a-SiO2 in positively or negatively charged state, and produces the structures absent in crystalline SiO2. It passivates the neutral oxygen vacancies and generates two neutral hydrogenated E‧ centers with different Si dangling bond projections. Electron spin resonance parameters, including Fermi contacts, and g-tensors, are calculated for these centers. The atomic hydrogen interacts with the positive oxygen vacancies in dimer configuration, and generate four different positive hydrogenated defects, two of which are puckered like the Eγ‧ centers. This research helps to understand the interactions between an atomic hydrogen, and defect-free a-SiO2 and oxygen vacancies, which may generate the hydrogen-complexed defects that play a key role in the degeneration of silicon/silica-based microelectronic devices.

  9. Production of Catalyst-Free Hyperpolarised Ethanol Aqueous Solution via Heterogeneous Hydrogenation with Parahydrogen

    Science.gov (United States)

    Salnikov, Oleg G.; Kovtunov, Kirill V.; Koptyug, Igor V.

    2015-09-01

    An experimental approach for the production of catalyst-free hyperpolarised ethanol solution in water via heterogeneous hydrogenation of vinyl acetate with parahydrogen and the subsequent hydrolysis of ethyl acetate was demonstrated. For an efficient hydrogenation, liquid vinyl acetate was transferred to the gas phase by parahydrogen bubbling and almost completely converted to ethyl acetate with Rh/TiO2 catalyst. Subsequent dissolution of ethyl acetate gas in water containing OH- ions led to the formation of catalyst- and organic solvent-free hyperpolarised ethanol and sodium acetate. These results represent the first demonstration of catalyst- and organic solvent-free hyperpolarised ethanol production achieved by heterogeneous hydrogenation of vinyl acetate vapour with parahydrogen and the subsequent ethyl acetate hydrolysis.

  10. Studies on the separation of hydrogen isotopes and spin isomers by gas chromatography

    International Nuclear Information System (INIS)

    Pushpa, K.K.; Annaji Rao, K.

    2000-08-01

    Separation and analysis of mixture of hydrogen isotopes has gained considerable importance because of various applications needing different isotopes in lasers, nuclear reactions and tracer or labelled compounds. In the literature gas chromatographic methods are reported using columns packed with partly dehydrated or thoroughly dehydrated alumina/molecular sieve stationary phase at 77 deg K with helium, neon and even hydrogen or deuterium as carrier gas. In the present study an attempt is made to compare the chromatographic behaviour of these two stationary phases using virgin and Fe doped form in partly dehydrated and thoroughly dehydrated state, using helium, neon, hydrogen and deuterium as carrier gas. The results of this study show that helium or neon carrier gas behave similarly broad peaks with some tailing. Sharp symmetric peaks are obtained with hydrogen or deuterium carrier gas. This is attributed to large hold up capacity for H 2 or D 2 at 77 deg K in these materials as compared to helium or neon. Spin isomers of H 2 or D 2 are separated on Fe free stationary phases, though ortho H 2 and HD are not resolved. Using a combination of Fe doped short column and plain alumina column, both maintained in dehydrated form, the effect of Fe doping on thermal equilibrium of ortho/para forms at 77 deg K is clearly demonstrated. (author)

  11. Raman scattering study of the anharmonic effects in CeO2-y nanocrystals

    Science.gov (United States)

    Popović, Z. V.; Dohčević-Mitrović, Z.; Cros, A.; Cantarero, A.

    2007-12-01

    We have studied the temperature dependence of the F2g Raman mode phonon frequency and broadening in CeO2-y nanocrystals. The phonon softening and phonon linewidth are calculated using a model which takes into account the three-and four-phonon anharmonic processes. A detailed comparison of the experimental data with theoretical calculations revealed the predominance of four-phonon anharmonic processes in the temperature dependence of the phonon energy and broadening of the nanocrystals. On the other hand, three-phonon processes dominate the temperature behavior of phonons in polycrystalline samples. The anti-Stokes/Stokes peak intensity ratio was also investigated and found to be smaller for nanosized CeO2 powders than in the bulk counterpart.

  12. Raman scattering study of the anharmonic effects in CeO2-y nanocrystals

    International Nuclear Information System (INIS)

    Popovic, Z V; Dohcevic-Mitrovic, Z; Cros, A; Cantarero, A

    2007-01-01

    We have studied the temperature dependence of the F 2g Raman mode phonon frequency and broadening in CeO 2-y nanocrystals. The phonon softening and phonon linewidth are calculated using a model which takes into account the three-and four-phonon anharmonic processes. A detailed comparison of the experimental data with theoretical calculations revealed the predominance of four-phonon anharmonic processes in the temperature dependence of the phonon energy and broadening of the nanocrystals. On the other hand, three-phonon processes dominate the temperature behavior of phonons in polycrystalline samples. The anti-Stokes/Stokes peak intensity ratio was also investigated and found to be smaller for nanosized CeO 2 powders than in the bulk counterpart

  13. Electrical and Plasmonic Properties of Ligand-Free Sn(4+) -Doped In2 O3 (ITO) Nanocrystals.

    Science.gov (United States)

    Jagadeeswararao, Metikoti; Pal, Somnath; Nag, Angshuman; Sarma, D D

    2016-03-03

    Sn(4+) -doped In2 O3 (ITO) is a benchmark transparent conducting oxide material. We prepared ligand-free but colloidal ITO (8 nm, 10 % Sn(4+) ) nanocrystals (NCs) by using a post-synthesis surface-modification reaction. (CH3 )3 OBF4 removes the native oleylamine ligand from NC surfaces to give ligand-free, positively charged NCs that form a colloidal dispersion in polar solvents. Both oleylamine-capped and ligand-free ITO NCs exhibit intense absorption peaks, due to localized surface plasmon resonance (LSPR) at around λ=1950 nm. Compared with oleylamine-capped NCs, the electrical resistivity of ligand-free ITO NCs is lower by an order of magnitude (≈35 mΩ cm(-1) ). Resistivity over a wide range of temperatures can be consistently described as a composite of metallic ITO grains embedded in an insulating matrix by using a simple equivalent circuit, which provides an insight into the conduction mechanism in these systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Room temperature redox reaction by oxide ion migration at carbon/Gd-doped CeO2 heterointerface probed by an in situ hard x-ray photoemission and soft x-ray absorption spectroscopies

    Directory of Open Access Journals (Sweden)

    Takashi Tsuchiya, Shogo Miyoshi, Yoshiyuki Yamashita, Hideki Yoshikawa, Kazuya Terabe, Keisuke Kobayashi and Shu Yamaguchi

    2013-01-01

    Full Text Available In situ hard x-ray photoemission spectroscopy (HX-PES and soft x-ray absorption spectroscopy (SX-XAS have been employed to investigate a local redox reaction at the carbon/Gd-doped CeO2 (GDC thin film heterointerface under applied dc bias. In HX-PES, Ce3d and O1s core levels show a parallel chemical shift as large as 3.2 eV, corresponding to the redox window where ionic conductivity is predominant. The window width is equal to the energy gap between donor and acceptor levels of the GDC electrolyte. The Ce M-edge SX-XAS spectra also show a considerable increase of Ce3+ satellite peak intensity, corresponding to electrochemical reduction by oxide ion migration. In addition to the reversible redox reaction, two distinct phenomena by the electrochemical transport of oxide ions are observed as an irreversible reduction of the entire oxide film by O2 evolution from the GDC film to the gas phase, as well as a vigorous precipitation of oxygen gas at the bottom electrode to lift off the GDC film. These in situ spectroscopic observations describe well the electrochemical polarization behavior of a metal/GDC/metal capacitor-like two-electrode cell at room temperature.

  15. Novel nanostructured CeO2 as efficient catalyst for energy and ...

    Indian Academy of Sciences (India)

    as counter ion shows lower-temperature oxidation of soot as compared to the mesoflower morphol- ... of CeO2 to Pt/C for ethanol electro-oxidation reaction in acidic media. Results show that ..... 3.1 Morphology dependent CO oxidation activity.

  16. Influence of nitrogen doping in sumanene framework toward hydrogen storage: A computational study.

    Science.gov (United States)

    Reisi-Vanani, Adel; Shamsali, Fatemeh

    2017-09-01

    Two conditions are important to obtain appropriate substances for hydrogen storage; high surface area and fitting binding energy (BE). Doping is a key strategy that improves BE. We investigated hydrogen adsorption onto twenty six nitrogen disubstituted isomers of sumanene (C 19 N 2 H 12 ) by MP2/6-311++G(d,p)//B3LYP/6-31+G(d) and M06-2X/6-31+G(d) levels of theory. Effect of nitrogen doping in different positions of sumanene was checked. To obtain better BE, basis set superposition error (BSSE) and zero point energy (ZPE) corrections were used. Anticipating of adsorption sites and extra details about adsorption process was done by molecular electrostatic potential (MEP) surfaces. Various types of density of state (DOS) diagrams such as total DOS (TDOS), projected DOS (PDOS) and overlap population DOS (OPDOS) and natural bond orbital (NBO) analysis were used to find better insight on the adsorption properties. In addition of temperature depending of the BE, HOMO-LUMO gap (HLG), dipole moment, reactivity and stability, bowl depth and natural population analysis (NPA) of the isomers were studied. A physisorption mechanism for adsorption was proposed and a trivial change was seen. Place of nitrogen atoms in sumanene frame causes to binding energy increases or decreases compared with pristine sumanene. The best and the worst isomers and category of isomers were suggested. Copyright © 2017 Elsevier Inc. All rights reserved.

  17. First-principles study of hydrogen dissociation and diffusion on transition metal-doped Mg(0 0 0 1) surfaces

    International Nuclear Information System (INIS)

    Wang, Zhiwen; Guo, Xinjun; Wu, Mingyi; Sun, Qiang; Jia, Yu

    2014-01-01

    First-principles calculations within the density functional theory (DFT) have been carried out to study hydrogen molecules dissociation and diffusion on clean and transition metals (TMs) doped Mg(0 0 0 1) surfaces following Pozzo et al. work. Firstly, the stability of Mg(0 0 0 1) surface doped with transition metals atom has been studied. The results showed that transition metals on the left of the table tend to substitute Mg in the second layer, while the other transition metals prefer to substitute Mg in the first layer. Secondly, we studied hydrogen molecules dissociation and diffusion on clean and Mg(0 0 0 1) surfaces which the transition metal atoms substituted both in the first layer and second layer. When transition metal atoms substitute in the first layer, the results agree with the Pozzo et al. result; when transition metal atoms substitute in the second layer, the results showed that the transition metals on the left of the periodic table impact on the dissociation barriers is less. However, for the transition metals (Mn, Fe, Co, Ni) on the right, there is a great impact on the barriers. The transition metals doped surfaces bind the dissociated H atoms loosely, making them easily diffused. The results further reveal that the Fe dopant on the Mg surface is the best choice for H 2 dissociation and hydrogen storage.

  18. Effects of hydrogen annealing on the room temperature ferromagnetism and optical properties of Cr-doped ZnO nanoparticles

    International Nuclear Information System (INIS)

    Tong Liuniu; Wang Yichao; He Xianmei; Han Huaibin; Xia Ailin; Hu Jinlian

    2012-01-01

    We explore the effects of hydrogen annealing on the room temperature ferromagnetism and optical properties of Cr-doped ZnO nanoparticles synthesized by the sol-gel method. X-ray diffraction and x-ray photoelectron spectroscopy data show evidence that Cr has been incorporated into the wurtzite ZnO lattice as Cr 2+ ions substituting for Zn 2+ ions without any detectable secondary phase in as-synthesized Zn 0.97 Cr 0.03 O nanopowders. The room temperature magnetization measurements reveal a large enhancement of saturation magnetization M s as well as an increase of coercivity of H 2 -annealed Zn 0.97 Cr 0.03 O:H samples. It is found that the field-cooled magnetization curves as a function of temperature from 40 to 400 K can be well fitted by a combination of a standard Bloch spin-wave model and Curie–Weiss law. The values of the fitted parameters of the ferromagnetic exchange interaction constant a and the Curie constant C of H 2 -annealed Zn 0.97 Cr 0.03 O:H nanoparticles are almost doubled upon H 2 -annealing. Photoluminescence measurements show evidence that the shallow donor defect or/and defect complexes such as hydrogen occupying an oxygen vacancy H o may play an important role in the origin of H 2 -annealing induced enhancement of ferromagnetism in Cr-H codoped ZnO nanoparticles. - Graphical Abstract: The H 2 -annealing induced enhancement of room temperature ferromagnetism in Cr-doped ZnO nanoparticles is observed. It is found that the field-cooled M-T curves can be well fitted by a combination of a standard Bloch spin-wave model and Curie–Weiss law. The values of the fitted parameters of the ferromagnetic exchange interaction constant a and the Curie constant C of H 2 -annealed Zn 0.97 Cr 0.03 O:H nanoparticles are almost doubled upon H 2 -annealing. The PL data show evidence that the hydrogen related shallow donor defect or/and defect complexes may be responsible for it. Display Omitted Highlights: ► The H 2 -annealing induced a large enhancement of

  19. Plasma-catalyst hybrid reactor with CeO2/γ-Al2O3 for benzene decomposition with synergetic effect and nano particle by-product reduction.

    Science.gov (United States)

    Mao, Lingai; Chen, Zhizong; Wu, Xinyue; Tang, Xiujuan; Yao, Shuiliang; Zhang, Xuming; Jiang, Boqiong; Han, Jingyi; Wu, Zuliang; Lu, Hao; Nozaki, Tomohiro

    2018-04-05

    A dielectric barrier discharge (DBD) catalyst hybrid reactor with CeO 2 /γ-Al 2 O 3 catalyst balls was investigated for benzene decomposition at atmospheric pressure and 30 °C. At an energy density of 37-40 J/L, benzene decomposition was as high as 92.5% when using the hybrid reactor with 5.0wt%CeO 2 /γ-Al 2 O 3 ; while it was 10%-20% when using a normal DBD reactor without a catalyst. Benzene decomposition using the hybrid reactor was almost the same as that using an O 3 catalyst reactor with the same CeO 2 /γ-Al 2 O 3 catalyst, indicating that O 3 plays a key role in the benzene decomposition. Fourier transform infrared spectroscopy analysis showed that O 3 adsorption on CeO 2 /γ-Al 2 O 3 promotes the production of adsorbed O 2 - and O 2 2‒ , which contribute benzene decomposition over heterogeneous catalysts. Nano particles as by-products (phenol and 1,4-benzoquinone) from benzene decomposition can be significantly reduced using the CeO 2 /γ-Al 2 O 3 catalyst. H 2 O inhibits benzene decomposition; however, it improves CO 2 selectivity. The deactivated CeO 2 /γ-Al 2 O 3 catalyst can be regenerated by performing discharges at 100 °C and 192-204 J/L. The decomposition mechanism of benzene over CeO 2 /γ-Al 2 O 3 catalyst was proposed. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Effects of hydrogen gas on properties of tin-doped indium oxide films deposited by radio frequency magnetron sputtering method

    International Nuclear Information System (INIS)

    Kim, Do-Geun; Lee, Sunghun; Lee, Gun-Hwan; Kwon, Sik-Chol

    2007-01-01

    Tin-doped indium oxide (ITO) films were deposited at ∼ 70 deg. C of substrate temperature by radio frequency magnetron sputtering method using an In 2 O 3 -10% SnO 2 target. The effect of hydrogen gas ratio [H 2 / (H 2 + Ar)] on the electrical, optical and mechanical properties was investigated. With increasing the amount of hydrogen gas, the resistivity of the samples showed the lowest value of 3.5 x 10 -4 Ω.cm at the range of 0.8-1.7% of hydrogen gas ratio, while the resistivity increases over than 2.5% of hydrogen gas ratio. Hall effect measurements explained that carrier concentration and its mobility are strongly related with the resistivity of ITO films. The supplement of hydrogen gas also reduced the residual stress of ITO films up to the stress level of 110 MPa. The surface roughness and the crystallinity of the samples were investigated by using atomic force microscopy and x-ray diffraction, respectively

  1. Does CEO compensation impact patient satisfaction?

    Science.gov (United States)

    Akingbola, Kunle; van den Berg, Herman A

    2015-01-01

    This study examines the relationship between CEO compensation and patient satisfaction in Ontario, Canada. The purpose of this paper is to determine what impact hospital CEO compensation has on hospital patient satisfaction. The analyses in this study were based on data of 261 CEO-hospital-year observations in a sample of 103 nonprofit hospitals. A number of linear regressions were conducted, with patient satisfaction as the dependent variable and CEO compensation as the independent variable of interest. Controlling variables included hospital size, type of hospital, and frequency of adverse clinical outcomes. CEO compensation does not significantly influence hospital patient satisfaction. Both patient satisfaction and CEO compensation appear to be driven primarily by hospital size. Patient satisfaction decreases, while CEO compensation increases, with the number of acute care beds in a hospital. In addition, CEO compensation does not even appear to moderate the influence of hospital size on patient satisfaction. There are several limitations to this study. First, observations of CEO-hospital-years in which annual nominal CEO compensation was below $100,000 were excluded, as they were not publicly available. Second, this research was limited to a three-year range. Third, this study related the compensation of individual CEOs to a measure of performance based on a multitude of patient satisfaction surveys. Finally, this research is restricted to not-for-profit hospitals in Ontario, Canada. The findings seem to suggest that hospital directors seeking to improve patient satisfaction may find their efforts frustrated if they focus exclusively on the hospital CEO. The findings highlight the need for further research on how CEOs may, through leading and supporting those hospital clinicians and staff that interact more closely with patients, indirectly enhance patient satisfaction. To the best of the authors' knowledge, no research has examined the relationship between

  2. High hole mobility p-type GaN with low residual hydrogen concentration prepared by pulsed sputtering

    Science.gov (United States)

    Arakawa, Yasuaki; Ueno, Kohei; Kobayashi, Atsushi; Ohta, Jitsuo; Fujioka, Hiroshi

    2016-08-01

    We have grown Mg-doped GaN films with low residual hydrogen concentration using a low-temperature pulsed sputtering deposition (PSD) process. The growth system is inherently hydrogen-free, allowing us to obtain high-purity Mg-doped GaN films with residual hydrogen concentrations below 5 × 1016 cm-3, which is the detection limit of secondary ion mass spectroscopy. In the Mg profile, no memory effect or serious dopant diffusion was detected. The as-deposited Mg-doped GaN films showed clear p-type conductivity at room temperature (RT) without thermal activation. The GaN film doped with a low concentration of Mg (7.9 × 1017 cm-3) deposited by PSD showed hole mobilities of 34 and 62 cm2 V-1 s-1 at RT and 175 K, respectively, which are as high as those of films grown by a state-of-the-art metal-organic chemical vapor deposition apparatus. These results indicate that PSD is a powerful tool for the fabrication of GaN-based vertical power devices.

  3. Oil-free centrifugal hydrogen compression technology demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Heshmat, Hooshang [Mohawk Innovative Technology Inc., Albany, NY (United States)

    2014-05-31

    One of the key elements in realizing a mature market for hydrogen vehicles is the deployment of a safe and efficient hydrogen production and delivery infrastructure on a scale that can compete economically with current fuels. The challenge, however, is that hydrogen, being the lightest and smallest of gases with a lower viscosity and density than natural gas, readily migrates through small spaces and is difficult to compresses efficiently. While efficient and cost effective compression technology is crucial to effective pipeline delivery of hydrogen, the compression methods used currently rely on oil lubricated positive displacement (PD) machines. PD compression technology is very costly, has poor reliability and durability, especially for components subjected to wear (e.g., valves, rider bands and piston rings) and contaminates hydrogen with lubricating fluid. Even so called “oil-free” machines use oil lubricants that migrate into and contaminate the gas path. Due to the poor reliability of PD compressors, current hydrogen producers often install duplicate units in order to maintain on-line times of 98-99%. Such machine redundancy adds substantially to system capital costs. As such, DOE deemed that low capital cost, reliable, efficient and oil-free advanced compressor technologies are needed. MiTi’s solution is a completely oil-free, multi-stage, high-speed, centrifugal compressor designed for flow capacity of 500,000 kg/day with a discharge pressure of 1200 psig. The design employs oil-free compliant foil bearings and seals to allow for very high operating speeds, totally contamination free operation, long life and reliability. This design meets the DOE’s performance targets and achieves an extremely aggressive, specific power metric of 0.48 kW-hr/kg and provides significant improvements in reliability/durability, energy efficiency, sealing and freedom from contamination. The multi-stage compressor system concept has been validated through full scale

  4. Preparation, characterization and luminescence of Sm~(3+) or Eu~(3+) doped Sr_2CeO_4 by a modified sol-gel method

    Institute of Scientific and Technical Information of China (English)

    张春祥; 史建设; 杨绪杰; 陆路德; 汪信

    2010-01-01

    Superfine Sr2CeO4:RE3+ (RE=Eu, Sm) phosphors were synthesized at relatively low temperature by a modified sol-gel method using nitrates as raw materials, ethylenediaminetetraacetic acid (EDTA) as complexing agent. Single phase phosphors could be obtained at calcination temperature above 800 °C and pH value higher than 6.4 of initial solution. The as-prepared powders consisted of uniform crotch-like grains. The preparation process was monitored by thermogravimetric and differential thermal analysis (TG-DTA) ...

  5. Effect of CeO2-coating on the electrochemical performances of LiFePO4/C cathode material

    International Nuclear Information System (INIS)

    Yao Jingwen; Wu Feng; Qiu Xinping; Li Ning; Su Yuefeng

    2011-01-01

    Highlights: → The first study the effect of CeO 2 coating on LiFePO 4 /C at low temperature. → Coated cathode shows improved capacities at high rates and low temperature. → CeO 2 -coating decreases electrode polarization and increases charge-transfer reaction activity. - Abstract: The effect of CeO 2 coating on LiFePO 4 /C cathode material has been investigated. The crystalline structure and morphology of the synthesized powders have been characterized by XRD, SEM, TEM and their electrochemical performances both at room temperature and low temperature are evaluated by CV, EIS and galvanostatic charge/discharge tests. It is found that, nano-CeO 2 particles distribute on the surface of LiFePO 4 without destroying the crystal structure of the bulk material. The CeO 2 -coated LiFePO 4 /C cathode material shows improved lithium insertion/extraction capacity and electrode kinetics, especially at high rates and low temperature. At -20 deg. C, the CeO 2 -coated material delivers discharge capacity of 99.7 mAh/g at 0.1C rate and the capacity retention of 98.6% is obtained after 30 cycles at various charge/discharge rates. The results indicate that the surface treatment should be an effective way to improve the comprehensive properties of the cathode materials for lithium ion batteries.

  6. Hydrogen storage enhanced in Li-doped carbon replica of zeolites: a possible route to achieve fuel cell demand.

    Science.gov (United States)

    Roussel, Thomas; Bichara, Christophe; Gubbins, Keith E; Pellenq, Roland J-M

    2009-05-07

    We first report the atomistic grand canonical Monte Carlo simulations of the synthesis of two realistic ordered microporous carbon replica in two siliceous forms of faujasite zeolite (cubic Y-FAU and hexagonal EMT). Atomistic simulations of hydrogen adsorption isotherms in these two carbon structures and their Li-doped composites were carried out to determine their storage capacities at 77 and 298 K. We found that these new forms of carbon solids and their Li-doped versions show very attractive hydrogen storage capacities at 77 and 298 K, respectively. However, for a filling pressure of 300 bars and at room temperature, bare carbons do not show advantageous performances compared to a classical gas cylinder despite of their crystalline micropore network. In comparison, Li-doped nanostructures provide reversible gravimetric and volumetric hydrogen storage capacities twice larger (3.75 wt % and 33.7 kg/m(3)). The extreme lattice stiffness of their skeleton will prevent them from collapsing under large external applied pressure, an interesting skill compared to bundle of carbon nanotubes, and metal organic frameworks (MOFs). These new ordered composites are thus very promising materials for hydrogen storage issues by contrast with MOFs.

  7. Are CEOs Different?

    DEFF Research Database (Denmark)

    Kaplan, Steven N.; Sørensen, Morten

    also predict future career progression. Non-CEO candidates who score higher on the four factors are subsequently more likely to become CEOs. The patterns are qualitatively similar for public, private equity and venture capital owned companies. We do not find economically large differences in the four...

  8. Investigation of charge compensation in indium-doped tin dioxide by hydrogen insertion via annealing under humid conditions

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Ken, E-mail: Watanabe.Ken@nims.go.jp [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); International Center for Young Scientists (ICYS-MANA), NIMS, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Ohsawa, Takeo; Ross, Emily M., E-mail: emross@hmc.edu; Adachi, Yutaka; Haneda, Hajime [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Sakaguchi, Isao; Takahashi, Ryosuke [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Department of Applied Science for Electronics and Materials, Kyushu University, 6-1 Kasuga-kouen Kasuga, Fukuoka 816-8580 (Japan); Bierwagen, Oliver, E-mail: bierwagen@pdi-berlin.de [Paul-Drude-Institute, Hausvogteiplatz 5-7, 10117 Berlin (Germany); Materials Department, University of California, Santa Barbara, California 93106 (United States); White, Mark E.; Tsai, Min-Ying; Speck, James S., E-mail: speck@ucsb.edu [Materials Department, University of California, Santa Barbara, California 93106 (United States); Ohashi, Naoki, E-mail: Ohashi.Naoki@nims.go.jp [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Department of Applied Science for Electronics and Materials, Kyushu University, 6-1 Kasuga-kouen Kasuga, Fukuoka 816-8580 (Japan); Materials Research Center for Element Strategy (MCES), Mailbox S2-13, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-0026 (Japan)

    2014-03-31

    The behavior of hydrogen (H) as an impurity in indium (In)-doped tin dioxide (SnO{sub 2}) was investigated by mass spectrometry analyses, with the aim of understanding the charge compensation mechanism in SnO{sub 2}. The H-concentration of the In-doped SnO{sub 2} films increased to (1–2) × 10{sup 19} cm{sup −3} by annealing in a humid atmosphere (WET annealing). The electron concentration in the films also increased after WET annealing but was two orders of magnitude less than their H-concentrations. A self-compensation mechanism, based on the assumption that H sits at substitutional sites, is proposed to explain the mismatch between the electron- and H-concentrations.

  9. Enhanced activity and stability of La-doped CeO2 monolithic catalysts for lean-oxygen methane combustion.

    Science.gov (United States)

    Zhu, Wenjun; Jin, Jianhui; Chen, Xiao; Li, Chuang; Wang, Tonghua; Tsang, Chi-Wing; Liang, Changhai

    2018-02-01

    Effective utilization of coal bed methane is very significant for energy utilization and environment protection. Catalytic combustion of methane is a promising way to eliminate trace amounts of oxygen in the coal bed methane and the key to this technology is the development of high-efficiency catalysts. Herein, we report a series of Ce 1-x La x O 2-δ (x = 0-0.8) monolithic catalysts for the catalytic combustion of methane, which are prepared by citric acid method. The structural characterization shows that the substitution of La enhance the oxygen vacancy concentration and reducibility of the supports and promote the migration of the surface oxygen, as a result improve the catalytic activity of CeO 2 . M-Ce 0.8 La 0.2 O 2-δ (monolithic catalyst, Ce 0.8 La 0.2 O 2-δ coated on cordierite honeycomb) exhibits outstanding activity for methane combustion, and the temperature for 10 and 90% methane conversion are 495 and 580 °C, respectively. Additionally, Ce 0.8 La 0.2 O 2-δ monolithic catalyst presents excellent stability at high temperature. These Ce 1-x La x O 2-δ monolithic materials with a small amount of La incorporation therefore show promises as highly efficient solid solution catalysts for lean-oxygen methane combustion. Graphical abstract ᅟ.

  10. Temperature dependence of gas sensing behaviour of TiO2 doped PANI composite thin films

    Science.gov (United States)

    Srivastava, Subodh; Sharma, S. S.; Sharma, Preetam; Sharma, Vinay; Rajura, Rajveer Singh; Singh, M.; Vijay, Y. K.

    2014-04-01

    In the present work we have reported the effect of temperature on the gas sensing properties of TiO2 doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO2 doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO2 doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

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

    International Nuclear Information System (INIS)

    Wen Jiuba; Yang Liusong; Zhu Limin; Zhang Jinmin; Li QuanAn

    2009-01-01

    A CeO 2 -modified aluminide coating was obtained by composite electro-deposition Ni and CeO 2 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 CeO 2 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

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

    International Nuclear Information System (INIS)

    Song, Xiu; Wang, Lei; Niinomi, Mitsuo; Nakai, Masaaki; Liu, Yang; Zhu, Miaoyong

    2014-01-01

    The new β-type Ti–29Nb–13Ta–4.6Zr (TNTZ) alloy containing trace amounts of CeO 2 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 CeO 2 ; the β grain size becomes a little larger when Ce content increases from 0.05% to 0.10%. This occurs because dispersed CeO 2 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 CeO 2 additions are maintained as low as those of TNTZ without CeO 2 , 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

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

    DEFF Research Database (Denmark)

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

    2009-01-01

    Developing multi-functional single buffer layer is one of the most important challenges for simplification of coated conductors configuration. Ladoped CeO2 films were prepared by chemical solution method. And surface morphology and texture quality of the La-doped CeO2 films were investigated...... method. It suggects that Ce0.9La0.1O2 film prepared by chemical solution route have a promising prospect for the simplification of coated conductors configuration....

  14. Catalytic activity of Pd-doped Cu nanoparticles for hydrogenation as a single-atom-alloy catalyst.

    Science.gov (United States)

    Cao, Xinrui; Fu, Qiang; Luo, Yi

    2014-05-14

    The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu55 nanoparticles have been systemically examined for H2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu55 shell can considerably reduce the activation energy of H2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.

  15. Do women CEOs face greater threat of shareholder activism compared to male CEOs? A role congruity perspective.

    Science.gov (United States)

    Gupta, Vishal K; Han, Seonghee; Mortal, Sandra C; Silveri, Sabatino Dino; Turban, Daniel B

    2018-02-01

    We examine the glass cliff proposition that female CEOs receive more scrutiny than male CEOs, by investigating whether CEO gender is related to threats from activist investors in public firms. Activist investors are extraorganizational stakeholders who, when dissatisfied with some aspect of the way the firm is being managed, seek to change the strategy or operations of the firm. Although some have argued that women will be viewed more favorably than men in top leadership positions (so-called "female leadership" advantage logic), we build on role congruity theory to hypothesize that female CEOs are significantly more likely than male CEOs to come under threat from activist investors. Results support our predictions, suggesting that female CEOs may face additional challenges not faced by male CEOs. Practical implications and directions for future research are discussed. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

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

    Directory of Open Access Journals (Sweden)

    Abdelkader Elaziouti

    2015-04-01

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

  17. Detection of Hydrogen Sulphide Gas Sensor Based Nanostructured Ba2CrMoO6 Thick Films

    Directory of Open Access Journals (Sweden)

    A. V. Kadu

    2007-11-01

    Full Text Available Nanocrystalline pure and doped Ba2CrMoO6, having an average crystallite size of 40 nm were synthesized by the sol-gel citrate method. Structural and gas-sensing characteristics were performed by using X-ray diffraction (XRD and sensitivity measurements. The gas sensing properties to reducing gases like Hydrogen sulphide (H2S, liquefied petroleum gas (LPG, carbon monoxide (CO and hydrogen gas (H2 were also discussed. The maximum sensitivity was obtained for 5 wt % Ni doped Ba2CrMoO6 at an operating temperature 250oC for H2S gas. Pd incorporation over 5 wt% Ni doped Ba2CrMoO6 improved the sensitivity, selectivity, response time, and reduced the operating temperature from 250 to 200oC of the sensor for H2S gas. This sensor also shows good satiability.

  18. Construction of g-C3N4/CeO2/ZnO ternary photocatalysts with enhanced photocatalytic performance

    Science.gov (United States)

    Yuan, Yuan; Huang, Gui-Fang; Hu, Wang-Yu; Xiong, Dan-Ni; Zhou, Bing-Xin; Chang, Shengli; Huang, Wei-Qing

    2017-07-01

    Promoting the spatial separation of photoexcited charge carriers is of paramount significance for photocatalysis. In this work, binary g-C3N4/CeO2 nanosheets are first prepared by pyrolysis and subsequent exfoliation method, then decorated with ZnO nanoparticles to construct g-C3N4/CeO2/ZnO ternary nanocomposites with multi-heterointerfaces. Notably, the type-II staggered band alignments existing between any two of the constituents, as well as the efficient three-level transfer of electron-holes in unique g-C3N4/CeO2/ZnO ternary composites, leads to the robust separation of photoexcited charge carriers, as verified by its photocurrent increased by 8 times under visible light irradiation. The resulting g-C3N4/CeO2/ZnO ternary nanocomposites unveil appreciably increased photocatalytic activity, faster than that of pure g-C3N4, ZnO and g-C3N4/CeO2 by a factor of 11, 4.6 and 3.7, respectively, and good stability toward methylene blue (MB) degradation. The remarkably enhanced photocatalytic activity of g-C3N4/CeO2/ZnO ternary heterostructures can be interpreted in terms of lots of active sites of nanosheet shapes and the efficient charge separation owing to the resulting type-II band alignment with more than one heterointerface and the efficient three-level electron-hole transfer. A plausible mechanism is also elucidated via active species trapping experiments with various scavengers, which indicating that the photogenerated holes and •OH radicals play a crucial role in photodegradation reaction under visible light irradiation. This work suggest that the rational design and construction of type II multi-heterostructures is powerful for developing highly efficient and reusable visible-light photocatalysts for environmental purification and energy conversion.

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

    Directory of Open Access Journals (Sweden)

    Maqbool Q

    2016-10-01

    Full Text Available Qaisar Maqbool,1 Mudassar Nazar,1 Sania Naz,2 Talib Hussain,3 Nyla Jabeen,4 Rizwan Kausar,5 Sadaf Anwaar,4 Fazal Abbas,6,7 Tariq Jan6 1Department of Biotechnology, Virtual University of Pakistan, Lahore, Pakistan; 2Department of Biotechnology, Quaid-i-Azam University, Islamabad, Pakistan; 3National Institute of Vacuum Science and Technology (NINVAST, Islamabad, Pakistan; 4Department of Biotechnology and Bioinformatics Lab., International Islamic University, Islamabad, Pakistan; 5Department of Chemistry, University of Sargodha, Sargodha, Pakistan; 6Department of Physics, International Islamic University, Islamabad, Pakistan; 7Interdisciplinary Research Organization, University of Chakwal (UOC, Chakwal, Pakistan Abstract: This article reports the green fabrication of cerium oxide nanoparticles (CeO2 NPs using Olea europaea leaf extract and their applications as effective antimicrobial agents. O. europaea leaf extract functions as a chelating agent for reduction of cerium nitrate. The resulting CeO2 NPs exhibit pure single-face cubic structure, which is examined by X-ray diffraction, with a uniform spherical shape and a mean size 24 nm observed through scanning electron microscopy and transmission electron microscopy. Ultraviolet-visible spectroscopy confirms the characteristic absorption peak of CeO2 NPs at 315 nm. Fourier transform infrared spectroscopy reflects stretching frequencies at 459 cm-1, showing utilization of natural components for the production of NPs. Thermal gravimetric analysis predicts the successful capping of CeO2 NPs by bioactive molecules present in the plant extract. The antimicrobial studies show significant zone of inhibition against bacterial and fungal strains. The higher activities shown by the green synthesized NPs than the plant extract lead to the conclusion that they can be effectively used in biomedical application. Furthermore, reduction of cerium salt by plant extract will reduce environmental impact over

  20. Synthesis by Sol-gel and characterization of catalysts Ag/Al2O3-CeO2

    International Nuclear Information System (INIS)

    Zayas, M.L.; Perez H, R.; Rubio, E.; Velasco, A.

    2004-01-01

    Aluminia, cerium and mixed oxides Al 2 O 3 -CeO 2 with different relationship Al/Ce (0.75, 0.50 and 0.25) were prepared by sol-gel and used as support for the Ag. The samples were characterized by XRD, DRIFT, TPR and adsorption of N 2 to temperature of liquid nitrogen. The surface area BET showed that the materials that contain aluminia present near values among them. XRD allowed to identify to the cerianite in the oxides that whose support contains cerium and to the α-aluminia. A mixture of phases was observed in the aluminia. Vibration bands attributed to the bond Al-O and Ce-O were observed by DRIFT in the catalytic materials. TPR showed differences in the reducibility of the Ag precursor in the indicative catalysts of a different interaction with the support. (Author)

  1. Reversible Interconversion between 2,5-Dimethylpyrazine and 2,5-Dimethylpiperazine by Iridium-Catalyzed Hydrogenation/Dehydrogenation for Efficient Hydrogen Storage.

    Science.gov (United States)

    Fujita, Ken-Ichi; Wada, Tomokatsu; Shiraishi, Takumi

    2017-08-28

    A new hydrogen storage system based on the hydrogenation and dehydrogenation of nitrogen heterocyclic compounds, employing a single iridium catalyst, has been developed. Efficient hydrogen storage using relatively small amounts of solvent compared with previous systems was achieved by this new system. Reversible transformations between 2,5-dimethylpyrazine and 2,5-dimethylpiperazine, accompanied by the uptake and release of three equivalents of hydrogen, could be repeated almost quantitatively at least four times without any loss of efficiency. Furthermore, hydrogen storage under solvent-free conditions was also accomplished. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Estudo microestrutural do catalisador Ni/gama-Al2O3: efeito da adição de CeO2 na reforma do metano com dióxido de carbono Microstructural study of Ni/gamma-Al2O3 catalyst: addition effects of CeO2 on carbon dioxide reforming of methane

    Directory of Open Access Journals (Sweden)

    Antoninho Valentini

    2003-10-01

    Full Text Available The carbon dioxide reforming of methane was carried out over nickel catalysts supported on the gamma-Al2O3/CeO2 system prepared by wet impregnation. With the increase of the CeO2 weight in the catalyst, a higher stability was observed in the catalytic activity, together with an excellent resistance to carbon deposition and a better Ni dispersion. The catalysts were characterized by means of surface area measurements, TPR, H2 chemisorption, XRD, SEM, EDX, XPS and TEM. An interaction between Ni and CeO2 was observed to the Ni/CeO2 sample after activation in a H2 atmosphere above 300 ºC. Such behavior has a significantly influence on the catalytic activity.

  3. Improved Cycling Stability of Cobalt-free Li-rich Oxides with a Stable Interface by Dual Doping

    International Nuclear Information System (INIS)

    Xie, Dongjiu; Li, Guangshe; Li, Qi; Fu, Chaochao; Fan, Jianming; Li, Liping

    2016-01-01

    Highlights: • Cobalt-free Na_xLi_1_._2_-_xMn_0_._6_-_xAl_xNi_0_._2O_2 oxides are prepared by a sol-gel method. • Dual-doping strengthens the covalence of Mn-O bonds and suppresses the side reactions between cathode and electrolyte. • Doped cathode has a capacity retention over 92.2% after 100 cycles at a high temperature of 55 °C. - Abstract: Li-rich cobalt-free oxides, popularly used as a cathode with high capacity in lithium ion battery, always suffer from poor cycling stability between 2.0 and 4.8 V vs Li"+/Li, especially when cycled at high temperatures (>50 °C). To overcome this issue, Na"+ and Al"3"+ dual-doped Na_xLi_1_._2_-_xMn_0_._6_-_xAl_xNi_0_._2O_2 Li-rich cathode is prepared in this study. It is shown that the side reactions between cathode and electrolyte during cycling are suppressed. The improved cycling performance is observed for all of the doped samples, among which the sample with x = 0.03 exhibits the highest capacity retention of 86.1% after 200 cycles between 2.0 and 4.8 V at 2C (1C = 200 mA g"−"1) and shows a remarkable cycling stability, even at a high temperature of 55 °C (a capacity retention of 92.2% after 100 cycles). Moreover, the average voltage of the sample with x = 0.03 after 100 cycles at 0.5C remains at 3.11 V with a retention ratio of 86.6%. This work provides a new strategy to develop Li-rich cobalt-free cathodes with excellent cycling stability for lithium ion batteries at high temperatures.

  4. Ceria-supported ruthenium nanoparticles as highly active and long-lived catalysts in hydrogen generation from the hydrolysis of ammonia borane.

    Science.gov (United States)

    Akbayrak, Serdar; Tonbul, Yalçın; Özkar, Saim

    2016-07-05

    Ruthenium(0) nanoparticles supported on ceria (Ru(0)/CeO2) were in situ generated from the reduction of ruthenium(iii) ions impregnated on ceria during the hydrolysis of ammonia borane. Ru(0)/CeO2 was isolated from the reaction solution by centrifugation and characterized by ICP-OES, BET, XRD, TEM, SEM-EDS and XPS techniques. All the results reveal that ruthenium(0) nanoparticles were successfully supported on ceria and the resulting Ru(0)/CeO2 is a highly active, reusable and long-lived catalyst for hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency value of 361 min(-1). The reusability tests reveal that Ru(0)/CeO2 is still active in the subsequent runs of hydrolysis of ammonia borane preserving 60% of the initial catalytic activity even after the fifth run. Ru(0)/CeO2 provides a superior catalytic lifetime (TTO = 135 100) in hydrogen generation from the hydrolysis of ammonia borane at 25.0 ± 0.1 °C before deactivation. The work reported here includes the formation kinetics of ruthenium(0) nanoparticles. The rate constants for the slow nucleation and autocatalytic surface growth of ruthenium(0) nanoparticles were obtained using hydrogen evolution as a reporter reaction. An evaluation of rate constants at various temperatures enabled the estimation of activation energies for both the reactions, Ea = 60 ± 7 kJ mol(-1) for the nucleation and Ea = 47 ± 2 kJ mol(-1) for the autocatalytic surface growth of ruthenium(0) nanoparticles, as well as the activation energy of Ea = 51 ± 2 kJ mol(-1) for the catalytic hydrolysis of ammonia borane.

  5. Reduction Mechanisms of Cu2+-Doped Na2O-Al2O3-SiO2 Glasses during Heating in H2 Gas.

    Science.gov (United States)

    Nogami, Masayuki; Quang, Vu Xuan; Ohki, Shinobu; Deguchi, Kenzo; Shimizu, Tadashi

    2018-01-25

    Controlling valence state of metal ions that are doped in materials has been widely applied for turning optical properties. Even though hydrogen has been proven effective to reduce metal ions because of its strong reducing capability, few comprehensive studies focus on practical applications because of the low diffusion rate of hydrogen in solids and the limited reaction near sample surfaces. Here, we investigated the reactions of hydrogen with Cu 2+ -doped Na 2 O-Al 2 O 3 -SiO 2 glass and found that a completely different reduction from results reported so far occurs, which is dominated by the Al/Na concentration ratio. For Al/Na glass body. For Al/Na > 1, on the other hand, the reduction of Cu 2+ ions occurred simultaneously with the formation of OH bonds, whereas the reduced Cu metal moved outward and formed a metallic film on glass surface. The NMR and Fourier transform infrared results indicated that the Cu 2+ ions were surrounded by Al 3+ ions that formed AlO 4 , distorted AlO 4 , and AlO 5 units. The diffused H 2 gas reacted with the Al-O - ···Cu + units, forming Al-OH and metallic Cu, the latter of which moved freely toward glass surface and in return enhanced H 2 diffusion.

  6. The possible role of cerium oxide (CeO 2 ) nanoparticles in ...

    African Journals Online (AJOL)

    Results showed that CeO2NPs resulted in partial neuroprotection against disturbances in motor performance. It also partially decreased apoptosis and oxidative stress in preventive group, while it failed to increase striatal dopamine level as compared to untreated rats. The present study verified some neuroprotective effects ...

  7. Are CEOs Different?

    DEFF Research Database (Denmark)

    Kaplan, Steven N.; Sørensen, Morten

    We use a dataset of over 2,600 executive assessments to study thirty individual characteristics ofcandidates for top executive positions – CEO, CFO, COO and others. We classify the thirtycandidate characteristics with four primary factors: general ability, execution vs. interpersonal,charisma vs....

  8. Nitrogen-doped fullerene as a potential catalyst for hydrogen fuel cells.

    Science.gov (United States)

    Gao, Feng; Zhao, Guang-Lin; Yang, Shizhong; Spivey, James J

    2013-03-06

    We examine the possibility of nitrogen-doped C60 fullerene (N-C60) as a cathode catalyst for hydrogen fuel cells. We use first-principles spin-polarized density functional theory calculations to simulate the electrocatalytic reactions on N-C60. The first-principles results show that an O2 molecule can be adsorbed and partially reduced on the N-C complex sites (Pauling sites) of N-C60 without any activation barrier. Through a direct pathway, the partially reduced O2 can further react with H(+) and additional electrons and complete the water formation reaction (WFR) with no activation energy barrier. In the indirect pathway, reduced O2 reacts with H(+) and additional electrons to form H2O molecules through a transition state (TS) with a small activation barrier (0.22-0.37 eV). From an intermediate state to a TS, H(+) can obtain a kinetic energy of ∼0.95-3.68 eV, due to the Coulomb electric interaction, and easily overcome the activation energy barrier during the WFR. The full catalytic reaction cycles can be completed energetically, and N-C60 fullerene recovers to its original structure for the next catalytic reaction cycle. N-C60 fullerene is a potential cathode catalyst for hydrogen fuel cells.

  9. CEO Education and Corporate Environmental Footprint

    DEFF Research Database (Denmark)

    Amore, Mario Daniele; Bennedsen, Morten; Larsen, Birthe

    We analyze the effect of CEO education on environmental decision-making. Using a unique sample of Danish firms from 1996 to 2012, we find that CEO education significantly improves firms’ energy efficiency. We derive causality using health shocks: the hospitalization of highly educated CEOs induces...... a drop in energy efficiency, whereas the hospitalization of less educated CEOs does not have any significant effect. Exploring the mechanisms at play, we show that our results are driven by the length rather than the field of education. CEO education improves corporate energy efficiency through personal...... environmental awareness: highly educated CEOs exhibit greater concerns for climate change, as measured by a survey of social preferences, and drive more environmentally-efficient cars. Taken together, our findings suggest that education shapes managerial styles giving rise to greater sustainability in corporate...

  10. WS2 as an Effective Noble-Metal Free Cocatalyst Modified TiSi2 for Enhanced Photocatalytic Hydrogen Evolution under Visible Light Irradiation

    Directory of Open Access Journals (Sweden)

    Dongmei Chu

    2016-09-01

    Full Text Available A noble-metal free photocatalyst consisting of WS2 and TiSi2 being used for hydrogen evolution under visible light irradiation, has been successfully prepared by in-situ formation of WS2 on the surface of TiSi2 in a thermal reaction. The obtained samples were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, energy dispersive X-ray spectrometry (EDX, transmission electron microscopy (TEM, and X-ray photoelectron spectroscopy (XPS. The results demonstrate that WS2 moiety has been successfully deposited on the surface of TiSi2 and some kind of chemical bonds, such as Ti-S-W and Si-S-W, might have formed on the interface of the TiSi2 and WS2 components. Optical and photoelectrochemical investigations reveal that WS2/TiSi2 composite possesses lower hydrogen evolution potential and enhanced photogenerated charge separation and transfer efficiency. Under 6 h of visible light (λ > 420 nm irradiation, the total amount of hydrogen evolved from the optimal WS2/TiSi2 catalyst is 596.4 μmol·g−1, which is around 1.5 times higher than that of pure TiSi2 under the same reaction conditions. This study shows a paradigm of developing the effective, scalable and inexpensive system for photocatalytic hydrogen generation.

  11. Bioactivity of Y2O3 and CeO2 doped SiO2-SrO-Na2O glass-ceramics.

    Science.gov (United States)

    Placek, L M; Keenan, T J; Wren, A W

    2016-08-01

    The bioactivity of yttrium and cerium are investigated when substituted for Sodium (Na) in a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramics (where x = 0.08 and MO = Y2O3 or CeO2). Bioactivity is monitored through pH and inductively coupled plasma-optical emission spectrometry where pH of simulated body fluid ranged from 7.5 to 7.6 and increased between 8.2 and 10.0 after 14-day incubation with the glass-ceramic disks. Calcium (Ca) and phosphorus (P) levels in simulated body fluid after incubation with yttrium and cerium containing disks show a continual decline over the 14-day period. In contrast, Con disks (not containing yttrium or cerium) caused the elimination of Ca in solution after 1 day and throughout the incubation period, and initially showed a decline in P levels followed by an increase at 14 days. Scanning electron microscopy and energy dispersive spectroscopy confirmed the presence of Ca and P on the surface of the simulated body fluid-incubated disks and showed precipitates on Con and HCe (8 mol% cerium) samples. Cell viability of MC3T3 osteoblasts was not significantly affected at a 9% extract concentration. Optical microscopy after 24 h cell incubation with disks showed that Con samples do not support osteoblast or Schwann cell growth, while all yttrium and cerium containing disks have direct contact with osteoblasts spread across the wells. Schwann cells attached in all wells, but only showed spreading with the HY-S (8 mol% yttrium, heated to sintering temperature) and YCe (4 mol% yttrium and cerium) disks. Scanning electron microscopy of the compatible disks shows osteoblast and sNF96.2 Schwann cells attachment and spreading directly on the disk surfaces. © The Author(s) 2016.

  12. Are CEOs Different?

    DEFF Research Database (Denmark)

    Kaplan, Steven N.; Sørensen, Morten

    We use a data set of over 2,600 executive assessments to study thirty individual characteristics of candidates for top executive positions – CEO, CFO, COO and others. Candidate characteristics can be classified by four primary factors: general ability, execution skills, charisma and strategic ski...

  13. MOD approach for the growth of epitaxial CeO2 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors

    International Nuclear Information System (INIS)

    Bhuiyan, M S; Paranthaman, M; Sathyamurthy, S; Aytug, T; Kang, S; Lee, D F; Goyal, A; Payzant, E A; Salama, K

    2003-01-01

    We have grown epitaxial CeO 2 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors using a newly developed metal organic decomposition (MOD) approach. Precursor solution of 0.25 M concentration was spin coated on short samples of Ni-3 at%W (Ni-W) substrates and heat-treated at 1100 C in a gas mixture of Ar-4%H 2 for 15 min. Detailed x-ray studies indicate that CeO 2 films have good out-of-plane and in-plane textures with full-width-half-maximum values of 5.8 deg. and 7.5 deg., respectively. High temperature in situ XRD studies show that the nucleation of CeO 2 films starts at 600 C and the growth completes within 5 min when heated at 1100 C. SEM and AFM investigations of CeO 2 films reveal a fairly dense microstructure without cracks and porosity. Highly textured YSZ barrier layers and CeO 2 cap layers were deposited on MOD CeO 2 -buffered Ni-W substrates using rf-magnetron sputtering. Pulsed laser deposition (PLD) was used to grow YBCO films on these substrates. A critical current, J c , of about 1.5 MA cm -2 at 77 K and self-field was obtained on YBCO (PLD)/CeO 2 (sputtered)/YSZ (sputtered)/CeO 2 (spin-coated)/Ni-W

  14. Metabolomic effects of CeO2, SiO2 and CuO metal oxide nanomaterials on HepG2 cells

    Data.gov (United States)

    U.S. Environmental Protection Agency — The data set is a matrix of cellular biochemical (metabolites) in HepG2 cells treated with various metal oxide nanomaterials composed of CeO2, SiO2 and CuO. This...

  15. Differential genomic effects on signaling pathways by two different CeO2 nanoparticles in HepG2 cells

    Data.gov (United States)

    U.S. Environmental Protection Agency — Differential genomic effects on signaling pathways by two different CeO2 nanoparticles in HepG2 cells. This dataset is associated with the following publication:...

  16. CEO origin and accrual-based earnings management

    NARCIS (Netherlands)

    Kuang, Y.F.; Qin, B.; Wielhouwer, J.

    2014-01-01

    This study examines the influence of CEO origin on accrual-based earnings management and how these effects evolve over the CEO's tenure in office. Compared with CEOs promoted from within the company, CEOs recruited from outside have a stronger incentive to demonstrate their abilities in the initial

  17. Ganoderma-Like MoS2 /NiS2 with Single Platinum Atoms Doping as an Efficient and Stable Hydrogen Evolution Reaction Catalyst.

    Science.gov (United States)

    Guan, Yongxin; Feng, Yangyang; Wan, Jing; Yang, Xiaohui; Fang, Ling; Gu, Xiao; Liu, Ruirui; Huang, Zhengyong; Li, Jian; Luo, Jun; Li, Changming; Wang, Yu

    2018-05-27

    Herein, a unique ganoderma-like MoS 2 /NiS 2 hetero-nanostructure with isolated Pt atoms anchored is reported. This novel ganoderma-like heterostructure can not only efficiently disperse and confine the few-layer MoS 2 nanosheets to fully expose the edge sites of MoS 2 , and provide more opportunity to capture the Pt atoms, but also tune the electronic structure to modify the catalytic activity. Because of the favorable dispersibility and exposed large specific surface area, single Pt atoms can be easily anchored on MoS 2 nanosheets with ultrahigh loading of 1.8 at% (the highest is 1.3 at% to date). Owing to the ganoderma-like structure and platinum atoms doping, this catalyst shows Pt-like catalytic activity for the hydrogen evolution reaction with an ultralow overpotential of 34 mV and excellent durability of only 2% increase in overpotential for 72 h under the constant current density of 10 mA cm -2 . © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Synthesis and characterization of magnesium doped cerium oxide for the fuel cell application

    International Nuclear Information System (INIS)

    Kumar, Amit; Kumari, Monika; Kumar, Mintu; Kumar, Sacheen; Kumar, Dinesh

    2016-01-01

    Cerium oxide has attained much attentions in global nanotechnology market due to valuable application for catalytic, fuel additive, and widely as electrolyte in solid oxide fuel cell. Doped cerium oxide has large oxygen vacancies that allow for greater reactivity and faster ion transport. These properties make cerium oxide suitable material for SOFCs application. Cerium oxide electrolyte requires lower operation temperature which shows improvement in processing and the fabrication technique. In our work, we synthesized magnesium doped cerium oxide by the co-precipitation method. With the magnesium doping catalytic reactivity of CeO_2 was increased. Synthesized nanoparticle were characterized by the XRD and UV absorption techniques.

  19. Au/CeO2-chitosan composite film for hydrogen peroxide sensing

    International Nuclear Information System (INIS)

    Zhang Wei; Xie Guoming; Li Shenfeng; Lu Lingsong; Liu Bei

    2012-01-01

    Au nanoparticles (AuNPs) were in situ synthesized at the cerium dioxide nanoparticles (CeO 2 NPs)-chitosan (CS) composite film by one-step direct chemical reduction, and the resulting Au/CeO 2 -CS composite were further modified for enzyme immobilization and hydrogen peroxide (H 2 O 2 ) biosensing. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), UV-vis spectra and electrochemical techniques have been utilized for characterization of the prepared composite. The stepwise assembly process and electrochemical performances of the biosensor were characterized by means of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and typical amperometric response (i-t). The Au/CeO 2 -CS composite exhibited good conductibility and biocompatibility, and the developed biosensor exhibited excellent response to hydrogen peroxide in the linear range of 0.05-2.5 mM (r = 0.998) with the detection limit of 7 μM (S/N = 3). Moreover, the biosensor presented high affinity (K m app =1.93mM), good reproducibility and storage stability. All these results demonstrate that the Au/CeO 2 -CS composite film can provide a promising biointerface for the biosensor designs and other biological applications.

  20. Initial sintering stage kinetics of CeO2 studied by stepwise isothermal dilatometry

    International Nuclear Information System (INIS)

    El Sayed Ali, M.; Toft Soerensen, O.

    1985-02-01

    The kinetics of the initial sintering stage of CeO 2 is studied by a new dilatometric technique in which the heating of the sample is controlled by its shrinkage rate. By this technique the shrinkage characteristically takes place in 'isothermal steps' which allows both the mechanism and its activation energy to be determined in a single experiment. The basic equations necessary to evaluate the shrinkage data are described, and using these equations on the curves recorded for CeO 2 it it shown that the controlling mechanism for the initial sintering stage for this oxides is grain-boundary diffusion of Ce 4+ -ions with an activation energy of 119.4 kcal/mole (5.2 eV). The corresponding diffusion coefficient is estimated to vary between 8.5 x 10 -17 - 3.1 x 10 -15 cm 2 /sec (1005 - 1099sup(o)C). (author)

  1. Synthesis and characterization of bimetallic Pd-Ni catalysts in a CeO_2 matrix for the generation of H_2 by the reforming reaction of methanol

    International Nuclear Information System (INIS)

    Contreras C, R.

    2016-01-01

    The hydrothermal method was used for the synthesis of CeO_2 nano rods using Ce(NO_3)_3·6H_2O and NH_4OH. The catalytic support was calcined at 700 degrees Celsius. The synthesis of CeO_2 nano rods were impregnated with an aqueous solution of Ni(NO_3)_2·6H_2O by an incipient wetness impregnation method at an appropriate concentration to yield 5 and 15% of Ni in the catalysts. Then 0.5% of Pd was impregnated using PdCl_2. The samples obtained were calcined at 400 and reduced at 450 degrees Celsius. The catalytic materials were characterized by: temperature programmed reduction (TPR), Scanning Electron Microscopy (Sem) , surface area and X-ray diffraction (XRD) . Sem results showed that the CeO_2 is formed by nano rods and in lesser proportion semi spherical particles. Bet surface area of the catalysts decreases with Ni loading onto the CeO_2 nano rods. Pd O and Ni O were reduced at low and high temperature as was observed by TPR. The CeO_2 one-dimensional nano rods showed a highly crystalline structure with sharp diffraction peaks, with a typical fluorite structure (cubic structure of the CeO_2) and characteristic peaks corresponding to metallic Ni. No diffraction peaks of Pd were found. This is due to the low concentration of this metal in the catalyst. These catalysts showed high activity and selectivity to H_2 at maximum reaction temperature. According to the results of activity and selectivity, the catalysts with Pd-Ni are an alternative for the H_2 production in auto thermal reforming reaction of methanol. (Author)

  2. Materials towards carbon-free, emission-free and oil-free mobility: hydrogen fuel-cell vehicles--now and in the future.

    Science.gov (United States)

    Hirose, Katsuhiko

    2010-07-28

    In the past, material innovation has changed society through new material-induced technologies, adding a new value to society. In the present world, engineers and scientists are expected to invent new materials to solve the global problem of climate change. For the transport sector, the challenge for material engineers is to change the oil-based world into a sustainable world. After witnessing the recent high oil price and its adverse impact on the global economy, it is time to accelerate our efforts towards this change. Industries are tackling global energy issues such as oil and CO2, as well as local environmental problems, such as NO(x) and particulate matter. Hydrogen is the most promising candidate to provide carbon-free, emission-free and oil-free mobility. As such, engineers are working very hard to bring this technology into the real society. This paper describes recent progress of vehicle technologies, as well as hydrogen-storage technologies to extend the cruise range and ensure the easiness of refuelling and requesting material scientists to collaborate with industry to fight against global warming.

  3. Hydrogen storage studies on palladium-doped carbon materials (AC, CB, CNMs) @ metal-organic framework-5.

    Science.gov (United States)

    Viditha, V; Srilatha, K; Himabindu, V

    2016-05-01

    Metal organic frameworks (MOFs) are a rapidly growing class of porous materials and are considered as best adsorbents for their high surface area and extraordinary porosity. The MOFs are synthesized by using various chemicals like triethylamine, terepthalic acid, zinc acetate dihydrate, chloroform, and dimethylformamide (DMF). Synthesized MOFs are intercalated with palladium/activated carbon, carbon black, and carbon nanomaterials by chemical reduction method for the purpose of enhancing the hydrogen adsorption capacities. We have observed that the palladium doped activated carbon on MOF-5 showed high hydrogen storage capacity. This may be due to the affinity of the palladium toward hydrogen molecule. The samples are characterized by X-ray diffraction, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. We have observed a clear decrease in the BET surface area and pore volume. The obtained results show a better performance for the synthesized sample. To our best knowledge, no one has reported the work on palladium-doped carbon materials (activated carbon, carbon black, carbon nanomaterials) impregnated to the metal-organic framework-5. We have attempted to synthesize carbon nanomaterials using indigenously fabricated chemical vapor deposition (CVD) unit as a support. We have observed an increase in the hydrogen storage capacities.

  4. Electrochemical impedance spectroscopy study during accelerated life test of conductive oxides: Ti/(Ru + Ti + Ce)O2-system

    International Nuclear Information System (INIS)

    Silva, Leonardo M. da; Fernandes, Karla C.; Faria, Luiz A. de; Boodts, Julien F.C.

    2004-01-01

    Ti-supported (Ru + Ti + Ce)O 2 -electrodes were prepared at 450d deg. C and the service life, t 6V , determined recording chronopotentiometric curves at 0.75Acm -2 (25 ± 1 deg. C). The results revealed a strong influence of the nominal cerium concentration, [CeO 2 ] N , on t 6V , showing substitution of Ti by Ce causes a major decrease in t 6V . The degree of electrode instability, Λ, calculated from the slope of the linear segment present in the chronopotentiometric profiles, showed [CeO 2 ] N exerts a strong influence on Λ. Voltammetric curves recorded at several anodisation times, t, support final electrode deactivation is due to Ti-support passivation. The chronopotentiometric and voltammetric data permitted to present a model for the porous electrode/electrolyte interface. The electrochemical impedance spectroscopic, EIS, investigation as function of t supports the proposed model denouncing a fast growth a TiO 2 interlayer at the Ti o /oxide interface for [CeO 2 ] N >= 30mol%. The studies also support substitution of Ti by Ce leads to an increase in the coating porosity, thus favouring electrode deactivation by passivation of the Ti-substrate. The model proposed for the porous electrode/electrolyte interface combined with the results of the EIS investigation permitted to propose an equivalent circuit to describe the modifications occurring in the electrode structure during anodisation. The true electrocatalytic activity for the oxygen evolution reaction, OER, depends on t and [CeO 2 ] N . The dependency of the inductive behaviour on t was investigated according to the model proposed for the effective inductance, L E , in the high frequency domain

  5. Electrical properties of aluminum-doped zinc oxide (AZO) nanoparticles synthesized by chemical vapor synthesis

    International Nuclear Information System (INIS)

    Hartner, Sonja; Schulz, Christof; Wiggers, Hartmut; Ali, Moazzam; Winterer, Markus

    2009-01-01

    Aluminum-doped zinc oxide nanoparticles have been prepared by chemical vapor synthesis, which facilitates the incorporation of a higher percentage of dopant atoms, far above the thermodynamic solubility limit of aluminum. The electrical properties of aluminum-doped and undoped zinc oxide nanoparticles were investigated by impedance spectroscopy. The impedance is measured under hydrogen and synthetic air between 323 and 673 K. The measurements under hydrogen as well as under synthetic air show transport properties depending on temperature and doping level. Under hydrogen atmosphere, a decreasing conductivity with increasing dopant content is observed, which can be explained by enhanced scattering processes due to an increasing disorder in the nanocrystalline material. The temperature coefficient for the doped samples switches from positive temperature coefficient behavior to negative temperature coefficient behavior with increasing dopant concentration. In the presence of synthetic air, the conductivity firstly increases with increasing dopant content by six orders of magnitude. The origin of the increasing conductivity is the generation of free charge carriers upon dopant incorporation. It reaches its maximum at a concentration of 7.7% of aluminum, and drops for higher doping levels. In all cases, the conductivity under hydrogen is higher than under synthetic air and can be changed reversibly by changing the atmosphere.

  6. Electrical properties of aluminum-doped zinc oxide (AZO) nanoparticles synthesized by chemical vapor synthesis.

    Science.gov (United States)

    Hartner, Sonja; Ali, Moazzam; Schulz, Christof; Winterer, Markus; Wiggers, Hartmut

    2009-11-04

    Aluminum-doped zinc oxide nanoparticles have been prepared by chemical vapor synthesis, which facilitates the incorporation of a higher percentage of dopant atoms, far above the thermodynamic solubility limit of aluminum. The electrical properties of aluminum-doped and undoped zinc oxide nanoparticles were investigated by impedance spectroscopy. The impedance is measured under hydrogen and synthetic air between 323 and 673 K. The measurements under hydrogen as well as under synthetic air show transport properties depending on temperature and doping level. Under hydrogen atmosphere, a decreasing conductivity with increasing dopant content is observed, which can be explained by enhanced scattering processes due to an increasing disorder in the nanocrystalline material. The temperature coefficient for the doped samples switches from positive temperature coefficient behavior to negative temperature coefficient behavior with increasing dopant concentration. In the presence of synthetic air, the conductivity firstly increases with increasing dopant content by six orders of magnitude. The origin of the increasing conductivity is the generation of free charge carriers upon dopant incorporation. It reaches its maximum at a concentration of 7.7% of aluminum, and drops for higher doping levels. In all cases, the conductivity under hydrogen is higher than under synthetic air and can be changed reversibly by changing the atmosphere.

  7. Hydrogen storage property of nanoporous carbon aerogels

    International Nuclear Information System (INIS)

    Shen Jun; Liu Nianping; Ouyang Ling; Zhou Bin; Wu Guangming; Ni Xingyuan; Zhang Zhihua

    2011-01-01

    Carbon aerogels were prepared from resorcinol and formaldehyde via sol-gel process, high temperature carbonization and atmospheric pressure drying technology with solvent replacement. By changing the resorcinol-sodium carbonate molar ratio and the mass fraction of the reactants,resorcinol and formaldehyde, the pore structure of carbon aerogels can be controlled and the palladium-doped carbon aerogels were prepared.By transmission electron microscopy (TEM), X-ray diffraction (XRD) spectra, it is confirmed that the Pd exists in the skeleton structure of carbon aerogels as a form of nano simple substance pellet. The specific surface area is successfully raised by 2 times, and palladium-doped carbon aerogels with a specific surface area of 1 273 m 2 /g have been obtained by carrying out the activation process as the post-processing to the doped carbon aerogels. The hydrogen adsorption results show that the saturated hydrogen storage mass fraction of the carbon aerogels with the specific surface area of 3 212 m 2 /g is 3% in the condition of 92 K, 3.5 MPa, and 0.84% in the condition of 303 K, 3.2 MPa. In addition, the hydrogen adsorption test of palladium-doped carbon aerogels at room temperature (303 K) shows that the total hydrogen storage capacity of doped carbon aerogels is declined due to the relative small specific surface, but the hydrogen storage of unit specific surface area is enhanced. (authors)

  8. Effect of sintering condition on the grain growth of Cr{sub 2}O{sub 3} doped UO{sub 2} pellets

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Jang Soo; Kim, Keon Sik; Kim, Dong Joo; Kim, Jong Hun; Yang, Jae Ho [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    In this paper, Cr{sub 2}O{sub 3} doped UO{sub 2} pellets were fabricated by two-step sintering process. The grain growth of pellet is related to dwell time in a hydrogen atmosphere during sintering process. A large grain pellet can minimize fission gas release and deform easily at an elevated temperature. So, the recent development of nuclear fuel pellet materials is mainly focused on the large grain pellets. The various methods of fabrication processes for large grain UO{sub 2} pellets have been investigated extensively. Those parameters include the additives, sintering temperature, sintering time, sintering atmosphere, and so on. Cr-doped UO{sub 2} pellet is one of the promising candidates for PCI remedy. It was shown that the grain size and softness of UO{sub 2} pellets could be enhanced by doping Cr or Cr compound in UO{sub 2}. Various in-pile test results revealed that the PCI properties were enhanced considerably [4]. In the sintering process of Cr-doped UO{sub 2} pellet, it was known that tight adjusting of sintering atmosphere is most important to achieve large grain pellet. The relevant research revealed that the doped Cr{sub 2}O{sub 3} became liquid phase in optimized oxygen potential and that liquid phase promoted the grain growth. Recently, KAERI has shown that grain size of Cr-doped UO{sub 2} pellet could be more enlarged by adjusting process parameters. In this paper, we introduced a sintering process which can form a liquid phase for a large grain growth in Cr{sub 2}O{sub 3} doped UO{sub 2} pellet. The study on the effect of dwell time in H{sub 2} atmosphere during sintering process on the grain structure of sintered pellet is also a part of this work. In order to obtain large grain in pellet, it is important to increase amount of Cr that can form a liquid phase for grain growth by increasing dwell time in a hydrogen atmosphere during sintering process.

  9. The Market for CEOs

    DEFF Research Database (Denmark)

    Aivazian, Varouj A.; Lai, Tat-kei; Rahaman, Mohammad M.

    2013-01-01

    We investigate empirically a market-based explanation for the rise in recent years in external CEO hiring and compensation and find, consistent with the market-based theory, that firms in industries relying on general managerial skills are more likely to hire CEOs externally than firms...

  10. Enhanced photocatalytic performance of CeO2-TiO2 nanocomposite for degradation of crystal violet dye and industrial waste effluent

    Science.gov (United States)

    Zahoor, Mehvish; Arshad, Amara; Khan, Yaqoob; Iqbal, Mazhar; Bajwa, Sadia Zafar; Soomro, Razium Ali; Ahmad, Ishaq; Butt, Faheem K.; Iqbal, M. Zubair; Wu, Aiguo; Khan, Waheed S.

    2018-03-01

    This study presents the synthesis of CeO2-TiO2 nanocomposite and its potential application for the visible light-driven photocatalytic degradation of model crystal violet dye as well as real industrial waste water. The ceria-titania (CeO2-TiO2) nanocomposite material was synthesised using facile hydrothermal route without the assistance of any template molecule. As-prepared composite was characterised by SEM, TEM, HRTEM, XRD, XPS for surface features, morphological and crystalline characters. The formed nanostructures were determined to possess crystal-like geometrical shape and average size less than 100 nm. The as-synthesised nanocomposite was further investigated for their heterogeneous photocatalytic potential against the oxidative degradation of CV dye taken as model pollutant. The photo-catalytic performance of the as-synthesised material was evaluated both under ultra-violet as well as visible light. Best photocatalytic performance was achieved under visible light with complete degradation (100%) exhibited within 60 min of irradiation time. The kinetics of the photocatalytic process were also considered and the reaction rate constant for CeO2-TiO2 nanocomposite was determined to be 0.0125 and 0.0662 min-1 for ultra-violet and visible region, respectively. In addition, the as-synthesised nanocomposite demonstrated promising results when considered for the photo-catalytic degradation of coloured industrial waste water collected from local textile industry situated in Faisalabad region of Pakistan. Enhanced photo-catalytic performance of CeO2-TiO2 nanocomposite was proposed owing to heterostructure formation leading to reduced electron-hole recombination.

  11. A Facile and Waste-Free Strategy to Fabricate Pt-C/TiO2 Microspheres: Enhanced Photocatalytic Performance for Hydrogen Evolution

    Directory of Open Access Journals (Sweden)

    Hui Li

    2014-01-01

    Full Text Available A facile and waste-free flame thermal synthesis method was developed for preparing Pt modified C/TiO2 microspheres (Pt-C/TiO2. The photocatalysts were characterized with X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope, ultraviolet-visible (UV-vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, and thermogravimetry analysis. The photocatalytic activity was evaluated by hydrogen evolution from water splitting under UV-vis light illumination. Benefitting from the electron-hole separation behavior and reduced overpotential of H+/H2, remarkably enhanced hydrogen production was demonstrated and the photocatalytic hydrogen generation from 0.4 wt% Pt-C/TiO2 increased by 22 times. This study also demonstrates that the novel and facile method is highly attractive, due to its easy operation, requiring no post treatment and energy-saving features.

  12. DFT study of adsorption and dissociation behavior of H2S on Fe-doped graphene

    International Nuclear Information System (INIS)

    Zhang, Hong-ping; Luo, Xue-gang; Song, Hong-tao; Lin, Xiao-yan; Lu, Xiong; Tang, Youhong

    2014-01-01

    Highlights: • Fe-doped and Pt-doped graphene can significantly improve the interactions between H 2 S and graphene. • The location of S had an important role in the interactions between H 2 S and Fe-doped graphene. • The influence of Fe-S distance can be very weak in a certain range and H 2 S can be dissociated into S and H 2 . - Abstracts: Understanding the interaction mechanisms of hydrogen sulfide (H 2 S) with graphene is important in developing graphene-based sensors for gas detection and removal. In this study, the effects of doped Fe atom on interaction of H 2 S with graphene were investigated by density functional theory calculations. Analyses of adsorption energy, electron density difference, and density of states indicated that the doped Fe atom can significantly improve the interaction of H 2 S gas molecules with graphene, as well as Pt-doped graphene. The location of the sulfur atom is important in the interactions between H 2 S and Fe-doped graphene. The influence of the Fe-S distance can be very weak within a certain distance, as simulated in this study

  13. Comment on “Synthesis of ceria (CeO_2 and CeO_2_−_x) nanoparticles via decarbonation and Ce(III) oxidation of synthetic bastnaesite (CeCO_3F)” by Montes-Hernandez et al

    International Nuclear Information System (INIS)

    Gysi, Alexander P.; Williams-Jones, Anthony E.

    2016-01-01

    Montes-Hernandez et al. [5] recently reported results of a study of the decarbonation of fine-grained synthetic bastnäsite-(Ce) precipitates involving the oxidation of Ce(III) to Ce(IV) and the formation of ceria (CeO_2 and CeO_2_-_x with oxygen vacancies) nano-particles. The purpose of their study was to show that oxidation of Ce(III) to Ce(IV) occurs spontaneously during heating of bastnäsite-(Ce) in air, a vacuum, N_2 or Ar gas. However, their interpretation of the formation of CeO_2 is not supported by the findings of Gysi and Williams-Jones [3], who showed that natural bastnäsite-(Ce) decomposes to form rare earth element (REE) oxyfluorides (REEOF). The latter was documented using differential scanning calorimetric (DSC) and thermogravimetric (TGA) experiments under a deoxygenated N_2 atmosphere. In their experiments, Gysi and Williams-Jones [3] found no evidence for the oxidation of Ce(III) to Ce(IV). This raises the question of whether the experiments of Montes-Hernandez et al. [5] in a N_2 atmosphere (and by extension in an Ar atmosphere) were compromised because of contamination by O_2 and that, as a result, they reached the erroneous conclusion that Ce(III) oxidizes spontaneously to Ce(IV) during heating of bastnäsite-(Ce) under these conditions. In order to explain the disagreement between their findings and those of Gysi and Williams-Jones [3], Montes-Hernandez et al. [5], proposed that the X-ray diffraction data of the former study were incorrectly interpreted. Here, we provide further evidence that the natural bastnäsite-(Ce) employed in the study by Gysi and Williams-Jones [3] decomposed to form REE oxyfluorides (i.e., CeOF, LaOF, PrOF and NdOF) and not CeO_2, and supply explanations for why Montes-Hernandez et al. [5] erroneously concluded that CeO_2 is produced during decomposition of this mineral under N_2 and Ar atmospheres. In so doing, we hope to provide new insights into the decomposition of bastnäsite-(Ce) that will help guide future

  14. Colloidal stability of CeO2 nanoparticles coated with either natural organic matter or organic polymers under various hydrochemical conditions

    Science.gov (United States)

    Dippon, Urs; Pabst, Silke; Klitzke, Sondra

    2016-04-01

    The worldwide marked for engineered nanoparticles (ENPs) is growing and concerns on the environmental fate- and toxicity of ENPs are rising. Understanding the transport of ENPs within and between environmental compartments such as surface water and groundwater is crucial for exposition modeling, risk assessment and ultimately the protection of drinking water resources. The transport of ENPs is strongly influenced by the surface properties and aggregation behavior of the particles, which is strongly controlled by synthetic and natural organic coatings. Both, surface properties and aggregation characteristics are also key properties for the industrial application of ENPs, which leads to the development and commercialization of an increasing number of surface-functionalized ENPs. These include metals and oxides such as Cerium dioxide (CeO2) with various organic coatings. Therefore, we investigate CeO2 ENPs with different surface coatings such as weakly anionic polyvinyl alcohol (PVA) or strongly anionic poly acrylic acid (PAA) with respect to their colloidal stability in aqueous matrix under various hydrochemical conditions (pH, ionic strength) and their transport behavior in sand filter columns. Furthermore, we investigate the interaction of naturally occurring organic matter (NOM) with CeO2 ENPs and its effect on surface charge (zeta potential), colloidal stability and transport. While uncoated CeO2 ENPs aggregate at pH > 4 in aqueous matrix, our results show that PAA and PVA surface coatings as well as NOM sorbed to CeO2-NP surfaces can stabilize CeO2 ENPs under neutral and alkaline pH conditions in 1 mM KCl solution. Under slightly acidic conditions, differences between the three particle types were observed. PVA can stabilize particle suspensions in presence of 1 mM KCl at pH > 4.3, PAA at pH >4.0 and NOM at >3.2. While the presence of KCl did not influence particle size of NOM-CeO2 ENPs, CaCl2 at >2 mM lead to aggregation. Further results on the influence of KCl

  15. Transfer-free synthesis of doped and patterned graphene films.

    Science.gov (United States)

    Zhuo, Qi-Qi; Wang, Qi; Zhang, Yi-Ping; Zhang, Duo; Li, Qin-Liang; Gao, Chun-Hong; Sun, Yan-Qiu; Ding, Lei; Sun, Qi-Jun; Wang, Sui-Dong; Zhong, Jun; Sun, Xu-Hui; Lee, Shuit-Tong

    2015-01-27

    High-quality and wafer-scale graphene on insulating gate dielectrics is a prerequisite for graphene electronic applications. For such applications, graphene is typically synthesized and then transferred to a desirable substrate for subsequent device processing. Direct production of graphene on substrates without transfer is highly desirable for simplified device processing. However, graphene synthesis directly on substrates suitable for device applications, though highly demanded, remains unattainable and challenging. Here, we report a simple, transfer-free method capable of synthesizing graphene directly on dielectric substrates at temperatures as low as 600 °C using polycyclic aromatic hydrocarbons as the carbon source. Significantly, N-doping and patterning of graphene can be readily and concurrently achieved by this growth method. Remarkably, the graphene films directly grown on glass attained a small sheet resistance of 550 Ω/sq and a high transmittance of 91.2%. Organic light-emitting diodes (OLEDs) fabricated on N-doped graphene on glass achieved a current density of 4.0 mA/cm(2) at 8 V compared to 2.6 mA/cm(2) for OLEDs similarly fabricated on indium tin oxide (ITO)-coated glass, demonstrating that the graphene thus prepared may have potential to serve as a transparent electrode to replace ITO.

  16. Hydrogenated indium oxide window layers for high-efficiency Cu(In,Ga)Se2 solar cells

    International Nuclear Information System (INIS)

    Jäger, Timo; Romanyuk, Yaroslav E.; Nishiwaki, Shiro; Bissig, Benjamin; Pianezzi, Fabian; Fuchs, Peter; Gretener, Christina; Tiwari, Ayodhya N.; Döbeli, Max

    2015-01-01

    High mobility hydrogenated indium oxide is investigated as a transparent contact for thin film Cu(In,Ga)Se 2 (CIGS) solar cells. Hydrogen doping of In 2 O 3 thin films is achieved by injection of H 2 O water vapor or H 2 gas during the sputter process. As-deposited amorphous In 2 O 3 :H films exhibit a high electron mobility of ∼50 cm 2 /Vs at room temperature. A bulk hydrogen concentration of ∼4 at. % was measured for both optimized H 2 O and H 2 -processed films, although the H 2 O-derived film exhibits a doping gradient as detected by elastic recoil detection analysis. Amorphous IOH films are implemented as front contacts in CIGS based solar cells, and their performance is compared with the reference ZnO:Al electrodes. The most significant feature of IOH containing devices is an enhanced open circuit voltage (V OC ) of ∼20 mV regardless of the doping approach, whereas the short circuit current and fill factor remain the same for the H 2 O case or slightly decrease for H 2 . The overall power conversion efficiency is improved from 15.7% to 16.2% by substituting ZnO:Al with IOH (H 2 O) as front contacts. Finally, stability tests of non-encapsulated solar cells in dry air at 80 °C and constant illumination for 500 h demonstrate a higher stability for IOH-containing devices

  17. Fabrication of hydrogen peroxide biosensor based on Ni doped SnO2 nanoparticles.

    Science.gov (United States)

    Lavanya, N; Radhakrishnan, S; Sekar, C

    2012-01-01

    Ni doped SnO(2) nanoparticles (0-5 wt%) have been prepared by a simple microwave irradiation (2.45 GHz) method. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies confirmed the formation of rutile structure with space group (P(42)/mnm) and nanocrystalline nature of the products with spherical morphology. Direct electrochemistry of horseradish peroxidase (HRP)/nano-SnO(2) composite has been studied. The immobilized enzyme retained its bioactivity, exhibited a surface confined, reversible one-proton and one-electron transfer reaction, and had good stability, activity and a fast heterogeneous electron transfer rate. A significant enzyme loading (3.374×10(-10) mol cm(-2)) has been obtained on nano-Ni doped SnO(2) as compared to the bare glassy carbon (GC) and nano-SnO(2) modified surfaces. This HRP/nano-Ni-SnO(2) film has been used for sensitive detection of H(2)O(2) by differential pulse voltammetry (DPV), which exhibited a wider linearity range from 1.0×10(-7) to 3.0×10(-4)M (R=0.9897) with a detection limit of 43 nM. The apparent Michaelis-Menten constant (K(M)(app)) of HRP on the nano-Ni-SnO(2) was estimated as 0.221 mM. This excellent performance of the fabricated biosensor is attributed to large surface-to-volume ratio and Ni doping into SnO(2) which facilitate the direct electron transfer between the redox enzyme and the surface of electrode. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Room temperature synthesis and enhanced photocatalytic property of CeO2/ZnO heterostructures

    Science.gov (United States)

    Wang, Chao; Fan, Huiqing; Ren, Xiaohu; Fang, Jiawen

    2018-02-01

    To achieve better photocatalytic performance, we proposed a facile solid-state reaction method to produce CeO2/ZnO heterostructures. Ceria and zinc oxide were synthesized simultaneously by thoroughly grinding the mixture of zinc acetate dihydrate, cerium nitrate hexahydrate and sodium hydroxide. The morphology of the as-prepared heterostructures varies dramatically as different amount of ceria was introduced in the composition. The photocatalytic performance of CeO2/ZnO heterojunctions was 4.6 times higher than that of pure ZnO. The enhanced photocatalytic activity could be ascribed to that more electrons and holes could transport to the surface of catalysts and react with the pollution due to the extended light-responsive range, accelerated migration, increased specific surface area and suppressed recombination of photogenerated carriers.

  19. The Effect of Acidic and Redox Properties of V2O5/CeO2-ZrO2 Catalysts in Selective Catalytic Reduction of NO by NH3

    DEFF Research Database (Denmark)

    Putluru, Siva Sankar Reddy; Riisager, Anders; Fehrmann, Rasmus

    2009-01-01

    V2O5 supported ZrO2 and CeO2–ZrO2 catalysts were prepared and characterized by N2 physisorption, XRPD, TPR, and NH3-TPD methods. The influence of calcination temperature from 400 to 600 °C on crystallinity, acidic and redox properties were studied and compared with the catalytic activity...... in the selective catalytic reduction (SCR) of NO with ammonia. The surface area of the catalysts decreased gradually with increasing calcination temperature. The SCR activity of V2O5/ZrO2 catalysts was found to be related with the support crystallinity, whereas V2O5/CeO2–ZrO2 catalysts were also dependent...... on acidic and redox properties of the catalyst. The V2O5/CeO2–ZrO2 catalysts showed high activity and selectivity for reduction of NO with NH3....

  20. Ti-doped hydrogenated diamond like carbon coating deposited by hybrid physical vapor deposition and plasma enhanced chemical vapor deposition

    Science.gov (United States)

    Lee, Na Rae; Sle Jun, Yee; Moon, Kyoung Il; Sunyong Lee, Caroline

    2017-03-01

    Diamond-like carbon films containing titanium and hydrogen (Ti-doped DLC:H) were synthesized using a hybrid technique based on physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD). The film was deposited under a mixture of argon (Ar) and acetylene gas (C2H2). The amount of Ti in the Ti-doped DLC:H film was controlled by varying the DC power of the Ti sputtering target ranging from 0 to 240 W. The composition, microstructure, mechanical and chemical properties of Ti-doped DLC:H films with varying Ti concentrations, were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nano indentation, a ball-on-disk tribometer, a four-point probe system and dynamic anodic testing. As a result, the optimum composition of Ti in Ti-doped DLC:H film using our hybrid method was found to be a Ti content of 18 at. %, having superior electrical conductivity and high corrosion resistance, suitable for bipolar plates. Its hardness value was measured to be 25.6 GPa with a low friction factor.

  1. Hydrogen storage via polyhydride complexes

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, C.M.; Zidan, R.A. [Univ. of Hawaii, Honolulu, HI (United States)

    1998-08-01

    The reversible dehydrogenation of NaAlH{sub 4} is catalyzed in toluene slurries of the NaAlH{sub 4} containing the pincer complex, IrH{sub 4} {l_brace}C{sub 6}H{sub 3}-2,6-(CH{sub 2}PBu{sup t}{sub 2}){sub 2}{r_brace}. The rates of the pincer complex catalyzed dehydrogenation are about five times greater those previously found for NaAlH{sub 4} that was doped with titanium through a wet chemistry method. Homogenization of NaAlH{sub 4} with 2 mole % Ti(OBu{sup n}){sub 4} under an atmosphere of argon produces a novel titanium containing material. TPD measurements show that the dehydrogenation of this material occurs about 30 C lower than that previously found for wet titanium doped NaAlH{sub 4}. In further contrast to wet doped NaAlH{sub 4}, the dehydrogenation kinetics and hydrogen capacity of the novel material are undiminished over several dehydriding/hydriding cycles. Rehydrogenation of the titanium doped material occurs readily at 170 C under 150 atm of hydrogen. TPD measurements show that about 80% of the original hydrogen content (4.2 wt%) can be restored under these conditions.

  2. Resonantly cladding-pumped Yb-free Er-doped LMA fiber laser with record high power and efficiency.

    Science.gov (United States)

    Zhang, Jun; Fromzel, Viktor; Dubinskii, Mark

    2011-03-14

    We report the results of our power scaling experiments with resonantly cladding-pumped Er-doped eye-safe large mode area (LMA) fiber laser. While using commercial off-the-shelf LMA fiber we achieved over 88 W of continuous-wave (CW) single transverse mode power at ~1590 nm while pumping at 1532.5 nm. Maximum observed optical-to-optical efficiency was 69%. This result presents, to the best of our knowledge, the highest power reported from resonantly-pumped Yb-free Er-doped LMA fiber laser, as well as the highest efficiency ever reported for any cladding-pumped Er-doped laser, either Yb-co-doped or Yb-free.

  3. Cerium dioxide (CeO2) nanoparticles decrease arsenite (As(III)) cytotoxicity to 16HBE14o- human bronchial epithelial cells.

    Science.gov (United States)

    Zeng, Chao; Nguyen, Chi; Boitano, Scott; Field, Jim A; Shadman, Farhang; Sierra-Alvarez, Reyes

    2018-07-01

    The production and application of engineered nanoparticles (NPs) are increasing in demand with the rapid development of nanotechnology. However, there are concerns that some of these novel materials could lead to emerging environmental and health problems. Some NPs are able to facilitate the transport of contaminants into cells/organisms via a "Trojan Horse" effect which enhances the toxicity of the adsorbed materials. In this work, we evaluated the toxicity of arsenite (As(III)) adsorbed onto cerium dioxide (CeO 2 ) NPs to human bronchial epithelial cells (16HBE14o-) using the xCELLigence real time cell analyzing system (RTCA). Application of 0.5 mg/L As(III) resulted in 81.3% reduction of cell index (CI, an RTCA measure of cell toxicity) over 48 h when compared to control cells exposed to medium lacking As(III). However, when the cells were exposed to 0.5 mg/L As(III) in the presence of CeO 2 NPs (250 mg/L), the CI was only reduced by 12.9% compared to the control. The CeO 2 NPs had a high capacity for As(III) adsorption (20.2 mg/g CeO 2 ) in the bioassay medium, effectively reducing dissolved As(III) in the aqueous solution and resulting in reduced toxicity. Transmission electron microscopy was used to study the transport of CeO 2 NPs into 16HBE14o- cells. NP uptake via engulfment was observed and the internalized NPs accumulated in vesicles. The results demonstrate that dissolved As(III) in the aqueous solution was the decisive factor controlling As(III) toxicity of 16HBE14o- cells, and that CeO 2 NPs effectively reduced available As(III) through adsorption. These data emphasize the evaluation of mixtures when assaying toxicity. Copyright © 2018 Elsevier Inc. All rights reserved.

  4. Effect of processing conditions and methods on residual stress in CeO2 buffer layers and YBCO superconducting films

    International Nuclear Information System (INIS)

    Xiong Jie; Qin Wenfeng; Cui Xumei; Tao Bowan; Tang Jinlong; Li Yanrong

    2006-01-01

    CeO 2 layers have been fabricated by pulsed laser deposition (PLD) technique on (1 1 0 2) sapphire substrate. Microstructure of CeO 2 layers is characterized by X-ray diffraction as functions of substrate temperature. The effects of the substrate temperature on the residual stress have been studied. The results show that residual stress in CeO 2 film decreased with increasing substrate temperature, not the same development tendency as that of thermal stress. This means that the thermal stress is only a fraction of the residual stress. Moreover, YBCO superconducting films were prepared by direct current (DC) sputtering and pulsed laser deposition (PLD) technique. The residual stress and thermal stress of both YBCO films were measured. PLD processing apparently generated higher intrinsic compressive stresses in comparison to DC sputtering

  5. Cuboid Ni2 P as a Bifunctional Catalyst for Efficient Hydrogen Generation from Hydrolysis of Ammonia Borane and Electrocatalytic Hydrogen Evolution.

    Science.gov (United States)

    Du, Yeshuang; Liu, Chao; Cheng, Gongzhen; Luo, Wei

    2017-11-16

    The design of high-performance catalysts for hydrogen generation is highly desirable for the upcoming hydrogen economy. Herein, we report the colloidal synthesis of nanocuboid Ni 2 P by the thermal decomposition of nickel chloride hexahydrate (NiCl 2 ⋅6 H 2 O) and trioctylphosphine. The obtained nanocuboid Ni 2 P was characterized by using powder X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and inductively coupled plasma atomic emission spectroscopy. For the first time, the as-synthesized nanocuboid Ni 2 P is used as a bifunctional catalyst for hydrogen generation from the hydrolysis of ammonia borane and electrocatalytic hydrogen evolution. Owing to the strong synergistic electronic effect between Ni and P, the as-synthesized Ni 2 P exhibits catalytic performance that is superior to its counterpart without P doping. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Hydrogen role in a carbon-free energy mix

    International Nuclear Information System (INIS)

    2014-02-01

    Among the energy storage technologies under development today, there is today an increasing interest towards the hydrogen-based ones. Hydrogen generation allows to store electricity, while its combustion can supply electrical, mechanical or heat energy. The French Atomic Energy Commission (CEA) started to work on hydrogen technologies at the end of the 1990's in order to reinforce its economical interest. The development of these technologies is one of the 34 French industrial programs presented in September 2013 by the French Minister of productive recovery. This paper aims at identifying the hydrogen stakes in a carbon-free energy mix and at highlighting the remaining technological challenges to be met before reaching an industrial development level

  7. Separation of pure Cerium oxides from rare earth compounds. Homogeneous precipitation using Urea-Hydrogen Peroxide

    International Nuclear Information System (INIS)

    Umeda, K.; Abrao, E.

    1975-01-01

    The obtainment of ceric oxide (CeO 2 ) of purity higher than 97% by application of homogeneous precipitation technique is described. The selective separation of cerium was reached by hydrolysis of urea in the presence of hydrogen peroxide, using a rare earths concentrate named rare earths chloride, a natural mixture of all lanthanides provenient from the industrialization of monazite. The best conditions for the preparation of CeO 2 of 94% purity are: 35-70g R 2 O 3 /1 and pH2,0 hydrolysis temperature: 88-90 0 C, urea/R 2 O 3 ratio: 4, H 2 O 2 /Ce 2 O 3 ratio: 1,5-5,0 and hydrolysis duration: 4 hours. A leaching procedure of the precipitate with 0,25-0,75M NHO 3 leads to a product of 97-99,5% CeO 2

  8. Involvement of intracellular free Ca2+ in enhanced release of herpes simplex virus by hydrogen peroxide

    Directory of Open Access Journals (Sweden)

    Ogawa Yuzo

    2006-08-01

    Full Text Available Abstract Background It was reported that elevation of the intracellular concentration of free Ca2+ ([Ca2+]i by a calcium ionophore increased the release of herpes simplex virus type 1 (HSV-1. Freely diffusible hydrogen peroxide (H2O2 is implied to alter Ca2+ homeostasis, which further enhances abnormal cellular activity, causing changes in signal transduction, and cellular dysfunction. Whether H2O2 could affect [Ca2+]i in HSV-1-infected cells had not been investigated. Results H2O2 treatment increased the amount of cell-free virus and decreased the proportion of viable cells. After the treatment, an elevation in [Ca2+]i was observed and the increase in [Ca2+]i was suppressed when intracellular and cytosolic Ca2+ were buffered by Ca2+ chelators. In the presence of Ca2+ chelators, H2O2-mediated increases of cell-free virus and cell death were also diminished. Electron microscopic analysis revealed enlarged cell junctions and a focal disintegration of the plasma membrane in H2O2-treated cells. Conclusion These results indicate that H2O2 can elevate [Ca2+]i and induces non-apoptotic cell death with membrane lesions, which is responsible for the increased release of HSV-1 from epithelial cells.

  9. Laser Decontamination of Type 304 Stainless Steel Contaminated with Co2+ and CeO2

    International Nuclear Information System (INIS)

    Won, Hui Jun; Baigalmaa, Byambatseren; Moon, Jei Kwon; Jung, Chong Hun; Lee, Kune Woo

    2009-01-01

    The merits of laser decontamination are a remote operation, a short application time, and the high removal efficiency. And also, generation of the secondary waste is negligible. A series of laser decontamination test by Qswitched Nd:YAG laser at 532 nm were performed on stainless steel specimens artificially contaminated with the Co 2+ and CeO 2 , respectively. Test results were examined by SEM and EPMA

  10. Adsorption mechanism and kinetics of azo dye chemicals on oxide nanotubes: a case study using porous CeO_2 nanotubes

    International Nuclear Information System (INIS)

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

    2016-01-01

    Metal oxide nanotubes are believed to be promising materials with adsorption functionality for water purification due to their synergistic effect of the overall microscale morphology for easy separation and nanoscale surface characters providing enough surface active absorption sites. This work shows the synthesis of uniform hierarchical porous CeO_2 nanotubes via nanowire-directed templating method and describes the adsorption behavior of CeO_2 nanotubes for a typical azo dye Congo red which has resistance to oxidation and decoloration in natural conditions. Fourier transform infrared spectroscopy spectra provided the evidence that Congo red was successfully coated on the surface of CeO_2 nanotubes by both bidentate-type bridge link of Ce"4"+ cations from sulfonate SO_3"− groups and the electrostatic attraction between the protonated surface generated by oxygen vacancies and dissociated sulfonate groups. The adsorption kinetic data fitted well to the pseudo-second-order kinetic equation, whereas the Langmuir isotherm equation exhibited better correlation with the experimental data. The calculated maximum adsorption capacity from the isothermal model was 362.32 mg/g. In addition, the prepared CeO_2 nanotubes exhibited good recyclability and reusability as highly efficient adsorbents for Congo red removal after regeneration. These favorable performances enable the obtained CeO_2 nanotubes to be promising materials for dye removal from aqueous solution.Graphical AbstractCeO_2 nanotubes composed of crystallized nanoparticles exhibit well adsorption ability for a typical azo dye Congo red.

  11. Ni-doping effect of Mg(0 0 0 1) surface to use it as a hydrogen storage material

    International Nuclear Information System (INIS)

    Kuklin, Artem V.; Kuzubov, Alexander A.; Krasnov, Pavel O.; Lykhin, Aleksandr O.; Tikhonova, Lyudmila V.

    2014-01-01

    Highlights: • Magnesium surface interaction with nickel at different it location was investigated. • A possibility of nickel migration on magnesium surface was examined. • A possibility of the nickel atoms to aggregate, producing the cluster was investigated. • A step by step diagram of the cluster formation was calculated and constructed. • The final step was the investigation of a hydrogenation process on the Ni cluster. - Abstract: A detailed study of Ni-doped Mg(0 0 0 1) surface performed by PAW method and the gradient corrected density functional GGA-PBE within the framework of generalized Kohn–Sham density functional theory (DFT) is presented in this work. Structural and electronic properties of magnesium surface interaction with nickel for the purpose of such compounds use for creation of hydrogen storage matrixes were investigated here. Choice of the PBE functional was caused by the good accordance of its prediction of the cell parameters with experimental results. It was shown that Ni atoms prefer to substitute for Mg atoms. Using NEB method, the diffusion barrier was calculated, and the most probable reaction path was established. In particular, when the Ni atom dopes the magnesium surface, it can migrate to the bulk and substitute for Mg in subsurface layers. Also a possibility of nickel cluster formation on clean surface of magnesium was examined. The kinetic factors hinder the movement of the nickel atoms to each other and make problematic the formation of clusters. The studies presented here showed that the diffusion barriers of the nickel atom migration from the cluster on the surface to the bulk of magnesium are 1.179 eV and 1.211 eV for the forward and reverse reactions, respectively. Therefore an improvement of the hydrogenation properties of Ni-doped magnesium surface depends on deposition not of the individual atoms, but their clusters. Hydrogenation of Ni cluster doping the magnesium surface was investigated. Initially Kubas

  12. Decoupling Hydrogen and Oxygen Production in Acidic Water Electrolysis Using a Polytriphenylamine-Based Battery Electrode.

    Science.gov (United States)

    Ma, Yuanyuan; Dong, Xiaoli; Wang, Yonggang; Xia, Yongyao

    2018-03-05

    Hydrogen production through water splitting is considered a promising approach for solar energy harvesting. However, the variable and intermittent nature of solar energy and the co-production of H 2 and O 2 significantly reduce the flexibility of this approach, increasing the costs of its use in practical applications. Herein, using the reversible n-type doping/de-doping reaction of the solid-state polytriphenylamine-based battery electrode, we decouple the H 2 and O 2 production in acid water electrolysis. In this architecture, the H 2 and O 2 production occur at different times, which eliminates the issue of gas mixing and adapts to the variable and intermittent nature of solar energy, facilitating the conversion of solar energy to hydrogen (STH). Furthermore, for the first time, we demonstrate a membrane-free solar water splitting through commercial photovoltaics and the decoupled acid water electrolysis, which potentially paves the way for a new approach for solar water splitting. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Natively textured surface hydrogenated gallium-doped zinc oxide transparent conductive thin films with buffer layers for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xin-liang, E-mail: cxlruzhou@163.com; Wang, Fei; Geng, Xin-hua; Huang, Qian; Zhao, Ying; Zhang, Xiao-dan

    2013-09-02

    Natively textured surface hydrogenated gallium-doped zinc oxide (HGZO) thin films have been deposited via magnetron sputtering on glass substrates. These natively textured HGZO thin films exhibit rough pyramid-like textured surface, high optical transmittances in the visible and near infrared region and excellent electrical properties. The experiment results indicate that tungsten-doped indium oxide (In{sub 2}O{sub 3}:W, IWO) buffer layers can effectively improve the surface roughness and enhance the light scattering ability of HGZO thin films. The root-mean-square roughness of HGZO, IWO (10 nm)/HGZO and IWO (30 nm)/HGZO thin films are 28, 44 and 47 nm, respectively. The haze values at the wavelength of 550 nm increase from 7.0% of HGZO thin film without buffer layer to 18.37% of IWO (10 nm)/HGZO thin film. The optimized IWO (10 nm)/HGZO exhibits a high optical transmittance of 82.18% in the visible and near infrared region (λ ∼ 400–1100 nm) and excellent electrical properties with a relatively low sheet resistance of 3.6 Ω/□ and the resistivity of 6.21 × 10{sup −4} Ωcm. - Highlights: • Textured hydrogenated gallium-doped zinc oxide (HGZO) films were developed. • Tungsten-doped indium oxide (IWO) buffer layers were applied for the HGZO films. • Light-scattering ability of the HGZO films can be improved through buffer layers. • Low sheet resistance and high haze were obtained for the IWO(10 nm)/HGZO film. • The IWO/HGZO films are promising transparent conductive layers for solar cells.

  14. Thermocatalytic CO2-Free Production of Hydrogen from Hydrocarbon Fuels

    Energy Technology Data Exchange (ETDEWEB)

    University of Central Florida

    2004-01-30

    The main objective of this project is the development of an economically viable thermocatalytic process for production of hydrogen and carbon from natural gas or other hydrocarbon fuels with minimal environmental impact. The three major technical goals of this project are: (1) to accomplish efficient production of hydrogen and carbon via sustainable catalytic decomposition of methane or other hydrocarbons using inexpensive and durable carbon catalysts, (2) to obviate the concurrent production of CO/CO{sub 2} byproducts and drastically reduce CO{sub 2} emissions from the process, and (3) to produce valuable carbon products in order to reduce the cost of hydrogen production The important feature of the process is that the reaction is catalyzed by carbon particulates produced in the process, so no external catalyst is required (except for the start-up operation). This results in the following advantages: (1) no CO/CO{sub 2} byproducts are generated during hydrocarbon decomposition stage, (2) no expensive catalysts are used in the process, (3) several valuable forms of carbon can be produced in the process depending on the process conditions (e.g., turbostratic carbon, pyrolytic graphite, spherical carbon particles, carbon filaments etc.), and (4) CO{sub 2} emissions could be drastically reduced (compared to conventional processes).

  15. A DLTS study of hydrogen doped czochralski-grown silicon

    Energy Technology Data Exchange (ETDEWEB)

    Jelinek, M. [Infineon Technologies Austria AG, 9500 Villach (Austria); Laven, J.G. [Infineon Technologies AG, 81726 Munich (Germany); Kirnstoetter, S. [Institute of Solid State Physics, Graz University of Technology, 8010 Graz (Austria); Schustereder, W. [Infineon Technologies Austria AG, 9500 Villach (Austria); Schulze, H.-J. [Infineon Technologies AG, 81726 Munich (Germany); Rommel, M. [Fraunhofer Institute of Integrated Systems and Devices IISB, 91058 Erlangen (Germany); Frey, L. [Fraunhofer Institute of Integrated Systems and Devices IISB, 91058 Erlangen (Germany); Chair of Electron Devices, FAU Erlangen-Nuremberg, 91058 Erlangen (Germany)

    2015-12-15

    In this study we examine proton implanted and subsequently annealed commercially available CZ wafers with the DLTS method. Depth-resolved spreading resistance measurements are shown, indicating an additional peak in the induced doping profile, not seen in the impurity-lean FZ reference samples. The additional peak lies about 10–15 μm deeper than the main peak near the projected range of the protons. A DLTS characterization in the depth of the additional peak indicates that it is most likely not caused by classical hydrogen-related donors known also from FZ silicon but by an additional donor complex whose formation is assisted by the presence of silicon self-interstitials.

  16. Metabolomic effects in HepG2 cells exposed to CeO2, SiO2 and CuO nanomaterials.

    Science.gov (United States)

    To better assess potential hepatotoxicity of nanomaterials, human liver HepG2 cells were exposed for three days to 5 different CeO2 (either 30 or 100 ug/ml), 3 SiO2 based (30 ug/ml) or 1 CuO (3 ug/ml) nanomaterials with dry primary particle sizes ranging from 15 to 213 nm. Metab...

  17. Temperature dependent selective detection of hydrogen and acetone using Pd doped WO3/reduced graphene oxide nanocomposite

    Science.gov (United States)

    Kaur, Jasmeet; Anand, Kanica; Kohli, Nipin; Kaur, Amanpreet; Singh, Ravi Chand

    2018-06-01

    Reduced graphene oxide (RGO) and Pd doped WO3 nanocomposites were fabricated by employing electrostatic interactions between poly (diallyldimethylammonium chloride) (PDDA) modified Pd doped WO3 nanostructures and graphite oxide (GO) and studied for their gas sensing application. XRD, Raman, FTIR, FESEM-EDX, TEM, TGA, XPS and Photoluminescence techniques were used for characterization of as-synthesized samples. Gas sensing studies revealed that the sensor with optimized doping of 1.5 mol% Pd and 1 wt% GO shows temperature dependent selectivity towards hydrogen and acetone. The role of WO3, Pd and RGO has been discussed in detail for enhanced sensing performance.

  18. Enhancement of critical current density of YBa2Cu3O7-δ thin films by nanoscale CeO2 pretreatment of substrate surfaces

    International Nuclear Information System (INIS)

    Cui, X.M.; Liu, G.Q.; Wang, J.; Huang, Z.C.; Zhao, Y.T.; Tao, B.W.; Li, Y.R.

    2007-01-01

    YBa 2 Cu 3 O 7-δ (YBCO) films were prepared on single-crystal SrTiO 3 substrates with metal-organic deposition using trifluoroacetates (TFA-MOD). Positive results have been acquired in controlled study to investigate the effects of substrate surface modification on the growth-induced flux-pinning nanostructures in YBCO films. Nanoscale CeO 2 particles were applied to single-crystal SrTiO 3 substrate surfaces using pulsed laser deposition before YBCO precursors coating. Superconducting properties of the YBCO films grown on the controlled CeO 2 -modified substrates have shown substantial improvement in the critical current densities (J c ) at 77 K over those grown on untreated substrates in almost all the field (78% increment at 1 T, 77 K). We think the reason is that the CeO 2 nanoparticles act as pinning centers

  19. Impurity doping effects on the orbital thermodynamic properties of hydrogenated graphene, graphane, in Harrison model

    Science.gov (United States)

    Yarmohammadi, Mohsen

    2016-12-01

    Using the Harrison model and Green's function technique, impurity doping effects on the orbital density of states (DOS), electronic heat capacity (EHC) and magnetic susceptibility (MS) of a monolayer hydrogenated graphene, chair-like graphane, are investigated. The effect of scattering between electrons and dilute charged impurities is discussed in terms of the self-consistent Born approximation. Our results show that the graphane is a semiconductor and its band gap decreases with impurity. As a remarkable point, comparatively EHC reaches almost linearly to Schottky anomaly and does not change at low temperatures in the presence of impurity. Generally, EHC and MS increases with impurity doping. Surprisingly, impurity doping only affects the salient behavior of py orbital contribution of carbon atoms due to the symmetry breaking.

  20. Defect-mediated magnetism of transition metal doped zinc oxide thin films

    Science.gov (United States)

    Roberts, Bradley Kirk

    Magnetism in transition metal doped wide band-gap materials is of interest to further the fundamental science of materials and future spintronics applications. Large inter-dopant separations require mediation of ferromagnetism by some method; carrier-mediated mechanisms are typically applicable to dilute magnetic semiconductors with low Curie temperatures. Dilute magnetic oxides, commonly with poor conductivity and TC above room temperature, cannot be described within this theory. Recent experiment and theory developments suggest that ferromagnetic exchange in these materials can be mediated by defects. This research includes experimental results justifying and developing this approach. Thin films of Cr doped ZnO (band gap ˜3.3 eV) were deposited with several processing variations to enhance the effects of either 0-dimensional (vacancy, hydrogen-related defect) or two-dimensional defects (surface/interface) and thereby affect magnetism and conductivity. We observe surface magnetism in dielectric thin films of oxygen-saturated ZnO:Cr with spontaneous magnetic moment and conductance dropping approximately exponentially with increasing thickness. Uniform defect concentrations would not result in such magnetic ordering behavior indicating that magnetism is mediated either by surface defects or differing concentrations of point defects near the surface. Polarized neutron reflectivity profiling confirms a magnetically active region of ˜8 nm at the film surface. Hydrogen is notoriously present as a defect and carrier dopant in ZnO, and artificial introduction of hydrogen in dielectric ZnO:Cr films results in varying electronic and magnetic behavior. Free carriers introduced with hydrogen doping are not spin-polarized requiring an alternative explanation for ferromagnetism. We find from positron annihilation spectroscopy measurements that hydrogen doping increases the concentration of an altered VZn-related defect (a preliminary interpretation) throughout the film, which

  1. Facile biological synthetic strategy to morphologically aligned CeO2/ZrO2 core nanoparticles using Justicia adhatoda extract and ionic liquid: Enhancement of its bio-medical properties.

    Science.gov (United States)

    Pandiyan, Nithya; Murugesan, Balaji; Sonamuthu, Jegatheeswaran; Samayanan, Selvam; Mahalingam, Sundrarajan

    2018-01-01

    In this study, a typical green synthesis route has approached for CeO 2 /ZrO 2 core metal oxide nanoparticles using ionic liquid mediated Justicia adhatoda extract. This synthesis method is carried out at simple room temperature condition to obtain the core metal oxide nanoparticles. XRD, SEM and TEM studies employed to study the crystalline and surface morphological properties under nucleation, growth, and aggregation processes. CeO 2 /ZrO 2 core metal oxides display agglomerated nano stick-like structure with 20-45nm size. GC-MS spectroscopy confirms the presence of vasicinone and N,N-Dimethylglycine present in the plant extract, which are capable of converting the corresponding metal ion precursor to CeO 2 /ZrO 2 core metal oxide nanoparticles. In FTIR, the corresponding stretching for Ce-O and Zr-O bands indicated at 498 and 416cm -1 and Raman spectroscopy also supports typical stretching frequencies at 463 and 160cm -1 . Band gap energy of the CeO 2 /ZrO 2 core metal oxide is 3.37eV calculated from UV- DRS spectroscopy. The anti-bacterial studies performed against a set of bacterial strains the result showed that core metal oxide nanoparticles more susceptible to gram-positive (G+) bacteria than gram-negative (G-) bacteria. A unique feature of the antioxidant behaviors core metal oxides reduces the concentration of DPPH radical up to 89%. The CeO 2 /ZrO 2 core metal oxide nanoparticles control the S. marcescent bio-film formation and restrict the quorum sensing. The toxicology behavior of CeO 2 /ZrO 2 core metal oxide NPs is found due to the high oxygen site vacancies, ROS formation, smallest particle size and higher surface area. This type of green synthesis route may efficient and the core metal oxide nanoparticles will possess a good bio-medical agent in future. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Photoluminescence properties of cerium oxide nanoparticles as a function of lanthanum content

    International Nuclear Information System (INIS)

    Deus, R.C.; Cortés, J.A.; Ramirez, M.A.; Ponce, M.A.; Andres, J.; Rocha, L.S.R.

    2015-01-01

    Highlights: • CeO 2 nanoparticles were obtained by microwave-hydrothermal method. • Rietveld refinement reveals a cubic structure. • KOH mineralizer agent exhibit weak agglomeration at low temperature and shorter time. - Abstract: The structural and photoluminescent properties at room temperature of CeO 2 and La-doped CeO 2 particles were undertaken. The obtained particles were synthesized by a microwave-assisted hydrothermal method (MAH) under different lanthanum contents. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman), Ultra-violet spectroscopy (UV–vis) and photoluminescence (PL) measurements were carried out. XRD revealed that the powders are free of secondary phases and crystallize in the cubic structure. Raman data show that increasing La doping content increase oxygen vacancies due to lattice expansion. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. Lanthanum addition creates oxygen vacancies and shifts the photoluminescence in the low energy range leading to intense PL emission

  3. Comparative exploration of hydrogen sulfide and water transmembrane free energy surfaces via orthogonal space tempering free energy sampling.

    Science.gov (United States)

    Lv, Chao; Aitchison, Erick W; Wu, Dongsheng; Zheng, Lianqing; Cheng, Xiaolin; Yang, Wei

    2016-03-05

    Hydrogen sulfide (H2 S), a commonly known toxic gas compound, possesses unique chemical features that allow this small solute molecule to quickly diffuse through cell membranes. Taking advantage of the recent orthogonal space tempering (OST) method, we comparatively mapped the transmembrane free energy landscapes of H2 S and its structural analogue, water (H2 O), seeking to decipher the molecular determinants that govern their drastically different permeabilities. As revealed by our OST sampling results, in contrast to the highly polar water solute, hydrogen sulfide is evidently amphipathic, and thus inside membrane is favorably localized at the interfacial region, that is, the interface between the polar head-group and nonpolar acyl chain regions. Because the membrane binding affinity of H2 S is mainly governed by its small hydrophobic moiety and the barrier height inbetween the interfacial region and the membrane center is largely determined by its moderate polarity, the transmembrane free energy barriers to encounter by this toxic molecule are very small. Moreover when H2 S diffuses from the bulk solution to the membrane center, the above two effects nearly cancel each other, so as to lead to a negligible free energy difference. This study not only explains why H2 S can quickly pass through cell membranes but also provides a practical illustration on how to use the OST free energy sampling method to conveniently analyze complex molecular processes. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  4. Synthesis and characterization of ZrO2-CuO co-doped ceria nanoparticles via chemical precipitation method.

    Science.gov (United States)

    Viruthagiri, G; Gopinathan, E; Shanmugam, N; Gobi, R

    2014-10-15

    In the present study, the fluorite cubic phase of bare and ZrO2-CuO co-doped ceria (CeO2) nanoparticles have been synthesized through a simple chemical precipitation method. X-ray diffraction results revealed that average grain sizes of the samples are within 5-6nm range. The functional groups present in the samples were identified by Fourier Transform Infrared Spectroscopy (FTIR) study. Surface area measurement was carried out for the ceria nanoparticles to characterize the surface properties of the synthesized samples. The direct optical cutoff wavelength from DRS analysis was blue-shifted evidently with respect to the bulk material and indicated quantum-size confinement effect in the nanocrystallites. PL spectra revealed the strong and sharp UV emission at 401nm. The surface morphology and the element constitution of the pure and doped nanoparticles were studied by scanning electron microscope fitted with energy dispersive X-ray spectrometer arrangement. The thermal decomposition course was followed using thermo gravimetric and differential thermal analyses (TG-DTA). Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Earnings Management Surrounding CEO Turnover: Evidence from Korea

    OpenAIRE

    JONG-SEO CHOI; YOUNG-MIN KWAK; CHONGWOO CHOE

    2012-01-01

    This article examines the empirical relation between CEO turnover and earnings management in Korea using a sample of 317 CEO turnovers and 634 non-turnover control firms during the period of 2001-2008. We classify CEO turnovers into four types depending on whether the departure of outgoing CEO is peaceful or forced and the incoming CEO is promoted from within or recruited from outside the firm. We measure earnings management by both discretionary accruals and real activities management. We al...

  6. Vice President of Medical Affairs--moving on up to CEO?

    Science.gov (United States)

    Tyler, J L

    1999-01-01

    Increasingly, physician executives are reaching the conclusion that if they choose, they may be viable candidates for CEO positions. While this opinion has merit, it must be tempered by marketplace realities. A fundamental issue for VPMAs aspiring to become CEOs is that they have little formalized training or education for CEO roles. Also, they may lack team-building skills--a critical success factor. Physician executives who seek out professional development opportunities that enhance both their interpersonal/management and "business" skills--accounting, finance, and planning--are more likely to be attractive candidates and succeed once they are in the position. Another consideration is that the CEO position usually has a precursor role--the COO. This position is the training ground for the CEO. Physician executives aspiring to be CEO will want to consider the following suggestions: (1) Make your intentions known; (2) groom your successor; (3) request a title change; (4) get your master's degree; (5) pursue professional development opportunities; (6) consider leaving the organization; and (7) talk with your family.

  7. Nitrate conversion and supercritical fluid extraction of UO2-CeO2 solid solution prepared by an electrolytic reduction-coprecipitation method

    International Nuclear Information System (INIS)

    Zhu, L.Y.; Duan, W.H.; Wen, M.F.; Xu, J.M.; Zhu, Y.J.

    2014-01-01

    A low-waste technology for the reprocessing of spent nuclear fuel (SNF) has been developed recently, which involves the conversion of actinide and lanthanide oxides with liquid N 2 O 4 into their nitrates followed by supercritical fluid extraction of the nitrates. The possibility of the reprocessing of SNF from high-temperature gas-cooled reactors (HTGRs) with nitrate conversion and supercritical fluid extraction is a current area of research in China. Here, a UO 2 -CeO 2 solid solution was prepared as a surrogate for a UO 2 -PuO 2 solid solution, and the recovery of U and Ce from the UO 2 -CeO 2 solid solution with liquid N 2 O 4 and supercritical CO 2 containing tri-n-butyl phosphate (TBP) was investigated. The UO 2 -CeO 2 solid solution prepared by electrolytic reduction-coprecipitation method had square plate microstructures. The solid solution after heat treatment was completely converted into nitrates with liquid N 2 O 4 . The XRD pattern of the nitrates was similar to that of UO 2 (NO 3 ) 2 . 3H 2 O. After 120 min of online extraction at 25 MPa and 50 , 99.98% of the U and 98.74% of the Ce were recovered from the nitrates with supercritical CO 2 containing TBP. The results suggest a promising potential technology for the reprocessing of SNF from HTGRs. (orig.)

  8. Mg2+ Doped into Electro-synthesized HKUST-1 and Their Initial Hydrogen Sorption Properties

    Science.gov (United States)

    Lestari, W. W.; Ni'maturrohmah, D.; Arrozi, U. S. F.; Suwarno, H.

    2018-01-01

    The hydrogen storage materials are essentially play important roles in supporting the utilization of hydrogen as a promising alternative energy. Several innovative materials have been proposed and intensively investigated in this regard, including Metal-Organic Framework (MOFs). MOFs type HKUST-1 [Cu3(BTC)2] (BTC = benzene-tri-carboxylate) is the most explored materials in hydrogen storage. In this research, HKUST-1 was electro-synthesized under 15 volt for 1.5 h. This material was ex-situ modified with magnesium(II) ion with variation: 3, 5 and 10 wt% to add attractive sites for hydrogen to form Mg2+@HKUST-1. The final materials were characterized by XRD, FTIR, SEM-EDX, and SAA. Hydrogen sorption measurement was conducted using Sievert system at 30 and 80 °C with pressure from 0.2 to 1.5 bar in 10 minutes for each condition. According to XRD analysis, the basic structure of Mg2+@HKUST-1 was remaining stable. In contrary, SEM analysis showed that HKUST-1 morphology was changed after modification with Mg2+. In addition, the surface area of materials significantly increased from 372.112 to 757.617m2/g, based on SAA analysis. The presence of Mg2+ in the HKUST-1 increased the hydrogen sorption capacity up to 0.475 wt% at 1.4 bar at 30 °C and 0.256 wt% at 80 °C (1.4 bar).

  9. The use of CeO2-Co3O4 oxides as a catalyst for the reduction of N2O emission

    Directory of Open Access Journals (Sweden)

    Rajska Maria

    2016-01-01

    Full Text Available The morphological characterization of a series of cobalt-cerium oxide composites prepared by the deposition of CeO2 onto Co3O4 powder with a molar ratio of cerium oxide to Co3O4 in the range of 0 to 1 was performed. The powders were also impregnated with a solution of K2CO3 to obtain the theoretical content of potassium atoms 2at·nm−2. To investigate the effect of adding specific amount of CeO2 on the catalytic activity, the X-ray diffraction, SEM-EDX, laser particle size distribution and BET surface area measurements were used. The catalysts were tested through the low-temperature decomposition of nitrous oxide in the temperature range of 50°C to 700°C. The addition of CeO2 and K always moved the temperature of a complete N2O conversion towards lower temperatures (480°C-540°C to 340°C-420°C. The best catalytic properties were shown by the samples in which the ratio of cerium oxide to cobalt oxide ranged from 0.4 to 0.7.

  10. Annealing-free synthesis of C-N co-doped TiO{sub 2} hierarchical spheres by using amine agents via microwave-assisted solvothermal method and their photocatalytic activities

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yu-Chun, E-mail: yuchunwu@mail.ncku.edu.tw; Ju, Lung-Shen

    2014-08-01

    Highlights: • The synthesis method for C-N co-doped TiO{sub 2} hierarchical spheres is proposed. • Microwave-assisted solvothermal method is applied. • C and N are doped into TiO{sub 2} via a direct chelating reaction of amine compounds. • The photodegradation rate is eightfold higher than the commercial P25 powders. - Abstract: The annealing-free synthesis of C-N co-doped TiO{sub 2} hierarchical spheres is proposed in this study. C and N were doped into the TiO{sub 2} structure via a direct chelating process to the Ti-precursor by using different amine agents, including hexadecylamine (HDA), diethylamine (DEA), trimethylamine (TMA), and diethylenetriamine (DETA). C-N co-doped TiO{sub 2} spheres (300 nm to 500 nm) composed of nanoparticles approximately 11 nm to 13 nm in size were obtained via an efficient microwave-assisted solvothermal reaction at 190 °C for 60 min. The effects of C and N doping by using different amine compounds on the bandgap energy and photocatalytic performance of TiO{sub 2} were investigated. Among the amine compounds, DETA provided the highest chelating efficiency because it provides two primary amine groups, which resulted in the highest C and N doping concentrations and the largest degree of bandgap narrowing (2.77 eV); nevertheless, the high chelating ratio of C and N restrained the crystallization of TiO{sub 2} and considerably decreased its photocatalytic activity. The use of TMA produced optimal C and N doping concentrations, which effectively reduced the bandgap of TiO{sub 2} to 2.85 eV without affecting its crystallization. Its photodecomposition activity to rhodamine B was eightfold of that of commercial Degussa P25 powders under visible light irradiation.

  11. Hydrogen passivation of titanium impurities in silicon: Effect of doping conditions

    Energy Technology Data Exchange (ETDEWEB)

    Santos, P.; Coutinho, J., E-mail: jose.coutinho@ua.pt; Torres, V. J. B. [Department of Physics and I3N, University of Aveiro, Campus Santiago, 3810-193 Aveiro (Portugal); Rayson, M. J. [Department of Chemistry, University of Surrey, Guildford GU2 7XH (United Kingdom); Briddon, P. R. [School of Electrical, Electronic and Computer Engineering, Newcastle University, Newcastle Upon Tyne NE1 7RU (United Kingdom)

    2014-07-21

    While the contamination of solar silicon by fast diffusing transition metals can be now limited through gettering, much attention has been drawn to the slow diffusing species, especially the early 3d and 4d elements. To some extent, hydrogen passivation has been successful in healing many deep centers, including transition metals in Si. Recent deep-level transient spectroscopy (DLTS) measurements concerning hydrogen passivation of Ti revealed the existence of at least four electrical levels related to Ti{sub i}H{sub n} in the upper-half of the gap. These findings challenge the existing models regarding both the current level assignment as well as the structure/species involved in the defects. We revisit this problem by means of density functional calculations and find that progressive hydrogenation of interstitial Ti is thermodynamically stable in intrinsic and n-doped Si. Full passivation may not be possible to attain in p-type Si as Ti{sub i}H{sub 3} and Ti{sub i}H{sub 4} are metastable against dissociation and release of bond-centered protons. All DLTS electron traps are assigned, namely, E40′ to Ti{sub i}H(-/0), E170′ to Ti{sub i}H{sub 3}(0/+), E(270) to Ti{sub i}H{sub 2}(0/+), and E170 to Ti{sub i}H(0/+) transitions. Ti{sub i}H{sub 4} is confirmed to be electrically inert.

  12. Properties of ceria doped with gadolinia via microwave-assisted hydrothermal synthesis

    International Nuclear Information System (INIS)

    Carregosa, J.D.C.; Oliveira, R.M.P.B.; Macedo, D.A.; Nascimento, R.M.

    2016-01-01

    The solid solution of CeO_2 doped with Gd"3"+ (CGO) is a promising candidate for electrolyte in Solid Oxide Full Cells (SOFCs) operating in intermediate and low temperatures. The reduction of the working temperature of these energy conversion devices is the great technological challenge to its marketing. In this work, nanocrystalline powders of Ce_1_-_xGd_xO_2_-_x_/_2 with x=0, x=0.1 e x=0.2 were obtained via microwave-hydrothermal synthesis at low temperature and times of synthesis (10 and 20 min at 120° C). The powders were analyzed by TG-DTA, DRX and dilatometry. The results showed characteristic peaks of the cubic fluorite-type structure, referring to the cerium oxide (CeO_2), without the presence of secondary peaks. It was also observed that the samples processed at levels of 10 and 20 minutes showed distinct behaviors in contrast to the concentrations of Gd"3"+. (author)

  13. A. C. conduction behaviour in amorphous WO 3 /CEO 2 thin film ...

    African Journals Online (AJOL)

    A. C. conduction behaviour in amorphous WO3/CEO2 thin film. B Yagoubi, C A Hogarth, A Boukorrt. Abstract. No Abstract. Technologies Avancees Vol. 17 2005: pp. 5-8. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · http://dx.doi.org/10.4314/ta.v17i1.18478.

  14. CEO Origin and Accrual-Based Earnings Management

    NARCIS (Netherlands)

    Kuang, Y.; Qin, B.; Wielhouwer, J.L.

    2014-01-01

    This study examines the influence of CEO origin on accrual-based earnings management and how these effects evolve over the CEO’s tenure in office. Compared with CEOs promoted from within the company, CEOs recruited from outside have a stronger incentive to demonstrate their abilities in the initial

  15. Synthesis and characterization of binary (CuO)0.6(CeO2)0.4 nanoparticles via a simple heat treatment method

    Science.gov (United States)

    Baqer, Anwar Ali; Matori, Khamirul Amin; Al-Hada, Naif Mohammed; Shaari, Abdul Halim; Kamari, Halimah Mohamed; Saion, Elias; Chyi, Josephine Liew Ying; Abdullah, Che Azurahanim Che

    2018-06-01

    A binary (CuO)0.6 (CeO2)0.4 nanoparticles were prepared via thermal treatment method, using copper nitrate, cerium nitrate as precursors, PVP as capping agent and de-ionized water as a solvent. The structures, morphology, composition of the element and optical properties of these nanoparticles have been studied under different temperatures using various techniques. The XRD spectrum of the samples at 500 °C and above confirmed the existence of both monoclinic (CuO) and cubic fluorite (CeO2) structures. The findings of FESEM and TEM exhibited the average practical size and agglomeration increment with an elevation in the calcination temperature. The synthesized nanoparticles were also characterized by FTIR, which indicated the formation of binary Cu-O and Ce-O bonds. The EDX analysis was performed to indicate the chemical composition of the sample. The double energy band gaps of (CuO)0.6(CeO2)0.4 reduction with rising calcination temperature, can be referred to the enhancement of the crystallinity of the samples. PL intensity of (CuO)0.6(CeO2)0.4 nanoparticles peaks, which increased with the elevation of the calcination temperature to 800 °C was observed from the PL spectrum; this was due to the increment of the particle size that occurred.

  16. Effect of cerium doping on the electrical properties of ultrathin indium tin oxide films for application in touch sensors

    International Nuclear Information System (INIS)

    Kang, Saewon; Cho, Sanghyun; Song, Pungkeun

    2014-01-01

    The electrical and microstructure properties of cerium doped indium tin oxide (ITO:Ce) ultrathin films were evaluated to assess their potential application in touch sensors. 10 to 150-nm ITO and ITO:Ce films were deposited on glass substrates (200 °C) by DC magnetron sputtering using different ITO targets (doped with CeO 2 : 0, 1, 3, 5 wt.%). ITO:Ce (doped with CeO 2 : 3 wt.%) films with thickness < 25 nm showed lower resistivity than ITO. This lower resistivity was accompanied by a significant increase in the Hall mobility despite a decrease in crystallinity. In addition, the surface morphology and wetting properties improved with increasing Ce concentration. This is related to an earlier transition from an island structure to continuous film formation caused by an increase in the initial nucleation density. - Highlights: • 10 to 150-nm InSnO 2 (ITO) and ITO:Ce thin films were deposited by sputtering. • ITO:Ce films with thickness < 25 nm showed lower resistivity than ITO. • Hall mobility was strongly affected by initial film formation. • Surface morphology and wetting property improved with increasing Ce concentration. • Such behavior is related to an earlier transition to continuous film formation

  17. N-doped TiO2 photo-catalyst for the degradation of 1,2-dichloroethane under fluorescent light

    International Nuclear Information System (INIS)

    Lin, Yi-Hsing; Chiu, Tang-Chun; Hsueh, Hsin-Ta; Chu, Hsin

    2011-01-01

    The photo-catalytic degradation of 1,2-dichloroethane (1, 2-DCE) using nitrogen-doped TiO 2 photo-catalysts under fluorescent light irradiation was investigated. Highly pure TiO 2 and nitrogen-doped TiO 2 were prepared by a sol-gel method and characterized by thermo-gravimetric/differential-thermal analysis (TG/DTA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the photo-catalysts were mainly nano-size with an anatase-phase structure. The degradation reaction of 1,2-DCE was operated under visible-light irradiation, and the photo-catalytic oxidation was conducted in a batch photo-reactor with various nitrogen doping ratios (N/Ti = 0-25 mol%). The relative humidity (RH) was controlled at 0-20% and the oxygen concentration was controlled at 0-21%. The photo-degradation with nitrogen-doped TiO 2 showed superior photo-catalytic activity compared to that for pure TiO 2 . TiO 2 doped with 15 mol% nitrogen exhibited the best photo-catalytic efficiency under the tested conditions. The products from the 1,2-DCE photo-catalytic oxidation were CO 2 and water; the by-products included dichloromethane, methyl chloride, ethyl chloride, carbon monoxide, and hydrogen chloride. The reaction pathway of 1,2-DCE indicates that oxygen molecules are the major factor that causes the degradation of 1,2-DCE in the gas phase.

  18. Single cobalt sites in mesoporous N-doped carbon matrix for selective catalytic hydrogenation of nitroarenes

    KAUST Repository

    Sun, Xiaohui

    2017-11-20

    A supported cobalt catalyst with atomically dispersed Co-Nx sites (3.5 wt% Co) in a mesoporous N-doped carbon matrix (named Co@mesoNC) is synthesized by hydrolysis of tetramethyl orthosilicate (TMOS) in a Zn/Co bimetallic zeolitic imidazolate framework (BIMZIF(Co,Zn)), followed by high-temperature pyrolysis and SiO2 leaching. A combination of TEM, XRD XPS and X-ray absorption spectroscopy studies confirm the absence of cobalt nanoparticles and indicate that these highly dispersed cobalt species are present in the form of Co-Nx. The exclusive formation of Co-Nx sites in the carbon matrix is attributed to the presence of a large amount of Zn and N in the BIMZIF precursor together with the presence of SiO2 in the pore space of this framework, extending the initial spatial distance between cobalt atoms and thereby impeding their agglomeration. The presence of SiO2 during high-temperature pyrolysis is proven crucial to create mesoporosity and a high BET area and pore volume in the N-doped carbon support (1780 m2 g−1, 1.54 cm3 g−1). This heterogeneous Co@mesoNC catalyst displays high activity and selectivity (>99%) for the selective hydrogenation of nitrobenzene to aniline at mild conditions (0.5–3 MPa, 343–383 K). When more challenging substrates (functionalized nitroarenes) are hydrogenated, the catalyst Co@mesoNC displays an excellent chemoselectivity to the corresponding substituted anilines.The presence of mesoporosity improves mass transport of reactants and/or products and the accessibility of the active Co-Nx sites, and greatly reduces deactivation due to fouling.

  19. Single cobalt sites in mesoporous N-doped carbon matrix for selective catalytic hydrogenation of nitroarenes

    KAUST Repository

    Sun, Xiaohui; Olivos-Suarez, Alma I.; Osadchii, Dmitrii; Romero, Maria Jose Valero; Kapteijn, Freek; Gascon, Jorge

    2017-01-01

    A supported cobalt catalyst with atomically dispersed Co-Nx sites (3.5 wt% Co) in a mesoporous N-doped carbon matrix (named Co@mesoNC) is synthesized by hydrolysis of tetramethyl orthosilicate (TMOS) in a Zn/Co bimetallic zeolitic imidazolate framework (BIMZIF(Co,Zn)), followed by high-temperature pyrolysis and SiO2 leaching. A combination of TEM, XRD XPS and X-ray absorption spectroscopy studies confirm the absence of cobalt nanoparticles and indicate that these highly dispersed cobalt species are present in the form of Co-Nx. The exclusive formation of Co-Nx sites in the carbon matrix is attributed to the presence of a large amount of Zn and N in the BIMZIF precursor together with the presence of SiO2 in the pore space of this framework, extending the initial spatial distance between cobalt atoms and thereby impeding their agglomeration. The presence of SiO2 during high-temperature pyrolysis is proven crucial to create mesoporosity and a high BET area and pore volume in the N-doped carbon support (1780 m2 g−1, 1.54 cm3 g−1). This heterogeneous Co@mesoNC catalyst displays high activity and selectivity (>99%) for the selective hydrogenation of nitrobenzene to aniline at mild conditions (0.5–3 MPa, 343–383 K). When more challenging substrates (functionalized nitroarenes) are hydrogenated, the catalyst Co@mesoNC displays an excellent chemoselectivity to the corresponding substituted anilines.The presence of mesoporosity improves mass transport of reactants and/or products and the accessibility of the active Co-Nx sites, and greatly reduces deactivation due to fouling.

  20. Fast humidity sensors based on CeO2 nanowires

    International Nuclear Information System (INIS)

    Fu, X Q; Wang, C; Yu, H C; Wang, Y G; Wang, T H

    2007-01-01

    Fast humidity sensors are reported that are based on CeO 2 nanowires synthesized by a hydrothermal method. Both the response and recovery time are about 3 s, and are independent of the humidity. The sensitivity increases gradually as the humidity increases, and is up to 85 at 97% RH. The resistance decreases exponentially with increasing humidity, implying ion-type conductivity as the humidity sensing mechanism. A model based on the morphology and surface energy of the nanowires is given to explain these results further. Our experimental results indicate a pathway to improving the performance of humidity sensors

  1. High-performance and renewable supercapacitors based on TiO2 nanotube array electrodes treated by an electrochemical doping approach

    International Nuclear Information System (INIS)

    Wu, Hui; Li, Dongdong; Zhu, Xufei; Yang, Chunyan; Liu, Dongfang; Chen, Xiaoyuan; Song, Ye; Lu, Linfeng

    2014-01-01

    Although one-dimensional anodic TiO 2 nanotube arrays have shown promise as supercapacitor electrode materials, their poor electronic conductivity embarrasses the practical applications. Here, we develop a simple electrochemical doping method to significantly improve the electronic conductivity and the electrochemical performances of TiO 2 nanotube electrodes. These TiO 2 nanotube electrodes treated by the electrochemical hydrogenation doping (TiO 2 -H) exhibit a very high average specific capacitance of 20.08 mF cm −2 at a current density of 0.05 mA cm −2 , ∼20 times more than the pristine TiO 2 nanotube electrodes. The improved electrochemical performances can be attributed to ultrahigh conductivity of TiO 2 -H due to the introduction of interstitial hydrogen ions and oxygen vacancies by the doping. The supercapacitor device assembled by the doped electrodes delivers a specific capacitance of 5.42 mF cm −2 and power density of 27.66 mW cm −2 , on average, at the current density of 0.05 mA cm −2 . The device also shows an outstanding rate capability with 60% specific capacitance retained when the current density increases from 0.05 to 4.00 mA cm −2 . More interestingly, the electrochemical performances of the supercapacitor after cycling can be recovered by the same doping process. This strategy boosts the performances of the supercapacitor, especially cycling stability

  2. Nitrogen and sulfur co-doped graphene/carbon nanotube as metal-free electrocatalyst for oxygen evolution reaction: the enhanced performance by sulfur doping

    International Nuclear Information System (INIS)

    Zhao, Jujiao; Liu, Yanming; Quan, Xie; Chen, Shuo; Zhao, Huimin; Yu, Hongtao

    2016-01-01

    Highlights: • Metal-free 3D architecture N,S co-doped GR/CNT is prepared by a one-step method. • N,S co-doped GR/CNT exhibits good activity and stability for OER. • S doping is indicated beneficial for OER performance of metal-free catalysts. • The catalytic kinetics is highly correlated with the content of C-S-C structure. • 3D architecture composed of GR and CNT also contributes to the OER activity. - Abstract: Highly active metal-free electrocatalysts consisting of earth-abundant elements for oxygen evolution reaction (OER) are extremely desired for renewable energy technologies. Here we prepare the nitrogen and sulfur co-doped graphene/carbon nanotube (NS-GR/CNT) with 3D architecture by one-step hydrothermal method, which presents good performance for OER. The as-prepared NS-GR/CNT exhibits more negative onset potential and lower Tafel slope (0.56 V, 103 mV decade"−"1 vs. S.C.E. in 0.1 M KOH) compared to single N doped graphene/carbon nanotube (0.65 V, 285 mV decade"−"1), which indicates S doping can significantly enhance the OER performance. The X-ray photoelectron spectroscopy reveals that the thiophene-like S (C-S-C) is the dominant S species in all the S doped samples. NS-GR/CNT with C-S-C content of 0.26% has the Tafel slope of 151 mV decade"−"1 while the value for NS-GR/CNT with C-S-C content of 1.09% is 103 mV decade"−"1. The decreased Tafel slope demonstrates the catalytic kinetics are highly correlated with the content of C-S-C. Density functional theory calculations suggest that C-S-C may improve the catalytic kinetics by facilitating the adsorption of the OH"− intermediate. Besides, the 3D architecture composed of graphene and CNTs also contributes to the good performance and chronoamperometric measurement demonstrates the good durability of NS-GR/CNTs.

  3. Hydrogen retention and erosion behaviour of tungsten-doped carbon films (a-C:W)

    International Nuclear Information System (INIS)

    Sauter, Philipp Andre

    2012-01-01

    In this study tungsten-doped carbon films (a-C:W) were investigated with respect on hydrogen retention and erosion under deuterium (D) impact. a-C:W was used as model system for mixed layers, which will be deposited on the inner wall of the fusion reactor ITER. The erosion is lowered by the successive enrichment of tungsten at the surface and only mildly depends on the dopant concentration and the temperature. The hydrogen retention is determined by the diffusion of D into depth, which increases with temperature. The resulting successive accumulation of D in a-C:W is insensitive on enrichment for high fluences and in line with the accumulation of D in C.

  4. Calcium decorated and doped phosphorene for gas adsorption

    Energy Technology Data Exchange (ETDEWEB)

    Lalitha, Murugan; Nataraj, Yuvarani; Lakshmipathi, Senthilkumar, E-mail: lsenthilkumar@buc.edu.in

    2016-07-30

    Highlights: • Phosphorene exhibits n-type/p-type nature on decorating/doping calcium respectively. • Gas molecules (CH{sub 4}, CO{sub 2}, H{sub 2} and NH{sub 3}) are physisorbed on phosphorene. • Ca decorated Phosphorene is recommended for high density hydrogen storage applications. • Calcium doping on zigzag and armchair sites makes phosphorene more reactive. • CH{sub 4}, CO{sub 2}, H{sub 2} prefer Ca-doped on zigzag1 site, whereas ammonia prefers Ca-doped on armchair. - Abstract: In this paper, we present the results from first-principles study based on the electronic structure and adsorption characteristics of CH{sub 4}, CO{sub 2}, H{sub 2} and NH{sub 3} adsorbed on Ca decorated/doped phosphorene. Our study finds that phosphorene exhibits n-type behaviour on decorating calcium, and p-type on doping calcium. Gas molecules are physisorbed on both pristine and calcium-mediated phosphorene, visible through their lower binding energy and charge transfer values. Ca decorated phosphorene is suitable for hydrogen storage due to its higher binding energy for H{sub 2}. Ca doped structures shows increased binding affinity towards CH{sub 4} and NH{sub 3} in zigzag1 direction and armchair directions respectively. The extracts of our study implies that Ca doped phosphorene possess increased binding affinity towards gas molecules, and the results are highly helpful for gas adsorption and to design gas sensors based on calcium doped or decorated phosphorene.

  5. Controllable Electrochemical Activities by Oxidative Treatment toward Inner-Sphere Redox Systems at N-Doped Hydrogenated Amorphous Carbon Films

    Directory of Open Access Journals (Sweden)

    Yoriko Tanaka

    2012-01-01

    Full Text Available The electrochemical activity of the surface of Nitrogen-doped hydrogenated amorphous carbon thin films (a-CNH, N-doped DLC toward the inner sphere redox species is controllable by modifying the surface termination. At the oxygen plasma treated N-doped DLC surface (O-DLC, the surface functional groups containing carbon doubly bonded to oxygen (C=O, which improves adsorption of polar molecules, were generated. By oxidative treatment, the electron-transfer rate for dopamine (DA positively charged inner-sphere redox analyte could be improved at the N-doped DLC surface. For redox reaction of 2,4-dichlorophenol, which induces an inevitable fouling of the anode surface by forming passivating films, the DLC surfaces exhibited remarkably higher stability and reproducibility of the electrode performance. This is due to the electrochemical decomposition of the passive films without the interference of oxygen evolution by applying higher potential. The N-doped DLC film can offer benefits as the polarizable electrode surface with the higher reactivity and higher stability toward inner-sphere redox species. By making use of these controllable electrochemical reactivity at the O-DLC surface, the selective detection of DA in the mixed solution of DA and uric acid could be achieved.

  6. Enhanced surface transfer doping of diamond by V{sub 2}O{sub 5} with improved thermal stability

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Kevin G., E-mail: k.crawford.2@research.gla.ac.uk; Moran, David A. J. [School of Engineering, University of Glasgow, Glasgow G12 8LT (United Kingdom); Cao, Liang [High Magnetic Field Laboratory, Chinese Academy of Sciences, 350 Shushanhu Road, Hefei 230031, Anhui (China); Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, Singapore 117542 (Singapore); Qi, Dongchen, E-mail: d.qi@latrobe.edu.au [Department of Chemistry and Physics, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria 3086 (Australia); Tallaire, Alexandre [LSPM-CNRS, Université Paris 13, Villetaneuse 93430 (France); Limiti, E.; Verona, C. [Department of Industrial Engineering, “Tor Vergata” University, Rome 00173 (Italy); Wee, Andrew T. S. [Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, Singapore 117542 (Singapore)

    2016-01-25

    Surface transfer doping of hydrogen-terminated diamond has been achieved utilising V{sub 2}O{sub 5} as a surface electron accepting material. Contact between the oxide and diamond surface promotes the transfer of electrons from the diamond into the V{sub 2}O{sub 5} as revealed by the synchrotron-based high resolution photoemission spectroscopy. Electrical characterization by Hall measurement performed before and after V{sub 2}O{sub 5} deposition shows an increase in hole carrier concentration in the diamond from 3.0 × 10{sup 12} to 1.8 × 10{sup 13 }cm{sup −2} at room temperature. High temperature Hall measurements performed up to 300 °C in atmosphere reveal greatly enhanced thermal stability of the hole channel produced using V{sub 2}O{sub 5} in comparison with an air-induced surface conduction channel. Transfer doping of hydrogen-terminated diamond using high electron affinity oxides such as V{sub 2}O{sub 5} is a promising approach for achieving thermally stable, high performance diamond based devices in comparison with air-induced surface transfer doping.

  7. Evidence for oxygen vacancy manipulation in La1/3Sr2/3FeO3− thin films via voltage controlled solid-state ionic gating

    Directory of Open Access Journals (Sweden)

    A. L. Krick

    2017-04-01

    Full Text Available Reversible changes of the structural and electronic transport properties of La1/3Sr2/3FeO3-δ/Gd-doped CeO2 heterostructures arising from the manipulation of δ are presented. Thermally induced oxygen loss leads to a c-axis lattice expansion and an increase in resistivity in a La1/3Sr2/3FeO3-δ film capped with Gd-doped CeO2. In a three-terminal device where a gate bias is applied across the Gd-doped CeO2 layer to alter the La1/3Sr2/3FeO3-δ oxygen stoichiometry, the ferrite channel is shown to undergo a change in resistance of an order of magnitude using gate voltages of less than 1 V applied at 500 K. The changes in resistance remain upon cooling to room temperature, in the absence of a gate bias, suggesting solid state ionic gating of perovskite oxides as a promising platform for applications in non-volatile, multistate devices.

  8. Hydrogenated indium oxide window layers for high-efficiency Cu(In,Ga)Se{sub 2} solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Jäger, Timo, E-mail: timo.jaeger@empa.ch; Romanyuk, Yaroslav E.; Nishiwaki, Shiro; Bissig, Benjamin; Pianezzi, Fabian; Fuchs, Peter; Gretener, Christina; Tiwari, Ayodhya N. [Empa – Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Thin Films and Photovoltaics, Überlandstrasse 129, 8600 Dübendorf (Switzerland); Döbeli, Max [ETH Zürich, Swiss Federal Institute of Technology, Laboratory of Ion Beam Physics, Otto-Stern-Weg 5, 8093 Zürich (Switzerland)

    2015-05-28

    High mobility hydrogenated indium oxide is investigated as a transparent contact for thin film Cu(In,Ga)Se{sub 2} (CIGS) solar cells. Hydrogen doping of In{sub 2}O{sub 3} thin films is achieved by injection of H{sub 2}O water vapor or H{sub 2} gas during the sputter process. As-deposited amorphous In{sub 2}O{sub 3}:H films exhibit a high electron mobility of ∼50 cm{sup 2}/Vs at room temperature. A bulk hydrogen concentration of ∼4 at. % was measured for both optimized H{sub 2}O and H{sub 2}-processed films, although the H{sub 2}O-derived film exhibits a doping gradient as detected by elastic recoil detection analysis. Amorphous IOH films are implemented as front contacts in CIGS based solar cells, and their performance is compared with the reference ZnO:Al electrodes. The most significant feature of IOH containing devices is an enhanced open circuit voltage (V{sub OC}) of ∼20 mV regardless of the doping approach, whereas the short circuit current and fill factor remain the same for the H{sub 2}O case or slightly decrease for H{sub 2}. The overall power conversion efficiency is improved from 15.7% to 16.2% by substituting ZnO:Al with IOH (H{sub 2}O) as front contacts. Finally, stability tests of non-encapsulated solar cells in dry air at 80 °C and constant illumination for 500 h demonstrate a higher stability for IOH-containing devices.

  9. Enzyme-free electrochemical immunosensor configured with Au-Pd nanocrystals and N-doped graphene sheets for sensitive detection of AFP.

    Science.gov (United States)

    Zhao, Lifang; Li, Songjun; He, Jing; Tian, Guihong; Wei, Qin; Li, He

    2013-11-15

    A novel electrochemical immunosensor capable of enzyme-free detection of alpha fetoprotein (AFP) is reported. This immunosensor was fabricated in a sandwich-like format where catalytic Au-Pd nanocrystals and highly conductive N-doped graphene sheets were incorporated. The significant catalysis by Au-Pd nanocrystals toward hydrogen peroxide, along with the increased electron transfer by graphene sheets, caused signal generation and increased sensitivity, which enables the enzyme-free detection of AFP. With a low detection limit at 0.005 ng mL(-1), this novel immunosensor worked well over the broad linear range of 0.05-30 ng mL(-1). Unlike previously reported enzyme-based electrochemical immunosensors, which often involve the complicated steps for enzyme loading and necessary treatments to keep the activity of enzyme, this novel immunosensor is simple in nature and employed catalytic Au-Pd nanoparticles and highly conductive graphene, which thus enables reliable and sensitive detection for clinic usage. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. PENGGUNAAN LEVERAGE PADA PERUSAHAAN: PERBEDAAN ANTARA CEO PRIA DAN WANITA

    Directory of Open Access Journals (Sweden)

    Farida Titik Kritanti

    2014-07-01

    Full Text Available AbstractVarious studies show that women are more risk averse in making decisions and better long-term oriented. Women would rather risk averse than men, making it less likely they will use debt in their capital structure, since by increasing debt increases the risk of the company's financial means. This study want to test whether gender became a significant factor in financial leverage, to see whether there are differences in policy between the company's leverage, led by men and women. Financial leverage is used as a measure of corporate risk because these variables can be changed by the CEO. Data from companies listed on the Jakarta Stock Exchange as sample. The results showed that there were differences in leverage between firms that have a men CEO with the women CEO of a company. Men CEO use more debt than the women CEO. But for the performance measured by ROI, obtained different results for the type of industry studied. For the consumer goods industry, there are performance differences between the men CEO and the women. But for the internet service industry and enamel kitchen showed no performance difference between women CEO with men CEO.Key words: leverage, woman CEO, man CEO, performanceAbstrakBerbagai penelitian menunjukkan bahwa wanita lebih risk averse dalam mengambil keputusan dan lebih berorientasi jangka panjang. Wanita lebih suka menolak risiko dibandingkan pria, sehingga kecil kemungkinan mereka akan menggunakan hutang dalam struktur modalnya, karena dengan menambah hutang berarti memperbesar risiko keuangan perusahaan. Penelitian ini ingin menguji apakah jender menjadi faktor yang cukup signifikan dalam financial leverage, dengan melihat apakah ada perbedaan dalam kebijakan leverage antara perusahaan yang dipimpin oleh pria dan wanita. Financial leverage dipakai sebagai ukuran risiko perusahaan karena variabel ini bisa diubah oleh CEO. Sampel menggunakan data dari perusahaan yang listed di Jakarta Stock Exchange. Hasil penelitian

  11. Probing the interaction of Rh, Co and bimetallic Rh-Co nanoparticles with the CeO2 support: catalytic materials for alternative energy generation.

    Science.gov (United States)

    Varga, E; Pusztai, P; Óvári, L; Oszkó, A; Erdőhelyi, A; Papp, C; Steinrück, H-P; Kónya, Z; Kiss, J

    2015-10-28

    The interaction of CeO2-supported Rh, Co and bimetallic Rh-Co nanoparticles, which are active catalysts in hydrogen production via steam reforming of ethanol, a process related to renewable energy generation, was studied by X-ray diffraction (XRD), high resolution electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and low energy ion scattering (LEIS). Furthermore, diffuse reflectance infrared spectroscopy (DRIFTS) of adsorbed CO as a probe molecule was used to characterize the morphology of metal particles. At small loadings (0.1%), Rh is in a much dispersed state on ceria, while at higher contents (1-5%), Rh forms 2-8 nm particles. Between 473-673 K pronounced oxygen transfer from ceria to Rh is observed and at 773 K significant agglomeration of Rh occurs. On reduced ceria, XPS indicates a possible electron transfer from Rh to ceria. The formation of smaller ceria crystallites upon loading with Co was concluded from XRD and HRTEM; for 10% Co, the CeO2 particle size decreased from 27.6 to 10.7 nm. A strong dissolution of Co into ceria and a certain extent of encapsulation by ceria were deduced by XRD, XPS and LEIS. In the bimetallic system, the presence of Rh enhances the reduction of cobalt and ceria. During thermal treatments, reoxidation of Co occurs, and Rh agglomeration as well as oxygen migration from ceria to Rh are hindered in the presence of cobalt.

  12. Effect of CeO2 on Microstructure and Wear Resistance of TiC Bioinert Coatings on Ti6Al4V Alloy by Laser Cladding

    Science.gov (United States)

    Wang, Haojun

    2017-01-01

    To solve the lack of wear resistance of titanium alloys for use in biological applications, various prepared coatings on titanium alloys are often used as wear-resistant materials. In this paper, TiC bioinert coatings were fabricated on Ti6Al4V by laser cladding using mixed TiC and ZrO2 powders as the basic pre-placed materials. A certain amount of CeO2 powder was also added to the pre-placed powders to further improve the properties of the TiC coatings. The effects of CeO2 additive on the phase constituents, microstructures and wear resistance of the TiC coatings were researched in detail. Although the effect of CeO2 on the phase constituents of the coatings was slight, it had a significant effect on the microstructure and wear resistance of the coatings. The crystalline grains in the TiC coatings, observed by a scanning electron microscope (SEM), were refined due to the effect of the CeO2. With the increase of CeO2 additive content in the pre-placed powders, finer and more compact dendrites led to improvement of the micro-hardness and wear resistance of the TiC coatings. Also, 5 wt % content of CeO2 additive in the pre-placed powders was the best choice for improving the wear properties of the TiC coatings. PMID:29301218

  13. Hydrogen plasma treatment for improved conductivity in amorphous aluminum doped zinc tin oxide thin films

    Directory of Open Access Journals (Sweden)

    M. Morales-Masis

    2014-09-01

    Full Text Available Improving the conductivity of earth-abundant transparent conductive oxides (TCOs remains an important challenge that will facilitate the replacement of indium-based TCOs. Here, we show that a hydrogen (H2-plasma post-deposition treatment improves the conductivity of amorphous aluminum-doped zinc tin oxide while retaining its low optical absorption. We found that the H2-plasma treatment performed at a substrate temperature of 50 °C reduces the resistivity of the films by 57% and increases the absorptance by only 2%. Additionally, the low substrate temperature delays the known formation of tin particles with the plasma and it allows the application of the process to temperature-sensitive substrates.

  14. Hydrogen plasma treatment for improved conductivity in amorphous aluminum doped zinc tin oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Masis, M., E-mail: monica.moralesmasis@epfl.ch; Ding, L.; Dauzou, F. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Jeangros, Q. [Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland); Hessler-Wyser, A. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Interdisciplinary Centre for Electron Microscopy, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne (Switzerland); Nicolay, S. [Centre Suisse d’Electronique et de Microtechnique (CSEM) SA, Rue Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland); Ballif, C. [Photovoltaics and Thin-Film Electronics Laboratory (PVLab), Institute of Microengineering (IMT), Ecole Polytechnique Fédérale de Lausanne - EPFL, Rue de la Maladière 71b, CH-2002 Neuchatel (Switzerland); Centre Suisse d’Electronique et de Microtechnique (CSEM) SA, Rue Jaquet-Droz 1, CH-2002 Neuchatel (Switzerland)

    2014-09-01

    Improving the conductivity of earth-abundant transparent conductive oxides (TCOs) remains an important challenge that will facilitate the replacement of indium-based TCOs. Here, we show that a hydrogen (H{sub 2})-plasma post-deposition treatment improves the conductivity of amorphous aluminum-doped zinc tin oxide while retaining its low optical absorption. We found that the H{sub 2}-plasma treatment performed at a substrate temperature of 50 °C reduces the resistivity of the films by 57% and increases the absorptance by only 2%. Additionally, the low substrate temperature delays the known formation of tin particles with the plasma and it allows the application of the process to temperature-sensitive substrates.

  15. Self-Template Synthesis of Hybrid Porous Co3 O4 -CeO2 Hollow Polyhedrons for High-Performance Supercapacitors.

    Science.gov (United States)

    Wei, Chengzhen; Liu, Kangfei; Tao, Jing; Kang, Xiaoting; Hou, Haiyan; Cheng, Cheng; Zhang, Daojun

    2018-01-04

    In this work, hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons have been successfully obtained via a simple cation-exchange route followed by heat treatment. In the synthesis process, ZIF-67 polyhedron frameworks are firstly prepared, which not only serve as a host for the exchanged Ce3 + ions but also act as the template for the synthesis of hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons. When utilized as electrode materials for supercapacitors, the hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons delivered a large specific capacitance of 1288.3 F g -1 at 2.5 A g -1 and a remarkable long lifespan cycling stability (<3.3 % loss after 6000 cycles). Furthermore, an asymmetric supercapacitor (ASC) device based on hybrid porous Co 3 O 4 -CeO 2 hollow polyhedrons was assembled. The ASC device possesses an energy density of 54.9 W h kg -1 , which can be retained to 44.2 W h kg -1 even at a power density of 5100 W kg -1 , indicating its promising application in electrochemical energy storage. More importantly, we believe that the present route is a simple and versatile strategy for the preparation of other hybrid metal oxides with desired structures, chemical compositions and applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Microstructural study of Ni/γ-Al2O3 catalyst: addition effects of CeO2 on carbon dioxide reforming of methane

    International Nuclear Information System (INIS)

    Valentini, Antoninho; Probst, Luiz Fernando Dias; Carreno, Neftali L. V.; Leite, Edson R.; Pontes, Fenelon M.; Longo, Elson; Schreiner, Wido H.; Lisboa-Filho, Paulo N.

    2003-01-01

    The carbon dioxide reforming of methane was carried out over nickel catalysts supported on the γ-Al 2 O 3 /CeO 2 system prepared by wet impregnation. With the increase of the Co2 weight in the catalyst, a higher stability was observed in the catalytic activity, together with an excellent resistance to carbon deposition and a better Ni dispersion. The catalysts were characterized by means of surface area measurements, TPR, H 2 chemisorption, XRD, SEM, EDX, XPS and TEM. An interaction between Ni and CeO 2 was observed to the Ni/CeO 2 sample after activation in a H 2 atmosphere above 300 deg C. Such behavior has a significantly influence on the catalytic activity. (author)

  17. Germination and early plant development of 10 plant species exposed to Nano TiO2 and CeO2

    Science.gov (United States)

    Ten agronomic plant species were exposed to different concentrations of nano-TiO2 or CeO2 (0, 250, 500 and 1000 ug/l) and followed to examine effects on germination and early seedling development. For TiO2, cabbage showed increased and corn decreased percent germination, while ...

  18. Development of natively textured surface hydrogenated Ga-doped ZnO-TCO thin films for solar cells via magnetron sputtering

    International Nuclear Information System (INIS)

    Wang, Fei; Chen, Xin-liang; Geng, Xin-hua; Zhang, De-kun; Wei, Chang-chun; Huang, Qian; Zhang, Xiao-dan; Zhao, Ying

    2012-01-01

    Highlights: ► Natively textured surface hydrogenated gallium-doped zinc oxide (HGZO) thin films have been deposited via magnetron sputtering on glass substrates. ► The directly deposited HGZO thin films present rough crater-type surface morphology. ► Typical HGZO thin film exhibits a high electron mobility of 41.3 cm 2 /V s and a relative low sheet resistance of ∼7.0 Ω. ► These HGZO thin films have high optical transmittances in the visible and near infrared region (∼380–1100 nm). ► A gradient H 2 growth method for fabricating HGZO thin films has been proposed in magnetron sputtering process. - Abstract: The main purposes are to obtain high quality transparent conductive oxide (TCO) based on zinc oxide (ZnO) thin films with high optical transparency in the visible and near infrared spectral range, high electrical conductivity and good light-scattering capability to enhance the path of the light inside the Si-based thin film solar cells. Natively textured surface hydrogenated gallium-doped ZnO (HGZO) thin films have been deposited via pulsed direct current (DC) magnetron sputtering on glass substrates at a substrate temperature of 553 K. These natively textured HGZO thin films exhibit high optical transmittance (over 80%) in the visible and near infrared region (λ = 380–1100 nm) and excellent electrical properties. The optimized HGZO thin film with crater-type textured surface obtained at the hydrogen flow rate of ∼2.0 sccm exhibits a high electron mobility of 41.3 cm 2 /V s and a relatively low sheet resistance of ∼7.0 Ω. The influences of hydrogen flow rates on the surface morphology, electrical and optical properties of HGZO thin films were investigated in detail. In addition, we put forward a method of gradient H 2 growth technique for fabricating HGZO thin films so as to obtain rough surface structure with good light-scattering capability and high electrical conductivity. “Crater-like” surface feature size and optical transmittance

  19. Metabolomic effects of CeO2, SiO2 and CuO metal oxide nanomaterials on HepG2 cells

    Science.gov (United States)

    To better assess potential hepatotoxicity of nanomaterials, human liver HepG2 cells were exposed for 3 days to five different CeO2 (either 30 or 100 μg/ml), 3 SiO2 based (30 μg/ml) or 1 CuO (3 μg/ml) nanomaterials with dry primary particle sizes ranging from 15 to 213 nm. Metabol...

  20. Purification of hydrogen under a free or combined form in a gaseous mixture, by chemical reactions with uranium

    International Nuclear Information System (INIS)

    Caron Charles, M.

    1988-03-01

    Within the framework of the european fusion program, we are dealing with the purification of hydrogen (tritium) under a free or combined form, from a H 2 , N 2 , NH 3 , CH 4 , O 2 , gaseous mixture. The process consists in cracking the hydrogenated molecules and absorbing the impurities by chemical reactions with uranium, without holding back hydrogen. In the temperature range: 950 K [fr

  1. Studies on various properties of pure and Li-doped Barium Hydrogen Phosphate (BHP) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Nallamuthu, D. [Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628216, Tamil Nadu (India); Selvarajan, P., E-mail: pselvarajanphy@yahoo.co.i [Department of Physics, Aditanar College of Arts and Science, Tiruchendur 628216, Tamil Nadu (India); Freeda, T.H. [Physics Research Centre, S.T. Hindu College, Nagercoil 629002 (India)

    2010-12-15

    Single crystals of pure and Li-doped barium hydrogen phosphate (BHP) were grown by solution method with gel technique. Various properties of the harvested crystals were studied by carrying out single crystal and powder XRD, FTIR, TG/DTA, microhardness and dielectric studies. Atomic absorption study was carried out for Li-doped BHP crystal to check the presence of Li dopants. Unit cell dimensions and diffracting planes of the grown crystals have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Density of the grown crystals was calculated using the XRD data. Thermal stability of the samples was checked by TG/DTA studies. Mechanical and dielectric characterizations of the harvested pure and Li-doped BHP crystals reveal the mechanical strength and ferroelectric transition. The observed results are reported and discussed.

  2. CEO Power, Corporate Tax Avoidance and Tax Aggressiveness

    OpenAIRE

    GATOT SOEPRIYANTO

    2017-01-01

    My thesis investigates the association between CEO power, corporate tax avoidance and tax aggressiveness, using two organizational theory perspectives: self-interest and stewardship. I find that a powerful CEO engages in less corporate tax avoidance activities, which lends credence to the risk minimization motive of the stewardship perspective. My findings on the association between CEO power and tax aggressiveness show that powerful CEOs avoid risky tax avoidance strategies that expose a fir...

  3. Structural, optical and electrical properties of CeO2 thin films simultaneously prepared by anodic and cathodic electrodeposition

    Science.gov (United States)

    Yang, Yumeng; Du, Xiaoqing; Yi, Chenxi; Liu, Jiao; Zhu, Benfeng; Zhang, Zhao

    2018-05-01

    CeO2 thin films were deposited on stainless steel (SS) and indium tin oxide (ITO)-coated glass by simultaneous anodic and cathodic electrodeposition, and the influence of negative potential on the formation of ceria films was studied with scanning electron microscopy, X-ray diffraction, Raman spectroscopy, van der Pauw measurements, UV-visible spectroscopy and X-ray photoelectron spectroscopy. The results show that CeO2 films on the anode are slightly affected by the potential, but the particle size, crystal orientation, strain, film thickness, resistivity and Ce(III) content of the films on the cathode increases with increasing potential on the SS substrate. Contradictory to the results of the SS cathode, redshift (Ed changed from 3.95 eV to 3.56 eV and Ei changed from 3.42 eV to 3.04 eV) occurring in the absorption spectrum of CeO2 deposited on the ITO-coated glass cathode indicates that the content of Ce3+ in the cathodic films is dependent on the adopted substrates and decreases as the applied potential is increased.

  4. CEO age and gender: Subsequent market performance

    Directory of Open Access Journals (Sweden)

    Marcelo Eduardo

    2016-12-01

    Full Text Available The issue of CEO age and gender vs. concurrent performance is extensively examined, but the association with subsequent performance has limited treatment in the financial literature, and with conflicting findings. In the current study, we examine the association between CEO age and gender, and subsequent company market performance using a more recent set of observations and the standard four-factor model to estimate future cumulative abnormal shareholder returns. We find that subsequent abnormal shareholder returns are marginally significantly higher for female CEOs than for their male counterparts, but no material pattern is observed between CEO age and subsequent abnormal shareholder return performance.

  5. Exposure of agricultural crops to nanoparticle CeO2 in biochar-amended soil.

    Science.gov (United States)

    Servin, Alia D; De la Torre-Roche, Roberto; Castillo-Michel, Hiram; Pagano, Luca; Hawthorne, Joseph; Musante, Craig; Pignatello, Joseph; Uchimiya, Minori; White, Jason C

    2017-01-01

    Biochar is seeing increased usage as an amendment in agricultural soils but the significance of nanoscale interactions between this additive and engineered nanoparticles (ENP) remains unknown. Corn, lettuce, soybean and zucchini were grown for 28 d in two different soils (agricultural, residential) amended with 0-2000 mg engineered nanoparticle (ENP) CeO 2  kg -1 and biochar (350 °C or 600 °C) at application rates of 0-5% (w/w). At harvest, plants were analyzed for biomass, Ce content, chlorophyll and lipid peroxidation. Biomass from the four species grown in residential soil varied with species and biochar type. However, biomass in the agricultural soil amended with biochar 600 °C was largely unaffected. Biochar co-exposure had minimal impact on Ce accumulation, with reduced or increased Ce content occurring at the highest (5%) biochar level. Soil-specific and biochar-specific effects on Ce accumulation were observed in the four species. For example, zucchini grown in agricultural soil with 2000 mg CeO 2  kg -1 and 350 °C biochar (0.5-5%) accumulated greater Ce than the control. However, for the 600 °C biochar, the opposite effect was evident, with decreased Ce content as biochar increased. A principal component analysis showed that biochar type accounted for 56-99% of the variance in chlorophyll and lipid peroxidation across the plants. SEM and μ-XRF showed Ce association with specific biochar and soil components, while μ-XANES analysis confirmed that after 28 d in soil, the Ce remained largely as CeO 2 . The current study demonstrates that biochar synthesis conditions significantly impact interactions with ENP, with subsequent effects on particle fate and effects. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  6. Radiation resistance of GeO2-doped silica core optical fibers

    International Nuclear Information System (INIS)

    Shibata, Shuichi; Nakahara, Motohiro; Omori, Yasuharu

    1985-01-01

    Effects of hlogen addition to silica glass on the loss in optical fibers are examined by using halogen-free, chlorine-containing and fluorine-containing GeO 2 -doped silica core optical fibers. Measurements are made for dependence of induced loss in these optical fibers on various factors such as wavelength and total dose of gamma radiation as well as GeO 2 content. Ultraviolet absorption spectra are also observed. In addition, effects of halogens added to pure silica fibers are considered on the basis of Raman spectra of three different optical fibers (pure, F-doped, and F- and GeO 2 -codoped silica core). Thus, it is concluded that (1) addition of halogens (F and Cl) serves to decrease GeO defects and Ge(3) defects in GeO 2 -doped silica optical fibers ; (2) addition of halogens suppresses the increase in loss in GeO 2 -doped silica optical fibers induced by gamma radiation ; and (3) there are close relations between the increase in loss induced by gamma radiation and defects originally existing in the fibers. Effects of halogens added to GeO 2 -doped and pure silica optical fibers can be explained on the basis of the latter relations. (Nogami, K.)

  7. Thermal Behavior and Hydrogen Production of Methanol Autothermal Reforming Performed Using Oxygen Enrichment and Cu/ZnO/Al2O3/Cr2O3/CeO2 Catalyst

    Directory of Open Access Journals (Sweden)

    Donny Lesmana

    2015-07-01

    Full Text Available A fixed-bed reactor designed for the autothermal reforming (ATR of methanol under adiabatic conditions was constructed to experimentally determine the profile of temperature and catalyst activity generated using the Cu/ZnO/Al2O3/Cr2O3/CeO2 catalyst. The effect of oxygen enrichment in this experiment was investigated, and the experimental results showed that an increase in oxygen concentration correlated with an increase in the temperature of the catalytic bed; by contrast, this increase in oxygen concentration resulted in a reduction of the startup time of the catalyst. Moreover, the reaction temperature was determined to vary with the position within the catalytic fixed bed. © 2015 BCREC UNDIP. All rights reservedReceived: 29th August 2014; Revised: 19th March 2015; Accepted: 19th March 2015

  8. Tunable and selective hydrogenation of furfural to furfuryl alcohol and cyclopentanone over Pt supported on biomass-derived porous heteroatom doped carbon.

    Science.gov (United States)

    Liu, Xiuyun; Zhang, Bo; Fei, Benhua; Chen, Xiufang; Zhang, Junyi; Mu, Xindong

    2017-09-21

    The search for and exploitation of efficient catalytic systems for selective conversion of furfural into various high value-added chemicals remains a huge challenge for green synthesis in the chemical industry. Here, novel Pt nanoparticles supported on bamboo shoot-derived porous heteroatom doped carbon materials were designed as highly active catalysts for controlled hydrogenation of furfural in aqueous media. The porous heteroatom doped carbon supported Pt catalysts were endowed with a large surface area with a hierarchical porous structure, a high content of nitrogen and oxygen functionalities, a high dispersion of the Pt nanoparticles, good water dispersibility and reaction stability. Benefiting from these features, the novel Pt catalysts displayed a high activity and controlled tunable selectivity for furfural hydrogenation to produce furfuryl alcohol and cyclopentanone in water. The product selectivity could be easily modulated by controlling the carbonization temperature of the porous heteroatom doped carbon support and the reaction conditions (temperature and H 2 pressure). Under mild conditions (100 °C, 1 MPa H 2 ), furfuryl alcohol was obtained in water with complete conversion of the furfural and an impressive furfuryl alcohol selectivity of >99% in the presence of Pt/NC-BS-500. A higher reaction temperature, in water, favored rearrangement of the furfural (FFA) with Pt/NC-BS-800 as the catalyst, which resulted in a high cyclopentanone yield of >76% at 150 °C and 3 MPa H 2 . The surface properties and pore structure of the heteroatom doped carbon support, adjusted using the carbonization temperature, might determine the interactions between the Pt nanoparticles, carbon support and catalytic reactants in water, which in turn could have led to a good selectivity control. The effect of different reaction temperatures and reaction times on the product selectivity was also explored. Combined with exploration of the distribution of the reaction products, a

  9. Microwave-assisted self-doping of TiO2 photonic crystals for efficient photoelectrochemical water splitting

    KAUST Repository

    Zhang, Zhonghai

    2014-01-08

    In this article, we report that the combination of microwave heating and ethylene glycol, a mild reducing agent, can induce Ti3+ self-doping in TiO2. A hierarchical TiO2 nanotube array with the top layer serving as TiO2 photonic crystals (TiO2 NTPCs) was selected as the base photoelectrode. The self-doped TiO2 NTPCs demonstrated a 10-fold increase in visible-light photocurrent density compared to the nondoped one, and the optimized saturation photocurrent density under simulated AM 1.5G illumination was identified to be 2.5 mA cm-2 at 1.23 V versus reversible hydrogen electrode, which is comparable to the highest values ever reported for TiO2-based photoelectrodes. The significant enhancement of photoelectrochemical performance can be ascribed to the rational coupling of morphological and electronic features of the self-doped TiO 2 NTPCs: (1) the periodically morphological structure of the photonic crystal layer traps broadband visible light, (2) the electronic interband state induced from self-doping of Ti3+ can be excited in the visible-light region, and (3) the captured light by the photonic crystal layer is absorbed by the self-doped interbands. © 2013 American Chemical Society.

  10. Recent progresses in the understanding of the elastic and anelastic properties of H-free, H-doped and H-contaminated NiTi based alloys

    Directory of Open Access Journals (Sweden)

    Giovanni Mazzolai

    2011-12-01

    Full Text Available This review is focused on the influence of interstitial hydrogen and alloy compositional changes on the internal friction (IF spectrum and elastic Young's modulus (E of NiTi based shape memory alloys. In the martensitically transforming binary alloys Ni50+xTi50-x (x≤1.3 vacuum annealed and furnace cooled (H-free, besides the well known IF peak associated with the martensitic transition two additional non-thermally activated peaks (P150K and P200K′ are present due to some sort of second-order phase transitions. In martensitically transforming Ni50+xTi50-x and Ti50Ni50-yCuy alloys doped with hydrogen two thermally activated peaks, PTWH and PH, appear which originate from stress-assisted motions of H-twin boundary complexes and isolated H-elastic dipoles (Snoek effect, respectively. In a H-free martensitically non-trasforming alloy (x=2, besides the non-thermally activated peak P150K, a frequency dependent dip is observed in the E(T curves at a temperature Tg. This dip is similar to that reported in the literature for two other non-transforming alloys (x=1.5 and x=2.5, which, however, were also found to exhibit a thermally activated IF peak just below Tg. Most likely, these two alloys were contaminated with hydrogen during the preliminary solubilization in argon atmosphere and subsequent water quenching treatments given to them. The Young's modulus dip and the lower temperature IF peak have been both attributed to a novel type of phase transition reported in the literature as “strain glass transition”. The introduction of hydrogen into the non-transforming alloy with x=2 enhances the Young's modulus dip and gives rise to the H-Snoek peak PH just below Tg, which clearly appears to be the counterpart of the peak observed in the alloys (x=1.5 and x=2.5 solubilized in argon atmosphere and water quenched. The conclusion was reached in the present work that this last peak is not related to the strain glass transition but is rather an H

  11. Hydrogen-induced strain localisation in oxygen-free copper in the initial stage of plastic deformation

    Science.gov (United States)

    Yagodzinskyy, Yuriy; Malitckii, Evgenii; Tuomisto, Filip; Hänninen, Hannu

    2018-03-01

    Single crystals of oxygen-free copper oriented to easy glide of dislocations were tensile tested in order to study the hydrogen effects on the strain localisation in the form of slip bands appearing on the polished specimen surface under tensile straining. It was found that hydrogen increases the plastic flow stress in Stage I of deformation. The dislocation slip localisation in the form of slip bands was observed and analysed using an online optical monitoring system and atomic force microscopy. The fine structure of the slip bands observed with AFM shows that they consist of a number of dislocation slip offsets which spacing in the presence of hydrogen is markedly reduced as compared to that in the hydrogen-free specimens. The tensile tests and AFM observations were accompanied with positron annihilation lifetime measurements showing that straining of pure copper in the presence of hydrogen results in free volume generation in the form of vacancy complexes. Hydrogen-enhanced free-volume generation is discussed in terms of hydrogen interactions with edge dislocation dipoles forming in double cross-slip of screw dislocations in the initial stage of plastic deformation of pure copper.

  12. Selective hydrogenation of phenol to cyclohexanone over Pd@CN (N-doped porous carbon): Role of catalyst reduction method

    Science.gov (United States)

    Hu, Shuo; Yang, Guangxin; Jiang, Hong; Liu, Yefei; Chen, Rizhi

    2018-03-01

    Selective phenol hydrogenation is a green and sustainable technology to produce cyclohexanone. The work focused on investigating the role of catalyst reduction method in the liquid-phase phenol hydrogenation to cyclohexanone over Pd@CN (N-doped porous carbon). A series of reduction methods including flowing hydrogen reduction, in-situ reaction reduction and liquid-phase reduction were designed and performed. The results highlighted that the reduction method significantly affected the catalytic performance of Pd@CN in the liquid-phase hydrogenation of phenol to cyclohexanone, and the liquid-phase reduction with the addition of appropriate amount of phenol was highly efficient to improve the catalytic activity of Pd@CN. The influence mechanism was explored by a series of characterizations. The results of TEM, XPS and CO chemisorption confirmed that the reduction method mainly affected the size, surface composition and dispersion of Pd in the CN material. The addition of phenol during the liquid-phase reduction could inhibit the aggregation of Pd NPs and promote the reduction of Pd (2+), and then improved the catalytic activity of Pd@CN. The work would aid the development of high-performance Pd@CN catalysts for selective phenol hydrogenation.

  13. From melamine sponge towards 3D sulfur-doping carbon nitride as metal-free electrocatalysts for oxygen reduction reaction

    Science.gov (United States)

    Xu, Jingjing; Li, Bin; Li, Songmei; Liu, Jianhua

    2017-07-01

    Development of new and efficient metal-free electrocatalysts for replacing Pt to improve the sluggish kinetics of oxygen reduction reaction (ORR) is of great importance to emerging renewable energy technologies such as metal-air batteries and polymer electrolyte fuel cells. Herein, 3D sulfur-doping carbon nitride (S-CN) as a novel metal-free ORR electrocatalyst was synthesized by exploiting commercial melamine sponge as raw material. The sulfur atoms were doping on CN networks uniformly through numerous S-C bonds which can provide additional active sites. And it was found that the S-CN exhibited high catalytic activity for ORR in term of more positive onset potential, higher electron transfer number and higher cathodic density. This work provides a novel choice of metal-free ORR electrocatalysts and highlights the importance of sulfur-doping CN in metal-free ORR electrocatalysts.

  14. Enhanced stability of Zr-doped Ba(CeTb)O(3-δ)-Ni cermet membrane for hydrogen separation.

    Science.gov (United States)

    Wei, Yanying; Xue, Jian; Fang, Wei; Chen, Yan; Wang, Haihui; Caro, Jürgen

    2015-07-25

    A mixed protonic and electronic conductor material BaCe(0.85)Tb(0.05)Zr(0.1)O(3-δ) (BCTZ) is prepared and a Ni-BCTZ cermet membrane is synthesized for hydrogen separation. Stable hydrogen permeation fluxes can be obtained for over 100 h through the Ni-BCTZ membrane in both dry and humid conditions, which exhibits an excellent stability compared with Ni-BaCe(0.95)Tb(0.05)O(3-δ) membrane due to the Zr doping.

  15. Committee on Earth Observation Satellites (CEOS) perspectives about the GEO Supersite initiative

    Science.gov (United States)

    Lengert, Wolfgang; Zoffoli, Simona; Giguere, Christine; Hoffmann, Joern; Lindsay, Francis; Seguin, Guy

    2014-05-01

    This presentation is outlining the effort of the Committee on Earth Observation Satellites (CEOS) using its global collaboration structure to support implementing the GEO priority action DI-01 Informing Risk Management and Disaster Reduction addressing the component: C2 Geohazards Monitoring, Alert, and Risk Assessment. A CEOS Supersites Coordination Team (SCT) has been established in order to make best use of the CEOS global satellite resources. For this, the CEOS SCT has taken a holistic view on the science data needs and availability of resources, considering the constraints and exploitation potentials of synergies. It is interfacing with the Supersites Science Advisory Group and the Principle Investigators to analyze how the satellite data associated with seismic and Global Navigation Satellite System (GNSS) data can support national authorities and policy makers in risk assessment and the development of mitigation strategies. CEOS SCT aims to support the establishment of a fully integrated approach to geohazards monitoring, based on collaboration among existing networks and international initiatives, using new instrumentation such as in-situ sensors, and aggregating space (radar, optical imagery) and ground-based (subsurface) observations. The three Supersites projects which are funded under the EC FP7 action, namely (i) FUTUREVOLC: A European volcanological supersite in Iceland: a monitoring system and network for the future Geohazards Monitoring, Alert, and Risk Assessment, (ii) MARsite: New Directions in Seismic Hazard assessment through Focused Earth Observation in the Marmara Supersite, (iii) MED-SUV: MEDiterranean Volcanoes and related seismic risks, have been examined as a vehicle to fulfill these ambitious objectives. FUTUREVOLC has already been granted CEOS support. This presentation will outline CEOS agreed process and criteria applied by the Supersites Coordination Team (SCT), for selecting these Supersites in the context of the GSNL initiative, as

  16. High-Performance Doping-Free Hybrid White OLEDs Based on Blue Aggregation-Induced Emission Luminogens.

    Science.gov (United States)

    Liu, Baiquan; Nie, Han; Lin, Gengwei; Hu, Shiben; Gao, Dongyu; Zou, Jianhua; Xu, Miao; Wang, Lei; Zhao, Zujin; Ning, Honglong; Peng, Junbiao; Cao, Yong; Tang, Ben Zhong

    2017-10-04

    Doping-free white organic light-emitting diodes (DF-WOLEDs) have aroused research interest because of their simple properties. However, to achieve doping-free hybrid WOLEDs (DFH-WOLEDs), avoiding aggregation-caused quenching is challenging. Herein, blue luminogens with aggregation-induced emission (AIE) characteristics, for the first time, have been demonstrated to develop DFH-WOLEDs. Unlike previous DFH-WOLEDs, both thin (10 nm) AIE luminogen (AIEgen) can be used for devices, enhancing the flexibility. Two-color devices show (i) pure-white emission, (ii) high CRI (85), and (iii) high efficiency. Particularly, 19.0 lm W 1- is the highest for pure-white DF-WOLEDs, while 35.0 lm W 1- is the best for two-color hybrid WOLEDs with CRI ≥ 80. A three-color DFH-WOLED shows broad color-correlated temperature span (2301-11628 K), (i) the first sunlight-like OLED (2500-8000 K) operating at low voltages, (ii) the broadest span among sunlight-like OLED, and (iii) possesses comparable efficiency with the best doping counterpart. Another three-color DFH-WOLED exhibits CRI > 90 at ≥3000 cd m -2 , (i) the first DF-WOLED with CRI ≥ 90 at high luminances, and (ii) the CRI (92.8) is not only the highest among AIE-based WOLEDs but also the highest among DF-WOLEDs. Such findings may unlock an alternative concept to develop DFH-WOLEDs.

  17. Characterization of hollow cathode fall field strength measured by Doppler-free two-photon optogalvanic spectroscopy via Stark splitting of the 2S level of hydrogen and deuterium

    Energy Technology Data Exchange (ETDEWEB)

    Perez, C; De la Rosa, M I; Gruetzmacher, K, E-mail: concha@opt.uva.e [Universidad de Valladolid, Facultad de Ciencias, 47071 Valladolid (Spain)

    2010-05-01

    Doppler-free two-photon optogalvanic spectroscopy has been applied to measure the strong electric field strength and the cathode fall characteristics of hollow cathode discharges operated in hydrogen and deuterium via the Stark splitting of the 2S level of atomic hydrogen isotopes. In this paper we show similarities and differences in the tendencies of the cathode fall characteristics of hydrogen and deuterium in a wide range of identical discharge parameters.

  18. Characterization of hollow cathode fall field strength measured by Doppler-free two-photon optogalvanic spectroscopy via Stark splitting of the 2S level of hydrogen and deuterium

    International Nuclear Information System (INIS)

    Perez, C; De la Rosa, M I; Gruetzmacher, K

    2010-01-01

    Doppler-free two-photon optogalvanic spectroscopy has been applied to measure the strong electric field strength and the cathode fall characteristics of hollow cathode discharges operated in hydrogen and deuterium via the Stark splitting of the 2S level of atomic hydrogen isotopes. In this paper we show similarities and differences in the tendencies of the cathode fall characteristics of hydrogen and deuterium in a wide range of identical discharge parameters.

  19. Blood conservation: the CEO perspective.

    Science.gov (United States)

    Morgan, Timothy O

    2004-08-01

    Hospital CEOs are concerned about more than just cost of services to their patients. The advancement of patient car along with maintaining or improving patient safety are also key elements to the CEO, to limit patient risks, hospital liability, and negative public relations. The CEO is accountable to the hospital staff, the patients, and the general public. Establishing programs such as blood management or bloodless medicine can be implemented by using a team approach. A physician champion with a clear business plan that addresses all issues and challenges is critical for successful implementation. As blood and blood product costs rise and supply decreases, alternatives such as cell saving techniques and the use of pharmacologic interventions can have a significant impact on net hospital expenditures.

  20. Exploring Corporate Rhetoric: Metadiscourse in the CEO's Letter.

    Science.gov (United States)

    Hyland, Ken

    1998-01-01

    Examines how metadiscourse is used to create a positive corporate image in 137 CEOs' letters, showing how CEOs use nonpropositional material to realize rational, credible, and affective appeals. Reveals the essentially rhetorical nature of CEOs' letters by comparing the frequency and distribution of metadiscourse in their letters and directors'…

  1. Photocatalytic activity of Sulfer-doped TiO2 fiber under visible light illumination (Joint research)

    International Nuclear Information System (INIS)

    Takeyama, Akinori; Yamamoto, Shunya; Yoshikawa, Masahito; Hasegawa, Yoshio; Awatsu, Satoshi

    2007-03-01

    The Sol-Gel derived precursor fiber was annealed under hydrogen disulfeid (H 2 S) following oxygen atmosphere, Sulfur-doped TiO 2 fiber was obtained. Crystal structure of the fiber was identified as anatase phase of TiO 2 . The energy band gap of the fiber was narrower by about 0.06 eV than that of anatase, which showed that it could absorb visible light. The fiber contains about 0.58 atomic % of Sulfur, and they located at the oxygen lattice site of TiO 2 . Under visible light illumination, the fiber degraded Trichloroethylen (TCE) and produced carbon dioxide (CO 2 ). This shows Sulfur-doped TiO 2 fiber has the photocatalytic activity under visible light illumination. (author)

  2. Hydrogenated TiO{sub 2} film for enhancing photovoltaic properties of solar cells and self-sensitized effect

    Energy Technology Data Exchange (ETDEWEB)

    He, Hongcai; Yang, Kui; Wang, Ning, E-mail: ning-wang@uestc.edu.cn; Luo, Feifei; Chen, Haijun [State Key Laboratory of Electronic Thin Films and Integrated Devices and School of Microelectronics and Solid-State Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2013-12-07

    Hydrogenated TiO{sub 2} film was obtained by annealing TiO{sub 2} film at 350 °C for 2 h with hydrogen, and TiO{sub 2} films were prepared by screen printing on fluorine-doped tin oxide glass. Structural characterization by X-ray diffraction and electron microscopy did not show obvious difference between hydrogenated TiO{sub 2} film and pristine TiO{sub 2} film. Through optical and electrochemical characterization, the hydrogenated TiO{sub 2} film showed enhanced absorption and narrowed band gap, as well as reduced TiO{sub 2} surface impedance and dark current. As a result, an obviously enhanced photovoltaic effect was observed in the solar cell with hydrogenated TiO{sub 2} as photoanode without adding any dye due to the self-sensitized effect of hydrogenated TiO{sub 2} film, which excited electrons injecting internal conduction band of TiO{sub 2} to generate more photocurrent.

  3. Hydrogen Production by Steam Reforming of Ethanol on Rh-Pt Catalysts: Influence of CeO2, ZrO2, and La2O3 as Supports

    Directory of Open Access Journals (Sweden)

    Bernay Cifuentes

    2015-11-01

    Full Text Available CeO2-, ZrO2-, and La2O3-supported Rh-Pt catalysts were tested to assess their ability to catalyze the steam reforming of ethanol (SRE for H2 production. SRE activity tests were performed using EtOH:H2O:N2 (molar ratio 1:3:51 at a gaseous space velocity of 70,600 h−1 between 400 and 700 °C at atmospheric pressure. The SRE stability of the catalysts was tested at 700 °C for 27 h time on stream under the same conditions. RhPt/CeO2, which showed the best performance in the stability test, also produced the highest H2 yield above 600 °C, followed by RhPt/La2O3 and RhPt/ZrO2. The fresh and aged catalysts were characterized by TEM, XPS, and TGA. The higher H2 selectivity of RhPt/CeO2 was ascribed to the formation of small (~5 nm and stable particles probably consistent of Rh-Pt alloys with a Pt surface enrichment. Both metals were oxidized and acted as an almost constant active phase during the stability test owing to strong metal-support interactions, as well as the superior oxygen mobility of the support. The TGA results confirmed the absence of carbonaceous residues in all the aged catalysts.

  4. X-ray and neutron powder investigations of pure and yttrium doped CeO2 at temperatures up to 1600 K

    International Nuclear Information System (INIS)

    Berber, K.; Martin, U.; Mursic, Z.; Schneider, J.; Boysen, H.; Frey, F.

    1991-01-01

    Ceria, CeO 2 powders and sintermaterials with different amounts of yttria, Y 2 O 3 , (0-10 mole %) were investigated up to 1600 K by X-ray and neutron powder diffraction. In the sample with 3 mole % yttria the onset of a solid-state reaction or a kind of phase change at 900 K is indicated by a change of the lattice expansion coefficient and by an increase of the slope of the B iso (T) curve. Microstrains are present in the sintered material above 900 K. Anharmonic contributions to the temperature factor of the oxygens become significant at higher temperatures. We deduce from a non-zero part B T ≠0 some static disorder within the O-sublattice. Pdf-maps of the oxygens show clearly deformations of the 'normal' isotropic behaviour, but exceptional smearing out or even closed pathways are not observed. Thus, the superior anionic conductivity of this material is not reflected by the features of the averaged structure. It is most likely due to a disordered 'interface-structure' between ordered domains. A temperature dependent 'structured' background scattering supports this conclusion. (author) 6 figs., 9 refs

  5. L-Arginine-Triggered Self-Assembly of CeO2 Nanosheaths on Palladium Nanoparticles in Water.

    Science.gov (United States)

    Wang, Xiao; Zhang, Yibo; Song, Shuyan; Yang, Xiangguang; Wang, Zhuo; Jin, Rongchao; Zhang, Hongjie

    2016-03-24

    Pd@CeO2 core-shell nanostructures with a tunable Pd core size, shape, and nanostructure as well as a tunable CeO2 sheath thickness were obtained by a biomolecule-assisted method. The synthetic process is simple and green, as it involves only the heating of a mixture of Ce(NO3 )3 , l-arginine, and preformed Pd seeds in water without additives. Importantly, the synthesis is free of thiol groups and halide ions, thus providing a possible solution to the problem of secondary pollution by Pd nanoparticles in the sheath-coating process. The Pd/CeO2 nanostructures can be composited well with γ-Al2 O3 to create a heterogeneous catalyst. In subsequent tests of catalytic NO reduction by CO, Pd@CeO2 /Al2 O3 samples based on Pd cubes (6, 10, and 18 nm), Pd octahedra (6 nm), and Pd cuboctahedra (9 nm) as well as a simply loaded Pd cube (6 nm)-CeO2 /Al2 O3 sample were used as catalysts to investigate the effects of the Pd core size and shape and the hybrid nanostructure on the catalytic performance. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Influence of deposition conditions on electrical and mechanical properties of Sm2O3-doped CeO2 thin films prepared by EB-PVD (+IBAD) methods. Part 1: Effective relative permittivity

    Science.gov (United States)

    Hartmanová, Mária; Nádaždy, Vojtech; Kundracik, František; Mansilla, Catina

    2013-03-01

    Study is devoted to the effective relative permittivity ɛr of CeO2 + x. Sm2O3 thin films prepared by electron-beam physical vapour deposition and ionic beam-assisted deposition methods; ɛr was investigated by three independent ways from the bulk parallel capacitance Cp, impedance capacitance Cimp, and accumulation capacitance Cacc in dependence on the deposition conditions (deposition temperature, dopant amount x and Ar+ ion bombardment during the film deposition) used. Investigations were performed using impedance spectroscopy, capacitance-voltage and current-voltage characteristics as well as deep level transient spectroscopy. Results obtained are described and discussed.

  7. Nanocrystalline Ce 1- xY xO 2- x/2 (0≤ x≤0.35) Oxides via Carbonate Precipitation: Synthesis and Characterization

    Science.gov (United States)

    Li, Ji-Guang; Ikegami, Takayasu; Wang, Yarong; Mori, Toshiyuki

    2002-10-01

    A novel carbonate (co)precipitation method, employing nitrates as the starting salts and ammonium carbonate as the precipitant, has been used to synthesize nanocrystalline CeO 2 and Ce 1- xY xO 2- x/2 ( x≤0.35) solid-solutions. The resultant powders are characterized by elemental analysis, differential thermal analysis/thermogravimetry (DTA/TG), X-ray diffractometry (XRD), Brunauer-Emmett-Teller (BET) analysis, and high-resolution scanning electron microscopy (HRSEM). Due to the direct formation of carbonate solid-solutions during precipitation, Ce 1- xY xO 2- x/2 solid-solution oxides are formed directly during calcination at a very low temperature of ˜300°C for 2 h. The thus-produced oxide nanopowders are essentially non-agglomerated, as revealed by BET in conjunction with XRD analysis. The solubility of YO 1.5 in CeO 2 is determined via XRD to be somewhere in the range from 27 to 35 mol%, from which a Y 2O 3-related type-C phase appears in the final product. Y 3+-doping promotes the formation of spherical nanoparticles, retards thermal decomposition of the precursors, and suppresses significantly crystallite coarsening of the oxides during calcination. The activation energy for crystallite coarsening increases gradually from 68.7 kJ mol -1 for pure CeO 2 to 138.6 kJ mol -1 for CeO 2 doped with 35 mol% YO 1.5. The dopant effects on crystallite coarsening is elaborated from the view point of solid-state chemistry.

  8. Nb-doped TiO2 thin films as photocatalytic materials

    Indian Academy of Sciences (India)

    Administrator

    that hydrophilicity is ruled by a different mechanism than photocatalysis. Keywords. Nb-doped ... studied for a large area of applications: solar cells,1–3 hydrogen ... our previous work.12,13 Results show that all the films are amorphous and ...

  9. CEO Succession in Community Colleges: A Grounded Theory.

    Science.gov (United States)

    Kirkland, Travis P.

    Intended as part of a larger study of the effects of anticipated or unanticipated changes in the chief executive officer (CEO) of a community college, a case study approach was taken to gather primary data from a multi-campus, urban community college that had recently experienced a CEO succession. The study focused on the effects of the CEO change…

  10. Enhancement of H2-sensing Properties of F-doped SnO2 Sensorby Surface Modification with SiO2

    Directory of Open Access Journals (Sweden)

    S. P. Khatkar

    2006-05-01

    Full Text Available Effects of surface chemical modification with sodium silicate on the gas-sensingproperties of F-doped SnO2 gas sensor designed and fabricated employing micro-electromechanical system (MEMS technology were investigated. Gas sensing properties of thesensor were checked against combustible gases like H2, CO, CH4 and C3H8 at a heatervoltage of 0.7 V. The H2 sensitivity of the surface modified F-doped SnO2 micro sensormarkedly increased and reached S = 175 which was found to be about 40 times more thanthat of unmodified sensor (S = ~ 4.2. The increase in the sensitivity is discussed in terms ofincreased resistivity and reduced permeation of gaseous oxygen into the underlying sensinglayer due to the surface modification of the sensor. The present micro-hydrogen sensor withenhanced sensitivity due to SiO2 incorporation is a low energy consuming portable sensormodule that can be mass-produced using MEMS technology at low cost.

  11. Uncovering a new quasi-2D CuO2 plane between the YBa2Cu3O7 and CeO2 buffer layer of coated conductors

    Science.gov (United States)

    Li, Zhi-Xin; Cao, Jin-Jin; Gou, Xiao-Fan; Wang, Tian-Ge; Xue, Feng

    2018-01-01

    We report a discovery of the quasi-two-dimensional (quasi-2D) CuO2 plane between the superconductor YBa2Cu3O7 (YBCO) and CeO2 buffer layer (mostly used in the fabrication) of coated conductors through the atomistic computer simulations with the molecular dynamics (MD) and first-principle calculations. For an YBCO coated conductor with multilayer structures, the buffer layers deposited onto a substrate are mainly considered to transfer a strong biaxial texture from the substrate to the YBCO layer. To deeply understand the tuning mechanism of the texture transfer, exploring the complete atomic-level picture of the structure between the YBa2Cu3O7/CeO2 interfaces is firstly required. However, the related observation data have not been available due to some big challenges of experimental techniques. With the MD simulations, having tested the accuracy of the potential functions for the YBa2Cu3O7/CeO2 interface, we constructed a total of 54 possible atom stacking models of the interface and identified its most appropriate and stable structure according to the criterion of the interface adhesion energy and the coherent characterization. To further verify the stability of the identified structure, we performed the first-principle calculations to obtain the adhesion energy and developed the general knowledge of the interface structure. Finally, a coherent interface formed with a new built quasi-2D CuO2 plane that is structurally similar to the CuO2 plane inside bulk YBCO was determined.

  12. Facile Synthesis of CeO2-LaFeO3 Perovskite Composite and Its Application for 4-(Methylnitrosamino-1-(3-Pyridyl-1-Butanone (NNK Degradation

    Directory of Open Access Journals (Sweden)

    Kaixuan Wang

    2016-04-01

    Full Text Available A facile and environmentally friendly surface-ion adsorption method using CeCO3OH@C as template was demonstrated to synthesize CeO2-LaFeO3 perovskite composite material. The obtained composite was characterized by X-ray diffraction (XRD, fourier transform infrared spectra (FT-IR, field-emission scanning electron microscopy (FE-SEM, transmission electron microscopy (TEM, thermo-gravimetric analysis and differential scanning calorimetry (TG-DSC, N2 adsorption/desorption isotherms and X-ray photoelectron spectra (XPS measurements. The catalytic degradation of nitrosamine 4-(methylnitrosamino-1-(3-pyridyl-1-butanone (NNK was tested to evaluate catalytic activity of the CeO2-LaFeO3 composite. Much better activity was observed for the CeO2-LaFeO3 composite comparing with CeO2 and LaFeO3. These results suggested that perovskite composite materials are a promising candidate for the degradation of tobacco-specific nitrosamines (TSNAs.

  13. CEO Sites Mission Management System (SMMS)

    Science.gov (United States)

    Trenchard, Mike

    2014-01-01

    Late in fiscal year 2011, the Crew Earth Observations (CEO) team was tasked to upgrade its science site database management tool, which at the time was integrated with the Automated Mission Planning System (AMPS) originally developed for Earth Observations mission planning in the 1980s. Although AMPS had been adapted and was reliably used by CEO for International Space Station (ISS) payload operations support, the database structure was dated, and the compiler required for modifications would not be supported in the Windows 7 64-bit operating system scheduled for implementation the following year. The Sites Mission Management System (SMMS) is now the tool used by CEO to manage a heritage Structured Query Language (SQL) database of more than 2,000 records for Earth science sites. SMMS is a carefully designed and crafted in-house software package with complete and detailed help files available for the user and meticulous internal documentation for future modifications. It was delivered in February 2012 for test and evaluation. Following acceptance, it was implemented for CEO mission operations support in April 2012. The database spans the period from the earliest systematic requests for astronaut photography during the shuttle era to current ISS mission support of the CEO science payload. Besides logging basic image information (site names, locations, broad application categories, and mission requests), the upgraded database management tool now tracks dates of creation, modification, and activation; imagery acquired in response to requests; the status and location of ancillary site information; and affiliations with studies, their sponsors, and collaborators. SMMS was designed to facilitate overall mission planning in terms of site selection and activation and provide the necessary site parameters for the Satellite Tool Kit (STK) Integrated Message Production List Editor (SIMPLE), which is used by CEO operations to perform daily ISS mission planning. The CEO team

  14. Al and Si Influences on Hydrogen Embrittlement of Carbide-Free Bainitic Steel

    Directory of Open Access Journals (Sweden)

    Yanguo Li

    2013-01-01

    Full Text Available A first-principle method based on the density functional theory was applied to investigate the Al and Si influences on the hydrogen embrittlement of carbide-free bainitic steel. The hydrogen preference site, binding energy, diffusion behaviour, and electronic structure were calculated. The results showed that hydrogen preferred to be at the tetrahedral site. The binding energy of the cell with Si was the highest and it was decreased to be the worst by adding hydrogen. The diffusion barrier of hydrogen in the cell containing Al was the highest, so it was difficult for hydrogen to diffuse. Thus, hydrogen embrittlement can be reduced by Al rather than Si.

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

    International Nuclear Information System (INIS)

    Hwang, C.-C.; Huang, T.-H.; Tsai, J.-S.; Lin, C.-S.; Peng, C.-H.

    2006-01-01

    In this study, ceria (CeO 2 ) powders were synthesized with 50 g per batch via a combustion technique using two kinds of starting materials-urea [(NH 2 ) 2 CO] (as a fuel) and ceric ammonium nitrate [Ce(NH 4 ) 2 (NO 3 ) 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 CeO 2 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

  16. The Effects of Added Hydrogen on Noble Gas Discharges Used as Ambient Desorption/Ionization Sources for Mass Spectrometry

    Science.gov (United States)

    Ellis, Wade C.; Lewis, Charlotte R.; Openshaw, Anna P.; Farnsworth, Paul B.

    2016-09-01

    We demonstrate the effectiveness of using hydrogen-doped argon as the support gas for the dielectric barrier discharge (DBD) ambient desorption/ionization (ADI) source in mass spectrometry. Also, we explore the chemistry responsible for the signal enhancement observed when using both hydrogen-doped argon and hydrogen-doped helium. The hydrogen-doped argon was tested for five analytes representing different classes of molecules. Addition of hydrogen to the argon plasma gas enhanced signals for gas-phase analytes and for analytes coated onto glass slides in positive and negative ion mode. The enhancements ranged from factors of 4 to 5 for gas-phase analytes and factors of 2 to 40 for coated slides. There was no significant increase in the background. The limit of detection for caffeine was lowered by a factor of 79 using H2/Ar and 2 using H2/He. Results are shown that help explain the fundamental differences between the pure-gas discharges and those that are hydrogen-doped for both argon and helium. Experiments with different discharge geometries and grounding schemes indicate that observed signal enhancements are strongly dependent on discharge configuration.

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

    Directory of Open Access Journals (Sweden)

    Majid Farahmandjou

    2015-06-01

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

  18. Oxygen Vacancies versus Fluorine at CeO 2 (111) : A Case of Mistaken Identity?

    NARCIS (Netherlands)

    Kullgren, J.; Wolf, M.J.; Castleton, C.W.M.; Mitev, P.; Briels, Willem J.; Hermansson, K.

    2014-01-01

    We propose a resolution to the puzzle presented by the surface defects observed with STM at the (111) surface facet of CeO 2 single crystals. In the seminal paper of Esch et al. [Science 309, 752 (2005)] they were identified with oxygen vacancies, but the observed behavior of these defects is

  19. Growth of boron doped hydrogenated nanocrystalline cubic silicon carbide (3C-SiC) films by Hot Wire-CVD

    Energy Technology Data Exchange (ETDEWEB)

    Pawbake, Amit [School of Energy Studies, Savitribai Phule Pune University, Pune 411 007 (India); Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Mayabadi, Azam; Waykar, Ravindra; Kulkarni, Rupali; Jadhavar, Ashok [School of Energy Studies, Savitribai Phule Pune University, Pune 411 007 (India); Waman, Vaishali [Modern College of Arts, Science and Commerce, Shivajinagar, Pune 411 005 (India); Parmar, Jayesh [Tata Institute of Fundamental Research, Colaba, Mumbai 400 005 (India); Bhattacharyya, Somnath [Department of Metallurgical and Materials Engineering, IIT Madras, Chennai 600 036 (India); Ma, Yuan‐Ron [Department of Physics, National Dong Hwa University, Hualien 97401, Taiwan (China); Devan, Rupesh; Pathan, Habib [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India); Jadkar, Sandesh, E-mail: sandesh@physics.unipune.ac.in [Department of Physics, Savitribai Phule Pune University, Pune 411007 (India)

    2016-04-15

    Highlights: • Boron doped nc-3C-SiC films prepared by HW-CVD using SiH{sub 4}/CH{sub 4}/B{sub 2}H{sub 6}. • 3C-Si-C films have preferred orientation in (1 1 1) direction. • Introduction of boron into SiC matrix retard the crystallanity in the film structure. • Film large number of SiC nanocrystallites embedded in the a-Si matrix. • Band gap values, E{sub Tauc} and E{sub 04} (E{sub 04} > E{sub Tauc}) decreases with increase in B{sub 2}H{sub 6} flow rate. - Abstract: Boron doped nanocrystalline cubic silicon carbide (3C-SiC) films have been prepared by HW-CVD using silane (SiH{sub 4})/methane (CH{sub 4})/diborane (B{sub 2}H{sub 6}) gas mixture. The influence of boron doping on structural, optical, morphological and electrical properties have been investigated. The formation of 3C-SiC films have been confirmed by low angle XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform infra-red (FTIR) spectroscopy and high resolution-transmission electron microscopy (HR-TEM) analysis whereas effective boron doping in nc-3C-SiC have been confirmed by conductivity, charge carrier activation energy, and Hall measurements. Raman spectroscopy and HR-TEM analysis revealed that introduction of boron into the SiC matrix retards the crystallanity in the film structure. The field emission scanning electron microscopy (FE-SEM) and non contact atomic force microscopy (NC-AFM) results signify that 3C-SiC film contain well resolved, large number of silicon carbide (SiC) nanocrystallites embedded in the a-Si matrix having rms surface roughness ∼1.64 nm. Hydrogen content in doped films are found smaller than that of un-doped films. Optical band gap values, E{sub Tauc} and E{sub 04} decreases with increase in B{sub 2}H{sub 6} flow rate.

  20. Progress in the chemistry of chromium(V) doping agents used in polarized target materials

    International Nuclear Information System (INIS)

    Krumpolc, M.; Hill, D.; Struhrmann, H.B.

    1990-01-01

    We wish to report progress in two areas of the chromium (V)-based doping agents: Two commonly used chromium (V) complexes, I and II, have been synthesized in perdeuterated form (i.e., all hydrogens replaced by deuterium). They are sodium bis(2-ethyl-2-deuteroxy-butyrato)oxochromate(V)monodeuterate, IV, (acronym EDBA-Cr(V)), and sodium bis(2-deuteroxy-2-methylpropionato)oxochromate(V), III, (acronym DMPA-Cr(V)). A synthetic route leading to the preparation of stable, chromium(III)-free solutions of chromium(V) in diols (1,2-ethanediol/ethylene glycol/and 1,2-propanediol/propylene glycol/) has been outlined