Sample records for er-doped ceo2 thin

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

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


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

  2. Optical properties of CeO2 thin films

    S Debnath; M R Islam; M S R Khan


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

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

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


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

  4. Violet/blue photoluminescence from CeO2 thin film


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

  5. Optical constants and near infrared emission of Er doped ZnO sol–gel thin films

    Vettumperumal, R. [P.G. and Research Department of Physics, Sri Paramakalyani College, Alwarkurichi 627412, Tamil Nadu (India); Kalyanaraman, S., E-mail: [P.G. and Research Department of Physics, Sri Paramakalyani College, Alwarkurichi 627412, Tamil Nadu (India); Thangavel, R., E-mail: [Department of Applied Physics, Indian School of Mines, Dhanbad (India)


    Erbium (Er) doped zinc oxide (ZnO) sol–gel thin films were deposited on glass substrate using the spin coating method. The effect of erbium concentration and annealing temperature on structural and optical properties was studied. The annealed film was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectrum (EDX), micro-Raman, photoluminescence (PL) and UV–vis spectroscopy. All the films showed a wurtzite structure of polycrystalline nature with an average crystal size of 27.44 nm at 500 °C and 29.28 nm at 600 °C. The Raman spectra confirmed the absence of secondary phases in the Er doped ZnO films and the longitudinal optical phonon mode was upto the fifth order. Densely packed surfaces of the films were observed from SEM images. The presence and distribution of Zn, O and Er elements in the deposited films were confirmed by EDX analysis. The calculated value of exciton binding energy of ZnO film was 60 meV with a maximum value of 72 meV being observed for Er doped films. The near infra-red emission peak was observed at 1.63 eV through PL spectra studies. The average transmission was 80% with the calculated value of optical band gap being 3.26–3.32 eV. An increase in the refractive index value predicts the substitutional incorporation of Er ions in ZnO with the maximum optical conductivity being observed in the UV region. - Highlights: • Higher exciton binding energy in the doped ZnO films. • Near infrared emission is observed and better than ZnO. • Refractive index is calculated by theoretical and experimental means. • Maximum optical conductivity in the UV region.

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


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

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

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


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

  8. Fabrication and photoluminescence of Er-doped ZnO thin films on SiO2/Si substrate by pulsed laser deposition

    GU Xiuquan; ZHU Liping; YE Zhizhen; HE Haiping; ZHAO Binghui


    Er doped ZnO thin films were grown on Si substrates using SiO2 buffer layer by pulsed laser deposition (PLD) method.The obtained films crystallize well and show high c-axis orientation.The Er content was evidently detected by the energy dispersive X-ray spectroscopy (EDS).Upon annealing in O2 ambience at different temperatures, the films show different photoluminescence properties at 1.54 μm.The samples annealed at 700 and 850 ℃ show intense photoluminescence peaks which enhance with the annealing temperature, while no obvious luminescence peaks are observed for the as-grown samples or annealed at 500 ℃.The possible mechanism was discussed.

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

    徐芸芸; 张韬; 李争鸣; 徐新


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

  10. Photoluminescence and electrochemical properties of transparent CeO2-ZnO nanocomposite thin films prepared by Pechini method

    Sani, Z. Khosousi; Ghodsi, F. E.; Mazloom, J.


    Nanocomposite thin films of CeO2-ZnO with different molar ratios of Zn/Ce (=0, 0.25, 0.5, 0.75 and 1) were prepared by the Pechini sol-gel route. Various spectroscopic and electrochemical techniques were applied to investigate the films. XRD patterns of all the samples exhibited the peaks corresponding to cubic fluorite structure of ceria and the (101) and (103) peaks of ZnO with hexagonal structure was just observed in the sample with molar ratio of 1. EDS confirmed the presence of constituent of element in the samples. FESEM images of the films showed a surface composed of nanograins. AFM analysis revealed that root mean square roughness was enhanced as molar ratio of Zn/Ce increased. Moreover, fractal dimension of surfaces were calculated by cube counting approach. Optical measurements indicated that the film with molar ratio of 1 has the highest transmission and lowest reflectivity. The optical band gap values varied between 2.95 and 3.42 eV. The compositional dependence of refractive index and extinction coefficient were reported. The UV and blue emission appeared in PL spectra. The highest photoluminescence emission intensity was observed in the 1:1 molar ratio sample. The cyclic voltammetry measurements indicated the highest charge density (9.75 mC cm-2) and diffusion coefficient (3.507 × 10-17 cm2 s-1) belonged to the Ce/Zn (1:1) thin film.

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

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


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

  12. Hybrid solar cells based on MEH-PPV and thin film semiconductor oxides (TiO2, Nb2O5, ZnO, CeO2 and CeO2–TiO2): Performance improvement during long-time irradiation

    Lira-Cantu, M.; Krebs, Frederik C


    prepared as bi-layers of thin film semiconducting oxides (TiO2, Nb2O5, ZnO, CeO2-TiO2 and CeO2) and the polymer MEH-PPV, with a final device configuration of ITO/ Oxide(thin) (film)/MEH-PPV/Ag. The oxides were prepared as thin transparent films from sol-gel solutions. The photovoltaic cells were studied......Performance improvement of hybrid solar cells (HSC) applying five different thin film semiconductor oxides has been observed during long-time irradiation in ambient atmosphere. This behavior shows a direct relation between HSC and oxygen content from the environment. Photovoltaic devices were...... with TiO2 thin films showed the best performance with maximum V-oc as high as -0.74V and I-sc of 0.4mA/cm(2). Solar decay analyses showed that the devices require a stabilization period of several hours in order to reach maximum performance. In the case of TiO2, Nb2O5 and CeO2-TiO2, the maximum current...

  13. Preparation and Properties of Dip-coated CeO2-TiO2 Thin Golden Glass Film


    The golden and ultraviolet-absorbed CeO2-TiO2 film was prepared on soda-lime glass substrate with the thickness of 2 mm via the sol-gel method. The transmission spectra in range of 200 nm-800 nm were measured, and the crystallization, the abrasion and acid resistance were also investigated. The appropriate sol contents and heat-treatment schedule were determined. The results indicate that the appropriate molar ratio of Ce/Ti was 3:5 to 5:6. The ultraviolet-absorbance ability increased with the increase of the Ce/Ti molar ratio, but when the Ce/Ti molar ratio was higher than 1.5, the homogeneity of the film was deteriorated. With the increase of heat-treatment temperature, the main wavelengths of the color of the coated glasses were equal, but the color's saturation decreased; the transmission peaks were the same, while the intensity of the peaks decreased. The roughness, abrasion and acid resistance of the film were also en hanced at the same time. The appropriate heattreatment temperature may be 340 ℃.

  14. Room-Temperature Ferromagnetism of Co-Doped CeO2 Thin Films on Si(111) substrates

    SONG Yuan-Qiang; ZHANG Huai-Wu; WEN Qi-Ye; LI Yuan-Xun; John Q. Xiao


    @@ Using Co2O3 as the Co source, doped cerium oxide thin films with the composition of Ce0.97Co0.03O2-δ (CCO)are deposited on Si(111) and glass substrates by pulse laser deposition technique. X-ray diffraction reveals that CCO films with (111) preferential orientation are grown on Si, while the film on glass is polycrystalline with nanocrystal. X-ray photoelectron spectroscopy shows that the Co displaces the Ce atom and exists in high spin state rather than low spin state, which contributes to the room-temperature ferromagnetism confirmed by vibration sample magnetometer.

  15. CeO2 thin film as a low-temperature formaldehyde sensor in mixed vapour environment

    R Pandeeswari; B G Jeyaprakash


    Nanostructured cerium oxide thin film was deposited onto the glass substrate under optimized condition using spray-pyrolysis technique. X-ray diffraction result indicates polycrystalline nature of the film with fluorite-type face-centered-cubic structure. The atomic force micrograph indicates the presence of nanocrystallites over the film surface. The vapour sensing characteristics of the annealed film were studied by chemiresistive method for various concentrations of formaldehyde vapour at room temperature (∼ 30 °C). For 0.5 ppm of formaldehyde vapour, the film shows a response and recovery time of 36 and 1 s, respectively. The vapour sensing properties of the cerium oxide film in mixed environment were studied and reported.

  16. Double Clad Er-doped Fiber Amplifier

    FU Yong-jun; MAO Xiang-qiao; WEI Huai; LI jian


    Presented is a theoretical study of double-clad Er-doped fiber power amplifier(EDFA). Two kinds of double clad fibers(DCF) with rectangular and "flower" inner clad shapes are studied, and these fibers have different coupling constants and propagation losses. We calculate the effective pump power absorption ratio along the fiber with different coupling constants from the first cladding to the doped core and with different propagation losses for the power in the inner cladding. Then the gains of the double clad Er-doped fiber amplifiers versus fiber lengths are calculated using the EDFA model based on propagation and rate equations of a homogeneous, two-level medium.

  17. Modification of erbium photoluminescence decay rate due to ITO layers on thin films of SiO{sub 2}:Er doped with Si-nanoclusters

    Wojdak, M., E-mail: [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Jayatilleka, H. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Department of Electrical and Computer Engineering, University of Toronto, 10 King' s College Road, Toronto, Ontario, Canada M5S 3G4 (Canada); Shah, M. [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Kenyon, A.J., E-mail: [Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Gourbilleau, F.; Rizk, R. [Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), ENSICAEN, CNRS, CEA/IRAMIS, Université de Caen, 14050 CAEN cedex (France)


    During the fabrication of MOS light emitting devices, the thin film of active material is usually characterized by photoluminescence measurements before electrical contacts are deposited. However, the presence of a conductive contact layer can alter the luminescent properties of the active material. The local optical density of states changes due to the proximity of luminescent species to the interface with the conductive medium (the top electrode), and this modifies the radiative rate of luminescent centers within the active layer. In this paper we report enhancement of the observed erbium photoluminescence rate after deposition of indium tin oxide contacts on thin films of SiO{sub 2}:Er containing silicon nanoclusters, and relate this to Purcell enhancement of the erbium radiative rate. -- Highlights: ► We studied photoluminescence of Er in SiO{sub 2} thin films doped with Si nanoclusters. ► Presence of ITO layer on the top enhances photoluminescence decay rate of Er. ► The effect depends on the thickness of active film. ► Radiative rate change in proximity of ITO layer was calculated theoretically. ► The calculation results are compared with the experiment and discussed.

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

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


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

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

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


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

  20. Structural and flux-pinning properties of laser ablated YBa 2Cu 3O 7-δ thin films: Effects of self-assembled CeO 2 nanodots on LaAlO 3 substrates

    Haywood, Talisha; Oh, Sang Ho; Kebede, Abebe; Pai, Devdas M.; Sankar, Jag; Christen, David K.; Pennycook, Stephen J.; Kumar, Dhananjay


    Self-assembled nanodots of CeO 2 on (1 0 0) LaAlO 3 substrates, generated in situ by means of a pulsed laser deposition method prior to the deposition of YBa 2Cu 3O 7-δ (YBCO) films, have been used to modify the superconducting properties of resulting YBCO films. Structural characterization has indicated that CeO 2 layers grow via van der Merwe three-dimensional mode and the islands eventually acquire a pancake type of structure with lateral dimension several times larger than vertical dimension. The three-dimensional growth of CeO 2 islands with (1 0 0) preferred orientation is believed to be associated with its surface energy anisotropy. The magnetization versus temperature and magnetization versus field measurements and analysis have suggested that CeO 2 can affect the superconducting properties of YBCO films favorably or adversely depending on the density of CeO 2 nanodots on the substrate surfaces prior to the deposition of YBCO films.

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

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


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

  2. Collective magnetic response of CeO2 nanoparticles

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


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

  3. Effect of the RE (RE = Eu, Er) doping on the structural and textural properties of mesoporous TiO{sub 2} thin films obtained by evaporation induced self-assembly method

    Borlaf, Mario, E-mail: [Instituto de Cerámica y Vidrio, CSIC, C/Kelsen, 5, Cantoblanco, E-28049 Madrid (Spain); Caes, Sebastien; Dewalque, Jennifer [LCIS-GREENMAT, Institute of Chemistry, University of Liege, B6 Sart Tilman, 4000 Liege (Belgium); Colomer, María Teresa; Moreno, Rodrigo [Instituto de Cerámica y Vidrio, CSIC, C/Kelsen, 5, Cantoblanco, E-28049 Madrid (Spain); Cloots, Rudi; Boschini, Frederic [LCIS-GREENMAT, Institute of Chemistry, University of Liege, B6 Sart Tilman, 4000 Liege (Belgium); APTIS, Institute of Physics, University of Liege, B5 Sart Tilman, 4000 Liege (Belgium)


    Polymeric sol–gel route has been used for the preparation of TiO{sub 2} and RE{sub 2}O{sub 3–}TiO{sub 2} (RE = Eu, Er) mesoporous thin films by evaporation induced self-assembly method using Si (100) as a substrate. The influence of the relative humidity (RH) on the preparation of the film has been studied being necessary to work under 40% RH in order to obtain homogeneous and transparent thin films. The films were annealed at different temperatures until 900 °C/1 h and the anatase crystallization and its crystal size evolution were followed by low angle X-ray diffraction. Neither the anatase–rutile transition nor the formation of other compounds was observed in the studied temperature range. Ellipsoporosimetry studies demonstrated that the thickness of the thin films did not change after calcination at 500 °C, the porosity was constant until 700 °C, the pore size increased and the specific surface area decreased with temperature. Moreover, the effect of the doping with Er{sup 3+} and Eu{sup 3+} was studied and a clear inhibition of the crystal growth and the sintering process was detected (by transmission electron and atomic force microscopy) when the doped films are compared with the undoped ones. Finally, Eu{sup 3+} and Er{sup 3+} f–f transitions were detected by PL measurements. - Highlights: • Eu and Er–TiO{sub 2} mesoporous films were prepared by evaporation induced self-assembly. • Influence of humidity on porosity and photoluminescent properties has been tested. • Influence of calcination on structural and textural properties has been also studied. • f–f transitions indicate that the thin films are active photoluminescent materials.

  4. Visible emission from Er-doped SnO2 thin films deposited by sol-gel Emissão no visível de filmes finos, depositados via sol-gel, de SnO2 dopados com Er

    L. P. Ravaro


    Full Text Available Emission from Er-doped SnO2 thin film deposited via sol-gel by the dip coating technique is obtained in the range 500-700 nm with peak at 530 nm (green. Electron-hole generation in the tin dioxide matrix is used to promote the rare-earth ion excitation. Evaluation of crystallite dimensions through X-ray diffraction results leads to nanoscopic size, what could play a relevant role in the emission spectra. The electron-hole mechanism is also responsible for the excitation of the transition in the 1540 nm range in powders obtained from the same precursor solution of films. The thin film matrix presents a very useful shape for technological application, since it allows integration in optical devices and the application of electric fields to operate electroluminescent devices.Foi obtida emissão de filmes finos de SnO2 dopados com Er no intervalo 500-700 nm, com pico em 530 nm (verde. Esses filmes foram depositados pela técnica de molhamento via sol-gel. A geração de pares elétron-buraco na matriz de SnO2 é usada para promover a excitação do íon terra-rara. A avaliação do tamanho dos cristalitos por meio de resultados de difração de raios X indica dimensões nanoscópicas, o que pode ser relevante para a interpretação do espectro de emissão. O mecanismo de excitação elétron-buraco é também responsável pela excitação da transição no intervalo que inclui 1540 nm em pós obtidos da mesma solução precursora dos filmes. Filmes finos constituem um formato muito útil para aplicações tecnológicas, desde que permite integração em dispositivos ópticos e a aplicação de campos elétricos para operar dispositivos eletroluminescentes.

  5. Preparation and Characterization of Graphite Powder Covered with CeO2


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

  6. Facile hydrothermal synthesis of CeO2 nanopebbles

    N Sabari Arul; D Mangalaraj; Jeong In Han


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

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

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


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

  8. Synthesis, Characterization, and Photocatalysis of ZnO and Er-Doped ZnO

    Yu, Kai-sheng; Shi, Jian-ying; Zhang, Zai-Li; Liang, Yong-Mei; LIU Wei


    ZnO and Er-doped ZnO with different molar ratios of Er/Zn were prepared using the homogeneous precipitation method. The photocatalysts prepared were characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction (XRD), UV-vis spectroscopy, and photoluminescence spectroscopy. The results showed that the Er-doped ZnO displayed characteristic wurtzite-type peaks in the XRD spectra. The Er-doped ZnO absorbed much more light than ZnO in the ultraviolet region...

  9. Enhanced magnetodielectric and multiferroic properties of Er-doped bismuth ferrite nanoparticles

    Mukherjee, A.; Banerjee, M. [Department of Physics, National Institute of Technology, Durgapur 713209 (India); Basu, S., E-mail: [Department of Physics, National Institute of Technology, Durgapur 713209 (India); Mukadam, M.D.; Yusuf, S.M. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Pal, M. [CSIR-Central Glass & Ceramic Research Institute, Kolkata 700032 (India)


    An enhancement in multiferroic properties has been achieved for chemically prepared BFO nanoparticles by doping with erbium (Er). XRD along with electron microscopy study reveals the phase purity and nanocrystalline nature of BFO. Enhancement of both the magnetic moment and resistivity is observed by virtue of Er doping. The observed enhanced magnetic moment is considered to be associated with smaller crystallite whereas increase of resistivity may be attributed to a decrease of oxygen vacancies. Doping also display an improvement of leakage behaviour and dielectric constant in nanocrystalline BFO, reflected in well-developed P-E loop. In addition, large enhancement in magnetodielectric coefficient is observed because of Er doping. Therefore, the results provide interesting approaches to improve the multiferroic properties of BFO, which has great implication towards its applications. - Highlights: • Synthesis of pure Er-doped BFO nanoparticles by chemical route. • Large increase in magnetic moment and resistivity due to Er doping. • Er doping produce well developed P-E loop and enhance polarization. • Drastic increase in dielectric constant as well as magnetodielectric coefficient observes because of Er doping.

  10. Three-Dimensional Structure of CeO2 Nanocrystals

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


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

  11. Design and Fabrication of an Er-Doped Silica Optical Fiber with Six Photosensitive Subcores

    LI Jian; WANG Jing; LIU Peng; LU Shao-Hua; MAO Xiang-Qiao; JIANG Wei-Wei; NING Ti-Gang; JIAN Shui-Sheng


    A type of multi-core Er-doped photosensitive silica optical fiber (MC-EDPF) is proposed and fabricated, in which a high consistency Er-doped core is surrounded by six high consistency Ge-doped cores. The multi-core design can overcome the difficulties encountered in the design and fabrication of single-core EDPFs through a modified chemical vapor deposition method combined with solution doping technology, and there is a conflict between high consistency Er doping and high consistency Ge doping. The absorption of MC-EDPFs achieved 15.876dB/m at 1550nm and 10dB/m at 980hm. The reflectivity of the fiber Bragg gratings (FBGs) written directly on the MC-EDPFs is as much as 96.84%.

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

    沈丹华; 吉琳韬; 付玲玲; 董旭龙; 刘志刚; 刘强; 刘世明


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

  13. Synthesis of Er-doped Lu2O3 nanoparticles and transparent ceramics

    Serivalsatit, K.; Wasanapiarnpong, T.; Kucera, C.; Ballato, J.


    Transparent rare earth-doped Lu2O3 ceramics have received much attention for use in solid-state scintillator and laser applications. The fabrication of these ceramics, however, requires ultrafine and uniform powders as precursors. Presented here is the synthesis of Er-doped Lu2O3 nanopowders by a solution precipitation method using Er-doped lutetium sulfate solution and hexamethylenetetramine as a precipitant and the fabrication of Er-doped Lu2O3 transparent ceramics from these nanopowders. The precipitated precursors were calcined at 1100 °C for 4 h in order to convert the precursors into Lu2O3 nanoparticles with an average particle size of 60 nm. Thermal decomposition and phase evolution of the precursors were studied by simultaneous thermal analysis (STA), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Er-doped Lu2O3 transparent ceramics were fabricated from these nanopowders using vacuum sintering followed by hot isostatic pressing at 1700 °C for 8 h. The transparent ceramics exhibit an optical transmittance of 78% at a wavelength of 1.55 μm.

  14. Er-doped concentric-cores optical fiber for simultaneous amplification and compensation of positive dispersion

    Pramod R. Watekar; M. L. N. Goswami; H. N. Acharya; J. C. Biswas; B. P. Pal


    The Er-doped concentric-cores dispersion compensating fiber (EDDCF) has been demonstrated. The rare earth has been doped as a ring around the inner core. We have obtained 14-dB gain at 1550 nm (using the optical fiber network where amplification as well as negative dispersion are necessary.

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

    Berton Marcos A.C.


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

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


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

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

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


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

  18. Effect of CeO2 Addition on Hybrid Direct Carbon Fuel Cell Performance

    Ippolito, Davide; Deleebeeck, Lisa; Kammer Hansen, Kent


    The effect of CeO2 infiltration into the anode or CeO2 mixed with the carbon-fuel on the performance of a Hybrid Direct Carbon Fuel Cell (HDCFC) was studied through the use of polarization curves and electrochemical impedance spectroscopy. The use CeO2 in both ways helped to increase the cell...

  19. Effect of CeO2 Infiltration on Hybrid Direct Carbon Fuel Cell Performance

    Ippolito, Davide; Deleebeeck, Lisa; Kammer Hansen, Kent


    The effect of CeO2 infiltration into the anode or CeO2 mixed with the carbon-fuel on the performance of a Hybrid Direct Carbon Fuel Cell (HDCFC) was studied through the use of polarization curves and electrochemical impedance spectroscopy. The use CeO2 in both ways helped to increase the cell...

  20. Er-doped fiber ring laser gyroscopes operating in continuous waves

    Jingren Qian; Jue Su; Xuxu Wang; Bing Zhu


    A direction related polarizer was inserted into a ring laser cavity to eliminate one of the two eigen-modes as well as spatial hole burning of the gain medium in a bidirectional Er-doped fiber ring laser. Thus, a fiber ring laser gyroscope (FRLG) operating in continuous wave was demonstrated. A beat signal of over 30-dB noise was observed and a good inear relation between the beat frequency shift and cavity rotation rate was obtained.

  1. Unusual Compression Behavior of Nanocrystalline CeO2

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


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

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

    Hattori, Takashi; Kobayashi, Katsutoshi; Ozawa, Masakuni


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

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

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


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

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

    Crovetto, Andrea; Yan, Chang; Iandolo, Beniamino


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

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

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


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

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

    LIU Zhen-Xiang; XIE Kan


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

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

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


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

  8. Photoluminescence in Er-doped V{sub 2}O{sub 5} and Er-doped CdV{sub 2}O{sub 6}

    González-Rivera, Y.A.; Cervantes-Juárez, E.; Aquino-Meneses, L. [Benemérita Universidad Autónoma de Puebla. Postgrado en Física Aplicada. Facultad de Ciencias Físico-Matemáticas, Av. San Claudio y Av. 18 sur, Col. San Manuel Ciudad Universitaria, Puebla Pue. C. P. 72570 (Mexico); Lozada-Morales, R., E-mail: [Benemérita Universidad Autónoma de Puebla. Postgrado en Física Aplicada. Facultad de Ciencias Físico-Matemáticas, Av. San Claudio y Av. 18 sur, Col. San Manuel Ciudad Universitaria, Puebla Pue. C. P. 72570 (Mexico); Jiménez-Sandoval, S. [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Querétaro, Apartado Postal 1-798, Querétaro, Qro. 76001 (Mexico); Rubio-Rosas, E.; Agustín-Serrano, R.; Cerna, C. de la; Reyes-Cervantes, E. [Centro Universitario de Vinculación y transferencia de Tecnología, Prol. De la 24 Sur y Av. San Claudio, Col. San Manuel, Puebla (Mexico); Zelaya Angel, O.; Tomas, S.A. [Departamento de Física, Centro de Investigación y de Estudios Avanzados, P.O. Box 14-740, México 07360, D.F. (Mexico); Rodriguez-Melgarejo, F. [Centro de Investigación y de Estudios Avanzados del IPN, Unidad Querétaro, Apartado Postal 1-798, Querétaro, Qro. 76001 (Mexico); and others


    A group of samples from the CdO–V{sub 2}O{sub 5} binary system, particularly with high V{sub 2}O{sub 5} content, doped with Er{sup 3+} were prepared. The set of samples was fabricated using the conventional melt-quenching method. Depending on the proportion of the used reactants, the existence of V{sub 2}O{sub 5} and of CdV{sub 2}O{sub 6} was identified from X-ray diffraction measurements and Raman spectroscopy. Depending on the relative concentrations of CdO and V{sub 2}O{sub 5}, different types of morphologies for each sample were found in a scanning electron microscope. Their chemical composition was measured from energy dispersive spectroscopy in the same instrument. An effective Er-doping of the order of 1.0±0.35 at% was found for each sample. From optical absorption data, the composition dependent optical band gap was determined with values between 1.94 and 2.29 eV. Finally, photoluminescence experiments showed, in the samples with the highest V{sub 2}O{sub 5} content, wide bands associated to oxygen vacancies. For the rest of the samples emissions from electronic transitions of Er{sup 3+} ions were detected. - Highlights: • PL ascribed to oxygen vacancies in Er-doped V{sub 2}O{sub 5} was observed. • PL of electronic transitions of Er{sup 3+} which is immersed in CdV{sub 2}O{sub 6} was found. • Some of those electronic transitions present sharp and narrow emissions. • An E{sub g} in the 1.94–2.29 range for this batch of samples was determined.

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

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


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

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

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


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

  11. Comparison of Er-doped sol-gel glasses with various hosts

    Xiang, Qing; Zhou, Yan; Lam, Yee Loy; Ooi, Boon Siew; Chan, Yuen Chuen; Kam, Chan Hin


    Using the sol-gel process, we prepared three groups of Er-doped glasses, namely, Er-doped Si02-A101.5 (SAB) glass, Er-doped Si02-Ti02-A101.5 (STAE) glass, and Er-doped Si02-Ge02-Al01.5 (SGAE) glass. Various erbium concentration and different host composition under the same processing condition have been studied in order to optimize the material composition to get the strongest fluorescence emission for each material system. It has been found that for SAE glass, the strongest fluorescence emission is obtained when the mole ratio of the three constituent oxides is lOOSiO2 : 20A101.5 2ErO1.5. For the STAE material system, the best composition ratio for the strongest fluorescence emission is 93 Si02 : 7TiO2: 20A101.5 : lErO1.5, whereas the value for SGAE glass is 9OSiO2:lOGeO2 : 2OAlO1.5: 1ErO1.5. But the relative lifetimes were obtained with the recipe lOOSiO2:10A101.5:1ErO1.5 for SAE series, 90 Si02:lOGeO2:1OAlO1.5: 1ErO1.5 for STAE group and 93 Si02:7Ti02:20A101.5:1ErO1.5 for STAE group. Using these recipes, three 20-layer (up to 2.5 μm) crack-free films have been deposited on silica-on-silicon (SOS) substrates with multiple spin-coating and rapid thermal annealing (RTA). Only the STAE film and the SGAE film are found to guide light. The experimental results show that STAB glasses have higher hydrophilicity than SGAE glasses and SGAE glasses has lower crystallization temperature than STAE glasses. The fact that these waveguiding films emit relatively strong fluorescence around the wavelength of 1.55 μm implies that such planar waveguides are potential candidates from which integrated optical waveguide amplifiers and lasers operating at the third optical fiber communication window can be fabricated.

  12. Preparation and Characterization of Nanocrystalline CeO2 by Precipitation Method

    董相廷; 李明; 张伟; 刘桂霞; 洪广言


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

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

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


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

  14. Influence of the matrix properties on the performances of Er-doped Si nanoclusters light emitting devices

    Irrera, Alessia; Iacona, Fabio; Franzò, Giorgia; Miritello, Maria; Lo Savio, Roberto; Castagna, Maria Eloisa; Coffa, Salvatore; Priolo, Francesco


    We investigated the properties of light emitting devices whose active layer consists of Er-doped Si nanoclusters (nc) generated by thermal annealing of Er-doped SiOx layers prepared by magnetron cosputtering. Differently from a widely used technique such as plasma enhanced chemical vapor deposition, sputtering allows to synthesize Er-doped Si nc embedded in an almost stoichiometric oxide matrix, so as to deeply influence the electroluminescence properties of the devices. Relevant results include the need for an unexpected low Si excess for optimizing the device efficiency and, above all, the strong reduction of the influence of Auger de-excitation, which represents the main nonradiative path which limits the performances of such devices and their application in silicon nanophotonics.

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

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


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

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

    Shan Wenjuan; Guo Hongjuan; Liu Chang; Wang Xiaonan


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

  17. Sonocatalytic performance of Er-doped ZnO for degradation of a textile dye.

    Khataee, Alireza; Saadi, Shabnam; Safarpour, Mahdie; Joo, Sang Woo


    Pure and erbium (Er)-doped ZnO samples were synthesized through a sonochemical method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-Vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis. The synthesized samples were used as a catalyst for the sonocatalytic decolorization of Reactive Orange 29 (RO29) as a model organic pollutant. The decolorization efficiency was 63%, 68%, 88%, and 75% for undoped, 2%, 4%, and 6% Er-doped ZnO, respectively. The effect of different experimental parameters including catalyst content, dye concentration and ultrasound power was investigated on the sonocatalytic decolorization of RO29. Among several radical scavengers (i.e. chloride, carbonate and sulfate anions and t-butanol), the chloride anion showed the most inhibitive effect on the sonocatalysis performance. Improvement of the sonocatalytic process by K2S2O8 and H2O2 enhancers was also studied. The reusability of the synthesized sonocatalyst was evaluated in several consecutive runs, and a decline of only 4% was observed in the process performance after five runs. The intermediates produced during the degradation of RO29 were identified by GC-MS analysis.

  18. Upconverted fluorescence in Er-doped ZBLAN glasses for high efficiency solar cells

    Henke, Bastian; Ahrens, Bernd; Johnson, Jacqueline A.; Miclea, Paul T.; Schweizer, Stefan


    Transparent erbium-doped fluorozirconate (FZ) glasses are attractive systems for upconversion-based solar cells. Upconverted fluorescence intensity vs. excitation power dependence was investigated for a series of erbium-doped FZ glasses. It was found that the ratio of the 2-photon upconverted emission in the near infrared at 980 nm to the 3-photon upconverted emissions in the visible at 530, 550, and 660 nm decreases with increasing excitation power. The integrated upconverted fluorescence intensity per excitation power shows "saturation" upon increasing the excitation power, while the point of saturation shifts to lower excitation power with increasing erbium doping level. To demonstrate the potential of these upconverters for photovoltaic applications, the external quantum efficiency (EQE) of a commercial monocrystalline silicon solar cell with an Er-doped FZ glass on top of it was measured. For an excitation power of 1 mW at a wavelength of 1540 nm an EQE of 1.6% was found for a 9.1 mol% Er-doped FZ glass. The samples investigated were not optically coupled to the solar cell and no optical coating was applied to the glass surface.

  19. Fast dynamics of 1.5 μm photoluminescence in Er-doped SiO2 sensitized with Si nanocrystals

    Timmerman, D.; Saeed, S.; Gregorkiewicz, T.


    In order to investigate origin of fast photoluminescence at 1.5 μm reported to appear in Er-doped SiO2 sensitized with silicon nanocrystals, time-resolved photoluminescence measurements were compared between high temperature annealed Er-doped and Er-free samples. We confirm that this fast

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

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


    Single-crystalline porous CeO2 nanocrystals, with sizes of ∼20 nm and pore diameters of 1-2 nm, were synthesized successfully using a hydrothermal method. Using electron tomography, we imaged the three-dimensional structure of the pores in the nanocrystals and found that the oriented aggregation...... of small CeO2 nanoparticles resulted in the growth of CeO2 nanocrystals with an irregular truncated octahedral shape and pores extending along the 〈110〉 directions. Oxygen vacancies were found on the crystal surfaces and internal walls of the pores by scanning transmission electron microscopy and electron...... energy-loss spectroscopy. The oxygen vacancies might play an important role in oxygen diffusion in the crystals and the catalytic activities of single-crystalline porous CeO 2 structures. © 2011 American Chemical Society....

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

    Sumanta Kumar Meher; G Ranga Rao


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

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

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


    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 ...

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

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


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

  4. Anomalous compressive behavior in CeO2 nanocubes under high pressure

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


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

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

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


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

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

    Hattori, Takashi; Kobayashi, Katsutoshi; Ozawa, Masakuni


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

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

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


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

  8. Photon management properties of rare-earth (Nd,Yb,Sm)-doped CeO2 films prepared by pulsed laser deposition.

    Balestrieri, Matteo; Colis, Silviu; Gallart, Mathieu; Schmerber, Guy; Bazylewski, Paul; Chang, Gap Soo; Ziegler, Marc; Gilliot, Pierre; Slaoui, Abdelilah; Dinia, Aziz


    CeO2 is a promising material for applications in optoelectronics and photovoltaics due to its large band gap and values of the refractive index and lattice parameters, which are suitable for silicon-based devices. In this study, we show that trivalent Sm, Nd and Yb ions can be successfully inserted and optically activated in CeO2 films grown at a relatively low deposition temperature (400 °C), which is compatible with inorganic photovoltaics. CeO2 thin films can therefore be efficiently functionalized with photon-management properties by doping with trivalent rare earth (RE) ions. Structural and optical analyses provide details of the electronic level structure of the films and of their energy transfer mechanisms. In particular, we give evidence of the existence of an absorption band centered at 350 nm from which energy transfer to rare earth ions occurs. The transfer mechanisms can be completely explained only by considering the spontaneous migration of Ce(3+) ions in CeO2 at a short distance from the RE(3+) ions. The strong absorption cross section of the f-d transitions in Ce(3+) ions efficiently intercepts the UV photons of the solar spectrum and therefore strongly increases the potential of these layers as downshifters and downconverters.

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

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


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

  10. Temperature Programmed Reduction Studies on CeO2-Containing Catalysts

    Noriyoshi Kakuta; Harunobu Ohkita; Takanori Mizushima


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

  11. Preparation and performance of CeO2 hollow spheres and nanoparticles

    ZHANG Wenwen; CHEN Donghui


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

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

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


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

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

    A. Akbari-Fakhrabadi


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

  14. Photosensitivity of ion-exchanged Er-doped phosphate glass using 248nm excimer laser radiation.

    Pissadakis, Stavros; Ikiades, Aris; Hua, Ping; Sheridan, Anna; Wilkinson, James


    The photosensitivity to 248nm excimer laser radiation of Er-doped Schott IOG-1 phosphate glass is presented. The photosensitive mechanism is investigated by employing a grating recording process. Index changes of up to ~2.0x10(-3) were measured in silver ion-exchanged samples using diffraction efficiency measurements; whereas changes of only ~10(-5) were measured for non-ion-exchanged samples. Absorption measurements allowed the identification of specific color center bands, which were attributed to the glass matrix and to the silver ions. Investigation of the exposed ion-exchanged glass using scanning electron microscopy and energy dispersive x-ray microanalysis revealed that in addition to the color centers formed, silver ion migration and ionization contribute significantly to the UV-induced index changes.

  15. Structural and photoluminescence properties of Ce, Dy, Er-doped ZnO nanoparticles

    Jayachandraiah, C. [Department of Physics, JNTU, Anantapur-515002 (India); Kumar, K. Siva [Department of Advanced Materials Science and Engineering, Dankook University, Cheonan, Chungnam 330-714 (Korea, Republic of); Krishnaiah, G., E-mail: [Govt. Degree College, Puttur, Chittoor-517 583 (India)


    Undoped ZnO and rare earth elements (Ce, Dy and Er with 2 at. %) doped nanoparticles were synthesized by wet chemical co-precipitation method at 90°C with Polyvinylpyrrolidone (PVP) as capping agent. The structural, morphological, compositional and photoluminescence studies were performed with X-ray diffraction (XRD), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS), FTIR spectroscopy and Photoluminescence (PL) respectively. XRD results revealed hexagonal wurtzite structure with average particle size around 18 nm - 14 nm and are compatible with TEM results. EDS confirm the incorporation of Ce, Dy and Er elements into the host ZnO matrix and is validated by FTIR analysis. PL studies showed a broad intensive emission peak at 558 nm in all the samples. The intensity for Er- doped ZnO found maximum with additional Er shoulder peaks at 516nm and 538 nm. No Ce, Dy emission centers were found in spectra.

  16. Effect of Er doping on the superconducting properties of porous MgB2

    O Erdem; E Yanmaz


    MgB2 bulk sample with porous structure was produced by using the in-situ solid-state reaction method under argon (Ar) atmosphere of 10 bar. Elemental Er in powder form was doped into MgB2 with different compositions (Mg1−Er)B2, where = 0.00, 0.03 and 0.05, in order to investigate the effect of rare-earth (RE) element Er on the structural and electromagnetic properties of porous MgB2. The Er-doped samples result in small grain size structure compared to the undoped one. The lattice constants and of the doped samples, determined from X-ray diffraction (XRD) analysis, increase with the increasing Er content, and consequently the superconducting transition temperature ($T^{\\text{onset}}_{c}$) of MgB2, determined from resistivity measurements, is slightly suppressed. Also, the upper critical field ($B_{c2}$), the irreversibility field ($B_{\\text{irr}}$) and the critical current density ($J_{c}$) values are significantly enhanced in the doped samples. For the best sample ( = 0.03), at 15 K under a magnetic field of 4 T, the $J_{c}$ value reaches 2.4×104 A cm-2, which is higher than that of the porous sample by an order of 103, and the $B_{\\text{irr}}$ value at 20 K reaches 9.7 T. These results imply that the RE element Er fills the pores, enhances the density and the grain connectivity. Hence, the superconducting properties of the porous MgB2 sample improve by Er doping.

  17. Microstructure, Magnetism and Magnetic Field Induced-Strain in Er-Doped Co-Ni-Al Polycrystalline Alloy

    Ju, Jia; Lou, Shuting; Yan, Chen; Yang, Liu; Li, Tao; Hao, Shuai; Wang, Xingyi; Liu, Huan


    A large magnetic field-induced strain (MFIS) was discovered in single-crystal alloys, whereas it is proven difficult for such apparent strain values to be obtained in polycrystalline alloys. In order for an apparent strain discovery to occur, the polycrystalline Co-Ni-Al system was doped by 0-1 at.% of Er and the effects of doping on microstructure, magnetism and MFIS were studied via scanning electron microscopy, x-ray diffraction, transmission electron microscopy and vibrating sample magnetometer in the present work. The microstructure of the alloy was a dual-phase microstructure, including the matrix and the γ phase. Following the Er doping, the γ phase was continuously coarsened, forming a network of precipitates surrounding the grains. Also, a Co-Er-rich intermetallic compound was formed in the Co-rich γ phase when the Er content exceeded 0.1 at.%. The martensitic transformation temperature has a decreasing tendency during the Er being doped from 0 at.% to 1 at.% and the martensitic structure of the sample is of the L10 type, forming twin grains in the (111) twinning plane. On the contrary, the magnetic properties were improved by Er doping, especially saturation magnetization and magneto-crystalline anisotropy constantly increased to 60.45 emu/g and 3.13 × 106 erg/cm3 when the Er content reached 1 at.%, respectively. Also, the strain recovery ratio ( R s) of Co-Ni-Al-Er alloys can be enhanced by thermo-mechanical cycles and Er doping. At 5% of the total strain, the R s value exceeded 83% following thermo-mechanical cycles when the Er doping was 1 at.%. The strain in the applied magnetic field was increased by Er doping and an excess of 140 ppm of MFIS was obtained in the polycrystalline Co-Ni-Al-Er alloys.

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

    Surendra, T V; Roopan, Selvaraj Mohana


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

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

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


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

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

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


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

  1. Fe-Doped Polycrystalline CeO2 as Terahertz Optical Material

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


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

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

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


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

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

    Chunjie Wang


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

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

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


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

  5. Thermal Quenching of Photoluminescence from Er-Doped GaN Thin Films


    Journal of Alloys and Compounds 341 (2002) 62 –66 63 3 . Results and...The Er transitions are indicated by their initial state. All transitions terminate in the I ground state.15 / 2 64 J.T. Seo et al. / Journal of Alloys and Compounds 341...GaN 4 2 4( S / H → I ).3 / 2 11 / 2 15 / 2 J.T. Seo et al. / Journal of Alloys and Compounds 341 (2002) 62 –66 65 31decrease in IR Er PL lifetime

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

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


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

  7. Promoting effect of CeO2 on cyclohexanol conversion over CeO2-ZnO mixed oxide materials prepared by amorphous citrate process

    Braja Gopal Mishra; G Ranga Rao


    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 well-dispersed interstitial Zn$_{x}$Ce$^{4+}_{1-2x}$Ce$^{3+}_{2x}$O2 solid solution on ZnO matrix. Addition of CeO2 to ZnO produced high surface area mixed oxide materials in citrate method. Cyclohexanol conversion reaction was carried out on these catalytic materials to investigate the effect of rare earth oxide on the activity and selectivity. It was found that CeO2 promotes the activity of ZnO without affecting the selectivity to cyclohexanone significantly. The factors such as reaction temperature and WHSV have turned out to be important for cyclohexanol conversion over CeO2-containing ZnO catalyst materials.

  8. Synthesis of Diethyl Carbonate from Carbon Dioxide, Propylene Oxide and Ethanol over KNO3-CeO2 and KBr-KNO3-CeO2 Catalysts

    Yanlou Wang


    Full Text Available One-pot syntheses of diethyl carbonate (DEC from CO2, propylene oxide and ethanol were carried out using different solid catalysts. The supercritical CO2 extraction method was used to separate the liquid products and reactants from the catalysts after reaction. The KNO3-CeO2 and KBr-KNO3-CeO2 were found to be active for the reaction after calcinations. The catalyst was also reusable. The thermodynamic properties of the reaction were also evaluated. The effects of various conditions, such as reaction time, amount of catalysts, molar ratio of the reactants, the composition and calcination temperature of the catalysts on the conversion and yields, were investigated, and the yield of DEC was about 13.0% with a selectivity of 38.5% over KBr-KNO3-CeO2. The yield of DEC was improved about 10-fold by using KBr-KNO3-CeO2 catalyst compared to CeO2.

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

    XUYan-qing; CHENZhao-you


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

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

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


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

  11. CeO2-Co3O4 Catalysts for CO Oxidation

    Xu Xiuyan; Li Jinjun; Hao Zhengping


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

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

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


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

  13. Study on the protection of Er-doped phosphate glass waveguide surface in ion-exchange processing


    A novel method, sputtering K9 glass film, is proposed to solve the surface corrosion of Er-doped phosphate glass during ion-exchange processing for optical waveguide fabrication. The corrosion causes are analyzed to be the intrinsically weak stabilization of phosphate glass structure, hydrophile and weakly acidic property of phosphate radical. Experimental results show that the K9 glass film could not only protect the Er-doped phosphate glass surface from being corroded but also give no influence on the waveguide fabrication. The effect of thickness of K9 glass film on the optical property of waveguide is also investigated and the op- timal thickness is found to be 60―80 nm. It provides a good base for further fabri- cation of active phosphate glass optical waveguide devices.

  14. Microstructure and photoluminescence of Er-doped SiOx films synthesized by ion beam assisted deposition

    Duan Shu-Qing; Tan Na; Zhang Qing-Yu


    Er-doped Sio_ films were synthesized at 500℃ by ion beam assisted deposition technique and annealed at 800 and 1100℃ for 2h in the air atomosphere. The analysis by using energy dispersive x-ray spectroscopy showed that the ratio of Si to O decreased from 3 in the as-deposited films to about 1 in the annealed films. The investigation by using transmission electron microscopy and x-ray diffraction inducated that annealing induces a microstructure change from amorphous to crystlline. The grain sizes in the films were about 10 and 40nm when annealed at 800 and 1100℃, respectively. The films annealed at temperatures of 800 and 1100℃ exhibited a sharp photoluminescence (PL) at 1.533μm from the Er centres when pumped by 980nm laser. The influence of microstructure and grain size on the PL from Er-doped Sio_ films has been studies and discussed.

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


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


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


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

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

    Oman Zuas


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

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

    Arnaud Zenerino


    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.

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

    YANG Yuying; ZHANG Ziyu; HU Zhongai


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

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

    Maheswari, Nallappan; Muralidharan, Gopalan


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

  6. Synthesis, Characterization and Microwave Absorption Properties of Polyaniline/Er-Doped Strontium Ferrite Nanocomposite.

    Luo, Juhua; Wang, Eryong; Xu, Yang


    Er-doped strontium ferrite nanopowders (SrEr0.3Fe11.7O19) were prepared by the sol-gel method, and then their composites of PANI/SrEr0.3Fe11.7O19 with 10 wt% and 20 wt% ferrite were prepared by an in-situ polymerization process. The characterization of obtained samples was accomplished by XRD, FT-IR, TEM, VSM, and vector network analyzer techniques. A successful conjugation of ferrite nanoparticles with polyaniline could be indicated by XRD and FT-IR analysis. TEM confirmed the formation of polyaniline packed on strontium ferrite surface. Magnetization measurements showed the substituted Er3+ of Fe3+ on basis site enhanced the magnetic property notably and the content of polyaniline also influenced the magnetic property prominently. PANI/SrEr0.3Fe11.7O19 possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2-18 GHz. The value of the maximum RL was -42.0 dB at 12.0 GHz with the 5.5 GHz bandwidth.

  7. Spectroscopic properties of transparent Er-doped oxyfluoride glass-ceramics with GdF₃.

    Środa, Marcin; Szlósarczyk, Krzysztof; Różański, Marek; Sitarz, Maciej; Jeleń, Piotr


    Optically active glass-ceramics (GC) with the low-phonon phases of fluorides, doped with Er(3+) was studied. Glass based on SiO₂-Al₂O₃-Na₂F₂-Na₂O-GdF₃-BaO system was obtained. Dopant were introduced to the glass in an amount of 0.01 mol Er₂O₃ per 1 mol of glass. DTA/DSC study shows multi-stage crystallization. XRD identification of obtained phases did not confirm the presence of pure GdF₃ phase. Instead of that ceramization process led to formation of NaGdF₄ and BaGdF₅. The structural changes were studied using FT-IR spectroscopic method. The study of luminescence of the samples confirmed that optical properties of the obtained GC depend on crystallizing phases during ceramization. Time resolved spectroscopy of Er-doped glass showed the 3 and 8 times increase of lifetime of emission from (4)S₃/₂ and (4)F₉/₂ states, respectively. It confirms the erbium ions have ability to locate in the low phonon gadolinium-based crystallites. The results give possibility to obtain a new material for optoelectronic application.

  8. Investigation of the photosensitivity, temperature sustainability and fluorescence characteristics of several Er-doped photosensitive fibers

    Shen, Y H; Mandal, J; Sun, T; Grattan, K T V; Wade, S A; Collins, Stephen F; Baxter, Gregory W; Dussardier, Bernard; Monnom, Gérard


    Three different types of Er doped photosensitive fibers, germanium/erbium (Ge/Er) fiber, tin/germanium/erbium fiber (Sn/Er) and antimony/germanium/erbium fiber (Sb/Er) have been manufactured and studied for use in optical sensor systems. Their characteristics of photosensitivity, the temperature sustainability of fiber Bragg gratings (FBGs) written into these fibers and the fluorescence emission from the Er dopant were investigated and compared. It has been shown in this work that these fibers all show a satisfactory degree of photosensitivity to enable the fabrication of FBGs and a significant level of fluorescence emission within the 1550 nm band for sensor use. The high temperature sustainability of the FBGs written into these fibers was investigated and seen to be quite significant at temperatures as high as 850 ^{\\circ}C, in particular for the Sn/Er and Sb/Er fibers. A fiber laser using the Sb/Er fiber as the gain medium was demonstrated, giving evidence of the strong fluorescence emission from the Er do...

  9. Upconversion luminescence, ferroelectrics and piezoelectrics of Er Doped SrBi4Ti4O15

    Dengfeng Peng


    Full Text Available Er3+ doped SrBi4Ti4O15 (SBT bismuth layered-structure ferroelectric ceramics were synthesized by the traditional solid-state method, and their upconversion photoluminescent (UC properties were investigated as a function of Er3+ concentration and incident pump power. Green (555 nm and red (670 nm emission bands were obtained under 980 nm excitation at room temperature, which corresponded to the radiative transitions from 4S3/2, and 4F9/2 to 4I15/2, respectively. The emission color of the samples could be changed with moderating the doping concentrations. The dependence of UC intensity on pumping power indicated a two-photon emission process. Studies on dielectric properties indicated that the introduction of Er increased the ferroelectric-paraelectric phase transition temperature (Tc of SBT, thus making this ceramic suitable for piezoelectric sensor applications at higher temperatures. Piezoelectric measurement showed that the doped SBT had a relative higher piezoelectric constant d33 compared with the non-doped ceramics. The thermal annealing behaviors of the doped sample revealed a stable piezoelectric property. The doped SBT showed bright UC emission while simultaneously having increased Tc and d33. As a multifunctional material, Er doped SBT ferroelectric oxide showed great potential in application of sensor, future optical-electro integration and coupling devices.

  10. Down- and up-conversion emissions in Er-doped transparent fluorotellurite glass-ceramics

    Miguel, A.; Morea, R.; Gonzalo, J.; Fernandez, J.; Balda, R.


    In this work, we report the near infrared and upconversion emissions of Er3+-doped transparent fluorotellurite glassceramics obtained by heat treatment of the precursor Er-doped TeO2-ZnO-ZnF2 glass. Structural analysis shows that ErF3 nanocrystals nucleated in the glass-ceramic sample are homogeneously distributed in the glass matrix with a typical size of 45±10 nm. The comparison of the fluorescence properties of Er3+-doped precursor glass and glass-ceramic confirms the successful incorporation of the rare-earth into the nanocrystals. An enhancement of the red upconversion emission due to 4F9/2→4I15/2 transition together with weak emission bands due to transitions from 2H9/2, 4F3/2,5/2, and 4F7/2 levels to the ground state are observed under excitation at 801 nm in the glass-ceramic sample. The temporal evolution of the red emission together with the excitation upconversion spectrum suggest that energy transfer processes are responsible for the enhancement of the red emission.

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

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


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

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

    张进; 王冰; 崔皓; 李闯; 翟建平; 李琴


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

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

    XUYanqing; CHENKaixian


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

  14. Er-doped sesquioxides for 1.5-micron lasers - spectroscopic comparisons

    Merkle, Larry D.; Ter-Gabrielyan, Nikolay


    Due to the favorable thermal properties of sesquioxides as hosts for rare earth laser ions, we have recently studied the spectroscopy of Er:Lu2O3 in the 1400-1700 nm wavelength range, and here report its comparison with our earlier results on Er:Y2O3 and Er:Sc2O3. These studies include absorption and fluorescence spectra, fluorescence lifetimes, and inference of absorption and stimulated emission cross sections, all as a function of temperature. At room temperature, optical absorption limits practical laser operation to wavelengths longer than about 1620 nm. In that spectral range, the strongest stimulated emission peak is that at 1665 nm in Er:Sc2O3, with an effective cross section considerably larger than those of Er:Y2O3 and Er:Lu2O3. At 77K, the absorption is weak enough for efficient laser operation at considerably shorter wavelengths, where there are peaks with much larger stimulated emission cross sections. The three hosts all have peaks near 1575-1580 nm with comparably strong cross sections. As we have reported earlier, it is possible to lase even shorter wavelengths efficiently at this temperature, in particular the line at 1558 nm in Er:Sc2O3. Our new spectroscopic studies of Er:Lu2O3 indicate that its corresponding peak, like that of Er:Sc2O3, has a less favorable ratio of stimulated emission to absorption cross sections. Reasons for the differences will be discussed. We conclude that for most operating scenarios, Er:Sc2O3 is the most promising of the Er-doped sesquioxides studied for laser operation around 1.5-1.6 microns.

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

    FENG Xiaojuan; SHI Yanlong; ZHOU Huijuan


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

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

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


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

  17. Morphology-controllable synthesis and characterization of CeO2 nanocrystals

    Yangfeng Huang; Yebin Cai; Dongkai Qiao; Hao Liu


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

  18. Imaging the atomic surface structures of CeO2 nanoparticles

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


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

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

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


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

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

    Rodrigo F. Silva


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

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

    孟君晟; 吉泽升


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

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

    A Rangaswamy; Putla Sudarsanam; Benjaram M Reddy


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

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

    刘坚; 赵震; 徐春明; 段爱军; 姜桂元


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

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

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


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

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


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

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

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


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

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

    Ruishu Shang


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

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

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


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

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

    Mei, Donghai


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

  10. Dynamics of a Dispersion-Managed Passively Mode-Locked Er-Doped Fiber Laser Using Single Wall Carbon Nanotubes

    Norihiko Nishizawa


    Full Text Available We investigated the dynamics of a dispersion-managed, passively mode-locked, ultrashort-pulse, Er-doped fiber laser using a single-wall carbon nanotube (SWNT device. A numerical model was constructed for analysis of the SWNT fiber laser. The initial process of passive mode-locking, the characteristics of the output pulse, and the dynamics inside the cavity were investigated numerically for soliton, dissipative-soliton, and stretched-pulse mode-locking conditions. The dependencies on the total dispersion and recovery time of the SWNTs were also examined. Numerical results showed similar behavior to experimental results.

  11. Large net-normal dispersion Er-doped fibre laser mode-locked with a nonlinear amplifying loop mirror

    Bowen, Patrick; Broderick, Neil G R


    We report on an environmentally stable, all-PM-fibre, Er-doped, mode-locked laser with a central wavelength of 1550 nm. Significantly, the laser possesses large net-normal dispersion such that its dynamics are comparable to that of an all-normal dispersion fibre laser at 1 {\\mu}m with an analogous architecture. The laser is mode-locked with a nonlinear amplifying loop mirror to produce pulses that are externally compressible to 500 fs. Experimental results are in good agreement with numerical simulations.


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


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

  13. Optical application of Er-doped ZnO nanoparticles for photodegradation of direct red - 31 dye

    Bhatia, Sonik; Verma, Neha; Bedi, R. K.


    Nowadays, growing world increasing demands of synthetic organic dyes which are widely used in food, leather and textile industries. This paper reports the simple rapid synthesis of Er doped ZnO nanoparticles by simple combustion method. Herein, different concentrations of Er (2.0 at. wt%, 2.5 at. wt %, 3.0 at. wt%, 3.5 at. wt%) were used as dopants. The synthesized nanoparticles were characterized in term of structural, morphological, optical and kinetic properties. These detailed characterization study confirmed that the prepared nanoparticles are well crystalline. It was observed that different concentration of Er greatly influences morphology, band gap and photocatalytic activity on ZnO nanoparticles. The prepared Er doped samples were used as photocatalyst for photodegradation of direct red 31 (DR-31) dye. From the photocatalytic experiment it was observed that the degradation percentage increases with increasing Er concentration up to 2.5 at. wt% and thereafter photocatalytic degradation was decreased. Thus the optimum concentrations of prepared nanoparticles (2.5 at. wt%) are exhibiting almost complete degradation only in 60 min under UV irradiation. Kinetic studied revealed that all the samples follows first order rate constant.

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

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

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

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

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

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


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

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

    牟广宇; 魏清莲; 黄永民


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

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

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

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

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


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

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

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


    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.

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

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


    The factors affecting the chronic (72-h) toxicity of three nanoparticulate (10-34nm) and one micron-sized form of CeO2 to the green alga, Pseudokirchneriella subcapitata were investigated. To characterise transformations in solution, hydrodynamic diameters (HDD) were measured by dynamic light scatter, zeta potential values by electrophoretic mobility, and dissolution by equilibrium dialysis. The protective effects of humic and fulvic dissolved organic carbon (DOC) on toxicity were also assessed. To investigate the mechanisms of algal toxicity, the CytoViva hyperspectral imaging system was used to visualise algal-CeO2 interactions in the presence and absence of DOC, and the role of reactive oxygen species (ROS) was investigated by 'switching off' ROS production using UV-filtered lighting conditions. The nanoparticulate CeO2 immediately aggregated in solution to HDDs measured in the range 113-193nm, whereas the HDD and zeta potential values were significantly lower in the presence of DOC. Negligible CeO2 dissolution over the time course of the bioassay ruled out potential toxicity from dissolved cerium. The nanoparticulate CeO2 concentration that caused 50% inhibition of algal growth rate (IC50) was in the range 7.6-28mg/L compared with 59mg/L for micron-sized ceria, indicating that smaller particles were more toxic. The presence of DOC mitigated toxicity, with IC50s increasing to greater than 100mg/L. Significant ROS were generated in the nanoparticulate CeO2 bioassays under normal light conditions. However, 'switching off' ROS under UV-filtered light conditions resulted in a similar IC50, indicating that ROS generation was not the toxic mechanism. The CytoViva imaging showed negligible sorption of nanoparticulate CeO2 to algal cells in the presence of DOC, and strong sorption in its absence, suggesting that this was the toxic mechanism. The results suggest that DOC in natural waters will coat CeO2 particles and mitigate toxicity to algal cells. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

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

    Duangdao Channei


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

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

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


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

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

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


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

  5. Photoluminescence study of Er-doped zinc–sodium–antimonite glasses

    Zavadil, J., E-mail: [Institute of Photonics and Electronics AS CR, Prague (Czech Republic); Ivanova, Z.G. [Institute of Solid State Physics Bulgarian Academy of Sciences, Sofia (Bulgaria); Kostka, P. [Institute of Rock Structure and Mechanics AS CR, Prague (Czech Republic); Hamzaoui, M.; Soltani, M.T. [Laboratoire de Physique Photonique et Nanomatériaux, Universite de Biskra (Algeria)


    Highlights: • Optical gap found at around 3.1 eV and its compositional tendency was deduced. • Emission spectra are overwhelmed by narrow 4f–4f emission bands of Er{sup 3+}. • Fine structure of emission bands at 980 and 1530 nm measured at 300 and 4 K. • Schematic energy diagram of Stark levels for 3 lowest manifolds of Er{sup 3+} is proposed. • A nature of temperature broadening of 4f–4f PL bands was discussed. - Abstract: Bulk samples of Er-doped zinc–sodium–antimonite glasses have been investigated by transmission and photoluminescence (PL) spectroscopy. Two series of compositions, (Sb{sub 2}O{sub 3}){sub 90−x}(Na{sub 2}O){sub 10}(ZnO){sub x} and (Sb{sub 2}O{sub 3}){sub 80−x}(Na{sub 2}O){sub 20}(ZnO){sub x}, doped with 0.25 mol% Er{sub 2}O{sub 3}, have been chosen for this study. Transmission spectra exhibit sharp absorption bands centred at 450, 489, 521, 545, 652, 795, 975 and 1530 nm, which correspond to absorption of Er{sup 3+} ions and they are attributed to the optical transitions from the ground state {sup 4}I{sub 15/2} to the excited states {sup 4}F{sub 5/2}, {sup 4}F{sub 7/2}, {sup 2}H{sub 11/2}, {sup 4}S{sub 3/2}, {sup 4}F{sub 9/2}, {sup 4}I{sub 9/2}, {sup 4}I{sub 11/2} and {sup 4}I{sub 13/2}, respectively. The optical gap has been found to vary from 3.09 to 3.15 eV with a tendency to decrease at higher Na{sub 2}O and/or ZnO contents. Four extrinsic bands due to OH{sup −}, Si–O, CO{sub 2}, and (CO{sub 3}){sup 2−} carbonate group vibrations have been identified in the infrared region. Emission spectra are overwhelmed by narrow 4f–4f emission bands. Fine structure of emission bands at 980 and 1530 nm, corresponding to radiative transitions from two lowest excited states of Er{sup 3+} ions to the ground state manifold have been investigated at room temperature and at 4 K. A schematic energy diagram of Stark levels splitting for the three lowest manifolds {sup 4}I{sub 11/2}, {sup 4}I{sub 13/2} and {sup 4}I{sub 15/2} has been

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

    Jieqiong Zhang


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

  7. Interaction of Zr with oxidized and partially reduced ceria thin films

    Wang, Weijia; Hu, Shanwei; Han, Yong; Pan, Xiao; Xu, Qian; Zhu, Junfa


    The growth and electronic properties of Zr on the ceria thin films were studied by X-ray photoelectron spectroscopy, low energy electron diffraction (LEED), scanning tunneling microscopy (STM) and work function measurements. Metallic zirconium was vapor-deposited on the well-ordered fully oxidized CeO2(111) and partially reduced CeO2-x(111) (0 CeO2(111) thin film at low coverages due to the strong interaction between Zr and CeO2(111).

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

    S. Usharani


    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.

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

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


    To utilize visible light more effectively in photocatalytic reactions, a fly ash cenosphere (FAC)-supported CeO2-BiVO4 (CeO2-BiVO4/FAC) composite photocatalyst was prepared by modified metalorganic decomposition and impregnation methods. The physical and photophysical properties of the composite have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and UV-Visible diffuse reflectance spectra. The XRD patterns exhibited characteristic diffraction peaks of both BiVO4 and CeO2 crystalline phases. The XPS results showed that Ce was present as both Ce(4+) and Ce(3+) oxidation states in CeO2 and dispersed on the surface of BiVO4 to constitute a p-n heterojunction composite. The absorption threshold of the CeO2-BiVO4/FAC composite shifted to a longer wavelength in the UV-Vis absorption spectrum compared to the pure CeO2 and pure BiVO4. The composites exhibited enhanced photocatalytic activity for Methylene Blue (MB) degradation under visible light irradiation. It was found that the 7.5wt.% CeO2-BiVO4/FAC composite showed the highest photocatalytic activity for MB dye wastewater treatment. Copyright © 2014. Published by Elsevier B.V.

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

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


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

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

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


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

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

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


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

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

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


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

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

    D. Channei


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

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

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


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

  16. All-polarization-maintaining Er-doped ultrashort-pulse fiber laser using carbon nanotube saturable absorber.

    Nishizawa, N; Seno, Y; Sumimura, K; Sakakibara, Y; Itoga, E; Kataura, H; Itoh, K


    We present an all-polarization-maintaining Er-doped ultrashort-pulse fiber laser using a single-wall carbon nanotube polyimide nanocomposite saturable absorber. The maximum average power for single-pulse operation is 4.8 mW, and the repetition frequency is 41.3 MHz. Self-start and stable mode-locking operation is achieved. The RF amplitude noise is also examined and it is confirmed that the noise figure is as low as that of a solid-state laser. Using a polarization-maintaining anomalous dispersive fiber, a 314 fs output pulse is compressed to 107 fs via higher-order soliton compression. The peak power of the compressed pulse is up to 1.1 kW.

  17. Mechanoluminescence by impulsive deformation of {gamma}-irradiated Er-doped CaF{sub 2} crystals

    Brahme, Nameeta, E-mail: [School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur 492101 (India); Shukla, Manju, E-mail: [Institute of Technology, Guru Ghasidas Vishwavidyalaya, Bilaspur 495009 (India); Bisen, D.P.; Kurrey, U.; Choubey, Anil [School of Studies in Physics and Astrophysics, Pt. Ravishankar Shukla University, Raipur 492101 (India); Kher, R.S. [Department of Physics, Govt. Science P.G. College, Bilaspur 495006 (India); Singh, Manisha [Department of Physics, Dr. H.S. Gour University, Sagar (India)


    An impulsive technique has been used for mechanoluminescence (ML) measurements in {gamma}-irradiated Er doped CaF{sub 2} crystals. When the ML is excited impulsively by the impact of moving piston on to {gamma}-irradiated CaF{sub 2}:Er crystals, two peaks are observed in ML intensity with time and it is seen that the peak intensities of first and second peaks (I{sub m1} and I{sub m2}) increase with increasing impact velocity. However the time corresponding to first and second peaks (t{sub m1} and t{sub m2}) shifts towards shorter time values with increasing impact velocity. It is also seen that the total ML intensity I{sub Total} initially increases with the impact velocity and then it attains a saturation value for higher values of the impact velocity. We have presented a theoretical explanation for the observed results. - Research highlights: {yields} Impulsive technique has been used for mechanoluminescence (ML) studies in {gamma}-irradiated Er doped CaF{sub 2} crystals. {yields} ML intensity exhibited two peaks with time (I{sub m1} and I{sub m2}), where the intensity of both the peaks increased with increasing impact velocity. {yields} The time of occurrence of the peaks (t{sub m1} and t{sub m2}) reduced with increasing the impact velocity. {yields} Total ML intensity (I{sub Total}) first increases and then attains a saturation value with an increment in the impact velocity. {yields} A theoretical explanation is presented to the observed results.

  18. Dramatic enhancement of 1.54 μm emission in Er doped GaN quantum well structures

    Al tahtamouni, T. M. [Department of Physics, Yarmouk University, Irbid 21163 (Jordan); Stachowicz, M. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland); Li, J.; Lin, J. Y.; Jiang, H. X. [Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)


    Erbium (Er) doped III-nitride materials have attracted much attention due to their capability to provide highly thermal stable optical emission in the technologically important as well as eye-safer 1540 nm wavelength window. There is a continued need to exploring effective mechanisms to further improve the quantum efficiency (QE) of the 1.54 μm emission in Er-doped III-nitrides. GaN/AlN multiple quantum wells (MQWs:Er) have been synthesized by metal organic chemical vapor deposition and explored as an effective means to improve the QE of the 1.54 μm emission via carrier confinement and strain engineering. The 1.54 μm emission properties from MQWs:Er were probed by photoluminescence (PL) emission spectroscopy. It was found that the emission intensity from MQWs:Er is 9 times higher than that of GaN:Er epilayers with a comparable Er active layer thickness. The influences of the well and barrier width on the PL emission at 1.54 μm were studied. The results revealed that MQWs:Er consisting of well width between 1 and 1.5 nm and the largest possible barrier width before reaching the critical thickness provide the largest boost in QE of the 1.54 μm emission. These results demonstrate that MQWs:Er provide a basis for efficient photonic devices active at 1.54 μm.

  19. Local microstructure and photoluminescence of Er-doped 12CaO·7Al2O3 powder

    WANG Dan; LIU Yuxue; XU Changshan; LIU Yichun; WANG Guorui; LI Xinghua


    Er-doped 12CaO·7Al2O3 (C12A7:Er) powders were prepared using the sol-gel method followed by annealing inorganic precursors. X-ray diffraction (XRD), Raman and absorption spectra revealed that Er ions existed and substituted Ca2+ lattice site in C12A7. The photoluminescence of C12A7:Er at room temperature was observed in the visible and infrared region using 488 nm (2.54 eV) Ar+ line as excitation source, respectively. The sharp and intense green emission bands with multi-peaks around 520 nm and 550 nm correspond to the transitions from the excited states 2H11/2 and 4S3/2 to the ground state 4I15/2, respectively. Furthermore, red emission band around 650 nm was also observed. It was attributed to the electronic transition from excited states 4F9/2 to the ground state 4I15/2 inside 4f-shell of Er3+ ions. The intensive infrared emission at 1.54μm was attributed to the transition from the first excited states of 4I13/2 to the ground state (4I15/2). The temperature dependent photoluminescence of infrared emission showed that the integrated intensity reached a maximum value at near room temperature. The forbidden transitions of intra-4f shell electrons in free Er3+ ions were allowed in C12A7 owing to lack of the inversion symmetry in the Er3+ position in C12A7 crystal field. Our results suggested that C12A7:Er was a candidate for applications in Er-doped laser materials, and full color display.

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

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


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

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

    Chunjie Wang


    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.

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

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


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

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

    Anushree, Sharma, C.; Kumar, S.


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

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

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


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

  5. Cell uptake, intracellular distribution, fate and reactive oxygen species generation of polymer brush engineered CeO2-x NPs

    Qiu, Yuan; Rojas, Elena; Murray, Richard A.; Irigoyen, Joseba; Gregurec, Danijela; Castro-Hartmann, Pablo; Fledderman, Jana; Estrela-Lopis, Irina; Donath, Edwin; Moya, Sergio E.


    Cerium Oxide nanoparticles (CeO2-x NPs) are modified with polymer brushes of negatively charged poly (3-sulfopropylmethacrylate) (PSPM) and positively charged poly (2-(methacryloyloxy)ethyl-trimethylammonium chloride) (PMETAC) by Atom Transfer Radical Polymerisation (ATRP). CeO2-x NPs are fluorescently labelled by covalently attaching Alexa Fluor® 488/Fluorescein isothiocyanate to the NP surface prior to polymerisation. Cell uptake, intracellular distribution and the impact on the generation of intracellular Reactive Oxygen Species (ROS) with respect to CeO2-x NPs are studied by means of Raman Confocal Microscopy (CRM), Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). PSPM and PMETAC coated CeO2-x NPs show slower and less uptake compared to uncoated Brush modified NPs display a higher degree of co-localisation with cell endosomes and lysosomes after 24 h of incubation. They also show higher co-localisation with lipid bodies when compared to unmodified CeO2-x NPs. The brush coating does not prevent CeO2-x NPs from displaying antioxidant properties.Cerium Oxide nanoparticles (CeO2-x NPs) are modified with polymer brushes of negatively charged poly (3-sulfopropylmethacrylate) (PSPM) and positively charged poly (2-(methacryloyloxy)ethyl-trimethylammonium chloride) (PMETAC) by Atom Transfer Radical Polymerisation (ATRP). CeO2-x NPs are fluorescently labelled by covalently attaching Alexa Fluor® 488/Fluorescein isothiocyanate to the NP surface prior to polymerisation. Cell uptake, intracellular distribution and the impact on the generation of intracellular Reactive Oxygen Species (ROS) with respect to CeO2-x NPs are studied by means of Raman Confocal Microscopy (CRM), Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). PSPM and PMETAC coated CeO2-x NPs show slower and less uptake compared to uncoated Brush modified NPs display a higher degree of co-localisation with cell endosomes and lysosomes after 24 h of incubation. They also show higher co-localisation with lipid bodies when compared to unmodified CeO2-x NPs. The brush coating does not prevent CeO2-x NPs from displaying antioxidant properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00884k

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

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


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


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


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

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

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


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

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

    李霞; 张羊换; 杨泰; 许剑轶; 赵栋梁


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

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

    Oman ZUAS


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

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

    YAN Kai; ZHEN Qiang; Song Xiwen


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

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

    Phuong Thi Mai Pham


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

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

    Zhao, He; Zhang, Guangming; Zhang, Quanling


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

  14. Synthesis of CeO2-based core/shell nanoparticles with high oxygen storage capacity

    Uzunoglu, Aytekin; Kose, Dursun Ali; Stanciu, Lia A.


    Ceria plays a key role in various applications including sensing and catalysis owing to its high oxygen storage capacity (OSC). The aim of this work is to prepare novel MO x /CeO2 (M: Zr, Ti, Cu) metal oxide systems with core/shell structures using a facile two-step chemical precipitation method. The synthesized nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption methods. The OSC property of the samples was evaluated using TGA analysis conducted at 600 °C under reductive (5% H2/Ar) and oxidative (synthetic air) environments. The OSCs of the samples were found to be 130, 253, and 2098 µmol-O2/g for ZrO2/CeO2, TiO2/CeO2, and CuO/CeO2, respectively. Effects of heat treatment on the physical and redox properties of the samples were also evaluated. In this regard, the samples were exposed to 500 °C for 5 h under ambient environment. It was observed that the heat treatment induced the formation of mixed metal oxide alloys and the BET surface area of the samples diminished significantly. The OSC of the samples, however, did not experience any significant chance, which was attributed to the compensation of the loss in the surface area by the alloy formation after the heat treatment.

  15. Laser-induced evaporation, reactivity and deposition of ZrO 2, CeO 2, V 2O 5 and mixed Ce-V oxides

    Flamini, C.; Ciccioli, A.; Traverso, P.; Gnecco, F.; Giardini Guidoni, A.; Mele, A.


    It has been found that pulsed laser ablation has good potentiality for the deposition of ZrO2, CeO2, V2O5 and mixed Ce-V oxides which are very important materials for their application in optics and electrochromic devices. Laser induced compositional changes of thin films in the ablation and deposition processes of these materials have been explored. The effect of the oxygen gas pressure on the thin film composition has been examined. The congruency of the process has been treated on the basis of a thermal mechanism of evaporation-decomposition of the compounds. An attempt to model the processes by means of a thermodynamic approach is reported.


    Livia Vittori Antisari


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

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

    Develos, Katherine; Kusunoki, Masanobu; Ohshima, Shigetoshi


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

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

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


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

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

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


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

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

    Xu, H. F.; Li, H.


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

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


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

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

    Shi Hong Zhang et al


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

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

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


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

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

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


    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, Cr23C6 and Ni3B 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.

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

    胡辉; 李劲; 程国宏; 李胜利


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

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

    Phanichphant, Sukon; Nakaruk, Auppatham; Channei, Duangdao


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

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

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


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

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

    詹望成; 张欣烨; 郭杨龙; 王丽; 郭耘; 卢冠忠


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

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

    Zhang Zhenyu; Wang Zhiping; Liang Bunü


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

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

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


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

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

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


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

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


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

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

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


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

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

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


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

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

    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


    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.

  16. Different heat treatment of CeO2 nanoparticle composited with ZnO to enhance photocatalytic performance

    Taufik, A.; Shabrany, H.; Saleh, R.


    In this study, ZnO/CeO2 nanocomposites were prepared with four variations of the molar ratio of ZnO to CeO2 nanoparticles. Both ZnO and CeO2 nanoparticles were synthesized using the sol-gel method at low temperature, followed by different heat treatments for CeO2 nanoparticles. Thermal phase transformation studies of the CeO2 nanoparticles were observed at annealing temperatures of 400-800°C. The complete crystalline structure of CeO2 nanoparticles was obtained at an annealing temperature of 800°C. The structural and optical properties of all samples were observed using several characterization techniques, such as X-ray diffraction (XRD), ultraviolet-visible diffuse reflectance spectroscopy, and Brunauer, Emmett, and Teller (BET) surface area analysis. The structural characterization results revealed that the prepared CeO2 nanoparticles were quite crystalline, with a cubic structure. The photocatalytic activities of all samples were tested under visible irradiation. The obtained results showed that ZnO/CeO2 nanocomposites with a molar ratio 1:0.3 exhibited the highest photocatalytic activity. Further understanding of the role of primary active species underlying the reaction mechanism involved in photocatalytic activity were carried out in controlled experiments by adding several scavengers. The detailed mechanism and its correlation with the properties of ZnO/CeO2 nanocomposites were discuss.

  17. Exposure of agricultural crops to nanoparticle CeO2 in biochar-amended soil.

    Servin, Alia D; De la Torre-Roche, Roberto; Castillo-Michel, Hiram; Pagano, Luca; Hawthorne, Joseph; Musante, Craig; Pignatello, Joseph; Uchimiya, Minori; White, Jason C


    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) CeO2 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 CeO2 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 CeO2. 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.

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

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


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

  19. Facile method for fabrication of surfactant-free concentrated CeO2 sols

    Shcherbakov, Alexander B.; Teplonogova, Maria A.; Ivanova, Olga S.; Shekunova, Taisiya O.; Ivonin, Ivan V.; Baranchikov, Alexander Ye; Ivanov, Vladimir K.


    We report a facile method for fabrication of highly concentrated electrostatically stabilized colloidal solutions containing ultra-small cerium (IV) oxide crystallites having a narrow size distribution (3-5 nm according to x-ray diffraction, and 10-30 nm according to dynamic light scattering). The proposed method comprises hydrothermal treatment of ceric ammonium nitrate aqueous solutions having concentrations over 0.2 M, in the temperature range of 80-100 °C, and the formation of nanoceria sediments, which can be easily peptized in both protic (water, isopropanol) and aprotic (DMF) media, forming stable and transparent CeO2 sols.

  20. 2D Layered Materials of Rare-Earth Er-Doped MoS2 with NIR-to-NIR Down- and Up-Conversion Photoluminescence.

    Bai, Gongxun; Yuan, Shuoguo; Zhao, Yuda; Yang, Zhibin; Choi, Sin Yuk; Chai, Yang; Yu, Siu Fung; Lau, Shu Ping; Hao, Jianhua


    A 2D system of Er-doped MoS2 layered nanosheets is developed. Structural studies indicate that the Er atoms can be substitutionally introduced into MoS2 to form stable doping. Density functional theory calculation implies that the system remains stable. Both NIR-to-NIR up-conversion and down-conversion light-emissions are observed in 2D transition metal dichalcogenides, ascribed to the energy transition from Er(3+) dopants.

  1. Pulsed Laser Deposition of Er doped tellurite films on large area

    Bouazaoui, M [Laboratoire PhLAM, UMR 8523, Groupe Photonique, Universite des Sciences et Technologies de Lille, 59655 Villeneuve d' Ascq Cedex (France); Capoen, B [Laboratoire PhLAM, UMR 8523, Groupe Photonique, Universite des Sciences et Technologies de Lille, 59655 Villeneuve d' Ascq Cedex (France); Caricato, A P [L3 group, Dipartimento di Fisica, Lecce, Via Arnesano, 73100 Lecce (Italy); Chiasera, A [CNR-IFN, CSMFO group, via Sommarive 14, 38100 Povo-Trento (Italy); Fazzi, A [L3 group, Dipartimento di Fisica, Lecce, Via Arnesano, 73100 Lecce (Italy); Ferrari, M [CNR-IFN, CSMFO group, via Sommarive 14, 38100 Povo-Trento (Italy); Leggieri, G [L3 group, Dipartimento di Fisica, Lecce, Via Arnesano, 73100 Lecce (Italy); Martino, M [L3 group, Dipartimento di Fisica, Lecce, Via Arnesano, 73100 Lecce (Italy); Mattarelli, M [Physics Department, CSMFO group, via Sommarive 14, 38100 Povo-Trento (Italy); Montagna, M [Physics Department, CSMFO group, via Sommarive 14, 38100 Povo-Trento (Italy); Romano, F [L3 group, Dipartimento di Fisica, Lecce, Via Arnesano, 73100 Lecce (Italy); Tunno, T [L3 group, Dipartimento di Fisica, Lecce, Via Arnesano, 73100 Lecce (Italy); Turrel, S [Universite des Sciences et Technologies de Lille, Laboratoire de Spectrochimie Infrarouge et Raman, LASIR - UMR 8516 du CNRS - Bat C5 - 59655 - Villeneuve d' Ascq cedex (France); Vishnubhatla, K [Physics Department, CSMFO group, via Sommarive 14, 38100 Povo-Trento (Italy)


    Thin films of Er{sup 3+}-doped tungsten tellurite glass have been prepared by the pulsed laser deposition technique using an ArF excimer laser. The depositions were performed at different O{sub 2} pressure (5, 10 Pa) and at different substrate temperatures (RT, 100deg. C and 200deg. C). The composition and the optical properties of the deposited films, such as transmission, dispersion curves of refraction index and extinction coefficient, and film thickness were studied for the different deposition parameters. Transparent films at the highest substrate temperature were obtained only for a higher oxygen pressure with respect to the RT conditions.

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

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


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

  3. Enhanced photocatalytic performance of Er-doped Bi{sub 24}O{sub 31}Br{sub 10}: Facile synthesis and photocatalytic mechanism

    Liu, Zhang Sheng, E-mail:; Liu, Zhi Lin; Liu, Jin Long; Zhang, Jing Wen; Zhou, Ting Fei; Ji, Xiang


    Highlights: • Er-doped Bi{sub 24}O{sub 31}Br{sub 10} have been prepared via a one-pot solvothermal method. • Er doping drastically improves the photocatalytic activity of Bi{sub 24}O{sub 31}Br{sub 10}. • The enhanced activity is attributed to effective electron trapping and up-conversion process resulting from Er{sup 3+}. • Holes and super-oxide radicals are main active species. - Abstract: Erbium (Er) doped Bi{sub 24}O{sub 31}Br{sub 10} samples were successfully prepared by using a solvothermal method. The samples were characterized by XRD, XPS, SEM, TEM, BET, DRS, PL and EIS. The photocatalytic activity was evaluated by the degradation of rhodamine B (RhB) and methyl orange (MO) under visible light irradiation. The result shows that Er dopant induces a significant improvement in the photocatalytic activity. 1.0% Er–Bi{sub 24}O{sub 31}Br{sub 10} sample exhibits the best photocatalytic performance. The enhanced photocatalytic activity is attributed to the effective trapping of photogenerated electron by Er{sup 3+} ion and the up-conversion process resulting from Er dopant. In addition, it is found that holes and super-oxide radicals play main role in the photocatalytic degradation of RhB and MO.

  4. Time delay and excitation mode induced tunable red/near-infrared to green emission ratio of Er doped BiOCl

    Avram, Daniel; Florea, Mihaela; Tiseanu, Ion; Tiseanu, Carmen


    Herein, we report on the emission color tunability of Er doped BiOCl measured under up—conversion as well as x-ray excitation modes. The dependence of red (670 nm) to green emission (543 nm) ratio on Er concentration (1 and 5%), excitation wavelength into different (656.4, 802 and 976 nm) or across single Er absorption levels (965 ÷ 990 nm) and delay after the laser pulse (0.001 ÷ 1 ms) is discussed in terms of ground state absorption/excited state absorption and energy transfer up-conversion mechanisms. A first example of extended Er x-ray emission measured in the range of 500 to 1700 nm shows comparable emission intensities corresponding to 543 nm and 1500 nm based transitions. The present results together with our earlier report on the upconversion emission of Er doped BiOCl excited at 1500 nm, suggest that Er doped BiOCl may be considered an attractive system for optical and x-ray imaging applications.

  5. First principles study of the magnetism driven by cation defects in CeO2: the important role of O2p states

    Lu Zhan-Sheng; Ma Dong-Wei; Zhang Jing; Xu Guo-Liang; Yang Zong-Xian


    The magnetism driven by cation defects in undoped CeO2 bulk and thin films is studied by the density functional theory corrected for on-site Coulomb interactions (DFT+U) with U =5 eV for the Ce4f states and U =7 eV for the O2p states.It is found that the Ce vacancies can induce a magnetic moment of the ~ 4 μB/supercell,which arises mainly from the 2p hole state of the nearest neighbouring O atom (~ 1 μB on per oxygen) to the Ce vacancy.The effect of the methodology is investigated,indicating that U =7 eV for the O2p state is necessary to obtain the localized O2p hole state in defective ceria with cation vacancies.

  6. CeO2-Co3O4纳米晶粒对甲烷气敏性影响分析%Methane Gas-sensitive Property Analysis Influenced by CeO2-Co3O4 Nanocrystalline

    曹小荣; 胡明江


    为了快速准确检测矿井中的甲烷气体浓度,以直接沉淀法制备了不同含量CeO2的CeO2-Co3 O4纳米晶粒。利用掩膜法将制备的CeO2-Co3 O4纳米晶粒镀膜于氧化硅绝缘层表面形成敏感薄膜,采用标准MEMS工艺制作了一种薄膜型甲烷传感器。采用 X 射线衍射仪表征了CeO2-Co3 O4纳米晶粒的相组成和微观形貌,利用全自动程序化学吸附仪分析了CeO2-Co3 O4纳米晶粒对甲烷的吸附机理。在气体传感器静态测试系统上,测试了甲烷传感器灵敏度、湿度、温度、动态响应、抗干扰和长期稳定性等特性。结果表明:以Ce30为敏感薄膜的甲烷传感器灵敏度为98.3%,动态响应时间为11 s,恢复时间为8 s。在矿井中连续使用12个月后,灵敏度衰减了8.5%。表明该甲烷传感器可实现矿井中甲烷气体在线检测。%In order to detect methane concentration in mine quickly and accurately,CeO2-Co3O4 nanocrystalline were pre-pared by direct precipitation method.CeO2-Co3O4 nanocrystalline was deposited onto the insulating layer of silicon oxide surface by mask method.A new film-type methane gas sensor was designed by micro electro mechanical system.The crystalline phase and microstructure of CeO2-Co3 O4 nanocrystalline were displayed using X-ray diffraction ( XRD) and field emission scanning electron microscope ( FE-SEM ) , methane adsorption mechanism of CeO2-Co3 O4 nanocrystalline were analyzed by automatic program chemisorption analyzer.These characteristic tests of methane gas sensors were carried out on the traits of sensitive performance, temperature,relative humidity,dynamic response,interference and long-term stability in gas sensor static test system.The conclu-sion demonstrates that the sensitivity of methane gas sensor based on Ce30 sensitive thin film was 98.3%,the dynamic response time and recover time of methane gas sensor were 11 s and 8 s respectively.The sensitivity of methane gas sensor was attenuated about 8

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

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


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

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

    Mohammad Sadegh Shakeri


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

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

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


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

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

    Ling Liu


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

  11. Synthesis and Electrical Conductivities of Sm2O3-CeO2 Systems

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


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

  12. Electrical and microstructural properties of Yb-doped CeO2

    B. Matović


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

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

    Ying Huang


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

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

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


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

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

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


    An important aspect in risk assessment of nanoparticles (NPs) is to understand their environmental interactions. We used hydroponic plant cultures to study nanoparticle-plant-root interaction and translocation and exposed wheat and pumpkin to suspensions of uncoated CeO2-NP for 8d (primary particle size 17-100 nm, 100 mg L(-1)) in the absence and presence of fulvic acid (FA) and gum arabic (GA) as representatives of different types of natural organic matter. The behavior of CeO2-NPs in the hydroponic solution was monitored regarding agglomeration, sedimentation, particle size distribution, surface charge, amounts of root association, and translocation into shoots. NP-dispersions were stable over 8d in the presence of FA or GA, but with growing plants, changes in pH, particle agglomeration rate, and hydrodynamic diameter were observed. None of the plants exhibited reduced growth or any toxic response during the experiment. We found that CeO2-NPs translocated into pumpkin shoots, whereas this did not occur in wheat plants. The presence of FA and GA affected the amount of CeO2 associated with roots (pure>FA>GA) but did not affect the translocation factor. Additionally, we could confirm via TEM and SEM that CeO2-NPs adhered strongly to root surfaces of both plant species. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

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


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

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

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


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

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

    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


    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).

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

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


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

  20. Effect of CeO2 coprecipitation on the electrochemical performance of Li(Li,Ni,Mn,Co)O2-CeO2-C composite cathode materials

    Kurilenko, K. A.; Shlyakhtin, O. A.; Petukhov, D. I.; Garshev, A. V.


    Composite electrode materials Li[Li0.13Ni0.2Mn0.47Co0.2]O2 (LNMC)-CeO2-C are obtained by the coprecipitation of Co, Ni, Mn and Ce hydroxides followed by the coating of LNMC-CeO2 composites with pyrolytic carbon. The introduction of 5% CeO2 promotes the reduction of LNMC grain size from 190-230 to 100-170 nm and the corresponding increase in the electrochemical capacity of LNMC-CeO2 composite. The pyrolytic coating consists of the network of 2-5 nm polymer-carbon particles at the surface of LNMC crystallites. The electrochemical impedance spectroscopy data, which was performed after the galvanostatic cycling, demonstrated considerably lower charge transfer resistance of the carbon-coated composites compared to the bare LNMC and the LNMC-CeO2 composites. The values of the discharge capacity of LNMC-CeO2-C composites are superior to the capacity of LMNC-CeO2 and LMNC-C composites at all discharge rates (C/10 - 5C). The increase of the upper boundary of potentials to 4.8 V after cycling at 5C (U - 2÷4.6 V) promotes the increase of low rate electrochemical capacity of LNMC-CeO2-C composite to 220 mAh g-1.

  1. CeO2掺杂对HfO2栅介质电学特性的影响%Influence of CeO2-Doping on Electrical Properties of HfO2 Gate Dielectrics

    杨萌萌; 屠海令; 张心强; 熊玉华; 王小娜; 杜军


    采用磁控共溅射的方法在p-Si(100)衬底上沉积了掺杂和不掺杂CeO2的HfO2薄膜.通过X射线光电子能谱(XPS)研究了薄膜中元素的化学计量比及结合能,制备MOS结构并对漏电流及电容等电学性能进行表征.结果表明,掺入CeO2后,整个体系的氧空位生成能增大,氧空位数目减少,漏电流较纯HfO2下降了一个数量级,满足作为高k材料的要求.%CeO2-doped HfO2(CDH) thin films were deposited on p-Si substrates by RF magnetron co-sputtering. The film thickness was measured by surface profiler. The binding energy of elements was characterized by X-ray photoelectron spectroscopy ( XPS). MOS structures were made to characterize the leakage current and capacitance. XPS analysis of Hf 4f and 01s confirmed that the Hf-0 binding energy increased after doping CeO2. This resulted in the increase of the oxygen vacancy formation energy and the reduction of the concentration of oxygen vacancy. The leakage current density of CDH film was about one order of magnitude lower than that of HfO2 film. CDH film can meet the requirements of high-fc application.

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

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


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

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

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


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

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

    Jiaheng Wang


    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.

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

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


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

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

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


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

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

    Chyuan Haur Kao


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

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

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


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

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

    SUN Qingchi; LU Cuimin; ZHOU Hua


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

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

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


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

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

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


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

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


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

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


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

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

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


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

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

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


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

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

    邵建军; 朱锡; 张永坤; 王明贵


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

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

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


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

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

    苏盛彪; 包亦望; 王黎; 李竟先


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

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

    Panpan Guan


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

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

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


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

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

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


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

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

    Mullins, David R.


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

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

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


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

  4. Up to 400 GHz burst-mode pulse generation from a hybrid harmonic mode-locked Er-doped fibre laser

    Wang, Sheng-Min; Lai, Yinchieh


    By inserting a birefringence filter with FSR  =  100 GHz inside a hybrid mode-locked Er-doped fibre laser, we successfully generate ps to sub-ps optical burst pulses with the intra-burst pulse rate up to 400 GHz. Multiplication of the intra-burst pulse rate is attributed to a new effect analogous to rational harmonic mode-locking, which occurs due to the relative alignment of the cavity harmonic frequencies, the external phase modulation induced frequencies, and the filter-selected frequencies.

  5. Effects of refractive index changes on four-wave mixing bands in Er-doped photonic crystal fibers pumped at 976 nm.

    Velázquez-Ibarra, L; Díez, A; Andrés, M V; Lucio, J L


    An experimental study of the effects of an auxiliary 976 nm pump signal on the four-wave mixing parametric bands generated with a 1064 nm pump in a normal dispersion Er-doped photonic crystal fiber is presented. The four-wave mixing signal and idler bands shift to shorter and longer wavelengths, respectively, with increasing 976 nm pump power. It is shown that the wavelength-dependent resonant refractive index change in the erbium-doped core under 976 nm pumping is at the origin of the effect.

  6. High energy, 1572.3 nm pulses for CO2 LIDAR from a polarization-maintaining, very-large-mode-area, Er-doped fiber amplifier.

    Nicholson, J W; DeSantolo, A; Yan, M F; Wisk, P; Mangan, B; Puc, G; Yu, A W; Stephen, M A


    We demonstrate the first polarization-maintaining, very-large-mode-area, Er-doped fiber amplifier with ~1100 μm2 effective area. The amplifier is core pumped by a Raman fiber laser and is used to generate single-frequency, one-microsecond, pulses with pulse energy of 541 μJ, peak power of 700 W, M2 of 1.1, and polarization extinction > 20 dB. The amplifier operates at 1572.3 nm, a wavelength useful for trace atmospheric CO2 detection.

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

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

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

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


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

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

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


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

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

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


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

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

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


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

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

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

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

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


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

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

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


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

  15. Er-doped and Er, Yb co-doped oxyfluoride glasses and glass-ceramics, structural and optical properties

    Lisiecki, Radosław; Augustyn, Elżbieta; Ryba-Romanowski, Witold; Żelechower, Michał


    -ceramic fibers indicate that these optical systems may be considered as promising materials for Er-doped optical amplifiers operating within third telecommunication window.

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

    Zhang, Zhenyu; Liang, Bunv; Guo, Hongjian


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

  17. Effect of the Cerium Oxide (CeO2) on the Structural and Electrochemical Properties of the LaNi5Ce Metal Hydride Anode

    Utami Hapsari, Ade; Zulfia, Anne; Raharjo, Jarot; Agustanhakri


    One of negative electrode, AB5-type alloy electrodes, have been extensively studied and applied in rechargeable Ni-MH batteries due to their excellent electrochemical characteristics. Some researchers have found that addition of rare earth oxides (La, Ce, Pr, Er, Tm, Yb) to AB5-type alloy (MH) electrode improves battery performance significantly. Cerium Oxide (CeO2) is a light rare earth oxide is widely obtained from the processing of tailings in mining activities. During this time, there is still little data for research applications of cerium oxide for electrode materials. In this paper, the effects of adding CeO2 on the performance metal hydride electrode were investigated. In order to study the effects of CeO2 on the performance of anode material, 1%, 2%, and 3% of weight ratio CeO2 was mixed to LaNi5 as an negative electrode. The powder mixtures were mechanically milled at a speed of rpm 240 for 2 hours using ball mill. The powder mixtures were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Electrochemical characteristics were measured using electrochemical impedance spectroscopy (EIS). The powder mixing showed the presence of Ce atom substitution into LaNi5 structures that affect the electrochemical properties of the material. The addition of cerium oxide at LaNi5 increase of the value of impedance. However, the addition of the value of impedance at 1% CeO2 is not significant when compared with the addition of 2% and 3% CeO2 that actually make the electrochemical properties of LaNi5 worst. Although the addition of 1% CeO2 also slightly increases the impedance value of LaNi5, but the addition of 1% CeO2 showed increase the corrosion resistance than without the addition of CeO2 and the addition of 2% and 3% CeO2.

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

    Uzunoglu, Aytekin; Stanciu, Lia A


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

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

    Jin Huiming; Zhang Linnan; Liu Xiaojun


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

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

    Reimers, Walter G.; Branda, María M.


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

  1. Configurational affects on the compaction response of CeO2 powders

    Dattelbaum D.


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

  2. Biogenic synthesis and catalysis of porous CeO2 hollow microspheres

    CHEN Feng; WANG Wei; CHEN Zhigang; WANG Taibin


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

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

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


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

  4. Functional Paper-Based Platform for Rapid Capture and Detection of CeO2 Nanoparticles.

    Othman, Ali; Andreescu, Daniel; Karunaratne, Dinusha P; Babu, S V; Andreescu, Silvana


    Development of systems for capture, sequestration, and tracking of nanoparticles (NPs) is becoming a significant focus in many aspects of nanotechnology and environmental research. These systems enable a broad range of applications for evaluating concentration, distribution, and effects of NPs for environmental, clinical, epidemiological, and occupational exposure studies. Herein, we describe the first example of a ligand-graft multifunctional platform for capture and detection of cerium oxide (CeO2 or ceria) NPs. The approach involves the use of redox-active ligands containing o-dihydroxy functionality, enabling multivalent binding, surface retention, and formation of charge transfer complexes between the grafted ligand and the NPs. Using this strategy, paper-based and microarray-printed platforms with NP-capture ability involving either catechol or ascorbic acid as ligands were successfully fabricated. Surface modification was determined by infrared spectroscopy, electron microscopy, X-ray spectroscopy, and thermogravimetric analysis. Functionality was demonstrated for the rapid assessment of NPs in chemical mechanical planarization (CMP) slurries and CMP wastewaters. This novel approach can enable further development of devices and separation technologies including platforms for retention and separation of NPs and measurement tools for detection of NPs in various environments.

  5. Stability and Temperature-Induced Agglomeration of Rh Nanoparticles Supported by CeO2.

    Varga, Erika; Pusztai, Péter; Oszkó, Albert; Baán, Kornélia; Erdőhelyi, András; Kónya, Zoltán; Kiss, János


    The effects of reduction by H2 and by heat treatment in vacuum and in O2 flow on Rh particle size changes of Rh/CeO2 samples were studied by X-ray photoelectron spectroscopy (XPS), high-resolution electron microscopy (HRTEM), and CO adsorption followed by diffuse reflectance infrared spectroscopy (DRIFTS). Low-temperature (373-423 K) reduction of Rh without agglomeration is demonstrated. An average particle size of 2.3 ± 1.1 nm was measured by HRTEM regardless of the metal loading (1-5%). On Rh/CeO2, a significant particle size increase of the Rh particles was detected on heating (773 K). In this work, we suggest that the temperature-induced surface decrease resulting from the sintering of Rh is favored only for well-dispersed particles. XP spectra revealed that the mobile oxygens of CeO2 fundamentally determine the oxidation state of the supported metals. At elevated temperature, the oxidation of the reduced support surface as well as the metal component takes place because of the segregation of ceria oxygens. When the aggregated particles were reoxidized, the redispersion of Rh was observed probably because of the formation of Rh-O-Ce bonds.

  6. Enhancement of room temperature ferromagnetic behavior of rf sputtered Ni-CeO2 thin films

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


    Ni-doped CeO2 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 CeO2 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 CeO2 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 CeO2. Room-temperature photoluminescence (PL) and micro-Raman spectroscopic studies revealed an increase of oxygen vacancies with higher concentration of Ni in CeO2. XPS results confirm the presence of Ni2p, O1s and Ce and depict that cerium is present as both Ce4+ and Ce3+ oxidation states in Ce1-xNixO2 (x = 15%) thin film. Field dependent magnetization measurements revealed a paramagnetic behavior for pure CeO2, while a ferromagnetic behavior appeared when Ni is doped in CeO2 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.

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

    Li Xingeng; Wang Xuegang; He Jiawen


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

  15. Photo-, sono-, and sonophotocatalytic activity of metal oxide nanocomposites TiO2/CeO2 for degradation of dye

    Tju, H.; Muzakki, A. T.; Taufik, A.; Saleh, R.


    In present study, TiO2 nanoparticles was modified by the addition of CeO2 to increase efficiency and improve catalytic activity under visible light, ultrasonic irradiation, and combination of both irradiation. The as-prepared CeO2 nanoparticles have been incorporated to mixture of TiO2 with various molar ratio (x)TiO2:(1-x)CeO2 = 0.25:0.75 ; 0.5:0.5 and 0.75:0.25). Then the pristine TiO2, CeO2 and TiO2/CeO2 nanocomposites were identified by X-ray Diffraction (XRD) and the surface area was measured using Brunner-Emett teller (BET) measurement. The XRD results indicated that the CeO2 was a face centered cubic structure and the TiO2 was anatas structures. The as-prepared samples exhibit a good catalytic for the decolorization of methylene blue (MB) under visible light, ultrasonic irradiation, and combination of visible light and ultrasonic irradiation. The enhanced performance might be due to the lower recombination of charge carriers and surface properties of TiO2/CeO2. To further studies the catalytic mechanism the scavenger and initial solution experiment were also tested. Moreover, TiO2/CeO2 nanocomposites shows good cycle stability toward continuous four cycles runs of catalytic experiment for the degradation of MB.

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

    Sumittra Charojrochkul


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

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


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

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

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


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

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

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


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

  20. 纳米CeO2悬浮液的流变性能研究%Study on Rheological Behavior of Nanosized CeO2 Suspension

    郑国琴; 沈志刚; 曾晓飞; 陈建峰


    The theological behavior of polishing slurry plays an important role in the chemical mechanical polishing. In this research, the rheology property of nano-ceria slurry is investigated. The effects of pH, particle concentration, temperature and electrolyte concentration are discussed. It is shown that a lower zeta potential gives rise to a higher apparent viscosity and results in the observed shear thinning property. In the suspension if the particle concentration is below 17.4wt% ,the nano-ceria slurry exhibits Newtonian behavior and further addition of CeO2, higher apparent viscosity and shear-thinning behavior is observed. The influence of temperature on rheology property of CeO2 slurry appears more complex. When the temperature is lower than 35℃ , the apparent viscosity of the CeO2 slurry decreases with temperature increases. But when the temperature is higher than 35 ℃, increasing temperature results in the apparent viscosity increasing. If the electrolyte is added into the slurry,a shift of apparent viscosity to a higher value is observed due to the decreased zeta potential.%在化学机械抛光过程中,抛光液的流变性能起到至关重要的作用.本文利用Haake流变仪研究了水基纳米CeO2悬浮液在不同pH值、CeO2颗粒浓度、温度、中性电解质浓度下的流变性能.研究结果表明,随着zeta电位减小,悬浮液表观粘度增大,体系逐渐转变为剪切变稀的非牛顿流体.悬浮液中CeO2颗粒浓度低于17.4wt%时,颗粒浓度对体系的流变性能影响较弱,体系为牛顿流体,但是继续增大颗粒浓度,悬浮体表观粘度明显增大,出现剪稀现象.温度对悬浮液流变性能影响较为复杂,当温度小于35℃时,随着温度的升高体系表观粘度变小,温度大于35℃时,温度的升高反而使体系表观粘度增高.中性电解质的加入使得悬浮体的zeta电位降低,从而使体系表现出较高的表观粘度.

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

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


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

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

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


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

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

    李霞章; 陈丰; 陆晓旺; 倪超英; 陈志刚


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

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

    Farooq, Muhammad; Ramli, Anita; Subbarao, Duvvuri


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

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

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


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

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

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


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

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

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


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

  8. High-temperature ferromagnetism in Co-doped CeO2 synthesized by the coprecipitation technique.

    Colis, S; Bouaine, A; Schmerber, G; Ulhaq-Bouillet, C; Dinia, A; Choua, S; Turek, P


    The aim of the present study is to check the influence of annealing under vacuum and a mixture of N(2)-H(2) atmosphere on the magnetic properties of polycrystalline Co-doped CeO(2) diluted magnetic oxides (DMOs) with Co concentrations of 5 at% synthesized using the coprecipitation technique. X-Ray diffraction (XRD) patterns and transmission electron microscopy (TEM) showed for all samples the expected CeO(2) cubic fluorite-type structure and that Co ions are uniformly distributed inside the samples. Room-temperature Raman and photoluminescence (PL) spectroscopies indicate an increase in the concentration of oxygen vacancies upon Co doping and further annealing. Field dependent magnetization measurements revealed a paramagnetic behavior for as-prepared Co-doped CeO(2), while a ferromagnetic behavior appears when the same samples are annealed under vacuum or N(2)-H(2) atmosphere. Temperature dependent magnetization measurements suggest that the observed ferromagnetism is due to the presence of metallic Co clusters with nanometric size and broad size distribution. These results are supported by electron paramagnetic resonance studies.

  9. Au/TiO2-CeO2 Catalysts for Photocatalytic Water Splitting and VOCs Oxidation Reactions

    Roberto Fiorenza


    Full Text Available Photocatalytic water splitting for H2 production and photocatalytic oxidation of 2-propanol, an example of volatile organic compounds, were investigated over TiO2 catalysts loaded with gold and/or ceria. In the water splitting reaction the presence of gold only slightly affected the performance of TiO2 whereas the presence of CeO2 had a more remarkable positive effect. In the 2-propanol oxidation Au/TiO2 was the most active sample in terms of alcohol conversion whereas Au/TiO2-CeO2 exhibited the highest CO2 yield. On the basis of characterization experiments (X-Ray Diffraction (XRD, Energy Dispersive X-ray Analysis EDX, surface area measurements, Diffuse Reflectance Spectroscopy (DRS and Raman spectroscopy, it was suggested that the interaction of Au with TiO2 causes an increase in the charge separation between the photo-excited electron/hole pairs, leading to an enhanced photocatalytic activity (to acetone over Au/TiO2 and to CO2 over Au/TiO2-CeO2, whereas the presence of ceria, acting as a hole trap, positively mainly affects the formation of hydrogen by water splitting.

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



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

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


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

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

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


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

  13. Structural Modification of Sol-Gel Synthesized V2O5 and TiO2 Thin Films with/without Erbium Doping

    Fatma Pınar Gökdemir; Ayşe Evrim Saatci; Orhan Özdemir; Kubilay Kutlu


    Comparative work of with/without erbium- (Er-) doped vanadium pentoxide (V2O5) and titanium dioxide (TiO2) thin films were carried out via sol-gel technique by dissolving erbium (III) nitrate pentahydrate (Er(NO3)3·5H2O) in vanadium (V) oxoisopropoxide (OV[OCH(CH3)2]3) and titanium (IV) isopropoxide (Ti[OCH(CH3)2]4). Effect of Er doping was traced by Fourier transform IR (FTIR), thermogravimetric/differential thermal (TG/DTA), and photoluminescence measurements. UV-Vis transmission/absorption...

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

    Yongjun He; Blun Yang; Haimin Pan; Guozhi Li


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

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

    张辉; 邹勇; 邹增大; 史传伟


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

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

    Lv, Zijian; Zhong, Qin; Ou, Man


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

  17. Sonocatalytic and sonophotocatalytic activity of ternary Fe3O4/CeO2/ZnO for waste water removal

    Harno, F. F.; Taufik, A.; Saleh, R.


    In this study, CeO2 nanoparticles were modified by Fe3O4 and ZnO to enhance their sono- and sonophotocatalytic activity for degrading Methylene Blue dye pollutant. The molar ratio between Fe3O4, CeO2, and ZnO was 0.05:1:1, 0.1:1:1, 0.3:1:1, 0.5:1:1. The ternary Fe3O4/CeO2/ZnO nanocomposites with various molar ratios were fabricated by the sol-gel method. The structure of ternary Fe3O4/CeO2/ZnO nanocomposites was investigated by XRD Diffraction, while the surface area was investigated by Brunauer-Emmett-Teller (BET). The conditions such as the molar ratio, catalyst dosage, and scavengers were investigated to see the degradation of Methylene Blue under ultrasonic and combination of ultrasonic and ultraviolet irradiations, simultaneously.

  18. Crystal growth and scintillation properties of Er-doped Lu{sub 3}Al{sub 5}O{sub 12} single crystals

    Sugiyama, Makoto, E-mail: [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Fujimoto, Yutaka [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yanagida, Takayuki [New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan); Totsuka, Daisuke [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Nihon Kessho Kogaku Co. Ltd., 810-5 Nobe-cho Tatebayashi Gunma (Japan); Kurosawa, Shunsuke; Futami, Yoshisuke; Yokota, Yuui; Chani, Valery [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); Yoshikawa, Akira [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan); New Industry Creation Hatchery Center (NICHe), Tohoku University, 6-6-10 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8579 (Japan)


    Er-doped Lu{sub 3}Al{sub 5}O{sub 12} (Er:LuAG) single crystalline scintillators with different Er concentrations of 0.1, 0.5, 1, and 3% were grown by the micro-pulling-down ({mu}-PD) method. The grown crystals were composed of single-phase material, as demonstrated by powder X-ray diffraction (XRD). The radioluminescence spectra measured under {sup 241}Am {alpha}-ray excitation indicated host emission at approximately 350 nm and Er{sup 3+} 4f-4f emissions. According to the pulse height spectra recorded under {gamma}-ray irradiation, the 0.5% Er:LuAG exhibited the highest peak channel among the samples. The {gamma}-ray excited decay time profiles were well fitted by the two-component exponential approximation (0.8 {mu}s and 6-10 {mu}s).

  19. Degradation of optical properties of a film-type single-wall carbon nanotubes saturable absorber (SWNT-SA) with an Er-doped all-fiber laser.

    Ryu, Sung Yoon; Kim, Kyung-Soo; Kim, Jungwon; Kim, Soohyun


    Single-wall carbon nanotubes (SWNTs) are promising materials for saturable absorbers (SAs) in mode-locked lasers. However it has been widely recognized that the degradation of optical properties of film-type SWNTs used in femtosecond mode-locked lasers limits the achievable long-term stability of such lasers. In this paper, we study the degradation of optical properties of SWNT-SA fabricated as sandwich type using HiPCO SWNTs with an Er-doped all-fiber laser. The thresholds of laser pump power are examined to avoid the damage of the SWNT-SA. Based on the proposed analysis, it is shown that all-fiber laser pulses of 300 fs pulse width, 3.85 mW average output power, 211.7 MW/cm² peak intensity and 69.9 MHz repetition rate can be reliably generated without any significant damage to the SWNT-SA film.

  20. Frequency stabilization of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer

    Hitachi, K., E-mail:; Ishizawa, A.; Mashiko, H.; Sogawa, T.; Gotoh, H. [NTT Basic Research Laboratories, NTT Corporation, Atsugi-shi, Kanagawa 243-0198 (Japan); Tadanaga, O. [NTT Device Technology Laboratories, NTT Corporation, Atsugi-shi, Kanagawa 243-0198 (Japan); Nishikawa, T. [Tokyo Denki University, 5 Senju-Asahi-cho, Adachi-ku, Tokyo 120-8551 (Japan)


    We report the stabilization of the carrier-envelope offset (CEO) frequency of an Er-doped fiber laser with a collinear 2f-to-3f self-referencing interferometer. The interferometer is implemented by a dual-pitch periodically poled lithium niobate ridge waveguide with two different quasi-phase matching pitch sizes. We obtain a 52-dB signal-to-noise ratio in the 100-kHz resolution bandwidth of a heterodyne beat signal, which is sufficient for frequency stabilization. We also demonstrate that the collinear geometry is robust against environmental perturbation by comparing in-loop and out-of-loop Allan deviations when the in-loop CEO frequency is stabilized with a phase-locked loop circuit.

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

    乔东升; 卢冠忠; 郭耘; 王艳芹; 郭杨龙


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

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

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


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

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

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


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

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

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


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

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

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


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

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

    Heydari, Hamid; Gholivand, Mohammad Bagher


    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.

  7. Incineration of a Commercial Coating with Nano CeO2

    Le Bihan, Olivier; Ounoughene, Ghania; Meunier, Laurent; Debray, Bruno; Aguerre-Chariol, Olivier


    The potential environmental risk arising from the incineration of waste containing nanomaterials is a new field which deserves further attention. Some recent studies have begun to focus on this topic but the data are incomplete. In addition, there is a need to consider real life waste. The present study gives some insight into the fate and behavior of a commercial coating containing a commercial additive (7% w/w) based on nano-CeO2 (aggregates of 10 to 40 nm, with elemental particles of 2-3 nm). The tests have been conducted with a system developed in the frame of the NanoFlueGas project. The test protocol was designed to respect the regulatory criteria of a good combustion in incineration plants (temperature around 850°C, highly ventilated combustion, at least 2 s residence time for the combustion gas in a post-combustion chamber at 850°C, and high oxygen/fuel contact). Time tracking by electric low pressure impaction (ELPI) shows that the incineration produces aerosol with number concentration dominated by sub-100 nm particles. Cerium is observed by TEM and EDS analysis but as a minor compound of a sub-group of particles. No nanoCeO2 particles have been observed in the aerosol. ICP-MS analysis indicates that the residual material consists mainly of CeO2 (60% of the mass). Observation by TEM establishes that this material is in the form of aggregates with individual particle of 40-200 nm and suggests that sintering occurred during incineration. As a conclusion, the lab scale incineration study led mainly to the release of nano-CeO2 in the residual material, as the major component. Its size distribution is different than the one of the nano-CeO2 observed in the initial sample before incineration. Additional research is needed to improve the understanding of nanoCeO2 behavior, and to integrate experiments at lab and real scale.

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

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


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

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

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


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

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

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


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

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

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


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

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


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

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

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


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

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

    Alexandra Kroll

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

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

    林英光; 皮丕辉; 郑大锋; 杨卓如; 王炼石


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

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

    李酽; 刘秀琳; 栗建钢


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

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

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


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

  6. High pressure behavior of nano-crystalline CeO2 up to 35 GPa: a Raman investigation

    Dogra, Sugandha; Dilawar Sharma, Nita; Singh, Jasveer; Poswal, Himanshu Kumar; Sharma, S. M.; Bandyopadhyay, A. K.


    The present paper reports the results of in situ Raman studies carried out on nano-crystalline CeO2 up to a pressure of 35 GPa at room temperature. The material was characterized at ambient conditions using X-ray diffraction and Raman spectroscopy and was found to have a cubic structure. We observed the Raman peak at ambient at 465 cm-1, which is characteristic of the cubic structure of the material. The sample was pressurized using a diamond anvil cell using ruby fluorescence as the pressure monitor, and the phase evolution was tracked by Raman spectroscopy. With an increase in the applied pressure, the cubic band was seen to steadily shift to higher wavenumbers. However, we observed the appearance of a number of new peaks around a pressure of about 34.7 GPa. CeO2 was found to undergo a phase transition to an orthorhombic α -PbCl2-type structure at this pressure. With the release of the applied pressure, the observed peaks steadily shift to lower wavenumbers. On decompression, the high pressure phase existed down to a total release of pressure.

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

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


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

  8. Laser clad Ni-base alloy added nano- and micron-size CeO 2 composites

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


    Micron-size Ni-base alloy (NBA) powders are mixed with both 1.5 wt% (%) micron-CeO 2 (m-CeO 2) and also 1.0-3.0% nano-CeO 2 (n-CeO 2) powders. These mixtures are coated on low carbon steel (Q235) by 2.0 kW CO 2 laser cladding. The effects on microstructures, microhardness and wear resistance of the coating by the addition of m- and n-CeO 2 powders to NBA (m- and n-CeO 2/NBA) have been investigated. Addition to the primary phases of γ-Ni, Cr 23C 6 and Ni 3B of NBA coating, CeNi 3 shows up both in m- and n-CeO 2/NBA coatings and CeNi 5 appears only in n-CeO 2/NBA coating. Directional dendrite and coarse equiaxed dendrite are grown in m-CeO 2/NBA coating from interface to central zone, whereas multi-oriented dendrite and fine equiaxed dendrite growth by addition of n-CeO 2. The microhardness and wear resistance of coatings are greatly improved by CeO 2 powder addition, and compared to the addition of 1.0% and 3.0%, 1.5% n-CeO 2/NBA is the best. Hardness and wear resistance of the coating improves with decreasing CeO 2 size from micron to nano.

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

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


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

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

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


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

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

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


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

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

    刘雪松; 吴晓东; 翁端; 石磊


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

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

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


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

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

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


    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.

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

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


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

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

    R. M. Mohamed


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

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

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


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

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

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


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

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

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


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

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

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


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

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

    Majid Farahmandjou


    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.

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

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


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

  3. Effect of the AlPO4 join on the pump-to-signal conversion efficiency in heavily Er-doped fibers.

    Likhachev, Mikhail E; Bubnov, Mikhail M; Zotov, Kirill V; Lipatov, Denis S; Yashkov, Mikhail V; Guryanov, Aleksei N


    Heavily Er-doped fibers (EDFs) based on P(2)O(5)-Al(2)O(3)-SiO(2) (PAS) ternary glass have been studied. A unique feature of this glass is the formation of a AlPO(4) join having a structure similar to that of SiO(2) glass and a refractive index below it. It is found that the Er(3+) absorption and emission spectra in the PAS EDFs are defined by the dopant (Al(2)O(3) or P(2)O(5)) present in excess and are close to those of the corresponding binary glass (Al(2)O(3)-SiO(2) or P(2)O(5)-SiO(2)). The presence of the AlPO(4) join results in the enhancement of the pump-to-signal conversion efficiency in the PAS EDFs as compared with the EDFs based on the P(2)O(5)-SiO(2) and Al(2)O(3)-SiO(2) (with 1.5 mol. %Al(2)O(3) and less) binary glasses. The PAS host glass is advantageous in the case of large-mode-area active fibers.

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

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


    The decomposition of methane on Ni/α-Al2O3 modified by La2O3 and CeO2 with different contents has been investigated and the ralationship between methane decomposition and removal of carbon by CO2 over these catalyst has also been studied by pulse-chromatography. The catalysts were characterized by TPR and XRD. It was shown that Ni/α-Al2O3 could be promoted by adding La2O3, and the carbon species produced over this catalyst was activated and eliminated by CO2. But CeO2 would suppress the decomposition of methane over Ni crystallite. Both La2O3 and CeO2 can inhibit aggregation of the Ni particles. Decomposition of methane over the Ni-based catalysts is structure sensitive to a certain extent.

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

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


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

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

    WEI Yan; LI Mao-Guo; FANG Bin


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

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

    Somekawa, Shouichi


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

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

    Li, Jing


    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.

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

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


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

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

    Ma, Lin; Tian, Hui; Yue, Zhao


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

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

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


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

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

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


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

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

    Xiulan Cai; Yuanxing Cai; Weiming Lin


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

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

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


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

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

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


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

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


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

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

    D Naga Durgasri; T Vinodkumar; Benjaram M Reddy


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

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

    Marija Prekajski


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

  19. Voltage tunable dielectric properties of oxides at nanoscale: TiO2 and CeO2 as model systems

    Prakash, T.; Tamil Selvan, A.; Suraiya Begum, S. N.


    Carrier transport through electrically active grain boundaries has been studied under biased condition using Solartron 1260 impedance/gain phase analyzer with an applied AC potential of 250 mV in the frequency range 1 Hz-1 MHz for nanocrystalline TiO2 and CeO2 as the model systems. Prior to the measurement both the materials were converted into cylindrical pellets with (8 mm diameter and 1 mm thick) by applying uni-axial pressure of 4 ton using a hydraulic press, then sintered at 300, 450 and 600 °C for 30 min for TiO2 sample and for the case of CeO2 it was done at 300, 600 and 900 °C for 30 min. Further, they were characterized using powder X-ray diffractometer (XRD) and transmission electron microscopy (TEM) to know the crystal structure, average crystallite size and morphology. The impedance measurements were performed at room temperature under applied DC bias voltages from 0 to 3 V in the periodic increment of 0.2 V. The observed applied bias voltage effect on dielectric constant of both the systems was analyzed with 'grain boundary double Schottky potential barrier height model' for different grain sizes. The percentage of voltage tunable dielectric constant (T%) as a function of frequency was estimated for all the grain sizes and it was found to be increase with reduction of grain size. Our experimental findings reveal the possibilities of utilizing these nanocrystals as a potential active material for phased array antenna since both the samples exhibits T% = 85% at 100 Hz frequency.

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

    塔娜; 张密林; 李娟; 李华举; 李勇; 申文杰


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

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

    崔华楠; 李登; 刘冠涛; 梁振兴; 石建英


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

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

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


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

  3. Dissolved cerium contributes to uptake of Ce in the presence of differently sized CeO2-nanoparticles by three crop plants.

    Schwabe, Franziska; Tanner, Simon; Schulin, Rainer; Rotzetter, Aline; Stark, Wendelin; von Quadt, Albrecht; Nowack, Bernd


    We investigated the uptake of cerium (Ce) dioxide nanoparticles (NPs) by hydroponically grown wheat, pumpkin and sunflower plants. The presence of plant roots in nutrient solution led to a substantial increase in the dissolution of CeO2-NP compared to plant-free medium. Experiments with Zr/CeOx-NP revealed that Ce was not only taken up in the form of NPs, but simultaneously to a significant degree also as dissolved Ce(iii) ions, which then re-precipitated in the form of CeO2-NPs inside the leaves. The contribution of dissolved Ce uptake was particularly large for particles smaller than 10 nm due to their higher dissolution rate. Our data also indicate that the translocation of Ce resulting from NP-root-exposure is species dependent. When Ce was supplied as dissolved ions, sunflower had the highest capacity of Ce-ion accumulation inside the leaves, while there was no significant difference between pumpkin and wheat. We found no Ce translocation from roots into shoots when only NPs bigger than 20 nm were applied. This study highlights that plant root activity can have a significant impact on the dissolution of CeO2-NPs in soil solution and that uptake of dissolved Ce(iii) followed by re-precipitation needs to be considered as an important pathway in studies of CeO2-NP uptake by plants.

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

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


    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.

  5. Facile Synthesis of CeO2-LaFeO3 Perovskite Composite and Its Application for 4-(Methylnitrosamino-1-(3-Pyridyl-1-Butanone (NNK Degradation

    Kaixuan Wang


    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.

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

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


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

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

    Omar, Shobit; Bonanos, Nikolaos


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

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

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


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

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

    Abdelkader Elaziouti


    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.

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

    Stroosnijder, M.F.; Guttmann, V.; Fransen, T.; Wit, de J.H.W.


    The corrosion behavior of a wrought austenitic Fe-20Cr-32Ni steel, Alloy 800H, was studied in a simulated coal-gasification atmosphere at 700°C for exposure times up to 2500 hr. The influence of preoxidation and CeO2-surface application followed by preoxidation on the corrosion resistance of this ma

  11. Germination and early plant development of 10 plant species exposed to Nano TiO2 and CeO2

    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 ...

  12. Pressure Regulations on the Surface Properties of CeO2 Nanorods and Their Catalytic Activity for CO Oxidation and Nitrile Hydrolysis Reactions.

    Li, Jing; Zhang, Zhiyun; Gao, Wei; Zhang, Sai; Ma, Yuanyuan; Qu, Yongquan


    Surface properties of nanoscale CeO2 catalysts in terms of the surface Ce(3+) fraction and concentration of oxygen vacancy can affect their catalytic performance significantly. Continual adjustment on surface properties of CeO2 with the morphological preservation has not been realized by synthetic methods. The revisited studies show that surface properties of CeO2 nanorods can be effectively regulated by synthetic pressures while the rodlike morphology is well-preserved. Such phenomena are ascribed to the contact possibility between Ce(3+) species and dissolved O2, which is balanced by the rapidly increased and gradually saturated dissolution/recrystallization rate of Ce(OH)3 and linearly increased concentration of dissolved O2 with the increase of total air pressure or partial pressure of O2. Surface-property-dependent catalytic activity of CeO2 nanorods synthesized under various pressures was also demonstrated in two benchmark reactions-catalytic oxidation of CO and hydrolysis of nitrile. Such a finding of the pressure regulation on the reducible metal oxides provides an effective approach to rationally design novel catalysts for specific reactions, where ceria are supports, promoters, or actives.

  13. Differential genomic effects on canonical signaling pathways by two different CeO2 nanoparticles in HepG2 cells

    Differential genomic effects on signaling pathways by two different CeO2 nanoparticles in HepG2 cells. Sheau-Fung Thai1, Kathleen A. Wallace1, Carlton P. Jones1, Hongzu Ren2, Benjamin T. Castellon1, James Crooks2, Kirk T. Kitchin1. 1Integrated Systems Toxicology Divison, 2Resea...

  14. Origin of enhanced visible-light photocatalytic activity of transition-metal (Fe, Cr and Co)-doped CeO2: effect of 3 d orbital splitting

    Yang, Ke; Li, Dong-Feng; Huang, Wei-Qing; Xu, Liang; Huang, Gui-Fang; Wen, Shuangchun


    Enhanced visible-light photocatalytic activity of transition-metal-doped ceria (CeO2) nanomaterials has experimentally been demonstrated, whereas there are very few reports mentioning the mechanism of this behavior. Here, we use first-principles calculations to explore the origin of enhanced photocatalytic performance of CeO2 doped with transition metal impurities (Fe, Cr and Co). When a transition metal atom substitutes a Ce atom into CeO2, t 2g and e g levels of 3 d orbits appear in the middle of band gap owing to the effect of cubic ligand field, and the former is higher than latter. Interestingly, t 2g subset of FeCe (CoCe and CrCe)-Vo-CeO2 splits into two parts: one merges into the conduction band, the other as well as e g will remain in the gap, because O vacancy defect adjacent to transition metal atom will break the symmetry of cubic ligand field. These e g and t 2g levels in the band gap are beneficial for absorbing visible-light and enhancing quantum efficiency because of forbidden transition, which is one key factor for enhanced visible-light photocatalytic activity. The band gap narrowing also leads to a redshift of optical absorbance and high photoactivity. These findings can rationalize the available experimental results and provide some new insights for designing CeO2-based photocatalysts with high photocatalytic performance.

  15. Controlled synthesis of CeO2 microstructures from 1D rod-like to 3D lotus-like and their morphology-dependent properties

    Gong, Jinfeng; Meng, Fanming; Fan, Zhenghua; Li, Huijie


    Monodisperse 3D lotus-like CeO2 microstructures have been successfully synthesized via controlling the morphology of CeCO3OH precursors under hydrothermal condition as well as subsequent calcination. The reaction time was systematically investigated. XRD, FT-IR, SEM, TEM, XPS, Raman scattering and Photoluminescence (PL) spectra were employed to characterize the samples. The lotus-like CeO2 hierarchical structures with an average of 4-6 μm are composed of many nanoplates of 100-200 nm in thickness as the petals stacking together to form open flowers and have a fluorite cubic structure. Based on the time-dependent morphology evolution evidences, a nucleation-dissolution-recrystallization mechanism has been proposed to explain the transformation from rod-like structures to lotus-like CeO2 hierarchical structures with the increase of reaction time. It is found that there are Ce3+ ions and oxygen vacancies in surface of samples. The magnetic and photoluminescence measurements indicated that all CeO2 samples exhibit excellent ferromagnetism and optical properties at room temperature, and while increasing the reaction time, the ferromagnetism and optical properties increase more, which can be reasonably explained for the influences of the different morphology of the particles and the concentration of oxygen vacancies and Ce3+ ions. [Figure not available: see fulltext.

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

    Oriekhova, Olena; Stoll, Serge


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

  17. WO3/CeO2/TiO2 Catalysts for Selective Catalytic Reduction of NO(x) by NH3: Effect of the Synthesis Method.

    Michalow-Mauke, Katarzyna A; Lu, Ye; Ferri, Davide; Graule, Thomas; Kowalski, Kazimierz; Elsener, Martin; Kröcher, Oliver


    WO3/CeO2/TiO2, CeO2/TiO2 and WO3/TiO2 catalysts were prepared by wet impregnation. CeO2/TiO2 and WO3/TiO2 showed activity towards the selective catalytic reduction (SCR) of NO(x) by NH3, which was significantly improved by subsequent impregnation of CeO/TiO2 with WO3. Catalytic performance, NH3 oxidation and NH3 temperature programmed desorption of wet-impregnated WO3/CeO2/TiO2 were compared to those of a flame-made counterpart. The flame-made catalyst exhibits a peculiar arrangement of W-Ce-Ti-oxides that makes it very active for NH3-SCR. Catalysts prepared by wet impregnation with the aim to mimic the structure of the flame-made catalyst were not able to fully reproduce its activity. The differences in the catalytic performance between the investigated catalysts were related to their structural properties and the different interaction of the catalyst components.

  18. Differential genomic effects on canonical signaling pathways by two different CeO2 nanoparticles in HepG2 cells

    Differential genomic effects on signaling pathways by two different CeO2 nanoparticles in HepG2 cells. Sheau-Fung Thai1, Kathleen A. Wallace1, Carlton P. Jones1, Hongzu Ren2, Benjamin T. Castellon1, James Crooks2, Kirk T. Kitchin1. 1Integrated Systems Toxicology Divison, 2Resea...

  19. Influence of calcination temperature on selective catalytic reduction of NOx with NH3 over CeO2-ZrO2-WO3 catalyst

    李军燕; 宋忠贤; 宁平; 张秋林; 刘昕; 李昊; 黄真真


    A series of CeO2-ZrO2-WO3 catalysts for the selective catalytic reduction (SCR) of NO with NH3 were prepared by hydro-thermal method. The influence of calcination temperature on the catalytic activity, microstructure, surface acidity and redox behavior of CeO2-ZrO2-WO3 catalyst was investigated using various characterization methods. It was found that the CeO2-ZrO2-WO3 catalyst calcined at 600 ºC showed the best catalytic performance and excellent N2 selectivity, and yielded more than 90% NO conversion in a wide temperature range of 250–500 ºC with a space velocity (GHSV) of 60000 h–1. As the calcination temperature was increased from 400 to 600 ºC, the NO conversion obviously increased, but decreased at higher calcination temperature. The results implied that the higher surface area, the strongest synergistic interaction, the superior redox property and the highly dispersed or amorphous WO3 species contributed to the excellent SCR activity of the CeO2-ZrO2-WO3 catalyst calcined at 600 ºC.

  20. Influence of CeO2 doping amount on property of BCTZ lead-free piezoelectric ceramics sintered at low temperature

    黄新友; 邢仁克; 高春华; 陈志刚


    Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) lead-free piezoelectric ceramics co-doped with CeO2 (x=0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%) and Li2CO3 (0.6 wt.%) were prepared by conventional solid-state reaction method. Influence of CeO2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and other ana-lytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO2 de-creased greatly when Li2CO3 doping amount was 0.6 wt.%;a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li2CO3 and CeO2 and sintered at 1050 °C could also be obtained. The piezoelectric constant (d33), the relative permit-tivity (εr) and the planar electromechanical coupling factor (kp) of BCTZ ceramics doped with Li2CO3 increased firstly and then de-creased, the dielectric loss (tanδ) decreased firstly and then increased and decreased at last when CeO2 doping amount increased. The influence of CeO2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li2CO3 were caused by“soft effect”and “hard effect”piezoelectric additive and causing lattice distortion. When CeO2 doping amount (x) was 0.2 wt.%, the BCTZ ce-ramics doped with Li2CO3 (0.6 wt.%) and sintered at 1050 °C possessed the best piezoelectric property and dielectric property with d33 of 436 pC/N, kp of 48.3%,εr of 3650, tanδof 1.5%.

  1. Colloidal stability of CeO2 nanoparticles coated with either natural organic matter or organic polymers under various hydrochemical conditions

    Dippon, Urs; Pabst, Silke; Klitzke, Sondra


    The worldwide marked for engineered nanoparticles (ENPs) is growing and concerns on the environmental fate- and toxicity of ENPs are rising. Understanding the transport of ENPs within and between environmental compartments such as surface water and groundwater is crucial for exposition modeling, risk assessment and ultimately the protection of drinking water resources. The transport of ENPs is strongly influenced by the surface properties and aggregation behavior of the particles, which is strongly controlled by synthetic and natural organic coatings. Both, surface properties and aggregation characteristics are also key properties for the industrial application of ENPs, which leads to the development and commercialization of an increasing number of surface-functionalized ENPs. These include metals and oxides such as Cerium dioxide (CeO2) with various organic coatings. Therefore, we investigate CeO2 ENPs with different surface coatings such as weakly anionic polyvinyl alcohol (PVA) or strongly anionic poly acrylic acid (PAA) with respect to their colloidal stability in aqueous matrix under various hydrochemical conditions (pH, ionic strength) and their transport behavior in sand filter columns. Furthermore, we investigate the interaction of naturally occurring organic matter (NOM) with CeO2 ENPs and its effect on surface charge (zeta potential), colloidal stability and transport. While uncoated CeO2 ENPs aggregate at pH > 4 in aqueous matrix, our results show that PAA and PVA surface coatings as well as NOM sorbed to CeO2-NP surfaces can stabilize CeO2 ENPs under neutral and alkaline pH conditions in 1 mM KCl solution. Under slightly acidic conditions, differences between the three particle types were observed. PVA can stabilize particle suspensions in presence of 1 mM KCl at pH > 4.3, PAA at pH >4.0 and NOM at >3.2. While the presence of KCl did not influence particle size of NOM-CeO2 ENPs, CaCl2 at >2 mM lead to aggregation. Further results on the influence of KCl and CaCl2 on aggregation of coated CeO2 ENPs and transport in sand filter columns will be presented.

  2. Modification of LiCo1/3Ni1/3Mn1/3O2 cathode material by CeO2-coating


    LiCo1/3Ni1/3Mn1/3O2 was coated by a layer of 1.0 wt% CeO2 via sol-gel method. The bared and coated LiMn1/3Co1/3Ni1/3O2 was characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),cyclic voltammogram (CV) and galvanotactic charge-discharge test. The results show that the coating layer has no effect on the crystal structure,only coating on the surface; the 1.0 wt% CeO2-coated LiCo1/3Ni1/3Mn1/3O2 exhibits better discharge capacity and cycling performance than the bared LiCo1/3Ni1/3Mn1/3O2. The discharge capacity of 1.0 wt% CeO2-coated cathode is 182.5 mAh.g-1 at a current density of 20 mA.g-1,in contrast to 165.8 mAh.g-1of the bared sample. The discharge capacity retention of 1.0 wt% CeO2-coated sample after 12 cycles reaches 93.2%,in comparison with 86.6% of the bared sample. CV results show that the CeO2 coating could suppress phase transitions and prevent the surface of cathode material from direct contact with the electrolyte,thus enhance the electro-chemical performance of the coated material.

  3. Chloride salt of conducting polyaniline synthesized in the presence of CeO2: Structural analysis of the core-shell nanocomposite

    da Silva, J. S. M.; de Souza, S. M.; Trovati, G.; Sanches, E. A.


    Chloride salt of conducting Polyaniline (ES-PANI) was synthesized in the presence of cerium dioxide (CeO2) for structural and morphological evaluation of the resulting core-shell nanocomposite. X-ray Diffraction (XRD), estimative of crystallinity percentage, Le Bail Method, Scanning Electron Microscopy (SEM) and DC electrical conductivity were used for materials characterization. The resulting nanocomposite was constituted of three phases as identified by X-Ray Diffraction: ES-PANI, CeO2 and CeCl3(H2O)7, chloride hepta-hydrate cerium. Crystallinity of ES-PANI and nanocomposite were estimated around 40 and 85%, respectively. XRD patterns were also used to perform the Le Bail Method. This refinement allowed structural characterization of each phase, obtainment of cell parameters and crystallite size and shape. For ES-PANI and CeCl3(H2O)7, crystallites showed a prolate-like shape with an average size of 21 Å and 104 Å, respectively. CeO2 crystallites presented much larger size, as expected, with isotropic average size of 490 Å. SEM images showed that the nanocomposite has a core-shell morphology with both ES-PANI nanofibers and CeCl3(H2O)7 particles coating the CeO2 particles. The polymerization of ES-PANI over the CeO2 particles in order to form the nanocomposite affected the natural chain alignment of the polymer, resulting in better molecular rearrangement and larger crystallites. Finally, measurements of DC electrical conductivity of ES-PANI and nanocomposite have showed values of 1.11 × 10-4 and 2.22 × 10-4 S/cm, respectively. Nanocomposite has showed electrical conductivity 50 times greater than the pure ES-PANI. Thus, in this work we have reported a systematic structural and morphological investigation of PANI/CeO2/CeCl3(H2O)7 core-shell nanocomposite.

  4. No genotoxicity in rat blood cells upon 3- or 6-month inhalation exposure to CeO2 or BaSO4 nanomaterials.

    Cordelli, Eugenia; Keller, Jana; Eleuteri, Patrizia; Villani, Paola; Ma-Hock, Lan; Schulz, Markus; Landsiedel, Robert; Pacchierotti, Francesca


    In the course of a 2-year combined chronic toxicity-carcinogenicity study performed according to Organisation for Economic Co-operation and Development (OECD) Test Guideline 453, systemic (blood cell) genotoxicity of two OECD representative nanomaterials, CeO2 NM-212 and BaSO4 upon 3- or 6-month inhalation exposure to rats was assessed. DNA effects were analysed in leukocytes using the alkaline Comet assay, gene mutations and chromosome aberrations were measured in erythrocytes using the flow cytometric Pig-a gene mutation assay and the micronucleus test (applying both microscopic and flow cytometric evaluation), respectively. Since nano-sized CeO2 elicited lung effects at concentrations of 5mg/m(3) (burdens of 0.5mg/lung) in the preceding range-finding study, whereas nano-sized BaSO4 did not induce any effect, female rats were exposed to aerosol concentrations of 0.1 up to 3mg/m(3) CeO2 or 50mg/m(3) BaSO4 nanomaterials (6h/day; 5 days/week; whole-body exposure). The blood of animals treated with clean air served as negative control, whereas blood samples from rats treated orally with three doses of 20mg/kg body weight ethylnitrosourea at 24h intervals were used as positive controls. As expected, ethylnitrosourea elicited significant genotoxicity in the alkaline Comet and Pig-a gene mutation assays and in the micronucleus test. By contrast, 3- and 6-month CeO2 or BaSO4 nanomaterial inhalation exposure did not elicit significant findings in any of the genotoxicity tests. The results demonstrate that subchronic inhalation exposure to different low doses of CeO2 or to a high dose of BaSO4 nanomaterials does not induce genotoxicity on the rat hematopoietic system at the DNA, gene or chromosome levels.

  5. Macroporous graphene capped Fe3O4 for amplified electrochemiluminescence immunosensing of carcinoembryonic antigen detection based on CeO2@TiO2.

    Yang, Lei; Zhu, Wenjuan; Ren, Xiang; Khan, Malik Saddam; Zhang, Yong; Du, Bin; Wei, Qin


    A novel electrochemiluminescence (ECL) signal-amplified immunosensing strategy was proposed by using gold nanoparticles (Au NPs) functionalized reduced graphene oxide (rGO) capped Fe3O4 (Au-FrGO). In this work, CeO2@TiO2 was prepared by a sol-gel method to wrap CeO2 with TiO2. In the presence of CeO2, CeO2@TiO2 exhibited better ECL activity than TiO2 with peroxydisulfate as coreactant. In addition, FrGO with macroporous structure was synthesized by self-assembly of rGO sheets capped cationic Fe3O4 nanoparticles, exhibiting larger specific surface area than rGO. Due to the low toxicity and magnetism of Fe3O4, FrGO owned more favorable biocompatibility and the application of magnetic-separation simplified the preparation procedure. After hybridizing with Au NPs, FrGO exhibited more excellent electrical conductivity and could immobilize more CeO2@TiO2 and antibodies. Therefore, a novel label-free ECL immunosensor based on Au-FrGO-CeO2@TiO2 was constructed which generated higher ECL response. To investigate the performance of the immunosensor, carcinoembryonic antigen (CEA) was chosen as a model target analyte. Under optimal conditions, the immunosensor had sensitive response to CEA in a wide linear range of 0.01pgmL(-1) to 10ngmL(-1) with a detection limit of 3.28 fg mL(-1). The proposed ECL immunosensor exhibited excellent stability, repeatability and selectivity, which opened another promising avenue for CEA determination in real serum samples.

  6. [Research on SCR denitrification of MnOx/Al2O3 modified by CeO2 and its mechanism at low temperature].

    Guo, Jing; Li, Cai-Ting; Lu, Pei; Cui, Hua-Fei; Peng, Dun-Liang; Wen, Qing-Bo


    The Al2O3,which has large specific surface area and is used as carrier,was prepared by sol-gel method in this study. Series catalysts of MnOx, CeO2 plus MnOx supported on Al2O3 by isometric impregnation method. The SCR denitrification experimental conditions were as follows: NH3 as reductive agent, certain gas velocity and suitable ratio of gas mixed was setup. Furthermore, the experiments of BET, XRD and SEM were also carried out respectively in order to obtain physicochemical properties of the prepared catalysts. The experimental results showed that the loading of active component and calcination temperature made a big difference to the catalysts' performance. With appropriate addition of CeO2, MnOx/Al2O3 exhibits better activity and stability. For MnOx/Al2O3, the catalytic activity on NO was greatly influenced by its loaded content, and 7% MnOx/Al2O3 showed superior catalytic activity among the MnOx/Al2O3. The addition of CeO2 could greatly improve the dispersibility of MnOx on the carrier and increase its catalytic activity. The 4% CeO2 addition was the optimum loaded mass precent. Forthermore, 550 degrees C is the best calcination temperature, as MnOx formed different crystalline phases with temperature, at the same time, the addition of CeO2 could affect MnOx crystalline phase. The catalytic mechanism of SCR on NO was also discussed.

  7. Structural Modification of Sol-Gel Synthesized V2O5 and TiO2 Thin Films with/without Erbium Doping

    Fatma Pınar Gökdemir


    Full Text Available Comparative work of with/without erbium- (Er- doped vanadium pentoxide (V2O5 and titanium dioxide (TiO2 thin films were carried out via sol-gel technique by dissolving erbium (III nitrate pentahydrate (Er(NO33·5H2O in vanadium (V oxoisopropoxide (OV[OCH(CH32]3 and titanium (IV isopropoxide (Ti[OCH(CH32]4. Effect of Er doping was traced by Fourier transform IR (FTIR, thermogravimetric/differential thermal (TG/DTA, and photoluminescence measurements. UV-Vis transmission/absorption measurement indicated a blue shift upon Er doping in V2O5 film due to the softening of V=O bond while appearance of typical absorption peaks in Er-doped TiO2 film. Granule size of the films increased (reduced upon Er substitution on host material compared to undoped V2O5 and TiO2 films, respectively.

  8. Design strategies for P-containing fuels adaptable CeO2-MoO3 catalysts for DeNO(x): significance of phosphorus resistance and N2 selectivity.

    Chang, Huazhen; Jong, Min Tze; Wang, Chizhong; Qu, Ruiyang; Du, Yu; Li, Junhua; Hao, Jiming


    Phosphorus compounds from flue gas have a significant deactivation effect on selective catalytic reduction (SCR) DeNOx catalysts. In this work, the effects of phosphorus over three catalysts (CeO2, CeO2-MoO3, and V2O5-MoO3/TiO2) for NH3-SCR were studied, and characterizations were performed aiming at a better understanding of the behavior and poisoning mechanism of phosphorus over SCR catalysts. The CeO2-MoO3 catalyst showed much better catalytic behavior with respect to resistance to phosphorus and N2 selectivity compared with V2O5-MoO3/TiO2 catalyst. With addition of 1.3 wt % P, the SCR activity of V2O5-MoO3/TiO2 decreased dramatically at low temperature due to the impairment of redox property for NO oxidation; meanwhile, the activity over CeO2 and CeO2-MoO3 catalysts was improved. The superior NO oxidation activity contributes to the activity over P-poisoned CeO2 catalyst. The increased surface area and abundant acidity sites contribute to excellent activity over CeO2-MoO3 catalyst. As the content of P increased to 3.9 wt %, the redox cycle over CeO2 catalyst (2CeO2 ↔ Ce2O3 + O*) was destroyed as phosphate accumulated, leading to the decline of SCR activity; whereas, more than 80% NOx conversion and superior N2 selectivity were obtained over CeO2-MoO3 at T > 300 °C. The effect of phosphorus was correlated with the redox properties of SCR catalyst for NH3 and NO oxidation. A spillover effect that phosphate transfers from Ce to Mo in calcination was proposed.

  9. Influence of nano-structural feature on electrolytic properties in Y2O3 doped CeO2 system

    Toshiyuki Mori, John Drennan, Yarong Wang, Graeme Auchterlonie, Ji-Guang Li and Anya Yago


    Full Text Available Doped ceria (CeO2 compounds are fluorite type oxides which show oxide ionic conductivity higher than yttria stabilized zirconia, in oxidizing atmosphere. As a consequence of this, considerable interest has been shown in application of these materials for 'low temperature operation (500–650 °C' of solid oxide fuel cells (SOFCs. In this study, YxCe1−xO2−δ (x=0.05, 0.1, 0.15, 0.2 and 0.25 fine powders were prepared using a carbonate co-precipitation method. The relationship between electrolytic properties and nano-structural features in the sintered bodies was examined. The micro-structures of Y0.05Ce0.95O1.975, Y0.15Ce0.85O1.925 and Y0.25Ce0.75O1.875 as representative three specimens have been investigated in more detail with transmission electron microscopy (TEM. The big diffuse scattering was observed in the background of electron diffraction pattern recorded from Y0.15Ce0.85O1.925 and Y0.25Ce0.75O1.875 sintered bodies. This means that the coherent micro-domain with ordered structure is in the micro-structure. While Y0.25Ce0.75O1.875 sintered body with low conductivity and high activation energy has big micro-domains, the micro-domain size in Y0.15Ce0.85O1.925 with high conductivity and low activation energy was much smaller than that of Y0.25Ce0.75O1.875. TEM observation gives us message that the size of coherent micro-domain with ordered structure would closely relate to the electrolytic properties such as conductivity and activation energy in the specimens. It was concluded that a control of micro-domain size in nano-scale in Y2O3 doped CeO2 system was a key for development of high quality solid electrolyte in fuel cell application.

  10. 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

    Antoninho Valentini


    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.

  11. Robust Strategy for Crafting Li5Cr7Ti6O25@CeO2 Composites as High-Performance Anode Material for Lithium-Ion Battery.

    Mei, Jie; Yi, Ting-Feng; Li, Xin-Yuan; Zhu, Yan-Rong; Xie, Ying; Zhang, Chao-Feng


    A facile strategy was developed to prepare Li5Cr7Ti6O25@CeO2 composites as a high-performance anode material. X-ray diffraction (XRD) and Rietveld refinement results show that the CeO2 coating does not alter the structure of Li5Cr7Ti6O25 but increases the lattice parameter. Scanning electron microscopy (SEM) indicates that all samples have similar morphologies with a homogeneous particle distribution in the range of 100-500 nm. Energy-dispersive spectroscopy (EDS) mapping and high-resolution transmission electron microscopy (HRTEM) prove that CeO2 layer successfully formed a coating layer on a surface of Li5Cr7Ti6O25 particles and supplied a good conductive connection between the Li5Cr7Ti6O25 particles. The electrochemical characterization reveals that Li5Cr7Ti6O25@CeO2 (3 wt %) electrode shows the highest reversibility of the insertion and deinsertion behavior of Li ion, the smallest electrochemical polarization, the best lithium-ion mobility among all electrodes, and a better electrochemical activity than the pristine one. Therefore, Li5Cr7Ti6O25@CeO2 (3 wt %) electrode indicates the highest delithiation and lithiation capacities at each rate. At 5 C charge-discharge rate, the pristine Li5Cr7Ti6O25 only delivers an initial delithiation capacity of ∼94.7 mAh g(-1), and the delithiation capacity merely achieves 87.4 mAh g(-1) even after 100 cycles. However, Li5Cr7Ti6O25@CeO2 (3 wt %) delivers an initial delithiation capacity of 107.5 mAh·g(-1), and the delithiation capacity also reaches 100.5 mAh g(-1) even after 100 cycles. The cerium dioxide modification is a direct and efficient approach to improve the delithiation and lithiation capacities and cycle property of Li5Cr7Ti6O25 at large current densities.

  12. Effect of Er-doping on the structural and optical properties of Cd{sub 2}V{sub 2}O{sub 7}

    Lozada-Morales, R.; Cid-Garcia, A.; Palomino-Merino, R. [Benemerita Universidad Autonoma de Puebla, Postgrado en Fisica Aplicada, Facultad de Ciencias Fisico-Matematicas, Av. 14, San Claudio, Col. San Manuel, Puebla (Mexico); Lopez-Calzada, G.; Jimenez-Sandoval, S. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Apartado Postal 1-798, Queretaro, Qro. 76001 (Mexico); Zayas, Ma.E. [Departamento de Investigacion en Fisica de la Universidad de Sonora, Edificio 3I, Blvd. Edificio 5 E, Luis Encinas s/n, Col. Centro, 83000 Hermosillo, Sonora (Mexico); Zelaya-Angel, O. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados, P.O. Box 14-740, Mexico D. F. 07360 (Mexico); Carmona-Rodriguez, J. [Instituto Tecnologico Superior de Poza Rica, Calle Luis Donaldo Colosio S/N, Col. Arroyo del Maiz, C.P. 93230, Poza Rica, Veracruz (Mexico); Rubio-Rosas, E. [Centro de Vinculacion Universitaria, Av. 14, San Claudio, Col. San Manuel, Puebla (Mexico); Portillo-Moreno, O. [Facultad de Ciencias Quimicas, Av. 14, San Claudio, Col. San Manuel, Puebla (Mexico)


    The melt-quenching method was used to prepare two groups of samples using CdO and V{sub 2}O{sub 5} as starting materials. Taking into account that a crystalline-amorphous phase transition would be expected for the CdO-V{sub 2}O{sub 5} system, a first batch was prepared varying the proportions of CdO and V{sub 2}O{sub 5} in the intervals 60-95 and 40-5 wt%, respectively. With the aim of investigating the effect of erbium in the phase transition and crystalline quality of the first group of samples, a second batch was fabricated with the same proportions of CdO and V{sub 2}O{sub 5}, with the addition of 5 wt% of Er(NO{sub 3})5H{sub 2}O as source of Er{sup 3+} ions. It was found that crystalline or amorphous samples could be obtained depending on the relative concentrations of CdO and V{sub 2}O{sub 5}, and that the borderline between amorphous and crystalline samples was affected by the incorporation of Er. From X-ray diffraction, it was possible to identify the formation of the ternary compound Cd{sub 2}V{sub 2}O{sub 7} in the crystalline cases. The Raman and infrared bands in these samples were in agreement with the lattice modes of Cd{sub 2}V{sub 2}O{sub 7}. Additionally, an improvement in the crystalline quality of Cd{sub 2}V{sub 2}O{sub 7} was obtained for the Er-doped samples. The effect of the local environment around the Er{sup 3+} ions on the room temperature photoluminescence was also investigated for the amorphous and crystalline samples. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

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


    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.

  14. Electrochemical reduction of CerMet fuels for transmutation using surrogate CeO2-Mo pellets

    Claux, B.; Souček, P.; Malmbeck, R.; Rodrigues, A.; Glatz, J.-P.


    One of the concepts chosen for the transmutation of minor actinides in Accelerator Driven Systems or fast reactors proposes the use of fuels and targets containing minor actinides oxides embedded in an inert matrix either composed of molybdenum metal (CerMet fuel) or of ceramic magnesium oxide (CerCer fuel). Since the sufficient transmutation cannot be achieved in a single step, it requires multi-recycling of the fuel including recovery of the not transmuted minor actinides. In the present work, a pyrochemical process for treatment of Mo metal inert matrix based CerMet fuels is studied, particularly the electroreduction in molten chloride salt as a head-end step required prior the main separation process. At the initial stage, different inactive pellets simulating the fuel containing CeO2 as minor actinide surrogates were examined. The main studied parameters of the process efficiency were the porosity and composition of the pellets and the process parameters as current density and passed charge. The results indicated the feasibility of the process, gave insight into its limiting parameters and defined the parameters for the future experiment on minor actinide containing material.

  15. Evidence of translocation and physiological impacts of foliar applied CeO2 nanoparticles on cucumber (Cucumis sativus) plants.

    Hong, Jie; Peralta-Videa, Jose R; Rico, Cyren; Sahi, Shivendra; Viveros, Marian N; Bartonjo, Jane; Zhao, Lijuan; Gardea-Torresdey, Jorge L


    Currently, most of the nanotoxicity studies in plants involve exposure to the nanoparticles (NPs) through the roots. However, plants interact with atmospheric NPs through the leaves, and our knowledge on their response to this contact is limited. In this study, hydroponically grown cucumber (Cucumis sativus) plants were aerially treated either with nano ceria powder (nCeO2) at 0.98 and 2.94 g/m(3) or suspensions at 20, 40, 80, 160, and 320 mg/L. Fifteen days after treatment, plants were analyzed for Ce uptake by using ICP-OES and TEM. In addition, the activity of three stress enzymes was measured. The ICP-OES results showed Ce in all tissues of the CeO2 NP treated plants, suggesting uptake through the leaves and translocation to the other plant parts. The TEM results showed the presence of Ce in roots, which corroborates the ICP-OES results. The biochemical assays showed that catalase activity increased in roots and ascorbate peroxidase activity decreased in leaves. Our findings show that atmospheric NPs can be taken up and distributed within plant tissues, which could represent a threat for environmental and human health.

  16. Equilibrium oxygen storage capacity of ultrathin CeO2-δ depends non-monotonically on large biaxial strain

    Balaji Gopal, Chirranjeevi; García-Melchor, Max; Lee, Sang Chul; Shi, Yezhou; Shavorskiy, Andrey; Monti, Matteo; Guan, Zixuan; Sinclair, Robert; Bluhm, Hendrik; Vojvodic, Aleksandra; Chueh, William C.


    Elastic strain is being increasingly employed to enhance the catalytic properties of mixed ion-electron conducting oxides. However, its effect on oxygen storage capacity is not well established. Here, we fabricate ultrathin, coherently strained films of CeO2-δ between 5.6% biaxial compression and 2.1% tension. In situ ambient pressure X-ray photoelectron spectroscopy reveals up to a fourfold enhancement in equilibrium oxygen storage capacity under both compression and tension. This non-monotonic variation with strain departs from the conventional wisdom based on a chemical expansion dominated behaviour. Through depth profiling, film thickness variations and a coupled photoemission-thermodynamic analysis of space-charge effects, we show that the enhanced reducibility is not dominated by interfacial effects. On the basis of ab initio calculations of oxygen vacancy formation incorporating defect interactions and vibrational contributions, we suggest that the non-monotonicity arises from the tetragonal distortion under large biaxial strain. These results may guide the rational engineering of multilayer and core-shell oxide nanomaterials.

  17. Study on application of CeO2 and CaCO3 nanoparticles in lubricating oils

    GU Caixiang; LI Qingzhu; GU Zhuoming; ZHU Guangyao


    The ceria (CeO2) nanoparticles and calcium carbonate (CaCO3) nanoparticles were chosen as additives of anti-wear and extreme pressure for lubricating oils, and the morphology and sizes of nanoparticles were examined using Transmission Electron Microscope (TEM). The tribological performance of lubricating oils containing combined nanoparticles were determined by four-ball friction and wear tester, and the chemical composition of steel ball with worn surface were analyzed by X-ray Photoelectron Spectrum(XPS). The results showed that the lubricating oils containing combined nanoparticles had good anti-wear and friction reducing effects, and the tribological properties were optimal when WCeO2+CaCO3=0.6%, WCeO2:WCaCO3=1:1. The extreme pressure value increased by 40.25%, the wear spot diameter reduced by 33.5%, and friction coefficient reduced by 32% compared with 40CD oil. The coordinated action of big and small particles made anti-wear and friction reducing effective. Tribological chemical reactions resulting from the friction surface formed metal calcium, metal cerium and oxides film, and they could fill up the concave surface and protect the worn surface.

  18. Fabrication of CeO2 by sol-gel process based on microfluidic technology as an analog preparation of ceramic nuclear fuel microspheres

    Ye, Bin; Li, Jiaolong; Zhao, Zichen; Chang, Zhenqi; Serra, Christophe A


    Microfluidics integrated with sol-gel processes is introduced in preparing monodispersed MOX nuclear fuel microspheres using nonactive cerium as a surrogate for uranium or plutonium. The detailed information about microfluidic devices and sol-gel processes are provided. The effects of viscosity and flow rate of continuous and dispersed phase on size and size distribution of CeO2 microspheres have been investigated. A comprehensive characterization of the CeO2 microspheres has been conducted, including XRD pattern, SEM, density, size and size distribution. The size of prepared monodisperse particles can be controlled precisely in range of 10{\\mu}m to 1000{\\mu}m and the particle CV is below 3%.

  19. 纳米CeO2粉体制备方法的研究进展%Prowess in Preparation of Nanometer CeO2

    王瑞芬; 张胤


    综述了近年来国内外纳米CeO2粉体的几种主要制备方法及它们的研究进展,其中重点介绍了液相法及其特点,对纳米CeO2的制备技术和发展趋势进行了展望,并指出了今后应重点研究和解决的主要问题.%Several main methods and their progress of studies on the preparation of nanometer CeO2 in resent years were introduced in this paper. The liquid phase methods were reviewed in detail. The future trend of the preparation technology of nanometer CeO2 was predicted and the main problems which should be resolved in the future research were indicated too.

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

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


    Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at the highest dose of 200 μg mL-1 over the time scale of 72 h, while being able to protect INS-1 cells from H2O2-induced cytotoxicity even after protein adsorption. It is also noteworthy that nanoceria with a smaller hydrodynamic radius exhibit stronger antioxidant and anti-apoptotic effects, which is consistent with their H2O2 quenching capability in biological systems. These findings suggest that nanoceria can be used as an excellent antioxidant for controlling oxidative stress-induced pancreatic β-cell damage.Oxidative stress plays a key role in the occurrence and development of diabetes. With their unique redox properties, CeO2 nanoparticles (nanoceria) exhibit promising potential for the treatment of diabetes resulting from oxidative stress. Here, we develop a novel preparation of hydrophilic CeO2 nanocubes (NCs) with two different sizes (5 nm and 25 nm) via an acetate assisted hydrothermal method. Dynamic light scattering, zeta potential measurements and thermogravimetric analyses were utilized to investigate the changes in the physico-chemical characteristics of CeO2 NCs when exposed to in vitro cell culture conditions. CCK-8 assays revealed that the CeO2 NCs did not impair cell proliferation in the pancreatic β-cell line INS-1 at the highest dose of 200 μg mL-1 over the time scale of 72 h, while being able to protect INS-1 cells from H2O2-induced cytotoxicity even after protein adsorption. It is also noteworthy that nanoceria with a smaller hydrodynamic radius exhibit stronger antioxidant and anti-apoptotic effects, which is consistent with their H2O2 quenching capability in biological systems. These findings suggest that nanoceria can be used as an excellent antioxidant for controlling oxidative stress-induced pancreatic β-cell damage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00826g

  1. Preparation and Optical Investigations of [(Sr1-xBixTiO3]-[2SiO2B2O3]-[CeO2] Glasses

    Chandkiram Gautam


    Full Text Available We are reporting synthesis and structural and optical investigation of strontium bismuth titanate borosilicate glasses with addition of one mole percent cerium oxide (CeO2. Glasses were synthesized by conventional rapid melt quench method. XRD studies of the glass samples confirm the amorphous nature. Infrared absorption spectra various strontium bismuth titanate borosilicate glass samples having glass system 60[(Sr1-xBixTiO3]-39[2SiO2B2O3]-1[CeO2] (x=0.0,0.1,0.2,0.4 were recorded over a continuous spectral range from 400 to 4000 cm−1. IR spectra were analyzed to determine and differentiate of various vibrational modes in the structural change. Raman spectroscopy of all glass samples was also carried out in the wave number range from 200 to 2000 cm−1.

  2. Assessing Hubbard-corrected AM05+U and PBEsol+U density functionals for strongly correlated oxides CeO2 and Ce2O3.

    Weck, Philippe F; Kim, Eunja


    The structure-property relationships of bulk CeO2 and Ce2O3 have been investigated using AM05 and PBEsol exchange-correlation functionals within the frameworks of Hubbard-corrected density functional theory (DFT+U) and density functional perturbation theory (DFPT+U). Compared with conventional PBE+U, RPBE+U, PW91+U and LDA+U functionals, AM05+U and PBEsol+U describe experimental crystalline parameters and properties of CeO2 and Ce2O3 with superior accuracy, especially when +U is chosen close to its value derived by the linear-response approach. The present findings call for a reexamination of some of the problematic oxide materials featuring strong f- and d-electron correlation using AM05+U and PBEsol+U.

  3. Inverse CeO2/CuO catalyst as an alternative to classical direct configurations for preferential oxidation of CO in hydrogen-rich stream.

    Hornés, A; Hungría, A B; Bera, P; López Cámara, A; Fernández-García, M; Martínez-Arias, A; Barrio, L; Estrella, M; Zhou, G; Fonseca, J J; Hanson, J C; Rodriguez, J A


    A novel inverse CeO(2)/CuO catalyst for preferential oxidation of CO in H(2)-rich stream (CO-PROX) has been developed on the basis of a hypothesis extracted from previous work of the group (JACS 2007, 129, 12064). Possible separation of the two competing oxidation reactions involved in the process (of CO and H(2), respectively) is the key to modulation of overall CO-PROX activity and is based on involvement of different sites as most active ones for each of the two reactions. Achievement of large size CuO particles and adequate CeO(2)-CuO interfacial configurations in the inverse catalyst apparently allows appreciable enhancement of the catalytic properties of this kind of system for CO-PROX, constituting an interesting alternative to classic direct configurations so far explored for this process. Reasons for such behavior are analyzed on the basis of operando-XRD, -XAFS, and -DRIFTS studies.

  4. Effects of CeO2 on structure and properties of Ni-Mn-K/bauxite catalysts for water-gas shift reaction

    JIANG Lilong; YE Binghuo; WEI Kemei


    Multiple-metal catalysts (Ni-Mn-Ce-K/bauxite) for Water-Gas Shift (WGS) reaction were prepared by impregnation, and the catalytic structure and properties were investigated by N2 physical, XRD, H2-TPR, and CO-TPD. The results indicated that the addition of 7.5% CeO2 improved the activity of the WGS reaction obviously, and also increased the specific surface area and pore volume of the catalysts. The addition of CeO2 decreases the reduction temperature, enhanced the adsorption and activation of H2O, and improved the adsorption content of CO. Besides, active sites were not changed and the number of active sites on catalysts did not increase obviously.

  5. Fabrication and Mechanical Properties of Sm2O3 Doped CeO2 Reinforced Ti3AlC2 Nano Composite

    Jae Ho Han; Sang Whan Park; Young Do Kim


    The fabrication process of Sm2O3 doped CeO2 reinforced Ti3AlC2 nano composites including the nano particle dispersion process by a hetero-coagulation process was developed using in-situ synthesis and densification process of Ti3AlC2. The effects of Sm2O2 doped CeO2 nano particles on mechanical properties of Ti3AlC2 were investigated. It was found that the presence of 20SDC nano particles in Ti3AlC2 was very effective to improve the mechanical properties of Ti3AlC2 without spoiling the unique characteristics of Ti3AlC2temary carbide.

  6. Thermodynamic Assessment of the ZrO2-CeO2 and ZrO2-CeO1.5 Binary System


    An optimal set of thermodynamic parameters of the ZrO2-CeO1.5 system has been obtained using phase diagram data by modern CALPHAD (CALculation of PHAse Diagrams) technique. The liquid and other solid solution phases were regarded as substitutional solution. The ordered Zr2Ce2O7 phase was treated as a stoichiometric compound. The ZrO2-CeO2 system has been re-optimized with new reference state. A comparison between the ZrO2-CeO2 system and ZrO2-CeO1.5 system has been made through calculation. With the calculation, the experimental information is well reproduced and a good agreement is obtained.

  7. Controlled synthesis of Ce(OH)CO3 flowers by a hydrothermal method and their thermal conversion to CeO2 flowers

    Dongen Zhang; Feng Li; Jian Gu; Qing Xie; Shanzhong Li; Xiaobo Zhang; Guiquan Han; Ailing Ying; Zhiwei Tong


    Highly uniform Ce(OH)CO3 flowers were successfully prepared in large quantities using a facile hydrothermal approach from the reaction of Ce(NH4)(NO3)4 with CO(NH2)2 at 160 ℃ in a water-N2H4 complex,The influences of the N2H4 content and temperature on flower formation were discussed.CeO2 flowers were prepared by thermal conversion of Ce(OH)CO3 flowers at 500 ℃ in air.Both Ce(OH)CO3 and CeO2 flowers were characterized by X-ray powder diffraction (XRD),and scanning electron microscopy (SEM),The UV-vis adsorption spectrum of the CeO2 flowers showed that the band gap energy (Eg) is 2.66 eV,which is lower than that of bulk ceria.

  8. Anchoring High-Concentration Oxygen Vacancies at Interfaces of CeO(2-x)/Cu toward Enhanced Activity for Preferential CO Oxidation.

    Chen, Shaoqing; Li, Liping; Hu, Wanbiao; Huang, Xinsong; Li, Qi; Xu, Yangsen; Zuo, Ying; Li, Guangshe


    Catalysts are urgently needed to remove the residual CO in hydrogen feeds through selective oxidation for large-scale applications of hydrogen proton exchange membrane fuel cells. We herein propose a new methodology that anchors high concentration oxygen vacancies at interface by designing a CeO2-x/Cu hybrid catalyst with enhanced preferential CO oxidation activity. This hybrid catalyst, with more than 6.1% oxygen vacancies fixed at the favorable interfacial sites, displays nearly 100% CO conversion efficiency in H2-rich streams over a broad temperature window from 120 to 210 °C, strikingly 5-fold wider than that of conventional CeO2/Cu (i.e., CeO2 supported on Cu) catalyst. Moreover, the catalyst exhibits a highest cycling stability ever reported, showing no deterioration after five cycling tests, and a super long-time stability beyond 100 h in the simulated operation environment that involves CO2 and H2O. On the basis of an arsenal of characterization techniques, we clearly show that the anchored oxygen vacancies are generated as a consequence of electron donation from metal copper atoms to CeO2 acceptor and the subsequent reverse spillover of oxygen induced by electron transfer in well controlled nanoheterojunction. The anchored oxygen vacancies play a bridging role in electron capture or transfer and drive molecule oxygen into active oxygen species to interact with the CO molecules adsorbed at interfaces, thus leading to an excellent preferential CO oxidation performance. This study opens a window to design a vast number of high-performance metal-oxide hybrid catalysts via the concept of anchoring oxygen vacancies at interfaces.

  9. Contribution of Energetically Reactive Surface Features to the Dissolution of CeO2 and ThO2 Analogues for Spent Nuclear Fuel Microstructures

    Corkhill, C.; Myllykyla, E.; Bailey, D. J.; Thornber, S.M.; Qi, J.; Maldonado, P.; Stennett, M.C.; Hamilton, A.; Hyatt, N.C.


    In the safety case for the geological disposal of nuclear waste, the release of radioactivity from the repository is controlled by the dissolution of the spent fuel in groundwater. There remain several uncertainties associated with understanding spent fuel dissolution, including the contribution of energetically reactive surface sites to the dissolution rate. In this study, we investigate how surface features influence the dissolution rate of synthetic CeO2 and ThO2, spent nuclear fuel analog...

  10. Screening of MgO- and CeO2-Based Catalysts for Carbon Dioxide Oxidative Coupling of Methane to C2+ Hydrocarbons

    Istadi; Nor Aishah Saidina Amin


    The catalyst screening tests for carbon dioxide oxidative coupling of methane (CO2-OCM)have been investigated over ternary and binary metal oxide catalysts. The catalysts are prepared by doping MgO- and CeO2-based solids with oxides from alkali (Li2O), alkaline earth (CaO), and transition metal groups (WO3 or MnO). The presence of the peroxide (O22-) active sites on the Li2O2, revealed by Raman spectroscopy, may be the key factor in the enhanced performance of some of the Li2O/MgO catalysts.The high reducibility of the CeO2 catalyst, an important factor in the CO2-OCM catalyst activity, may be enhanced by the presence of manganese oxide species. The manganese oxide species increases oxygen mobility and oxygen vacancies in the CeO2 catalyst. Raman and Fourier Transform Infra Red (FT-IR) spectroscopies revealed the presence of lattice vibrations of metal-oxygen bondings and active sites in which the peaks corresponding to the bulk crystalline structures of Li2O, CaO, WO3 and MnO are detected. The performance of 5%MnO/15%CaO/CeO2 catalyst is the most potential among the CeO2-based catalysts,although lower than the 2%Li2O/MgO catalyst. The 2%Li2O/MgO catalyst showed the most promising C2+ hydrocarbons selectivity and yield at 98.0% and 5.7%, respectively.

  11. Influence of Different Subsistence States of CeO2-ZrO2 Mixed Oxides in Catalyst Coating on Catalytic Properties


    The metallic substrate-catalysts with different subsistence states of CeO2-ZrO2 mixed oxides were prepared and the catalytic properties were investigated. The studies on CeO2-ZrO2-V2O5-CuO mixed oxides which were prepared by coprecipitation, show that the doping of V5+ and Cu2+ in CeO2-ZrO2 mixed oxides can enhance the catalytic activity and thermal stability of coating materials. Moreover, different additives were doped in slurries of γ-Al2O3 to investigate the influence of additives on oxidation activity of catalysts. The mixture of ceria-zirconia, alkali metals and other rare earths acting as additives exhibits promotion effect on oxidation activity by optimizing the distribution of oxygen on the surface and in the bulk of ceria species. This mentioned mixture was mixed with γ-Al2O3 and a newly proposed active component to prepare a new catalyst. Afterward, the influence of thermal treatment on the new catalyst were investigated by calcinations at 500, 650, 750, 800, 850 and 900 ℃ for 2 h. The light-off curves of CO and HC show that after being treated at 650~750 ℃, catalysts present the best activity. XRD patterns show that ceria and zirconia species in the newly proposed active component form a phase of extra CeO2-ZrO2 mixed oxides on the surface of catalysts after the thermal treatment at 750 ℃, which has practical value for improving the preparation process and promoting the catalytic properties. Moreover, XPS results imply the existence of Ce1-xPdxO2-σ and Ce1-xPtxO2-σ on the surface of these treated samples, which may show influence on the catalytic activities.

  12. Metabolomic effects in HepG2 cells exposed to CeO2, SiO2 and CuO nanomaterials.

    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...

  13. Low temperature destruction of PCDD/Fs over V2O5-CeO2/TiO2 catalyst with ozone.

    Yu, Ming-Feng; Lin, Xiao-Qing; Yan, Mi; Li, Xiao-Dong; Chen, Tong; Yan, Jian-Hua


    Catalytic destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans) over V2O5-CeO2/TiO2 catalyst was investigated at a low temperature range of 140-180 °C, in the absence and presence of ozone (200 ppm). Nano-TiO2 support was used to prepare the catalyst by step impregnation method. A stable PCDD/Fs-generating system was established to support the catalytic destruction tests. In the presence of ozone alone, destruction efficiencies of PCDD/Fs are between 32.2 and 43.1 % with temperature increasing from 140 to 180 °C. The activity of V2O5-CeO2/TiO2 catalyst alone on PCDD/Fs destruction is also studied. The increase of temperature from 140 to 180 °C enhances the activity of catalyst with destruction efficiencies increasing from 54.7 to 73.4 %. However, ozone addition greatly enhances the catalytic activity of V2O5-CeO2/TiO2 catalyst on PCDD/Fs decomposition. At 180 °C, the destruction efficiency of PCDD/Fs achieved with V2O5-CeO2/TiO2 catalyst and ozone is above 86.0 %. It indicates that the combined use of ozone and catalyst reduces the reaction temperature of PCDD/Fs oxidation and offers a new method to destroy PCDD/Fs with high destruction efficiency at a low temperature. Furthermore, the destruction efficiencies of 17 toxic PCDD/F congeners, achieved with ozone alone, catalyst alone, and catalyst/ozone are analyzed.

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

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


    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.

  15. Towards the standardization of nanoecotoxicity testing: Natural organic matter 'camouflages' the adverse effects of TiO2 and CeO2 nanoparticles on green microalgae.

    Cerrillo, Cristina; Barandika, Gotzone; Igartua, Amaya; Areitioaurtena, Olatz; Mendoza, Gemma


    In the last few years, the emission of CeO2 and TiO2 nanoparticles (NPs) into the environment has been raising concerns about their potential adverse effects on wildlife and human health. Aquatic organisms constitute one of the most important pathways for the entrance of these NPs and transfer throughout the food web, but divergences exist in the experimental data published on their aquatic toxicity. The pressing need for standardization of methods to analyze their ecotoxicity requires aquatic media representing realistic environmental conditions. The present study aimed to determine the usefulness of Suwannee River natural organic matter (SR-NOM) in the assessment of the agglomeration kinetics and ecotoxicity of CeO2 and TiO2 NPs towards green microalgae Pseudokirchneriella subcapitata. SR-NOM alleviated the adverse effects of NPs on algal growth, completely in the case of TiO2 NPs and partially in the case of CeO2 NPs, suggesting a 'camouflage' of toxicity. This behavior has been observed also for other algal species and types of natural organic matter in the literature. Furthermore, SR-NOM markedly increased the stability of the NPs in algal medium, which led to a better reproducibility of the toxicity test results, and provided an electrophoretic mobility similar to that previously reported in various river and groundwaters. Thus, SR-NOM can be a representative sample of what is found in many different ecosystems, and the observed 'camouflage' of the effects of CeO2 and TiO2 NPs on algal cells might be considered as a natural interaction occurring in their standardized ecotoxicological assessment.

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

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


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

  17. Metabolomic effects in HepG2 cells exposed to CeO2, SiO2 and CuO nanomaterials.

    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...

  18. Heterogeneous synthesis of dimethylhexane-1,6-dicarbamate from 1,6-hexanediamine and methyl carbonate in methanol over a CeO2 catalyst☆

    Yan Cao; Huiquan Li; Xintao Li; Liguo Wang; Ganyu Zhu; Qing Tang


    The efficient synthesis of dimethylhexane-1,6-dicarbamate (HDC) from 1,6-hexanediamine (HDA) and methyl carbonate over a series of heterogeneous catalysts (e.g., MgO, Fe2O3, Mo2O3, and CeO2) was investigated. The reaction pathway was confirmed as an alcoholysis reaction through a series of designed experiments. Under optimized conditions, 100%HDA conversion with 83.1%HDCtotal and 16.9%polyurea was obtained using a one-step with high temperature procedure with CeO2 as the catalyst. A new two-step with variable temperature technol-ogy was developed based on the reaction pathway to reduce the polyurea yield. Using the proposed method, the HDCtotal yield reached 95.2%, whereas the polyurea yield decreased to 4.8%. The CeO2 catalyst showed high stability and did not exhibit any observable decrease in the HDC yield or any structural changes after four recycling periods. © 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. Al rights reserved.

  19. The use of CeO2-Co3O4 oxides as a catalyst for the reduction of N2O emission

    Rajska Maria


    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.

  20. CeO2 as the Oxygen Carrier for Partial Oxidation of Methane to Synthesis Gas in Molten Salts: Thermodynamic Analysis and Experimental Investigation


    A new technique - the direct partial oxidation of methane to synthesis gas using lattice oxygen in molten salts medium has been introduced. Using CeO2 as the oxygen carrier, thermodynamic data were calculated in the reaction process, and the results indicated that direct partial oxidation of methane to synthesis gas using lattice oxygen of cerium oxide is feasible in theory. In a stainless steel reactor, the effects of temperature and varying amounts of γ-Al2O3 supported CeO2 on CH4 conversion,H2 and CO selectivity, were investigated, respectively. The results show that 10% CeO2/γ-Al2O3 has the maximal reaction activity at a temperature of 865 ℃ and above, the H2/CO ratio in the gas that has been produced reaches 2 and the CH4 conversion, H2 and CO selectivity reached the following percentages: i.e.61%, 89%, and 91% at 870 ℃, respectively. In addition, increase of reaction temperature is favorable for the partial oxidation of methane.

  1. Preparation and characterization of Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst for degradation dye wastewater

    LIU Yan; SUN De-zhi; CHENG Lin; LI Yan-ping


    In order to develop a catalyst with high activity for catalytic wet oxidation (CWO) process at room temperature and atmospheric pressure, Fe2O3-CeO2-TiO2/γ-Al2O3 catalyst was prepared by consecutive impregnation method and the prepared parameters were optimized. The structure of the catalyst was characterized by BET, XRF, SEM and XPS technologies, and the actual wastewater was used to investigate the catalytic activity of Fe2O3-CeO2-TiO2/γ-Al2O3 in CWO process. The experimental results showed that the prepared catalyst exhibited good catalytic activity when the doping amount of Ti was 1.0 wt% (the weight ratio of Ti to carriers), and the middle product, CeO2-TiO2/γ-Al2O3, was calcined in 450℃ for 2 h. The CWO experiment for treating actual dye wastewater indicated that the COD, color and TOC of actual wastewater were decreased by 62.23%, 50.12% and 41.26% in 3 h,respectively, and the ratio of BOD5/COD was increased from 0.19 to 0.30.

  2. Experimental study on a room temperature urea-SCR of NO over activated carbon fibre-supported CeO2-CuO.

    Jiang, Xiao; Lu, Pei; Li, Caiting; Zeng, Zheng; Zeng, Guangming; Hu, Luping; Mai, Lei; Li, Zhi


    In order to establish a desirable method for NO reduction, selective catalytic reduction (SCR) of NO by urea-CeO2/ACF and urea-CeO2-CuO/ACF was carried out at room temperature. The experimental results showed that 10% urea-9% CeO2/ACF could yield the highest NO conversion of 85% among the series of urea-CeO2/ACF prepared. When urea-CeO2-CuO/ACF was compared with urea-CeO2/ACF, it achieved higher NO conversion to a certain degree with the addition of CuO, which was attributed to the synergistic effect between cerium and copper. The effect of the mass ratio of CeO2 and CuO was also observed. The desirable mass ratio of CeO2 and CuO was 1:1, which yielded about 90% NO conversion when ACF was loaded with 10% urea. Furthermore, the influence of O2 concentration and NO concentration was also observed. In this study, NO conversion increased with increasing O2 concentration. In addition, some samples were further characterized by BET, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared methods.

  3. Effects of WOx modification on the activity, adsorption and redox properties of CeO2 catalyst for NOx reduction with ammonia

    Ziran Ma; Duan Weng; Xiaodong WU; Zhichun Si


    A series of WO3/CeO2 (WOx/CeO2) catalysts were synthesized by wet impregnation of ammonium metatungstate on a CeO2 support.The resulting solid acid catalysts were characterized by X-ray diffraction (XRD),UV-Vis spectroscopy (UV-Vis),Raman spectroscopy (Raman),in-situ Fourier transform infrared spectroscopy (in-situ FT-IR) of ammonia adsorption,NH3-TPD,H2 temperatureprogrammed reduction (H2-TPR),NH3/NO oxidation and activity measurements for NOx reduction by NH3 (NH3-SCR).The results show that polytungstate (WOx) species are the main species of tungsten oxide on the surface of ceria.The addition of tungsten oxide enhances the Br(ō)nsted acidity of ceria catalysts remarkably and decreases the amount of surface oxygen on ceria,with strong interaction between CeO2 and WOx.As a result,the N2 selectivity of NH3 oxidation and NH3-SCR at high temperatures (> 300℃) is enhanced.Therefore,a wide working temperature window in which NOx conversion exceeds 80% (NOx conversion > 80%) from 200 to 450℃,is achieved over 10 wt.% WOx/CeO2 catalyst.A tentative model of the NH3-SCR reaction route on WOx/CeO2 catalysts is presented.

  4. Hot Corrosion Studies of Detonation-Gun-Sprayed NiCrAlY + 0.4 wt.% CeO2 Coated Superalloys in Molten Salt Environment

    Kamal, Subhash; Jayaganthan, R.; Prakash, Satya


    Rare earth oxide (CeO2) has been incorporated in NiCrAlY alloy and hot corrosion resistance of detonation-gun-sprayed NiCrAlY + 0.4 wt.% CeO2 coatings on superalloys, namely, superni 75, superni 718, and superfer 800H in molten 40% Na2SO4-60% V2O5 salt environment were investigated at 900 °C for 100 cycles. The coatings exhibited characteristic splat globular dendritic structure with diameter similar to the original powder particles. The weight change technique was used to establish corrosion kinetics. X-ray diffraction (XRD), field emission scanning electron microscopy/energy-dispersive analysis (FE-SEM/EDAX), and x-ray mapping techniques were used to analyze the corrosion products. Coated superfer 800H alloy showed the highest corrosion resistance among the examined superalloys. CeO2 was found to be distributed in the coating along the splat boundaries, whereas Al streaks distributed non-uniformly. The main phases observed for the coated superalloys are oxides of Ni, Cr, Al, and spinels, which are suggested to be responsible for developing corrosion resistance.

  5. Single particle ICP-MS method development for the determination of plant uptake and accumulation of CeO2 nanoparticles.

    Dan, Yongbo; Ma, Xingmao; Zhang, Weilan; Liu, Kun; Stephan, Chady; Shi, Honglan


    Cerium dioxide nanoparticles (CeO2NPs) are among the most broadly used engineered nanoparticles that will be increasingly released into the environment. Thus, understanding their uptake, transportation, and transformation in plants, especially food crops, is critical because it represents a potential pathway for human consumption. One of the primary challenges for the endeavor is the inadequacy of current analytical methodologies to characterize and quantify the nanomaterial in complex biological samples at environmentally relevant concentrations. Herein, a method was developed using single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) technology to simultaneously detect the size and size distribution of particulate Ce, particle concentration, and dissolved cerium in the shoots of four plant species including cucumber, tomato, soybean, and pumpkin. An enzymatic digestion method with Macerozyme R-10 enzyme previously used for gold nanoparticle extraction from the tomato plant was adapted successfully for CeO2NP extraction from all four plant species. This study is the first to report and demonstrate the presence of dissolved cerium in plant seedling shoots exposed to CeO2NPs hydroponically. The extent of plant uptake and accumulation appears to be dependent on the plant species, requiring further systematic investigation of the mechanisms.

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

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


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

  7. Selective catalytic reduction (SCR) of NO by urea loaded on activated carbon fibre (ACF) and CeO2/ACF at 30 degrees C: the SCR mechanism.

    Zeng, Zheng; Lu, Pei; Li, Caiting; Zeng, Guangming; Jiang, Xiao; Zhai, Yunbo; Fan, Xiaopeng


    Selective catalytic reduction (SCR) of NO by urea loaded on rayon-based activated carbon fibre (ACF) and CeO2/ACF (CA) was studied at ambient temperature (30 degrees C) to establish a basic scheme for its reduction. Nitric oxide was found to be reduced to N2 with urea deposited on the ACF and CA. When oxygen was present, the greater the amount of loaded urea (20-60%), the greater the NO(x) conversions, which were between 72.03% and 77.30%, whereas the NO(x) conversions were about 50% when oxygen was absent. Moreover, when the urea was loaded on CA, a catalyst containing 40% urea/ACF loaded with 10% CeO2 (UCA4) could yield a NO(x) conversion of about 80% for 24.5 h. Based on the experimental results, the catalytic mechanisms of SCR with and without oxygen are discussed. The enhancing effect of oxygen resulted from the oxidation of NO to NO2, and urea was the main reducing agent in the SCR of loaded catalysts. ACF-C was the catalytic centre in the SCR of NO of ACF, while CeO2 of urea-loaded CA was the catalytic centre.

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

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


    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).

  9. CeO2对镍基金属陶瓷复合层组织和耐腐蚀性能的影响%Effects of CeO2 on Structure and Corrosion Resistance of Ni-based Metal-Ceramic Coatings

    赵涛; 蔡珣; 王顺兴; 郑世安


    利用5kW CO2激光器在5Cr21Mn9Ni4N不锈钢基体表面成功熔覆了含不同CeO2量的镍基金属陶瓷复合层。研究了稀土氧化物CeO2对激光熔覆金属陶瓷复合层显微组织形态和耐腐蚀性能的影响,发现稀土氧化物CeO2能加速碳化钨颗粒的溶解,促使钨与铬形成金属间化合物;激光熔覆镍基金属陶瓷复合层的耐硫酸腐蚀能力显著优于1Cr18Ni9Ti不锈钢;且含0.5%CeO2(质量分数)的激光熔覆层的耐腐蚀能力比含1.5% CeO2(质量分数)和不含CeO2的激光熔覆层都要强。%The Ni-based metal-ceramic coatings on the surface of 5Cr21Mn9Ni4N stainless steel were clad by a 5kW CO2 laser.The effects of CeO2 on structure and corrosion resistance of laser clad Ni-based metal-ceramic coatings were investigated.The studies revealed that CeO2 could accelerate the dissolution of tungsten carbide particles and made the formation of Cr-W intermetallic compound.Compared with steel 1Cr18Ni9Ti,the corrosion resistance of the laser clad Ni-based metal-ceramic coatings was raised remarkably and the corrosion resistance of the coatings with 0.5wt% CeO2 was better than that of the coatings with 1.5wt% CeO2 and without CeO2.

  10. 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

    Takashi Tsuchiya, Shogo Miyoshi, Yoshiyuki Yamashita, Hideki Yoshikawa, Kazuya Terabe, Keisuke Kobayashi and Shu Yamaguchi


    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.

  11. Surface Acidity/Basicity and Catalytic Reactivity of CeO2/γ-Al2O3 Catalysts for the Oxidative Dehydrogenation of Ethane with Carbon Dioxide to Ethylene

    Xin Ge; Shenghua Hu; Qing Sun; Jianyi Shen


    Dehydrogenation of ethane to ethylene in CO2 was investigated over CeO2/γ-Al2O3 catalysts at 700 ℃ in a conventional flow reactor operating at atmospheric pressure. XRD, BET and microcalorimetric adsorption techniques were used to characterize the structure and surface acidity/basicity of the CeO2/γ-Al2O3 catalysts. The results show that the surface acidity decreased while the surface basicity increased after the addition of CeO2 to γ-Al2O3. Accordingly, the activity of the hydrogenation reaction of CO2 increased, which might be responsible for the enhanced conversion in the dehydrogenation of ethane to ethylene. The highest ethane conversion obtained was about 15% for the 25%CeO2/γ-Al2O3. The selectivity to ethylene was high for all the CeO2, γ-Al2O3 and CeO2/γ-Al2O3 catalysts.

  12. Soot combustion over Ce1-xFexO2-δ and CeO2/Fe2O3 catalysts: Roles of solid solution and interfacial interactions in the mixed oxides

    Li, Hongcheng; Li, Kongzhai; Wang, Hua; Zhu, Xing; Wei, Yonggang; Yan, Dongxia; Cheng, Xianming; Zhai, Kang


    Two series of CeO2-Fe2O3 catalysts (CeO2-based and Fe2O3-supported oxides) with varying composition were synthesized by a hydrothermal method and characterized using various techniques. The comparison on the activity and thermal stability of different catalysts for low-temperature soot oxidation was also performed. The presence of both Ce-Fe-O solid solution and CeO2-Fe2O3 interaction were observed over the two types of catalysts. The oxygen vacancy in the solid solution is the crucial active site to facilitating the soot combustion over the CeO2-based samples. Small CeO2 nanoparticles are well dispersed on the Fe2O3-supported catalysts, which results in the formation of Fe-O-Ce species due to the strong CeO2-Fe2O3 interaction. The Fe-O-Ce species could achieve the coupling of the Ce4+-Ce3+ and Fe3+-Fe2+ couples in the CeO2-Fe2O3 interface, which is also identified as an active species for catalytic soot oxidation. The concentration of oxygen vacancy is closely related to the content of iron in ceria lattice, while the formation of Fe-O-Ce species strongly relies on the particle size of CeO2. It is also found that the oxygen vacancy is more active than the Fe-O-Ce species for soot oxidation, but it is very easy to decompose at high temperature, resulting in obvious deactivation of catalysts. By contrast, the Fe-O-Ce species is very stable under high-temperature treatments. For the fresh samples, the CeO2-based and Fe2O3-supported catalysts showed comparable catalytic activity. After long term aging at 800 °C, the loss on activity over the CeO2-based catalyst (Ce-Fe-O solid solution) is much higher than that over the Fe2O3-supported sample. The Fe2O3-supported catalysts are more suitable for practical application than the Ce-Fe-O solid solution.

  13. Electrochemical degradation of reactive brilliant red X-3B with the (CeO2/C)-β-PbO2-PTFE composite electrode

    孙鹏哲; 陈东辉


    The (CeO2/C)-β-PbO2-PTFE composite electrodes modified by graphite powder, cerium oxide powder, polytetrafluoro-ethylene (PTFE) and the homemadeβ-PbO2 powder were prepared by the high pressure molding technique. The X-ray diffraction (XRD) was used to test the purity of the homemadeβ-PbO2 powder. The surface structure and electrical property of electrodes were characterized by using scanning electron microscopy (SEM) and the cyclic voltammetry curves (CV). Those images indicated that in electrolysis the (CeO2/C)-β-PbO2-PTFE composite electrodes had higher activity than theβ-PbO2-PTFE electrodes, as good as the excellent catalytic performance. In the electrode system the composite electrodes were applied to treat reactive brilliant red (RBR) X-3B solution and we studied the degradation influence factors and the reaction mechanism. The results showed that the electrode system was well in treating RBR X-3B solution with the 20%(CeO2/C)-β-PbO2-PTFE composite electrodes at the initial 100 mg/L RBR X-3B concentration, Na2SO4concentration of 0.35 mol/L, the constant current density of 30 mA/cm2 and electrolyte pH=2. Af-ter electrolytic time of 90 min, the maximum decolorization and chemical oxygen demand (COD) removal rates reached 88.92% and 54.54%. And the decolorization rate of RBR X-3B was in conformity with pseudo-first-order kinetics equation. The RBR X-3B deg-radation mechanism in the electrochemical oxidation system was used with LC-MS to analyze the possible intermediates and degra-dation pathway.

  14. Er掺杂SiNP电子结构和光学性质的第一性原理研究%First-principles Study of Electronic Structure and Optical Properties for Er-doped Silicon Nanoparticles

    王英龙; 王秀丽; 梁伟华; 傅广生


    When the silicon-based photoelectron material is widespread, the structural stability, electronic and optical properties of Er-doped silicon nanoparticles were investigated by first-principles based on density functional theory to provide the theory basis for the silicon-based materials design and application. The results show that the structure is more stable when the Er is in the central position. The doping of Er atom in silicon nanoparticle introduces the impurity levels, which result in the narrowing of band gap. A new absorption peak occurs in the low-energy region of Er-doped silicon nanoparticle, however, the value of the absorption peak decrease gradually, even disappear when the Er move to the surface.%当硅基发光材料得到广泛应用时,为了给硅基材料的设计及应用提供理论依据,利用基于密度泛函理论的第一性原理,对Er掺杂在Si纳米晶粒不同位置的结构稳定性、电子与光学性质进行了研究.结果表明:Er掺杂在Si纳米晶粒的中心位置时,结构最稳定;Er掺杂后的Si纳米晶粒引入了杂质能级,最终导致禁带宽度变窄;掺杂后的Si纳米晶粒在低能区出现了一个新的吸收峰,当Er原子向表面位置移动时,新的吸收峰峰值逐渐减小,甚至消失.

  15. A new approach of CeO2 and La2O3 effects on the three-way catalysts containing low precious metals

    WANG, Wen-Dong; ZHANG, Xiao-Peng; MENG, Ming; YU, Shou-Ming; FU, Yi-Lu; LIN, Pei-Yan


    A series of three-way catalysts (TWCs), containing a small amount of precious metals ( PMs, including Pt, Pd and Rh ) and a large amount of promoters CeO2 and La2O3, were pre pared with different precursor compotmds and various doped mtaners. Crystal phases, dispersion of cerium and lan thamun, textural structure and thermal stability of the cata lysts were investigated by XRD, XPS and pore parameters de termination. The catalytic performance was studied by the measurements of CO, C3H6 and NO conversions on depen dence of temperature at stoichimetric nunber point (S = 1.00), and from S=0.75 to 1.30 at 280℃C or 340℃C for fresh or aged samples, respectively. The correlation between the catalytic performance and the characteristics of fresh and aged samples were discussed. The results show that the sampie, in which CeO2 and La2Os are doped with mixed oxide powders, possesses poor dispersion and less thermal stability, and the conversions of NO and C3H6 are apparently lower than those of the samples aged at 850℃C. The main reason is due to the ianthamum enriclument on the surface. The precious metals and cerium may be covered and enveloped, and the PMs lo cated on the internal microporous su-face where no cerium and lanthanum exist, are easier to sinter and oxidize. For the sample doped with La(NO3)3 and Ce(NO3)3 aqueous solu tions, high dispersion and thermal stable CeO2-La2O3 solid so lution on all the surface of microporous γ-Al2O3 is identified. The solid solution CeO2-La2O3 also possessed high dispersion in the sample doped with La2O3 powder and Ce(NO3)3 aque ous soltion The last two aged samples keep higher NO eon version at S>1 region.

  16. Visible Light Photocatalytic Activity of CeO2-ZnO-TiO2 Composites for the Degradation of Rhodamine B

    Prabhu, S.; Viswanathan, T.; Jothivenkatachalam, K.; Jeganathan, K.


    TiO2 plays a significant role in many applications including solar cell. Consecutively to absorb the low-energy radiation, it is very much essential to tune the optical property of TiO2. We fabricated CeO2-ZnO-TiO2 semiconductor composites by sol-gel method and achieved the absorption of lower energy radiation. The prepared composites were characterized by TG-DTA, UV-DRS, XRD, AFM, TEM and FESEM techniques. The particle and crystalline size of the composites was calculated using FESEM and XRD...

  17. CHx adsorption (x = 1-4) and thermodynamic stability on the CeO2(111) surface: A first-principles investigation

    Fronzi, Marco


    We present an ab initio investigation of the interaction between methane, its dehydrogenated forms and the cerium oxide surface. In particular, the stoichiometric CeO2(111) surface and the one with oxygen vacancies are considered. We study the geometries, energetics and electronic structures of various configurations of these molecules adsorbed on the surface in vacuum, and we extend the analysis to realistic environmental conditions. A phase diagram of the adsorbate-surface system is constructed and relevant transition phases are analyzed in detail, showing the conditions where partial oxidation of methane can occur. © 2014 The Royal Society of Chemistry.

  18. Effects of CeO_2 nanoparticles on microstructure and properties of laser cladded NiCoCrAlY coatings

    王宏宇; 左敦稳; 黎向锋; 陈康敏; 黄铭敏


    CeO2 nanoparticles(nano-CeO2p) were added into laser cladded NiCoCrAlY coatings on Ni-based superalloy substrate to improve the microstructure and properties.Scanning electron microscope(SEM),X-ray diffractometer(XRD),micro-hardness tester,and heat treatment furnace were employed to investigate their morphologies,phases,micro-hardness and thermal shock resistance,compared with the coating without nanoparticles added.The results showed that the microstructure and properties of the coatings with the addition ...

  19. The role of the cationic Pt sites in the adsorption properties of water and ethanol on the Pt4/Pt(111) and Pt4/CeO2(111) substrates: A density functional theory investigation

    Seminovski, Yohanna; Tereshchuk, Polina; Kiejna, Adam; Da Silva, Juarez L. F.


    Finite site platinum particles, Ptn, supported on reduced or unreduced cerium oxide surfaces, i.e., CeO2-x(111) ( 0 CeO2-x has been improved in the last years; however, the identification of the active sites on the Ptn/CeO2-x(111) substrates is still far from complete. In this work, we applied density functional theory based calculations with the addition of the on-site Coulomb interactions (DFT+U) for the investigation of the active sites and the role of the Pt oxidation state on the adsorption properties of water and ethanol (probe molecules) on four selected substrates, namely, Pt(111), Pt4/Pt(111), CeO2(111), and Pt4/CeO2(111). Our results show that water and ethanol preferentially bind in the cationic sites of the base of the tetrahedron Pt4 cluster instead of the anionic lower-coordinated Pt atoms located on the cluster-top or in the surface Ce (cationic) and O (anionic) sites. The presence of the Pt4 cluster contributes to increase the adsorption energy of both molecules on Pt(111) and CeO2(111) surfaces; however, its magnitude increases less for the case of Pt4/CeO2(111). Thus, the cationic Pt sites play a crucial role in the adsorption properties of water and ethanol. Both water and ethanol bind to on-top sites via the O atom and adopt parallel and perpendicular configurations on the Pt(111) and CeO2(111) substrates, respectively, while their orientation is changed once the Pt4 cluster is involved, favoring H binding with the surface sites.

  20. Photorefractive Properties of Potassium Lithium Niobate Crystals with CeO2 and Nd2O3


    KLN and Ce:Nd:KLN crystals were grown by Czochralski method and polarized into single ferroelectrics domain along c-axis. The properties of KLN and Ce:Nd:KLN crystals, such as Curie temperature, Raman spectra, exponential gain coefficient (Г) and thin crystal sheet effect, were measured. The results showed that the two spectra resembling Ce:Nd:KLN crystal were of tetragonal tungsten bronze structure, the exponential gain coefficient of Ce:Nd:KLN crystal was higher than that of KLN crystals and Ce:Nd:KLN crystal had thin crystal sheet effect, for its exponential gain coefficient increasing with crystal sheet thinning. The thin crystal sheet effect of Ce:Nd:KLN crystal was also discussed.

  1. Improving the Photoelectric Characteristics of MoS2 Thin Films by Doping Rare Earth Element Erbium

    Meng, Miaofei; Ma, Xiying


    We investigated the surface morphologies, crystal structures, and optical characteristics of rare earth element erbium (Er)-doped MoS2 (Er: MoS2) thin films fabricated on Si substrates via chemical vapor deposition (CVD). The surface mopography, crystalline structure, light absorption property, and the photoelectronic characteristics of the Er: MoS2 films were studied. The results indicate that doping makes the crystallinity of MoS2 films better than that of the undoped film. Meanwhile, the electron mobility and conductivity of the Er-doped MoS2 films increase about one order of magnitude, and the current-voltage ( I- V) and the photoelectric response characteristics of the Er:MoS2/Si heterojunction increase significantly. Moreover, Er-doped MoS2 films exhibit strong light absorption and photoluminescence in the visible light range at room temperature; the intensity is enhanced by about twice that of the undoped film. The results indicate that the doping of MoS2 with Er can significantly improve the photoelectric characteristics and can be used to fabricate highly efficient luminescence and optoelectronic devices.

  2. Estimation of Ce 4f-5d Interaction by Analysis of Partial Fluorescence Yield at the Ce L3 Edge of CeO2

    Tonai, Hironori; Sasabe, Norimasa; Uozumi, Takayuki; Kawamura, Naomi; Mizumaki, Masaichiro


    Partial fluorescence yield (PFY) spectroscopy, which corresponds to a high-resolution version of the X-ray absorption spectroscopy (XAS), is experimentally performed at the Ce L3 edge of CeO2, and the result is theoretically analyzed using an impurity Anderson model (IAM). In order to estimate the Ce 4f-5d interaction Ufd, we employ a semi-empirical IAM framework based on the local density approximation+U method; Slater-Koster parameters describing the valence of CeO2 are estimated by band mapping within the linear combination of atomic orbitals scheme, and the resulting realistic valence structure is considered in the IAM analysis. The global structure of the PFY-XAS result, which consists of the Ce 2p3/2 → 5d dipole transition and the Ce 2p3/2 → 4f quadrupole transition, is excellently reproduced by the calculation. The Ufd value is estimated to be 3.0 eV. We emphasize that the sensitivity of PFY-XAS to Ufd makes it a good ruler for obtaining the Ufd values of Ce compounds.

  3. Active sites over CuO/CeO2 and inverse CeO2/CuO catalysts for preferential CO oxidation

    Zeng, Shanghong; Wang, Yan; Ding, Suping; Sattler, Jesper J. H. B.; Borodina, Elena; Zhang, Lu; Weckhuysen, Bert M.; Su, Haiquan


    A series of CuO/CeO2 and inverse CeO2/CuO catalysts are prepared by the surfactant-templated method and characterized via XRD, HRTEM, H2-TPR, SEM, XPS, in situ XRD, in situ UV-Vis and N2 adsorption-desorption techniques. It is found that there are two kinds of surface sites in the CuO-CeO2 system, including CuO surface sites for CO chemisorption and CeO2 surface sites with oxygen vacancies for oxygen sorption. The active sites for CO oxidation are located on the contact interface of two-kind surface sites and the lattice oxygen can make a significant contribution to the CO-PROX reaction. The resistance to H2O and CO2 is related to BET surface area, the crystallite sizes of CuO and the reduction behavior of catalysts. The Ce4Cu4 and Ce4Cu1 catalysts exhibit the best resistance against H2O and CO2.

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

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


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

  5. Effect of manganese and potassium addition on CeO2-Al2O3 catalyst for hydrogenation of benzoic acid to benzaldehyde

    CHENG; Dangguo; HOU; Chunyang; CHEN; Fengqiu; ZHAN; Xiaol


    A series of Mn/CeO2-Al2O3 and K/CeO2-Al2O3 catalysts for hydrogenation of benzoic acid to benzaldehyde were prepared to in-vestigate the effect of Mn, K addition on CeO2-Al2O3 catalyst. X-ray diffraction (XRD) and H2-temperature-programmed reduction (H2-TPR) results suggested that the interaction between CeO2 and MnOx enhanced the reducibility of catalysts and therefore benzoic acid conversion.The addition of K increased the number of basic number on the catalyst which leads to a high selectivity to benzaldehyde, but excessive addition imposed negative effects on the catalyst performance. A Mn-K/CeO2Al2O3 catalyst was developed and investigated in the reaction. The simul-taneous addition of Mn and K enhanced not only the catalytic activity but also the capacity to resist the coke formation over catalyst.

  6. Study on characteristics of Ni-W-B composites containing CeO2 nano-particles prepared by pulse electrodeposition

    WANG Junli; XU Ruidong; ZHANG Yuzhi


    Ni-W-B composites containing CeO2 nano-particles on the surface of 45 steel were prepared by pulse electrodeposition,and the influence of pulse frequency,pulse duty circle and heat treatment temperature on the structures and properties were investigated.The results indicated that the pulse co-deposition of Ni,W,B and CeO2 nano-particles led to Ni-W-B/CeO2 composites possessing higher microhardness and better wear resistance when heat-treated at 400 ℃ for 1 h.The microhardness of 636 HV and the deposition rate of 0.0281 mm/h of the as-deposited alloy were the highest at pulse frequency of 1000 Hz,pulse duty circle of 10% and pulse average current density of 10 A/dm2.The composites were mainly in the amorphous state and were partially crystallized as-deposited,and the crystallization trend was strengthened when heat-treated at 400 ℃.Decreasing pulse duty cycle from 75% to 10% was favorable to the refinement in grain strctures and improvement ofmicrostructures.The crystal sizes of the composites were smaller by means of pulse electrodeposition.

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

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


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

  8. Surface reactive species on MnOx(0.4)-CeO2 catalysts towards soot oxidation assisted with pulse dielectric barrier discharge

    付名利; 林俊敏; 朱文波; 吴军良; 陈礼敏; 黄碧纯; 叶代启


    MnOx(0.4)-CeO2 was investigated for soot oxidation assisted with a pulse dielectric barrier discharge (DBD). The catalysts were evaluated and characterized with TPO (temperature programmed oxidation), X-ray diffraction (XRD), Raman and X-ray photo-electron spectroscopy (XPS). The ignition temperature Ti for soot oxidation decreased from 240.8 to 216.4 ºC with the increase of the pulse DBD frequencies from 50 to 400 Hz, lower than that of the case without pulse DBD present (253.4 ºC). The results of XRD, Raman and XPS agreed well with the TPO activities of MnOx(0.4)-CeO2 towards soot oxidation. More solid solution of ceria and manganese, and surface reactive species including O2-, O-and Mn4+were responsible for the enhancement of soot oxidation due to pulse DBD injection in the present study. For solid solution favors to the activation and transformation of those species, which are be-lieved to be involved in the soot oxidation in a hybrid catalysis-plasma.

  9. Synergistic effect between MnO and CeO2 in the physical mixture:Electronic interaction and NO oxidation activity

    吴晓东; 于海宁; 翁端; 刘爽; 樊俊


    MnO and CeO2 powders were mechanically mixed by a spatula and by milling to obtain loose-contact and tight-contact mixed oxides, respectively. The monoxides and their physical mixtures were characterized by X-ray diffraction (XRD), Brun-auer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), Raman, O2 temperature-programmed desorption (O2-TPD), H2 temperature-programmed reduction (H2-TPR) and NO temperature-programmed oxidation (NO-TPO). The MnOx-CeO2 solid solu-tions did not form without any calcination process. The oxidation state of manganese tended to increase while the ionic valence of ce-rium decreased in the mixed oxides, accompanied with the formation of oxygen vacancies. This long-ranged electronic interaction occured more significantly in the tight-contact mixture of MnO and CeO2. The formation of more Mn4+and oxygen vacancies pro-moted the catalytic oxidation of NO in an oxygen-rich atmosphere.

  10. Dispersion state of CuO on CeO2——An incorporation model for the interaction between metal oxide and oxide support

    董林; 金永漱; 陈懿


    XRD and XPS are used to study the dispersion state of CuO on ceria surface.The dispersion capacity values of CuO measured by the two methods are consistent,which are of 1.20 mmol CuO/100 m CeO2.In addition,the results reveal that highly dispersed Cu2 + ions are formed at low CuO loadings and that increasing the CuO content to a value higher than its dispersion capacity produces crystalline CuO after the surface vacant sites on CeO2 are filled.The atomic composition of the outermost layer of the CuO/CeO2 samples has been probed by using static secondary ion mass spectroscopy (SSIMS),and the ratios of Cu/Ce are found to be 0.93 and 0.46 for the 1.22 and 0 61 mmol CuO/CeO2 samples respectively.Temperature-programmed reduction (TPR) profile with two reduction peaks at 156 and 16513 suggests that the reduction of highly dispersed Cu2+ ions consists of two steps and is easier than that of CuO crystallites,in which the TPR profile has only one reduction peak at about 249℃.The above experimental results are in

  11. Gold stabilized aqueous sols immobilized on mesoporous CeO2-Al2O3 as catalysts for the preferential oxidation of carbon monoxide.

    Storaro, Loretta; Lenarda, Maurizio; Moretti, Elisa; Talon, Aldo; Porta, Francesca; Moltrasio, Bernardo; Canton, Patrizia


    Nanostructured Au/Al(2)O(3)-CeO(2) catalysts with a low content of precious metal (0.9% wt.) were prepared immobilizing two different stabilized Au sols on a high surface area Al(2)O(3)-CeO(2) mixed oxide with a uniform pore size distribution, synthesized by a one-pot methodology. The samples were characterized by elemental analysis, N(2) physisorption, XRPD, TEM and (27)Al-MAS NMR techniques. The catalytic activity of the two samples in the preferential oxidation of CO in excess of H(2) (CO-PROX) was comparatively evaluated in the 35-110 degrees C temperature range. The Au-THPS/AlCe20 sample, prepared immobilizing a sol obtained reducing an aqueous solution of gold tetrachloroaurate salt with bis[tetrakis(hydroxymethyl)phosphonium sulfate], resulted very active and selective at low temperatures and its catalytic activity was correlated with the structural characteristics of the metal particles and of the ordered mesoporous support. Copyright 2010 Elsevier Inc. All rights reserved.

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

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


    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.

  13. CeO2-TiO2 catalysts for catalytic oxidation of elemental mercury in low-rank coal combustion flue gas.

    Li, Hailong; Wu, Chang-Yu; Li, Ying; Zhang, Junying


    CeO(2)-TiO(2) (CeTi) catalysts synthesized by an ultrasound-assisted impregnation method were employed to oxidize elemental mercury (Hg(0)) in simulated low-rank (sub-bituminous and lignite) coal combustion flue gas. The CeTi catalysts with a CeO(2)/TiO(2) weight ratio of 1-2 exhibited high Hg(0) oxidation activity from 150 to 250 °C. The high concentrations of surface cerium and oxygen were responsible for their superior performance. Hg(0) oxidation over CeTi catalysts was proposed to follow the Langmuir-Hinshelwood mechanism whereby reactive species from adsorbed flue gas components react with adjacently adsorbed Hg(0). In the presence of O(2), a promotional effect of HCl, NO, and SO(2) on Hg(0) oxidation was observed. Without O(2), HCl and NO still promoted Hg(0) oxidation due to the surface oxygen, while SO(2) inhibited Hg(0) adsorption and subsequent oxidation. Water vapor also inhibited Hg(0) oxidation. HCl was the most effective flue gas component responsible for Hg(0) oxidation. However, the combination of SO(2) and NO without HCl also resulted in high Hg(0) oxidation efficiency. This superior oxidation capability is advantageous to Hg(0) oxidation in low-rank coal combustion flue gas with low HCl concentration.

  14. Viscous properties of new mould flux based on aluminate systemwith CeO2 for continuous casting of RE alloyed heat resistant steel

    QI Jie; LIU Chengjun; LI Chunlong; JIANG Maofa


    The conventional mould fluxes can not be applied to the continuous casting of RE alloyed heat resistant steel, because se-vere slag-metal interface reactions occur generally in the mold. To restrain the interface reaction and improve conditions for continu-ous casting, a new mould flux based on aluminate system was devised. The viscous properties were investigated. Scanning electron microscopy and X-ray diffraction were applied to detect and characterize the crystalline phases in the continuous cooling process. The results showed that appropriate addition of CeO2 could avoid the precipitation of CaO and decrease the viscosity of the mould flux. Increasing the mass ratio of CaO/Al2O3, especially to a value exceeding 1, could worsen the stability of the mould flux. With a con-tent of less than 14 wt.%, Li2O could reduce the viscosity and breaking temperature, but its effect could be weakened for the pro-moted precipitation of LiAlO2. To obtain a mould flux with stable viscous properties, such as viscosity and breaking temperature, ap-propriate contents of CeO2 and Li2O should be controlled to around 10 wt.% and 14 wt.%, while the mass ratio of CaO/Al2O3 should not be more than 1.

  15. CeO2-supported Au38(SR)24 nanocluster catalysts for CO oxidation: a comparison of ligand-on and -off catalysts

    Nie, Xiaotao; Zeng, Chenjie; Ma, Xiangang; Qian, Huifeng; Ge, Qingjie; Xu, Hengyong; Jin, Rongchao


    The catalytic properties of atomically precise, thiolate-protected Au38(SR)24 (R = CH2CH2Ph) nanoclusters supported on CeO2 were investigated for CO oxidation in a fixed bed quartz reactor. Oxygen (O2) thermal pretreatment of Au38(SR)24/CeO2 at a temperature between 100 and 175 °C largely enhanced the catalytic activity, while pretreatment at higher temperatures (>200 °C) for removing thiolate instead gave rise to a somewhat lower activity than that for 175 °C pretreatment, and the ligand-off clusters were also found to be less stable. The CO conversion in the case of wet feed-gas (i.e. the presence of H2O vapor) was appreciably higher than the case of dry feed-gas when the reaction temperature was kept relatively low (between 60 and 80 °C), and interestingly the ligand-on and ligand-off catalysts exhibited opposite response to water vapor. Finally, we discussed some insights into the catalytic reaction involving the well-defined gold nanocluster catalyst.

  16. Probing the interaction of Rh, Co and bimetallic Rh-Co nanoparticles with the CeO2 support: catalytic materials for alternative energy generation.

    Varga, E; Pusztai, P; Óvári, L; Oszkó, A; Erdőhelyi, A; Papp, C; Steinrück, H-P; Kónya, Z; Kiss, J


    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.

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

    Ippolito, Davide; Kammer Hansen, Kent


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

  18. Design and Preparation of MnO2/CeO2-MnO2 Double-Shelled Binary Oxide Hollow Spheres and Their Application in CO Oxidation.

    Zhang, Jian; Cao, Yidan; Wang, Chang-An; Ran, Rui


    Herein, we designed an extremely facile method to prepare well-defined MnO2@CeO2-MnO2 ball-in-ball binary oxide hollow spheres by employing carbon spheres (CSs) as sacrificial templates. The synthesis process involves a novel self-assembled approach to prepare core-shell CSs@CeO2 precursor, which would directly react with KMnO4 aqueous solution to form yolk-shell CSs@MnO2/CeO2-MnO2 precursor in the following step. Well-dispersed Ce-Mn binary oxide with double-shelled hollow sphere structure could be achieved after annealing the precursor in air. The evolution process and formation mechanism of this novel structure were thoroughly studied in this paper. Especially the as-prepared double-shell MnO2/CeO2-MnO2 hollow spheres exhibited enhanced catalytic activity for CO oxidation compared with the pure MnO2 hollow spheres and pure CeO2 hollow spheres. We believe the high surface area, hierarchical porous structures, and strong synergistic interaction between CeO2 and MnO2 contribute to the excellent catalytic activity. Most importantly, this method could be extended to prepare other transition metal oxides. As an example, triple-shelled Co-Mn composite hollow spheres assembled by ultrathin nanoplates were successfully prepared.

  19. S-type Er-Yb Co-doped Phosphate Glass Waveguide Amplifier Integrated with Cascaded Multilayer Medium Thin Film Filter

    CHEN Hai-yan; DAI Ji-zhi; LIU Yong-zhi


    A new S-type of erbium-ytterbium co-doped phosphate glass waveguide amplifier integrated with cascaded multilayer medium thin film filter is proposed,this S-type geometry waveguide structure is used to achieve a long path in a compact chip,and obtained higher gain with lower Er-doped concentration. The cascaded multilayer medium thin film filter is utilized to achieve a broader flattening gain bandwidth.The intrinsical gain spectrum is obtained by solving rate and power propagation equations,the effect of transmittance spectrum of thin film filter on flattening gain is discussed.

  20. Controlled growth of epitaxial CeO2 thin films with self-organized nanostructure by chemical solution method

    Yue, Zhao; Grivel, Jean-Claude


    Chemical solution deposition is a versatile technique to grow oxide thin films with self-organized nanostructures. Morphology and crystallographic orientation control of CeO2 thin films grown on technical NiW substrates by a chemical solution deposition method are achieved in this work. Based...... on an enhanced understanding of the effect of oxygen partial pressure during film crystallization, a strong texture can be obtained on the surface of the CeO2 films annealed at temperatures as low as 900 °C followed by a two-step annealing procedure. Crystallization at high temperature (e.g., 1100 °C...... a fluorite structure but exhibits an alternative in-plane texture with eight fold symmetry on the surface. According to phase and texture stability studies, these off-stoichiometric phases gradually transform back to fully oxidized CeO2 with a 45° rotated cube texture during storage in ambient air. Moreover...

  1. Effect of CeO2 and CaO Promoters on Ignition Performance for Partial Oxidation of Methane over Ni/MgO-Al2O3 Catalyst

    Yejun Qiu; Jixiang Chen; Jiyan Zhang


    The effect of CeO2 and CaO promoters on the ignition performance over Ni/MgO-Al2O3 catalyst for the partial oxidation of methane (POM) to synthesis gas was investigated. It was found that the POM reaction could not be ignited over 1wt%Ni/MgO-Al2O3 catalyst without the promoters in the temperature range from 773 K to 1073 K. CeO2 and CaO promoters enhanced the ignition performance and the POM reactivity of 1wt%Ni/MgO-Al2O3 catalyst remarkably. Moreover, the improving effect became greater with the increase of the promoter content under the investigated reactionconditions. The modification effects of CeO2 and CaO promoters were closely related to the concentration and reducibility of the surface and bulk oxygen species.

  2. Ferroelectric properties of epitaxial Pb(Zr, Ti)O3 thin films on silicon by control of crystal orientation

    Dekkers, Jan M.; Nguyen, Duc Minh; Steenwelle, Ruud Johannes Antonius; te Riele, P.M.; Blank, David H.A.; Rijnders, Augustinus J.H.M.


    Crystalline Pb(Zr,Ti)O3 (PZT) thin films between metallic-oxide SrRuO3 (SRO) electrodes were prepared using pulsed laser deposition on CeO2/yttria-stabilized zirconia buffered silicon (001) substrates. Different deposition conditions for the initial layers of the bottom SRO electrode result in an or

  3. Effect of CeO2 doping on catalytic activity of Fe2O3/gamma-Al2O(3) catalyst for catalytic wet peroxide oxidation of azo dyes.

    Liu, Yan; Sun, Dezhi


    In order to find a catalyst with high activity and stability for catalytic wet peroxide oxidation (CWPO) process under normal condition, with Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) catalysts prepared by impregnation method, the effect of CeO(2) doping on the structure and catalytic activity of Fe(2)O(3)/gamma-Al(2)O(3) for catalytic wet peroxide oxidation of azo dyes at 25 degrees C and atmospheric pressure is evaluated using BET, SEM, XRF, XRD, XPS and chemical analysis techniques, and test results show that, better dispersion and smaller size of Fe(2)O(3) crystal can be achieved by adding CeO(2), and the content of chemisorbed oxygen can also be increased on the surface of catalyst. CWPO experimental results indicate that azo dyes in simulated wastewater can be efficiently mineralized and the catalytic activity of Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) can be increased by about 10% compared with that of Fe(2)O(3)/gamma-Al(2)O(3) because of the promotion of the structural and redox properties of the ferric oxide by ceria doped. Leaching tests indicate that Fe(2)O(3)/gamma-Al(2)O(3) and Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) are stable with a negligible amount of irons found in the aqueous solution after reaction for 2h. It can therefore be concluded from results and discussion that in comparison with Fe(2)O(3)/gamma-Al(2)O(3), Fe(2)O(3)-CeO(2)/gamma-Al(2)O(3) is a suitable catalyst, which can effectively degrade contaminants at normal temperature and atmospheric pressure.

  4. 一种新的CeO2改性渗铬涂层的制备与氧化性能%Preparation and oxidation behavior of a novel CeO2-modified chromizing coating

    孙俭峰; 周月波; 张海军


    利用CeO2颗粒部分替代Al2O3粉作填充剂对电镀纳米Ni和微晶Ni进行800℃低温渗铬,将CeO2颗粒渗入涂层的外层,制备了2种CeO2改性渗铬涂层.采用相同的工艺在微晶Ni上利用不含CeO2的普通渗剂直接渗铬,获得一种不含CeO2粒子的普通渗铬涂层.SEM/EDX和TEM结果表明:基体Ni的细化和CeO2颗粒的渗入有利于得到细晶渗铬涂层.在900℃下氧化时,CeO2颗粒的渗入明显提高了渗铬涂层的抗氧化性能.对于该2种CeO2改性的渗铬涂层,基体Ni的纳米化明显降低了涂层在暂态氧化期的氧化速度,使得在纳米Ni上制备的CeO2改性渗铬涂层具有更好的抗氧化性能.%By using CeO2 particles instead of part of Al2O3 particles as filler,the CeO2 was successfully entrapped into the outer layer of the chromizing coatings on the as-deposited nanocrystalline (NC) and microcrystalline (MC) Ni films using a conventional pack-cementation method at 800 ℃.For comparison,chromizing was also performed under the same condition on MC Ni film using Al2O3 as filler without CeO2 particles.SEM/EDX and TEM results indicate that the refinement of Ni grain and CeO2 entrapped into the chromizing coatings refine the grain of the chromizing coating.Oxidation at 900 ℃ indicates that compared with the CeO2-free chromizing coating,the CeO2-dispersed chromizing coating exhibits an increased oxidation resistance.For the CeO2-dispersed chromizing coating,the refinement of Ni grain size significantly decreases the transient-oxidation scaling rate of the chromizing coatings.Together with this,the CeO2-dispersed chromizing coating formed on NC Ni exhibits a better oxidation resistance.

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

    李红梅; 祝清超; 李移乐; 龚茂初; 陈永东; 王健礼; 陈耀强


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

  6. Visible Light Photocatalytic Activity of CeO2-ZnO-TiO2 Composites for the Degradation of Rhodamine B

    S. Prabhu


    Full Text Available TiO2 plays a significant role in many applications including solar cell. Consecutively to absorb the low-energy radiation, it is very much essential to tune the optical property of TiO2. We fabricated CeO2-ZnO-TiO2 semiconductor composites by sol-gel method and achieved the absorption of lower energy radiation. The prepared composites were characterized by TG-DTA, UV-DRS, XRD, AFM, TEM and FESEM techniques. The particle and crystalline size of the composites was calculated using FESEM and XRD techniques, respectively. The photocatalytic activity of the synthesized composite for the degradation of Rhodamine B (RhB under visible light irradiation was investigated. The photocatalytic degradation of RhB under various experimental conditions such as amount of catalyst, initial dye concentration and H2O2 amount was also demonstrated and the rate constant was calculated using L-H model.

  7. Role of Surface Adsorption in Fast Oxygen Storage/Release of CeO2-ZrO2 Mixed Oxides

    Wu Xiaodong; Liang Qing; Wu Xiaodi; Weng Duan


    Four kinds of CeO2-ZrO2 mixed oxides, i.e., a physical mixture of ceria and zirconia (CZP), zirconia-coated ceria (ZCC), ceria-coated zirconia (CCZ) and a chemical mixture of ceria and zirconia (CZC), were prepared. The oxygen storage capacity (OSC) measurements at 500 ℃ were performed under transient and stationary reaction conditions. All the curves of CO2 evolution during CO-O2 cycles presented a bimodal shape. The first peak was primarily the result of the reaction of CO with the oxygen from the oxides, which was mainly determined by the nature of the material. The second peak was mostly related to the CO2 adsorption behavior and was highly influenced by the surface area and the number of surface active sites. As a result, OSC activity of the samples followed in the order of CZC>CCZ>ZCC≈CZP.

  8. Grain-boundary phases in hot-pressed silicon nitride containing Y2O3 and CeO2 additives

    Guha, J. P.; Hench, L. L.


    Auger electron spectroscopy in conjunction with X-ray powder diffraction and scanning electron microscopy is used to analyze the grain-boundary phases of Y2O3- and CeO2-doped Si3N4 hot-pressed materials in order to demonstrate that the additives concentrate predominantly in the grain boundaries of Si3N4 in the form of various oxynitride phases. A high oxygen content observed in sample fracture surfaces was found to be consistent with the existence of an oxygen-enriched phase in the grain boundaries. The presence of yttrium and cerium in the fracture surfaces and an overall increase in the O/N ratio imply that the additive oxides are predominantly concentrated in the intergranular phases.

  9. Influence of the Electronic Structure and Optical Properties of CeO2 and UO2 for Characterization with UV-Laser Assisted Atom Probe Tomography

    Billy Valderrama; H.B. Henderson; C. Yablinsky; J. Gan; T.R. Allen; M.V. Manuel


    Oxide materials are used in numerous applications such as thermal barrier coatings, nuclear fuels, and electrical conductors and sensors, all applications where nanometer-scale stoichiometric changes can affect functional properties. Atom probe tomography can be used to characterize the precise chemical distribution of individual species and spatially quantify the oxygen to metal ratio at the nanometer scale. However, atom probe analysis of oxides can be accompanied by measurement artifacts caused by laser-material interactions. In this investigation, two technologically relevant oxide materials with the same crystal structure and an anion to cation ratio of 2.00, pure cerium oxide (CeO2) and uranium oxide (UO2) are studied. It was determined that electronic structure, optical properties, heat transfer properties, and oxide stability strongly affect their evaporation behavior, thus altering their measured stoichiometry, with thermal conductance and thermodynamic stability being strong factors.

  10. Effect of Preparation Method on Surface Area and Crystalline Form of CeO2-ZrO2 Solid Solution

    王晓红; 郭耘; 卢冠忠; 郭杨龙; 王筠松; 张志刚; 刘晓晖


    The CeO2-ZrO2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m2·g-1, and that calcined at 900 ℃ for 6 h is 88 m2·g-1.The sample with tetragonal symmetry Ce0.5Zr0.5O2 phase has a higher stability.

  11. Hydrogen transfer reaction of cyclohexanone with 2-propanol catalysed by CeO2-ZnO materials: Promoting effect of ceria

    Braja Gopal Mishra; G Ranga Rao; B Poongodi


    Ce-Zn-O mixed oxides were prepared by amorphous citrate process and decomposition of the corresponding acetate precursors. The resulting materials were characterised by TGA, XRD, UV-Vis-DRS, EPR, SEM and surface area measurements. XRD and DRS results indicated fine dispersion of the ceria component in the ZnO matrix. EPR results clearly indicate the presence of oxygen vacancy and defect centres in the composite oxide. Addition of CeO2 to ZnO produced mixed oxides of high surface area compared to the pure ZnO. Hydrogen transfer reaction was carried out on these catalytic materials to investigate the effect of rare earth oxide on the activity of ZnO. Addition of ceria into zinc oxide was found to increase the catalytic activity for hydrogen transfer reaction. The catalytic activity also depended on the method of preparation. Citrate process results in uniformly dispersed mixed oxide with higher catalytic activity.

  12. Characterization and Catalytic Activity for the Oxidation of Ethane and Propane on Platinum and Copper Supported on CeO2/Al2O3

    Cataluña R.


    Full Text Available Ethane and propane oxidation on platinum and copper supported on Al2O3 and CeO2/Al2O3 catalysts were studied comparatively by examining reaction rates as a function of temperature. Results show that the addition of cerium oxide shifts the catalytic activity to higher temperatures. This negative influence is less pronounced in the case of supported copper samples, which on the basis of EPR and FTIR of adsorbed CO results is attributed to the low relative amount of this metal is in contact with ceria. The decrease in activity the presence of ceria might be due to changes in metal particle size or to the stabilization of the oxidized states of the metals, induced by their interactions with cerium oxide. The higher activity of platinum, in comparison with copper, is attributed to its higher reducibility along with an easier hydrocarbon activation on that metal.

  13. FTIR study of CO adsorption on Rh/MgO modified with Co, Ni, Fe, or CeO2 for the catalytic partial oxidation of methane.

    Li, Dalin; Sakai, Shigemasa; Nakagawa, Yoshinao; Tomishige, Keiichi


    The surface state of Rh/MgO catalysts modified with Co, Ni, Fe, or CeO(2) after the reduction and partial oxidation pretreatments as well as during the catalytic partial oxidation of methane has been investigated by FTIR of adsorbed CO. The results of CO adsorption on the reduced catalysts suggest the formation of Rh-M alloy on Rh-M/MgO (M = Co, Ni, Fe) and Rh particles partially covered with reduced ceria on Rh-CeO(2)/MgO. The strength of CO adsorption on Rh/MgO is weakened by the modification with Co, Ni, Fe, or CeO(2). Partial oxidation pretreatment of Rh/MgO leads to a significant decrease in the CO adsorption due to the oxidation of Rh. In contrast, on partially oxidized Rh-M/MgO (M = Co, Ni, Fe) and Rh-CeO(2)/MgO, the preferential oxidation of the surface M atoms or reduced ceria maintains the metallic Rh and preserves the CO adsorbed on the surface Rh atoms. The CO adsorption during the reaction of catalytic partial oxidation of methane on Rh/MgO and Rh-Ni/MgO is similar to that on the reduced catalysts. On the other hand, the CO adsorption during the reaction on Rh-Co/MgO, Rh-Fe/MgO, and Rh-CeO(2)/MgO is different from that on the reduced catalysts, and this is related to the structural change of these catalysts during the reaction.

  14. The influence of Mn-doped CeO2 on the activity of CuO/CeO2 in CO oxidation and NO + CO model reaction

    Deng, Changshun; Huang, Qingqing; Zhu, Xiying; Hu, Qun; Su, Wenli; Qian, Junning; Dong, Lihui; Li, Bin; Fan, Minguang; Liang, Caiyuan


    This work is mainly focused on the investigation of the influence of Mn-doped CeO2 supported by CuO on the physicochemical and catalytic properties for CO oxidation and NO + CO model reaction. The obtained samples were characterized using N2-physisorption (BET), XRD, LRS, TEM, EDS-Mapping, ICP-AES, XPS, H2-TPR, O2-TPD, in situ DRIFTS, CO oxidation, and NO + CO model reaction. The results imply that appropriate doping MnOx into the lattice of CeO2 will cause an obvious change in the properties of the catalyst and the Cu/CeMn-10: 1 catalyst shows the largest specific surface area, the most uniformity of structure, and the most extent of lattice expansion. A few addition of MnOx is more conducive to the generation of low valence manganese ion in the process of calcination, which may contribute to the synergetic introduction. This further results in more Cu+ due to the shifting of redox equilibrium (Cu2+ + Ce3+ ↔ Cu+ + Ce4+) to right, as well as more oxygen vacancies. Moreover, the capability of Cu/CeMn-10: 1 on desorb/transform/decompose of the adsorbed NO species is more effective than that of Cu/CeO2. The results of catalytic performance show that Cu+/Cu0 species play a key role, and the activity is mainly related to the specific surface area, the content of Cu+ and Ce3+, the reduction, desorption capability of chemisorbed O2- (and/or O-) species as well as adsorption behaviors of these catalysts for CO oxidation and NO + CO reaction. Finally, possible reaction mechanisms are tentatively proposed to understand the reactions.

  15. Effect of transition metal Fe adsorption on CeO2 (110) surface in the methane activation and oxygen vacancy formation: A density functional theory study

    Tian, Dong; Zeng, Chunhua; Wang, Hua; Cheng, Xianming; Zheng, Yane; Xiang, Chao; Wei, Yonggang; Li, Kongzhai; Zhu, Xing


    Methane activation and oxygen vacancy formation over transition metal Fe adsorption on CeO2 (110) are studied by using the method of density functional theory (DFT) + U method. A set of model configurations are generated by placing Fe at five surface sites, viz., O-top site, O-bridge site, Ce-bridge site, Ce-top and double oxygen-bridge sites. The study shows that the energetically most favorable configuration is Fe adsorption at the double oxygen-bridge site. Based on the calculated surface, subsurface and the second oxygen vacancies formation energy with (or without) Fe adsorption, it shows that the Fe adsorption is in favor of the surface, subsurface and second oxygen vacancies formation. For the surface and subsurface oxygen vacancy on the Fe/CeO2 (110) surface, the main factor responsible for lowering of Evac is that the adsorption induces structural distortions, whereas, for the second oxygen vacancy, half can be attributed to the large structural relaxation, half can be attributed to the electronic effects. After calculating and discussing about the CH4 activation on CeO2 (110) and Fe/CeO2 (110) surface with (or without) the surface or subsurface oxygen vacancies at the possible adsorption sites, the results show that when the CH4 adsorbed on the Fe/CeO2 (110) with the surface oxygen vacancy at the Ce1 and Ce2 sites, the CH4 decomposed into the CH(ads) and H(ads), its belongs to the chemical absorption, whereas, when the CH4 adsorbed on the other possible sites, the mentioned phenomenon is not occurred, its belongs to the physical absorption. This study reveals the correlation between surface reducibility and catalytic activity for methane oxidation on cerium-based materials, which might be beneficial in developing improved catalysts for methane combustion.

  16. Effects of Sintering Temperature on Ti/RuO2-CeO2 Electrodes Applied in Super-Capacitors%烧结温度对Ti/RuO2-CeO2超电容性能的影响

    孙俊梅; 王欣; 魏宗平; 邵艳群; 张腾; 唐电


    RuO2-CeO2/Ti electrodes were prepared by thermal decomposition, taking RuCl3 and CeCl3 as raw material, ethanol as solvent and Ti slide as substrate.The microstructures were investigated by means of XRD,SEM and HRTEM. The supercapacitive properties were examined by cyclic voltammetric and chrono-potentiometry measurements. The results showed that the highest specific capacitance was obtained in the electrodes prepared at 300 t, and the electrodes at higher or lower sintering temperature had lower specific capacitances. It is indicated that the capacitive properties of the Ti/RuO2-CeO2 electrodes were influenced by their microstructures. The unstable or well developed structure of the oxides was not good for the supercapacitor performance of the. Electrodes. In the electrodes prepared at 300℃, the amorphous structure with nanocrystals could be found. This kind of microstructure had more electroactive points and lager electrochemical roughness.%以三氯化钌和三氯化铈为原料,以无水乙醇为溶剂,采用热分解法在钛基材上制备了Ti/RuO2-CeO2二元氧化物涂层电极材料,利用XRD,SEM,HR-TEM分析方法对涂层组织结构进行表征,通过循环伏安和充放电曲线来研究涂层的超电容性质.结果表明,300℃烧结制备的电极可获得最大的比电容;烧结温度低于或者超过300℃,电极的超电容性能不佳.分析表明,Ti/RuO2-CeO2的超电容性能与其结构密切相关,氧化物的结构未稳定或发育良好,均不利于提高超电容性能.300℃时涂层形成带有纳米级微晶的非晶组织,获得了高的活性点数和电化学粗糙度.

  17. CeO2对Al2O3基泡沫陶瓷过滤器性能的影响%Effect of CeO2 on Properties of Al2O3-based Ceramic Foam Filters

    马战红; 任凤章


    The effects of CeO2 on the properties of ceramic foam by using polymeric sponge impregnation process are studied.The influences of CeO2 different contents on properties of ceramic foam filter,such as cold compression strength(CCS),thermal shock resistance,volume weight,are investigated.The microstructure of samples is analyzed using scanning electron microscopy(SEM).The results show that the CeO2 used as sintering additives can promote the formation of a liquid phase,reduce the sintering temperature of alumina-based ceramic foam,and improve microstructure and properties of the ceramic.The samples with the best thermal shock resistance and high compression strength are obtained by adding 3% CeO2 respectively.%采用有机泡沫浸渍工艺,研究了CeO2对氧化铝基泡沫陶瓷过滤器性能的影响。通过检测试样的常温耐压强度、热震稳定性、通透率等性能以及利用扫描电镜(SEM)对试样的显微结构进行研究,较为详细地探讨不同含量的CeO2对氧化铝基泡沫陶瓷过滤器性能的影响。结果表明,使用CeO2作添加剂可促进液相的生成,降低氧化铝基泡沫陶瓷的烧成温度,改善瓷体的微观组织结构和性能。实验结果表明,当CeO2含量为3%时其热震稳定性和抗压强度最佳。

  18. Fabrication of Mesoporous Co_3O_4-CeO_2 and their Application in Selective Oxidation of CO%介孔Co_3O_4-CeO_2复合氧化物的制备及在CO选择性氧化中的应用

    刘华; 许珊; 王晓来


    Mesoporous Co3O4-CeO2 mixed oxides was synthesized by a bi-solvent method in which SBA-15 was introduced as the hard template and cerium nitrate and cobalt nitrate were wed as precursors.The active composite and support were characterized by techniques of X-ray powder diffraction,nitrogen adsorption/desorption,temperature programmed reduction and transmission electron microscopy.The experimental results show that the catalyst prepared by the bi-solvent method displayed the uniform mesoporous structure,the smaller particle size,the higher surface area and the high dispersion of active composites compared with the catalysts prepared by impregnation and co-precipitation methods.In addition,the as-prepared mesoporous Co3O4-CeO2 showed a superior performance of CO oxidation over catalysts prepared by traditional preparation protocols of impregnation method and coprecipitation method,which can be ascribed to the high surface area and high dispersion of the catalyst.%以硝酸钴和硝酸铈为前驱物,SBA-15为硬模板,利用双溶剂法制备了Co3O4-CeO2介孔复合氧化物,通过X-射线衍射、N2吸脱附测试、程序升温还原和透射电子显微镜等技术对活性组分及载体进行了表征,并且与浸渍法和共沉淀法所制备的催化剂进行了对比分析.结果表明,相比于浸渍法和共沉淀法,采用双溶剂法制备的介孔Co3O4-CeO2复合氧化物具有均匀的介孔结构、较小的颗粒尺寸、较大的比表面积和较高的活性组分分散度.此外,CO氧化脱除评价显示与常规的共沉淀法和浸渍法所制备的催化剂相比该介孔复合氧化物具有较高的反应活性和选择性,其高活性主要归因于较高的比表面积和活性组分的高分散度.

  19. The CO methanation on Rh/CeO 2 and CeO 2/Rh model catalysts: a comparative study

    Jenewein, B.; Fuchs, M.; Hayek, K.


    Like other reducible oxides, ceria promotes the CO methanation reaction on noble metals, but after high-temperature reduction the promotion is usually reduced and limited to transient conditions. We studied the effect of low- and high-temperature reduction on two types of Rh/ceria model catalysts: "thin film catalysts" consisting of well-defined regular Rh nanoparticles partly embedded in the crystalline ceria support, and "inverse catalysts", i.e. UHV grown ceria submonolayers on polycrystalline Rh surfaces. The turnover rates on either catalyst were related to the free Rh surface area and to the dimensions of the metal-oxide boundary. On thin film catalysts the rates decrease strongly with reduction temperature up to 723 K while no significant structural changes are detectable by ex situ electron microscopy. On ceria-modified surfaces the reaction is initially favoured after reduction below 573 K, but promotion converts to inhibition with increasing reduction temperature. The changing number of Ce III/Ce IV ions on the surface, the oxygen transport to and from the interface, and changes in the free Rh surface area resulting from spreading and reordering of the ceria overlayer are discussed as possible reasons for the observed effects.

  20. A New Strategy for Humidity Independent Oxide Chemiresistors: Dynamic Self-Refreshing of In2 O3 Sensing Surface Assisted by Layer-by-Layer Coated CeO2 Nanoclusters.

    Yoon, Ji-Wook; Kim, Jun-Sik; Kim, Tae-Hyung; Hong, Young Jun; Kang, Yun Chan; Lee, Jong-Heun


    The humidity dependence of the gas sensing characteristics of metal oxide semiconductors has been one of the greatest obstacles for gas sensor applications during the last five decades because ambient humidity dynamically changes with the environmental conditions. Herein, a new and novel strategy is reported to eliminate the humidity dependence of the gas sensing characteristics of oxide chemiresistors via dynamic self-refreshing of the sensing surface affected by water vapor chemisorption. The sensor resistance and gas response of pure In2 O3 hollow spheres significantly change and deteriorate in humid atmospheres. In contrast, the humidity dependence becomes negligible when an optimal concentration of CeO2 nanoclusters is uniformly loaded onto In2 O3 hollow spheres via layer-by-layer (LBL) assembly. Moreover, In2 O3 sensors LBL-coated with CeO2 nanoclusters show fast response/recovery, low detection limit (500 ppb), and high selectivity to acetone even in highly humid conditions (relative humidity 80%). The mechanism underlying the dynamic refreshing of the In2 O3 sensing surfaces regardless of humidity variation is investigated in relation to the role of CeO2 and the chemical interaction among CeO2 , In2 O3 , and water vapor. This strategy can be widely used to design high performance gas sensors including disease diagnosis via breath analysis and pollutant monitoring.

  1. Liquid-Phase Ethanol Oxidation and Gas-Phase CO Oxidation Reactions over M Doped (M = Ag, Au, Pd, and Ni and MM′ Codoped CeO2 Nanoparticles

    Yohan Park


    Full Text Available Transition metal doped metal oxides have been studied extensively for potential applications to environments and chemical industry. Herein, M doped (M = Ag, Au, Pd, and Ni and MM′ codoped CeO2 nanoparticles (NPs were prepared by a hydrothermal method and their liquid-phase ethanol and gas-phase CO oxidation performances were examined by UV-visible absorption spectroscopy and temperature programmed mass spectrometry, respectively. The ethanol and CO oxidation performances were enhanced greatly by metal-doping and were dependent on the relative concentration of codoped metals. For ethanol oxidation, the concentration of acetaldehyde became saturated at low levels, while that of ethyl acetate continuously increased to become a final major product. For M doped CeO2 NPs, the ethanol oxidation performance showed an order of Ni < Ag < Pd ≪ Au. For MM′ codoped CeO2 NPs, the activity of Au doped CeO2 deteriorated drastically upon adding other metals (Ag, Ni, and Pd as a cocatalyst.

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

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


    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.

  3. Investigation of the Poisoning Mechanism of Lead on the CeO2-WO3 Catalyst for the NH3-SCR Reaction via in Situ IR and Raman Spectroscopy Measurement.

    Peng, Yue; Si, Wenzhe; Li, Xiang; Chen, Jianjun; Li, Junhua; Crittenden, John; Hao, Jiming


    The in situ IR and Raman spectroscopy measurements were conducted to investigate lead poisoning on the CeO2-WO3 catalysts. The deactivation mechanisms were studied with respect to the changes of surface acidity, redox property, nitrate/nitrite adsorption behaviors, and key active sites (note that the results of structure-activity relationship of CeO2-WO3 were based on our previous research). (1) Lewis acid sites originated from CeO2 and crystalline WO3, whereas Brønsted acid sites originated from Ce2(WO4)3. The poisoned catalysts exhibited a lower surface acidity than the fresh catalysts: the number of acid sites decreased, and their thermal stability weakened. (2) The reducibility of catalysts and the amount of active oxygen exhibited a smaller influence after poisoning because lead preferred to bond with surface WOx species rather than CeO2. (3) The quantity of active nitrate species decreased due to the lead coverage on the catalyst and the partial bridged-nitrate species induced by lead exhibited a low degree of activity at 200 °C. (4) Crystalline WO3 and Ce2(WO4)3 originated from the transformation of polytungstate sites. These sites were the key active sites during the SCR process. The formation temperatures of polytungstate on the poisoned catalysts were higher than those on the fresh catalysts.

  4. KOH溶液中CeO2-Pd/C对乙醇的电催化研究%Study on CeO2-Pd/C to ethanol electrocatalytic reaction in KOH solution

    刘畅; 田丹妮; 周新文; 代忠旭


    用液相还原法制得CeO2-Pd/C催化剂样品,研究Ce元素对Pd/C催化氧化乙醇能力的影响.通过XRD,循环伏安和计时电流法对实验样品进行了结构表征和催化氧化乙醇行为测试.结果表明,在碱性条件下,CeO2有助于提升Pd/C对乙醇的催化氧化能力.当n(Pd):n(CeO2)=2:1(摩尔比)时,催化效率达到峰值.但当Pd和CeO2的摩尔比达到1:2后,继续增加CeO2的量,其氧化电量基本保持平稳.样品中,Pd和CeO2的摩尔比达到1:2之前,CeO2可以作为Pd的助催化剂;当Pd和CeO2的摩尔比达到1:2之后,CeO2不再作为助催化剂,而可能是成为了催化剂的载体.%To study the influence of catalytic oxidation ability to ethanol of Ce element in Pd/C catalyst , CeO2-Pd/C catalysts were prepared by a liquid phase chemical reduction method. The structure and catalytic oxidation of ethanol behavior of the catalysts were characterized and tested by XRD,cyclic voltammograms and chronoamperometry experiment,respectively. The results show that CeO2 can improve Pd/C catalytic oxidation ability of ethanol in alkaline solution. When n(Pd):n(CeO2) equaled 2:1 (molar ratio),its catalytic efficiency value reached a peak. When the molar ratio of Pd and CeO2 changed less than 1:2,its oxidation capacity remained unchanged basically by increasing the amount of CeO2. It was indicated that CeO2 was a co-catalyst before the molar ratio of Pd to CeO2 was larger than 1:2. After the numerical value was less than 1:2,CeO2 was no longer act as a co-catalyst,but might play a role of the catalyst carrier.

  5. Role of silicon excess in Er-doped silicon-rich nitride light emitting devices at 1.54 μm

    Ramírez, J. M., E-mail:; Berencén, Y.; Garrido, B. [MIND-IN2UB, Department Electrònica, Universitat de Barcelona, Martí i Franquès 1, Barcelona 08028 (Spain); Cueff, S. [Institut des Nanotechnologies de Lyon, École Centrale de Lyon, Écully 69134 (France); Labbé, C. [Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), UMR 6252 CNRS/CEA/Ensicaen/UCBN, Caen 14050 (France)


    Erbium-doped silicon-rich nitride electroluminescent thin-films emitting at 1.54 μm have been fabricated and integrated within a metal-oxide-semiconductor structure. By gradually varying the stoichiometry of the silicon nitride, we uncover the role of silicon excess on the optoelectronic properties of devices. While the electrical transport is mainly enabled in all cases by Poole-Frenkel conduction, power efficiency and conductivity are strongly altered by the silicon excess content. Specifically, the increase in silicon excess remarkably enhances the conductivity and decreases the charge trapping; however, it also reduces the power efficiency. The main excitation mechanism of Er{sup 3+} ions embedded in silicon-rich nitrides is discussed. The optimum Si excess that balances power efficiency, conductivity, and charge trapping density is found to be close to 16%.

  6. Temperature-dependent void formation and growth at ion-irradiated nanocrystalline CeO2 Si interfaces

    Perez-Bergquist, Alex G [ORNL; Zhang, Yanwen [ORNL; Varga, Tamas [Pacific Northwest National Laboratory (PNNL); Moll, Sandra [TN International / AREVA, 1, rue des Hérons, 78182 Montigny Le Bretonneux, France; Namavar, Fereydoon [University of Nebraska Medical Center; Weber, William J [ORNL


    Ceria is a thermally stable ceramic that has numerous applications in the nuclear industry, including use in nuclear fuels and waste forms. Recently, interest has surged in nanostructured ceria due to its increased mechanical properties and electronic conductivity in comparison with bulk ceria and its ability to self-heal in response to energetic ion bombardment. Here, nanocrystalline ceria thin films grown over a silicon substrate are irradiated to fluences of up to 4 1016 ions/cm2 under different irradiation conditions: with differing ion species (Si+ and Ni+), different ion energies (1.0 1.5 MeV), and at varying temperatures (160 600 K). While the nanocrystalline ceria is found to exhibit exceptional radiation resistance under all tested conditions, severe ion irradiation-induced mixing, void formation, and void growth are observed at the ceria/silicon interface, with the degree of damage proving to be temperature dependent.

  7. Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnO(x)-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NO(x).

    Shin, Byeongkil; Chun, Ho Hwan; Cha, Jin-Sun; Shin, Min-Chul; Lee, Heesoo


    The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnO(x)-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NO(x) emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnO(x)-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h(-)1, and its de-NO(x) efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersion state and catalytic acidity on the catalyst surface, and the highly dispersed Mn and Ce on the nano-scaled TiO2 catalyst affects the increase of Lewis and Brønsted acid sites. A CeO2-rich additive on MnO(x)-TiO2 could provide stronger catalytic acid sites, associated with NH3 adsorption and the SCR performance. As the results of sulfur resistance in flue gas that contains SO2, the de-NO(x) efficiency of MnO(x)-TiO2 decreased by 15% over 200 degrees C, whereas that of 30 wt% ceria-doped catalyst increased by 14-21% over 150 degrees C. The high SO2 resistance of CeO2-MnO(x)-TiO2 catalysts that resulted from the addition of ceria suppressed the formation of Mn sulfate species, which led to deactivation on the surface of nano-catalyst.

  8. Methane reforming With CO2 to syngas over CeO2-promoted Ni/Al2O3-ZrO2 catalysts Prepared Via a direct sol-gel process

    Hansheng Li; Hang Xu; Jinfu Wang


    CeO2-promoted Ni/Al2O3-ZrO2 (Ni/Al2O3-ZrO2-CeO2) catalysts were prepared by a direct sol-gel process with citric acid as gelling agent.The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy (IR), thermal gravimetric analysis (TGA), microscopic analysis, X-ray diffraction (XRD) and temperature-programmed reduction (TPR).The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure.TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support.There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable.The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts.The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst.The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.

  9. Análise por difração de raios x de filmes de óxidos cerâmicos compostos por IrO2/TiO2/CeO2

    Alves Valéria Almeida


    Full Text Available Independent of the sample form (powder or film, XRD analysis of Ir0,3Ti(0,7-xCe xO2, (nominal mixtures, for x=0, shows the formation of a solid solution phase between IrO2 and TiO2, as well as the rutile phases of IrO2 and TiO2. The presence of the anatase phase of TiO2 is also confirmed. The introduction of 30 mol% CeO2 in the mixture reveals the presence of the CeO2 and Ce2O3 phases, besides the already mentioned ones, in the powder. In the film form, however, an amorphous phase is identified. When all of the TiO2 is substituded by CeO2, for both sample forms, the only phases found are IrO2, CeO2 and Ce2O3. This result suggests cerium oxides are not capable of forming solid solutions with either IrO2 or (Ir,TiO2 acting solely as a dispersant matrix for these phases. These results are consistent with the much higher electrochemically active surface area when CeO2 is introduced in the binary Ti/Ir0,3Ti0,7O2 mixture. It was possible to establish a relationship between the electrochemical stability of the supported films and their crystalline structure. The unexpected presence of TiO2 and Ti2O3 in the Ti/Ir0,3Ce0,7O2 (film sample is attributed to oxidation of the Ti support during the calcination step.

  10. Morphology, structural properties and reducibility of size-selected CeO2−x nanoparticle films

    Maria Chiara Spadaro


    Full Text Available Non-stoichiometric ceria nanoparticles (NPs were obtained by a gas aggregation source with a magnetron and were mass-selected with a quadrupole mass filter. By varying magnetron power, Ar gas flow, and the length of the aggregation tube, NPs with an average diameter of 6, 9, and 14 nm were synthesized and deposited onto a substrate, thus obtaining NP films. The morphology of the films was studied with scanning electron microscopy, while high resolution transmission electron microscopy was used to gain a deeper insight into the atomic structure of individual NPs. By using X-ray photoelectron spectroscopy we analyzed the degree of reduction of the NPs of different diameters, before and after thermal treatments in vacuum (reduction cycle and in O2 atmosphere (oxidation cycle at different temperatures. From this analysis we inferred that the size is an important parameter only at intermediate temperatures. As a comparison, we evaluated the reducibility of an ultra-thin ceria film with the same surface to volume ratio as the 9 nm diameter NPs film, observing that NPs are more reducible than the ceria film.

  11. CeO2/NaF吸附剂的制备及其对MoF6的吸附性能研究%Preparation of adsorbent CeO2/NaF and its adsorption performance for MoF6

    李洒洒; 程治强; 李杨娟; 龙德武; 龚昱; 窦强; 吴明红; 李晴暖


    Background: The fluoride volatility process has been developed to recover uranium from spent nuclear fuel. And the fluoride adsorption technique is usually applied in the purification and collection of UF6 during the fluoride volatility process.Purpose: This study aims to investigate the characteristics and sorption performance of a novel sorbent CeO2/NaF synthesized by doping NaF with CeF3.Methods: With polymer sodium carboxymethyl cellulose (CMC) as a binder and pore-forming agent, CeF3 and NaFwas mixed according to a mass ratio of 4:9:62, and then water were added (the ratio of CMC to water is 1:6). The porous CeO2/NaF adsorbent particles were prepared by a mixing, molding and sintering process. The characteristics and adsorption performance of the adsorbent particles were analyzed and characterized.Results: Specific surface area of CeO2/NaF was (0.84±0.04)m2·g−1, which was twice of NaF sorbent made under the same process. Porosity was 42.2%, which was larger than that of NaF sorbent. The initial adsorption rate of MoF6 on CeO2/NaF was much higher than that of NaF sorbent. The temperature zone for desorption of MoF6 from CeO2/NaF ranged from 150°C to 300°C, while there were two desorption zones for desorption of MoF6 from NaF sorbent, which varied from 100°C to 300°C and 350°C to 400°C, respectively. This phenomenon showed that CeO2 might stabilize Mo6+in MoF6. Conclusion: The physical properties of NaF could be changed by doping with CeO2, and its adsorption performance was also improved.%将作为粘结剂和造孔剂的高分子羧甲基纤维素钠(Carboxymethylcellulose, CMC)、CeF3和NaF按4:9:62的质量比例混合,再加一定量的水(CMC与水的比为1:6),通过混捏、成形和烧结等程序制得了一种新型的CeO2/NaF吸附剂颗粒。通过研究CeO2的掺杂对NaF吸附剂表观性质和吸附性能的影响发现:CeO2/NaF吸附剂的比表面积为(0.84±0.04) m2·g−1,是相同条件下制得的 NaF 吸附剂的两倍以上;孔隙率为42.2%,也优于NaF吸附剂;CeO2/NaF和NaF吸附剂对MoF6的饱和吸附容量相当,但CeO2/NaF吸附剂的初始吸附速率明显大于NaF吸附剂;吸附于CeO2/NaF吸附剂上的MoF6在150–300°C单个温度段解吸附,而吸附于NaF吸附剂上的MoF6在100–300°C和350–400°C两个温度段发生解吸,表明CeO2的引入在一定程度上起到了稳定MoF6的作用。在NaF吸附剂内掺杂CeO2可以改变NaF吸附剂部分表观性质,从而改善NaF的吸附性能。

  12. Photoluminescence and compositional-structural properties of ion-beam sputter deposited Er-doped TiO{sub 2−x}N{sub x} films: Their potential as a temperature sensor

    Scoca, D., E-mail:; Morales, M.; Merlo, R.; Alvarez, F. [Instituto de Física Gleb Wataghin, UNICAMP, Campinas, São Paulo (Brazil); Zanatta, A. R. [Instituto de Física de São Carlos, USP, São Carlos, São Paulo (Brazil)


    Er-doped TiO{sub 2−x}N{sub x} films were grown by Ar{sup +} ion-beam sputtering a Ti + Er target under different N{sub 2} + O{sub 2} high-purity atmospheres. The compositional-structural properties of the samples were investigated after thermal annealing the films up to 1000 °C under a flow of oxygen. Sample characterization included x-ray photoelectron spectroscopy, grazing incidence x-ray diffraction, Raman scattering, and photoluminescence experiments. According to the experimental data, both composition and atomic structure of the samples were very sensitive to the growth conditions and annealing temperature. In the as-deposited form, the N-rich TiO{sub 2−x}N{sub x} films presented TiN crystallites and no photoluminescence. As the thermal treatments proceed, the films were transformed into TiO{sub 2} and Er{sup 3+}-related light emission were observed in the visible and near-infrared ranges at room-temperature. Whereas the development of TiO{sub 2} occurred due to the insertion-diffusion of oxygen in the films, light emission originated because of optical bandgap widening and/or structural-chemical variations in the vicinity of the Er{sup 3+} ions. Finally, the photoluminescence results in the visible range suggested the potential of the present samples in producing an optically based temperature sensor in the ∼150–500 K range.

  13. Synthesis of Cerium Dioxide High-k Thin Films as a Gate Dielectric in MOS Capacitor

    Anil G. Khairnar


    Full Text Available In the present study, the Al/CeO2 / p-Si MOS capacitor was fabricated by depositing the Aluminium (Al metal layer by thermal evaporation technique on sol-gel derived CeO2 high-k thin films on p-Si substrate. The deposited CeO2 films were characterized by Ellipsometer to study the refractive index that is determined to be 3.62. The FTIR analysis was carried out to obtain chemical bonding characteristics. Capacitance-voltage measurements of Al/CeO2 /p-Si MOS capacitor were carried out to determine the dielectric constant, equivalent oxide thickness (EOT and flat band shift (VFB for the deposited CeO2 film of 16.22, 1.62 nm and 0.7 V respectively. The conductance voltage curve was used to determine the interface trap density (Dit at the CeO2 / p-Si interface that is calculated to be 1.29 × 1013 cm – 2 eV – 1 for measurement frequency of 500 kHz.


    Загайнов, И.; Либерман, Е.; Михайличенко, А.; Конькова, Т.; Почиталкина, И.


    Синтезированы образцы CuO/CeO 2/g-Al 2O 3 и Со 3О 4/CeO 2/g-Al 2O 3 путем импрегнирования растворов нитратов соответствующих солей. Исследована каталитическая активность нанесенных катализаторов в реакции окисления СО. Показано, что каталитическая активность синтезированных образцов определяется химическим составом и способом нанесения вторичного носителя CeO 2 на поверхность g-Al 2O 3.CuO/CeO 2/g-Al 2O 3 and Со 3О 4/CeO 2/g-Al 2O 3 were synthesited by their nitrate salts impregnation.Catalyt...

  15. The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

    Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F


    Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and hence, also affecting the location of the Ce(III) cations and the structure of the TM13 clusters.

  16. Selective catalytic reduction of NO with NH3 over CeO2-ZrO2-WO3 catalysts prepared by different methods

    Ning, Ping; Song, Zhongxian; Li, Hao; Zhang, Qiulin; Liu, Xin; Zhang, Jinhui; Tang, Xiaosu; Huang, Zhenzhen


    The selective catalytic reduction (SCR) of NO by NH3 has been investigated over the CeO2-ZrO2-WO3 (CZW) catalysts prepared by hydrothermal synthesis, incipient impregnation, co-precipitation and sol-gel methods. The results indicate that the CZW catalyst prepared by hydrothermal method shows the best SCR activity, and more than 90% NO conversion is obtained at 195-450 °C with a gas hourly space velocity of 50,000 h-1. The samples are characterized by XRD, N2 adsorption-desorption, SEM, EDS, XPS, H2-TPR, NH3-TPD and Pyridine-IR techniques. The results imply that the superior SCR activity of CZW catalyst is contributed to the excellent redox property, strong acidity and highest content of chemisorbed oxygen species. Furthermore, the larger surface area and greater total pore volume improve the redox ability and enhance NO conversion at low temperature, while the co-existence of Lewis and Brønsted acid sites enhance the SCR activity at high temperature.

  17. Effect of fluorine additive on CeO2(ZrO2)/TiO2 for selective catalytic reduction of NO by NH3.

    Jin, Qijie; Shen, Yuesong; Zhu, Shemin


    A series of CeO2(ZrO2)/TiO2 catalysts with fluorine additive were prepared by impregnation method and tested for selective catalytic reduction (SCR) of NO by NH3. These samples were characterized by XRD, N2-BET, Raman spectra, SEM, TEM, NH3-TPD, H2-TPR and XPS, respectively. Results showed that the optimal catalyst with the appropriate HF exhibited excellent performance for NH3-SCR and more than 96% NO conversion at 360°C under GHSV of 71,400h(-1). It was found that the grain size of TiO2 increased and the specific surface area reduced with the modulation of HF, which was not good for the adsorption of gas molecule. However, the modulation of HF exposed the high energy (001) facets of TiO2 and increased the surface chemisorbed oxygen concentration, oxygen storage capacity and Ce(3+) concentration of catalyst. In addition, the synergy of (101) and (001) facets was beneficial to the improvement of catalytic activity.

  18. Preferential oxidation of CO in excess H2 over the CeO2/CuO catalyst:Effect of initial support

    Zhiming Gao; Yuanyuan Gong; Qiang Zhang; Hao Deng; Yong Yue


    Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperature-programmed reduction (TPR), XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu(OH)2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcina-tion temperatures of 400◦C-600◦C. As a result, Cu(OH)2 is better than CuO as initial support for preferential oxidation of CO in excess H2 (CO-PROX). The best catalytic performance was achieved on the sample calcined at 600◦C and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600◦C. And the atomic ratio of Ce/Cu at 40%led to a proper reducibility for the sample as illustrated by the TPR measurements.

  19. Template-assisted formation of microsized nanocrystalline CeO2 tubes and their catalytic performance in the carboxylation of methanol

    Jörg J. Schneider


    Full Text Available Polymethylmethacrylate (PMMA/ceria composite fibres were synthesized by using a sequential combination of polymer electrospinning, spray-coating with a sol, and a final calcination step to yield microstructured ceria tubes, which are composed of nanocrystalline ceria particles. The PMMA template is removed from the organic/inorganic hybrid material by radio frequency (rf plasma etching followed by calcination of the ceramic green-body fibres. Microsized ceria (CeO2 tubes, with a diameter of ca. 0.75 µm, composed of nanocrystalline agglomerated ceria particles were thus obtained. The 1-D ceramic ceria material was characterized by X-ray diffraction, scanning electron microscopy (SEM, high-resolution transmission electron microscopy (HRTEM, UV–vis and photoluminescence spectroscopy (PL, as well as thermogravimetric analysis (TGA. Its catalytic performance was studied in the direct carboxylation of methanol with carbon dioxide leading to dimethyl carbonate [(CH3O2CO, DMC], which is widely employed as a phosgene and dimethyl sulfate substitute, and as well as a fuel additive.

  20. Total catalytic wet oxidation of phenol and its chlorinated derivates with MnO2/CeO2 catalyst in a slurry

    A. J. Luna


    Full Text Available In the present work, a synthetic effluent of phenol was treated by means of a total oxidation process-Catalyzed Wet Oxidation (CWO. A mixed oxide of Mn-Ce (7:3, the catalyst, was synthesized by co-precipitation from an aqueous solution of MnCl2 and CeCl3 in a basic medium. The mixed oxide, MnO2/CeO2, was characterized and used in the oxidation of phenol in a slurry reactor in the temperature range of 80-130ºC and pressure of 2.04-4.76 MPa. A phenol solution containing 2.4-dichlorophenol and 2.4-dichlorophenoxyacetic acid was also degraded with good results. A lumped kinetic model, with two parallel reaction steps, fits precisely with the integrated equation and the experimental data. The kinetic parameters obtained are in agreement with the Arrhenius equation. The activation energies were determined to be 38.4 for the total oxidation and 53.4 kJ/mol for the organic acids formed.