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Sample records for cerium oxides

  1. Thermodynamic properties of cerium oxide

    International Nuclear Information System (INIS)

    Thermodynamic properties of cerium oxides in the CeO2-CeO1.5 composition range are studied. For this purpose method of electromotive force with solid electrolyte is used, equilibrium constants of reduction of cerium oxides by hydrogen are measured. Necessity of using atmosphere of argon or purified nitrogen to work with pyrophoric cerium oxides is stressed. The obtained results and the earlier known literary data on CeO2 and Ce2O3 thermodynamic properties are tabulated. 14 refs.; 5 tabs

  2. Inhibited oxidation of polymethylsiloxane, containing cerium

    International Nuclear Information System (INIS)

    The kinetics of oxidation of oligomeric polydimethylsiloxane in the presence of cerium-containing organosilicon antioxidant at 285-310 deg was investigated. High energy of activation for initiation process (around 272 kJ/mole) was established as a feature specific for chain oxidation of polydimethylsiloxane. It was found that cerium-containing antioxidant, as well as the iron-containing one, based on iron capronate, is of the ''depleting'' inhibitors, i.e. it looses its inhibiting ability during oxidation

  3. Electrodeposition of Oriented Cerium Oxide Films

    OpenAIRE

    Golden, Teresa D.; Adele Qi Wang

    2013-01-01

    Cerium oxide films of preferred orientation are electrodeposited under anodic conditions. A complexing ligand, acetate, was used to stabilize the cerium (III) ion in solution for deposition of the thin films. Fourier transform infrared spectroscopy showed that the ligand and metal tended to bind as a weakly bidentate complex. The crystallite size of the films was in the nanometer range as shown by Raman spectroscopy and was calculated from X-ray diffraction data. Crystallite sizes from 6 to 2...

  4. Electrochemical reduction of cerium oxide into metal

    International Nuclear Information System (INIS)

    The Fray Farthing and Chen (FFC) and Ono and Suzuki (OS) processes were developed for the reduction of titanium oxide to titanium metal by electrolysis in high temperature molten alkali chloride salts. The possible transposition to CeO2 reduction is considered in this study. Present work clarifies, by electro-analytical techniques, the reduction pathway leading to the metal. The reduction of CeO2 into metal was feasible via an indirect mechanism. Electrolyses on 10 g of CeO2 were carried out to evaluate the electrochemical process efficiency. Ca metal is electrodeposited at the cathode from CaCl2-KCl solvent and reacts chemically with ceria to form not only metallic cerium, but also cerium oxychloride.

  5. Electrochemical reduction of cerium oxide into metal

    Energy Technology Data Exchange (ETDEWEB)

    Claux, Benoit [CEA, Valduc, F-21120 Is-sur-Tille (France); Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France); Serp, Jerome, E-mail: jerome.serp@cea.f [CEA, Valduc, F-21120 Is-sur-Tille (France); Fouletier, Jacques [Universite de Grenoble, LEPMI-ENSEEG, 1130 rue de la Piscine, BP75, F-38402 St Martin d' Heres Cedex (France)

    2011-02-28

    The Fray Farthing and Chen (FFC) and Ono and Suzuki (OS) processes were developed for the reduction of titanium oxide to titanium metal by electrolysis in high temperature molten alkali chloride salts. The possible transposition to CeO{sub 2} reduction is considered in this study. Present work clarifies, by electro-analytical techniques, the reduction pathway leading to the metal. The reduction of CeO{sub 2} into metal was feasible via an indirect mechanism. Electrolyses on 10 g of CeO{sub 2} were carried out to evaluate the electrochemical process efficiency. Ca metal is electrodeposited at the cathode from CaCl{sub 2}-KCl solvent and reacts chemically with ceria to form not only metallic cerium, but also cerium oxychloride.

  6. Photodissociation of Cerium Oxide Nanocluster Cations.

    Science.gov (United States)

    Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A

    2016-04-21

    Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)). PMID:27035210

  7. Structural, optical, morphological and dielectric properties of cerium oxide nanoparticles

    International Nuclear Information System (INIS)

    Cerium oxide (CeO2) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature. (author)

  8. Structural, optical, morphological and dielectric properties of cerium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Prabaharan, Devadoss Mangalam Durai Manoharadoss [Department of Physics, NPR College of Engineering and Technology, Natham, Dindigul, Tamil Nadu (India); Sadaiyandi, Karuppasamy [Department of Physics, Alagappa Government Arts College, Karaikudi, Sivaganga, Tamil Nadu (India); Mahendran, Manickam [Department of Physics, Thiagarajar College of Engineering, Madurai, Tamil Nadu (India); Sagadevan, Suresh, E-mail: duraiphysics2011@gmail.com [Department of Physics, AMET University (India)

    2016-03-15

    Cerium oxide (CeO{sub 2}) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature. (author)

  9. Antibacterial Activity of Polymer Coated Cerium Oxide Nanoparticles

    OpenAIRE

    Shah, Vishal; Shah, Shreya; Shah, Hirsh; Rispoli, Fred J.; McDonnell, Kevin T.; Workeneh, Selam; Karakoti, Ajay; Kumar, Amit; Seal, Sudipta

    2012-01-01

    Cerium oxide nanoparticles have found numerous applications in the biomedical industry due to their strong antioxidant properties. In the current study, we report the influence of nine different physical and chemical parameters: pH, aeration and, concentrations of MgSO4, CaCl2, KCl, natural organic matter, fructose, nanoparticles and Escherichia coli, on the antibacterial activity of dextran coated cerium oxide nanoparticles. A least-squares quadratic regression model was developed to underst...

  10. Uptake and accumulation of bulk and nanosized cerium oxide particles and ionic cerium by radish (Raphanus sativus L.).

    Science.gov (United States)

    Zhang, Weilan; Ebbs, Stephen D; Musante, Craig; White, Jason C; Gao, Cunmei; Ma, Xingmao

    2015-01-21

    The potential toxicity and accumulation of engineered nanomaterials (ENMs) in agricultural crops has become an area of great concern and intense investigation. Interestingly, although below-ground vegetables are most likely to accumulate the highest concentrations of ENMs, little work has been done investigating the potential uptake and accumulation of ENMs for this plant group. The overall objective of this study was to evaluate how different forms of cerium (bulk cerium oxide, cerium oxide nanoparticles, and the cerium ion) affected the growth of radish (Raphanus sativus L.) and accumulation of cerium in radish tissues. Ionic cerium (Ce(3+)) had a negative effect on radish growth at 10 mg CeCl3/L, whereas bulk cerium oxide (CeO2) enhanced plant biomass at the same concentration. Treatment with 10 mg/L cerium oxide nanoparticles (CeO2 NPs) had no significant effect on radish growth. Exposure to all forms of cerium resulted in the accumulation of this element in radish tissues, including the edible storage root. However, the accumulation patterns and their effect on plant growth and physiological processes varied with the characteristics of cerium. This study provides a critical frame of reference on the effects of CeO2 NPs versus their bulk and ionic counterparts on radish growth. PMID:25531028

  11. Chlorination and Carbochlorination of Cerium Oxide

    International Nuclear Information System (INIS)

    The chlorination and carbochlorination of cerium oxide were studied by thermogravimetry under controlled atmosphere (TG) in the 7000C 9500C temperature range.Both reactants and products were analyzed by X-ray diffraction (RX), scanning electronic microscopy (SEM) and energy dispersive spectroscopy (EDS). Thermodynamic calculations were performed by computer assisted software.The chlorination starts at a temperature close to 8000C.This reaction involves the simultaneous formation and evaporation of CeCl3.Both processes control the reaction rate and their kinetic may not be easily separated.The apparent chlorination activation energy in the 8500C-9500C temperature range is 172 to 5 kJ/ mole.Carbon transforms the CeO2-Cl2 into a more reactive system: CeO2-C-Cl2, where the effects of the carbon content, total flow rate and temperature were analyzed.The carbochlorination starting temperature is 7000C.This reaction is completed in one step controlled by mass transfer with an apparent activation energy of 56 to 5 kJ/mole in the 8500C-9500C temperature range

  12. Modulated structures in oxidized cerium niobates

    International Nuclear Information System (INIS)

    Three previously reported oxidized cerium niobate phases CeNbO4+x (x = 0.08, 0.25, and 0.33) have been synthesized and characterized by X-ray powder and electron diffraction. All three phases display structures which are modulated variants of a parent fergusonite-type CeIIINbO4 structure (I2/a, a = 5.5342(2) angstrom, b = 11.4016(6) angstrom, c = 5.1583(3) angstrom, β = 94.600(5)degree). The x = 0.08 phase with parent unit cell (I2/a, a = 5.3029(8) angstrom, b = 11.483(2) angstrom, c = 5.2515(8) angstrom, β = 91.32(2)degree) is a two-dimensional, incommensurately modulated phase characterized by incommensurate primary modulation wavevectors q1 ∼ [0.345, 0, 0.138]p* and q2 ∼ [-0.069, 0, 0.172]p* (p for parent). The x = 0.25 phase with parent unit cell (I2/a, a = 5.3522(8) angstrom, b = 11.374(3) angstrom, c = 5.116(1) angstrom, β = 93.34(2)degree) is a commensurately modulated superstructure phase characterized by the reciprocal space unit cell ar* = 1/12[402]p*, br* = 1/4[020]p*, and cr* = 1/3[101]p* (r for resultant). The x = 0.33 phase with parent unit cell (I1, a = 5.4374(8) angstrom, b = 11.189(2) angstrom, c = 5.1458(8) angstrom, α = 90.56(1), β = 94.37(1), γ = 88.19(1)degree) is again commensurately modulated with q = 1/3[101]p*. The close structural relationship between the three oxidized phases and possible interstitial oxygen sites in the CeIIINbO4 structure are discussed

  13. Optical and electrical studies of cerium mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Sherly, T. R., E-mail: trsherly@gmail.com [Post Graduate Department of Physics, Sanathana Dharma College, Alappuzha, Kerala (India); Raveendran, R. [Nanoscience Research Laboratory, Sree Narayana College, Kollam, Kerala 691001 (India)

    2014-10-15

    The fast development in nanotechnology makes enthusiastic interest in developing nanomaterials having tailor made properties. Cerium mixed oxide materials have received great attention due to their UV absorption property, high reactivity, stability at high temperature, good electrical property etc and these materials find wide applications in solid oxide fuel cells, solar control films, cosmetics, display units, gas sensors etc. In this study cerium mixed oxide compounds were prepared by co-precipitation method. All the samples were doped with Zn (II) and Fe (II). Preliminary characterizations such as XRD, SEM / EDS, TEM were done. UV - Vis, Diffuse reflectance, PL, FT-IR, Raman and ac conductivity studies of the samples were performed.

  14. Synthesis and characterization of magnesium doped cerium oxide for the fuel cell application

    Science.gov (United States)

    Kumar, Amit; Kumari, Monika; Kumar, Mintu; Kumar, Sacheen; Kumar, Dinesh

    2016-05-01

    Cerium oxide has attained much attentions in global nanotechnology market due to valuable application for catalytic, fuel additive, and widely as electrolyte in solid oxide fuel cell. Doped cerium oxide has large oxygen vacancies that allow for greater reactivity and faster ion transport. These properties make cerium oxide suitable material for SOFCs application. Cerium oxide electrolyte requires lower operation temperature which shows improvement in processing and the fabrication technique. In our work, we synthesized magnesium doped cerium oxide by the co-precipitation method. With the magnesium doping catalytic reactivity of CeO2 was increased. Synthesized nanoparticle were characterized by the XRD and UV absorption techniques.

  15. Electrical measurements in the cerium oxide doped samples

    International Nuclear Information System (INIS)

    Electrical behaviour of an interface formed by cerium oxide doped system has been studied. The system was (Ce O2)1-0,005 (Y O 1,5)0,005/(Ce O2)1-0,14(Y O 1,5)0,14. This work relates results of impedance analysis, and curves U(I) at different temperatures and polarizations conditions. (author)

  16. Thin film growth of epitaxial gadolinium oxide, gadolinium yttrium oxide, and gadolinium cerium oxide by electrodeposition

    International Nuclear Information System (INIS)

    Thin films of gadolinium oxide, gadolinium yttrium oxide, and gadolinium cerium oxide were electrodeposited from non-aqueous baths. The films were on the order of 15 nm thick, and were grown epitaxially on textured nickel-tungsten substrates. The effect of deposition rate, annealing temperature and secondary metals on crystallinity and crystal orientation was investigated by X-ray diffraction and transmission electron microscopy. Slower rates, higher temperatures and low concentrations of yttrium improve the crystallinity of gadolinium oxide films, whereas the introduction of cerium induced polycrystallinity.

  17. Thin film growth of epitaxial gadolinium oxide, gadolinium yttrium oxide, and gadolinium cerium oxide by electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Mann, Jonathan R., E-mail: jonathan.mann@nrel.gov; Bhattacharya, Raghu N.

    2010-10-29

    Thin films of gadolinium oxide, gadolinium yttrium oxide, and gadolinium cerium oxide were electrodeposited from non-aqueous baths. The films were on the order of 15 nm thick, and were grown epitaxially on textured nickel-tungsten substrates. The effect of deposition rate, annealing temperature and secondary metals on crystallinity and crystal orientation was investigated by X-ray diffraction and transmission electron microscopy. Slower rates, higher temperatures and low concentrations of yttrium improve the crystallinity of gadolinium oxide films, whereas the introduction of cerium induced polycrystallinity.

  18. Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine

    OpenAIRE

    Nelson, Bryant C.; Monique E. Johnson; Walker, Marlon L.; Riley, Kathryn R.; Christopher M. Sims

    2016-01-01

    Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where o...

  19. Fungus mediated synthesis of biomedically important cerium oxide nanoparticles

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • First time biological synthesis of cerium oxide oxide nanoparticles using fungus Humicola sp. • Complete characterization of cerium oxide nanoparticles. • Biosynthesis of naturally protein capped, luminescent and water dispersible CeO2 nanoparticles. • Biosynthesized CeO2 nanoparticles can be used for many biomedical applications. - Abstract: Nanomaterials can be synthesized by chemical, physical and the more recently discovered biological routes. The biological routes are advantageous over the chemical and physical ones as unlike these, the biological synthesis protocols occur at ambient conditions, are cheap, non-toxic and eco-friendly. Although purely biological and bioinspired methods for the synthesis of nanomaterials are environmentally benign and energy conserving processes, their true potential has not been explored yet and attempts are being made to extend the formation of technologically important nanoparticles using microorganisms like fungi. Though there have been reports on the biosynthesis of oxide nanoparticles by our group in the past, no attempts have been made to employ fungi for the synthesis of nanoparticles of rare earth metals or lanthanides. Here we report for the first time, the bio-inspired synthesis of biomedically important cerium oxide (CeO2) nanoparticles using the thermophilic fungus Humicola sp. The fungus Humicola sp. when exposed to aqueous solutions of oxide precursor cerium (III) nitrate hexahydrate (CeN3O9·6H2O) results in the extracellular formation of CeO2 nanoparticles containing Ce (III) and Ce (IV) mixed oxidation states, confirmed by X-ray Photoemission Spectroscopy (XPS). The formed nanoparticles are naturally capped by proteins secreted by the fungus and thus do not agglomerate, are highly stable, water dispersible and are highly fluorescent as well. The biosynthesized nanoparticles were characterized by UV–vis spectroscopy, Photoluminescence spectroscopy (PL), Transmission

  20. Fundamental aspects of regenerative cerium oxide nanoparticles and their applications in nanobiotechnology

    Science.gov (United States)

    Patil, Swanand D.

    Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1muM in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide

  1. Antioxidant activity of levan coated cerium oxide nanoparticles.

    Science.gov (United States)

    Kim, Sun-Jung; Chung, Bong Hyun

    2016-10-01

    Levan coated cerium oxide nanoparticles (LCNPs) with the enhanced antioxidant activity were successfully synthesized and characterized. Levan and their derivatives are attractive for biomedical applications attributable to their antioxidant, anti-inflammation and anti-tumor properties. LCNPs were synthesized using the one-pot and green synthesis system with levan. For production of nanoparticles, levan plays a role as a stabilizing and reducing agent. Fourier transform infrared spectroscopy (FT-IR) analysis showed that LCNPs successfully synthesized. The morphology and size of nanoparticles were confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). LCNPs have good water solubility and stability. The conjugation of levan with cerium oxide nanoparticles improved antioxidant activity. Moreover the level of ROS was reduced after treatment of LCNPs to H2O2 stimulated NIH3T3 cells. These results demonstrate that the LCNPs are useful for applying of treatment of ROS induced diseases. PMID:27312651

  2. Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

    Energy Technology Data Exchange (ETDEWEB)

    Shih, C.J., E-mail: cjshih@kmu.edu.tw [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 807, Taiwan (China); Chen, Y.J. [Institute of Biomedical Sciences, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Hon, M.H. [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

    2010-05-15

    Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol{sup -1}.

  3. Synthesis and crystal kinetics of cerium oxide nanocrystallites prepared by co-precipitation process

    International Nuclear Information System (INIS)

    Cerium oxide nanocrystallites were synthesized at a relatively low temperature using cerium nitrate as starting materials in a water solution by a co-precipitation process. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K by XRD analysis. When calcined from 473 to 1273 K, the crystallization of the face-centered cubic phase was observed by XRD. The crystallite size of the cerium oxide increased from 10.0 to 43.8 nm with calcining temperature increasing from 673 to 1273 K. The activation energy for growth of cerium oxide nanoparticles was found to be 16.0 kJ mol-1.

  4. Induction of pulmonary fibrosis by cerium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jane Y., E-mail: jym1@cdc.gov [Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505 (United States); Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Scabilloni, James [Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505 (United States); Ma, Joseph K. [School of Pharmacy, West Virginia University, Morgantown, WV 26506 (United States); Castranova, Vincent [Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505 (United States)

    2012-08-01

    Cerium compounds have been used as a diesel engine catalyst to lower the mass of diesel exhaust particles, but are emitted as cerium oxide (CeO{sub 2}) nanoparticles in the diesel exhaust. In a previous study, we have demonstrated a wide range of CeO{sub 2}-induced lung responses including sustained pulmonary inflammation and cellular signaling that could lead to pulmonary fibrosis. In this study, we investigated the fibrogenic responses induced by CeO{sub 2} in a rat model at various time points up to 84 days post-exposure. Male Sprague Dawley rats were exposed to CeO{sub 2} by a single intratracheal instillation. Alveolar macrophages (AM) were isolated by bronchial alveolar lavage (BAL). AM-mediated cellular responses, osteopontin (OPN) and transform growth factor (TGF)-β1 in the fibrotic process were investigated. The results showed that CeO{sub 2} exposure significantly increased fibrotic cytokine TGF-β1 and OPN production by AM above controls. The collagen degradation enzymes, matrix metalloproteinase (MMP)-2 and -9 and the tissue inhibitor of MMP were markedly increased in the BAL fluid at 1 day- and subsequently declined at 28 days after exposure, but remained much higher than the controls. CeO{sub 2} induced elevated phospholipids in BAL fluid and increased hydroxyproline content in lung tissue in a dose- and time-dependent manner. Immunohistochemical analysis showed MMP-2, MMP-9 and MMP-10 expressions in fibrotic regions. Morphological analysis noted increased collagen fibers in the lungs exposed to a single dose of 3.5 mg/kg CeO{sub 2} and euthanized at 28 days post-exposure. Collectively, our studies show that CeO{sub 2} induced fibrotic lung injury in rats, suggesting it may cause potential health effects. -- Highlights: ► Cerium oxide exposure significantly affected the following parameters in the lung. ► Induced fibrotic cytokine OPN and TGF-β1 production and phospholipidosis. ► Caused imbalance of the MMP-9/ TIMP-1 ratio that favors fibrosis

  5. Induction of pulmonary fibrosis by cerium oxide nanoparticles

    International Nuclear Information System (INIS)

    Cerium compounds have been used as a diesel engine catalyst to lower the mass of diesel exhaust particles, but are emitted as cerium oxide (CeO2) nanoparticles in the diesel exhaust. In a previous study, we have demonstrated a wide range of CeO2-induced lung responses including sustained pulmonary inflammation and cellular signaling that could lead to pulmonary fibrosis. In this study, we investigated the fibrogenic responses induced by CeO2 in a rat model at various time points up to 84 days post-exposure. Male Sprague Dawley rats were exposed to CeO2 by a single intratracheal instillation. Alveolar macrophages (AM) were isolated by bronchial alveolar lavage (BAL). AM-mediated cellular responses, osteopontin (OPN) and transform growth factor (TGF)-β1 in the fibrotic process were investigated. The results showed that CeO2 exposure significantly increased fibrotic cytokine TGF-β1 and OPN production by AM above controls. The collagen degradation enzymes, matrix metalloproteinase (MMP)-2 and -9 and the tissue inhibitor of MMP were markedly increased in the BAL fluid at 1 day- and subsequently declined at 28 days after exposure, but remained much higher than the controls. CeO2 induced elevated phospholipids in BAL fluid and increased hydroxyproline content in lung tissue in a dose- and time-dependent manner. Immunohistochemical analysis showed MMP-2, MMP-9 and MMP-10 expressions in fibrotic regions. Morphological analysis noted increased collagen fibers in the lungs exposed to a single dose of 3.5 mg/kg CeO2 and euthanized at 28 days post-exposure. Collectively, our studies show that CeO2 induced fibrotic lung injury in rats, suggesting it may cause potential health effects. -- Highlights: ► Cerium oxide exposure significantly affected the following parameters in the lung. ► Induced fibrotic cytokine OPN and TGF-β1 production and phospholipidosis. ► Caused imbalance of the MMP-9/ TIMP-1 ratio that favors fibrosis. ► Cerium oxide particles were detected in

  6. EIS study of nano crystalline Ni-cerium oxide coating electrodeposition mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Hasannejad, H. [Department of Materials Science and Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Shahrabi, T., E-mail: Tshahrabi34@modares.ac.ir [Department of Materials Science and Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Jafarian, M. [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 15875-4416, Tehran (Iran, Islamic Republic of); Rouhaghdam, A. Sabour [Department of Materials Science and Engineering, Tarbiat Modares University, Tehran (Iran, Islamic Republic of)

    2011-02-03

    Research highlights: > In this study a new procedure was used for electrodeposition of Ni-cerium oxide amorphous-nano crystalline composite coatings. The innovation of this method is that the metal and oxides are deposited simultaneously on the samples from the plating bath solution containing Ni ions and Ce ions with no powder added. - Abstract: In this study a novel procedure was used for the electrodeposition of Ni-cerium oxide nano crystalline composite coatings. The novelty of this method lies in the fact that the metal and the oxide are both deposited simultaneously on the substrate, directly from the plating bath containing Ni and Ce ions with no oxide powder addition. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were used to study the mechanisms of Ni-CeO{sub 2} nanocomposite coating deposition. The results indicated that the morphology of Ni-cerium oxide coatings varied based on the Ni:Ce ion ratio. When this ratio exceeds 100, sporadic distribution of cerium oxide in the Ni matrix occurred. On the other hand, when the aforementioned ratio was less than 100, it was found that Ni species were dispersed in a continuous film of cerium oxide. Furthermore, it was observed that Ni in Ni-cerium oxide composite coating was nanocrystalline, while cerium oxide was amorphous. Introduction of the cerium ions to the plating bath resulted in the reduction of the Ni grains average size.

  7. EIS study of nano crystalline Ni-cerium oxide coating electrodeposition mechanism

    International Nuclear Information System (INIS)

    Research highlights: → In this study a new procedure was used for electrodeposition of Ni-cerium oxide amorphous-nano crystalline composite coatings. The innovation of this method is that the metal and oxides are deposited simultaneously on the samples from the plating bath solution containing Ni ions and Ce ions with no powder added. - Abstract: In this study a novel procedure was used for the electrodeposition of Ni-cerium oxide nano crystalline composite coatings. The novelty of this method lies in the fact that the metal and the oxide are both deposited simultaneously on the substrate, directly from the plating bath containing Ni and Ce ions with no oxide powder addition. Electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were used to study the mechanisms of Ni-CeO2 nanocomposite coating deposition. The results indicated that the morphology of Ni-cerium oxide coatings varied based on the Ni:Ce ion ratio. When this ratio exceeds 100, sporadic distribution of cerium oxide in the Ni matrix occurred. On the other hand, when the aforementioned ratio was less than 100, it was found that Ni species were dispersed in a continuous film of cerium oxide. Furthermore, it was observed that Ni in Ni-cerium oxide composite coating was nanocrystalline, while cerium oxide was amorphous. Introduction of the cerium ions to the plating bath resulted in the reduction of the Ni grains average size.

  8. Cathodic electrodeposition of cerium-based oxides on carbon steel from concentrated cerium nitrate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Hamlaoui, Y. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France); Pedraza, F. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France)], E-mail: fpedraza@univ-lr.fr; Remazeilles, C.; Cohendoz, S.; Rebere, C. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France); Tifouti, L. [Laboratoire de Genie de l' Environnement, Universite Badji Mokhtar, BP 1223, 23020 El Hadjar-Annaba (Algeria); Creus, J. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France)

    2009-02-15

    In this work the elaboration by cathodic electrodeposition of cerium-based oxides on carbon steel from relatively concentrated cerium nitrate solutions is investigated. In particular, the study presented here (Part I) focuses on the electrochemical and analytical characterisation of the films and on the correlations between the electrochemical features and the characteristics of the layers. The effect of other parameters such as concentration, temperature, pH and additives to improve the behaviour of the film against corrosion will be investigated in part II of the study. The electrochemical characterisation will reveal that Ce(IV)-steel interactions can be responsible for some weak electrochemical waves appearing in the cyclic voltammograms that often are attributed to oxygen or nitrates reduction. This results from the oxidation of Ce(III) solutions to Ce(IV) in contact with air. Furthermore, the deposits strongly depend on the applied current density. Low current densities do not render fully covering deposits on the steel and a carbonated green rust will appear. On the contrary, the increase of the current density leads to denser layers of relatively small crystallite size that readily covers the steel surface. The deposits have a needle-like morphology and the Ce content achieves a plateau of about 20-22 at.%. However, a significant network of cracks appears probably occurring during the deposition process itself. The differential scanning calorimetry (DSC) results indicate that the deposits are not fully crystalline after 550 deg. C in contrast with the X-ray diffraction (XRD) patterns that unambiguously show a fluorite-type CeO{sub 2} phase whose crystallite size decreases with increasing the current density. The rinsing medium also brings about different features of the films. Rinsing with water allows to incorporate more nitrates and to adsorb CO{sub 2} than when rinsing with ethanol. However, R-OH bonds will be trapped in the latter.

  9. Cathodic electrodeposition of cerium-based oxides on carbon steel from concentrated cerium nitrate solutions

    International Nuclear Information System (INIS)

    In this work the elaboration by cathodic electrodeposition of cerium-based oxides on carbon steel from relatively concentrated cerium nitrate solutions is investigated. In particular, the study presented here (Part I) focuses on the electrochemical and analytical characterisation of the films and on the correlations between the electrochemical features and the characteristics of the layers. The effect of other parameters such as concentration, temperature, pH and additives to improve the behaviour of the film against corrosion will be investigated in part II of the study. The electrochemical characterisation will reveal that Ce(IV)-steel interactions can be responsible for some weak electrochemical waves appearing in the cyclic voltammograms that often are attributed to oxygen or nitrates reduction. This results from the oxidation of Ce(III) solutions to Ce(IV) in contact with air. Furthermore, the deposits strongly depend on the applied current density. Low current densities do not render fully covering deposits on the steel and a carbonated green rust will appear. On the contrary, the increase of the current density leads to denser layers of relatively small crystallite size that readily covers the steel surface. The deposits have a needle-like morphology and the Ce content achieves a plateau of about 20-22 at.%. However, a significant network of cracks appears probably occurring during the deposition process itself. The differential scanning calorimetry (DSC) results indicate that the deposits are not fully crystalline after 550 deg. C in contrast with the X-ray diffraction (XRD) patterns that unambiguously show a fluorite-type CeO2 phase whose crystallite size decreases with increasing the current density. The rinsing medium also brings about different features of the films. Rinsing with water allows to incorporate more nitrates and to adsorb CO2 than when rinsing with ethanol. However, R-OH bonds will be trapped in the latter

  10. Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Cerium oxide nanorods were uniformly grown on diverse substrates. • Changes in growth conditions led to morphology evolution of cerium oxide nanostructures. • The grown cerium oxide nanostructures were single or poly crystalline. • Direct growth of cerium oxide nanorods made the diverse substrates superhydrophobic and anti-corrosive without any surface modifiers. - Abstract: Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields

  11. Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo [School of Mechanical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Kim, Dong Rip, E-mail: dongrip@hanyang.ac.kr [School of Mechanical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of); Institute of Nano Science and Technology, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2015-06-15

    Graphical abstract: - Highlights: • Cerium oxide nanorods were uniformly grown on diverse substrates. • Changes in growth conditions led to morphology evolution of cerium oxide nanostructures. • The grown cerium oxide nanostructures were single or poly crystalline. • Direct growth of cerium oxide nanorods made the diverse substrates superhydrophobic and anti-corrosive without any surface modifiers. - Abstract: Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

  12. Fabrication of Cerium Oxide and Uranium Oxide Microspheres for Space Nuclear Power Applications

    Energy Technology Data Exchange (ETDEWEB)

    Jeffrey A. Katalenich; Michael R. Hartman; Robert C. O' Brien

    2013-02-01

    Cerium oxide and uranium oxide microspheres are being produced via an internal gelation sol-gel method to investigate alternative fabrication routes for space nuclear fuels. Depleted uranium and non-radioactive cerium are being utilized as surrogates for plutonium-238 (Pu-238) used in radioisotope thermoelectric generators and for enriched uranium required by nuclear thermal rockets. While current methods used to produce Pu-238 fuels at Los Alamos National Laboratory (LANL) involve the generation of fine powders that pose a respiratory hazard and have a propensity to contaminate glove boxes, the sol-gel route allows for the generation of oxide microsphere fuels through an aqueous route. The sol-gel method does not generate fine powders and may require fewer processing steps than the LANL method with less operator handling. High-quality cerium dioxide microspheres have been fabricated in the desired size range and equipment is being prepared to establish a uranium dioxide microsphere production capability.

  13. Altering properties of cerium oxide thin films by Rh doping

    International Nuclear Information System (INIS)

    Highlights: • Thin films of ceria doped by rhodium deposited by RF magnetron sputtering. • Concentration of rhodium has great impact on properties of Rh–CeOx thin films. • Intensive oxygen migration in films with low concentration of rhodium. • Oxygen migration suppressed in films with high amount of Rh dopants. - Abstract: Ceria containing highly dispersed ions of rhodium is a promising material for catalytic applications. The Rh–CeOx thin films with different concentrations of rhodium were deposited by RF magnetron sputtering and were studied by soft and hard X-ray photoelectron spectroscopies, Temperature programmed reaction and X-ray powder diffraction techniques. The sputtered films consist of rhodium–cerium mixed oxide where cerium exhibits a mixed valency of Ce4+ and Ce3+ and rhodium occurs in two oxidation states, Rh3+ and Rhn+. We show that the concentration of rhodium has a great influence on the chemical composition, structure and reducibility of the Rh–CeOx thin films. The films with low concentrations of rhodium are polycrystalline, while the films with higher amount of Rh dopants are amorphous. The morphology of the films strongly influences the mobility of oxygen in the material. Therefore, varying the concentration of rhodium in Rh–CeOx thin films leads to preparing materials with different properties

  14. Violet/blue emission from epitaxial cerium oxide films on silicon substrates

    International Nuclear Information System (INIS)

    Violet/blue photoluminescence was observed from epitaxial cerium oxide films on silicon substrates. The films were deposited on silicon (111) substrates under ultrahigh vacuum conditions using pulsed laser ablation of a cerium oxide target and treated by rapid thermal annealing in argon. High resolution transmission electron microscopy and x-ray diffraction measurements indicated the formation of a single crystal cerium oxide phase Ce6O11 different from CeO2 in the annealed films. The emission might be due to charge transfer transitions from the 4f band to the valence band of the oxide. copyright 1997 American Institute of Physics

  15. Structure and activity of tellurium-cerium oxide acrylonitrile catalysts

    International Nuclear Information System (INIS)

    Ammoxidation of propylene to acrylonitrile (ACN) was investigated over various silica-supported (Te,Ce)O catalysts at 360 and 4400C. The binary oxide system used consists of a single nonstoichiometric fluorite-type phase α-(Ce,Te)O2 up to about 80 mole% TeO2 and a tellurium-saturated solid solution β-(Ce,Te)O2 at higher tellurium concentrations. The ACN yield varies almost linearly with the tellurium content of (Ce,Te)O2. The β-(Ce,Te)O2 phase is the most active component of the system (propylene conversion and ACN selectivity at 440 C of 76.7 and 74%, respectively) and is slightly more selective to ACN than α-Te02. Tellurium reduces the overoxidation properties of cerium and selective oxidation occurs through Te(IV)-bonded oxygen

  16. Cerium fluoride nanoparticles protect cells against oxidative stress

    Energy Technology Data Exchange (ETDEWEB)

    Shcherbakov, Alexander B.; Zholobak, Nadezhda M. [Zabolotny Institute of Microbiology and Virology, National Academy of Sciences of Ukraine, Kyiv D0368 (Ukraine); Baranchikov, Alexander E. [Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); Ryabova, Anastasia V. [Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow 115409 (Russian Federation); Ivanov, Vladimir K., E-mail: van@igic.ras.ru [Kurnakov Institute of General and Inorganic Chemistry of the Russian Academy of Sciences, Moscow 119991 (Russian Federation); National Research Tomsk State University, Tomsk 634050 (Russian Federation)

    2015-05-01

    A novel facile method of non-doped and fluorescent terbium-doped cerium fluoride stable aqueous sols synthesis is proposed. Intense green luminescence of CeF{sub 3}:Tb nanoparticles can be used to visualize these nanoparticles' accumulation in cells using confocal laser scanning microscopy. Cerium fluoride nanoparticles are shown for the first time to protect both organic molecules and living cells from the oxidative action of hydrogen peroxide. Both non-doped and terbium-doped CeF{sub 3} nanoparticles are shown to provide noteworthy protection to cells against the vesicular stomatitis virus. - Highlights: • Facile method of CeF{sub 3} and CeF{sub 3}:Tb stable aqueous sols synthesis is proposed. • Naked CeF{sub 3} nanoparticles are shown to be non-toxic and to protect cells from the action of H{sub 2}O{sub 2}. • CeF{sub 3} and CeF{sub 3}:Tb nanoparticles are shown to protect living cells against the vesicular stomatitis virus.

  17. Cerium fluoride nanoparticles protect cells against oxidative stress

    International Nuclear Information System (INIS)

    A novel facile method of non-doped and fluorescent terbium-doped cerium fluoride stable aqueous sols synthesis is proposed. Intense green luminescence of CeF3:Tb nanoparticles can be used to visualize these nanoparticles' accumulation in cells using confocal laser scanning microscopy. Cerium fluoride nanoparticles are shown for the first time to protect both organic molecules and living cells from the oxidative action of hydrogen peroxide. Both non-doped and terbium-doped CeF3 nanoparticles are shown to provide noteworthy protection to cells against the vesicular stomatitis virus. - Highlights: • Facile method of CeF3 and CeF3:Tb stable aqueous sols synthesis is proposed. • Naked CeF3 nanoparticles are shown to be non-toxic and to protect cells from the action of H2O2. • CeF3 and CeF3:Tb nanoparticles are shown to protect living cells against the vesicular stomatitis virus

  18. The effect of cerium valence states at cerium oxide nanoparticle surfaces on cell proliferation

    KAUST Repository

    Naganuma, Tamaki

    2014-05-01

    Understanding and controlling cell proliferation on biomaterial surfaces is critical for scaffold/artificial-niche design in tissue engineering. The mechanism by which underlying integrin ligates with functionalized biomaterials to induce cell proliferation is still not completely understood. In this study, poly-l-lactide (PL) scaffold surfaces were functionalized using layers of cerium oxide nanoparticles (CNPs), which have recently attracted attention for use in therapeutic application due to their catalytic ability of Ce4+ and Ce3+ sites. To isolate the influence of Ce valance states of CNPs on cell proliferation, human mesenchymal stem cells (hMSCs) and osteoblast-like cells (MG63) were cultured on the PL/CNP surfaces with dominant Ce4+ and Ce3+ regions. Despite cell type (hMSCs and MG63 cells), different surface features of Ce4+ and Ce3+ regions clearly promoted and inhibited cell spreading, migration and adhesion behavior, resulting in rapid and slow cell proliferation, respectively. Cell proliferation results of various modified CNPs with different surface charge and hydrophobicity/hydrophilicity, indicate that Ce valence states closely correlated with the specific cell morphologies and cell-material interactions that trigger cell proliferation. This finding suggests that the cell-material interactions, which influence cell proliferation, may be controlled by introduction of metal elements with different valence states onto the biomaterial surface. © 2014 Elsevier Ltd.

  19. Effect of Surface Modification on Behaviors of Cerium Oxide Nanopowders

    Institute of Scientific and Technical Information of China (English)

    Li Mei; Shi Zhenxue; Liu Zhaogang; Hu Yanhong; Wang Mitang; Li Hangquan

    2007-01-01

    Study was made on the effect of surface modification on the behaviors of cerium oxide nanopowders. A surfactant-sodium dodecyl sulfate(C12H25SO4Na) was used to modify the surface of CeO2 powder particles. The unmodified and modified CeO2 powders were characterized by using a powder comprehensive characteristic tester, laser particle size analyzer, specific surface area tester, X-ray diffraction tester, and a scanning electron microscope. The testing and analysis results showed that C12H25SO4Na surface modification might increase the flowability and dispersity, and decrease the specific surface area and agglomeration of CeO2 powders. The mechanism of the surface modification of CeO2 powder particles was also discussed.

  20. Cerium oxide for the destruction of chemical warfare agents: A comparison of synthetic routes

    Czech Academy of Sciences Publication Activity Database

    Janos, P.; Henych, Jiří; Pelant, O.; Pilařová, V.; Vrtoch, L.; Kormunda, M.; Mazanec, K.; Štengl, Václav

    2016-01-01

    Roč. 304, MAR (2016), s. 259-268. ISSN 0304-3894 Institutional support: RVO:61388980 Keywords : Cerium oxide * Chemical warfare agents * Organophosphate compounds * Decontamination Subject RIV: CA - Inorganic Chemistry Impact factor: 4.529, year: 2014

  1. Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

    Science.gov (United States)

    Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo; Kim, Dong Rip

    2015-06-01

    Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

  2. Protein adsorption and cellular uptake of cerium oxide nanoparticles as a function of zeta potential

    OpenAIRE

    Patil, Swanand; Sandberg, Amanda; Heckert, Eric; Self, William; Seal, Sudipta

    2007-01-01

    The surface chemistry of biomaterials can have a significant impact on their performance in biological applications. Our recent work suggests that cerium oxide nanoparticles are potent antioxidants in cell culture models and we have evaluated several therapeutic applications of these nanoparticles in different biological systems. Knowledge of protein adsorption and cellular uptake will be very useful in improving the beneficial effects of cerium oxide nanoparticles in biology. In the present ...

  3. Effects of Morphology of Cerium Oxide Catalysts for Reverse Water Gas Shift Reaction

    OpenAIRE

    Kovasevic, M.; Mojet, B.L.; Ommen, van, B.; Lefferts, L.

    2016-01-01

    Reverse water gas shift reaction (RWGS) was investigated over cerium oxide catalysts of distinct morphologies: cubes, rods and particles. Catalysts were characterized by X-ray diffraction, Raman spectroscopy and temperature programmed reduction (TPR) in hydrogen. Nanoshapes with high concentration of oxygen vacancies contain less surface oxygen removable in TPR. Cerium oxide cubes exhibited two times higher activity per surface area as compared to rods and particles. Catalytic activity of the...

  4. Imidazolium ionic liquids as solvents for cerium(IV)-mediated oxidation reactions

    OpenAIRE

    Mehdi, Hasan; Bodor, Andrea; Lantos, Diana; Horváth, István T; De Vos, Dirk; Binnemans, Koen

    2007-01-01

    Use of imidazolium ionic liquids as solvents for organic transformations with tetravalent cerium salts as oxidizing agents was evaluated. Good solubility was found for ammonium hexanitratocerate(IV) (ceric ammonium nitrate, CAN) and cerium(IV) triflate in 1-alkyl-3-methylimidazolium triflate ionic liquids. Oxidation of benzyl alcohol to benzaldehyde in 1-ethyl-3-methylimidazolium triflate was studied by in-situ FTIR spectroscopy and 13C NMR spectroscopy on carbon-13-labeled benzyl alcohol. Ca...

  5. Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine

    Science.gov (United States)

    Nelson, Bryant C.; Johnson, Monique E.; Walker, Marlon L.; Riley, Kathryn R.; Sims, Christopher M.

    2016-01-01

    Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where our experimental understanding of the antioxidant activity of CNPs can be translated into useful therapeutics in the clinic, it is necessary to evaluate the most current evidence that supports CNP antioxidant activity in biological systems. Accordingly, the aims of this review are three-fold: (1) To describe the putative reaction mechanisms and physicochemical surface properties that enable CNPs to both scavenge reactive oxygen species (ROS) and to act as antioxidant enzyme-like mimetics in solution; (2) To provide an overview, with commentary, regarding the most robust design and synthesis pathways for preparing CNPs with catalytic antioxidant activity; (3) To provide the reader with the most up-to-date in vitro and in vivo experimental evidence supporting the ROS-scavenging potential of CNPs in biology and medicine. PMID:27196936

  6. Antioxidant Cerium Oxide Nanoparticles in Biology and Medicine.

    Science.gov (United States)

    Nelson, Bryant C; Johnson, Monique E; Walker, Marlon L; Riley, Kathryn R; Sims, Christopher M

    2016-01-01

    Previously, catalytic cerium oxide nanoparticles (CNPs, nanoceria, CeO2-x NPs) have been widely utilized for chemical mechanical planarization in the semiconductor industry and for reducing harmful emissions and improving fuel combustion efficiency in the automobile industry. Researchers are now harnessing the catalytic repertoire of CNPs to develop potential new treatment modalities for both oxidative- and nitrosative-stress induced disorders and diseases. In order to reach the point where our experimental understanding of the antioxidant activity of CNPs can be translated into useful therapeutics in the clinic, it is necessary to evaluate the most current evidence that supports CNP antioxidant activity in biological systems. Accordingly, the aims of this review are three-fold: (1) To describe the putative reaction mechanisms and physicochemical surface properties that enable CNPs to both scavenge reactive oxygen species (ROS) and to act as antioxidant enzyme-like mimetics in solution; (2) To provide an overview, with commentary, regarding the most robust design and synthesis pathways for preparing CNPs with catalytic antioxidant activity; (3) To provide the reader with the most up-to-date in vitro and in vivo experimental evidence supporting the ROS-scavenging potential of CNPs in biology and medicine. PMID:27196936

  7. Electronic interaction in oxide copper-cerium catalysts according to exoemission data

    International Nuclear Information System (INIS)

    The electronic properties of the oxide copper-cerium catalysts with different copper content are studied through the exoemission methods. It is shown, that the introduction of the copper increases the CeO2 emission activity and the number of the electrons, emitted from the catalysts surface, as compared to the surface of the CeO2 and CuO initial oxides. It is concluded, that the event of synergism in the exoemission from the studied systems surface is conditioned through the electronic interactions, including the electronic transitions on the cerium oxide - copper oxide boundary

  8. Synthesis and characterization of cerium oxide by electrochemical methods

    International Nuclear Information System (INIS)

    Ceria-based materials have been synthesized by electrochemical process. Electrodeposition is an interesting cheap method which can be performed at ambient pressure and rather low temperature (less than 100 C). Moreover, it is easy to control in situ the film thickness. Ceria coatings were obtained by an indirect electrodeposition method. A potentiostatic technique (-0.7 V/SCE) was used to first reduce a hydroxide precursor (O2 or NO3-) before leading to the formation of cerium oxide after 2h of deposition time. This work focused on the characterization of ceria films deposited onto stainless steel in view of high temperature fuel cell applications. The chosen deposition conditions lead to quite adherent, homogenous and covering films. The microstructure and the crystallinity of the ceria thin layers were characterized by SEM, TEM and XRD measurements. Electrochemical microscopy (SECM) was also used to locally study the conductive properties of ceria layers and the homogeneity of the deposited films. Finally, electrochemical characterizations such as impedance spectroscopy were performed under air atmosphere. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Synthesis and characterization of cerium oxide by electrochemical methods

    Energy Technology Data Exchange (ETDEWEB)

    Lair, V.; Ringuede, A. [LECA CNRS UMR 7575-ENSCP-Paris 6, Paris (France); Vermaut, P. [Groupe Metallurgie Structurale LPCS UMR CNRS, ENSCP-Paris 6, Paris (France); Griveau, S. [Ecole Nationale Superieure de Chimie de Paris, Faculty of Pharmacy, Chemical and Genetic Pharmacology Laboratory, Paris (France)

    2008-07-01

    Ceria-based materials have been synthesized by electrochemical process. Electrodeposition is an interesting cheap method which can be performed at ambient pressure and rather low temperature (less than 100 C). Moreover, it is easy to control in situ the film thickness. Ceria coatings were obtained by an indirect electrodeposition method. A potentiostatic technique (-0.7 V/SCE) was used to first reduce a hydroxide precursor (O{sub 2} or NO{sub 3}{sup -}) before leading to the formation of cerium oxide after 2h of deposition time. This work focused on the characterization of ceria films deposited onto stainless steel in view of high temperature fuel cell applications. The chosen deposition conditions lead to quite adherent, homogenous and covering films. The microstructure and the crystallinity of the ceria thin layers were characterized by SEM, TEM and XRD measurements. Electrochemical microscopy (SECM) was also used to locally study the conductive properties of ceria layers and the homogeneity of the deposited films. Finally, electrochemical characterizations such as impedance spectroscopy were performed under air atmosphere. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  10. Catalytic properties and biomedical applications of cerium oxide nanoparticles

    KAUST Repository

    Walkey, Carl D.

    2014-11-10

    Cerium oxide nanoparticles (nanoceria) have shown promise as catalytic antioxidants in the test tube, cell culture models and animal models of disease. However given the reactivity that is well established at the surface of these nanoparticles, the biological utilization of nanoceria as a therapeutic still poses many challenges. Moreover the form that these particles take in a biological environment, such as the changes that can occur due to a protein corona, are not well established. This review aims to summarize the existing literature on biological use of nanoceria, and to raise questions about what further study is needed to apply this interesting catalytic material to biomedical applications. These questions include: 1) How does preparation, exposure dose, route and experimental model influence the reported effects of nanoceria in animal studies? 2) What are the considerations to develop nanoceria as a therapeutic agent in regards to these parameters? 3) What biological targets of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are relevant to this targeting, and how do these properties also influence the safety of these nanomaterials?

  11. Characterization of microstructure and catalytic of cerium oxide obtained by colloidal solution

    International Nuclear Information System (INIS)

    This study investigated to obtain particles of cerium oxide, for use as catalysts for the combustion of methane using the technique of through polymeric colloidal solution. Obtaining the colloidal system is based on hydrolysis of salts such as cerium acetylacetonate, cerium nitrate in the presence of additives such as polyvinylbutyral (PVB), polyvinylpyrrolidone (PVP) and polyvinyl acetate (PVA), at concentrations of 5, 10 and 15% in aqueous or alcoholic medium. These solutions containing ions of interest were subjected to a heat treatment at 650° C for 30 minutes, with heating rate of 2 ° C/ min. After heat treatment, the fibers were characterized according to their morphology, surface area, crystallinity, weight loss and catalytic activity. Samples obtained from cerium acetylacetonate were more reactive than the cerium nitrate to the combustion of methane, as showed greater conversions and higher temperatures reached during the process, which is of utmost importance since the combustion catalytic methane is used for generating thermal energy. After the reaction with methane, the samples underwent significant change in surface area, probably due to the intensity of combustion reactions of the nitrate and the generation of heat involved in this reaction, which gave rise to coarse particles. During the combustion process using the obtained from particles of cerium acetylacetonate, there was the release of large quantities of nitrogen compared to the results of assays with the particles obtained with cerium nitrate. (author)

  12. Growth mode and oxidation state analysis of individual cerium oxide islands on Ru(0001)

    International Nuclear Information System (INIS)

    The growth of cerium oxide on Ru(0001) by reactive molecular beam epitaxy has been investigated using low-energy electron microscopy (LEEM) and diffraction as well as local valence band photoemission. The oxide islands are found to adopt a carpet-like growth mode, which depending on the local substrate morphology and misorientation leads to deviations from the otherwise almost perfect equilateral shape at a growth temperature of 850 °C. Furthermore, although even at this high growth temperature the micron-sized CeO2(111) islands are found to exhibit different lattice registries with respect to the hexagonal substrate, the combination of dark-field LEEM and local intensity-voltage analysis reveals that the oxidation state of the islands is homogeneous down to the 10 nm scale. - Highlights: • Cerium oxide is grown on ruthenium inside a low-energy electron microscope (LEEM). • The identified carpet growth mode is shown to determine the oxide island shape. • Intensity-voltage LEEM is demonstrated to be sensitive to oxidation state changes. • The oxidation state is found to be laterally homogeneous on the nanometer scale. • Ceria islands of the same oxidation state may have different substrate registries

  13. A corrosion resistant cerium oxide based coating on aluminum alloy 2024 prepared by brush plating

    International Nuclear Information System (INIS)

    Cerium oxide based coatings were prepared on AA2024 Al alloy by brush plating. The characteristic of this technology is that hydrogen peroxide, which usually causes the plating solution to be unstable, is not necessary in the plating electrolyte. The coating showed laminated structures and good adhesive strength with the substrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that the coatings were composed of Ce(III) and Ce(IV) oxides. The brush plated coatings on Al alloys improved corrosion resistance. The influence of plating parameters on structure and corrosion resistance of the cerium oxide based coating was studied.

  14. A corrosion resistant cerium oxide based coating on aluminum alloy 2024 prepared by brush plating

    Energy Technology Data Exchange (ETDEWEB)

    Tang Junlei; Han Zhongzhi [School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Zuo Yu, E-mail: zuoy@mail.buct.edu.cn [School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Tang Yuming [School of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

    2011-01-15

    Cerium oxide based coatings were prepared on AA2024 Al alloy by brush plating. The characteristic of this technology is that hydrogen peroxide, which usually causes the plating solution to be unstable, is not necessary in the plating electrolyte. The coating showed laminated structures and good adhesive strength with the substrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that the coatings were composed of Ce(III) and Ce(IV) oxides. The brush plated coatings on Al alloys improved corrosion resistance. The influence of plating parameters on structure and corrosion resistance of the cerium oxide based coating was studied.

  15. Soil organic matter influences cerium translocation and physiological processes in kidney bean plants exposed to cerium oxide nanoparticles.

    Science.gov (United States)

    Majumdar, Sanghamitra; Peralta-Videa, Jose R; Trujillo-Reyes, Jesica; Sun, Youping; Barrios, Ana C; Niu, Genhua; Margez, Juan P Flores-; Gardea-Torresdey, Jorge L

    2016-11-01

    Soil organic matter plays a major role in determining the fate of the engineered nanomaterials (ENMs) in the soil matrix and effects on the residing plants. In this study, kidney bean plants were grown in soils varying in organic matter content and amended with 0-500mg/kg cerium oxide nanoparticles (nano-CeO2) under greenhouse condition. After 52days of exposure, cerium accumulation in tissues, plant growth and physiological parameters including photosynthetic pigments (chlorophylls and carotenoids), net photosynthesis rate, transpiration rate, and stomatal conductance were recorded. Additionally, catalase and ascorbate peroxidase activities were measured to evaluate oxidative stress in the tissues. The translocation factor of cerium in the nano-CeO2 exposed plants grown in organic matter enriched soil (OMES) was twice as the plants grown in low organic matter soil (LOMS). Although the leaf cover area increased by 65-111% with increasing nano-CeO2 concentration in LOMS, the effect on the physiological processes were inconsequential. In OMES leaves, exposure to 62.5-250mg/kg nano-CeO2 led to an enhancement in the transpiration rate and stomatal conductance, but to a simultaneous decrease in carotenoid contents by 25-28%. Chlorophyll a in the OMES leaves also decreased by 27 and 18% on exposure to 125 and 250mg/kg nano-CeO2. In addition, catalase activity increased in LOMS stems, and ascorbate peroxidase increased in OMES leaves of nano-CeO2 exposed plants, with respect to control. Thus, this study provides clear evidence that the properties of the complex soil matrix play decisive roles in determining the fate, bioavailability, and biological transport of ENMs in the environment. PMID:27343939

  16. Effects of Cerium Oxide Nanoparticles on Sorghum Plant Traits

    Science.gov (United States)

    Mu, L.; Chen, Y.; Darnault, C. J. G.; Rauh, B.; Kresovich, S.; Korte, C.

    2015-12-01

    Nanotechnology and nanomaterials are considered as the development of the modern science. However, besides with that wide application, nanoparticles arouse to the side effects on the environment and human health. As the catalyst of ceramics and fuel industry, Cerium (IV) oxide nanoparticles (CeO2 NPs) can be found in the environment following their use and life-cycle. Therefore, it is critical to assess the potential effects that CeO2 NPs found in soils may have on plants. In this study, CeO2 NPs were analyzed for the potential influence on the sorghum [Sorghum bicolor (L.) Moench] (Reg. no. 126) (PI 154844) growth and traits. The objectives of this research were to determine whether CeO2 NPs impact the sorghum germination and growth characteristics. The sorghum was grown in the greenhouse located at Biosystems Research Complex, Clemson University under different CeO2 NPs treatments (0mg; 100mg; 500mg; 1000mg CeO2 NPs/Kg soil) and harvested around each month. At the end of the each growing period, above ground vegetative tissue was air-dried, ground to 2mm particle size and compositional traits estimated using near-infrared spectroscopy. Also, the NPK value of the sorghum tissue was tested by Clemson Agriculture Center. After the first harvest, the result showed that the height of above ground biomass under the nanoparticles stress was higher than that of control group. This difference between the control and the nanoparticles treatments was significant (F>F0.05; LSD). Our results also indicated that some of the compositional traits were impacted by the different treatments, including the presence and/or concentrations of the nanoparticles.

  17. Mesoporous cerium oxide nanospheres for the visible-light driven photocatalytic degradation of dyes

    Directory of Open Access Journals (Sweden)

    Subas K. Muduli

    2014-04-01

    Full Text Available A facile, solvothermal synthesis of mesoporous cerium oxide nanospheres is reported for the purpose of the photocatalytic degradation of organic dyes and future applications in sustainable energy research. The earth-abundant, relatively affordable, mixed valence cerium oxide sample, which consists of predominantly Ce7O12, has been characterized by powder X-ray diffraction, X-ray photoelectron and UV–vis spectroscopy, and transmission electron microscopy. Together with N2 sorption experiments, the data confirms that the new cerium oxide material is mesoporous and absorbs visible light. The photocatalytic degradation of rhodamin B is investigated with a series of radical scavengers, suggesting that the mechanism of photocatalytic activity under visible-light irradiation involves predominantly hydroxyl radicals as the active species.

  18. Environmental Geochemistry of Cerium: Applications and Toxicology of Cerium Oxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Jessica T. Dahle

    2015-01-01

    Full Text Available Cerium is the most abundant of rare-earth metals found in the Earth’s crust. Several Ce-carbonate, -phosphate, -silicate, and -(hydroxide minerals have been historically mined and processed for pharmaceutical uses and industrial applications. Of all Ce minerals, cerium dioxide has received much attention in the global nanotechnology market due to their useful applications for catalysts, fuel cells, and fuel additives. A recent mass flow modeling study predicted that a major source of CeO2 nanoparticles from industrial processing plants (e.g., electronics and optics manufactures is likely to reach the terrestrial environment such as landfills and soils. The environmental fate of CeO2 nanoparticles is highly dependent on its physcochemical properties in low temperature geochemical environment. Though there are needs in improving the analytical method in detecting/quantifying CeO2 nanoparticles in different environmental media, it is clear that aquatic and terrestrial organisms have been exposed to CeO2 NPs, potentially yielding in negative impact on human and ecosystem health. Interestingly, there has been contradicting reports about the toxicological effects of CeO2 nanoparticles, acting as either an antioxidant or reactive oxygen species production-inducing agent. This poses a challenge in future regulations for the CeO2 nanoparticle application and the risk assessment in the environment.

  19. Evaluation of Antiproliferative Potential of Cerium Oxide Nanoparticles on HeLa Human Cervical Tumor Cell

    Directory of Open Access Journals (Sweden)

    Zoriţa Diaconeasa

    2015-05-01

    Full Text Available Cerium oxide nanoparticles (CeO2 nanoparticles as nanomaterials have promising biomedical applications. In this paper, the cytotoxicity induced by CONPs human cervical tumor cells was investigated. Cerium oxide nanoparticles were synthesized using the precipitation method. The nanoparticles were found to inhibit the proliferation of HeLa human cervical tumor cells in a dose dependent manner but did not showed to be cytotoxic as analyzed by MTT assay. The administrated treatment decreased the HeLa cell viability cells from 100% to 65% at the dose of 100 μg/mL.

  20. Cerium Oxide Nanoparticles and Bulk Cerium Oxide Leading to Different Physiological and Biochemical Responses in Brassica rapa.

    Science.gov (United States)

    Ma, Xingmao; Wang, Qiang; Rossi, Lorenzo; Zhang, Weilan

    2016-07-01

    Cerium oxide nanoparticles (CeO2NPs) have been incorporated into many commercial products, and their potential release into the environment through the use and disposal of these products has caused serious concerns. Despite the previous efforts and rapid progress on elucidating the environmental impact of CeO2NPs, the long-term impact of CeO2NPs to plants, a key component of the ecosystem, is still not well understood. The potentially different impact of CeO2NPs and their bulk counterparts to plants is also unclear. The main objectives of this study were (1) to investigate whether continued irrigation with solutions containing different concentrations of CeO2NPs (0, 10, and 100 mg/L) would induce physiological and biochemical adjustments in Brassica rapa in soil growing conditions and (2) to determine whether CeO2NPs and bulk CeO2 particles exert different impacts on plants. The results indicated that bulk CeO2 at 10 and 100 mg/L enhanced plant biomass by 28% and 35%, respectively, while CeO2NPs at equivalent concentrations did not. While the bulk CeO2 treatment resulted in significantly higher concentrations of hydrogen peroxide (H2O2) in plant tissues at the vegetative stage, CeO2NPs led to significantly higher H2O2 levels in plant tissues at the floral stage. The activity of superoxide dismutase (SOD) in Brassica rapa also displayed a growth-stage dependent response to different sizes of CeO2 while catalase (CAT) activity was not affected by either size of CeO2 throughout the life cycle of Brassica rapa. Altogether, the results demonstrated that plant responses to CeO2 exposure varied with the particle sizes and the growth stages of plants. PMID:26691446

  1. Oxochloroalkoxide of the Cerium (IV and Titanium (IV as oxides precursor

    Directory of Open Access Journals (Sweden)

    Machado Luiz Carlos

    2002-01-01

    Full Text Available The Cerium (IV and Titanium (IV oxides mixture (CeO2-3TiO2 was prepared by thermal treatment of the oxochloroisopropoxide of Cerium (IV and Titanium (IV. The chemical route utilizing the Cerium (III chloride alcoholic complex and Titanium (IV isopropoxide is presented. The compound Ce5Ti15Cl16O30 (iOPr4(OH-Et15 was characterized by elemental analysis, FTIR and TG/DTG. The X-ray diffraction patterns of the oxides resulting from the thermal decomposition of the precursor at 1000 degreesC for 36 h indicated the formation of cubic cerianite (a = 5.417Å and tetragonal rutile (a = 4.592Å and (c = 2.962 Å, with apparent crystallite sizes around 38 and 55nm, respectively.

  2. Studies of solution deposited cerium oxide thin films on textured Ni-alloy substrates for YBCO superconductor

    International Nuclear Information System (INIS)

    Cerium oxide (CeO2) buffer layers play an important role for the development of YBa2Cu3O7-x (YBCO) based superconducting tapes using the rolling assisted biaxially textured substrates (RABiTS) approach. The chemical solution deposition (CSD) approach has been used to grow epitaxial CeO2 films on textured Ni-3 at.% W alloy substrates with various starting precursors of ceria. Precursors such as cerium acetate, cerium acetylacetonate, cerium 2-ethylhexanoate, cerium nitrate, and cerium trifluoroacetate were prepared in suitable solvents. The optimum growth conditions for these cerium precursors were Ar-4% H2 gas processing atmosphere, solution concentration levels of 0.2-0.5 M, a dwell time of 15 min, and a process temperature range of 1050-1150 deg. C. X-ray diffraction, AFM, SEM, and optical microscopy were used to characterize the CeO2 films. Highly textured CeO2 layers were obtained on Ni-W substrates with both cerium acetate and cerium acetylacetonate as starting precursors. YBCO films with a J c of 1.5 MA/cm2 were obtained on cerium acetylacetonate-based CeO2 films with sputtered YSZ and CeO2 cap layers

  3. Untangling the biological effects of cerium oxide nanoparticles: the role of surface valence states

    OpenAIRE

    Gerardo Pulido-Reyes; Ismael Rodea-Palomares; Soumen Das; Tamil Selvan Sakthivel; Francisco Leganes; Roberto Rosal; Sudipta Seal; Francisca Fernández-Piñas

    2015-01-01

    Cerium oxide nanoparticles (nanoceria; CNPs) have been found to have both pro-oxidant and anti-oxidant effects on different cell systems or organisms. In order to untangle the mechanisms which underlie the biological activity of nanoceria, we have studied the effect of five different CNPs on a model relevant aquatic microorganism. Neither shape, concentration, synthesis method, surface charge (ζ-potential), nor nominal size had any influence in the observed biological activity. The main drive...

  4. XPS and factor analysis study of initial stages of cerium oxide growth on polycrystalline tungsten

    Czech Academy of Sciences Publication Activity Database

    Polyak, Yaroslav; Bastl, Zdeněk

    2015-01-01

    Roč. 47, č. 6 (2015), s. 663-671. ISSN 0142-2421 Institutional support: RVO:68378271 ; RVO:61388955 Keywords : XPS * FA * PLD * cerium oxide * WO 3 * Ce (3d) Subject RIV: BM - Solid Matter Physics ; Magnetism; CF - Physical ; Theoretical Chemistry (UFCH-W) Impact factor: 1.245, year: 2014

  5. Influences of the main anodic electroplating parameters on cerium oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yang; Yang, Yumeng; Du, Xiaoqing; Chen, Yu [Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang (China); Zhang, Zhao, E-mail: eaglezzy@zjuem.zju.edu.cn [Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang (China); Zhang, Jianqing [Department of Chemistry, Zhejiang University, Hangzhou 310027, Zhejiang (China); State Key Laboratory for Corrosion and Protection of Metals, Shenyang 110016 (China)

    2014-06-01

    Cerium oxide thin films were fabricated onto 316 L stainless steel via a potentiostatically anodic electrodeposition approach in the solutions containing cerium(III) nitrate (0.05 M), ammonia acetate (0.1 M) and ethanol (10% V/V). The electrochemical behaviors and deposition parameters (applied potential, bath temperature, dissolving O{sub 2} and bath pH) have been investigated. Results show that, the electrochemical oxidation of Ce{sup 3+} goes through one electrochemical step, which is under charge transfer control. The optimum applied potential for film deposition is 0.8 V. Bath temperature plays a significant effect on the deposition rate, composition (different colors of the film) and surface morphology of the deposits. Due to the hydrolysis of Ce{sup 3+}, cerous hydroxide is facility to form when the bath temperature is higher than 60 °C. The electroplating bath pH is another key role for the anodic deposition of cerium oxide thin films, and the best bath pH is around 6.20. N{sub 2} or O{sub 2} purged into the bath will result in film porosities and O{sub 2} favors cerium oxide particles and film generation.

  6. Influences of the main anodic electroplating parameters on cerium oxide films

    International Nuclear Information System (INIS)

    Cerium oxide thin films were fabricated onto 316 L stainless steel via a potentiostatically anodic electrodeposition approach in the solutions containing cerium(III) nitrate (0.05 M), ammonia acetate (0.1 M) and ethanol (10% V/V). The electrochemical behaviors and deposition parameters (applied potential, bath temperature, dissolving O2 and bath pH) have been investigated. Results show that, the electrochemical oxidation of Ce3+ goes through one electrochemical step, which is under charge transfer control. The optimum applied potential for film deposition is 0.8 V. Bath temperature plays a significant effect on the deposition rate, composition (different colors of the film) and surface morphology of the deposits. Due to the hydrolysis of Ce3+, cerous hydroxide is facility to form when the bath temperature is higher than 60 °C. The electroplating bath pH is another key role for the anodic deposition of cerium oxide thin films, and the best bath pH is around 6.20. N2 or O2 purged into the bath will result in film porosities and O2 favors cerium oxide particles and film generation.

  7. Influences of the main anodic electroplating parameters on cerium oxide films

    Science.gov (United States)

    Yang, Yang; Yang, Yumeng; Du, Xiaoqing; Chen, Yu; Zhang, Zhao; Zhang, Jianqing

    2014-06-01

    Cerium oxide thin films were fabricated onto 316 L stainless steel via a potentiostatically anodic electrodeposition approach in the solutions containing cerium(III) nitrate (0.05 M), ammonia acetate (0.1 M) and ethanol (10% V/V). The electrochemical behaviors and deposition parameters (applied potential, bath temperature, dissolving O2 and bath pH) have been investigated. Results show that, the electrochemical oxidation of Ce3+ goes through one electrochemical step, which is under charge transfer control. The optimum applied potential for film deposition is 0.8 V. Bath temperature plays a significant effect on the deposition rate, composition (different colors of the film) and surface morphology of the deposits. Due to the hydrolysis of Ce3+, cerous hydroxide is facility to form when the bath temperature is higher than 60 °C. The electroplating bath pH is another key role for the anodic deposition of cerium oxide thin films, and the best bath pH is around 6.20. N2 or O2 purged into the bath will result in film porosities and O2 favors cerium oxide particles and film generation.

  8. Cerium oxide nanoparticles inhibit lipopolysaccharide induced MAP kinase/NF-kB mediated severe sepsis

    Directory of Open Access Journals (Sweden)

    Vellaisamy Selvaraj

    2015-09-01

    Full Text Available The life threatening disease of sepsis is associated with high mortality. Septic patient survivability with currently available treatments has failed to improve. The purpose of this study was to evaluate whether lipopolysaccharide (LPS induced sepsis mortality and associated hepatic dysfunction can be prevented by cerium oxide nanoparticles (CeO2NPs treatment in male Sprague Dawley rats. Here we provide the information about the methods processing of raw data related to our study published in Biomaterials (Selvaraj et al., Biomaterials, 2015, In press and Data in Brief (Selvaraj et al., Data in Brief, 2015, In Press. The data present here provides confirmation of cerium oxide nanoparticle treatments ability to prevent the LPS induced sepsis associated changes in physiological, blood cell count, inflammatory protein and growth factors in vivo. In vitro assays investigation the treated of macrophages cells with different concentrations of cerium oxide nanoparticle demonstrate that concentration of cerium oxide nanoparticles below 1 µg/ml did not significantly influence cell survival as determined by the MTT assay.

  9. Cerium oxide nanoparticles inhibit lipopolysaccharide induced MAP kinase/NF-kB mediated severe sepsis.

    Science.gov (United States)

    Selvaraj, Vellaisamy; Nepal, Niraj; Rogers, Steven; Manne, Nandini D P K; Arvapalli, Ravikumar; Rice, Kevin M; Asano, Shinichi; Fankenhanel, Erin; Ma, J Y; Shokuhfar, Tolou; Maheshwari, Mani; Blough, Eric R

    2015-09-01

    The life threatening disease of sepsis is associated with high mortality. Septic patient survivability with currently available treatments has failed to improve. The purpose of this study was to evaluate whether lipopolysaccharide (LPS) induced sepsis mortality and associated hepatic dysfunction can be prevented by cerium oxide nanoparticles (CeO2NPs) treatment in male Sprague Dawley rats. Here we provide the information about the methods processing of raw data related to our study published in Biomaterials (Selvaraj et al., Biomaterials, 2015, In press) and Data in Brief (Selvaraj et al., Data in Brief, 2015, In Press). The data present here provides confirmation of cerium oxide nanoparticle treatments ability to prevent the LPS induced sepsis associated changes in physiological, blood cell count, inflammatory protein and growth factors in vivo. In vitro assays investigation the treated of macrophages cells with different concentrations of cerium oxide nanoparticle demonstrate that concentration of cerium oxide nanoparticles below 1 µg/ml did not significantly influence cell survival as determined by the MTT assay. PMID:26217772

  10. Phenotypic and genomic responses to titanium dioxide and cerium oxide nanoparticles in Arabidopsis germinants

    Science.gov (United States)

    The effects of exposure to two nanoparticles (NPs) -titanium dioxide (nano-titania) and cerium oxide (nano-ceria) at 500 mg NPs L-1 on gene expression and growth in Arabidopsis thaliana germinants were studied using microarrays and phenotype studies. After 12 days post treatment,...

  11. Photocatalytic action of cerium molybdate and iron-titanium oxide hollow nanospheres on Escherichia coli

    International Nuclear Information System (INIS)

    This study is focused on the production of hollow nanospheres that reveal antibacterial action. Cerium molybdate and iron-titanium oxide hollow nanospheres with a diameter of 175 ± 15 and 221 ± 10 nm, respectively, were synthesized using emulsion polymerization and the sol–gel process. Their morphology characterization was accomplished using scanning electron microscopy. Their antibacterial action was examined on pure culture of Escherichia coli considering the loss of their viability. Both hollow nanospheres presented photocatalytic action after illumination with blue–black light, but those of cerium molybdate also demonstrated photocatalytic action in the dark. Therefore, the produced nanospheres can be used for antibacterial applications.

  12. Synthesis and catalytic properties of microemulsion-derived cerium oxide nanoparticles

    Science.gov (United States)

    Kockrick, Emanuel; Schrage, Christian; Grigas, Anett; Geiger, Dorin; Kaskel, Stefan

    2008-07-01

    The synthesis of cerium dioxide nanoparticles using an inverse microemulsion technique and precipitation method was investigated. Cerium hydroxide nanoparticles were synthesized by adding diluted ammonia to n-heptane-surfactant-cerium nitrate system. The micelle and particle size in the range of 5-12 nm were controlled by varying the molar water to surfactant ratio and analyzed by dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM). Cerium hydroxide nanoparticles were isolated and subsequently treated at 100-600 °C to obtain nanoscale ceria. Crystallite sizes of cerium dioxide in the range of 6-16 nm were estimated by Scherrer analysis by X-ray diffraction (XRD) and HRTEM. The catalytic activity of particles annealed at 400 and 600 °C in soot combustion reactions was characterized by temperature-programmed oxidation (TPO) indicating a size-dependant activity. Crystallite sizes and catalytic stability of elevated ceria systems were tested in second combustion cycles.

  13. Oxidation behaviour and electrical properties of cobalt/cerium oxide composite coatings for solid oxide fuel cell interconnects

    DEFF Research Database (Denmark)

    Harthøj, Anders; Holt, Tobias; Møller, Per

    2015-01-01

    This work evaluates the performance of cobalt/cerium oxide (Co/CeO2) composite coatings and pure Co coatings to be used for solid oxide fuel cell (SOFC) interconnects. The coatings are electroplated on the ferritic stainless steels Crofer 22 APU and Crofer 22H. Coated and uncoated samples....... The ASR of all Crofer 22H samples increased significantly faster than of Crofer 22 APU samples which was likely due to the presence of SiO2 in the oxide/metal interface of Crofer 22H....

  14. Investigation of the Carbon Monoxide Gas Sensing Characteristics of Tin Oxide Mixed Cerium Oxide Thin Films

    Directory of Open Access Journals (Sweden)

    Muhammad B. Haider

    2012-02-01

    Full Text Available Thin films of tin oxide mixed cerium oxide were grown on unheated substrates by physical vapor deposition. The films were annealed in air at 500 °C for two hours, and were characterized using X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. X-ray photoelectron spectroscopy and atomic force microscopy results reveal that the films were highly porous and porosity of our films was found to be in the range of 11.6–21.7%. The films were investigated for the detection of carbon monoxide, and were found to be highly sensitive. We found that 430 °C was the optimum operating temperature for sensing CO gas at concentrations as low as 5 ppm. Our sensors exhibited fast response and recovery times of 26 s and 30 s, respectively.

  15. Catalytic performance of cerium iron complex oxides for partial oxidation of methane to synthesis gas

    Institute of Scientific and Technical Information of China (English)

    LI Kongzhai; WANG Hua; WEI Yonggang; LIU Mingchun

    2008-01-01

    The cerium iron complex oxides oxygen carder was prepared by the co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carrier could be re-oxidized by air and its initial state could be restored. The characterizations of the oxygen carriers were studied using XRD, O2-TPD, and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for the partial oxidation of methane to synthesis gas. There were two kinds of oxygen species on the oxygen carder: the stronger oxygen species that was responsible for the complete oxidation of methane, and the weaker oxygen species (bulk lattice oxygen) that was responsible for the selective oxidation of methane to CO and H2 at a higher temperature. Then, the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction con-dition. CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles, however, it was not bad for the selectivity of CO and H2.

  16. Theoretical modeling of heterogeneous catalysts based on platinum and cerium oxide

    OpenAIRE

    Bruix Fusté, Albert

    2014-01-01

    This thesis focuses on the computational study of models for platinum catalysts supported on cerium oxide (CeO2) which are of technological relevance. In these catalysts, ceria is often found acting as a non-inert support, leading to complex metal-support interactions (MSI) that modify the properties of both the oxide and the supported metal. First principles computational methods based on the Density functional Theory (DFT) have been used to study the nature of these interactions and their e...

  17. Redox-active cerium oxide nanoparticles protect human dermal fibroblasts from PQ-induced damage

    OpenAIRE

    Claudia von Montfort; Lirija Alili; Sarah Teuber-Hanselmann; Peter Brenneisen

    2014-01-01

    Recently, it has been published that cerium (Ce) oxide nanoparticles (CNP; nanoceria) are able to downregulate tumor invasion in cancer cell lines. Redox-active CNP exhibit both selective pro-oxidative and antioxidative properties, the first being responsible for impairment of tumor growth and invasion. A non-toxic and even protective effect of CNP in human dermal fibroblasts (HDF) has already been observed. However, the effect on important parameters such as cell death, proliferation and red...

  18. Exposure of cerium oxide nanoparticles to kidney bean shows disturbance in the plant defense mechanisms

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Kidney bean roots uptake nCeO2 primarily without biotransformation. • Cerium reached the root vascular tissues through gaps in the Casparian strip. • On longer exposure to high concentration, roots demonstrate stress response. • In leaves, guaiacol peroxidase plays a major role in ROS scavenging. - Abstract: Overwhelming use of engineered nanoparticles demands rapid assessment of their environmental impacts. The transport of cerium oxide nanoparticles (nCeO2) in plants and their impact on cellular homeostasis as a function of exposure duration is not well understood. In this study, kidney bean plants were exposed to suspensions of ∼8 ± 1 nm nCeO2 (62.5 to 500 mg/L) for 15 days in hydroponic conditions. Plant parts were analyzed for cerium accumulation after one, seven, and 15 days of nCeO2 exposure. The primary indicators of stress like lipid peroxidation, antioxidant enzyme activities, total soluble protein and chlorophyll contents were studied. Cerium in tissues was localized using scanning electron microscopy and synchrotron μ-XRF mapping, and the chemical forms were identified using μ-XANES. In the root epidermis, cerium was primarily shown to exist as nCeO2, although a small fraction (12%) was biotransformed to Ce(III) compound. Cerium was found to reach the root vascular tissues and translocate to aerial parts with time. Upon prolonged exposure to 500 mg nCeO2/L, the root antioxidant enzyme activities were significantly reduced, simultaneously increasing the root soluble protein by 204%. In addition, leaf's guaiacol peroxidase activity was enhanced with nCeO2 exposure in order to maintain cellular homeostasis

  19. Exposure of cerium oxide nanoparticles to kidney bean shows disturbance in the plant defense mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, Sanghamitra [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Peralta-Videa, Jose R. [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Bandyopadhyay, Susmita [Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Castillo-Michel, Hiram [European Synchrotron Radiation Facility, B.P. 220-38043 Grenoble, Cedex (France); Hernandez-Viezcas, Jose-Angel [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States); Sahi, Shivendra [Department of Biology, Western Kentucky University, Bowling Green, KY 42101 (United States); Gardea-Torresdey, Jorge L., E-mail: jgardea@utep.edu [Department of Chemistry, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); Environmental Science and Engineering PhD Program, The University of Texas at El Paso, 500 West University Ave., El Paso, TX 79968 (United States); University of California Center for Environmental Implications of Nanotechnology (UC CEIN) (United States)

    2014-08-15

    Graphical abstract: - Highlights: • Kidney bean roots uptake nCeO{sub 2} primarily without biotransformation. • Cerium reached the root vascular tissues through gaps in the Casparian strip. • On longer exposure to high concentration, roots demonstrate stress response. • In leaves, guaiacol peroxidase plays a major role in ROS scavenging. - Abstract: Overwhelming use of engineered nanoparticles demands rapid assessment of their environmental impacts. The transport of cerium oxide nanoparticles (nCeO{sub 2}) in plants and their impact on cellular homeostasis as a function of exposure duration is not well understood. In this study, kidney bean plants were exposed to suspensions of ∼8 ± 1 nm nCeO{sub 2} (62.5 to 500 mg/L) for 15 days in hydroponic conditions. Plant parts were analyzed for cerium accumulation after one, seven, and 15 days of nCeO{sub 2} exposure. The primary indicators of stress like lipid peroxidation, antioxidant enzyme activities, total soluble protein and chlorophyll contents were studied. Cerium in tissues was localized using scanning electron microscopy and synchrotron μ-XRF mapping, and the chemical forms were identified using μ-XANES. In the root epidermis, cerium was primarily shown to exist as nCeO{sub 2}, although a small fraction (12%) was biotransformed to Ce(III) compound. Cerium was found to reach the root vascular tissues and translocate to aerial parts with time. Upon prolonged exposure to 500 mg nCeO{sub 2}/L, the root antioxidant enzyme activities were significantly reduced, simultaneously increasing the root soluble protein by 204%. In addition, leaf's guaiacol peroxidase activity was enhanced with nCeO{sub 2} exposure in order to maintain cellular homeostasis.

  20. Shifts in oxidation states of cerium oxide nanoparticles detected inside intact hydrated cells and organelles

    Energy Technology Data Exchange (ETDEWEB)

    Szymanski, Craig J.; Munusamy, Prabhakaran; Mihai, Cosmin; Xie, Yumei; Hu, Dehong; Gilles, Marry K.; Tyliszczak, T.; Thevuthasan, Suntharampillai; Baer, Donald R.; Orr, Galya

    2015-09-01

    Cerium oxide nanoparticles (CNPs) have been shown to induce diverse biological effects, ranging from toxic to beneficial. The beneficial effects have been attributed to the potential antioxidant activity of CNPs via certain redox reactions, depending on their oxidation state or Ce3+/Ce4+ ratio. However, this ratio is strongly dependent on the environment and age of the nanoparticles and it is unclear whether and how the complex intracellular environment impacts this ratio and the possible redox reactions of CNPs. To identify any changes in the oxidation state of CNPs in the intracellular environment and better understand their intracellular reactions, we directly quantified the oxidation states of CNPs outside and inside intact hydrated cells and organelles using correlated scanning transmission x-ray and super resolution fluorescence microscopies. By analyzing hundreds of small CNP aggregates, we detected a shift to a higher Ce3+/Ce4+ ratio in CNPs inside versus outside the cells, indicating a net reduction of CNPs in the intracellular environment. We further found a similar ratio in the cytoplasm and in the lysosomes, indicating that the net reduction occurs earlier in the internalization pathway. Together with oxidative stress and toxicity measurements, our observations identify a net reduction of CNPs in the intracellular environment, which is consistent with their involvement in potentially beneficial oxidation reactions, but also point to interactions that can negatively impact the health of cells.

  1. Radioluminescence and phosphororescence in electron-tube glasses doped with tin and cerium oxides

    International Nuclear Information System (INIS)

    Cerium and tin additions effect upon radioluminescence and phosphorescence of glasses (basic components are: SiO2, Al2O-3, ZnO, B2O3, Na2O, K2O) exposed to gamma radiation is studied. It has been shown that the following small amounts of CeO2 and SnO2 additions cause a considerable change in radioluminescence (2 times) and phosphorescence (more than an order). Tin oxide concentration increase results in radioluminescence growth in the short-wave spectral region. The dependence of radioluminescence and phosphorescence on cerium oxide concentration as well as the dependence of phosphorescence on tin oxide concentration has its maximum at 0.5-0.7 mass% of these additions. Radiation and optical characteristics of the glass under study have been compared to those of industrial glasses

  2. Thermal Property Evaluation of Cerium Dioxide and Cerium Dioxide Magnesium Oxide Powders for Testing Plutonium

    International Nuclear Information System (INIS)

    Ceric oxide (CeO2) and mixtures of CeO2 -magnesium oxide (MgO) have been utilized at the Plutonium Finishing Plant (PFP) as surrogate materials to represent plutonium dioxide (PuO2) and impure PuO2 containing impurities such as MgO during verification tests on PFP's stabilization furnaces. Magnesium oxide was selected during furnace testing as the impurity of interest since much of the impure PuO2 to be stabilized and packaged at the PFP contains significant amounts of MgO from solution stabilization work. The issue being addressed in this study is whether or not heating the surrogate materials to 950 C adequately simulates heating PuO2 powders to 950 C. This paper evaluates some of the thermal properties of these oxides, as related to the heating of powders of these materials where heat transfer within the powders is governed primarily by conduction. Detailed heat transfer modeling was outside the scope of this paper

  3. Development of Stable Cerium Zirconium Mixed Oxide Nanoparticle Additive for Emission Reduction in Biodiesel Blends

    Directory of Open Access Journals (Sweden)

    Sajith V

    2015-06-01

    Full Text Available Harmful emissions associated with the use of biodiesel is a serious issue and various fuel additives are being used for the reduction of emissions as well as for the improvement of engine performance. Use of cerium oxide nanoparticles as fuel additive is one of the methods for the reduction of emissions, due to its peculiar redox functionality and oxygen buffering capability. Doping of ceria with transition metals such as zirconium improves its Oxygen storage capacity and thermal stability, thereby enhancing simultaneous oxidation and reduction reactions. The present work focuses on the development of cerium zirconium mixed oxide nanoparticle based additive for the reduction of emissions from diesel engine fuelled with biodiesel - diesel blends. Cerium zirconium mixed oxide was synthesized by means of co precipitation method. The stability of the nanofluids was improved by the addition of surfactant, namely Oleic acid. The optimum concentration of surfactant was determined based on estimation of critical micelle concentration, by means of standard tests. Stability of catalytic nanoparticle in fuel was evaluated from the measurement of Zeta potential. Various properties were determined as per ASTM standards to investigate the effect of the nanoparticles on fuel properties. Addition of catalytic nanoparticle in diesel - biodiesel blends does not significantly affect the fuel properties. Engine performance and emission tests were conducted on single cylinder diesel engine to assess the potential of synthesized nanofuel and 15% average reduction of NO emissions was observed for B5 and B10 blends with 15 ppm of catalytic nanoparticle concentration.

  4. Synthesis of mesoporous cerium-zirconium mixed oxides by hydrothermal templating method

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Mesoporous cerium-zirconium mixed oxides were prepared by hydrothermal method using cetyl trimethyl ammonium bromide (CTAB) as template.The effects of amount of template,pH value of solution and hydrothermal temperature on mesostructure of samples were systematically investigated.The final products were characterized by XRD,TEM,FT-IR,and BET.The results indicate that all the cerium-zirconium mixed oxides present a meso-structure.At molar ratio of n(CTAB)/n((Ce)+(Zr))=0.15,pH value of 9,and hydrothermal temperature of 120 ℃,the samples obtained possess a specific surface area of 207.9 m2/g with pore diameter of 3.70 nm and pore volume of 0.19 cm3/g.

  5. Monte Carlo radiative transfer simulation of a cavity solar reactor for the reduction of cerium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Villafan-Vidales, H.I.; Arancibia-Bulnes, C.A.; Dehesa-Carrasco, U. [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Privada Xochicalco s/n, Col. Centro, A.P. 34, Temixco, Morelos 62580 (Mexico); Romero-Paredes, H. [Departamento de Ingenieria de Procesos e Hidraulica, Universidad Autonoma Metropolitana-Iztapalapa, Av. San Rafael Atlixco No.186, Col. Vicentina, A.P. 55-534, Mexico D.F 09340 (Mexico)

    2009-01-15

    Radiative heat transfer in a solar thermochemical reactor for the thermal reduction of cerium oxide is simulated with the Monte Carlo method. The directional characteristics and the power distribution of the concentrated solar radiation that enters the cavity is obtained by carrying out a Monte Carlo ray tracing of a paraboloidal concentrator. It is considered that the reactor contains a gas/particle suspension directly exposed to concentrated solar radiation. The suspension is treated as a non-isothermal, non-gray, absorbing, emitting, and anisotropically scattering medium. The transport coefficients of the particles are obtained from Mie-scattering theory by using the optical properties of cerium oxide. From the simulations, the aperture radius and the particle concentration were optimized to match the characteristics of the considered concentrator. (author)

  6. Effect of cerium oxide addition on electrical and physical properties of alkali borosilicate glasses

    International Nuclear Information System (INIS)

    The study of electrical conductivity, density and coefficient of thermal expansion (CTE) of Na2O:K2O:B2O3:SiO2:BaO glass samples with addition of cerium oxide has been carried out. It has been observed that the addition of cerium oxide affects the electrical conductivity, density and CTE. The results have been explained on the basis of the variation in number of bridging oxygens (BOs) and non-bridging oxygens (NBOs) present in the glass. In general, the glass with more NBOs has a weak network which exhibits higher electrical conductivity. The weakening of the network has been supported by the observed decrease in density and increase in CTE for the glasses.

  7. Effects of cerium oxide supplementation to laying hen diets on performance, egg quality, some antioxidant enzymes in serum and lipid oxidation in egg yolk.

    Science.gov (United States)

    Bölükbaşı, S C; Al-Sagan, A A; Ürüşan, H; Erhan, M K; Durmuş, O; Kurt, N

    2016-08-01

    This study was conducted to determine the effects of dietary cerium oxide levels (0, 100, 200, 300 or 400 mg/kg) on the laying performance, egg quality, some blood serum parameters and egg lipid peroxidation of laying hen. In total, one hundred and twenty 22-week-old brown Lohman LSL laying hens were randomly assigned to five groups equally (n = 24). Each treatment was replicated six times. Dietary supplementation of cerium oxide had no significant effect on feed intake and egg weight. The addition of cerium oxide to the laying hens' feed improved feed conversion ratio and increased (p laying hens feed led to a significant (p hen diets. It was also observed that serum superoxide dismutase (SOD) activity and malondialdehyde (MDA) concentration decreased significantly with supplementation of cerium oxide in diets. Inclusion of cerium oxide resulted in a significant reduction in thiobarbituric acid reactive substance (TBARS) values in egg yolk in this study. It can be concluded that the addition of cerium oxide had positive effects on egg production, feed conversion ratio and egg shelf life. Based on the results of this study, it could be advised to supplement laying hens feed with cerium oxide as feed additives. PMID:26847677

  8. One step hydrothermal synthesis of a carbon nanotube/cerium oxide nanocomposite and its electrochemical properties

    Science.gov (United States)

    Kalubarme, Ramchandra S.; Kim, Yong-Han; Park, Chan-Jin

    2013-09-01

    A carbon nanotube (CNT)/cerium oxide composite was prepared by a one-pot hydrothermal reaction in the presence of KOH and capping agent polyvinylpyrrolidone. The nanocomposite displayed pronounced capacitive behaviour with very small diffusion resistance. The electrochemical performance of the composite electrode in a symmetric supercapacitor displayed a high energy density of 35.9 Wh kg-1 corresponding to a specific capacitance of 289 F g-1. These composite electrodes also demonstrated a long cycle life with better capacity retention.

  9. Laser ablated plasma plume diagnostics of cerium oxide: effect of oxygen partial pressure

    International Nuclear Information System (INIS)

    This paper describes the spatial and temporal investigation of laser ablated plasma plume of cerium oxide target using Langmuir probe to measure the plasma parameters. Cerium oxide target was ablated using a KrF (λ ∼ 248 nm) gas laser at an energy of 300 mJ per pulse. Experimental studies confirmed that oxygen partial pressure of 2 x 10-2 mbar is sufficient enough to get good quality films of cerium oxide. At this pressure, plume was diagnosed for their spatial and temporal behaviour. The tungsten probe tip was inserted along the length of the plasma to collect the ions and electrons effectively. A thin probe tip (about 0.4 mm diameter) was used to avoid plasma perturbation during measurements. A variable voltage was applied to the tip and corresponding current due to electrons and ions was collected. Spatial distribution was investigated at a regular interval of 15 mm from the target up maximum distance 45 mm and the temporal behaviour was recorded in the range of 0 to 50 μS with an interval of 0.5 μS. The ion and average electron density are found to be maximum at 30 mm from the target position and the plasma current of ceria is found to be maximum at 22 μS. (author)

  10. Sol-gel derived cerium-oxide-silicon-oxide nanocomposite for cypermethrin detection

    International Nuclear Information System (INIS)

    Cerium oxide (CeO2) nanoparticles have been self-assembled onto sol-gel derived silicon-oxide (SiO2) film fabricated onto indium tin oxide (ITO) coated glass plate. These SiO2-CeO2 nanocomposite films have been used to immobilize the double stranded calf thymus deoxy ribose nucleic acid (dsCT-DNA) by physical adsorption to detect cypermethrin (CM). Both CeO2-SiO2/ITO electrode and dsCT-DNA/CeO2-SiO2/ITO bioelectrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microsopy (SEM) and differential pulse voltammetry (DPV) to confirm the formation of CeO2-SiO2 nanocomposite and binding of dsCT-DNA with CeO2-SiO2 nanocomposite. Electrochemical response studies of dsCT-DNA/CeO2-SiO2/ITO bioelectrode carried out as a function of CM concentration using DPV technique exhibit detection limit up to 0.0025 ppm with response time of 30 s.

  11. Oxidation behaviour and electrical properties of cobalt/cerium oxide composite coatings for solid oxide fuel cell interconnects

    Science.gov (United States)

    Harthøj, Anders; Holt, Tobias; Møller, Per

    2015-05-01

    This work evaluates the performance of cobalt/cerium oxide (Co/CeO2) composite coatings and pure Co coatings to be used for solid oxide fuel cell (SOFC) interconnects. The coatings are electroplated on the ferritic stainless steels Crofer 22 APU and Crofer 22H. Coated and uncoated samples are exposed in air at 800 °C for 3000 h and oxidation rates are measured and oxide scale microstructures are investigated. Area-specific resistances (ASR) in air at 850 °C of coated and uncoated samples are also measured. A dual layered oxide scale formed on all coated samples. The outer layer consisted of Co, Mn, Fe and Cr oxide and the inner layer consisted of Cr oxide. The CeO2 was present as discrete particles in the outer oxide layer after exposure. The Cr oxide layer thicknesses and oxidations rates were significantly reduced for Co/CeO2 coated samples compared to for Co coated and uncoated samples. The ASR of all Crofer 22H samples increased significantly faster than of Crofer 22 APU samples which was likely due to the presence of SiO2 in the oxide/metal interface of Crofer 22H.

  12. High temperature stability of a 316 austenitic stainless steel coated with cerium oxide nanoparticles

    Science.gov (United States)

    Mendoza Del Angel, Humberto

    Cerium oxide (CeO2-x) nanoparticles were used for coating protection on a 316 Austenitic Stainless Steel (Aust. SS) to enhance the thermal stability of the oxide films formed at high temperatures. Three simple coating methods were used, dipping, spraying and spinning in order to explore the coating film morphology, nanoparticle distribution and its effect on thermal stability of the steel substrates. Experimentally, the selected steel was exposed to 800°C/1000°C under dry air conditions. Weight changes (DeltaW/A) were monitored as a function of time and the results were compared with uncoated alloys tested under similar conditions. The cerium oxide nanoparticles used on the three methods were synthesized in the laboratory obtaining nanoparticles in the range of 3.5 to 6.2 nanometers. It was found that cerium oxide particle size is affected by temperature. In this case, the activation energy for particle growth was estimated to be around 21,1 kJ/mol. Characterization of the film morphologies before and after oxidation were carried out using Atomic Force Microscopy (AFM), Surface Profilometry, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). A comparison of the three coating methods was carried out for the particular case of the 316 Aust. SS coupons. In addition, the oxidation kinetics was experimentally investigated for the coated samples. For this purpose thermal gravimetric determinations were made at 800°C, 900°C, and 1000°C and oxidation rate constants were calculated at each temperature.

  13. Effect of cerium oxide addition on electrical properties of ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, D.M. [National Research Center, Dokki, Giza (Egypt). Dept. of Ceramics; Mounir, M. [Dept. of Physics, Cairo Univ., Giza (Egypt); Mahgoub, A.S. [Cairo Univ., Giza (Egypt). Dept. of Chemistry; Turky, G. [Dept. of Physics, National Research Center, Dokki, Giza (Egypt); El-Desouky, O.A. [Cer. Cleopatra Co., Ramadan City (Egypt)

    2002-07-01

    Mixtures of ZnO and Ce{sub 6} O{sub 11} as additive were prepared by solid state reaction from the calcined oxides with the following proportions: 0.03, 0.08, 0.1, 0.2 and 0.4 mole. Disc specimens 1.2 cm 5 cm in diameter and 0.3 cm thickness were processed under a force of 70 kN and fired at 1150 C/ 30 minutes. XRD revealed the presence of limited solid solution of cerium in ZnO, as evident from the shift in the peaks [0.03-0.04 A ] up to 0.1 mole addition and remains constant. SEM revealed the presence of inter-granular phase. EDAX showed it to be a mixture of ZnO and Ce{sub 6}O{sub 11}. Also cerium was detected in the ZnO grains confirming the XRD results. RCL circuit was used to measure the capacitance and resistance at different frequencies at room temperature. The dielectric constant and conductivity were calculated. The change in resistivity with temperature was followed up to 523 K. The change in dielectric strength with temperature at spot frequency of 10 kHz is demonstrated. The electrical conductivity was found to increase with the proportion of cerium oxide up to 0.2 mole then decreased. (orig.)

  14. Growth of monodisperse nanocrystals of cerium oxide during synthesis and annealing

    International Nuclear Information System (INIS)

    Monodisperse cerium oxide nanocrystals have been successfully synthesised using simple ammonia precipitation technique from cerium(III) nitrate solution at different temperatures in the range 35-80 oC. The activation energy for growth of CeO2 nanocrystals during the precipitation is calculated as 11.54 kJ/mol using Arrhenius plot. Average crystal diameter was obtained from XRD analysis, HR-TEM and light scattering (PCS). The analysis of size data from HR-TEM images and PCS clearly indicated the formation of highly crystalline CeO2 particles in narrow size range. CeO2 nanocrystals precipitated at 35 oC were further annealed at temperatures in the range 300-700 oC. The activation energy for crystal growth during annealing is also calculated and is close to the reported values. An effort is made to predict the mechanism of crystal growth during the precipitation and annealing.

  15. Copper-cerium oxides supported on carbon nanomaterial for preferential oxidation of carbon monoxide

    Institute of Scientific and Technical Information of China (English)

    高美怡; 江楠; 赵宇宏; 徐长进; 苏海全; 曾尚红

    2016-01-01

    The CuxO-CeO2/Fe@CNSs, CuxO-CeO2/MWCNTs-Co and CuxO-CeO2/MWCNTs-Ni catalysts were prepared by the im-pregnation method and characterized by transmission electron microscopy, scanning electron microscopy, X-ray powder diffrac-tion, H2-temperature programmed reduction and N2 adsorption-desorption techniques. It was found that the Fe nanoparticles were encapsulated into the multi-layered carbon nanospheres (CNSs). However, the multi-wall carbon nanotubes (MWCNTS) were generated on the Co/Al2O3 and Ni/Al2O3 precursor. The addition of carbon nanomaterial as supports could improve structural properties and low-temperature activity of the CuO-CeO2 catalyst, and save the used amount of metal catalysts in the temperature range with high selectivity for CO oxidation. The copper-cerium oxides supported on carbon nanomaterial had good resistence to H2O and CO2.

  16. UV-Shielding and Catalytic Characteristics of Nanoscale Zinc-Cerium Oxides

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Fine particles of zinc-cerium oxides (ZCO) used as an ultraviolet filter were prepared via combustion synthesis route. The catalytic activity, UV-shielding performance, surface modification and application of ZCO in polyester varnish were discussed in detail. The experimental results indicate that the photo-catalytic activity of ZCO is much smaller than these of ZnO and TiO2; the oxidation catalytic activity of ZCO is far lower than that of CeO2; the ZCO has shown excellent ultraviolet absorption in the range of UV;addition modified ZCO (MZCO) into polyester will enhance the UV-shielding capability of polyester.

  17. Evaluation of mechanically treated cerium (IV) oxides as corrosion inhibitors for galvanized steel

    International Nuclear Information System (INIS)

    The use of cerium salts as corrosion inhibitors for hot dip galvanized steel has been object of a numerous studies in the last few years. The role of cerium ions as corrosion inhibitors was proved: cerium is able to block the cathodic sites of the metal, forming insoluble hydroxides and oxides on the zinc surface. This fact leads to a dramatic decrease of the cathodic current densities and, therefore, to a reduction the overall corrosion processes. On the other hand, the potential of cerium oxides as corrosion inhibitors was also proposed. However, the real effectiveness of this kind of anticorrosive pigments has not been clarified yet. In this work cerium (IV) oxides are considered as corrosion inhibitors for galvanized steel. The corrosion inhibition mechanism of mechanically treated (milled) CeO2 alone and in combination with milled SiO2 nanoparticles was investigated. For this purpose milled CeO2, CeO2 and SiO2 milled together and milled SiO2 particles were studied as corrosion inhibitors in water solution. Therefore, the different mechanically treated particles were dispersed in 0.1 M NaCl solution to test their effectiveness as corrosion inhibitors for galvanized steel. The galvanized steel was immersed in the different solutions and the corrosion inhibition efficiency of the different particles was measured by means of electrochemical techniques. For this purpose, electrochemical impedance spectroscopy (EIS) measurements were carried out, monitoring the evolution of the corrosion processes occurring at the metal surface with the immersion time in the solution. The effect of the different pigments was also investigated by carrying out anodic and cathodic polarization measurements. The polarization curves were acquired under conditions of varied pH. The experimental measurements suggest that the mechanical treatment performed on the SiO2 and CeO2 particles promote the formation of an effective corrosion pigment. The tests evidence also the beneficial effect of

  18. Preparation of magnetron sputtered thin cerium oxide films with a large surface on silicon substrates using carbonaceous interlayers.

    Science.gov (United States)

    Dubau, Martin; Lavková, Jaroslava; Khalakhan, Ivan; Haviar, Stanislav; Potin, Valerie; Matolín, Vladimír; Matolínová, Iva

    2014-01-22

    The study focuses on preparation of thin cerium oxide films with a porous structure prepared by rf magnetron sputtering on a silicon wafer substrate using amorphous carbon (a-C) and nitrogenated amorphous carbon films (CNx) as an interlayer. We show that the structure and morphology of the deposited layers depend on the oxygen concentration in working gas used for cerium oxide deposition. Considerable erosion of the carbonaceous interlayer accompanied by the formation of highly porous carbon/cerium oxide bilayer systems is reported. Etching of the carbon interlayer with oxygen species occurring simultaneously with cerium oxide film growth is considered to be the driving force for this effect resulting in the formation of nanostructured cerium oxide films with large surface. In this regard, results of oxygen plasma treatment of a-C and CNx films are presented. Gradual material erosion with increasing duration of plasma impact accompanied by modification of the surface roughness is reported for both types of films. The CNx films were found to be much less resistant to oxygen etching than the a-C film. PMID:24372305

  19. Effect of coating parameters on the microstructure of cerium oxide conversion coatings

    International Nuclear Information System (INIS)

    The microstructure and morphology of cerium oxide conversion coatings prepared under different deposition conditions were characterized by transmission electron microscopy (TEM). The coatings were formed by a spontaneous reaction between a water-based solution containing CeCl3 and aluminum alloy 7075-T6 substrates. Microstructural characterization was performed to determine the crystallinity of the coatings and to obtain a better understanding of the deposition parameters on coating microstructure. The results of TEM imaging and electron diffraction analysis indicated that the as-deposited coating was composed of nanocrystalline particles of a previously unreported cerium compound. The particles of the coatings produced using glycerol as an additive were found to be much finer than those of the coatings prepared in the absence of glycerol. This indicates that glycerol may act as a grain refiner and/or growth inhibitor during coating deposition. After deposition, the coated panels were treated for 5 min in a phosphate sealing solution. The sealing treatment converted the as-deposited coating into hydrated cerium phosphate. Panels coated from solutions containing no glycerol followed by phosphate sealing performed poorly in salt fog tests. With glycerol addition, the corrosion resistance of the coatings that were phosphate sealed improved considerably, achieving an average passing rate of 85%

  20. Basic study on decontamination of TRU waste with cerium-mediated electrolytic oxidation method

    International Nuclear Information System (INIS)

    It is important to decrease the radioactivity of transuranium (TRU) waste arising from reprocessing plants by the decontamination for its disposal. In order to dispose TRU waste safely and rationally, a decontamination technology is required to be developed. For this purpose, the Japan Atomic Energy Agency has conducted a basic study focusing on the cerium-mediated electrolytic oxidation (CeMEX) method. In this study, two series of tests were performed to confirm the sufficient corrosion rate for the decontamination of metallic waste with the CeMEX method. One is the pre-corrosion test to survey an optimum solution condition for the generation of cerium(IV) ion under different conditions in concentration of cerium(III) ion and nitric acid. The other is the corrosion test to evaluate the corrosion rate of stainless steel as simulating waste under the optimized solution condition. It was confirmed that the average corrosion rate of stainless steel was 3.3 μm/h for 90 hours. This means that the decontamination can be completed within 6 hours and that the decontamination solution can be recycled 15 times, assuming that the decontamination to the clearance-level needs corrosion depth of 20 μm. From the results, the CeMEX method is sufficiently applicable to the decontamination of TRU waste. (author)

  1. Chromium VI adsorption on cerium oxide nanoparticles and morphology changes during the process

    International Nuclear Information System (INIS)

    In this study, suspended cerium oxide nanoparticles stabilized with hexamethylenetetramine were used for the removal of dissolved chromium VI in pure water. Several concentrations of adsorbent and adsorbate were tested, trying to cover a large range of possible real conditions. Results showed that the Freundlich isotherm represented well the adsorption equilibrium reached between nanoparticles and chromium, whereas adsorption kinetics could be modeled by a pseudo-second-order expression. The separation of chromium-cerium nanoparticles from the medium and the desorption of chromium using sodium hydroxide without cerium losses was obtained. Nanoparticles agglomeration and morphological changes during the adsorption-desorption process were observed by TEM. Another remarkable result obtained in this study is the low toxicity in the water treated by nanoparticles measured by the Microtox commercial method. These results can be used to propose this treatment sequence for a clean and simple removal of drinking water or wastewater re-use when a high toxicity heavy metal such as chromium VI is the responsible for water pollution.

  2. Optical properties and structural characteristics of zinc oxide-cerium oxide doped polyvinyl alcohol films

    Energy Technology Data Exchange (ETDEWEB)

    Chandrakala, H.N. [Department of Chemistry, Siddaganga Institute of Technology, Tumkur 572 103 (India); Department of Polymer Science and Technology, Sri Jayachamarajendra College of Engineering, Mysore 570 006 (India); Ramaraj, B. [Central Institute of Plastics Engineering and Technology (CIPET), Ahmedabad 382 445 (India); Shivakumaraiah [Department of Chemistry, Siddaganga Institute of Technology, Tumkur 572 103 (India); Siddaramaiah, E-mail: siddaramaiah@yahoo.com [Department of Polymer Science and Technology, Sri Jayachamarajendra College of Engineering, Mysore 570 006 (India)

    2014-02-15

    Highlights: • A polyvinyl alcohol film doped with ZnO-Ce{sub 2}O{sub 3} nanoparticles was prepared by casting technique. • PL spectra shows intense emission peaks due to the presence of ZnO-Ce{sub 2}O{sub 3} nanoparticles. • The band gap energy measured shows enhanced conductivity for PVA films. • TG analysis reveal enhanced thermal stability for PVA/ZnO-Ce{sub 2}O{sub 3} nanocomposites. • The data generated will support the PVA nanocomposites for applications in Opto-electronic devices. -- Abstract: Influence of zinc oxide-cerium oxide (ZnO-Ce{sub 2}O{sub 3}) nanoparticles on the structural characteristics and optical properties of polyvinyl alcohol (PVA) films have been investigated. The fabricated PVA/ZnO-Ce{sub 2}O{sub 3} nanocomposite films have been characterized by UV–visible spectroscopy, photoluminescence spectroscopy, X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The UV–vis analysis reveals the interaction of ZnO-Ce{sub 2}O{sub 3} nanoparticles through hydroxyl groups of PVA. Photoluminescence spectra shows intense emission peaks due to the presence of ZnO-Ce{sub 2}O{sub 3} nanoparticles. Microwave irradiation analysis shows the effect of nanoparticles on the degradation profile of PVA. The band gap energy measured based on UV–vis analysis shows enhanced conductivity of PVA films. XRD analysis shows the effect of annealing temperature on the XRD patterns of PVA. DSC analysis shows reduction in percentage of crystallinity with an increase in annealing temperatures and nanoparticles concentration. Thermal analysis by TGA shows enhanced thermal stability for the nanocomposites as compared to the PVA matrix. The data generated from these investigations will support the PVA nanocomposites for possible applications in opto-electronic devices.

  3. Characteristics of cerium-gadolinium oxide (CGO) suspensions as a function of dispersant and powder properties

    DEFF Research Database (Denmark)

    Phair, John; Lönnroth, Nadja; Lundberg, Mats;

    2009-01-01

    A series of concentrated suspensions ( = 0.18–0.34) of cerium-gadolinium oxide (CGO) in terpineol were prepared as a function of dispersant, powder surface area and solids concentration. The stability of the suspensions was assessed by rheological measurements including viscosity and oscillatory...... measurements. Six dispersants with different molecular weights and terminal groups were compared for their relative efficiency in dispersing the powders by viscosity measurements. A Rhodafac dispersant, a long chain polymer containing phosphoric acid terminal groups, was found to produce suspensions with the...

  4. Kinetics of bromide catalysed oxidation of dextrose by cerium (IV) in aqueous sulphuric acid solution

    International Nuclear Information System (INIS)

    Kinetics of bromide catalysed oxidation of dextrose by CeIV in aqueous sulphuric acid medium show first order dependence each in dextrose and cerium(IV). The reaction rate decreases on increasing the concentration of hydrogen ion. The increase in [HSO4-] or [SO42-] decreases the rate. The bromide ion shows positive catalytic effect on the reaction rate. The value of activation energy has been calculated and a suitable mechanism confirming to the kinetic data is proposed. (author). 3 refs., 3 tabs

  5. Direct liquid injection chemical vapor deposition of platinum doped cerium oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zanfoni, N.; Avril, L.; Imhoff, L.; Domenichini, B., E-mail: bruno.domenichini@u-bourgogne.fr; Bourgeois, S.

    2015-08-31

    Thin films of Pt-doped CeO{sub 2} were grown by direct liquid injection chemical vapor deposition on silicon wafer covered by native oxide at 400 °C using Ce(IV) alkoxide and organoplatinum(IV) as precursors. X-ray photoelectron spectra evidenced that the platinum oxidation state is linked to the deposition way. For platinum deposited on top of cerium oxide thin films previously grown, metallic platinum particles were obtained. Cerium and platinum codeposition allowed obtaining a Pt{sup 0} and Pt{sup 2+} mixture with the Pt{sup 2+} to Pt ratio strongly dependent on the platinum flow rate during the deposition. Indeed, the lower the platinum precursor flow rate is, the higher the Pt{sup 2+} to Pt ratio is. Moreover, surface and cross-sectional morphologies obtained by scanning electron microscopy evidenced porous layers in any case. - Highlights: • Pt-doped ceria were synthesized. • Films were obtained by direct liquid injection chemical vapor deposition. • Simultaneous deposition of Pt and Ce was used to obtain homogeneous films. • Pt{sup 2+} was revealed through X-ray photoelectron spectroscopy. • Different routes were used to exalt Pt{sup 2+}/Pt ratio.

  6. Direct liquid injection chemical vapor deposition of platinum doped cerium oxide thin films

    International Nuclear Information System (INIS)

    Thin films of Pt-doped CeO2 were grown by direct liquid injection chemical vapor deposition on silicon wafer covered by native oxide at 400 °C using Ce(IV) alkoxide and organoplatinum(IV) as precursors. X-ray photoelectron spectra evidenced that the platinum oxidation state is linked to the deposition way. For platinum deposited on top of cerium oxide thin films previously grown, metallic platinum particles were obtained. Cerium and platinum codeposition allowed obtaining a Pt0 and Pt2+ mixture with the Pt2+ to Pt ratio strongly dependent on the platinum flow rate during the deposition. Indeed, the lower the platinum precursor flow rate is, the higher the Pt2+ to Pt ratio is. Moreover, surface and cross-sectional morphologies obtained by scanning electron microscopy evidenced porous layers in any case. - Highlights: • Pt-doped ceria were synthesized. • Films were obtained by direct liquid injection chemical vapor deposition. • Simultaneous deposition of Pt and Ce was used to obtain homogeneous films. • Pt2+ was revealed through X-ray photoelectron spectroscopy. • Different routes were used to exalt Pt2+/Pt ratio

  7. Complete Oxidation of Methane over Palladium Supported on Alumina Modified with Calcium, Lanthanum, and Cerium Ions

    Institute of Scientific and Technical Information of China (English)

    Beata Stasinska; Wojciech Gac; Theophilos Ioannides; Andrzej Machocki

    2007-01-01

    The activity and thermal stability of Pd/Al2O3 and Pd/(Al2O3+MOx) (M=Ca, La, Ce) palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the alumina-supported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.

  8. Cathodic electrodeposition of cerium based oxides on carbon steel from concentrated cerium nitrate. Part II: Influence of electrodeposition parameters and of the addition of PEG

    Energy Technology Data Exchange (ETDEWEB)

    Hamlaoui, Y. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France); Institut des Sciences et Sciences de l' Ingenieur, Centre Universitaire de Souk-Ahras, BP 1553, 41000 Souk-Ahras (Algeria); Tifouti, L. [Laboratoire de Genie de l' Environnement, Universite Badji Mokhtar, BP 1223, 23020, El Hadjar-Annaba (Algeria); Remazeilles, C. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France); Pedraza, F., E-mail: fpedraza@univ-lr.fr [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France)

    2010-03-15

    The mechanisms of formation of cerium based oxides on carbon steel by cathodic electrodeposition from relatively concentrated cerium nitrate solutions were investigated in a previous work (Part I). It was shown that some corrosion products developed on the steel upon and soon after coating, thereby suggesting the films were not protective. This work (Part II) focuses on the influence of various elaboration parameters on the composition and morphology of the deposits likely to improve the corrosion resistance of carbon steel. It will be shown that an increase of the precursor concentration increases the Ce(OH){sub 3} content of the deposits and brings about larger crystallite sizes at low to moderate applied current densities. As a result, the formation of the carbonated green rust corrosion product is not hindered. The kinetics of formation of the film follows a polynomial law in which concurrent deposition and dissolution steps are combined. However, an increase of the deposition time results in a reduced content of Ce(OH){sub 3} in the layers, hence in an evolution of the colour of the deposits. Similarly, the increase of the temperature of the bath brings about significant modifications of the surface morphology, of the crystallite size and of the content of oxygen vacancies that are suspected not to confer adequate protection. In contrast, the addition of 10 g L{sup -1} of PEG to the 0.1 M cerium nitrate solutions will be shown to inhibit the development of the carbonated green rust.

  9. Cathodic electrodeposition of cerium based oxides on carbon steel from concentrated cerium nitrate. Part II: Influence of electrodeposition parameters and of the addition of PEG

    International Nuclear Information System (INIS)

    The mechanisms of formation of cerium based oxides on carbon steel by cathodic electrodeposition from relatively concentrated cerium nitrate solutions were investigated in a previous work (Part I). It was shown that some corrosion products developed on the steel upon and soon after coating, thereby suggesting the films were not protective. This work (Part II) focuses on the influence of various elaboration parameters on the composition and morphology of the deposits likely to improve the corrosion resistance of carbon steel. It will be shown that an increase of the precursor concentration increases the Ce(OH)3 content of the deposits and brings about larger crystallite sizes at low to moderate applied current densities. As a result, the formation of the carbonated green rust corrosion product is not hindered. The kinetics of formation of the film follows a polynomial law in which concurrent deposition and dissolution steps are combined. However, an increase of the deposition time results in a reduced content of Ce(OH)3 in the layers, hence in an evolution of the colour of the deposits. Similarly, the increase of the temperature of the bath brings about significant modifications of the surface morphology, of the crystallite size and of the content of oxygen vacancies that are suspected not to confer adequate protection. In contrast, the addition of 10 g L-1 of PEG to the 0.1 M cerium nitrate solutions will be shown to inhibit the development of the carbonated green rust.

  10. Improvement of corrosion resistance of AZ31 Mg alloy by anodizing with co-precipitation of cerium oxide

    Institute of Scientific and Technical Information of China (English)

    Salah Abdelghany SALMAN; Ryoichi ICHINO; Masazumi OKIDO

    2009-01-01

    Anodizing of AZ31 Mg alloy in NaOH solution by co-precipitation of cerium oxide was investigated. The chemical composition and phase structure of the coating film were determined via optical microscopy, SEM and XRD. The corrosion properties of the anodic film were characterized by using potentiodynamic polarization curves in 17 mmol/L NaCl and 0.1 mol/L Na2SO4 solution at 298 K. The corrosion resistance of AZ31 magnesium alloy is significantly improved by adding cerium oxide to alkaline solution. In addition, the surface properties are enhanced and the film contains no crack.

  11. Cerium oxide nanoparticles protect rodent lungs from hypobaric hypoxia-induced oxidative stress and inflammation

    Directory of Open Access Journals (Sweden)

    Arya A

    2013-11-01

    Full Text Available Aditya Arya,1 Niroj Kumar Sethy,1 Sushil Kumar Singh,2 Mainak Das,3 Kalpana Bhargava1 1Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, Defence Research and Development Organization, Delhi, 2Functional Materials Division, Solid State Physics Laboratory, Defence Research and Development Organization, Delhi, 3Biological Science and Bioengineering, Indian Institute of Technology, Kanpur, Uttar Pradesh, India Background: Cerium oxide nanoparticles (nanoceria are effective at quenching reactive oxygen species (ROS in cell culture and animal models. Although nanoceria reportedly deposit in lungs, their efficacy in conferring lung protection during oxidative stress remains unexplored. Thus, the study evaluated the protective efficacy of nanoceria in rat lung tissue during hypobaric hypoxia. Methods: A total of 48 animals were randomly divided into four equal groups (control [C], nanoceria treated [T], hypoxia [H], and nanoceria treated plus hypoxia [T+H]. Animals were injected intraperitoneally with either a dose of 0.5 µg/kg body weight/week of nanoceria (T and T+H groups or vehicle (C and H groups for 5 weeks. After the final dose, H and T+H animals were challenged with hypobaric hypoxia, while C and T animals were maintained at normoxia. Lungs were isolated and homogenate was obtained for analysis of ROS, lipid peroxidation, glutathione, protein carbonylation, and 4-hydroxynonenal-adduct formation. Plasma was used for estimating major inflammatory cytokines using enzyme-linked immunosorbent assay. Intact lung tissues were fixed and both transmission electron microscopy and histopathological examinations were carried out separately for detecting internalization of nanoparticles as well as altered lung morphology. Results: Spherical nanoceria of 7–10 nm diameter were synthesized using a microemulsion method, and the lung protective efficacy of the nanoceria evaluated during hypobaric hypoxia. With repeated

  12. Force modulation atomic force microscopy: background, development and application to electrodeposited cerium oxide films

    Science.gov (United States)

    Li, Feng-Bin; Thompson, G. E.; Newman, R. C.

    1998-04-01

    In force modulation atomic force microscopy (FMAFM), vertical oscillation of the scanning tip of the AFM is added purposely and the deflection of the tip, which is influenced by surface features of the sample, is used as the z dimension to construct images. FMAFM represents a powerful technique for scientific research, but its merit has not been realized adequately to date. In this paper, the basic principles and particular features, as well as potential drawbacks of the technique, are presented and demonstrated systematically, through its application to electrochemically deposited cerium oxide films. Comparisons are also made with the more familiar contact mode AFM (CMAFM) and tapping mode AFM (TMAFM). It is shown that FMAFM reveals the major topographic features of CMAFM, but affords (i) greater resolution for sample features that are difficult in CMAFM, and (ii) continuous two-dimensional mapping of local mechanical properties on a scale of nanometres that the CMAFM, TMAFM and any other techniques, are not capable of sensing. This information can be used to elucidate other properties of the investigated surface, such as crystallinity variation, phase separation and distribution, and mechanisms of formation of deposited films. Major artifacts associated with the technique include `wedge cavity effect' and `tip slip effect', for which a geometric model is proposed to elucidate their origins. The cerium oxide films are shown to be composed of relatively hard crystalline grains, of well-defined individual geometry and comparatively regular packing, alongside relatively soft amorphous patches, devoid of distinct geometry and assembled disorderly. These features are consistent with a nucleation and growth mechanism of the deposition, in which crystalline nuclei arise and grow from an intermediate cerium gel mass, produced in the interfacial region during deposition.

  13. Cerium-based binary and ternary oxides in the transesterification of dimethylcarbonate with phenol.

    Science.gov (United States)

    Dibenedetto, Angela; Angelini, Antonella; di Bitonto, Luigi; De Giglio, Elvira; Cometa, Stefania; Aresta, Michele

    2014-04-01

    Diphenyl carbonate (DPC) plays a key role in phosgene-free carbonylation processes. It can be produced by transesterification of dimethyl carbonate (DMC) with phenol in the presence of catalysts. Methyl phenyl carbonate (MPC) is first produced that is then converted into DPC by either disproportionation or further transesterification with phenol. Cerium-based bimetallic oxides (with the heterometal being niobium, iron, palladium, or aluminum) are used as catalysts in the transesterification of DMC to synthesize MPC. The catalytic activity is affected by the type and concentration of the heterometal. XPS, IR and elementary analyses are employed to characterize the new catalysts. Differently from pure oxides, the mixed oxides produce a significant increase of the conversion and selectivity towards MPC. PMID:24616260

  14. Low Temperature Constrained Sintering of Cerium Gadolinium OxideFilms for Solid Oxide Fuel Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Nicholas, Jason.D.

    2007-06-30

    Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95}, and to evaluate whether they could be used to produce dense, constrained Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} films at temperatures below 1000 C. To find the optimal sintering aid, Ce{sub 0.9}Gd{sub 0.1}O{sub 1.95} was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800 C--a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aid's effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O1.95 indicated that lithium affects sintering by producing a Li{sub 2}O-Gd{sub 2}O{sub 3}-CeO{sub 2} liquid at the CGO grain boundaries. Due to this liquid phase sintering, it was possible to produce dense, crack-free constrained films of CGO at the record low temperature of 950 C using cheap, colloidal spray deposition processes. This is the first time dense constrained CGO films have been produced below 1000 C and could help commercialize metal supported ceria based solid oxide fuel cells.

  15. Silver ion catalyzed cerium(IV) mediated electrochemical oxidation of phenol in nitric acid medium

    International Nuclear Information System (INIS)

    Mediated electrochemical oxidation (MEO) is one of the sustainable processes for organic pollutant destruction and has been employed for organic mineralization reactions by many researchers. In the MEO a metal ion capable of exhibiting redox behavior is oxidized from lower oxidation state to higher oxidation state by an electrochemical cell and subsequently used as an oxidant for mineralizing the toxic organics into CO2 and water. The net result is the consumption of electrical energy for organic mineralization. Therefore, the current efficiency is an important factor and maximizing the current efficiency is one of the ways of reducing the running cost of the MEO process. It has been reported in the literature that the current efficiency could be increased using a metal ion catalyst having a good redox potential. In this study Ce(IV) mediated electrochemical oxidation of phenol was carried out with silver ion catalyst. The current efficiency for the electro-oxidation of cerium(III) in nitric acid was found to be increased by the addition of silver ions. This mixed mediator system was tested for the oxidation of phenol in order to optimize the parameters for organic pollutant destruction. The mineralization efficiency calculated based on the CO2 evolution was found to be higher for silver catalyzed Ce(IV) mediated oxidation compared to the non-silver catalyzed system

  16. Dielectric properties and electronic transitions of porous and nanostructured cerium oxide films

    International Nuclear Information System (INIS)

    Cerium dioxide (CeO2) exhibits exceptional electronic properties such as optical transparency and high refractive index (n) and high dc dielectric constant (k). Therefore, it is an attractive material for ultra-thin gate oxide in CMOS technology, where high-k dielectrics are required. We study the electronic properties of nanostructured and porous cerium oxide (CeOx) films, 110-500 nm thick, grown on Si by electron beam evaporation (EBE) and ion beam assisted deposition (IBAD). The film microstructure and morphology (grain size, porosity, defect concentration, surface and interface roughness) are controlled by varying the process parameters appropriately. They have been studied by high-resolution and transmission electron microscopy (HRTEM). The optical properties have been studied by spectroscopic ellipsometry (SE) and k was determined by capacitance measurements. We have found that the values of k and n (1.6-2.5 depending on porosity) are affected by the electronic transitions, which are strongly correlated with the microstructure and morphology of the films. We investigate how the microstructure and morphology variations affect the absolute values of the dc dielectric constant and of the dielectric function at the UV-Vis and IR spectral regions. In addition, we investigate the very important role of the defects, which have the form of grain boundaries, trivalent Ce3+ and O vacancies. As a result we were able to tailor n and k of CeOx films controlling their porosity and defect density

  17. FT-IR Studies of Cerium Oxide Nanoparticles and Natural Zeolite Materials

    Directory of Open Access Journals (Sweden)

    Oana Lelia Pop

    2015-05-01

    Full Text Available An emerging topic of our days is nanoscience and nanotechnology successfully applied in the food industry. Characteristics such as size, surface area and morphology can modify the basic properties and the chemical reactivity of the nanomaterials. The breakthrough of innovative materials, processes, and phenomena at the nanoscale, as well as the progress of new experimental and theoretical techniques for research, supply novel opportunities for the expansion of original nanosystems and nanostructured materials. These study examine two types of nanoparticles, namely cerium oxide nanoparticles (CeO2 NP and natural zeolites. In view of the importance of CeO2 NP in various biological applications, the primary objective of this study is to characterise four samples of CeO2 NP in order to understand the role of the synthesis process in the final product. Nanocrystalline natural zeolites are materials with interesting properties which allows them to be used as adjuvant in many therapies. The characterisation of CeO2 NP and two types of natural zeolites using Fourier Transform Infrared (FT-IR spectroscopy is described. Therefore, this study examined two types of nanomaterials, namely cerium oxide nanoparticles and zeolites, for further applications on microorganisms and living cells.

  18. Surface study of cerium oxide based coatings obtained by cathodic electrodeposition on zinc

    International Nuclear Information System (INIS)

    A surface study of electrodeposited cerium oxide based coatings is presented. Different surface analytical techniques were used in order to obtain complementary information to fully characterize such complex systems. X-ray Photoelectron Spectroscopy was used as the main technique to determine the surface composition of the coating. The analysis of the core level peaks of the elements provides additional information about the functional groups present on the surface. A mixture of Ce (III) and Ce (IV) was found in the coating and their proportion was calculated at different depths. The analysis of the O 1s core level peak revealed a triple structure whose origin will be discussed. To support the results obtained, electron stimulated desorption was performed. The study was completed with Auger electron spectroscopy and Raman spectroscopy, both techniques having different surface sensitivities. From all these results, it is derived that incomplete electrochemical reactions occurred during the growth of the coatings. This led to rather complex compositions, in which defective cerium oxides are the major species. In addition, hydroxides, carbonates and nitrates are also present, together with adsorbed water.

  19. Surface study of cerium oxide based coatings obtained by cathodic electrodeposition on zinc

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, L., E-mail: lidia.martinez@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Cantoblanco, 28049 Madrid (Spain); Roman, E.; Segovia, J.L. de [Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Cantoblanco, 28049 Madrid (Spain); Poupard, S.; Creus, J.; Pedraza, F. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle, Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France)

    2011-05-01

    A surface study of electrodeposited cerium oxide based coatings is presented. Different surface analytical techniques were used in order to obtain complementary information to fully characterize such complex systems. X-ray Photoelectron Spectroscopy was used as the main technique to determine the surface composition of the coating. The analysis of the core level peaks of the elements provides additional information about the functional groups present on the surface. A mixture of Ce (III) and Ce (IV) was found in the coating and their proportion was calculated at different depths. The analysis of the O 1s core level peak revealed a triple structure whose origin will be discussed. To support the results obtained, electron stimulated desorption was performed. The study was completed with Auger electron spectroscopy and Raman spectroscopy, both techniques having different surface sensitivities. From all these results, it is derived that incomplete electrochemical reactions occurred during the growth of the coatings. This led to rather complex compositions, in which defective cerium oxides are the major species. In addition, hydroxides, carbonates and nitrates are also present, together with adsorbed water.

  20. Cerium oxide nanoparticles stimulate proliferation of primary mouse embryonic fibroblasts in vitro.

    Science.gov (United States)

    Popov, Anton L; Popova, Nelly R; Selezneva, Irina I; Akkizov, Azamat Y; Ivanov, Vladimir K

    2016-11-01

    The increasing application of cell therapy technologies in the treatment of various diseases requires the development of new effective methods for culturing primary cells. The major limitation for the efficient use of autologous cell material is the low rate of cell proliferation. Successful cell therapy requires sufficient amounts of cell material over a short period of time with the preservation of their differentiation and proliferative potential. In this regard, the development of novel, highly efficient stimulators of proliferative activity in stem cells is a truly urgent task. In this paper we have demonstrated that citrate-stabilized cerium oxide nanoparticles (nanoceria) enhance the proliferative activity of primary mouse embryonic fibroblasts in vitro. Cerium oxide nanoparticles stimulate cell proliferation in a wide range of concentrations (10(-3)М-10(-9)M) through reduction of intracellular levels of reactive oxygen species (ROS) during the lag phase of cell growth and by modulating the expression level of the major antioxidant enzymes. We found the optimal concentration of nanoceria, which provides the greatest acceleration of cell proliferation in vitro, while maintaining the levels of intracellular ROS and mRNA of antioxidant enzymes in the physiological range. Our results confirm that nanocrystalline ceria can be considered as a basis for effective and inexpensive supplements in cell culturing. PMID:27524035

  1. Thermodynamic Studies of the Phase Relationships of Nonstoichiometric Cerium Oxides at Higher Temperatures

    DEFF Research Database (Denmark)

    Sørensen, Ole Toft

    1976-01-01

    Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater-or-equal, slan......Partial molar thermodynamic quantities for oxygen in nonstoichiometric cerium oxides were determined by thermogravimetric analysis in CO/CO2 mixtures in the temperature range 900–1400°C. Under these conditions compositions within the range 2.00 greater-or-equal, slanted O/M greater......-or-equal, slanted not, vert, similar1.75 could be obtained. A detailed analysis of the data shows that the α′-phase region in the phase diagram, previously described as a grossly nonstoichiometric phase, can be divided into several subregions each consisting of an apparent nonstoichiometric single phase. The finer...... details of the thermodynamic data, however, suggest that some of these subregions can be further split into ordered intermediate phases with compositions following the series MnO2n−2. Supplementary high-temperature X-ray diffraction studies under vacuum were made at temperatures up to 855°C. At the higher...

  2. Effect of cerium ion implantation on the oxidation behavior of zircaloy-4 at 500 degree sign C

    CERN Document Server

    Chen, X W; Yu, H R; Zhou, Q G; Chen, B S

    2002-01-01

    In order to investigate the oxidation behavior changes of zircaloy-4 induced by cerium ion implantation using a MEVVA source at an energy of 40 keV with a dose range from 1x10 sup 1 sup 6 to 1x10 sup 1 sup 7 ions/cm sup 2 at the maximum temperature of 130 degree sign C, weight gain curves of the different specimens including as-received zircaloy-4 and cerium-implanted zircaloy-4 were measured after oxidation in air at 500 degree sign C for 100 min. It was obviously found that a significant improvement was achieved in the oxidation behavior of cerium ion implanted zircaloy-4 compared with that of the as-received zircaloy-4. The depth profile of the element composition in the surface region of the samples was obtained by Auger electron spectroscopy, and the valence of the oxides in the scale was analyzed by X-ray photoemission spectroscopy. Glancing angle X-ray diffraction employed to examine the phase transformation in the oxide films showed that the addition of cerium transformed the phase from monoclinic zir...

  3. Heteroaggregation of Cerium Oxide Nanoparticles and Nanoparticles of Pyrolyzed Biomass.

    Science.gov (United States)

    Yi, Peng; Pignatello, Joseph J; Uchimiya, Minori; White, Jason C

    2015-11-17

    Heteroaggregation with indigenous particles is critical to the environmental mobility of engineered nanomaterials (ENM). We studied heteroaggregation of ceria nanoparticles (n-CeO2), as a model for metal oxide ENM, with nanoparticles of pyrogenic carbonaceous material (n-PCM) derived from pecan shell biochar, a model for natural chars and human-made chars used in soil remediation and agriculture. The TEM and STEM images of n-PCM identify both hard and soft particles, both C-rich and C,O,Ca-containing particles (with CaCO3 crystals), both amorphous and "onion-skin" C-rich particles, and traces of nanotubes. Heteroaggregation was evaluated at constant n-CeO2, variable n-PCM concentration by monitoring hydrodynamic diameter by dynamic light scattering and ζ-potential under conditions where n-PCM is "invisible". At pH 5.3, where n-CeO2 and n-PCM are positively and negatively charged, respectively, and each stable to homoaggregation, heteroaggregation is favorable and occurs by a charge neutralization-charge reversal mechanism (CNCR): in this mechanism, primary heteroaggregates that form in the initial stage are stable at low or high n-PCM concentration due to electrostatic repulsion, but unstable at intermediate n-PCM concentration, leading to secondary heteroaggregation. The greatest instability coincides with full charge neutralization. At pH 7.1, where n-CeO2 is neutral and unstable alone, and n-PCM is negative and stable alone, heteroaggregation occurs by a charge-accumulation, core-shell stabilization (CACS) mechanism: n-PCM binds to and forms a negatively charged shell on the neutral surface of the nascent n-CeO2 core, stabilizing the core-shell heteraggregate at a size that decreases with n-PCM concentration. The CNCR and CACS mechanisms give fundamental insight into heteroaggregation between oppositely charged, and between neutral and charged nanoparticles. PMID:26461459

  4. Catalytic oxidative treatment of diluted black liquor at mild conditions using copper oxide/cerium oxide catalyst.

    Science.gov (United States)

    Garg, Anurag; Mishra, Indra M; Chand, Shri

    2008-02-01

    Wet-air oxidation of diluted black liquor (chemical oxygen demand [COD] approximately 3250 to 14 500 mg/L) was performed at mild operating conditions (temperature = 388 to 423 K and total pressure = 0.6 MPa) in the presence of heterogeneous 60% copper oxide (CuO)/ 40% cerium oxide (CeO2) catalyst. Maximum COD reduction of 77.3% was obtained at 423 K at pH 3.0, which was marginally higher than that obtained at 413 K temperature (77.1%). In the acidic environment (pH < or = 3), most of the COD was removed in the form of settleable solids during the transient heating of the wastewater from room temperature to the desired one. The solid residue obtained after the reaction has a heating value of 20.1 MJ/kg, which is comparable with that of Indian coal. Thermal degradation kinetic determination suggested that thermal characteristics of the solid residue are well represented by a power law model with Agarwal and Sivasubramanian approximation (Safi et al., 2004). PMID:18330223

  5. Redox-active cerium oxide nanoparticles protect human dermal fibroblasts from PQ-induced damage

    Directory of Open Access Journals (Sweden)

    Claudia von Montfort

    2015-04-01

    Full Text Available Recently, it has been published that cerium (Ce oxide nanoparticles (CNP; nanoceria are able to downregulate tumor invasion in cancer cell lines. Redox-active CNP exhibit both selective pro-oxidative and antioxidative properties, the first being responsible for impairment of tumor growth and invasion. A non-toxic and even protective effect of CNP in human dermal fibroblasts (HDF has already been observed. However, the effect on important parameters such as cell death, proliferation and redox state of the cells needs further clarification. Here, we present that nanoceria prevent HDF from reactive oxygen species (ROS-induced cell death and stimulate proliferation due to the antioxidative property of these particles.

  6. Structural Characteristics of Cerium Oxide Nanocrystals Prepared by the Microemulsion Method

    Institute of Scientific and Technical Information of China (English)

    J.Zhang; X.Ju; Z.Y.Wu; T.Liu; T.D.Hu; Y.N.Xie

    2001-01-01

    The aim of this work is to investigate the microstructure development of erium oxide nanocrystal,prepared by the microemulsion process,as a function of annealing temperature in air.Combined with the HRTEM and the thermogravimetric-differential thermal analysis in air.Combined withthe HRTEm and the thremogravimetric-differential thermal analysis(TG-DTA),the XRD patterns reveal that the sample annealed at 623 K is amorphous,and the formation of cerium oxide nanocrystal occurs above 773 K.The local structural and electronic properties in the nanocrystallization process are probed by X-ray absorption spectra (XAS) at the Ce L3 edge.It is found that the phase structure changes from triclinic to cubic (CeO2),and the electroic structure changes from Ce3 to Ce4 upon increasing the annealing temperature.

  7. Germination and early plant development of ten plant species exposed to titanium dioxide and cerium oxide nanoparticles

    Science.gov (United States)

    Ten agronomic plant species were exposed to different concentrations of nano titanium dioxide (nTiO2) or nano cerium oxide (nCeO2) (0, 250, 500 and 1000 mg/L) to examine potential effects on germination and early seedling development. We modified a standard test protocol develop...

  8. Air, aqueous and thermal stabilities of Ce3+ ions in cerium oxide nanoparticle layers with substrates

    KAUST Repository

    Naganuma, Tamaki

    2014-01-01

    Abundant oxygen vacancies coexisting with Ce3+ ions in fluorite cerium oxide nanoparticles (CNPs) have the potential to enhance catalytic ability, but the ratio of unstable Ce3+ ions in CNPs is typically low. Our recent work, however, demonstrated that the abundant Ce3+ ions created in cerium oxide nanoparticle layers (CNPLs) by Ar ion irradiation were stable in air at room temperature. Ce valence states in CNPs correlate with the catalytic ability that involves redox reactions between Ce3+ and Ce4+ ions in given application environments (e.g. high temperature in carbon monoxide gas conversion and immersion conditions in biomedical applications). To better understand the mechanism by which Ce3+ ions achieve stability in CNPLs, we examined (i) extra-long air-stability, (ii) thermal stability up to 500 °C, and (iii) aqueous stability of Ce 3+ ions in water, buffer solution and cell culture medium. It is noteworthy that air-stability of Ce3+ ions in CNPLs persisted for more than 1 year. Thermal stability results showed that oxidation of Ce 3+ to Ce4+ occurred at 350 °C in air. Highly concentrated Ce3+ ions in ultra-thin CNPLs slowly oxidized in water within 1 day, but stability was improved in the cell culture medium. Ce 3+ stability of CNPLs immersed in the medium was associated with phosphorus adsorption on the Ce3+ sites. This study also illuminates the potential interaction mechanisms of stable Ce3+ ions in CNPLs. These findings could be utilized to understand catalytic mechanisms of CNPs with abundant oxygen vacancies in their application environments. © The Royal Society of Chemistry 2014.

  9. Computational and Experimental Study of the Thermodynamics of Uranium-Cerium Mixed Oxides

    Science.gov (United States)

    Hanken, Benjamin Edward

    The thermophysical properties of mixed oxide (MOX) fuels, and how they are influenced by the incorporation of fission products and other actinides, must be well understood for their safe use in an advanced fuel cycle. Cerium is a common plutonium surrogate in experimental studies of MOX, as it closely matches plutonium's ionic radii in the 3+ and 4+ oxidation states, and is soluble in fluorite-structured UO2. As a fission product, cerium's effects on properties of MOX are also of practical interest. To provide additional insights on structure-dependent behavior, urania solid solutions can be studied via density functional theory (DFT), although approaches beyond standard DFT are needed to properly account for the localized nature of the ƒ-electrons. In this work, DFT with Hubbard-U corrections (DFT+U) was employed to study the energetics of fluorite-structured U1-yCe yO2 mixtures. The employed computational approach makes use of a procedure which facilitates convergence of the calculations to multiple self-consistent DFT+U solutions for a given cation arrangement, corresponding to different charge states for the U and Ce ions in several prototypical cation arrangements. Results indicate a significant dependence of the structural and energetic properties of U1-yCeyO2 on the nature of both charge and cation ordering. With the effective Hubbard-U parameters that reproduce well the measured oxidation-reduction energies for urania and ceria, it was found that charge transfer between U4+ and Ce4+ ions, leading to the formation of U5+ and Ce3+, gives rise to an increase in the mixing energy in the range of 4-14 kJ/mol of the formula unit, depending on the nature of the cation ordering. In conjunction with the computational approach, high-temperature oxide-melt drop-solution calorimetry experiments were performed on eight samples spanning compositions of y = 0.119 to y = 0.815. Room temperature mixing enthalpies of U1-yCeyO2 determined from these experiments show near

  10. Growth of monodisperse nanocrystals of cerium oxide during synthesis and annealing

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Swapankumar, E-mail: swapankumar.ghosh2@mail.dcu.ie; Divya, Damodaran [National Institute for Interdisciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research (CSIR) (India); Remani, Kottayilpadi C. [Sree Neelakanda Government Sanskrit College, Department of Chemistry (India); Sreeremya, Thadathil S. [National Institute for Interdisciplinary Science and Technology (NIIST), Council of Scientific and Industrial Research (CSIR) (India)

    2010-06-15

    Monodisperse cerium oxide nanocrystals have been successfully synthesised using simple ammonia precipitation technique from cerium(III) nitrate solution at different temperatures in the range 35-80 {sup o}C. The activation energy for growth of CeO{sub 2} nanocrystals during the precipitation is calculated as 11.54 kJ/mol using Arrhenius plot. Average crystal diameter was obtained from XRD analysis, HR-TEM and light scattering (PCS). The analysis of size data from HR-TEM images and PCS clearly indicated the formation of highly crystalline CeO{sub 2} particles in narrow size range. CeO{sub 2} nanocrystals precipitated at 35 {sup o}C were further annealed at temperatures in the range 300-700 {sup o}C. The activation energy for crystal growth during annealing is also calculated and is close to the reported values. An effort is made to predict the mechanism of crystal growth during the precipitation and annealing.

  11. Corrosion resistance of flaky aluminum pigment coated with cerium oxides/hydroxides in chloride and acidic electrolytes

    Science.gov (United States)

    Niroumandrad, S.; Rostami, M.; Ramezanzadeh, B.

    2015-12-01

    The objective of this study was to enhance the corrosion resistance of lamellar aluminum pigment through surface treatment by cerium oxides/hydroxides. The surface composition of the pigments was studied by energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the pigment was evaluated by conventional hydrogen evolution measurements in acidic solution and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. Results showed that the Ce-rich coating composed of Ce2O3 and CeO2 was precipitated on the pigment surface after immersion in the cerium solution. The corrosion resistance of pigment was significantly enhanced after modification with cerium layer.

  12. Freshwater dispersion stability of PAA-stabilised cerium oxide nanoparticles and toxicity towards Pseudokirchneriella subcapitata

    International Nuclear Information System (INIS)

    An aqueous dispersion of poly (acrylic acid)-stabilised cerium oxide (CeO2) nanoparticles (PAA-CeO2) was evaluated for its stability in a range of freshwater ecotoxicity media (MHRW, TG 201 and M7), with and without natural organic matter (NOM). In a 15 day dispersion stability study, PAA-CeO2 did not undergo significant aggregation in any media type. Zeta potential varied between media types and was influenced by PAA-CeO2 concentration, but remained constant over 15 days. NOM had no influence on PAA-CeO2 aggregation or zeta potential. The ecotoxicity of the PAA-CeO2 dispersion was investigated in 72 h algal growth inhibition tests using the freshwater microalgae Pseudokirchneriella subcapitata. PAA-CeO2 EC50 values for growth inhibition (GI; 0.024 mg/L) were 2–3 orders of magnitude lower than pristine CeO2 EC50 values reported in the literature. The concentration of dissolved cerium (Ce3+/Ce4+) in PAA-CeO2 exposure suspensions was very low, ranging between 0.5 and 5.6 μg/L. Free PAA concentration in the exposure solutions (0.0096–0.0384 mg/L) was significantly lower than the EC10 growth inhibition (47.7 mg/L) value of pure PAA, indicating that free PAA did not contribute to the observed toxicity. Elemental analysis indicated that up to 38% of the total Cerium becomes directly associated with the algal cells during the 72 h exposure. TOF-SIMS analysis of algal cell wall compounds indicated three different modes of action, including a significant oxidative stress response to PAA-CeO2 exposure. In contrast to pristine CeO2 nanoparticles, which rapidly aggregate in standard ecotoxicity media, PAA-stabilised CeO2 nanoparticles remain dispersed and available to water column species. Interaction of PAA with cell wall components, which could be responsible for the observed biomarker alterations, could not be excluded. This study indicates that the increased dispersion stability of PAA-CeO2 leads to an increase in toxicity compared to pristine non-stabilised forms

  13. Effective improvement of interface modified strontium titanate based solid oxide fuel cell anodes by infiltration with nano-sized palladium and gadolinium-doped cerium oxide

    DEFF Research Database (Denmark)

    Abdul Jabbar, Mohammed Hussain; Høgh, Jens Valdemar Thorvald; Zhang, Wei; Blennow Tullmar, Peter; Bonanos, Nikolaos; Boukamp, Bernard A.

    2013-01-01

    The development of low temperature solid oxide fuel cell (SOFC) anodes by infiltration of Pd/Gd-doped cerium oxide (CGO) electrocatalysts in Nb-doped SrTiO3 (STN) backbones has been investigated. Modification of the electrode/electrolyte interface by thin layer of spin-coated CGO (400-500 nm) con...

  14. Catalytic ozonation of oxalate with a cerium supported palladium oxide: An efficient degradation not relying on hydroxyl radical oxidation

    KAUST Repository

    Zhang, Tao

    2011-11-01

    The cerium supported palladium oxide (PdO/CeO 2) at a low palladium loading was found very effective in catalytic ozonation of oxalate, a probe compound that is difficult to be efficiently degraded in water with hydroxyl radical oxidation and one of the major byproducts in ozonation of organic matter. The oxalate was degraded into CO 2 during the catalytic ozonation. The molar ratio of oxalate degraded to ozone consumption increased with increasing catalyst dose and decreasing ozone dosage and pH under the conditions of this study. The maximum molar ratio reached around 1, meaning that the catalyst was highly active and selective for oxalate degradation in water. The catalytic ozonation, which showed relatively stable activity, does not promote hydroxyl radical generation from ozone. Analysis with ATR-FTIR and in situ Raman spectroscopy revealed that 1) oxalate was adsorbed on CeO 2 of the catalyst forming surface complexes, and 2) O 3 was adsorbed on PdO of the catalyst and further decomposed to surface atomic oxygen (*O), surface peroxide (*O 2), and O 2 gas in sequence. The results indicate that the high activity of the catalyst is related to the synergetic function of PdO and CeO 2 in that the surface atomic oxygen readily reacts with the surface cerium-oxalate complex. This kind of catalytic ozonation would be potentially effective for the degradation of polar refractory organic pollutants and hydrophilic natural organic matter. © 2011 American Chemical Society.

  15. Fabrication of condensate microdrop self-propelling porous films of cerium oxide nanoparticles on copper surfaces.

    Science.gov (United States)

    Luo, Yuting; Li, Juan; Zhu, Jie; Zhao, Ye; Gao, Xuefeng

    2015-04-13

    Condensate microdrop self-propelling (CMDSP) surfaces have attracted intensive interest. However, it is still challenging to form metal-based CMDSP surfaces. We design and fabricate a type of copper-based CMDSP porous nanoparticle film. An electrodeposition method based on control over the preferential crystal growth of isotropic nanoparticles and synergistic utilization of tiny hydrogen bubbles as pore-making templates is adopted for the in situ growth of cerium oxide porous nanoparticle films on copper surfaces. After characterizing their microscopic morphology, crystal structure and surface chemistry, we explore their CMDSP properties. The nanostructure can realize the efficient ejection of condensate microdrops with sizes below 50 μm. PMID:25693502

  16. Biaxially aligned buffer layers of cerium oxide, yttria stabilized zirconia, and their bilayers

    International Nuclear Information System (INIS)

    Biaxially aligned cerium oxide (CeO2) and yttria stabilized zirconia (YSZ) films were deposited on Ni-based metal (Hastelloy C276) substrates held at room temperature using ion beam assisted (IBAD) magnetron deposition with the ion beam directed at 55 degree to the normal of the film plane. In addition, we achieved, room-temperature epitaxial growth of CeO2 by bias sputtering to form biaxially aligned CeO2/YSZ bilayers. The crystalline structure and in-plane orientation of films was investigated by x-ray diffraction techniques. Both the IBAD CeO2 and YSZ films, and the CeO2/YSZ bilayers have a (111) pole in the ion beam direction. copyright 1997 American Institute of Physics

  17. Biaxially aligned buffer layers of cerium oxide, yttria stabilized zirconia, and their bilayers

    Science.gov (United States)

    Gnanarajan, S.; Katsaros, A.; Savvides, N.

    1997-05-01

    Biaxially aligned cerium oxide (CeO2) and yttria stabilized zirconia (YSZ) films were deposited on Ni-based metal (Hastelloy C276) substrates held at room temperature using ion beam assisted (IBAD) magnetron deposition with the ion beam directed at 55° to the normal of the film plane. In addition, we achieved, room-temperature epitaxial growth of CeO2 by bias sputtering to form biaxially aligned CeO2/YSZ bilayers. The crystalline structure and in-plane orientation of films was investigated by x-ray diffraction techniques. Both the IBAD CeO2 and YSZ films, and the CeO2/YSZ bilayers have a (111) pole in the ion beam direction.

  18. EMISSION REDUCTION FROM A DIESEL ENGINE FUELED BY CERIUM OXIDE NANO-ADDITIVES USING SCR WITH DIFFERENT METAL OXIDES COATED CATALYTIC CONVERTER

    Directory of Open Access Journals (Sweden)

    B. JOTHI THIRUMAL

    2015-11-01

    Full Text Available This paper reports the results of experimental investigations on the influence of the addition of cerium oxide in nanoparticle form on the major physiochemical properties and the performance of diesel. The fuel is modified by dispersing the catalytic nanoparticle by ultrasonic agitation. The physiochemical properties of sole diesel fuel and modified fuel are tested with ASTM standard procedures. The effects of the additive nanoparticles on the individual fuel properties, the engine performance, and emissions are studied, and the dosing level of the additive is optimized. Cerium oxide acts as an oxygen-donating catalyst and provides oxygen for the oxidation of CO during combustion. The active energy of cerium oxide acts to burn off carbon deposits within the engine cylinder at the wall temperature and prevents the deposition of non-polar compounds on the cylinder wall which results in reduction in HC emission by 56.5%. Furthermore, a low-cost metal oxide coated SCR (selective catalyst reduction, using urea as a reducing agent, along with different types of CC (catalytic converter, has been implemented in the exhaust pipe to reduce NOx. It was observed that a reduction in NOx emission is 50–60%. The tests revealed that cerium oxide nanoparticles can be used as an additive in diesel to improve complete combustion of the fuel and reduce the exhaust emissions significantly.

  19. Recent advances of cerium oxide nanoparticles in synthesis, luminescence and biomedical studies:a review

    Institute of Scientific and Technical Information of China (English)

    何立莹; 苏玉民; 蒋兰宏; 石士考

    2015-01-01

    Nanostructured cerium oxide (CeO2) commonly known as nanoceria is a rare earth metal oxide, which plays a technologi-cally important role due to its versatile applications as automobile exhaust catalysts, oxide ion conductors in solid oxide fuel cells, electrode materials for gas sensors, ultraviolet absorbents and glass-polishing materials. However, nanoceria has little or weak lumi-nescence, and therefore its uses in high-performance luminescent devices and biomedical areas are limited. In this review, we present the recent advances of nanoceria in the aspects of synthesis, luminescence and biomedical studies. The CeO2 nanoparticles can be synthesized by solution-based methods including co-precipitation, hydrothermal, microemulsion process, sol-gel techniques, combus-tion reaction and so on. Achieving controlled morphologies and enhanced luminescence efficiency of nanoceria particles are quite es-sential for its potential energy- and environment-related applications. Additionally, a new frontier for nanoceria particles in biomedi-cal research has also been opened, which involves low toxicity, retinopathy, biosensors and cancer therapy aspects. Finally, the sum-mary and outlook on the challenges and perspectives of the nanoceria particles are proposed.

  20. Destruction of commercial pesticides by cerium redox couple mediated electrochemical oxidation process in continuous feed mode

    International Nuclear Information System (INIS)

    Mediated electrochemical oxidation was carried out for the destruction of commercial pesticide formulations using cerium(IV) in nitric acid as the mediator electrolyte solution in a bench scale set up. The mediator oxidant was regenerated in situ using an electrochemical cell. The real application of this sustainable process for toxic organic pollutant destruction lies in its ability for long term continuous operation with continuous organic feeding and oxidant regeneration with feed water removal. In this report we present the results of fully integrated MEO system. The task of operating the continuous feed MEO system for a long time was made possible by continuously removing the feed water using an evaporator set up. The rate of Ce(IV) regeneration in the electrochemical cell and the consumption for the pesticide destruction was matched based on carbon content of the pesticides. It was found that under the optimized experimental conditions for Ce(III) oxidation, organic addition and water removal destruction efficiency of ca. 99% was obtained for all pesticides studied. It was observed that the Ce(IV) concentration was maintained nearly the same throughout the experiment. The stable operation for 6 h proved that the process can be used for real applications and for possible scale up for the destruction of larger volumes of toxic organic wastes.

  1. Effects of acetic acid on microstructure and electrochemical properties of nano cerium oxide films coated on AA7020-T6 aluminum alloy

    Institute of Scientific and Technical Information of China (English)

    H. Hasannejad; T. Shahrabi; M. Aliofkhazraei

    2009-01-01

    Nano cerium oxide films were applied on AA7020-T6 aluminum alloy and the effects of acetic acid concentration on the microstructure and electrochemical properties of the coated samples were investigated by using scanning electron microscopy (SEM), X-ray diffraction (XRD), crack-flee films with well-developed grains were obtained and grain sizes of the films decreased. Elimination of cracks and decreasing grain size of the nano cerium oxide films caused corrosion resistance to increase.

  2. Potential of using cerium oxide nanoparticles for protecting healthy tissue during accelerated partial breast irradiation (APBI).

    Science.gov (United States)

    Ouyang, Zi; Mainali, Madan Kumar; Sinha, Neeharika; Strack, Guinevere; Altundal, Yucel; Hao, Yao; Winningham, Thomas Andrew; Sajo, Erno; Celli, Jonathan; Ngwa, Wilfred

    2016-04-01

    The purpose of this study is to investigate the feasibility of using cerium oxide nanoparticles (CONPs) as radical scavengers during accelerated partial breast irradiation (APBI) to protect normal tissue. We hypothesize that CONPs can be slowly released from the routinely used APBI balloon applicators-via a degradable coating-and protect the normal tissue on the border of the lumpectomy cavity over the duration of APBI. To assess the feasibility of this approach, we analytically calculated the initial concentration of CONPs required to protect normal breast tissue from reactive oxygen species (ROS) and the time required for the particles to diffuse to various distances from the lumpectomy wall. Given that cerium has a high atomic number, we took into account the possible inadvertent dose enhancement that could occur due to the photoelectric interactions with radiotherapy photons. To protect against a typical MammoSite treatment fraction of 3.4Gy, 5ng·g(-1) of CONPs is required to scavenge hydroxyl radicals and hydrogen peroxide. Using 2nm sized NPs, with an initial concentration of 1mg·g(-1), we found that 2-10days of diffusion is required to obtain desired concentrations of CONPs in regions 1-2cm away from the lumpectomy wall. The resultant dose enhancement factor (DEF) is less than 1.01 under such conditions. Our results predict that CONPs can be employed for radioprotection during APBI using a new design in which balloon applicators are coated with the NPs for sustained/controlled in-situ release from within the lumpectomy cavity. PMID:27053452

  3. Preparation of mesoporous cerium oxide templated by tri-block copolymer for solid oxide fuel cell

    International Nuclear Information System (INIS)

    Mesoporous structured CeO2 with high specific surface area was synthesized at ambient temperature in this study. The synthesis of this material was accomplished using a tri-block copolymer as the organic supermolecular template and the cerium nitrate hexahydrate as the inorganic precursor. X-ray diffraction, nitrogen adsorption and desorption isotherms and transmission electron microscopy have been used to characterize the mesoporous structure. The nitrogen adsorption and desorption isotherms analysis indicates that the average pore size is 3.5 and 3.4 nm and the specific surface area is 155 and 103 m2/g for the samples calcined at 523 and 723 K, respectively

  4. Untangling the biological effects of cerium oxide nanoparticles: the role of surface valence states

    Science.gov (United States)

    Pulido-Reyes, Gerardo; Rodea-Palomares, Ismael; Das, Soumen; Sakthivel, Tamil Selvan; Leganes, Francisco; Rosal, Roberto; Seal, Sudipta; Fernández-Piñas, Francisca

    2015-10-01

    Cerium oxide nanoparticles (nanoceria; CNPs) have been found to have both pro-oxidant and anti-oxidant effects on different cell systems or organisms. In order to untangle the mechanisms which underlie the biological activity of nanoceria, we have studied the effect of five different CNPs on a model relevant aquatic microorganism. Neither shape, concentration, synthesis method, surface charge (ζ-potential), nor nominal size had any influence in the observed biological activity. The main driver of toxicity was found to be the percentage of surface content of Ce3+ sites: CNP1 (58%) and CNP5 (40%) were found to be toxic whereas CNP2 (28%), CNP3 (36%) and CNP4 (26%) were found to be non-toxic. The colloidal stability and redox chemistry of the most and least toxic CNPs, CNP1 and CNP2, respectively, were modified by incubation with iron and phosphate buffers. Blocking surface Ce3+ sites of the most toxic CNP, CNP1, with phosphate treatment reverted toxicity and stimulated growth. Colloidal destabilization with Fe treatment only increased toxicity of CNP1. The results of this study are relevant in the understanding of the main drivers of biological activity of nanoceria and to define global descriptors of engineered nanoparticles (ENPs) bioactivity which may be useful in safer-by-design strategies of nanomaterials.

  5. Cytotoxicity and antibacterial activity of gold-supported cerium oxide nanoparticles

    Directory of Open Access Journals (Sweden)

    Suresh Babu K

    2014-11-01

    Full Text Available K Suresh Babu,1,† M Anandkumar,1,† TY Tsai,2 TH Kao,2 B Stephen Inbaraj,2 BH Chen2,31Centre for Nano Sciences and Technology, Madanjeet School of Green Energy Technologies, Pondicherry University, Kalapet, India; 2Department of Food Science, 3Graduate Institute of Medicine, Fu Jen University, Taipei, Taiwan†These authors contributed equally to this workBackground: Cerium oxide nanoparticles (CeO2 have been shown to be a novel therapeutic in many biomedical applications. Gold (Au nanoparticles have also attracted widespread interest due to their chemical stability and unique optical properties. Thus, decorating Au on CeO2 nanoparticles would have potential for exploitation in the biomedical field. Methods: In the present work, CeO2 nanoparticles synthesized by a chemical combustion method were supported with 3.5% Au (Au/CeO2 by a deposition-precipitation method. The as-synthesized Au, CeO2, and Au/CeO2 nanoparticles were evaluated for antibacterial activity and cytotoxicity in RAW 264.7 normal cells and A549 lung cancer cells. Results: The as-synthesized nanoparticles were characterized by X-ray diffraction, scanning and transmission electron microscopy, and ultraviolet-visible measurements. The X-ray diffraction study confirmed the formation of cubic fluorite-structured CeO2 nanoparticles with a size of 10 nm. All synthesized nanoparticles were nontoxic towards RAW 264.7 cells at doses of 0–1,000 µM except for Au at >100 µM. For A549 cancer cells, Au/CeO2 had the highest inhibitory effect, followed by both Au and CeO2 which showed a similar effect at 500 and 1,000 µM. Initial binding of nanoparticles occurred through localized positively charged sites in A549 cells as shown by a shift in zeta potential from positive to negative after 24 hours of incubation. A dose-dependent elevation in reactive oxygen species indicated that the pro-oxidant activity of the nanoparticles was responsible for their cytotoxicity towards A549 cells. In

  6. Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III) on short term effects to the green algae Chlamydomonas reinhardtii

    International Nuclear Information System (INIS)

    Highlights: • Phosphate-dispersed CeO2 NP did not affect photosynthetic yield in C. reinhardtii. • Agglomerated CeO2 NP slightly decreased photosynthetic yield. • Cerium(III) was shown to affect photosynthetic yield and intracellular ROS level. • Slight effects of CeO2 NP were caused by dissolved Ce3+ ions present in suspensions. • Wild type and cell wall free mutant of C. reinhardtii showed the same sensitivity. - Abstract: Cerium oxide nanoparticles (CeO2 NP) are increasingly used in industrial applications and may be released to the aquatic environment. The fate of CeO2 NP and effects on algae are largely unknown. In this study, the short term effects of CeO2 NP in two different agglomeration states on the green algae Chlamydomonas reinhardtii were examined. The role of dissolved cerium(III) on toxicity, its speciation and the dissolution of CeO2 NP were considered. The role of cell wall of C. reinhardtii as a barrier and its influence on the sensitivity to CeO2 NP and cerium(III) was evaluated by testing both, the wild type and the cell wall free mutant of C. reinhardtii. Characterization showed that CeO2 NP had a surface charge of ∼0 mV at physiological pH and agglomerated in exposure media. Phosphate stabilized CeO2 NP at pH 7.5 over 24 h. This effect was exploited to test CeO2 NP dispersed in phosphate with a mean size of 140 nm and agglomerated in absence of phosphate with a mean size of 2000 nm. The level of dissolved cerium(III) in CeO2 NP suspensions was very low and between 0.1 and 27 nM in all tested media. Exposure of C. reinhardtii to Ce(NO3)3 decreased the photosynthetic yield in a concentration dependent manner with EC50 of 7.5 ± 0.84 μM for wild type and EC50 of 6.3 ± 0.53 μM for the cell wall free mutant. The intracellular level of reactive oxygen species (ROS) increased upon exposure to Ce(NO3)3 with effective concentrations similar to those inhibiting photosynthesis. The agglomerated CeO2 NP caused a slight decrease of

  7. Influence of agglomeration of cerium oxide nanoparticles and speciation of cerium(III) on short term effects to the green algae Chlamydomonas reinhardtii

    Energy Technology Data Exchange (ETDEWEB)

    Röhder, Lena A. [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland); ETH-Zurich, Institute of Biogeochemistry and Pollutant Dynamics, Zürich 8092 (Switzerland); Brandt, Tanja [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland); Sigg, Laura [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland); ETH-Zurich, Institute of Biogeochemistry and Pollutant Dynamics, Zürich 8092 (Switzerland); Behra, Renata, E-mail: Renata.behra@eawag.ch [Eawag, Swiss Federal Institute of Aquatic Science and Technology, Department of Environmental Toxicology, Dübendorf 8600 (Switzerland)

    2014-07-01

    Highlights: • Phosphate-dispersed CeO₂ NP did not affect photosynthetic yield in C. reinhardtii. • Agglomerated CeO₂ NP slightly decreased photosynthetic yield. • Cerium(III) was shown to affect photosynthetic yield and intracellular ROS level. • Slight effects of CeO₂ NP were caused by dissolved Ce³⁺ ions present in suspensions. • Wild type and cell wall free mutant of C. reinhardtii showed the same sensitivity. - Abstract: Cerium oxide nanoparticles (CeO₂ NP) are increasingly used in industrial applications and may be released to the aquatic environment. The fate of CeO₂ NP and effects on algae are largely unknown. In this study, the short term effects of CeO₂ NP in two different agglomeration states on the green algae Chlamydomonas reinhardtii were examined. The role of dissolved cerium(III) on toxicity, its speciation and the dissolution of CeO₂ NP were considered. The role of cell wall of C. reinhardtii as a barrier and its influence on the sensitivity to CeO₂ NP and cerium(III) was evaluated by testing both, the wild type and the cell wall free mutant of C. reinhardtii. Characterization showed that CeO₂ NP had a surface charge of ~0 mV at physiological pH and agglomerated in exposure media. Phosphate stabilized CeO₂ NP at pH 7.5 over 24 h. This effect was exploited to test CeO₂ NP dispersed in phosphate with a mean size of 140 nm and agglomerated in absence of phosphate with a mean size of 2000 nm. The level of dissolved cerium(III) in CeO₂ NP suspensions was very low and between 0.1 and 27 nM in all tested media. Exposure of C. reinhardtii to Ce(NO₃)₃ decreased the photosynthetic yield in a concentration dependent manner with EC₅₀ of 7.5 ± 0.84 μM for wild type and EC₅₀ of 6.3 ± 0.53 μM for the cell wall free mutant. The intracellular level of reactive oxygen species (ROS) increased upon exposure to Ce(NO₃)₃ with effective concentrations similar to those inhibiting photosynthesis. The agglomerated Ce

  8. Reaction chemistry of cerium

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-01-01

    It is truly ironic that a synthetic organic chemist likely has far greater knowledge of the reaction chemistry of cerium(IV) than an inorganic colleague. Cerium(IV) reagents have long since been employed as oxidants in effecting a wide variety of organic transformations. Conversely, prior to the late 1980s, the number of well characterized cerium(IV) complexes did not extend past a handful of known species. Though in many other areas, interest in the molecular chemistry of the 4f-elements has undergone an explosive growth over the last twenty years, the chemistry of cerium(IV) has for the most part been overlooked. This report describes reactions of cerium complexes and structure.

  9. Real-time observation of dynamic process of oxygen vacancy migration in cerium oxides under electric field

    International Nuclear Information System (INIS)

    The dynamic process of oxygen vacancy migration driven by the external electric field is directly observed at atomic scale in the cerium oxides (CeO2) thin film by in-situ transmission electron microscopy method. When a bias voltage of a proper value is applied across the CeO2 film, the oxygen vacancies are formed near the interface of CeO2/anode, followed by their migration along the direction of the external electric field. The structural modulation occurs in the [110] zone axis due to the ordering of oxygen vacancies. The migration of oxygen vacancies results in the reversible structural transformation, i.e., releasing and storing oxygen processes in CeO2, which is of great significance for the ionic and electronic applications of the cerium oxides materials, such as oxygen pump, gas sensor, resistive random access memory, etc

  10. Real-time observation of dynamic process of oxygen vacancy migration in cerium oxides under electric field

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaomin; Qi, Kuo; Sun, Muhua; Huang, Qianming; Xu, Zhi, E-mail: xuzhi@iphy.ac.cn, E-mail: xdbai@iphy.ac.cn; Wang, Wenlong [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Bai, Xuedong, E-mail: xuzhi@iphy.ac.cn, E-mail: xdbai@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2015-11-23

    The dynamic process of oxygen vacancy migration driven by the external electric field is directly observed at atomic scale in the cerium oxides (CeO{sub 2}) thin film by in-situ transmission electron microscopy method. When a bias voltage of a proper value is applied across the CeO{sub 2} film, the oxygen vacancies are formed near the interface of CeO{sub 2}/anode, followed by their migration along the direction of the external electric field. The structural modulation occurs in the [110] zone axis due to the ordering of oxygen vacancies. The migration of oxygen vacancies results in the reversible structural transformation, i.e., releasing and storing oxygen processes in CeO{sub 2}, which is of great significance for the ionic and electronic applications of the cerium oxides materials, such as oxygen pump, gas sensor, resistive random access memory, etc.

  11. Real-time observation of dynamic process of oxygen vacancy migration in cerium oxides under electric field

    Science.gov (United States)

    Li, Xiaomin; Qi, Kuo; Sun, Muhua; Huang, Qianming; Xu, Zhi; Wang, Wenlong; Bai, Xuedong

    2015-11-01

    The dynamic process of oxygen vacancy migration driven by the external electric field is directly observed at atomic scale in the cerium oxides (CeO2) thin film by in-situ transmission electron microscopy method. When a bias voltage of a proper value is applied across the CeO2 film, the oxygen vacancies are formed near the interface of CeO2/anode, followed by their migration along the direction of the external electric field. The structural modulation occurs in the [110] zone axis due to the ordering of oxygen vacancies. The migration of oxygen vacancies results in the reversible structural transformation, i.e., releasing and storing oxygen processes in CeO2, which is of great significance for the ionic and electronic applications of the cerium oxides materials, such as oxygen pump, gas sensor, resistive random access memory, etc.

  12. Preparation and properties of a cerium-containing hydroxyapatite coating on commercially pure titanium by micro-arc oxidation

    Institute of Scientific and Technical Information of China (English)

    HUANG Yong; WANG Yingjun; NING Chengyun; NAN Kaihui; HAN Yong

    2008-01-01

    A porous cerium-containing hydroxyapatite coating on commercially pure titanium was prepared by micro-arc oxidation (MAO) in an electrolytic solution containing calcium acetate, β-glycerol phosphate disodium salt pentahydrate (β-GP), and cerium nitrate. The thickness, phase, composition morphology, and biocompatibility of the oxide coating were characterized by X-ray diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM) with energy dispersive X-ray spectrometer (EDS), and cell culture. The thickness of the MAO film is about 15-25μm, and the coating is porous and uneven, without any apparent interface to the titanium substrates. The results of XRD and EDS show that the porous coating is made up of hydroxyapatite (HA) film containing Ce. The favorable osteoblast cell affinity makes the Ce-HA film have a good biocompatibility. The Ce-HA film is expected to have significant medical applications as dental implants and artificial bone joints.

  13. Structural and morphological evolution of cerium oxide thin film on silicon prepared by metal-organic decomposition route

    International Nuclear Information System (INIS)

    Thin film of cerium oxide (CeO2) were prepared on silicon (Si) substrate by metal organic decomposition route. 0.25 M of cerium (III) acetylacetonate (acac) was used as starting materials with the addition of methanol and acetic acid as solvents. Oxide conversion of the film by thermal treatment was conducted at temperature ranging from 400 degree Celsius to 1000 degree Celsius for 15 min in argon ambient. X-ray diffraction (XRD) analysis utilizing Cukα radiation (Model Brukker DiffracPlus), Filmetrics system measurement, field emission scanning electron microscope (FESEM) (Model Zeiss Supra 35 VP FESEM) and atomic force microscopy (AFM) (Model SII Nanonavi) were employed to characterize the phase formed and morphologies of the film produced. (author)

  14. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders prepared by the co-precipitation process

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jian-Chih [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Chen, Wen-Cheng [School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China); Tien, Yin-Chun [Department of Orthopaedics, Kaohsiung Medical University Hospital, Kaohsiung 807, Taiwan (China); Shih, Chi-Jen, E-mail: cjshih@kmu.edu.t [Department of Fragrance and Cosmetics Science, Kaohsiung Medical University, 100 Shi-Chuan1st Road, Kaohsiung 80708, Taiwan (China)

    2010-04-30

    Cerium oxide nanocrystallites were synthesized by a co-precipitation process at a relatively low temperature, using cerium (III) nitrate as the starting material in a water solution with pH in the range of 8-9. The effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K, by XRD analysis. When calcined at temperatures from 473 to 1273 K, face-centered cubic phase crystallization was observed by XRD. The crystallite size of the cerium oxide increased from 12.0 to 48 nm as the calcining temperature increased from 473 to 1273 K, in the pH range 8-9. The activation energy for the growth of cerium oxide nanoparticles was found to have very low values of 17.5 kJ/mol for pH = 8 and 16.0 kJ/mol for pH = 9.

  15. Effect of calcination temperature on the crystallite growth of cerium oxide nano-powders prepared by the co-precipitation process

    International Nuclear Information System (INIS)

    Cerium oxide nanocrystallites were synthesized by a co-precipitation process at a relatively low temperature, using cerium (III) nitrate as the starting material in a water solution with pH in the range of 8-9. The effect of calcination temperature on the crystallite growth of cerium oxide nano-powders was investigated by X-ray diffraction, transmission electron microscopy and electron diffraction. The crystallization temperature of the cerium oxide powders was estimated to be about 273 K, by XRD analysis. When calcined at temperatures from 473 to 1273 K, face-centered cubic phase crystallization was observed by XRD. The crystallite size of the cerium oxide increased from 12.0 to 48 nm as the calcining temperature increased from 473 to 1273 K, in the pH range 8-9. The activation energy for the growth of cerium oxide nanoparticles was found to have very low values of 17.5 kJ/mol for pH = 8 and 16.0 kJ/mol for pH = 9.

  16. Mixtures of room temperature ionic liquid/ethanol solutions as electrolytic media for cerium oxide thin layer electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Lair, V., E-mail: virginie-lair@chimie-paristech.f [Laboratoire d' Electrochimie, Chimie des Interfaces et Modelisation pour l' Energie, LECIME, CNRS UMR 7575-Chimie Paristech (ENSCP)-Paris, 11, rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Sirieix-Plenet, J.; Gaillon, L.; Rizzi, C. [UPMC University Paris 06, UMR 7195, Laboratoire de Physicochimie des Electrolytes, Colloides et Sciences Analytiques (PECSA), F-75005 Paris (France); CNRS, UMR 7195, PECSA, F-75005 Paris (France); ESPCI, UMR 7195, PECSA, F-75005 Paris (France); Ringuede, A. [Laboratoire d' Electrochimie, Chimie des Interfaces et Modelisation pour l' Energie, LECIME, CNRS UMR 7575-Chimie Paristech (ENSCP)-Paris, 11, rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France)

    2010-12-30

    A cerium oxide thin layer was electrodeposited onto stainless steel, using mixed room temperature ionic liquid (the 1-methyl-3-butylimidazolium bis(trifluoromethyl sulfonyl)imide)/ethanol solutions, as electrolytic medium. The hydrophobic ionic liquid content is one of the main parameters in the morphology control influencing the ceria growth rate and crystallinity. Micro-nano structural properties and electrical behaviour are presented, using XRD, SEM/EDS and impedance spectroscopy, as a function of electrodeposition conditions.

  17. Mixtures of room temperature ionic liquid/ethanol solutions as electrolytic media for cerium oxide thin layer electrodeposition

    International Nuclear Information System (INIS)

    A cerium oxide thin layer was electrodeposited onto stainless steel, using mixed room temperature ionic liquid (the 1-methyl-3-butylimidazolium bis(trifluoromethyl sulfonyl)imide)/ethanol solutions, as electrolytic medium. The hydrophobic ionic liquid content is one of the main parameters in the morphology control influencing the ceria growth rate and crystallinity. Micro-nano structural properties and electrical behaviour are presented, using XRD, SEM/EDS and impedance spectroscopy, as a function of electrodeposition conditions.

  18. Study on recovering directly the commercial cerium oxide and total of residue rare earths from Dongpao bastnasite concentrate

    International Nuclear Information System (INIS)

    A technology for decomposition roasting and sequential leaching processes of Dong Pao bastnasite concentrate to recover directly commercial cerium oxide and total of residue rare earth elements from the leaching solution of the roasted product have been investigated. The bastnasite concentrate is initially roasted at temperature range of 600 - 650 degC and for time of 4 hrs in order to decompose and convert the hardly soluble carbonate forms of ore into easily soluble oxide. The roasted solid is then leached with sulfuric acid solution of 6N at 60 degC for 4 hrs to convert rare earths in oxide and fluoride form into rare earth sulfate. The recovery yield of rare earths of these stages is more than 95%. The attention has especially been paid on recovering directly the commercial cerium oxide and total of residue rare earth element from the above leaching solution. Complex ions of CeSO42+, Ce(SO4)2, Ce(SO4)32- and Ce(SO4)44- exist in aqueous solution of cerium (IV) sulfate. Based on the property, the method of ion - sieve with DOWEX cation resin column has been applied to estimating separation of the ceric complex anions from Ln(III). The survey showed that most of the ceric complex anions are separated from total of residue rare earths. The latter which are absorbed in the cation column are recovered by elution of HCl of 4N. The recovery yield of cerium can only be reached 20% but the purity of that is very high, can be reached 99.6%. About 5 kg of CeO2 of high grade and 5 kg of TREO of commercial specification have been produced. (author)

  19. Effect of impurities (carbon and manganese) on iron oxidation at high temperature: impurities-rare earth element (cerium) interactions

    International Nuclear Information System (INIS)

    After oxidation of ceria coated iron specimens, (T = 700 C, pO2 = 0.04 Pa), cerium is located inside the wustite matrix as a CeFeO3 phase. The CeFeO3 formation is attributed to an oxido-reduction process between the CeO2 coating and the FeO nuclei at the beginning of the oxidation test. On ceria coated Fe-Mn-C steel samples, carbon and manganese impurities have a strong influence on the oxidation rate and on the rare-earth element location. After the coated steel oxidation, cerium is located at the scale-gas interface as a CeO2 phase and it is not incorporated inside the iron oxide scale. The role of each impurity is established : manganese prevents the formation of CeFeO3 because no contact between the reducing FeO germs and the oxidant CeO2 phase is permitted. This lack of contact is due to the high vapor pressure of manganese oxides which evaporate at the beginning of the reaction and promote the CeO2 coating spallation. On the other hand, carbon does not hinder the CeFeO3 formation but it always favours the wustite scale spallation after some hours oxidation, due to the carbon segregation in the metal at the steel-oxide interface. (orig.)

  20. A nanostructured cerium oxide film-based immunosensor for mycotoxin detection

    International Nuclear Information System (INIS)

    Rabbit-immunoglobulin antibodies (r-IgGs) and bovine serum albumin (BSA) have been immobilized onto sol-gel-derived nanostructured cerium oxide (nanoCeO2) film fabricated onto an indium-tin-oxide (ITO) coated glass plate to detect ochratoxin-A (OTA). Broad reflection planes obtained in x-ray diffraction (XRD) patterns reveal the formation of CeO2 nanostructures. Electrochemical studies reveal that nanoCeO2 particles provide an increased electroactive surface area for loading of r-IgGs with desired orientation, resulting in enhanced electron communication between r-IgGs and electrode. BSA/r-IgGs/nano CeO2/ITO immunoelectrode exhibits improved characteristics such as linear range (0.5-6 ng dl-1), low detection limit (0.25 ng dl-1), fast response time (30 s) and high sensitivity (1.27 μA ng-1 dl-1 cm-2). The high value of the association constant (Ka, 0.9 x 1011 l mol-1) indicates the high affinity of the BSA/r-IgGs/nanoCeO2/ITO immunoelectrode to OTA.

  1. Structure and properties of cerium oxides in bulk and nanoparticulate forms

    Energy Technology Data Exchange (ETDEWEB)

    Gangopadhyay, Shruba [NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826 (United States); Department of Chemistry, University of Central Florida, 4111 Libra Drive, PS 255, Orlando, FL 32826 (United States); Frolov, Dmitry D. [NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826 (United States); Department of Chemistry, Moscow M.V. Lomonosov State University, Leninskiye Gory, Moscow 119991 (Russian Federation); Masunov, Artëm E., E-mail: amasunov@ucf.edu [NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826 (United States); Department of Chemistry, University of Central Florida, 4111 Libra Drive, PS 255, Orlando, FL 32826 (United States); Department of Physics, University of Central Florida, 4111 Libra Drive, PS 430, Orlando, FL 32826 (United States); Seal, Sudipta [Advanced Materials Processing and Analysis Center, University of Central Florida, 12760 Pegasus Drive, ENG1 381, Orlando, FL 32816 (United States); Department of Materials Science and Engineering, University of Central Florida, 12760 Pegasus Drive, ENG1 207, FL 32816 (United States); College of Medicine, University of Central Florida, 6850 Lake Nona Blvd, Orlando, FL 32827 (United States); NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL 32826 (United States)

    2014-01-25

    The experimental and computational studies on the cerium oxide nanoparticles, as well as stoichiometric phases of bulk ceria are reviewed. Based on structural similarities of these phases in hexagonal aspect, electroneutral and non-polar pentalayers are identified as building blocks of type A sesquioxide structure. The idealized core/shell structure of the ceria nanoparticles is described as dioxide core covered by a single pentalayer of sesquioxide, which explains the exceptional stability of subsurface vacancies in nanoceria. The density functional theory (DFT) predictions of the lattice parameters and elastic moduli for the Ce(IV) and Ce(III) oxides at the hybrid DFT level are also presented. The calculated values for both compounds agree with available experimental data and allow predicting changes in the lattice parameter with decreasing size of the nanoparticles. The lattice parameter is calculated as equilibrium between contraction of sesquioxide structure in the core, and expansion of dioxide structure in the shell of the nanoparticle. This is consistent with available XRD data on ceria NPs obtained in mild aqueous conditions. The core/shell model, however, breaks down when applied to the size dependence of lattice parameter in NPs obtained by the laser ablation techniques.

  2. Structure and properties of cerium oxides in bulk and nanoparticulate forms

    International Nuclear Information System (INIS)

    The experimental and computational studies on the cerium oxide nanoparticles, as well as stoichiometric phases of bulk ceria are reviewed. Based on structural similarities of these phases in hexagonal aspect, electroneutral and non-polar pentalayers are identified as building blocks of type A sesquioxide structure. The idealized core/shell structure of the ceria nanoparticles is described as dioxide core covered by a single pentalayer of sesquioxide, which explains the exceptional stability of subsurface vacancies in nanoceria. The density functional theory (DFT) predictions of the lattice parameters and elastic moduli for the Ce(IV) and Ce(III) oxides at the hybrid DFT level are also presented. The calculated values for both compounds agree with available experimental data and allow predicting changes in the lattice parameter with decreasing size of the nanoparticles. The lattice parameter is calculated as equilibrium between contraction of sesquioxide structure in the core, and expansion of dioxide structure in the shell of the nanoparticle. This is consistent with available XRD data on ceria NPs obtained in mild aqueous conditions. The core/shell model, however, breaks down when applied to the size dependence of lattice parameter in NPs obtained by the laser ablation techniques

  3. Gold-supported cerium-doped NiOx catalysts for water oxidation

    Science.gov (United States)

    Ng, Jia Wei Desmond; García-Melchor, Max; Bajdich, Michal; Chakthranont, Pongkarn; Kirk, Charlotte; Vojvodic, Aleksandra; Jaramillo, Thomas F.

    2016-05-01

    The development of high-performance catalysts for the oxygen-evolution reaction (OER) is paramount for cost-effective conversion of renewable electricity to fuels and chemicals. Here we report the significant enhancement of the OER activity of electrodeposited NiOx films resulting from the combined effects of using cerium as a dopant and gold as a metal support. This NiCeOx–Au catalyst delivers high OER activity in alkaline media, and is among the most active OER electrocatalysts yet reported. On the basis of experimental observations and theoretical modelling, we ascribe the activity to a combination of electronic, geometric and support effects, where highly active under-coordinated sites at the oxide support interface are modified by the local chemical binding environment and by doping the host Ni oxide with Ce. The NiCeOx–Au catalyst is further demonstrated in a device context by pairing it with a nickel–molybdenum hydrogen evolution catalyst in a water electrolyser, which delivers 50 mA consistently at 1.5 V over 24 h of continuous operation.

  4. Evaluation of cerium oxide coated Cu cermets as inert anodes for aluminum electrowinning

    Energy Technology Data Exchange (ETDEWEB)

    1992-08-01

    Cu/NiFe{sub 2}O{sub 4} cermets were evaluated, with and without an in-situ deposited CEROX (TM; cerium oxide) coating, in 100 h laboratory A1 electrowinning tests. Bath ratio and current density were varied between tests and corrosion was determined by contamination of the aluminum and cryolite by cermet components (Cu, Fe, and Ni). Higher bath ratios of 1.5 to 1.6 led to less corrosion and thicker CEROX coatings. Lower current densities led to slightly less corrosion but much less oxidation of the Cu cermet substrate. At identical test conditions, the corrosion of the CEROX coated cermets was 1/7 that of an uncoated cermet. Corrosion was increased in CEROX coated cermets tested under unsaturated alumina conditions. The electrical conductivity of the CEROX coating was measured to be {approximately}0.2 ohm{sup {minus}1}cm{sup {minus}1}, resulting in a slight voltage penalty, depending on the thickness of the coating.

  5. Freshwater dispersion stability of PAA-stabilised cerium oxide nanoparticles and toxicity towards Pseudokirchneriella subcapitata

    Energy Technology Data Exchange (ETDEWEB)

    Booth, Andy, E-mail: andy.booth@sintef.no [SINTEF Materials and Chemistry, Trondheim N-7465 (Norway); Størseth, Trond [SINTEF Materials and Chemistry, Trondheim N-7465 (Norway); Altin, Dag [BioTrix, Trondheim N-7022 (Norway); Fornara, Andrea; Ahniyaz, Anwar [German Federal Institute for Risk Assessment (BfR), Department of Product Safety, Berlin (Germany); Jungnickel, Harald; Laux, Peter; Luch, Andreas [SP Chemistry, Materials and Surfaces, Drottning Kristinas vag 45, SE-11686 Stockholm (Sweden); Sørensen, Lisbet [SINTEF Materials and Chemistry, Trondheim N-7465 (Norway)

    2015-02-01

    An aqueous dispersion of poly (acrylic acid)-stabilised cerium oxide (CeO{sub 2}) nanoparticles (PAA-CeO{sub 2}) was evaluated for its stability in a range of freshwater ecotoxicity media (MHRW, TG 201 and M7), with and without natural organic matter (NOM). In a 15 day dispersion stability study, PAA-CeO{sub 2} did not undergo significant aggregation in any media type. Zeta potential varied between media types and was influenced by PAA-CeO{sub 2} concentration, but remained constant over 15 days. NOM had no influence on PAA-CeO{sub 2} aggregation or zeta potential. The ecotoxicity of the PAA-CeO{sub 2} dispersion was investigated in 72 h algal growth inhibition tests using the freshwater microalgae Pseudokirchneriella subcapitata. PAA-CeO{sub 2} EC{sub 50} values for growth inhibition (GI; 0.024 mg/L) were 2–3 orders of magnitude lower than pristine CeO{sub 2} EC{sub 50} values reported in the literature. The concentration of dissolved cerium (Ce{sup 3+}/Ce{sup 4+}) in PAA-CeO{sub 2} exposure suspensions was very low, ranging between 0.5 and 5.6 μg/L. Free PAA concentration in the exposure solutions (0.0096–0.0384 mg/L) was significantly lower than the EC{sub 10} growth inhibition (47.7 mg/L) value of pure PAA, indicating that free PAA did not contribute to the observed toxicity. Elemental analysis indicated that up to 38% of the total Cerium becomes directly associated with the algal cells during the 72 h exposure. TOF-SIMS analysis of algal cell wall compounds indicated three different modes of action, including a significant oxidative stress response to PAA-CeO{sub 2} exposure. In contrast to pristine CeO{sub 2} nanoparticles, which rapidly aggregate in standard ecotoxicity media, PAA-stabilised CeO{sub 2} nanoparticles remain dispersed and available to water column species. Interaction of PAA with cell wall components, which could be responsible for the observed biomarker alterations, could not be excluded. This study indicates that the increased

  6. Interactive effect of cerium and aluminum on the ignition point and the oxidation resistance of magnesium alloy

    International Nuclear Information System (INIS)

    This paper focused on the interactive effect of cerium (Ce) addition and aluminum (Al) content in magnesium alloy on ignition point and oxidation resistance. Ce content played an important role in improving the oxidation resistance of Mg alloy. Ignition point ascended with increasing Ce content. 0.25 wt% Ce content in Mg alloys could greatly improve tightness of the oxide film of Mg alloys. However, when Ce content in the alloy exceeded its solid solubility, ignition point descended. Furthermore, Al content in the alloy also influenced the ignition point. The higher the Al content was, the lower the ignition point

  7. Electrodeposition of cerium oxide on porous silicon via anodization and enhancement of photoluminescence

    Science.gov (United States)

    Mizuhata, Minoru; Kubo, Yohei; Maki, Hideshi

    2016-02-01

    A porous Si/cerium oxide composite (PSi/CeO2) was synthesized by electrodeposition of CeO2 via anodic oxidation on PSi. The PSi photoluminescence (PL) was enhanced. The anodically oxidized PSi substrates in HF solution had macropores (diameter 2 μm), mesopores (diameter 15 nm), and micropores (diameter less than 4 nm). Emission at 700 nm from microporous PSi (microPSi) was observed under ultraviolet irradiation. Transmission electron microscopy showed that in microPSi/CeO2, the oxide was infiltrated into microPSi by anodization. The deposited amount of CeO2 depended on the reaction time, applied voltage, temperature, and reaction species concentrations in anodization. Emission by microPSi/CeO2 at 650 nm was observed; the PL intensity was higher (about 10-30 times) than that of PSi because of energy transfer from CeO2 to nanosized Si in porous layers produced by HF etching. The lifetime of the PL of microPSi/CeO2 was longer than that of microPSi. Excitation spectra of microPSi/CeO2 at 650 nm and diffuse-reflectance spectra showed that the excitation peak for microPSi/CeO2 was similar to the absorbance of CeO2, and excitation of microPSi/CeO2 gave two peaks, at 3.7 and 4.4 eV; these peaks originated from the absorptions of CeO2 and Si nanocrystals. The PL of PSi was enhanced in microPSi/CeO2 because of efficient energy transfer from CeO2 to the Si nanocrystal.

  8. Lipase immobilized on nanostructured cerium oxide thin film coated on transparent conducting oxide electrode for butyrin sensing

    International Nuclear Information System (INIS)

    Nanostructured cerium oxide (CeO2) thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique with cerium nitrate salt, Ce(NO3)3·6H2O as precursor. Fluorine doped cadmium oxide (CdO:F) thin film prepared using spray pyrolysis technique acts as the TCO film and hence the bare electrode. The structural, morphological and elemental characterizations of the films were carried out using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) respectively. The diffraction peak positions in XRD confirmed the formation of highly crystalline ceria with cubic structure and FE-SEM images showed uniform adherent films with granular morphology. The band gaps of CeO2 and TCO were found to be 3.2 eV and 2.6 eV respectively. Lipase enzyme was physisorbed on the surface of CeO2/TCO film to form the lipase/nano-CeO2/TCO bioelectrode. Sensing studies were carried out using cyclic voltammetry and amperometry, with lipase/nano-CeO2/TCO as working electrode and tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33–1.98 mM) with a lowest detection limit of 2 μM with sharp response time of 5 s and a shelf life of about 6 weeks. -- Graphical abstract: Nanostructured cerium oxide thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique. Fluorine doped cadmium oxide (CdO:F) thin film acts as the TCO film and hence the working electrode. Lipase enzyme was physisorbed on the surface of CeO2/TCO film and hence the lipase/nano-CeO2/TCO bioelectrode has been fabricated. Sensing studies were carried out using cyclic voltammetry and amperometry with tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33–1.98 mM) with a lowest detection limit of 2 μM with sharp response time of 5 s and a shelf life of about 6 weeks. Highlights:

  9. Lipase immobilized on nanostructured cerium oxide thin film coated on transparent conducting oxide electrode for butyrin sensing

    Energy Technology Data Exchange (ETDEWEB)

    Panky, Sreedevi; Thandavan, Kavitha [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Chemical and Biotechnology, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Sivalingam, Durgajanani [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Sethuraman, Swaminathan; Krishnan, Uma Maheswari [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Chemical and Biotechnology, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Jeyaprakash, Beri Gopalakrishnan [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401, Tamil Nadu (India); Rayappan, John Bosco Balaguru, E-mail: rjbosco@ece.sastra.edu [Centre for Nanotechnology and Advanced Biomaterials (CeNTAB), SASTRA University, Thanjavur 613 401, Tamil Nadu (India); School of Electrical and Electronics Engineering, SASTRA University, Thanjavur 613 401, Tamil Nadu (India)

    2013-01-15

    Nanostructured cerium oxide (CeO{sub 2}) thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique with cerium nitrate salt, Ce(NO{sub 3}){sub 3}{center_dot}6H{sub 2}O as precursor. Fluorine doped cadmium oxide (CdO:F) thin film prepared using spray pyrolysis technique acts as the TCO film and hence the bare electrode. The structural, morphological and elemental characterizations of the films were carried out using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) respectively. The diffraction peak positions in XRD confirmed the formation of highly crystalline ceria with cubic structure and FE-SEM images showed uniform adherent films with granular morphology. The band gaps of CeO{sub 2} and TCO were found to be 3.2 eV and 2.6 eV respectively. Lipase enzyme was physisorbed on the surface of CeO{sub 2}/TCO film to form the lipase/nano-CeO{sub 2}/TCO bioelectrode. Sensing studies were carried out using cyclic voltammetry and amperometry, with lipase/nano-CeO{sub 2}/TCO as working electrode and tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33-1.98 mM) with a lowest detection limit of 2 {mu}M with sharp response time of 5 s and a shelf life of about 6 weeks. -- Graphical abstract: Nanostructured cerium oxide thin films were deposited on transparent conducting oxide (TCO) substrate using spray pyrolysis technique. Fluorine doped cadmium oxide (CdO:F) thin film acts as the TCO film and hence the working electrode. Lipase enzyme was physisorbed on the surface of CeO{sub 2}/TCO film and hence the lipase/nano-CeO{sub 2}/TCO bioelectrode has been fabricated. Sensing studies were carried out using cyclic voltammetry and amperometry with tributyrin as substrate. The mediator-free biosensor with nanointerface exhibited excellent linearity (0.33-1.98 mM) with a lowest detection limit of 2 {mu}M with sharp

  10. Electron microscopy investigations of the organization of cerium oxide nanocrystallites and polymers developed in polyvinylpyrrolidone-assisted polyol synthesis process

    Energy Technology Data Exchange (ETDEWEB)

    Horiuchi, Shin, E-mail: s.horiuchi@aist.go.jp; Hanada, Takeshi [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) (Japan); Izu, Noriya; Matsubara, Ichiro [Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) (Japan)

    2012-03-15

    The microstructures and the organization mechanism of cerium oxide (ceria) nanospheres were investigated by transmission electron microscopy. The ceria nanospheres with the diameter of 50-150 nm were produced by the polyol synthesis method with cerium nitrate precursor and with polyvinylpyrrolidone (PVP) used as a protecting agent. Dose-limited observations performed by energy-filtering transmission electron microscopy revealed that the ceria nanospheres were the aggregated products consisting of ceria nanocrystallites {approx}3 nm in size and PVP-derived polymer products. It was found that the ceria nanocrystallites were oriented within the nanospheres by high-resolution transmission electron microscopy and selected-area electron diffraction. Selective adsorption of PVP on the crystal facets of the ceria nanocrystallites was suggested, and the aggregation of the PVP-adsorbed ceria through cross-linking reaction of PVP causes the crystal orientation.

  11. Cerium oxide nanoparticles inhibit the migration and proliferation of gastric cancer by increasing DHX15 expression

    Science.gov (United States)

    Xiao, Yu-Feng; Li, Jian-Mei; Wang, Su-Min; Yong, Xin; Tang, Bo; Jie, Meng-Meng; Dong, Hui; Yang, Xiao-Chao; Yang, Shi-Ming

    2016-01-01

    Gastric cancer is one of the leading causes of tumor-related deaths in the world. Current treatment options do not satisfy doctors and patients, and new therapies are therefore needed. Cerium oxide nanoparticles (CNPs) have been studied as a potential therapeutic approach for treating many diseases. However, their effects on human gastric cancer are currently unknown. Therefore, in this study, we aimed to characterize the effects of CNPs on human gastric cancer cell lines (MKN28 and BGC823). Gastric cancer cells were cocultured with different concentrations of CNPs, and proliferation and migration were measured both in vitro and in vivo. We found that CNPs inhibited the migration of gastric cancer cells when applied at different concentrations, but only a relatively high concentration (10 µg/mL) of CNPs suppressed proliferation. Furthermore, we found that CNPs increased the expression of DHX15 and its downstream signaling pathways. We therefore provide evidence showing that CNPs may be a promising approach to suppress malignant activity of gastric cancer by increasing the expression of DHX15. PMID:27486320

  12. Magnetic behaviors of cerium oxide-based thin films deposited using electrochemical method

    International Nuclear Information System (INIS)

    Zn and Co multi-doped CeO2 thin films have been prepared using an anodic electrochemical method. The structures and magnetic behaviors are characterized by several techniques, in which the oxygen states in the lattice and the absorptive oxygen bonds at the surface are carefully examined. The absorptive oxygen bond is about 50% of the total oxygen bond by using a semi-quantitative method. The value of actual stoichiometry δ' is close to 2. The experimental results indicate that the thin films are of a cerium oxide-based solid solution with few oxygen vacancies in the lattice and many absorptive oxygen bonds at the surface. Week ferromagnetic behaviors were evidenced by observed M—H hysteresis loops at room temperature. Furthermore, an evidence of relative ferromagnetic contributions was revealed by the temperature dependence of magnetization. It is believed that the ferromagnetic contributions exhibited in the M—H loops originate from the absorptive oxygen on the surface rather than the oxygen vacancies in the lattice. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  13. Effects of cerium oxide nanoparticles on soil enzymatic activities and wheat grass nutrients uptake

    Science.gov (United States)

    Li, Biting; Chen, Yirui; Bai, Lingyun; Jacobson, Astrid; Darnault, Christophe

    2015-04-01

    The US National Science Foundation estimated that the use of nanomaterials and nanotechnology would reach a global market value of 1 million this year. Concomitant with the wide applications of nanoparticles is an increasing risk of adverse effects to the environment and human health. As a common nanomaterial used as a fuel catalyst and polish material, cerium (IV) oxide nanoparticles (CeO2 NP) were tested for their potential impact on soil health and plant growth. Through exposure by air, water, and solid deposition, nanoparticles may accumulate in soils and impact agricultural systems. The objectives of this research were to determine whether CeO2 NPs affect the growth of wheat grass and selected soil enzyme activities chose as indicators of soil health. Wheat grass was grown in plant boxes containing CeO2 NPs mixed with agricultural soil at different concentrations. Two control groups were included: one consisting of soil with plants but no CeO2 NPs, and one containing only soil, i.e., no NP or wheat plants added. The plants were grown for 10 weeks and harvested every two weeks in a laboratory under sodium growth lights. At the end of the each growing period, two weeks, soils were assayed for phosphatase, β-glucosidase, and urease activities, and NPK values. Spectrophotometer analyses were used to assess enzyme activities, and NPK values were tested by Clemson Agricultural Center. Wheat yields were estimated by shoot and root lengths and weights.

  14. Characterization of microstructure and catalytic of cerium oxide obtained by colloidal solution; Caracterizacao da microestrutura e da atividade catalitica de oxido de cerio obtido por solucao coloidal

    Energy Technology Data Exchange (ETDEWEB)

    Senisse, C.A.L.; Bergmann, C.P.; Alves, A.K., E-mail: carolinasenisse@hotmail.com [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alege, RS (Brazil). Lab. de Materiais Ceramicos

    2012-07-01

    This study investigated to obtain particles of cerium oxide, for use as catalysts for the combustion of methane using the technique of through polymeric colloidal solution. Obtaining the colloidal system is based on hydrolysis of salts such as cerium acetylacetonate, cerium nitrate in the presence of additives such as polyvinylbutyral (PVB), polyvinylpyrrolidone (PVP) and polyvinyl acetate (PVA), at concentrations of 5, 10 and 15% in aqueous or alcoholic medium. These solutions containing ions of interest were subjected to a heat treatment at 650° C for 30 minutes, with heating rate of 2 ° C/ min. After heat treatment, the fibers were characterized according to their morphology, surface area, crystallinity, weight loss and catalytic activity. Samples obtained from cerium acetylacetonate were more reactive than the cerium nitrate to the combustion of methane, as showed greater conversions and higher temperatures reached during the process, which is of utmost importance since the combustion catalytic methane is used for generating thermal energy. After the reaction with methane, the samples underwent significant change in surface area, probably due to the intensity of combustion reactions of the nitrate and the generation of heat involved in this reaction, which gave rise to coarse particles. During the combustion process using the obtained from particles of cerium acetylacetonate, there was the release of large quantities of nitrogen compared to the results of assays with the particles obtained with cerium nitrate. (author)

  15. Effects of amorphous silica coating on cerium oxide nanoparticles induced pulmonary responses

    Science.gov (United States)

    Ma, Jane; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane; Cohen, Joel M.; Demokritou, Philip; Castranova, Vincent

    2015-01-01

    Recently cerium compounds have been used in a variety of consumer products, including diesel fuel additives, to increase fuel combustion efficiency and decrease diesel soot emissions. However, cerium oxide (CeO2) nanoparticles have been detected in the exhaust, which raises a health concern. Previous studies have shown that exposure of rats to nanoscale CeO2 by intratracheal instillation (IT) induces sustained pulmonary inflammation and fibrosis. In the present study, male Sprague–Dawley rats were exposed to CeO2 or CeO2 coated with a nano layer of amorphous SiO2 (aSiO2/CeO2) by a single IT and sacrificed at various times post-exposure to assess potential protective effects of the aSiO2 coating. The first acellular bronchoalveolar lavage (BAL) fluid and BAL cells were collected and analyzed from all exposed animals. At the low dose (0.15 mg/kg), CeO2 but not aSiO2/CeO2 exposure induced inflammation. However, at the higher doses, both particles induced a dose-related inflammation, cytotoxicity, inflammatory cytokines, matrix metalloproteinase (MMP)-9, and tissue inhibitor of MMP at 1 day post-exposure. Morphological analysis of lung showed an increased inflammation, surfactant and collagen fibers after CeO2 (high dose at 3.5 mg/kg) treatment at 28 days post-exposure. aSiO2 coating significantly reduced CeO2-induced inflammatory responses in the airspace and appeared to attenuate phospholipidosis and fibrosis. Energy dispersive X-ray spectroscopy analysis showed Ce and phosphorous (P) in all particle-exposed lungs, whereas Si was only detected in aSiO2/CeO2-exposed lungs up to 3 days after exposure, suggesting that aSiO2 dissolved off the CeO2 core, and some of the CeO2 was transformed to CePO4 with time. These results demonstrate that aSiO2 coating reduce CeO2-induced inflammation, phospholipidosis and fibrosis. PMID:26210349

  16. Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jane Y.C., E-mail: jym1@cdc.gov [Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505 (United States); Young, Shih-Houng; Mercer, Robert R.; Barger, Mark; Schwegler-Berry, Diane [Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505 (United States); Ma, Joseph K. [School of Pharmacy, West Virginia University, Morgantown, WV 26506 (United States); Castranova, Vincent [Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV 26505 (United States)

    2014-07-15

    Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO{sub 2}) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO{sub 2} on the pulmonary system in a rat model. Specific pathogen-free male Sprague–Dawley rats were exposed to CeO{sub 2} and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO{sub 2} induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO{sub 2} and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ, respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO{sub 2}, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP + CeO{sub 2} were significantly larger than CeO{sub 2} or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP + CeO{sub 2} reflects the combination of DEP-exposure plus CeO{sub 2}-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO{sub 2} induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO{sub 2} in the combined exposure. Using CeO{sub 2} as diesel fuel catalyst may cause health concerns. - Highlights: • DEP induced acute lung inflammation and switched immune response from Th1 to Th2. • DEP induced lung granulomas were not affected by the presence of CeO{sub 2}. • CeO{sub 2} induced sustained lung

  17. Interactive effects of cerium oxide and diesel exhaust nanoparticles on inducing pulmonary fibrosis

    International Nuclear Information System (INIS)

    Cerium compounds have been used as a fuel-borne catalyst to lower the generation of diesel exhaust particles (DEPs), but are emitted as cerium oxide nanoparticles (CeO2) along with DEP in the diesel exhaust. The present study investigates the effects of the combined exposure to DEP and CeO2 on the pulmonary system in a rat model. Specific pathogen-free male Sprague–Dawley rats were exposed to CeO2 and/or DEP via a single intratracheal instillation and were sacrificed at various time points post-exposure. This investigation demonstrated that CeO2 induces a sustained inflammatory response, whereas DEP elicits a switch of the pulmonary immune response from Th1 to Th2. Both CeO2 and DEP activated AM and lymphocyte secretion of the proinflammatory cytokines IL-12 and IFN-γ, respectively. However, only DEP enhanced the anti-inflammatory cytokine IL-10 production in response to ex vivo LPS or Concanavalin A challenge that was not affected by the presence of CeO2, suggesting that DEP suppresses host defense capability by inducing the Th2 immunity. The micrographs of lymph nodes show that the particle clumps in DEP + CeO2 were significantly larger than CeO2 or DEP, exhibiting dense clumps continuous throughout the lymph nodes. Morphometric analysis demonstrates that the localization of collagen in the lung tissue after DEP + CeO2 reflects the combination of DEP-exposure plus CeO2-exposure. At 4 weeks post-exposure, the histological features demonstrated that CeO2 induced lung phospholipidosis and fibrosis. DEP induced lung granulomas that were not significantly affected by the presence of CeO2 in the combined exposure. Using CeO2 as diesel fuel catalyst may cause health concerns. - Highlights: • DEP induced acute lung inflammation and switched immune response from Th1 to Th2. • DEP induced lung granulomas were not affected by the presence of CeO2. • CeO2 induced sustained lung inflammation, phospholipidosis, and fibrosis. • After the combined exposure, CeO2 and

  18. The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice

    Energy Technology Data Exchange (ETDEWEB)

    Cassee, Flemming R., E-mail: flemming.cassee@rivm.nl [National Institute for Public Health and the Environment, PO box 1, 3720 BA Bilthoven (Netherlands); Campbell, Arezoo, E-mail: acampbell@westernu.edu [Western University of Health Sciences, Pomona, CA (United States); Boere, A. John F., E-mail: john.boere@rivm.nl [National Institute for Public Health and the Environment, PO box 1, 3720 BA Bilthoven (Netherlands); McLean, Steven G., E-mail: smclean1@staffmail.ed.ac.uk [BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, Edinburgh (United Kingdom); Duffin, Rodger, E-mail: Rodger.Duffin@ed.ac.uk [MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh (United Kingdom); Krystek, Petra, E-mail: petra.krystek@philips.com [Philips Innovation Services, Eindhoven (Netherlands); Gosens, Ilse, E-mail: Ilse.gosens@rivm.nl [National Institute for Public Health and the Environment, PO box 1, 3720 BA Bilthoven (Netherlands); Miller, Mark R., E-mail: Mark.Miller@ed.ac.uk [BHF/University Centre for Cardiovascular Sciences, University of Edinburgh, Edinburgh (United Kingdom)

    2012-05-15

    Background: Cerium oxide (CeO{sub 2}) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles. Methods: Atherosclerosis-prone apolipoprotein E knockout (ApoE{sup -/-}) mice were exposed by inhalation to diluted exhaust (1.7 mg/m{sup 3}, 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed. Results: Addition of CeO{sub 2} to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6-8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure. Conclusions: These results imply that addition of CeO{sub 2} nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects.

  19. The biological effects of subacute inhalation of diesel exhaust following addition of cerium oxide nanoparticles in atherosclerosis-prone mice

    International Nuclear Information System (INIS)

    Background: Cerium oxide (CeO2) nanoparticles improve the burning efficiency of fuel, however, little is known about health impacts of altered emissions from the vehicles. Methods: Atherosclerosis-prone apolipoprotein E knockout (ApoE−/−) mice were exposed by inhalation to diluted exhaust (1.7 mg/m3, 20, 60 or 180 min, 5 day/week, for 4 weeks), from an engine using standard diesel fuel (DE) or the same diesel fuel containing 9 ppm cerium oxide nanoparticles (DCeE). Changes in hematological indices, clinical chemistry, atherosclerotic burden, tissue levels of inflammatory cytokines and pathology of the major organs were assessed. Results: Addition of CeO2 to fuel resulted in a reduction of the number (30%) and surface area (10%) of the particles in the exhaust, whereas the gaseous co-pollutants were increased (6–8%). There was, however, a trend towards an increased size and complexity of the atherosclerotic plaques following DE exposure, which was not evident in the DCeE group. There were no clear signs of altered hematological or pathological changes induced by either treatment. However, levels of proinflammatory cytokines were modulated in a brain region and liver following DCeE exposure. Conclusions: These results imply that addition of CeO2 nanoparticles to fuel decreases the number of particles in exhaust and may reduce atherosclerotic burden associated with exposure to standard diesel fuel. From the extensive assessment of biological parameters performed, the only concerning effect of cerium addition was a slightly raised level of cytokines in a region of the central nervous system. Overall, the use of cerium as a fuel additive may be a potentially useful way to limit the health effects of vehicle exhaust. However, further testing is required to ensure that such an approach is not associated with a chronic inflammatory response which may eventually cause long-term health effects.

  20. Uptake and Release of Cerium During Fe-Oxide Formation and Transformation in Fe(II) Solutions

    DEFF Research Database (Denmark)

    Nedel, Sorin; Dideriksen, Knud; Christiansen, Bo C.;

    2010-01-01

    of trace components. Further, Fe(II)-Fe(III) (hydr)oxides are redox active. Cerium, a member of the lanthanide family, can be used as an analogue for the tri- and tetra-valent actinides found in radioactive waste, expected to be stored in subsurface repositories. In experiments with ferrihydrite, Ce....... Transmission electron microscopy revealed that it formed discrete nanocrystals of CeO2(s). These results demonstrate that Fe-oxide interaction with radionuclides is likely to depend strongly on the local redox conditions. By analogy with Ce, the trivalent actinides are not expected to be sequestered by...

  1. Influence of the surface pre-treatment of aluminum on the processes of formation of cerium oxides protective films

    Science.gov (United States)

    Andreeva, R.; Stoyanova, E.; Tsanev, A.; Stoychev, D.

    2016-03-01

    It is known that there is special interest in the contemporary investigations on conversion treatment of aluminum aimed at promoting its corrosion stability, which is focused on electrolytes on the basis of salts of metals belonging to the group of rare-earth elements. Their application is especially attractive, as it enables a successful substitution of the presently applied highly efficient, but at the same time toxic Cr6+-containing electrolytes. The present paper presents a study on the influence of the preliminary alkaline activation and acidic de-oxidation of the aluminum surface on the processes of immersion formation of protective cerium oxides films on Al 1050. The results obtained show that their deposition from simple electrolytes (containing only salts of Ce3+ ions) on the Al surface, treated only in alkaline solution, occurs at a higher rate, which leads to preparing thicker oxide films having a better protective ability. In the cases when the formation of oxide films is realized in a complex electrolyte (containing salts of Ce3+ and Cu2+ ions), better results are obtained with respect to the morphology and protective action of cerium oxides film on samples that have been consecutively activated in alkaline solution and deoxidized in acidic solution. Electrochemical investigations were carried out in a model corrosion medium (0.1 M NaCl); it was shown that the cerium protective films, deposited by immersion, have a cathodic character with regard to the aluminum support and inhibit the occurrence of the depolarizing corrosion process -- the reaction of oxygen reduction.

  2. Cerium Oxide Nanoclusters on Graphene/Ru(0001): Intercalation of Oxygen via Spillover.

    Science.gov (United States)

    Novotny, Zbynek; Netzer, Falko P; Dohnálek, Zdenek

    2015-08-25

    Cerium oxide is an important catalytic material known for its ability to store and release oxygen, and as such, it has been used in a range of applications, both as an active catalyst and as a catalyst support. Using scanning tunneling microscopy and Auger electron spectroscopy, we investigated oxygen interactions with CeOx nanoclusters on a complete graphene monolayer-covered Ru(0001) surface at elevated temperatures (600-725 K). Under oxidizing conditions (PO2 = 1 × 10(-7) Torr), oxygen intercalation under the graphene layer is observed. Time dependent studies demonstrate that the intercalation proceeds via spillover of oxygen from CeOx nanoclusters through the graphene (Gr) layer onto the Ru(0001) substrate and extends until the Gr layer is completely intercalated. Atomically resolved images further show that oxygen forms a p(2 × 1) structure underneath the Gr monolayer. Temperature dependent studies yield an apparent kinetic barrier for the intercalation of 1.21 eV. This value correlates well with the theoretically determined value for the reduction of small CeO2 clusters reported previously. At higher temperatures, the intercalation is followed by a slower etching of the intercalated graphene (apparent barrier of 1.60 eV). Vacuum annealing of the intercalated Gr leads to the formation of carbon monoxide, causing etching of the graphene film, demonstrating that the spillover of oxygen is not reversible. In agreement with previous studies, no intercalation is observed on a complete graphene monolayer without CeOx clusters, even in the presence of a large number of point defects. These studies demonstrate that the easily reducible CeOx clusters act as intercalation gateways capable of efficiently delivering oxygen underneath the graphene layer. PMID:26230753

  3. Studies of binary cerium(IV)-praseodymium(IV) and cerium(IV)-terbium(IV) oxides as pigments for ceramic applications

    International Nuclear Information System (INIS)

    It was investigated a series of pigments of general composition Ce1-x Prx O2, and Cex Tby O2, exhibiting radish and brown colors, respectively, and high temperature stability. The pigments were obtained by dissolving appropriate amounts of the pure lanthanide oxides in acids and precipitating the rare earths as mixed oxalates, which were isolated and calcined under air, at 10000 C. X-Ray powder diffractograms were consistent with a cubic structure for the pigments. Magnetic susceptibility measurements, using Gouy method, indicated the presence of Pr(IV) ions in the Ce1-x Prx O2 pigments and of Terbium predominantly as Tb(III) ions in the Ce-tb mixed oxides. A new method, based on suspension of solid samples in PVA-STB gels (STB = sodium tetradecaborate), was employed for the measurements of the electronic spectra of the pigments. The thermal behaviour the pigments was investigated by the calcination of the oxalates in the temperature range of 500 to 1200O C, from 10 to 60 minutes. (author)

  4. Pulmonary toxicity of well-dispersed cerium oxide nanoparticles following intratracheal instillation and inhalation

    Energy Technology Data Exchange (ETDEWEB)

    Morimoto, Yasuo, E-mail: yasuom@med.uoeh-u.ac.jp; Izumi, Hiroto; Yoshiura, Yukiko; Tomonaga, Taisuke; Oyabu, Takako; Myojo, Toshihiko; Kawai, Kazuaki; Yatera, Kazuhiro [University of Occupational and Environmental Health (Japan); Shimada, Manabu; Kubo, Masaru [Hiroshima University (Japan); Yamamoto, Kazuhiro [National Institute of Advanced Industrial Science and Technology (AIST) (Japan); Kitajima, Shinichi [National Sanatorium Hoshizuka Keiaien (Japan); Kuroda, Etsushi [Osaka University, Laboratory of Vaccine Science, WPI Immunology Frontier Research Center (Japan); Kawaguchi, Kenji; Sasaki, Takeshi [National Institute of Advanced Industrial Science and Technology (AIST) (Japan)

    2015-11-15

    We performed inhalation and intratracheal instillation studies of cerium dioxide (CeO{sub 2}) nanoparticles in order to investigate their pulmonary toxicity, and observed pulmonary inflammation not only in the acute and but also in the chronic phases. In the intratracheal instillation study, F344 rats were exposed to 0.2 mg or 1 mg of CeO{sub 2} nanoparticles. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the instillation. In the inhalation study, rats were exposed to the maximum concentration of inhaled CeO{sub 2} nanoparticles (2, 10 mg/m{sup 3}, respectively) for 4 weeks (6 h/day, 5 days/week). The same endpoints as in the intratracheal instillation study were examined from 3 days to 3 months after the end of the exposure. The intratracheal instillation of CeO{sub 2} nanoparticles caused a persistent increase in the total and neutrophil number in BALF and in the concentration of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2, chemokine for neutrophil, and heme oxygenase-1 (HO-1), an oxidative stress marker, in BALF during the observation time. The inhalation of CeO{sub 2} nanoparticles also induced a persistent influx of neutrophils and expression of CINC-1, CINC-2, and HO-1 in BALF. Pathological features revealed that inflammatory cells, including macrophages and neutrophils, invaded the alveolar space in both studies. Taken together, the CeO{sub 2} nanoparticles induced not only acute but also chronic inflammation in the lung, suggesting that CeO{sub 2} nanoparticles have a pulmonary toxicity that can lead to irreversible lesions.

  5. Pulmonary toxicity of well-dispersed cerium oxide nanoparticles following intratracheal instillation and inhalation

    International Nuclear Information System (INIS)

    We performed inhalation and intratracheal instillation studies of cerium dioxide (CeO2) nanoparticles in order to investigate their pulmonary toxicity, and observed pulmonary inflammation not only in the acute and but also in the chronic phases. In the intratracheal instillation study, F344 rats were exposed to 0.2 mg or 1 mg of CeO2 nanoparticles. Cell analysis and chemokines in bronchoalveolar lavage fluid (BALF) were analyzed from 3 days to 6 months following the instillation. In the inhalation study, rats were exposed to the maximum concentration of inhaled CeO2 nanoparticles (2, 10 mg/m3, respectively) for 4 weeks (6 h/day, 5 days/week). The same endpoints as in the intratracheal instillation study were examined from 3 days to 3 months after the end of the exposure. The intratracheal instillation of CeO2 nanoparticles caused a persistent increase in the total and neutrophil number in BALF and in the concentration of cytokine-induced neutrophil chemoattractant (CINC)-1, CINC-2, chemokine for neutrophil, and heme oxygenase-1 (HO-1), an oxidative stress marker, in BALF during the observation time. The inhalation of CeO2 nanoparticles also induced a persistent influx of neutrophils and expression of CINC-1, CINC-2, and HO-1 in BALF. Pathological features revealed that inflammatory cells, including macrophages and neutrophils, invaded the alveolar space in both studies. Taken together, the CeO2 nanoparticles induced not only acute but also chronic inflammation in the lung, suggesting that CeO2 nanoparticles have a pulmonary toxicity that can lead to irreversible lesions

  6. EMISSION REDUCTION FROM A DIESEL ENGINE FUELED BY CERIUM OXIDE NANO-ADDITIVES USING SCR WITH DIFFERENT METAL OXIDES COATED CATALYTIC CONVERTER

    OpenAIRE

    B. JOTHI THIRUMAL; E, JAMES GUNASEKARAN; LOGANATHAN; C.G. Saravanan

    2015-01-01

    This paper reports the results of experimental investigations on the influence of the addition of cerium oxide in nanoparticle form on the major physiochemical properties and the performance of diesel. The fuel is modified by dispersing the catalytic nanoparticle by ultrasonic agitation. The physiochemical properties of sole diesel fuel and modified fuel are tested with ASTM standard procedures. The effects of the additive nanoparticles on the individual fuel properties, the engine performanc...

  7. Fabrication of Al5083 surface composites reinforced by CNTs and cerium oxide nano particles via friction stir processing

    International Nuclear Information System (INIS)

    Highlights: • Using friction stir processing, an effect of CNTs and CeO2 reinforcements on mechanical and corrosion properties of Al5083 alloy is reported. • The strength of Al5083 was increased by 42%, its matrix grain size reduced five times, and hardness was doubled by the incorporation of CNTs-CeO2 mixture in the volume ratio of 75-25 respectively. • Unlike the CNTs, incorporation of nanosized CeO2 particles resulted in remarkable increase in pitting resistance of the alloy. - Abstract: In the present investigation, friction stir processing (FSP) was utilized to incorporate Multi Walled Carbon Nano Tubes (MWCNT) and nanosized cerium oxide particles into the matrix of Al5083 alloy to form surface reinforced composites. The effect of these nanosized reinforcements either separately or in the combined form, on microstructural modification, mechanical properties and corrosion resistance of FSPed Al5083 surface composites was studied. A threaded cylindrical hardened steel tool was used with the rotation speeds of 600 and 800 rpm and travel speeds of 35 and 45 mm/min and a tilt angle of 5°. Mechanical properties and corrosion resistance of FSPed samples were evaluated and compared with the base alloy. The maximum tensile strength and hardness value were achieved for the hybrid composite containing a mixture of CNTs and cerium oxide in the volume ratio of 75-25, respectively, whereas a significant increase in pitting resistance of the base alloy was obtained when cerium oxide alone was incorporated. The corrosion behavior of the samples was investigated by potentiodynamic polarization tests and assessed in term of pitting potential and passivation range. Microstructural analysis carried out by using optical and electron microscopes showed that reinforcements are well dispersed inside the nugget zone (NZ), and remarkable grain refinement is gained. The study was aimed to fabricate surface composites with improved mechanical properties and corrosion resistance

  8. Fabrication of Al5083 surface composites reinforced by CNTs and cerium oxide nano particles via friction stir processing

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, S.A. [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz (Iran, Islamic Republic of); Ranjbar, Khalil, E-mail: k_ranjbar@scu.ac.ir [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz (Iran, Islamic Republic of); Dehmolaei, R. [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University of Ahvaz (Iran, Islamic Republic of); Amirani, A.R. [12th Ghaem Street, Bld. Hashemzadeh, Shahrak Golestan, Tehran (Iran, Islamic Republic of)

    2015-02-15

    Highlights: • Using friction stir processing, an effect of CNTs and CeO{sub 2} reinforcements on mechanical and corrosion properties of Al5083 alloy is reported. • The strength of Al5083 was increased by 42%, its matrix grain size reduced five times, and hardness was doubled by the incorporation of CNTs-CeO{sub 2} mixture in the volume ratio of 75-25 respectively. • Unlike the CNTs, incorporation of nanosized CeO{sub 2} particles resulted in remarkable increase in pitting resistance of the alloy. - Abstract: In the present investigation, friction stir processing (FSP) was utilized to incorporate Multi Walled Carbon Nano Tubes (MWCNT) and nanosized cerium oxide particles into the matrix of Al5083 alloy to form surface reinforced composites. The effect of these nanosized reinforcements either separately or in the combined form, on microstructural modification, mechanical properties and corrosion resistance of FSPed Al5083 surface composites was studied. A threaded cylindrical hardened steel tool was used with the rotation speeds of 600 and 800 rpm and travel speeds of 35 and 45 mm/min and a tilt angle of 5°. Mechanical properties and corrosion resistance of FSPed samples were evaluated and compared with the base alloy. The maximum tensile strength and hardness value were achieved for the hybrid composite containing a mixture of CNTs and cerium oxide in the volume ratio of 75-25, respectively, whereas a significant increase in pitting resistance of the base alloy was obtained when cerium oxide alone was incorporated. The corrosion behavior of the samples was investigated by potentiodynamic polarization tests and assessed in term of pitting potential and passivation range. Microstructural analysis carried out by using optical and electron microscopes showed that reinforcements are well dispersed inside the nugget zone (NZ), and remarkable grain refinement is gained. The study was aimed to fabricate surface composites with improved mechanical properties and

  9. Stability and spinodal decomposition of the solid-solution phase in the ruthenium-cerium-oxide electro-catalyst.

    Science.gov (United States)

    Li, Yanmei; Wang, Xin; Shao, Yanqun; Tang, Dian; Wu, Bo; Tang, Zhongzhi; Lin, Wei

    2015-01-14

    The phase diagram of Ru-Ce-O was calculated by a combination of ab initio density functional theory and thermodynamic calculations. The phase diagram indicates that the solubility between ruthenium oxide and cerium oxide is very low at temperatures below 1100 K. Solid solution phases, if existing under normal experimental conditions, are metastable and subject to a quasi-spinodal decomposition to form a mixture of a Ru-rich rutile oxide phase and a Ce-rich fluorite oxide phase. To study the spinodal decomposition of Ru-Ce-O, Ru0.6Ce0.4O2 samples were prepared at 280 °C and 450 °C. XRD and in situ TEM characterization provide proof of the quasi-spinodal decomposition of Ru0.6Ce0.4O2. The present study provides a fundamental reference for the phase design of the Ru-Ce-O electro-catalyst. PMID:25418197

  10. Mast cells contribute to altered vascular reactivity and ischemia-reperfusion injury following cerium oxide nanoparticle instillation

    OpenAIRE

    Wingard, Christopher J.; WALTERS, DIANNE M.; Cathey, Brook L.; Hilderbrand, Susana C.; Katwa, Pranita; Lin, Sijie; Ke, Pu Chun; Podila, Ramakrishna; Rao, Apparao; Lust, Robert M.; Brown, Jared M.

    2010-01-01

    Cerium oxide (CeO2) represents an important nanomaterial with wide ranging applications. However, little is known regarding how CeO2 exposure may influence pulmonary or systemic inflammation. Furthermore, how mast cells would influence inflammatory responses to a nanoparticle exposure is unknown. We thus compared pulmonary and cardiovascular responses between C57BL/6 and B6.Cg-KitW-sh mast cell deficient mice following CeO2 nanoparticle instillation. C57BL/6 mice instilled with CeO2 exhibited...

  11. Influence of hydroxyl content of binders on rheological properties of cerium-gadolinium oxide (CGO) screen printing inks

    DEFF Research Database (Denmark)

    Marani, Debora; Gadea, Christophe; Hjelm, Johan;

    2015-01-01

    The influence of hydroxyl content of binders on rheological properties of screen printing inks is investigated. The actual amount of hydroxyl groups is correlated to the level of hyper-entanglement that characterizes the binders in solution. Three of the most used binders (ethyl cellulose, and two...... vinyl resins) were selected and characterized in solution via viscosimetry method. A high degree of hyper-entanglement was observed for ethyl cellulose polymers, whereas a mitigated effect characterized the two vinyl resins. Cerium-gadolinium oxides (CGO)-based inks, prepared using the selected binders...

  12. Synthesis of β-SiC/SiO_2 core-shell nanowires with the assistance of cerium oxide

    Institute of Scientific and Technical Information of China (English)

    于伟鹏; 郑瑛; 杨娥; 邱健斌; 兰瑞芳

    2010-01-01

    The β-SiC/SiO2 core-shell nanowires with the "stem-and-node" structure were synthesized in the presence of cerium oxide by the carbothermal reduction of the starch-SiO2 hybrids gel.The samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM) and energy-dispersed X-ray(EDX).The results showed that the nanowires consisted of a 20-35 nm diameter crystalline β-SiC core wrapped with a 2-5 n...

  13. Cerium oxide coated anodes for aluminum electrowinning: Topical report, October 1, 1986-June 30, 1987

    Energy Technology Data Exchange (ETDEWEB)

    Walker, J. K.

    1987-12-01

    Because of the cost of building and maintaining a carbon anode plant and the energy penalties associated with the use of carbon anodes in the production of aluminum, the use of inert anodes has long been proposed. Various cermet anodes have been investigated. In this paper, tests on a material, cerium oxyfluoride (CEROX), deposited in situ as an anode, are reported. (JDH)

  14. Influence of ethanol on catalytic properties of vanadium (5) compounds in the reaction of hydrazine oxidation by cerium (4) sulfate

    International Nuclear Information System (INIS)

    A study was made of the effect of ethyl alcohol on the rate of oxidation of hydrazine by cerium sulphate in the presence and in the absence of vanadium compounds. The addition of ethyl alcohol accelerates the oxidation reaction. In the absence of the vanadium compounds acting as catalyst, the increase in the reaction rate is due to the formation of an intermediate complex between the oxidizing agent and the ethyl alcohol. The equilibrium constant for the reaction forming the intermediate complex with composition 1:1 is 0.70+-0.05, while the constant for the rate of decomposition of the intermediate product is 0.24 min-1. In the presence of the vanadium compounds an intermediate complex is formed between the catalyst and the ethyl alcohol. The equilibrium constant for the reaction forming this complex is 0.41+-0.03, and the constant for the rate of decomposition thereof is 0.44x105min-1. (author)

  15. Co/Zr substitution in a cerium-zirconium oxide by catalytic steam reforming of bio-ethanol

    International Nuclear Information System (INIS)

    This work deals with the production of hydrogen by bio-ethanol catalytic steam reforming. The aim is to develop a catalyst active in ethanol conversion, selective in hydrogen and resistant to deactivation, particularly those induced by the formation of carbon deposition. The metal-support interaction being one of the keys of this challenge, catalysts in which a transition metal is inserted into an oxide by a liquid synthesis method (by the precursor method) have been developed. The initial insertion of cobalt into a cerium oxide-zirconia structure presents the advantages to increase the redox properties of the host oxide and to allow a stable reduction of a cobalt part while favoring the metal-support interaction. (O.M.)

  16. Gadolinium doped cerium oxide for soot oxidation: Influence of interfacial metal–support interactions

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Supported Ce-Gd-oxides are applied for soot oxidation for the first time. • Gd2O3 doping facilitates enhanced extrinsic oxygen vacancy concentration in ceria. • The Ce-Gd/TiO2 exhibited the highest soot oxidation activity. • Key parameters that involved in tuning the activity are discussed. - Abstract: The aim of the present investigation was to ascertain the role of Al2O3, SiO2, and TiO2 supports in modulating the catalytic performance of ceria-based solid solutions. In this study, we prepared nanosized Ce-Gd/Al2O3, Ce-Gd/SiO2, and Ce-Gd/TiO2 catalysts by a deposition coprecipitation method and evaluated for soot oxidation. The synthesized catalysts were calcined at two different temperatures to assess their thermal stability and extensively characterized by various techniques, namely, XRD, Raman, BET surface area, TEM, H2-TPR, and UV–vis DRS. XRD and TEM results indicate that Ce-Gd-oxide nanoparticles are in highly dispersed form on the surface of the supports. Raman results show a prominent sharp peak and a broad peak corresponding to the F2g mode of ceria and the presence of oxygen vacancies, respectively. The presence of a significant number of oxygen vacancies in all samples is also confirmed from UV–vis DRS measurements. The H2-TPR results suggest that Gd-doping facilitates the reduction of the materials and decreases the onset temperature of reduction. Among the prepared samples, Ce-Gd/TiO2 catalyst exhibited the highest activity, suggesting the existence of strong interfacial metal support interaction between the active metal oxide and the support

  17. Study of the Dissolution of Thin Films of Cerium Oxide by Using a GaPO{sub 4} Crystal Microbalance

    Energy Technology Data Exchange (ETDEWEB)

    Jakab, S.; Picart, S. [CEA Marcoule, LCA, SCPS, DRCP, DEN, 30 (France); Jakab, S.; Tribollet, B.; Rousseau, Ph.; Perrot, H.; Gabrielli, C. [Univ Paris 06, CNRS, LISE, UPR 15, F-7552 Paris (France)

    2009-07-01

    In this study, microbalance measurements with a GaPO{sub 4} crystal were performed to determine the dissolution rate of cerium oxide thin films at room temperature after a high temperature treatment of the hydroxide precursor Ce(OH){sub 4} at 700 degrees C. The properties of the GaPO{sub 4} crystal enables gravimetric measurements to be performed after being heated at high temperatures where the classical quartz crystal microbalance irreversibly loses all its piezoelectric properties. The GaPO{sub 4} resonators were calibrated at room temperature by galvano-static copper deposition before and after a high-temperature treatment, and the sensitivity coefficients K{sub s} were found to be identical, which proved the high potential of GaPO{sub 4} at high temperatures. However the accuracy of the gravimetric measurements is lower after a high temperature treatment. The rate determining step of the cerium oxide dissolution seems to be the reduction reaction of Ce(IV) to Ce(III), which is carried out by the hydrogen peroxide present in the dissolution medium. (authors)

  18. Study of the Dissolution of Thin Films of Cerium Oxide by Using a GaPO4 Crystal Microbalance

    International Nuclear Information System (INIS)

    In this study, microbalance measurements with a GaPO4 crystal were performed to determine the dissolution rate of cerium oxide thin films at room temperature after a high temperature treatment of the hydroxide precursor Ce(OH)4 at 700 degrees C. The properties of the GaPO4 crystal enables gravimetric measurements to be performed after being heated at high temperatures where the classical quartz crystal microbalance irreversibly loses all its piezoelectric properties. The GaPO4 resonators were calibrated at room temperature by galvano-static copper deposition before and after a high-temperature treatment, and the sensitivity coefficients Ks were found to be identical, which proved the high potential of GaPO4 at high temperatures. However the accuracy of the gravimetric measurements is lower after a high temperature treatment. The rate determining step of the cerium oxide dissolution seems to be the reduction reaction of Ce(IV) to Ce(III), which is carried out by the hydrogen peroxide present in the dissolution medium. (authors)

  19. Si3N4-TiC composites modified by gallium, indium, cerium, zirconium and zinc oxides additives

    International Nuclear Information System (INIS)

    The paper presents the results of experiments on the modification of ceramic composites of the Si3N4-Al2O3-Y2O3-TiC system by adding gallium, indium, cerium, zirconium and zinc oxides with the aim of improving the fracture toughness of the material. For all the compositions, the value of stress intensity factor KIC is very high and ranges from 7.5 to 9 MPa m0,5 depending on the kind and amount of the additive. The best fracture toughness was obtained in 60% Si3N4-Al2O3-3.5%Y2O3-15%TiC sinters added with 11% of ZrO2 or 6.5% of CeO. An interesting experimental fact is that an increase of the KIC value does not result in any drastic decrease of the material hardness. In order to explain the role playing by the additives in increasing so significantly the fracture toughness of the sintered materials, their microstructures were examined. Tests of the machining properties of the Si3N4-Al2O3-Y2O3-TiC composites when used for the high-speed cutting of heat-treated 45 steel have shown that even a small amount of gallium, zirconium, zinc or cerium oxide introduced in place of Al2O3 increases appreciably the service life of the ceramic tool. (author)

  20. Cerium oxide nanoparticles promote neurogenesis and abrogate hypoxia-induced memory impairment through AMPK–PKC–CBP signaling cascade

    Directory of Open Access Journals (Sweden)

    Arya A

    2016-03-01

    Full Text Available Aditya Arya,1 Anamika Gangwar,1 Sushil Kumar Singh,2 Manas Roy,3,4 Mainak Das,3 Niroj Kumar Sethy,1 Kalpana Bhargava1 1Peptide and Proteomics Division, Defense Institute of Physiology and Allied Sciences, 2Functional Materials Division, Solid State Physics Laboratory, Defense Research and Development Organization, Timarpur, Delhi, 3Biological Science and Bioengineering, Indian Institute of Technology, Kanpur, 4Department of Chemistry, Indian Institute of Engineering Science and Technology, Howrah, India Abstract: Structural and functional integrity of the brain is adversely affected by reduced oxygen saturation, especially during chronic hypoxia exposure and often encountered by altitude travelers or dwellers. Hypoxia-induced generation of reactive nitrogen and oxygen species reportedly affects the cortex and hippocampus regions of the brain, promoting memory impairment and cognitive dysfunction. Cerium oxide nanoparticles (CNPs, also known as nanoceria, switch between +3 and +4 oxidation states and reportedly scavenge superoxide anions, hydrogen peroxide, and peroxynitrite in vivo. In the present study, we evaluated the neuroprotective as well as the cognition-enhancing activities of nanoceria during hypobaric hypoxia. Using polyethylene glycol-coated 3 nm nanoceria (PEG-CNPs, we have demonstrated efficient localization of PEG-CNPs in rodent brain. This resulted in significant reduction of oxidative stress and associated damage during hypoxia exposure. Morris water maze-based memory function tests revealed that PEG-CNPs ameliorated hypoxia-induced memory impairment. Using microscopic, flow cytometric, and histological studies, we also provide evidences that PEG-CNPs augmented hippocampus neuronal survival and promoted neurogenesis. Molecular studies revealed that PEG-CNPs promoted neurogenesis through the 5'-adenine monophosphate-activated protein kinase–protein kinase C–cyclic adenosine monophosphate response element-binding protein

  1. Investigation of electrodeposited cerium oxide based films on carbon steel and of the induced formation of carbonated green rusts

    International Nuclear Information System (INIS)

    Cerium oxide based films on carbon steel were deposited using a cathodic electrodeposition approach and from relatively concentrated solutions. The effects of the relatively high cerium nitrate concentrations (0.1 and 0.25 M) and of applied current density (0.25 mA cm-2 ≤ j ≤ 3 mA cm-2) on the composition and microstructure of the films were thoroughly investigated with the support of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman and Fourier transformed infrared (FTIR) spectroscopies. The results showed that the use of 0.25 M solutions brought about immediate formation of the films compared to the 0.1 M. As the applied current density was increased, the time elapsed for achieving a stabilisation of the potential decreased. Also, the CeO2 crystallite size decreased with increasing applied current density. However, at high cathodic current densities, the crystallite size was similar regardless of the concentration, hence suggesting that the precipitation mechanisms became predominant. CeO2 was the major species deposited on carbon steel. Ce(OH)3 was also well distinguished in the deposits elaborated from 0.25 M solutions. Both concentrations led to the formation of a carbonated green rust in which some carbonates were probably replaced by nitrate anions. The mechanisms of formation of the green rust and its evolution with time are also elucidated in this work

  2. Investigation of electrodeposited cerium oxide based films on carbon steel and of the induced formation of carbonated green rusts

    Energy Technology Data Exchange (ETDEWEB)

    Hamlaoui, Y. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France); Pedraza, F. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs (LEMMA), Pole Sciences et Technologie, Universite de La Rochelle Avenue Michel Crepeau, 17042 La Rochelle Cedex 1 (France)], E-mail: fpedraza@univ-lr.fr; Tifouti, L. [Laboratoire de Genie de l' Environnement, Universite Badji Mokhtar, BP 1223, 23020 El Hadjar-Annaba (Algeria)

    2008-08-15

    Cerium oxide based films on carbon steel were deposited using a cathodic electrodeposition approach and from relatively concentrated solutions. The effects of the relatively high cerium nitrate concentrations (0.1 and 0.25 M) and of applied current density (0.25 mA cm{sup -2} {<=} j {<=} 3 mA cm{sup -2}) on the composition and microstructure of the films were thoroughly investigated with the support of scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman and Fourier transformed infrared (FTIR) spectroscopies. The results showed that the use of 0.25 M solutions brought about immediate formation of the films compared to the 0.1 M. As the applied current density was increased, the time elapsed for achieving a stabilisation of the potential decreased. Also, the CeO{sub 2} crystallite size decreased with increasing applied current density. However, at high cathodic current densities, the crystallite size was similar regardless of the concentration, hence suggesting that the precipitation mechanisms became predominant. CeO{sub 2} was the major species deposited on carbon steel. Ce(OH){sub 3} was also well distinguished in the deposits elaborated from 0.25 M solutions. Both concentrations led to the formation of a carbonated green rust in which some carbonates were probably replaced by nitrate anions. The mechanisms of formation of the green rust and its evolution with time are also elucidated in this work.

  3. Synthesis and characterization of C14TAB passivated cerium oxide nanoparticles prepared by co-precipitation route

    Science.gov (United States)

    Krishna Chandar, N.; Jayavel, R.

    2014-04-01

    A facile co-precipitation route has been employed to synthesize cerium oxide (CeO2) nanoparticles using cationic surfactant (tetradecyltrimethyl ammonium bromide, C14TAB) and cerium nitrate hexahydrate at room temperature. X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), selected area electron diffraction (SAED), fourier transform infrared spectroscopy (FT-IR), UV-vis spectrophotometer and photoluminescence spectroscopy (PL) were employed to characterize the as-prepared sample. The XRD pattern showed cubic fluorite structure of CeO2 without any impurity peaks, revealing high purity of the sample. The lattice strain experienced by the sample was analyzed using Williamson-Hall plot. FTIR studies confirmed the presence of C14TAB on the CeO2 nanoparticles. TEM revealed that the as-prepared CeO2 sample consists of uniform particles with particle size of 10 nm. The red shift phenomenon was observed in UV-vis spectrum, which was further supported by PL studies.

  4. Probing and tuning the size, morphology, chemistry and structure of nanoscale cerium oxide

    Science.gov (United States)

    Kuchibhatla, Satyanarayana Vnt

    Cerium oxide (ceria)-based materials in the nanoscale regime are of significant fundamental and technological interest. Nanoceria in pure and doped forms has current and potential use in solid oxide fuel cells, catalysis, UV-screening, chemical mechanical planarization, oxygen sensors, and bio-medical applications. The characteristic feature of Ce to switch between the +3 and +4 oxidation states renders oxygen buffering capability to ceria. The ease of this transformation was expected to be enhanced in the nanoceria. In most the practical scenarios, it is necessary to have a stable suspension of ceria nanoparticles (CNPs) over longer periods of time. However, the existing literature is confined to short term studies pertaining to synthesis and property evaluation. Having understood the need for a comprehensive understanding of the CNP suspensions, this dissertation is primarily aimed at understanding the behavior of CNPs in various chemical and physical environments. We have synthesized CNPs in the absence of any surfactants at room temperature and studied the aging characteristics. After gaining some understanding about the behavior of this functional oxide, the synthesis environment and aging temperature were varied, and their affects were carefully analyzed using various materials analysis techniques such as high resolution transmission electron microscopy (HRTEM), UV-Visible spectroscopy (UV-Vis), and X-ray photoelectron spectroscopy (XPS). When the CNPs were aged at room temperature in as-synthesized condition, they were observed to spontaneously assemble and evolve as fractal superoctahedral structures. The reasons for this unique polycrystalline morphology were attributed to the symmetry driven assembly of the individual truncated octahedral and octahedral seed of the ceria. HRTEM and Fast Fourier Transform (FFT) analyses were used to explain the agglomeration behavior and evolution of the octahedral morphology. Some of the observations were supported by

  5. Laser induced densification of cerium gadolinium oxide: Application to single-chamber solid oxide fuel cells

    Science.gov (United States)

    Mariño, Mariana; Rieu, Mathilde; Viricelle, Jean-Paul; Garrelie, Florence

    2016-06-01

    In single-chamber solid oxide fuel cells (SC-SOFC), anode and cathode are placed in a gas chamber where they are exposed to a fuel/air mixture. Similarly to conventional dual-chamber SOFC, the anode and the cathode are separated by an electrolyte. However, as in the SC-SOFC configuration the electrolyte does not play tightness role between compartments, this one can be a porous layer. Nevertheless, it is necessary to have a diffusion barrier to prevent the transportation of hydrogen produced locally at the anode to the cathode that reduces fuel cell performances. This study aims to obtain directly a diffusion barrier through the surface densification of the electrolyte Ce0.9Gd0.1O1.95 (CGO) by a laser treatment. KrF excimer laser and Yb fiber laser irradiations were used at different fluences and number of pulses to modify the density of the electrolyte coating. Microstructural characterizations confirmed the modifications on the surface of the electrolyte for appropriate experimental conditions showing either grain growth or densified but cracked surfaces. Gas permeation and electrical conductivities of the modified electrolyte were evaluated. Finally SC-SOFC performances were improved for the cells presenting grain growth at the electrolyte surface.

  6. Study of the catalytic activity of pure or cerium-containing thoria in the catalytic oxidation of carbon monoxide (1963)

    International Nuclear Information System (INIS)

    We have undertaken research into the oxidation of carbon monoxide on pure thoria prepared by the decomposition of thorium nitrate, and on the same oxide containing small amounts of cerium. The results we have obtained, both as concerns the chemisorption of the various gases as well as the conductivity of the absorbent and the kinetics of the oxidation itself, appear to be quite coherent. The following steps occur: 1) The carbon monoxide is adsorbed on a clean catalyst surface, the oxygen remaining un-adsorbed. 2) The oxygen is adsorbed on a previously adsorbed carbon, monoxide layer, and reacts to give carbon dioxide (no role being played by the lattice oxygen). This behaviour is usual for a p-type semiconductor. We have in fact confirmed that semi-conductivity is of this type, and the gas-solid interactions can be written: (1) CO(g) ↔ CO+(a) + e- (2) CO+ 1/2 O2(g) + 2 e- → CO-2(a) (3) CO-2(a) ↔ CO2(g) + e- The kinetic equation obtained by supposing that step (2) is the slowest, makes it possible to deduce correctly the experimental results which can be expressed as: dp / dt = k (P0.3CO x P0.5O2) / (1+ k' x PCO2) The influence of the addition of small amounts of cerium can also be explained logically by this process; there is in fact both a decrease in the conductivity and an increase in the catalytic activity, this being characteristic, according to VOLKENSTEIN [52] of an n-type rate-determining reaction occurring on a p-type semi-conductor. We believe that these first results could be advantageously complemented by a study of thoria prepared by other means and doped differently. (author)

  7. Cerium oxide nanoparticles coated by surfactant sodium bis(2-ethylhexyl) sulphosuccinate (AOT): local atomic structures and x-ray absorption spectroscopic studies

    International Nuclear Information System (INIS)

    Cerium oxide nanoparticles coated by sodium bis(2-ethylhexyl) sulphosuccinate (AOT) were prepared by using a microemulsion method. Transmission electron microscopy revealed an average particle size of 2-3 nm. X-ray diffraction showed that the cerium oxide nanoparticles retain the CeF2-type cubic structures like the bulk crystal. The intermediate valence of formally tetravalent compounds had been detected by x-ray-absorption near-edge structure (XANES) spectra of Ce LIII absorption in bulk CeO2 and the cerium oxide nanoparticles. Two well resolved white lines can be assigned to the electron configurations of 4f0L and 4f1L, respectively, where L denotes a ligand hole. At the same time, the cerium oxide nanoparticles also showed the structural features of trivalent compounds, in comparison to the trivalent Ce(NO3)3·6H2O. Four Lorentzian functions and two arctan functions were used to fit the normalized XANES spectra. The extended x-ray-absorption fine-structure (EXAFS) technique was used to probe the local atomic structures around the absorber Ce. The multielectron excitation effect on the EXAFS spectra was eliminated. A core-shell model was used to deduce the near-neighbour structural parameters around cerium. Bulk CeO2 with eight oxygen atoms located at 2.343 A was used as the reference sample to extract the backscattering amplitude and phase shift of the Ce-O bond. One half of the atoms locate at the core part with the CeF2-type cubic structures (eight oxygens at 2.343 A around Ce), the other half of the atoms are amorphous phase located in the shell part (surface of the nanoparticles) with approximately Ce2O3 structural features (averaged seven oxygens at 2.50 A around Ce). (author)

  8. The iron and cerium oxide influence on the electric conductivity and the corrosion resistance of anodized aluminium

    International Nuclear Information System (INIS)

    The influence of different treatments on the aluminum system covered with aluminum oxide is investigated. The aluminum anodization in sulphuric media and in mixed sulphuric and phosphoric media was used to alter the corrosion resistance, thickness, coverage degree and microhardness of the anodic oxide. Iron electrodeposition inside the anodic oxide was used to change its electric conductivity and corrosion resistance. Direct and pulsed current were used for iron electrodeposition and the Fe(SO4)2(NH4)2.6H2O electrolyte composition was changed with the addition of boric and ascorbic acids. To the sealing treatment the CeCl3 composition was varied. The energy dispersive x-ray (EDS), the x-ray fluorescence spectroscopy (FRX) and the morphologic analysis by scanning electronic microscopy (SEM) allowed to verify that, the pulsed current increase the iron content inside the anodic layer and that the use of the additives inhibits the iron oxidation. The chronopotentiometric curves obtained during iron electrodeposition indicated that the boric and ascorbic acids mixture increased the electrodeposition process efficiency. The electrochemical impedance spectroscopy (EIE), the Vickers (Hv) microhardness measurements and morphologic analysis evidenced that the sealing treatment improves the corrosion resistance of the anodic film modified with iron. The electrical impedance (EI) technique allowed to prove the electric conductivity increase of the anodized aluminum with iron electrodeposited even after the cerium low concentration treatment. Iron nanowires were prepared by using the anodic oxide pores as template. (author)

  9. Effects of cathodic electrodeposition parameters of cerium oxide film on the corrosion resistance of the 2024 Al alloy

    Energy Technology Data Exchange (ETDEWEB)

    Brunelli, K.; Bisaglia, F.; Magrini, M.; Dabala, M. [DIMEG University of Padua, Padua (Italy); Kovac, J. [Department of Surface Engineering and Optoelectronics, Jozef Stefan Institute, Ljubljana, (Slovenia)

    2009-07-15

    Cerium oxide thin films obtained by cathodic electrodeposition on 2024 aluminium alloy have been studied. The coatings, obtained with electrochemical deposition, offer an effective corrosion protection and require a lower deposition time when compared to chemical conversion coatings. The coatings were obtained at room temperature by deposition from CeCl{sub 3}/H{sub 2}O{sub 2} aqueous solutions and the influence of several parameters (CeCl{sub 3} concentration, H{sub 2}O{sub 2} concentration, deposition time, current intensity) on the corrosion resistance was studied. The composition, morphology and microstructure of the films have been characterized by SEM, XPS and AFM. The corrosion resistance was investigated through potentiodynamic tests in 3% NaCl solution. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  10. Kinetics and mechanism of iridium (III) catalysed oxidation of tellurium (IV) by cerium (IV) in sulfuric acid medium

    International Nuclear Information System (INIS)

    The kinetics and mechanism of iridium (III) catalysed oxidation of tellurium (IV) by cerium (IV) have been studied in sulfuric acid medium. The reaction is first order in [Ir (III)] as well as in [Ce (IV)] and fractional order (0.23) in [Te (IV)]. Increase in [H3O+] accelerates the rate while that in ionic strength or [HSO4-] retards. Ce (III), one of the products, inhibits while the other, Te (VI), has negligible effect on the rate. The reaction is supposed to proceed via the formation of a complex between Te (IV) and Ir (III) which in turn reacts with active Ce (IV) species in a reversible step. A rate law, consistent with the observed kinetic data, has been derived basing on the proposed mechanism. (author)

  11. CuO/CeO2 catalysts prepared with different cerium supports for CO oxidation at low temperature

    International Nuclear Information System (INIS)

    The activity of a catalyst depends on the nature of its support, its active site, and its preparation method. This study aimed to employ various types of CeO2 supports such as commercial CeO2 and self-prepared CeO2 for the preparation of copper catalysts. The CuO/CeO2 catalysts were prepared using the polyol process and impregnation method. The catalysts were characterized using Brunauer–Emmett–Teller analysis, scanning electron microscopy, and X-ray analysis, and their catalytic activity for CO removal was evaluated in a microcatalytic reactor. The experimental results showed that the catalytic activity of the CuO/CeO2 catalysts with different calcination temperatures decreased in the following order: 500 °C > 300 °C > 700 °C. Compared to the impregnation method, the polyol process generated well-dispersed metal particles over the support and showed higher CO removal efficiency with low activation energy. Compared to CuO/CeO2 catalysts with commercial CeO2, those with CeO2 that was self-prepared by pyrolysis had a large pore volume and good crystal structure of CeO2 and showed good performance. The catalytic activity for CO removal was in the following order: CuO/CeO2-P (pyrolysis) > CuO/CeO2-C (commercial) > CuO/CeO2-D (deposition precipitation). CuO/CeO2-P catalysts showed good activity even at low temperature. The CuO/CeO2-P(300)-P-120 min catalyst was found to possess the good CO removal rate when the oxygen content was 6%, CO concentration was 500 ppm, catalyst weighed 1.0 g, pollutant gas velocity was 500 mL min−1, SV was 3.7 × 104 h−1, and reaction temperature was 150 °C. - Highlights: • CuO/CeO2 catalysts were prepared using polyol and impregnation methods. • The supports of catalyst were self-prepared cerium oxide and commercial cerium oxide. • Pyrolysis and deposition precipitation methods were used for cerium preparation. • Catalytic activity of CuO/CeO2 catalysts were evaluated by the removal of CO

  12. CuO/CeO{sub 2} catalysts prepared with different cerium supports for CO oxidation at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Chi-Yuan [School of Public Health, Chung Shan Medical University, Taichung 402, Taiwan, ROC (China); Department of Occupational Medicine, Chung Shan Medical University Hospital, Taichung 402, Taiwan, ROC (China); Chang, Wen-Chi [Department of Environmental Engineering, National Chung Hsing University, Taichung 402, Taiwan, ROC (China); Wey, Ming-Yen, E-mail: mywey@dragon.nchu.edu.tw [Department of Environmental Engineering, National Chung Hsing University, Taichung 402, Taiwan, ROC (China)

    2013-08-15

    The activity of a catalyst depends on the nature of its support, its active site, and its preparation method. This study aimed to employ various types of CeO{sub 2} supports such as commercial CeO{sub 2} and self-prepared CeO{sub 2} for the preparation of copper catalysts. The CuO/CeO{sub 2} catalysts were prepared using the polyol process and impregnation method. The catalysts were characterized using Brunauer–Emmett–Teller analysis, scanning electron microscopy, and X-ray analysis, and their catalytic activity for CO removal was evaluated in a microcatalytic reactor. The experimental results showed that the catalytic activity of the CuO/CeO{sub 2} catalysts with different calcination temperatures decreased in the following order: 500 °C > 300 °C > 700 °C. Compared to the impregnation method, the polyol process generated well-dispersed metal particles over the support and showed higher CO removal efficiency with low activation energy. Compared to CuO/CeO{sub 2} catalysts with commercial CeO{sub 2}, those with CeO{sub 2} that was self-prepared by pyrolysis had a large pore volume and good crystal structure of CeO{sub 2} and showed good performance. The catalytic activity for CO removal was in the following order: CuO/CeO{sub 2}-P (pyrolysis) > CuO/CeO{sub 2}-C (commercial) > CuO/CeO{sub 2}-D (deposition precipitation). CuO/CeO{sub 2}-P catalysts showed good activity even at low temperature. The CuO/CeO{sub 2}-P(300)-P-120 min catalyst was found to possess the good CO removal rate when the oxygen content was 6%, CO concentration was 500 ppm, catalyst weighed 1.0 g, pollutant gas velocity was 500 mL min{sup −1}, SV was 3.7 × 10{sup 4} h{sup −1}, and reaction temperature was 150 °C. - Highlights: • CuO/CeO{sub 2} catalysts were prepared using polyol and impregnation methods. • The supports of catalyst were self-prepared cerium oxide and commercial cerium oxide. • Pyrolysis and deposition precipitation methods were used for cerium preparation.

  13. Stability and mobility of cerium oxide nanoparticles in soils: effects of humic substances, pH and ionic strength

    Science.gov (United States)

    Chen, Yirui; Mu, Linlin; Li, Chunyan; Bai, Lingyun; Jacobson, Astrid; Darnault, Christophe

    2015-04-01

    Among the large number of types of nanomaterials used in the field of nanotechnology, cerium oxide nanoparticles (CeO2 NPs) are among the top five most commonly utilized by industry, agriculture and nanomedicine for their unique physico-chemical properties. They are used, for example, in the production of catalysts, as fuel additives, and as polishing agents. Therefore, the release and encounter of CeO2 NPs in the environment following their application, waste disposal, life-cycle and accidents is inevitable. It is critical to examine the behavior of CeO2 NPs released in the environment to assess the risk they pose to the environmental and public health. In particular, little is known about the fate and transport of CeO2 NPs in soils and groundwater. To assess the behavior of CeO2 NPs, it is important to investigate the factors that affect their stability and mobility. Humic substances are a major component of soils and have been shown to have the potential to impact the transport and retention of nanoparticles in soils. Consequently, our study characterizes the impacts of humic and fulvic acids on the stability and mobility of cerium oxides in model porous media under various pH and ionic strength conditions. Batch experiments conducted at various concentrations of humic and fulvic acids coupled with a wide range of pHs and ionic strengths were investigated. Selected parameters from these batch studies were then used as experimental conditions representative of environmental systems to perform column transport experiments to assess of the mobility of CeO2 NPs in saturated porous media, which is the first step in simulating their behavior in soil and groundwater systems.

  14. Evaluation of the effect of valence state on cerium oxide nanoparticle toxicity following intratracheal instillation in rats.

    Science.gov (United States)

    Dunnick, Katherine M; Morris, Anna M; Badding, Melissa A; Barger, Mark; Stefaniak, Aleksandr B; Sabolsky, Edward M; Leonard, Stephen S

    2016-09-01

    Cerium (Ce) is becoming a popular metal for use in electrochemical applications. When in the form of cerium oxide (CeO2), Ce can exist in both 3 + and 4 + valence states, acting as an ideal catalyst. Previous in vitro and in vivo evidence have demonstrated that CeO2 has either anti- or pro-oxidant properties, possibly due to the ability of the nanoparticles to transition between valence states. Therefore, we chose to chemically modify the nanoparticles to shift the valence state toward 3+. During the hydrothermal synthesis process, 10 mol% gadolinium (Gd) and 20 mol% Gd, were substituted into the lattice of the CeO2 nanoparticles forming a perfect solid solution with various A-site valence states. These two Gd-doped CeO2 nanoparticles were compared to pure CeO2 nanoparticles. Preliminary characteristics indicated that doping results in minimal size and zeta potential changes but alters valence state. Following characterization, male Sprague-Dawley rats were exposed to 0.5 or 1.0 mg/kg nanoparticles via a single intratracheal instillation. Animals were sacrificed and bronchoalveolar lavage fluid and various tissues were collected to determine the effect of valence state and oxygen vacancies on toxicity 1-, 7-, or 84-day post-exposure. Results indicate that damage, as measured by elevations in lactate dehydrogenase, occurred within 1-day post-exposure and was sustained 7-day post-exposure, but subsided to control levels 84-day post-exposure. Furthermore, no inflammatory signaling or lipid peroxidation occurred following exposure with any of the nanoparticles. Our results implicate that valence state has a minimal effect on CeO2 nanoparticle toxicity in vivo. PMID:26898289

  15. Thermal barrier coating of lanthanum-zirconium-cerium composite oxide made by electron beam-physical vapor deposition

    International Nuclear Information System (INIS)

    Lanthanum-zirconium-cerium composite oxide (La2(Zr0.7Ce0.3)2O7, LZ7C3) as a candidate material for thermal barrier coatings (TBCs) was prepared by electron beam-physical vapor deposition (EB-PVD). The composition, crystal structure, thermophysical properties, surface and cross-sectional morphologies and cyclic oxidation behavior of the LZ7C3 coating were studied. The results indicated that LZ7C3 has a high phase stability between 298 K and 1573 K, and its linear thermal expansion coefficient (TEC) is similar to that of zirconia containing 8 wt% yttria (8YSZ). The thermal conductivity of LZ7C3 is 0.87 W m-1 K-1 at 1273 K, which is almost 60% lower than that of 8YSZ. The deviation of coating composition from the ingot can be overcome by the addition of excess CeO2 and ZrO2 during ingot preparation or by adjusting the process parameters. The failure of the LZ7C3 coating is mainly a result of the occurrence of micro-cracks inside ceramic topcoat, which cause the abnormal oxidation of bond coat.

  16. Improvements in or relating to cerium compounds

    International Nuclear Information System (INIS)

    A process for the preparation of a dispersible cerium compound comprises heating a substantially dry cerium (IV) oxide hydrate in the presence of a deaggregating agent to cause deaggregation of aggregated crystallites in the cerium (IV) oxide hydrate and produce a dry dispersible cerium compound. The deaggregating agent is an acid species e.g. NO3-, Cl- or ClO4-. The dry dispersible product may be mixed with an aqueous medium to form a colloidal dispersion and if the dispersion is allowed to dry, a gel. (author)

  17. Effect of cerium additives on structure and electrical properties of Aurivillius oxides (K0.16Na0.84)0.5Bi4.5Ti4O15

    International Nuclear Information System (INIS)

    Highlights: • Cerium modified KNBT ceramics were synthesized using the solid-state process. • The d33 and ρ of KNBT ceramic were improved by cerium additives. • The tan δ at high temperature of KNBT ceramic was suppressed by cerium additive. • The d33 and Tc of KNBT-Ce50 ceramic were 28 pC/N and 656 °C, respectively. - Abstract: The effect of cerium additive on structure and electric properties of Aurivillius oxide (K0.16Na0.84)0.5Bi4.5Ti4O15 (KNBT), was investigated. Phase analysis was performed by X-ray diffraction analyses (XRD) and Raman spectroscopy. Morphologies were assessed by the scanning electron microscopy. Piezoelectric properties of the KNBT ceramic were improved by the modification of cerium ions. Dielectric loss at high temperature of the KNBT ceramic was also suppressed because of the cerium ions introduced. Piezoelectric coefficient (d33) and Curie temperature (Tc) of KNBT ceramic modified with 0.50 wt% cerium were 28 pC/N and 656 °C, respectively, together with higher resistivity (higher than 107 Ω cm at 550 °C). Moreover, reasons for the improvement of electric properties of the KNBT ceramic modified by cerium were also discussed

  18. Effects of pH and fulvic acids concentration on the stability of fulvic acids – cerium (IV) oxide nanoparticle complexes

    OpenAIRE

    Oriekhova, Olena; Stoll, Serge

    2016-01-01

    The behavior of cerium (IV) oxide nanoparticles has been first investigated at different pH conditions. The point of zero charge was determined as well as the stability domains using dynamic light scattering, nanoparticle tracking analysis and scanning electron microscopy. A baseline hydrodynamic diameter of 180 nm was obtained indicating that individual CeO2 nanoparticles are forming small aggregates. Then we analyzed the particle behavior at variable concentrations of fulvic acids for three...

  19. Evaluation of cerium oxide coated Cu cermets as inert anodes for aluminum electrowinning. Final report, August 1990--March 1992

    Energy Technology Data Exchange (ETDEWEB)

    1992-08-01

    Cu/NiFe{sub 2}O{sub 4} cermets were evaluated, with and without an in-situ deposited CEROX (TM; cerium oxide) coating, in 100 h laboratory A1 electrowinning tests. Bath ratio and current density were varied between tests and corrosion was determined by contamination of the aluminum and cryolite by cermet components (Cu, Fe, and Ni). Higher bath ratios of 1.5 to 1.6 led to less corrosion and thicker CEROX coatings. Lower current densities led to slightly less corrosion but much less oxidation of the Cu cermet substrate. At identical test conditions, the corrosion of the CEROX coated cermets was 1/7 that of an uncoated cermet. Corrosion was increased in CEROX coated cermets tested under unsaturated alumina conditions. The electrical conductivity of the CEROX coating was measured to be {approximately}0.2 ohm{sup {minus}1}cm{sup {minus}1}, resulting in a slight voltage penalty, depending on the thickness of the coating.

  20. Polyacrylic acid-coated cerium oxide nanoparticles: An oxidase mimic applied for colorimetric assay to organophosphorus pesticides.

    Science.gov (United States)

    Zhang, Shi-Xiang; Xue, Shi-Fan; Deng, Jingjing; Zhang, Min; Shi, Guoyue; Zhou, Tianshu

    2016-11-15

    It is important and urgent to develop reliable and highly sensitive methods that can provide on-site and rapid detection of extensively used organophosphorus pesticides (OPs) for their neurotoxicity. In this study, we developed a novel colorimetric assay for the detection of OPs based on polyacrylic acid-coated cerium oxide nanoparticles (PAA-CeO2) as an oxidase mimic and OPs as inhibitors to suppress the activity of acetylcholinesterase (AChE). Firstly, highly dispersed PAA-CeO2 was prepared in aqueous solution, which could catalyze the oxidation of TMB to produce a color reaction from colorless to blue. And the enzyme of AChE was used to catalyze the substrate of acetylthiocholine (ATCh) to produce thiocholine (TCh). As a thiol-containing compound with reducibility, TCh can decrease the oxidation of TMB catalyzed by PAA-CeO2. Upon incubated with OPs, the enzymatic activity of AChE was inhibited to produce less TCh, resulting in more TMB catalytically oxidized by PAA-CeO2 to show an increasing blue color. The two representative OPs, dichlorvos and methyl-paraoxon, were tested using our proposed assay. The novel assay showed notable color change in a concentration-dependent manner, and as low as 8.62 ppb dichlorvos and 26.73 ppb methyl-paraoxon can be readily detected. Therefore, taking advantage of such oxidase-like activity of PAA-CeO2, our proposed colorimetric assay can potentially be a screening tool for the precise and rapid evaluation of the neurotoxicity of a wealth of OPs. PMID:27208478

  1. The effect of cerium and lanthanum surface treatments on early stages of oxidation of A361 aluminium alloy at high temperature

    International Nuclear Information System (INIS)

    X-ray photoelectron spectroscopy analysis has been used to study the surface of A361 aluminium alloy after electrodeposition of cerium and lanthanum compounds followed by oxidation tests in air at 100-500 deg. C for 2 h. Cerium and lanthanum oxide deposits are found on the β-AlFeSi second phase particles and to a lesser extent on the eutectic Al-Si areas, while the α-Al phase is covered with a thin aluminium oxide film. This uneven deposition may be related either to a preferential nucleation and growth process on active interfaces or to the differing electrical conductivity of the phases and intermetallic compounds of the alloy. Initial stages of oxidation of A361 alloy disclosed thickening of the aluminium oxide layer and Mg enrichment at the surface, especially above 400 deg. C. Rare earth deposits revealed two different effects: reduced Mg diffusion and enhanced thickening of the aluminium oxide film. A distinctive behaviour of Ce oxide appears at 300-500 deg. C related with Ce(III) to Ce(IV) transition

  2. The effect of cerium and lanthanum surface treatments on early stages of oxidation of A361 aluminium alloy at high temperature

    Science.gov (United States)

    Pardo, A.; Feliú, S.; Merino, M. C.; Arrabal, R.; Matykina, E.

    2007-11-01

    X-ray photoelectron spectroscopy analysis has been used to study the surface of A361 aluminium alloy after electrodeposition of cerium and lanthanum compounds followed by oxidation tests in air at 100-500 °C for 2 h. Cerium and lanthanum oxide deposits are found on the β-AlFeSi second phase particles and to a lesser extent on the eutectic Al-Si areas, while the α-Al phase is covered with a thin aluminium oxide film. This uneven deposition may be related either to a preferential nucleation and growth process on active interfaces or to the differing electrical conductivity of the phases and intermetallic compounds of the alloy. Initial stages of oxidation of A361 alloy disclosed thickening of the aluminium oxide layer and Mg enrichment at the surface, especially above 400 °C. Rare earth deposits revealed two different effects: reduced Mg diffusion and enhanced thickening of the aluminium oxide film. A distinctive behaviour of Ce oxide appears at 300-500 °C related with Ce(III) to Ce(IV) transition.

  3. Kinetic studies on dissolution of UO2 powders in acid solutions by using cerium (IV) or chlorine dioxide as oxidants

    International Nuclear Information System (INIS)

    The UO2 powders of 100-150, 150-212, 212-250, and 250-300 μm were dissolved in HNO3 or HCl solutions containing strong oxidants to examine their effect on the dissolution rates. Cerium(IV) species and ClO2 were used as oxidants in HNO3 and HCl solutions, respectively. The Ce(IV) species were prepared by bubbling O3 gas into HNO3 solutions containing Ce(NO3)3. All dissolution experiments were carried out under rapid stirring conditions which make it possible to neglect the diffusion effect. Dissolution reactions were analyzed on the assumptions that the UO2 powders are spherical particles and homogeneously dissolved from their external surface. Dissolution rate constants (Φ) in mol·cm-2·min-1 were measured at various concentrations of oxidants and temperatures. Furthermore, the effect of acid concentrations on the dissolution rate was also examined. As a result, the dissolution rate constants Φ were found to be expressed as Φ=kN[Ce(IV)][H+]0.6 for HNO3 solution([HNO3]=1-5M, Temp.≤30degC) and Φ=kH[ClO2][H+]-0.3 for HCl solution([HCl]=1-5M, Temp.≤30degC), respectively. Activation energies(kJ·mol-1) for the apparent dissolution rate constants are 44.1±1.9 for the HNO3 solution system and 33.5±2.8 for the HCl solution system, respectively. (author)

  4. Near- and supercritical alcohols as solvents and surface modifiers for the continuous synthesis of cerium oxide nanoparticles.

    Science.gov (United States)

    Slostowski, Cédric; Marre, Samuel; Babot, Odile; Toupance, Thierry; Aymonier, Cyril

    2012-12-01

    Supercritical fluids offer fast and facile routes toward well-crystallized tailor-made cerium oxide nanoparticles. However, the use of surfactants to control morphology and surface properties remains essential. Therefore, although water, near-critical (nc) or supercritical (sc), is a solvent of choice, the poor water solubility of some surfactants could require other solvent systems such as alcohols, which could themselves behave as surface modifiers. In here, the influence of seven different alcohols, MeOH, EtOH, PrOH, iPrOH, ButOH, PentOH, and HexOH, in alcothermal conditions (300 °C, 24.5 MPa) over CeO(2) nanocrystals (NCs) size, morphology, and surface properties was investigated. The crystallite size of the CeO(2) nanocrystals can be tuned in the range 3-7 nm depending on the considered alcohol, and their surface has been modified by these solvents without the use of surfactants. Mechanisms are proposed for the interaction of primary and secondary alcohols with CeO(2) surface and its functionalization during the synthesis based on FTIR and TGA-MS studies. This study allows apprehending the role of alcohols during the synthesis and may lead to an informed choice of solvent as a function of the required size and surface properties of CeO(2) NCs. It also opens new route to CeO(2) functionalization using supercritical alcohol derivatives. PMID:23126630

  5. Fate of engineered cerium oxide nanoparticles in an aquatic environment and their toxicity toward 14 ciliated protist species.

    Science.gov (United States)

    Zhang, Wei; Pu, Zhichao; Du, Songyan; Chen, Yongsheng; Jiang, Lin

    2016-05-01

    The potential environmental impacts of engineered cerium oxide nanoparticles (CeO2 NPs) on aquatic organisms have remained largely unknown. Therefore, the laboratory study featured herein was performed to determine the fate of CeO2 NPs in an aquatic environment and their toxicity towards 14 different ciliated protist species at a specified population level. An investigation of 48 h aggregation kinetics in the Dryl's solution showed the CeO2 NPs to be relatively stable. The pH values in three test medium were too far away from PZC, which explained the stability of CeO2 NPs. CeO2 NPs generally elicited more toxicity with increasing NP concentration, following certain dose-response relationships. Nano-CeO2 resulted in greater toxicity in a particle state than when added as bulk material. LC50 values showed a negative correlation with the surface-to-volume ratio for these protists, suggesting that surface adsorption of CeO2 NPs might contribute to the observed toxicity. Additionally, acute toxic responses of 14 ciliated protist species to CeO2 NPs were not significantly phylogenetically conserved. The results of these observations provide a better insight into the potential risks of CeO2 NPs in an aquatic environment. PMID:26986089

  6. Preparation of core/shell and hollow nanostructures of cerium oxide by electrodeposition on a polystyrene sphere template.

    Science.gov (United States)

    Yamaguchi, Ippei; Watanabe, Mitsuru; Shinagawa, Tsutomu; Chigane, Masaya; Inaba, Minoru; Tasaka, Akimasa; Izaki, Masanobu

    2009-05-01

    Core/shell nanostructures of polystyrene (PS)/CeO2 have been prepared on conductive glass substrates by using a novel electrochemical route consisting of (i) the electrophoretic deposition of a PS sphere monolayer on the substrate and (ii) the following potentiostatic electrodeposition of CeO2 on the PS sphere template in Ce(NO3)3 aqueous solutions. The structural morphologies of the deposit changed drastically depending on the Ce(NO3)3 concentration; i.e., spherical and needlelike shells were deposited. The deposit was formed only on the PS sphere surface because of an interaction between cationic cerium species and a sulfate group that was immobilized on the PS sphere surface. The spherical shell layer was assigned as CeO2, and the needlelike shells were composed of Ce(OH)3 needles formed on the CeO2 layer surface, indicating that the deposit species changes from CeO2 to Ce(OH)3 during electrodeposition only in a 1 mM Ce3+ solution. Deposition of Ce(OH)3 would begin when electrogenerated hydrogen peroxide was consumed by decomposition under reductive conditions and could no longer oxidize Ce3+ ions. The corresponding CeO2 hollow shells were obtained by thermal elimination of the PS sphere core and transformation of Ce(OH)3 into CeO2 while keeping their original shapes. PMID:20355893

  7. Effect of cerium doping on the electrical properties of ultrathin indium tin oxide films for application in touch sensors

    International Nuclear Information System (INIS)

    The electrical and microstructure properties of cerium doped indium tin oxide (ITO:Ce) ultrathin films were evaluated to assess their potential application in touch sensors. 10 to 150-nm ITO and ITO:Ce films were deposited on glass substrates (200 °C) by DC magnetron sputtering using different ITO targets (doped with CeO2: 0, 1, 3, 5 wt.%). ITO:Ce (doped with CeO2: 3 wt.%) films with thickness < 25 nm showed lower resistivity than ITO. This lower resistivity was accompanied by a significant increase in the Hall mobility despite a decrease in crystallinity. In addition, the surface morphology and wetting properties improved with increasing Ce concentration. This is related to an earlier transition from an island structure to continuous film formation caused by an increase in the initial nucleation density. - Highlights: • 10 to 150-nm InSnO2(ITO) and ITO:Ce thin films were deposited by sputtering. • ITO:Ce films with thickness < 25 nm showed lower resistivity than ITO. • Hall mobility was strongly affected by initial film formation. • Surface morphology and wetting property improved with increasing Ce concentration. • Such behavior is related to an earlier transition to continuous film formation

  8. Continuous precipitation of mineral products: influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides

    International Nuclear Information System (INIS)

    An automated experimental set-up with rapid mixers is used to study the influence of mixing conditions on the co-precipitation of cerium-zirconium mixed oxides. The intensity of mixing is controlled by the inlet flow rates of the reacting solutions. An engulfment model is used to estimate a mixing time from the measurement of a segregation index by the Villermaux-Dushman reaction system. Three geometries of Hartridge Roughton mixers are compared. Mixing performance is better when a separate mixing chamber upstream of a narrower outlet pipe is present. A better mixing decreases the maximal reducibility temperature of the material and increases the crystal strains of the particles calcined at 1100 C. This is probably due to a better homogenization of the particles content. The important incorporation of nitrates in the particle at the outlet of the mixers shows precipitation occurs while the mixing process is not finished. This experimental result was confirmed by numerical simulation and an estimation of sur-saturations during the mixing process. (author)

  9. Nanocasted synthesis of magnetic mesoporous iron cerium bimetal oxides (MMIC) as an efficient heterogeneous Fenton-like catalyst for oxidation of arsenite

    International Nuclear Information System (INIS)

    Highlights: • MMIC with large surface area and pore volume was synthesized via the hard template. • MMIC could be easily separated from aqueous solution with an external magnetic field. • MMIC presented excellent catalytic activity for the oxidation of As(III). • As(III) was mainly oxidized by surface-bound ·OHads and free ·OHfree radicals. • MMIC played a dual function role for the arsenic removal in aqueous solution. - Abstract: Magnetic mesoporous iron cerium bimetal oxides (MMIC) with large surface area and pore volume was synthesized via the hard template approach. This obtained MMIC was easily separated from aqueous solution with an external magnetic field and was proposed as a heterogeneous Fenton-like catalyst for oxidation of As(III). The MMIC presented excellent catalytic activity for the oxidation of As(III), achieving almost complete oxidation of 1000 ppb As(III) after 60 min and complete removal of arsenic species after 180 min with reaction conditions of 0.4 g/L catalyst, pH of 3.0 and 0.4 mM H2O2. Kinetics analysis showed that arsenic removal followed the pseudo-first order, and the pseudo-first-order rate constants increased from 0.0014 min−1 to 0.0548 min−1 as the H2O2 concentration increased from 0.04 mM to 0.4 mM. On the basis of the effects of XPS analysis and reactive oxidizing species, As(III) in aqueous solution was mainly oxidized by ·OH radicals, including the surface-bound ·OHads generated on the MMIC surface which were involved in ≡Fe2+ and ≡Ce3+, and free ·OHfree generation by soluble iron ions which were released from the MMIC into the bulk solution, and the generated As(V) was finally removed by MMIC through adsorption

  10. Effects of Cerium and Titanium Oxide Nanoparticles in Soil on the Nutrient Composition of Barley (Hordeum vulgare L.) Kernels

    Science.gov (United States)

    Pošćić, Filip; Mattiello, Alessandro; Fellet, Guido; Miceli, Fabiano; Marchiol, Luca

    2016-01-01

    The implications of metal nanoparticles (MeNPs) are still unknown for many food crops. The purpose of this study was to evaluate the effects of cerium oxide (nCeO2) and titanium oxide (nTiO2) nanoparticles in soil at 0, 500 and 1000 mg·kg−1 on the nutritional parameters of barley (Hordeum vulgare L.) kernels. Mineral nutrients, amylose, β-glucans, amino acid and crude protein (CP) concentrations were measured in kernels. Whole flour samples were analyzed by ICP-AES/MS, HPLC and Elemental CHNS Analyzer. Results showed that Ce and Ti accumulation under MeNPs treatments did not differ from the control treatment. However, nCeO2 and nTiO2 had an impact on composition and nutritional quality of barley kernels in contrasting ways. Both MeNPs left β-glucans unaffected but reduced amylose content by approximately 21%. Most amino acids and CP increased. Among amino acids, lysine followed by proline saw the largest increase (51% and 37%, respectively). Potassium and S were both negatively impacted by MeNPs, while B was only affected by 500 mg nCeO2·kg−1. On the contrary Zn and Mn concentrations were improved by 500 mg nTiO2·kg−1, and Ca by both nTiO2 treatments. Generally, our findings demonstrated that kernels are negatively affected by nCeO2 while nTiO2 can potentially have beneficial effects. However, both MeNPs have the potential to negatively impact malt and feed production. PMID:27294945

  11. Effects of Cerium and Titanium Oxide Nanoparticles in Soil on the Nutrient Composition of Barley (Hordeum vulgare L. Kernels

    Directory of Open Access Journals (Sweden)

    Filip Pošćić

    2016-06-01

    Full Text Available The implications of metal nanoparticles (MeNPs are still unknown for many food crops. The purpose of this study was to evaluate the effects of cerium oxide (nCeO2 and titanium oxide (nTiO2 nanoparticles in soil at 0, 500 and 1000 mg·kg−1 on the nutritional parameters of barley (Hordeum vulgare L. kernels. Mineral nutrients, amylose, β-glucans, amino acid and crude protein (CP concentrations were measured in kernels. Whole flour samples were analyzed by ICP-AES/MS, HPLC and Elemental CHNS Analyzer. Results showed that Ce and Ti accumulation under MeNPs treatments did not differ from the control treatment. However, nCeO2 and nTiO2 had an impact on composition and nutritional quality of barley kernels in contrasting ways. Both MeNPs left β-glucans unaffected but reduced amylose content by approximately 21%. Most amino acids and CP increased. Among amino acids, lysine followed by proline saw the largest increase (51% and 37%, respectively. Potassium and S were both negatively impacted by MeNPs, while B was only affected by 500 mg nCeO2·kg−1. On the contrary Zn and Mn concentrations were improved by 500 mg nTiO2·kg−1, and Ca by both nTiO2 treatments. Generally, our findings demonstrated that kernels are negatively affected by nCeO2 while nTiO2 can potentially have beneficial effects. However, both MeNPs have the potential to negatively impact malt and feed production.

  12. Germination and early plant development of ten plant species exposed to titanium dioxide and cerium oxide nanoparticles.

    Science.gov (United States)

    Andersen, Christian P; King, George; Plocher, Milt; Storm, Marjorie; Pokhrel, Lok R; Johnson, Mark G; Rygiewicz, Paul T

    2016-09-01

    Ten agronomic plant species were exposed to different concentrations of nano-titanium dioxide (nTiO2 ) or nano-cerium oxide (nCeO2 ) (0 μg/mL, 250 μg/mL, 500 μg/mL, and 1000 μg/mL) to examine potential effects on germination and early seedling development. The authors modified a standard test protocol developed for soluble chemicals (OPPTS 850.4200) to determine if such an approach might be useful for screening engineered nanomaterials (ENMs) and whether there were differences in response across a range of commercially important plant species to 2 common metal oxide ENMs. Eight of 10 species responded to nTiO2 , and 5 species responded to nCeO2 . Overall, it appeared that early root growth may be a more sensitive indicator of potential effects from ENM exposure than germination. The observed effects did not always relate to the exposure concentration, indicating that mass-based concentration may not fully explain the developmental effects of these 2 ENMs. The results suggest that nTiO2 and nCeO2 have different effects on early plant growth of agronomic species, with unknown effects at later stages of the life cycle. In addition, standard germination tests, which are commonly used for toxicity screening of new materials, may not detect the subtle but potentially more important changes associated with early growth and development in terrestrial plants. Environ Toxicol Chem 2016;35:2223-2229. Published 2016 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America. PMID:26773270

  13. The effect of surface implantation of yttrium and cerium upon the oxidation behaviour of stainless steels and aluminized coatings at high temperatures

    International Nuclear Information System (INIS)

    Assessments have been carried out on the extent to which the oxidation resistance of metals at high temperatures can be improved by surface implantation with yttrium or cerium. The elements were implanted to a concentration of 0.2 to 0.8%, to a depth of 0.2 μm. Yttrium implantation reduced the magnitude of oxidation and oxide spallation for a 20% Cr/25% Ni/Nb steel in carbon dioxide, at 800 to 8500C. The benefits approached those from a comparable yttrium alloy addition. The oxidation behaviour of a 15% Cr/4% Al steel, in air and carbon dioxide, at 1100 to 12000C, was improved markedly by a 0.86% yttrium alloy addition but yttrium implantation into the steel was without significant influence. The oxidation behaviour of aluminized coatings on three nickel based alloys in air, at 11000C, was also unaffected by implantations of either yttrium or cerium. The mechanisms associated with the results are discussed in detail. (author)

  14. Quaternary Oxide of Cerium, Terbium, Praseodymium and Zirconium for Three-Way Catalysts

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Oxygen storagecapacity (OSC), oxygen buffer capacity (OBC), X-ray diffraction and electron diffraction pattern, high resolution electron microscopy were used to study the quaternary oxides, i.e., of Ce, Tb, Pr and Zr. (Ce0.6Tb0.2Zr0.2O2-δ and Ce0.6Pr0.2Zr0.2O2-δ). OSC and OBC data indicate that these oxides have very good oxygen transfer capacity (OTC) and their pseudo-solid solutions exhibit fluorite-type structure. These oxides may act as a good candidate for three-way catalysts (TWC).

  15. Storage and characterization of the hydrogen in mixed oxides on base of cerium-nickel and zirconium or the aluminium

    International Nuclear Information System (INIS)

    The mixed oxides based on cerium-nickel and zirconium or aluminium are able to store large quantities of hydrogen, To determine nature, reactivity and properties of hydrogen species (spill-over, direct desorption), the solid were studied by different physicochemical techniques in the dried, calcined and partially reduced states: XRD, porosity, TGA, TPR, TPA, TPD, chemical titration and inelastic neutron scattering (INS). Solids are mainly meso-porous with a common pore size at 4 nm, They are constituted of CeO2 phase, Ce-Ni or Ce-Ni-Zr solid solution and of Ni(OH)2 in the dried state and NiO in the calcined state. The Ni species are in various environments and the strong interactions between the cations in solid solution and at different particles interface influence their reducibility and the creation of anionic vacancies. Activation in H2 in temperature is determining for hydrogen storage in the solid while calcination step is not necessary. INS Analyses evidence that the hydrogen species inserted during treatment in H2 are H+(OH-), hydride H- and H* (metallic nickel) species, present in various chemical environments, in particular for hydride species. All kinds of hydrogen species participate to the reaction during the chemical titration in agreement with the proposed hydrogenation mechanism. The study of the adsorption of hydrogen shows that this step is fast and in quantity of the same order as that measured by chemical titration. The direct desorption of H2 is very low, linked to the presence of hydrogen in interaction with metallic nickel (H*-.). Desorption of water is also observed, in parallel, corresponding to the elimination of groups. The hydride species are not desorbed. These various observations allow connecting hydrogen species properties with their localization in the structure and to model active sites. (author)

  16. Influence of the preparation method and the support on H2O2 electrogeneration using cerium oxide nanoparticles

    International Nuclear Information System (INIS)

    This work describes the influence of the preparation method and the carbon support using a low content of cerium oxide nanoparticles (CeO2/C 4%) on H2O2 electrogeneration via the oxygen reduction reaction (ORR). For this purpose, the polymeric precursor (PPM) and sol–gel (SGM) methods with Vulcan XC 72R (V) and Printex L6 (P) supports were employed. The materials were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XRD analysis identified two phases comprising CeO2 and CeO2−x. The smallest mean crystallite size was exhibited for the 4% CeO2/CPPMP material, which was estimated using the Debye–Scherrer equation to be 6 nm and 4 nm for the CeO2 and the CeO2−x phases, respectively, and was determined by TEM to be 5.9 nm. XPS analysis was utilized to compare the oxygen content of the 4% CeO2/CPPMP to Printex L6. The electrochemical analysis was accomplished using a rotating ring-disk electrode. The results showed that the 4% CeO2/C specimen, prepared by PPM and supported on Printex L6, was the best electrocatalyst for H2O2 production in 1 mol L−1 NaOH. This material showed the highest ring current, producing 88% H2O2 and transferring 2.2 electrons per O2 molecule via the ORR at the lowest onset potential. Additionally, the ring-current of the 4% CeO2/CPPMP material was higher than that of Vulcan XC 72R and Printex L6, the reference materials for H2O2 production, indicating the highest electrocatalytic activity for the 4% CeO2/CPPMP material

  17. Role of cerium-zirconium mixed oxides as catalysts for car pollution: a short review

    International Nuclear Information System (INIS)

    This article focuses on the role of mixed oxides in the Ce-Zr-O system, which is important as an excellent promoter for oxygen storage capacity in automotive three-way catalysts. In a model of Pt-alumina catalysts, there is a clear effect of CeO2-ZrO2 solid solution on NO and CO removal activities under dynamic air/fuel conditions. It is suggested that the design and development of automotive catalyst can be realized through research on complex oxides in Ce-Zr-O and related systems. (orig.)

  18. Poly(vinylpyrrolidone) as dispersing agent for cerium-gadolinium oxide (CGO) suspensions

    DEFF Research Database (Denmark)

    Marani, Debora; Sudireddy, Bhaskar Reddy; Nielsen, Lotte;

    2016-01-01

    The behaviour of selected poly(vinylpyrrolidone) grades to act as dispersant for ethanol-based ceriumgadolinium oxide suspensions was investigated and related to the molecular weight characteristics. The number, weight, and z-average molecular weights Mn, Mw, and Mz were determined by gel...

  19. EFFECT OF HEAT TREATMENT ON PITTING CORROSION RESISTANCE OF 6061 AL/SIC P COATED BY THE CERIUM OXIDE FILM IN 3.5 N NACL SOLUTION

    OpenAIRE

    Rajasekaran, S; UdayaShankar, N.; Nayaks, Jagannath

    2011-01-01

    One of the main drawbacks of 6061 Al/SiC P is its poor pitting corrosion resistance in the aggressive environment containing chloride ions, such as seawater, for example. The present article deals with the investigations of effects of aging on the corrosion behavior of 6061 Al/SiC P and of the heat treatment on the pitting corrosion resistance of 6061 Al/SiC P coated by cerium oxide prepared by chemical bath technique. Potentiodynamic polarization test was used to study the corrosion behavior...

  20. Investigation of heat-treatment and pre-treatment on microstructure and electrochemical properties of cerium nano-oxide films on AA7020-T6 by sol-gel methods

    Energy Technology Data Exchange (ETDEWEB)

    Hasannejad, H. [Materials Engineering Department, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of); Shahrabi, Taghi [Materials Engineering Department, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)], E-mail: tshahrabi34@modares.ac.ir; Rouhaghdam, Alireza Sabour; Aliofkhazraei, M.; Saebnoori, E. [Materials Engineering Department, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2008-07-15

    In this paper cerium nano-oxide films were applied on AA7020-T6 alloy by sol-gel method. Potentiodynamic polarization and EIS studies have been used to study the corrosion behavior of cerium oxide nano films in 3.5% NaCl. Microstructural and phase properties of cerium oxide were investigated by SEM and XRD. The results showed that heat-treatment temperature and pre-treatment have an important effect on microstructure and electrochemical properties of cerium nano-oxide films. It can be seen from the results that with increasing heat-treatment temperature from 150 to 300 deg. C, the corrosion resistance of the films increased. It is related to increase the condensation of the films with adding temperature. Also, it can be seen that with adding temperature from 300 to 400 deg. C, the corrosion resistance of the films decrease. This is an important case related to crystallization of the cerium oxide films between 300 and 400 deg. C which showed that crystallized ceria films illustrate less corrosion resistance with respect to an amorphous film. Although with applying cerium oxide films the corrosion resistance of the films increased but still the passive region of the ceria films was tiny. So that in this research especially pre-treatment (etching in NaOH solution for 1 min, washing with deionized water for 5 min, etching with acid solution which contained several acids (H{sub 2}SO{sub 4}, HF, HCl, H{sub 3}PO{sub 4}), washing with deionized water for 5 min and after that following the samples in boiling deionized water for 1 h) was applied on samples before ceria treatment. The results showed that after applying this pre-treatment the passive region of the films increased extremely. It is related to formation of the thick and porous alumina films after applying pre-treatment which are similar to millepore.

  1. Characteristics and mechanism study of cerium oxide based random access memories

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Cheng-Chih; Roy, Anupam; Rai, Amritesh; Chang, Yao-Feng; Banerjee, Sanjay K. [Microelectronics Research Center, The University of Texas at Austin, 10100 Burnet Rd. Bldg. 160, Austin, Texas 78758 (United States)

    2015-04-27

    In this work, low operating voltage and high resistance ratio of different resistance states of binary transition metal oxide based resistive random access memories (RRAMs) are demonstrated. Binary transition metal oxides with high dielectric constant have been explored for RRAM application for years. However, CeO{sub x} is considered as a relatively new material to other dielectrics. Since research on CeO{sub x} based RRAM is still at preliminary stage, fundamental characteristics of RRAM such as scalability and mechanism studies need to be done before moving further. Here, we show very high operation window and low switching voltage of CeO{sub x} RRAMs and also compare electrical performance of Al/CeO{sub x}/Au system between different thin film deposition methods and discuss characteristics and resistive switching mechanism.

  2. Influence of the synthesis parameters on the physico-chemical and catalytic properties of cerium oxide for application in the synthesis of diethyl carbonate

    International Nuclear Information System (INIS)

    Synthesis of cerium (IV) oxide by means of room temperature precipitation method was carried out. The effect of preparation variables such as synthesis time, calcination temperature and pH of the solution on resulting CeO2 properties was discussed. Moreover, the comparison of CeO2 samples prepared in a static and rotation mode of synthesis is presented. The solid catalysts were characterized by means of X-ray powder diffraction, scanning electron microscopy, transmission electron microscope, nitrogen physisorption, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy using pyridine as a probe molecule and temperature programmed desorption of CO2. Significant variations in physico-chemical properties of CeO2 by varying the preparation conditions were observed. Furthermore, the catalytic performances of CeO2 catalysts were compared in the synthesis of diethyl carbonate starting from ethanol and CO2 using butylene oxide as a dehydrating agent. The dependence of CeO2 properties on its catalytic activity is evaluated in detail. - Highlights: • Synthesis of cerium (IV) oxide by precipitation method. • Influence of synthesis time, calcination temperature, mode of stirring and solution pH on properties. • Characterization by XRD, SEM, TEM, nitrogen physisorption, XPS, FTIR. • Catalytic performance diethyl carbonate synthesis from ethanol and CO2

  3. Comparison of Titration ICP and XRF Spectrometry Methods in Determination of Cerium in Lens Polishing Powder

    International Nuclear Information System (INIS)

    Three analytical methods in determination of cerium in cerium oxide separated from monazite ore for producing lens polishing powder were compared. These methods are titration ICP and XRF spectrometry techniques. The cerium oxide sample with estimated 45% cerium content needed to be digested and converted into solution before the analysis. The analytical results shown significantly no difference between each method. However, the titration method was found to be more convenient and suitable for quality control in the production of cerium oxide as it does not require standard cerium and the complicated analytical instruments

  4. Calculations of thermodynamic data from spectroscopic data for oxides for cerium and neodymium

    International Nuclear Information System (INIS)

    A code to calculate thermodynamic functions of an ideal gas (at 1 atm pressure) from its spectroscopic data using statistical mechanics methods was commissioned, tested and verified. The code was used to calculate the thermodynamic functions for three fission-product oxides, Ce02, Ce202 and NdO2, for temperatures between 100 K and 3000 K and 0.1 MPa. High-temperature thermodynamic data of fission products are needed to calculate the source terms under accident conditions using fuel safety codes such as CHMWRK and F*A*C*T. (author)

  5. Nanocasted synthesis of magnetic mesoporous iron cerium bimetal oxides (MMIC) as an efficient heterogeneous Fenton-like catalyst for oxidation of arsenite

    Energy Technology Data Exchange (ETDEWEB)

    Wen, Zhipan [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China); Zhang, Yalei, E-mail: zhangyalei@tongji.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China); Dai, Chaomeng [College of Civil Engineering, Tongji University, Shanghai 200092 (China); Sun, Zhen [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China)

    2015-04-28

    Highlights: • MMIC with large surface area and pore volume was synthesized via the hard template. • MMIC could be easily separated from aqueous solution with an external magnetic field. • MMIC presented excellent catalytic activity for the oxidation of As(III). • As(III) was mainly oxidized by surface-bound ·OH{sub ads} and free ·OH{sub free} radicals. • MMIC played a dual function role for the arsenic removal in aqueous solution. - Abstract: Magnetic mesoporous iron cerium bimetal oxides (MMIC) with large surface area and pore volume was synthesized via the hard template approach. This obtained MMIC was easily separated from aqueous solution with an external magnetic field and was proposed as a heterogeneous Fenton-like catalyst for oxidation of As(III). The MMIC presented excellent catalytic activity for the oxidation of As(III), achieving almost complete oxidation of 1000 ppb As(III) after 60 min and complete removal of arsenic species after 180 min with reaction conditions of 0.4 g/L catalyst, pH of 3.0 and 0.4 mM H{sub 2}O{sub 2}. Kinetics analysis showed that arsenic removal followed the pseudo-first order, and the pseudo-first-order rate constants increased from 0.0014 min{sup −1} to 0.0548 min{sup −1} as the H{sub 2}O{sub 2} concentration increased from 0.04 mM to 0.4 mM. On the basis of the effects of XPS analysis and reactive oxidizing species, As(III) in aqueous solution was mainly oxidized by ·OH radicals, including the surface-bound ·OH{sub ads} generated on the MMIC surface which were involved in ≡Fe{sup 2+} and ≡Ce{sup 3+}, and free ·OH{sub free} generation by soluble iron ions which were released from the MMIC into the bulk solution, and the generated As(V) was finally removed by MMIC through adsorption.

  6. A rapid solvothermal synthesis of cerium oxide hollow spheres and characterization

    International Nuclear Information System (INIS)

    An easy and size controlled solvothermal synthesis of CeO2 hollow spheres is still a challenge in the area of materials synthesis. Here, CeO2 hollow spheres have been synthesized using PVA500 as a surfactant via solvothermal reaction followed by calcinations. The size of CeO2 hollow spheres could be controlled from 500 to 150 nm by changing the amounts of Ce(NO3)3·6H2O and PVA500. The possible growth mechanism of CeO2 hollow sphere was explained. The CO oxidation catalytic activity of the CeO2 hollow spheres were superior to that of the commercial CeO2 powder due to the high specific surface area and small crystallite size. - Graphical abstract: A rapid and easy way to prepare CeO2 hollow sphere with 150–500 nm in diameter was successfully achieved by solvothermal reaction. The prepared particles showed hollowness due to Ostwald ripening process. An improved catalytic activity was observed and discussed. Highlights: A rapid synthesis of CeO2 hollow spheres with diameter size from 15 to 500 nm. ► Cheap surfactant was used to prepare hollow spheres. ► Effect of temperature and surfactant ratio were investigated. ► Systematic characterization by XRD, FESEM, TEM, TG, FTIR and UV. ► CO oxidation analysis results showed better catalytic activity.

  7. Oxygen level: the dominant of resistive switching characteristics in cerium oxide thin films

    International Nuclear Information System (INIS)

    Currently, resistive switching mechanisms in metal oxide thin films are not clearly understood due to lack of solid evidence. In this work, the switching behaviour of the Au/CeO2/conductive glass structure was analysed, where reproducible and pronounced resistive switching characteristics were obtained. The role of oxygen vacancies in switching characteristics was investigated. The concentration of oxygen vacancies in the CeO2 thin films was controlled by post-annealing and monitored by x-ray photon spectroscopy. The reduction in the switching ratio and the intensity of the peak associated with oxygen concentration O 1s level after annealing treatment confirmed the dominating role of oxygen vacancies in switching behaviour.

  8. Cerium oxide as conversion coating for the corrosion protection of aluminum

    Directory of Open Access Journals (Sweden)

    JELENA GULICOVSKI

    2013-11-01

    Full Text Available CeO2 coatings were formed on the aluminum after Al surface preparation, by dripping the ceria sol, previously prepared by forced hydrolysis of Ce(NO34. The anticorrosive properties of ceria coatings were investigated by the electrochemical impedance spectroscopy (EIS during the exposure to 0.03 % NaCl. The morphology of the coatings was examined by the scanning electron microscopy (SEM. EIS data indicated considerably larger corrosion resistance of CeO2-coated aluminum than for bare Al. The corrosion processes on Al below CeO2 coating are subjected to more pronounced diffusion limitations in comparison to the processes below passive aluminum oxide film, as the consequence of the formation of highly compact protective coating. The results show that the deposition of ceria coatings is an effective way to improve corrosion resistance for aluminum.

  9. Selective side-chain oxidation of alkyl aromatic compounds catalyzed by cerium modified silver catalysts

    DEFF Research Database (Denmark)

    Beier, Matthias Josef; Schimmoeller, Bjoern; Hansen, Thomas Willum; Andersen, Jens Enevold Thaulov; Pratsinis, Sotiris E.; Grunwaldt, Jan-Dierk

    2010-01-01

    Silver supported on silica effectively catalyzes the aerobic side-chain oxidation of alkyl aromatic compounds under solvent-free conditions. Toluene, p-xylene, ethylbenzene and cumene were investigated as model substrates. Typically, the reaction was performed at ambient pressure; only for toluene...... an elevated pressure was required. Carboxylic acids, such as benzoic acid or p-toluic acid, additionally increased the reaction rate while CeO2 could act both as a promoter and an inhibitor depending on the substrate and the reaction conditions. Silver catalysts were prepared both by standard...... catalysis. In addition, flame-made catalysts were more stable against silver leaching compared to the impregnated catalysts. The structure of the silver catalysts was studied in detail both by X-ray absorption spectroscopy and transmission electron microscopy suggesting metallic silver to be required for...

  10. A novel technique for simultaneous diagnosis and radioprotection by radioactive cerium oxide nanoparticles. Study of cyclotron production of 137mCe

    International Nuclear Information System (INIS)

    Application of nanoparticles in nuclear medicine has aimed to develop diagnosis and therapeutic techniques. Cerium oxide nanoparticles (CNPs) are expected to be useful for protection of healthy tissue from radiation-induced harm and could serve therapeutic function. Among a variety of cerium radioisotopes, 137mCe (T1/2 = 34.4 h, IT (99.22%), β+ (0.779%)) could be a novel candidate radionuclide in the field of diagnosis owing to its appropriate half-life, 99.91% natural abundance of target and its intense gamma line at 254.29 keV. In this study, 137mCe excitation function via the natLa(p,3n) reaction was calculated by TALYS-1.2 and EMPIRE-3 codes. The excitation function calculations demonstrated that the natLa(p,3n)137mCe reaction leads to the formation of the 136/138Ce isotopic contamination in the 22-35 MeV energy range. Interestingly, the isotopic impurities of 137mCe could serve radio protector function. Overall results indicate that the cyclotron produced 137mCeO2 nanoparticles by irradiation of a target encompassing lanthanum oxide nanoparticles could be a potent alternative for conventional diagnostic radionuclides with simultaneous radioprotection capacity. (author)

  11. Growth and thermal properties of ultrathin cerium oxide layers on Rh(111)

    International Nuclear Information System (INIS)

    Full text: The growth morphology and structure and the thermal reduction of ultrathin ceria overlayers on Rh(111) have been investigated by LEED, STM, XPS and valence band resonant photoemission with use of synchrotron radiation. The ceria grows in form of ordered CeO2 crystallites following a Volmer-Weber island growth mode, with (111) faces parallel and orientationally aligned to the Rh(111) substrate. Very thin Ceria layers ( 3+ species, which appear to be dominantly located at the ceria - Rh interface. For ceria films thicker than 5 MLE stoichiometric CeO2 is detected in XPS. Annealing in vacuum leads to the formation of well-defined hexagonal island structures, accompanied by partial reduction and the formation of Ce3+ species at the surface with concomitant surface O vacancies. The degree of reduction depends on the oxide layer thickness, suggesting a promoting role of the ceria - Rh interface for the reduction process. At high temperature ( > 800 oC) the ceria decomposes and Ce-Rh surface alloy phases are detected. The surface alloying process is clearly identified in valence band resonant photoemission spectra. (author)

  12. Combination of supported bimetallic rhodium–molybdenum catalyst and cerium oxide for hydrogenation of amide

    International Nuclear Information System (INIS)

    Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6–7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh–MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2–8 MPa and 393–433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh–MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh–MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh–MoOx/SiO2, i.e. reducing the ratio of Mo–OH/Mo–O− sites. (focus issue paper)

  13. Combination of supported bimetallic rhodium-molybdenum catalyst and cerium oxide for hydrogenation of amide

    Science.gov (United States)

    Nakagawa, Yoshinao; Tamura, Riku; Tamura, Masazumi; Tomishige, Keiichi

    2015-02-01

    Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6-7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh-MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2-8 MPa and 393-433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh-MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh-MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh-MoOx/SiO2, i.e. reducing the ratio of Mo-OH/Mo-O- sites.

  14. Properties of cerium-zirconium mixed oxides partially substituted by neodymium: Comparison with Zr-Ce-Pr-O ternary oxides

    International Nuclear Information System (INIS)

    CeO2 doped with praseodymium, neodymium and/or zirconium atoms were prepared by coprecipitation and by the sol-gel method. Structural properties were investigated by in situ XRD and Raman spectroscopy while oxygen storage capacity (OSC) was measured by transient CO oxidation. All the compounds, except pure Nd2O3, have a fluorite-type structure as well as a Raman band at 560 cm-1 characteristic of the oxygen vacancies involving non-stoichiometric oxides. The lattice parameter under hydrogen, being dependent on the temperature, revealed two reduction mechanisms: one at a low temperature at the surface and another at a high temperature in the bulk. Ce-Nd binary oxides show a strong tendency towards crystallite aggregation, which reduces accessibility to gases and OSC properties. Zirconium improves the thermal resistance to sintering of both Ce-Nd and Ce-Pr oxides. The Zr-Ce-Pr-O followed by Zr-Ce-Nd-O compounds displaying high oxygen mobility at a low temperature, appear to be very promising for practical applications such as OSC materials. - Graphical abstract: Variation of oxygen vacancies under hydrogen on ternary oxides

  15. Pulsed laser deposition of bimetallic gold–platinum nanoparticles on cerium oxide and their characterisation by X-ray photoelectron spectroscopy and temperature-programmed desorption of isotopically labelled carbon monoxide

    Czech Academy of Sciences Publication Activity Database

    Plšek, Jan; Bastl, Zdeněk

    2013-01-01

    Roč. 109, MAR 2013 (2013), s. 109-118. ISSN 0021-9517 R&D Projects: GA ČR GA104/08/1501 Institutional support: RVO:61388955 Keywords : pulsed laser deposition * cerium oxide * Au-Pt nanostructures Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 6.073, year: 2013

  16. Nanostructured cerium oxide catalyst support: Effects of morphology on the electro activity of gold toward oxidative sensing of glucose

    International Nuclear Information System (INIS)

    We report on the fabrication of nanostructured CeO2-gold electrodes by means of laser ablation. The synthetic conditions were varied in order to obtain different morphologies of CeO2. The physical and chemical properties of the samples were studied by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The effect of the morphology of CeO2 on the electrocatalytic oxidation of glucose were studied by cyclic voltammetry and square-wave voltammetry. Among the various electrodes fabricated, the CeO2 coating produced under 10 mTorr of oxygen showed the best supporting catalytic properties for gold by displaying 44 μA cm−2 mM−1 sensitivity for glucose oxidation at near neutral pH values. The detection limit is as low as 10 μM. This electrochemical activity makes the optimized nanostructured electrode potentially useful for non-enzymatic sensing of glucose. (author)

  17. Modified semi-coke-supported cerium oxide-doped zinc ferrites for the removal of H{sub 2}S from coal gas

    Energy Technology Data Exchange (ETDEWEB)

    Mi, J.; Guo, T.; Zhu, Y.; Wang, J. [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan (China); Feng, G. [Shanghai Research Institute of Petrochemical Technology SINOPEC, Shanghai (China); Han, L. [Key Laboratory of Coal Science and Technology of Shanxi Province and Ministry of Education, Taiyuan University of Technology, Taiyuan (China); College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan (China)

    2012-09-15

    Cerium oxide-doped ZnFe{sub 2}O{sub 4} sorbents supported on modified semi-coke (MSC) were prepared to improve the desulfurization efficiency of zinc ferrites. The sulfidation tests of the ZnFe{sub 2}O{sub 4}/MSC sorbents with and without Ce were carried out using a fixed-bed reactor at 450 C. The effect of the CeO{sub 2}/ZnFe{sub 2}O{sub 4} molar ratio of the sorbents on the sulfur capacity was studied. The characteristics of the sorbents were analyzed by X-ray diffraction, N{sub 2} adsorption, scanning electron microscopy and X-ray photoelectron spectroscopy. The results showed that cerium oxide could greatly improve the desulfurization reactivity of the ZnFe{sub 2}O{sub 4}/MSC sorbents. The molar ratio of Ce to Zn and Fe influences the desulfurization reactivity, and a good sulfur capacity of the sorbent can be obtained with a Ce/Zn/Fe ratio of 4:4:1. It was also found that the addition of CeO{sub 2} could enlarge the surface area and the pore volume, thus improving the dispersion of active components. Ce doping results in an increment of the oxygen adsorbed on the sorbent surface, which facilitates the adsorption of H{sub 2}S. The Ce ions could act as carriers of the oxidation and reduction reactions and the oxygen transfer could be accelerated during the desulfurization process of coal gas. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Determining the Source of Water Vapor in a Cerium Oxide Electrochemical Oxygen Separator to Achieve Aviator Grade Oxygen

    Science.gov (United States)

    Graf, John; Taylor, Dale; Martinez, James

    2014-01-01

    More than a metric ton of water is transported to the International Space Station (ISS) each year to provide breathing oxygen for the astronauts. Water is a safe and compact form of stored oxygen. The water is electrolyzed on ISS and ambient pressure oxygen is delivered to the cabin. A much smaller amount of oxygen is used each year in spacesuits to conduct Extra Vehicular Activities (EVAs). Space suits need high pressure (>1000 psia) high purity oxygen (must meet Aviator Breathing Oxygen "ABO" specifications, >99.5% O2). The water / water electrolysis system cannot directly provide high pressure, high purity oxygen, so oxygen for EVAs is transported to ISS in high pressure gas tanks. The tanks are relatively large and heavy, and the majority of the system launch weight is for the tanks and not the oxygen. Extracting high purity oxygen from cabin air and mechanically compressing the oxygen might enable on-board production of EVA grade oxygen using the existing water / water electrolysis system. This capability might also benefit human spaceflight missions, where oxygen for EVAs could be stored in the form of water, and converted into high pressure oxygen on-demand. Cerium oxide solid electrolyte-based ion transport membranes have been shown to separate oxygen from air, and a supported monolithic wafer form of the CeO2 electrolyte membrane has been shown to deliver oxygen at pressures greater than 300 psia. These supported monolithic wafers can withstand high pressure differentials even though the membrane is very thin, because the ion transport membrane is supported on both sides (Fig 1). The monolithic supported wafers have six distinct layers, each with matched coefficients of thermal expansion. The wafers are assembled into a cell stack which allows easy air flow across the wafers, uniform current distribution, and uniform current density (Fig 2). The oxygen separation is reported to be "infinitely selective" to oxygen [1] with reported purity of 99.99% [2

  19. Stability of Commercial Small-Sized Cerium Oxide in the Presence of Biological Material: Dilucidating Relationships between Reactivity and Toxicity of Nanomaterials

    Science.gov (United States)

    Cervini-Silva, J.; Gilbert, B.; Fernandez-Lomelin, P.; Guzman-Mendoza, J.; Chavira, E.

    2007-05-01

    Cerium is the most abundant lanthanide and generally the only one to undergo redox reactions at the Earth's surface. Although rarely studied in natural environments, the redox chemistry of cerium may regulate metal toxicity. Unlike Ce(III) or other lanthanide ions, Ce(IV) has shown a remarkably efficacy to hydrolyze DNA. While Ce(IV) has been recognized as an important candidate to occupy peptidases catalytic centers, Ce(III) is virtually inactive for peptide hydrolysis. The selectivity of Ce as Ce(IV) relates to the specific coordination of water molecules and their orientation. Ce(IV) may bind selectivity to biomolecules to instigate conformation changes or cleavage of complexes, which affect metabolic pathways pivotal to growth and survival. For instance, Ce(IV) promotes the selective cleavage of RNA-type substrates, cyclic monophosphates, peptides, or monocleotides such as AMP, leading to mixtures of nucleosides and nucleobases. Association constants for Ce(IV)-DNA complexes are reported to be higher in magnitude for single stranded than double stranded DNA, while cleavage rates for either complexes are comparable. Complexation of Ce(IV) with mitoxantrone results in the intercalation of such complex into DNA, enabling mitoxantrone to bind effectively with DNA, along with concomitant conformational changes in the DNA double helix and inhibition of DNA synthesis. To the authors' knowledge, however, little information is available on the reactivity as it relates to toxicity of Ce-bearing nanoparticles widely used in nanotechnological applications. Here, we study molecular interactions between small-sized CeO2 and biomolecules(e.g., DNA, RNA, proteins) using carbon and cerium spectroscopy. Suspension stability as determined by aggregation kinetics was studied by Dynamic Light Scattering (DSL) and UV. In addition, acidophiles and fungi cultures were analyzed by nephelometry to estimate population density and growth rate values. Results show a progressive increase in

  20. Role of tantalum nitride as active top electrode in electroforming-free bipolar resistive switching behavior of cerium oxide-based memory cells

    International Nuclear Information System (INIS)

    Electroforming-free cerium oxide-based bipolar resistive switching memory devices have been deposited using radio frequency magnetron sputtering technique. These devices demonstrate two types of forming-free cells: some in the low-resistance state and the others in high-resistance state. The transmission electron microscopy and X-ray diffraction analyses illustrate the formation of tantalum oxynitride layer between tantalum nitride (TaN) and cerium oxide (CeOx), which looks to be responsible for the two types of cells as well as their memory performance. Ohmic and Poole-Frenkel conduction mechanisms are found to be responsible for charge transport in the low- and high-resistance states. The current-voltage characteristics and temperature dependence of resistance suggest that resistive switching mechanism in our TaN/CeOx/Pt devices may be explained by the model of connection and disconnection of filamentary paths made of oxygen vacancies. The reliability characteristics of TaN/CeOx/Pt devices indicate better endurance and stable retention performance at relatively lower programming voltages and larger memory window (OFF/ON resistance ratio ~ 103) at room temperature and at 100 °C. - Highlights: • Electroforming-free TaN/CeOx/Pt memory cells have been fabricated by sputtering. • Device exhibits good endurance, long data retention and high-resistance window (~ 103). • Voltages for SET and RESET transitions of our device exhibit narrow distribution. • The device is forming-free due to pre-existence of abundant oxygen vacancies. • TaN top electrode play major role in uniformity of resistive switching characteristics

  1. Role of tantalum nitride as active top electrode in electroforming-free bipolar resistive switching behavior of cerium oxide-based memory cells

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Muhammad, E-mail: ismailmalikbzu10@gmail.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Ahmed, Ejaz; Rana, Anwar Manzoor; Talib, Ijaz; Khan, Tahira [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Iqbal, Khalid [Department of Radiation Oncology, Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore (Pakistan); Nadeem, Muhammad Younus [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan)

    2015-05-29

    Electroforming-free cerium oxide-based bipolar resistive switching memory devices have been deposited using radio frequency magnetron sputtering technique. These devices demonstrate two types of forming-free cells: some in the low-resistance state and the others in high-resistance state. The transmission electron microscopy and X-ray diffraction analyses illustrate the formation of tantalum oxynitride layer between tantalum nitride (TaN) and cerium oxide (CeO{sub x}), which looks to be responsible for the two types of cells as well as their memory performance. Ohmic and Poole-Frenkel conduction mechanisms are found to be responsible for charge transport in the low- and high-resistance states. The current-voltage characteristics and temperature dependence of resistance suggest that resistive switching mechanism in our TaN/CeO{sub x}/Pt devices may be explained by the model of connection and disconnection of filamentary paths made of oxygen vacancies. The reliability characteristics of TaN/CeO{sub x}/Pt devices indicate better endurance and stable retention performance at relatively lower programming voltages and larger memory window (OFF/ON resistance ratio ~ 10{sup 3}) at room temperature and at 100 °C. - Highlights: • Electroforming-free TaN/CeO{sub x}/Pt memory cells have been fabricated by sputtering. • Device exhibits good endurance, long data retention and high-resistance window (~ 10{sup 3}). • Voltages for SET and RESET transitions of our device exhibit narrow distribution. • The device is forming-free due to pre-existence of abundant oxygen vacancies. • TaN top electrode play major role in uniformity of resistive switching characteristics.

  2. Optimization of process efficiency in cerium electrorefining

    International Nuclear Information System (INIS)

    Reactive metal electrorefining presents a number of problems that pose daunting obstacles to commercial operation. Typical reduction of reactive metal oxides or halide can introduce a variety of impurities such as iron, nickel, chromium, silicon, aluminum and various other metals which must be removed. This research program has addressed the various parameters of molten salt electrorefining of cerium metal to provide insight to this extremely important process. Cerium has been chosen as the surrogate for certain reactive metals on account of its similar electrochemical characteristics. The justification for such a choice has been investigated. The cell components and configuration, current efficiency of the process, purity of the cathodically deposited metal and the power requirement of the system have been optimized in a molten calcium chloride salt electrolyte using a molten, stirred impure metal anode. Various refractory crucible design and electrode materials have been studied to improve the process reliability. The equimolar NaKCl2 salt used in the electrorefining of some reactive metals is found to be inappropriate as a relatively high temperature is required to electrorefine cerium, i.e. melting point of Ce [798 C]. The homogeneity of the anode is controlled by the stirring at an optimized rate. This paper highlights the validity of cerium oxide and intermetallics of cerium as a surrogate for other reactive metal oxides or the respective intermetallics

  3. Physical characterization of post-deposition annealed metal-organic decomposed cerium oxide film spin-coated on 4H-silicon carbide

    International Nuclear Information System (INIS)

    Cerium oxide (CeO2) precursor, prepared by metal-organic decomposition method, was spin-coated on n-type 4H-SiC substrate. Effect of post-deposition annealing (600, 800, and 1000 oC) in argon ambient on physical properties of the deposited film (∼110 nm) was investigated. Refractive index (nf) of the film was measured by ellipsometer. Lorentz-Lorenz law was applied to estimate the film density (ρf). nf and ρf were increased with increasing annealing temperature. Film with defect-free surface had been revealed under field-emission scanning electron microscope. In order to study topography and surface roughness of the annealed oxides and SiC surfaces, atomic force microscope was used. The film showed an increment in surface roughness when the annealing temperature was increased. X-ray diffraction (XRD) was employed to detect the presence of crystalline phases and orientations in the films. Williamson-Hall plots were constructed from XRD line broadening, in which grain size (D) and microstrains were determined. Opposite relationship between D and microstrains was observed with the increase of annealing temperature. Coefficient of texture was calculated and used to measure preferred orientation of the film. All of the films annealed at different temperatures demonstrated (2 0 0)-preferred orientation.

  4. Effects of cerium dioxide nanoparticles in Oncorhynchus mykiss liver after an acute exposure: assessment of oxidative stress, genotoxicity and histological alterations

    Directory of Open Access Journals (Sweden)

    Ana Cristina Nunes

    2015-12-01

    Full Text Available At present cerium oxide nanoparticles (CeO2 NP have numerous applications ranging from industry to the household, leading to its wide distribution namely in the aquatic environment. The hereby study aimed to assess the toxic effects of CeO2 NPs in Oncorhynchus mykiss liver following an acute exposure (96h to three different concentrations (0.25, 2.5 and 25 mg/L in terms of the genotoxicity (comet assay, oxidative stress response (Catalase CAT; Glutathione S-Transferases GSTs; Thiobarbituric Acid Reactive Substances TBARS and histopathology. CeO2 NP exposure resulted in genotoxic damage in all exposure treatments, inhibition of CAT in the highest concentration and histopathological changes in all exposure concentrations with predominance of progressive and circulatory alterations. However TBARS and GSTs showed no significant differences comparatively to the control (unexposed group. The results suggest that CeO2 NP are able to cause genotoxicity, biochemical impairment and histological alterations in the liver of rainbow trout.

  5. Growth of cerium oxide thin layers for the manufacture of dosemeters and/or irradiation detectors by magnetron RF cathodic sputtering

    International Nuclear Information System (INIS)

    Oxide thin films deposited on silicon substrate are interesting for the manufacture of dosemeters and detectors of gas, humidity, temperature and irradiation. The irradiation dose measurement is required for assessing the risks and advantages of the use of ionizing radiations in fields such as biology, medicine and more generally in all the civil and military nuclear applications. According to literature, cerium oxide seems to be potentially interesting for the manufacture of dosemeters and/or irradiation detectors. The influence of the deposition parameters, such as the inter-electrodes distance, the temperature, the RF power, the work pressure, on the crystalline quality of the CeO2 layers deposited on a silicon (111) substrate by magnetron RF cathodic sputtering has been studied. All these thin films have been characterized by X-ray diffraction and by Raman spectroscopy. At the present time, studies are carried out on 'flash' annealing in order to improve the crystalline state of the thin layers. The aim is to study the influence of gamma and neutrons irradiations on the electric properties of capacities made of CeO2 thin films. (O.M.)

  6. Inhibition of MAP kinase/NF-kB mediated signaling and attenuation of lipopolysaccharide induced severe sepsis by cerium oxide nanoparticles.

    Science.gov (United States)

    Selvaraj, Vellaisamy; Nepal, Niraj; Rogers, Steven; Manne, Nandini D P K; Arvapalli, Ravikumar; Rice, Kevin M; Asano, Shinichi; Fankhanel, Erin; Ma, Jane J; Shokuhfar, Tolou; Maheshwari, Mani; Blough, Eric R

    2015-08-01

    Sepsis is a life threatening disease that is associated with high mortality. Existing treatments have failed to improve survivability in septic patients. The purpose of this present study is to evaluate whether cerium oxide nanoparticles (CeO2NPs) can prevent lipopolysaccharide (LPS) induced severe sepsis mortality by preventing hepatic dysfunction in male Sprague Dawley rats. Administration of a single dose (0.5 mg/kg) of CeO2NPs intravenously to septic rats significantly improved survival rates and functioned to restore body temperature, respiratory rate and blood pressure towards baseline. Treatment-induced increases in animal survivability were associated with decreased hepatic damage along with reductions in serum cytokines/chemokines, and diminished inflammatory related signaling. Kupffer cells and macrophage cells exposed to CeO2NPs exhibited decreases in LPS-induced cytokine release (TNF-α, IL-1β, IL-6, HMGB1) which were associated with diminished cellular ROS, reduced levels of nitric oxide synthase (iNOS), cyclooxygenase 2 (COX-2), and decreased nuclear factor-kappa light chain enhancer of activated B cells (NF-kB) transcriptional activity. The findings of this study indicate that CeO2NPs may be useful as a therapeutic agent for sepsis. PMID:25968464

  7. Methane Activation Mediated by a Series of Cerium-Vanadium Bimetallic Oxide Cluster Cations: Tuning Reactivity by Doping.

    Science.gov (United States)

    Ma, Jia-Bi; Meng, Jing-Heng; He, Sheng-Gui

    2016-04-18

    The reactions of cerium-vanadium cluster cations Cex Vy Oz (+) with CH4 are investigated by time-of-flight mass spectrometry and density functional theory calculations. (CeO2 )m (V2 O5 )n (+) clusters (m=1,2, n=1-5; m=3, n=1-4) with dimensions up to nanosize can abstract one hydrogen atom from CH4 . The theoretical study indicates that there are two types of active species in (CeO2 )m (V2 O5 )n (+) , V[(Ot )2 ](.) and [(Ob )2 CeOt ](.) (Ot and Ob represent terminal and bridging oxygen atoms, respectively); the former is less reactive than the latter. The experimentally observed size-dependent reactivities can be rationalized by considering the different active species and mechanisms. Interestingly, the reactivity of the (CeO2 )m (V2 O5 )n (+) clusters falls between those of (CeO2 )2-4 (+) and (V2 O5 )1-5 (+) in terms of C-H bond activation, thus the nature of the active species and the cluster reactivity can be effectively tuned by doping. PMID:26714587

  8. Evaluation of the role of oxidative stress, inflammation and apoptosis in the pulmonary and the hepatic toxicity induced by cerium oxide nanoparticles following intratracheal instillation in male Sprague-Dawley rats

    Science.gov (United States)

    Nalabotu, Siva Krishna

    The field of nanotechnology is rapidly progressing with potential applications in the automobile, healthcare, electronics, cosmetics, textiles, information technology, and environmental sectors. Nanomaterials are engineered structures with at least one dimension of 100 nanometers or less. With increased applications of nanotechnology, there are increased chances of exposure to manufactured nanomaterials. Recent reports on the toxicity of engineered nanomaterials have given scientific and regulatory agencies concerns over the safety of nanomaterials. Specifically, the Organization for Economic Co-operation and Development (OECD) has identified fourteen high priority nanomaterials for study. Cerium oxide (CeO2) nanoparticles are one among the high priority group. Recent data suggest that CeO2 nanoparticles may be toxic to lung cell lines in vitro and lung tissues in vivo. Other work has proposed that oxidative stress may play an important role in the toxicity; however, the exact mechanism of the toxicity, has to our knowledge, not been investigated. Similarly, it is not clear whether CeO2 nanoparticles exhibit systemic toxicity. Here, we investigate whether pulmonary exposure to CeO2 nanoparticles is associated with oxidative stress, inflammation and apoptosis in the lungs and liver of adult male Sprague-Dawley rats. Our data suggest that the intratracheal instillation of CeO2 nanoparticles can cause an increased lung weight to body weight ratio. Changes in lung weights were associated with the accumulation of cerium in the lungs, elevations in serum inflammatory markers, an increased Bax to Bcl-2 ratio, elevated caspase-3 protein levels, increased phosphorylation of p38-MAPK and diminished phosphorylation of ERK1/2-MAPK. Our findings from the study evaluating the possible translocation of CeO2 nanoparticles from the lungs to the liver suggest that CeO 2 nanoparticle exposure was associated with increased liver ceria levels, elevations in serum alanine transaminase

  9. Effects of pH and fulvic acids concentration on the stability of fulvic acids--cerium (IV) oxide nanoparticle complexes.

    Science.gov (United States)

    Oriekhova, Olena; Stoll, Serge

    2016-02-01

    The behavior of cerium (IV) oxide nanoparticles has been first investigated at different pH conditions. The point of zero charge was determined as well as the stability domains using dynamic light scattering, nanoparticle tracking analysis and scanning electron microscopy. A baseline hydrodynamic diameter of 180 nm was obtained indicating that individual CeO2 nanoparticles are forming small aggregates. Then we analyzed the particle behavior at variable concentrations of fulvic acids for three different pH-electrostatic scenarios corresponding to positive, neutral and negative CeO2 surface charges. The presence of fulvic acids was found to play a key role on the CeO2 stability via the formation of electrostatic complexes. It was shown that a small amount of fulvic acids (2 mg L(-1)), representative of environmental fresh water concentrations, is sufficient to stabilize CeO2 nanoparticles (50 mg L(-1)). When electrostatic complexes are formed between negatively charged FAs and positively charged CeO2 NPs the stability of such complexes is obtained with time (up to 7 weeks) as well as in pH changing conditions. Based on zeta potential variations we also found that the fulvic acids are changing the CeO2 acid-base surface properties. Obtained results presented here constitute an important outcome in the domain of risk assessment, transformation and removal of engineered nanomaterials released into the environment. PMID:26347935

  10. Effect of the Preparation Method on the Structural and Catalytic Properties of MnOx-CeO2 Manganese Cerium Mixed Oxides

    Directory of Open Access Journals (Sweden)

    Djadoun A.

    2013-09-01

    Full Text Available MnOx-CeO2 catalysts (molar ratio Mn/Ce = 1 were prepared using two methods: co-precipitation and citrate methods. The prepared solids were calcined at 500°C, and characterized by XRD, nitrogen adsorption-desorption technique and SEM morphological, they were, then, tested in the toluene combustion reaction. The catalytic performances of the prepared solids were evaluated in the temperature range 150-400° C. The XRD analysis of the two solids showed that the only crystalline phase detected is cerium oxide. BET surface area measurements showed that the incorporation of manganese led to an increase in the specific surface area of ceria, the solid prepared by the co-precipitation method led to the highest specific surface area (156 m²/g. The solids showed good performances in the toluene combustion reaction that depend strongly on the preparation method. The best catalytic activity was obtained for the catalyst prepared by the citrate method achieving a complete conversion of toluene at 250 ° C.

  11. Initial in vitro screening approach to investigate the potential health and environmental hazards of Envirox™ – a nanoparticulate cerium oxide diesel fuel additive

    Directory of Open Access Journals (Sweden)

    Whittingham Andrew

    2007-12-01

    Full Text Available Abstract Nanotechnology is the new industrial revolution of the 21st Century as the various processes lead to radical improvements in medicine, manufacturing, energy production, land remediation, information technology and many other everyday products and applications. With this revolution however, there are undoubted concerns for health, safety and the environment which arise from the unique nature of materials and processes at the nanometre scale. The in vitro assays used in the screening strategy are all validated, internationally accepted protocols and provide a useful indication of potential toxicity of a chemical as a result of effects on various toxicological endpoints such as local site of contact (dermal irritation, general cytotoxicity and mutagenicity. The initial in vitro screening strategy described in this paper to investigate the potential health implications, if any, which may arise following exposure to one specific application of nanoparticulate cerium oxide used as a diesel fuel borne catalyst, reflects a precautionary approach and the results will inform judgement on how best to proceed to ensure safe use.

  12. 电化学阻抗谱法研究铈改性TiO2纳米管阵列光电极裂解水产氢动力学%Dynamics Study on the Cerium and Oxidative Cerium Modified TiO2 Nanotube Arrays for Hydrogen Production by Water Splitting Using Electrochemical Impedance Spectrum

    Institute of Scientific and Technical Information of China (English)

    张胜寒; 梁可心; 檀玉

    2012-01-01

    TiO2 nanotube arrays photoelectrodes were prepared by anode oxidation on pure Ti sheet. The donor material glycol (C2H6O2) added in the anode electrolyte significantly reduced the charge transfer impedance of TiO2 nanotubes to promote the photocatalytic water splitting for hydrogen production. TiO2 nanotube arrays electrodes were modified by cerium and oxidative cerium with electrochemical deposition and anodic oxidation. The fiat band potential moves to the negative potential direction after modification. Electrochemical impedance spectrum (EIS) measurement was used to investigate the electron transfer characteristic in photoelectrodes and the interface characteristic in the photoelectrochemical cell (PEC) for hydrogen production. Arcs of EIS and corresponding electrode processes were discussed. Dynamic parameters of the electrodes were calculated by reasonable electrical equivalent circuit fitting. The results indicate that TiO2 nanotube arrays electrode modified by cerium and oxidative cerium could largely decrease the electron transfer resistance which contributes to hydrogen production. The mechanism of the cerium and oxidative cerium acting on TiO2 nanotube arrays to promote charge transfer is discussed.%通过阳极氧化法在纯钛板上制备TiO2纳米管阵列电极.在光电化学电解池阳极中加入供电子物质乙二醇,显著减小了TiO2纳米管的电荷传递阻抗,促进了光电催化裂解水产氢反应.采用阴极电沉积和阳极氧化法制备了单质铈和氧化铈共同改性的TiO2纳米管阵列半导体光阳极,其平带电位向电负方向移动.采用电化学阻抗谱法(EIS)对改性后TiO2纳米管阵列在光电催化裂解水产氢中的电子传输性能以及界面性质进行了表征,确定了各阻抗弧对应的电极过程.采用合理的等效电路模型计算了电极的电子传输动力学参数.结果表明,经铈改性后的TiO2纳米管阵列膜电阻明显减小,

  13. Effect of cerium addition on oxidation behavior of 2SCr20Ni alloy under lowoxygen partial pressure

    Institute of Scientific and Technical Information of China (English)

    SHAO Mingzeng; CUI Lishan; ZHENG Yanjun; XING Linlin

    2012-01-01

    The influence of Ce addition on the oxidation behavior of 25Cr20Ni alloy at 950 ℃ under low oxygen partial pressure was investigated.The oxidized samples were characterized by using X-ray diffraction (XRD),scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDS),and scratch tester to obtain the oxide phases,morphology,thickness,composition and adhesion property of the oxide scales.The experiment results indicated that a small amount of Ce addition (0.02 wt.% or 0.05 wt.%) promoted oxidation resistance and inhibited the growth of the needlelike oxide.The Ce addition also decreased the formation of MnCr2O4 but promoted the SiO2 formation underneath the Cr2O3,which largely contributed to the improvement of oxide scale spallation resistance.For the sample with 0.3 wt.% Ce addition,the oxidation rate significantly increased and the spallation resistance of the oxide scale decreased.

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

    Science.gov (United States)

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

    2016-07-28

    The electronic structures of several small Ce-Pt oxide complexes were explored using a combination of anion photoelectron (PE) spectroscopy and density functional theory calculations. Pt and Pt2 both accept electron density from CeO diatomic molecules, in which the cerium atom is in a lower-than-bulk oxidation state (+2 versus bulk +4). Neutral [CeO]Pt and [CeO]Pt2 complexes are therefore ionic, with electronic structures described qualitatively as [CeO(+2)]Pt(-2) and [CeO(+)]Pt2 (-), respectively. The associated anions are described qualitatively as [CeO(+)]Pt(-2) and [CeO(+)]Pt2 (-2), respectively. In both neutrals and anions, the most stable molecular structures determined by calculations feature a distinct CeO moiety, with the positively charged Ce center pointing toward the electron rich Pt or Pt2 moiety. Spectral simulations based on calculated spectroscopic parameters are in fair agreement with the spectra, validating the computationally determined structures. In contrast, when Pt is coupled with CeO2, which has no Ce-localized electrons that can readily be donated to Pt, the anion is described as [CeO2]Pt(-). The molecular structure predicted computationally suggests that it is governed by charge-dipole interactions. The neutral [CeO2]Pt complex lacks charge-dipole stabilizing interactions, and is predicted to be structurally very different from the anion, featuring a single Pt-O-Ce bridge bond. The PE spectra of several of the complexes exhibit evidence of photodissociation with Pt(-) daughter ion formation. The electronic structures of these complexes are related to local interactions in Pt-ceria catalyst-support systems. PMID:27475371

  15. EPR spin trapping evaluation of ROS production in human fibroblasts exposed to cerium oxide nanoparticles: evidence for NADPH oxidase and mitochondrial stimulation.

    Science.gov (United States)

    Culcasi, Marcel; Benameur, Laila; Mercier, Anne; Lucchesi, Céline; Rahmouni, Hidayat; Asteian, Alice; Casano, Gilles; Botta, Alain; Kovacic, Hervé; Pietri, Sylvia

    2012-09-30

    To better understand the antioxidant (enzyme mimetic, free radical scavenger) versus oxidant and cytotoxic properties of the industrially used cerium oxide nanoparticles (nano-CeO(2)), we investigated their effects on reactive oxygen species formation and changes in the antioxidant pool of human dermal and murine 3T3 fibroblasts at doses relevant to chronic inhalation or contact with skin. Electron paramagnetic resonance (EPR) spin trapping with the nitrone DEPMPO showed that pretreatment of the cells with the nanoparticles dose-dependently triggered the release in the culture medium of superoxide dismutase- and catalase-inhibitable DEPMPO/hydroxyl radical adducts (DEPMPO-OH) and ascorbyl radical, a marker of ascorbate depletion. This DEPMPO-OH formation occurred 2 to 24 h following removal of the particles from the medium and paralleled with an increase of cell lipid peroxidation. These effects of internalized nano-CeO(2) on spin adduct formation were then investigated at the cellular level by using specific NADPH oxidase inhibitors, transfection techniques and a mitochondria-targeted antioxidant. When micromolar doses of nano-CeO(2) were used, weak DEPMPO-OH levels but no loss of cell viability were observed, suggesting that cell signaling mechanisms through protein synthesis and membrane NADPH oxidase activation occurred. Incubation of the cells with higher millimolar doses provoked a 25-60-fold higher DEPMPO-OH formation together with a decrease in cell viability, early apoptosis induction and antioxidant depletion. These cytotoxic effects could be due to activation of both the mitochondrial source and Nox2 and Nox4 dependent NADPH oxidase complex. Regarding possible mechanisms of nano-CeO(2)-induced free radical formation in cells, in vitro EPR and spectrophotometric studies suggest that, contrary to Fe(2+) ions, the Ce(3+) redox state at the surface of the particles is probably not an efficient catalyst of hydroxyl radical formation by a Fenton-like reaction

  16. Fabrication of catalytically active nanocrystalline samarium (Sm)-doped cerium oxide (CeO2) thin films using electron beam evaporation

    International Nuclear Information System (INIS)

    Samarium (Sm)-doped cerium oxide (CeO2) thin films were fabricated using electron beam evaporation technique. The synthesized films were deposited either on glass or ITO substrates and studied their nature by annealing at different temperatures. The optical properties and other morphological studies were done by UV–Vis, XRD, XPS, SEM, EDS, and FT-IR analysis. XRD and XPS analysis clearly confirm the presence of Sm in the ceria site. From the SEM study, it was found that after annealing at high temperature (∼300 or 500 °C), the particles size was reduced due to breakdown of large aggregates of particles which is also confirmed from UV–Vis, XPS, and XRD analyses. The FT-IR study proves the presence of –COO–, –OH, or ammonium group on the particles surface. The deposition of Sm-doped CeO2 nanomaterials was found more feasible on ITO substrate compared to that of glass substrate in terms of stability and depth of film thickness. The Sm-doped CeO2 nanomaterial acts as a re-usable catalyst for the reduction of organic dye molecules in the presence of NaBH4. The catalysis rate was compared by considering the electron transfer process during the reduction. The synthesized Sm-doped CeO2 thin films might find wide variety of applications in various emerging fields like solid oxide fuel cells (SOFCs), oxygen sensor or as catalyst in different types of organic and inorganic catalytic reactions. The fabrication process is very simple, straightforward, less time consuming, and cost effective.Graphical Abstract

  17. Probing the cerium/cerium hydride interface using nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Brierley, Martin, E-mail: martin.brierley@awe.co.uk [Atomic Weapons Establishment, Aldermaston, Berkshire RG7 4PR (United Kingdom); University of Manchester, Manchester M13 9PL (United Kingdom); Knowles, John, E-mail: john.knowles@awe.co.uk [Atomic Weapons Establishment, Aldermaston, Berkshire RG7 4PR (United Kingdom)

    2015-10-05

    Highlights: • A disparity exists between the minimum energy and actual shape of a cerium hydride. • Cerium hydride is found to be harder than cerium metal by a ratio of 1.7:1. • A zone of material under compressive stress was identified surrounding the hydride. • No distribution of hardness was apparent within the hydride. - Abstract: A cerium hydride site was sectioned and the mechanical properties of the exposed phases (cerium metal, cerium hydride, oxidised cerium hydride) were measured using nanoindentation. An interfacial region under compressive stress was observed in the cerium metal surrounding a surface hydride that formed as a consequence of strain energy generated by the volume expansion associated with precipitation of the hydride phase.

  18. Probing the cerium/cerium hydride interface using nanoindentation

    International Nuclear Information System (INIS)

    Highlights: • A disparity exists between the minimum energy and actual shape of a cerium hydride. • Cerium hydride is found to be harder than cerium metal by a ratio of 1.7:1. • A zone of material under compressive stress was identified surrounding the hydride. • No distribution of hardness was apparent within the hydride. - Abstract: A cerium hydride site was sectioned and the mechanical properties of the exposed phases (cerium metal, cerium hydride, oxidised cerium hydride) were measured using nanoindentation. An interfacial region under compressive stress was observed in the cerium metal surrounding a surface hydride that formed as a consequence of strain energy generated by the volume expansion associated with precipitation of the hydride phase

  19. Cerium tartrate as a corrosion inhibitor for AA 2024-T3

    International Nuclear Information System (INIS)

    Highlights: • Cerium tartrate was found to be an effective inhibitor for AA 2024-T3. • Both anodic and cathodic inhibitions were present during the corrosion process. • The corrosion of Al2CuMg phase was well inhibited by cerium tartrate. - Abstract: A new corrosion inhibitor, cerium tartrate, was synthetized. The inhibition behavior of cerium tartrate for 2024-T3 aluminum alloy was investigated in 0.05 M NaCl solution. The immersion tests indicate that the corrosion of Al2CuMg phase was well inhibited. The electrochemical results show that both anodic and cathodic inhibitions are present during the corrosion process. The surface characterizations reveal that the protective film of cerium tartrate inhibits the dealloying of Al2CuMg phase in the initial stage, and then cerium ions transform to cerium oxide/hydroxides and appear at the Al2CuMg phase, blocking the further corrosion at those corrosion sites

  20. Humic Substances-dependent Aggregation and Transport of Cerium Oxide Nanoparticles in Porous Media at Different pHs and Ionic Strengths

    Science.gov (United States)

    Mu, L.; Jacobson, A. R.; Darnault, C. J. G.

    2015-12-01

    Cerium oxide nanoparticles (CeO2 NPs) are commonly used in several fields and industries, such as chemical and pharmaceutical, due to both their physical and chemical properties. For example, they are employed in the manufacturing of catalysts, as fuel additives, and as polishing agents. The release and exposure to CeO2 NPs can occur during their fabrication, application, and waste disposal, as well as through their life-cycle and accidents. Therefore, the assessment of the dynamic nature of CeO2 NPs stability and mobilty in the environment is of paramount importance to establish the environmental and public health risks associated with their inevitable release in the environment. Humic substances are a key element of soils and have been revealed to possibly affect the fate and transport of nanoparticles in soils. Consequently, our present research aims at investigating the influence that different pHs, monovalent and divalent cations, Suwannee River humic acid, and Suwanee River fulvic acid have on the aggregation, transport, and deposition of CeO2 NPs. Batch studies performed with different concentrations of humic and fulvic acids associated with a wide spectrum of pHs and ionic strengths were examined. Key variables from these batch studies were then examined to simulate experimental conditions commonly encountered in the soil-water system to conduct column transport experiments in order to establish the fate and transport of CeO2 NPs in saturated porous media, which is a critical phase in characterizing the behavior of CeO2 NPs in subsurface environmental systems.

  1. Influence of a Cerium Surface Treatment on the Oxidation Behavior of Cr2O3-Forming Alloys (title on slides varies: Oxidation Behavior of Cerium Surface Treated Chromia Forming Alloys)

    International Nuclear Information System (INIS)

    Current goals of the U.S. Department of Energy's Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760 C. This temperature will require the construction of boiler and turbine components from austenitic stainless steels and nickel alloys. Many of the alloys being considered for use are primarily Cr2O3 forming alloys [1-4]. It is well known that the addition of a small amount of reactive elements, such as the rare earths elements Ce, La, and Y, can significantly improve the high temperature oxidation resistance of both iron- and nickel- base alloys. A list of the benefits of the reactive element effect include: (i) slowing scale growth, (ii) enhancing scale adhesion; and (iii) stabilizing Cr2O3 formation at lower Cr levels. The incorporation of the reactive element can be made in the melt or through a surface infusion or surface coating. Surface modifications allow for the concentration of the reactive element at the surface where it can provide the most benefit. This paper will detail a Ce surface treatment developed at NETL that improves the high temperature oxidation resistance of Cr2O3 forming alloys. The treatment consists of painting, dip coating, or spraying the alloy surface with a slurry containing CeO2 and a halide activator followed by a thermal treatment in a mild (x10-3 Torr) vacuum. During treatment the CeO2 reacts with the alloy to for a thin CrCeO3-type scale on the alloy surface. Upon subsequent oxidation, scale growth occurs at a reduced rate on alloys in the surface treated condition compared to those in the untreated condition

  2. Redox Reactivity of Cerium Oxide Nanoparticles Induces the Formation of Disulfide Bridges in Thiol-Containing Biomolecules.

    Science.gov (United States)

    Rollin-Genetet, Françoise; Seidel, Caroline; Artells, Ester; Auffan, Mélanie; Thiéry, Alain; Vidaud, Claude

    2015-12-21

    The redox state of disulfide bonds is implicated in many redox control systems, such as the cysteine-cystine couple. Among proteins, ubiquitous cysteine-rich metallothioneins possess thiolate metal binding groups susceptible to metal exchange in detoxification processes. CeO2 NPs are commonly used in various industrial applications due to their redox properties. These redox properties that enable dual oxidation states (Ce(IV)/Ce(III)) to exist at their surface may act as oxidants for biomolecules. The interaction among metallothioneins, cysteine, and CeO2 NPs was investigated through various biophysical approaches to shed light on the potential effects of the Ce(4+)/Ce(3+) redox system on the thiol groups of these biomolecules. The possible reaction mechanisms include the formation of a disulfide bridge/Ce(III) complex resulting from the interaction between Ce(IV) and the thiol groups, leading to metal unloading from the MTs, depending on their metal content and cluster type. The formation of stable Ce(3+) disulfide complexes has been demonstrated via their fluorescence properties. This work provides the first evidence of thiol concentration-dependent catalytic oxidation mechanisms between pristine CeO2 NPs and thiol-containing biomolecules. PMID:26566067

  3. Determination of plutonium in nitric acid solutions - Method by oxidation by cerium(IV), reduction by iron(II) ammonium sulfate and amperometric back-titration with potassium dichromate

    International Nuclear Information System (INIS)

    This International Standard specifies a precise and accurate analytical method for determining plutonium in nitric acid solutions. Plutonium is oxidized to plutonium(VI) in a 1 mol/l nitric acid solution with cerium(IV). Addition of sulfamic acid prevents nitrite-induced side reactions. The excess of cerium(IV) is reduced by adding a sodium arsenite solution, catalysed by osmium tetroxide. A slight excess of arsenite is oxidized by adding a 0.2 mol/l potassium permanganate solution. The excess of permanganate is reduced by adding a 0.1 mol/l oxalic acid solution. Iron(III) is used to catalyse the reduction. A small excess of oxalic acid does not interfere in the subsequent plutonium determination. These reduction and oxidation stages can be followed amperometrically and the plutonium is left in the hexavalent state. The sulfuric acid followed by a measured amount of standardized iron(II) ammonium sulfate solution in excess of that required to reduce the plutonium(VI) to plutonium(IV) is added. The excess iron(II) and any plutonium(III) formed to produce iron(III) and plutonium(IV) is amperometrically back-titrated using a standard potassium dichromate solution. The method is almost specifically for plutonium. It is suitable for the direct determination of plutonium in materials ranging from pure product solutions, to fast reactor fuel solutions with a uranium/plutonium ratio of up to 10:1, either before or after irradiation

  4. Pharmacological potential of cerium oxidenanoparticles

    Science.gov (United States)

    Celardo, Ivana; Pedersen, Jens Z.; Traversa, Enrico; Ghibelli, Lina

    2011-04-01

    Nanotechnology promises a revolution in pharmacology to improve or create ex novo therapies. Cerium oxidenanoparticles (nanoceria), well-known as catalysts, possess an astonishing pharmacological potential due to their antioxidant properties, deriving from a fraction of Ce3+ ions present in CeO2. These defects, compensated by oxygen vacancies, are enriched at the surface and therefore in nanosized particles. Reactions involving redox cycles between the Ce3+ and Ce4+oxidation states allow nanoceria to react catalytically with superoxide and hydrogen peroxide, mimicking the behavior of two key antioxidant enzymes, superoxide dismutase and catalase, potentially abating all noxious intracellularreactive oxygen species (ROS) via a self-regenerating mechanism. Hence nanoceria, apparently well tolerated by the organism, might fight chronic inflammation and the pathologies associated with oxidative stress, which include cancer and neurodegeneration. Here we review the biological effects of nanoceria as they emerge from in vitro and in vivo studies, considering biocompatibility and the peculiar antioxidant mechanisms.

  5. Tuning Reactivity and Electronic Properties through Ligand Reorganization within a Cerium Heterobimetallic Framework

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, Jerome R.; Gordon, Zachary; Booth, Corwin H.; Carroll, Patrick J.; Walsh, Patrick J.; Schelter, Eric J.

    2014-06-24

    Cerium compounds have played vital roles in organic, inorganic, and materials chemistry due to their reversible redox chemistry between trivalent and tetravalent oxidation states. However, attempts to rationally access molecular cerium complexes in both oxidation states have been frustrated by unpredictable reactivity in cerium(III) oxidation chemistry. Such oxidation reactions are limited by steric saturation at the metal ion, which can result in high energy activation barriers for electron transfer. An alternative approach has been realized using a rare earth/alkali metal/1,1'-BINOLate (REMB) heterobimetallic framework, which uses redox-inactive metals within the secondary coordination sphere to control ligand reorganization. The rational syntheses of functionalized cerium(IV) products and a mechanistic examination of the role of ligand reorganization in cerium(III) oxidation are presented.

  6. Cerium oxide nanoparticles, combining antioxidant and UV shielding properties, prevent UV-induced cell damage and mutagenesis

    Science.gov (United States)

    Caputo, Fanny; de Nicola, Milena; Sienkiewicz, Andrzej; Giovanetti, Anna; Bejarano, Ignacio; Licoccia, Silvia; Traversa, Enrico; Ghibelli, Lina

    2015-09-01

    Efficient inorganic UV shields, mostly based on refracting TiO2 particles, have dramatically changed the sun exposure habits. Unfortunately, health concerns have emerged from the pro-oxidant photocatalytic effect of UV-irradiated TiO2, which mediates toxic effects on cells. Therefore, improvements in cosmetic solar shield technology are a strong priority. CeO2 nanoparticles are not only UV refractors but also potent biological antioxidants due to the surface 3+/4+ valency switch, which confers anti-inflammatory, anti-ageing and therapeutic properties. Herein, UV irradiation protocols were set up, allowing selective study of the extra-shielding effects of CeO2vs. TiO2 nanoparticles on reporter cells. TiO2 irradiated with UV (especially UVA) exerted strong photocatalytic effects, superimposing their pro-oxidant, cell-damaging and mutagenic action when induced by UV, thereby worsening the UV toxicity. On the contrary, irradiated CeO2 nanoparticles, via their Ce3+/Ce4+ redox couple, exerted impressive protection on UV-treated cells, by buffering oxidation, preserving viability and proliferation, reducing DNA damage and accelerating repair; strikingly, they almost eliminated mutagenesis, thus acting as an important tool to prevent skin cancer. Interestingly, CeO2 nanoparticles also protect cells from the damage induced by irradiated TiO2, suggesting that these two particles may also complement their effects in solar lotions. CeO2 nanoparticles, which intrinsically couple UV shielding with biological and genetic protection, appear to be ideal candidates for next-generation sun shields.

  7. Visible light activated photocatalytic degradation of tetracycline by a magnetically separable composite photocatalyst: Graphene oxide/magnetite/cerium-doped titania.

    Science.gov (United States)

    Cao, Muhan; Wang, Peifang; Ao, Yanhui; Wang, Chao; Hou, Jun; Qian, Jin

    2016-04-01

    In this study, magnetic graphene oxide-loaded Ce-doped titania (MGO-Ce-TiO2) hybridized composite was prepared by a facile method. The as-prepared samples exhibited good adsorption capacity, high visible-light photoactive and magnetic separability as a novel photocatalyst in the degradation of tetracyclines (TC). The intermediate products and photocatalytic route of TC were proposed based on the analysis results of LC-MS. Moreover, the repeatability of the photoactivity with the use of MGO-Ce-TiO2 was investigated in the multi-round experiments with the assistance of an applied magnetic field. Therefore, the prepared composite photocatalysts were considered as a kind of promising photocatalyst in a suspension reaction system, in which they can offer effectively recovery ability. The effect of MGO content on the photocatalytic performance was also studied, and an optimum content was obtained. PMID:26799623

  8. Comparison of the high-pressure behavior of the cerium oxides C e2O3 and Ce O2

    Science.gov (United States)

    Lipp, M. J.; Jeffries, J. R.; Cynn, H.; Park Klepeis, J.-H.; Evans, W. J.; Mortensen, D. R.; Seidler, G. T.; Xiao, Y.; Chow, P.

    2016-02-01

    The high-pressure behavior of C e2O3 was studied using angle-dispersive x-ray diffraction to 70 GPa and compared with that of Ce O2 . Up to the highest pressure C e2O3 remains in the hexagonal phase (space group 164, P 3 ¯2 /m 1 ) typical for the lanthanide sesquioxides. A theoretically predicted phase instability for 30 GPa is not observed. The isothermal bulk modulus and its pressure derivative for the quasihydrostatic case are B0=111 ±2 GPa ,B0'=4.7 ±0.3 , and for the case without pressure-transmitting medium B0=104 ±4 GPa ,B0'=6.5 ±0.4 . Starting from ambient-pressure magnetic susceptibility measurements for both oxides in highly purified form, we find that the Ce atom in C e2O3 behaves like a trivalent C e3 + ion (2.57 μB per Ce atom) in contrast to previously published data. Since x-ray emission spectroscopy of the L γ (4 d3 /2→2 p1 /2 ) transition is sensitive to the 4 f -electron occupancy, we also followed the high-pressure dependence of this line for both oxides up to 50 GPa. No change of the respective line shape was observed, indicating that the 4 f -electron configuration is stable for both materials. We posit from this data that the 4 f electrons do not drive the volume collapse of Ce O2 from the high-symmetry, low-pressure fluorite structure to the lower-symmetry orthorhombic phase.

  9. Novel solid-state route to nanostructured tin, zinc and cerium oxides as potential materials for sensors.

    Science.gov (United States)

    Diaz, C; Platoni, S; Molina, A; Valenzuela, M L; Geaney, H; O'Dwyer, C

    2014-09-01

    Solid-state sensor nanostructured materials (SnO2, ZnO and CeO2) have been prepared by pyrolysis of macromolecular complexes: PSP-co-4-PVP x (SnCl2)n, PSP-co-4-PVP x (ZnCl2)n and PSP-co-4-PVP x (Ce(NO3)3)n in several molar ratios under air at 800 degrees C. The as-prepared nanostructured SnO2 exhibits morphologies and particle sizes which are dependent upon the molar ratio of the SnCl2:PSP-co-4-PVP. When a larger weight fraction of the inorganic salt in the precursor mixture is used (1:10 > 1:5 > 1.1) larger crystalline crystals are found for each oxide. For ZnO and CeO2 agglomerates of morphologies from the respective hexagonal and cubic structures were observed with typical sizes of 30-50 nm in both cases for a precursor mixture ratio of 1:1. PMID:25924326

  10. Thermoluminescence of magnesium oxide doped with cerium and lithium obtained by a glycine-based solution combustion method

    International Nuclear Information System (INIS)

    Full text: It is well known that glycine, fulfills two principal purposes: first, complexes with metal cations formed, which increases their solubility and prevents selective precipitation as water is evaporated; and second, it serves as fuel for the combustion reaction, being oxidized by the nitrate ions. The glycine molecule has a carboxylic acid group at one end and an amine group at the other end, both of which can participate in the complexation of metal ions. This zwitterionic character allows effective complexation with metal cations of different ionic size. Novel Mg O:Ce3+, Li+ phosphor was obtained for the very first time by solution combustion synthesis (Scs) in which a redox combustion process between metallic nitrates and glycine at 500 degrees C was accomplished. The powder samples obtained were annealed at 900 degrees C during 2 h in air. X-ray diffraction (XRD) results showed the face-centered cubic (fcc) phase of Mg O as well as the presence of CeO2 for the annealed powder samples. Photoluminescence emission spectra showed the characteristic Ce3+ peak located at 520 nm. The thermoluminescence glow curve obtained after exposure to beta radiation of these samples, displayed three maxima located at ∼ 108 degrees C, ∼ 210 degrees C, and ∼ 310 degrees C. Results from experiments such as dose response and fading showed that annealed Mg O:Ce3+, Li+ powder obtained by Scs is a promising material for radiation dosimetry applications. (Author)

  11. Thermoluminescence of magnesium oxide doped with cerium and lithium obtained by a glycine-based solution combustion method

    Energy Technology Data Exchange (ETDEWEB)

    Escobar O, F. M.; Orante B, V. R.; Cruz V, C. [Universidad de Sonora, Departamento de Investigacion en Polimeros y Materiales, Apdo. Postal 130, 83000 Hermosillo, Sonora (Mexico); Bernal, R., E-mail: flor.escobaroc@gmail.com [Universidad de Sonora, Departamento de Investigacion en Fisica, Apdo. Postal 5-088, 83190 Hermosillo, Sonora (Mexico)

    2015-10-15

    Full text: It is well known that glycine, fulfills two principal purposes: first, complexes with metal cations formed, which increases their solubility and prevents selective precipitation as water is evaporated; and second, it serves as fuel for the combustion reaction, being oxidized by the nitrate ions. The glycine molecule has a carboxylic acid group at one end and an amine group at the other end, both of which can participate in the complexation of metal ions. This zwitterionic character allows effective complexation with metal cations of different ionic size. Novel Mg O:Ce{sup 3+}, Li{sup +} phosphor was obtained for the very first time by solution combustion synthesis (Scs) in which a redox combustion process between metallic nitrates and glycine at 500 degrees C was accomplished. The powder samples obtained were annealed at 900 degrees C during 2 h in air. X-ray diffraction (XRD) results showed the face-centered cubic (fcc) phase of Mg O as well as the presence of CeO{sub 2} for the annealed powder samples. Photoluminescence emission spectra showed the characteristic Ce{sup 3+} peak located at 520 nm. The thermoluminescence glow curve obtained after exposure to beta radiation of these samples, displayed three maxima located at ∼ 108 degrees C, ∼ 210 degrees C, and ∼ 310 degrees C. Results from experiments such as dose response and fading showed that annealed Mg O:Ce{sup 3+}, Li{sup +} powder obtained by Scs is a promising material for radiation dosimetry applications. (Author)

  12. Synthesis of cerium oxide nanoparticles using Gloriosa superba L. leaf extract and their structural, optical and antibacterial properties

    Energy Technology Data Exchange (ETDEWEB)

    Arumugam, Ayyakannu, E-mail: sixmuga@yahoo.com [Department of Nanoscience and Technology, Alagappa University, Karaikudi 630 004, Tamil Nadu (India); Karthikeyan, Chandrasekaran; Haja Hameed, Abdulrahman Syedahamed [PG and Research Department of Physics, Jamal Mohamed College, Tiruchirappalli 620 020, Tamil Nadu (India); Gopinath, Kasi; Gowri, Shanmugam; Karthika, Viswanathan [Department of Nanoscience and Technology, Alagappa University, Karaikudi 630 004, Tamil Nadu (India)

    2015-04-01

    CeO{sub 2} nanoparticles (NPs) were green synthesized using Gloriosa superba L. leaf extract. The synthesized nanoparticles retained the cubic structure, which was confirmed by X-ray diffraction studies. The oxidation states of the elements (C (1s), O (1s) and Ce (3d)) were confirmed by XPS studies. TEM images showed that the NPs possessed spherical shape and particle size of 5 nm. The Ce–O stretching bands were observed at 451 cm{sup −1} and 457 cm{sup −1} from the FT-IR and Raman spectra respectively. The band gap of the CeO{sub 2} NPs was estimated as 3.78 eV from the UV–visible spectrum. From the photoluminescence measurements, the broad emission composed of eight different bands were found. The antibacterial studies performed against a set of bacterial strains showed that Gram positive (G +) bacteria were relatively more susceptible to the NPs than Gram negative (G −) bacteria. The toxicological behavior of CeO{sub 2} NPs was found due to the synthesized NPs with uneven ridges and oxygen defects in CeO{sub 2} NPs. - Highlights: • Phytosynthesis of CeO{sub 2} NPs using Gloriosa superba leaf extract • Single step synthesis • Characterized by XRD, XPS, TEM, FTIR, Raman, UV–vis, PL and TG/DTA analyses • CeO{sub 2} NPs were of spherical shape with an average size of 5 nm. • CeO{sub 2} NPs showed highly potent antibacterial activity.

  13. Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents

    OpenAIRE

    Mirella Gutiérrez-Arzaluz; Luis Noreña-Franco; Saúl Ángel-Cuevas; Violeta Mugica-Álvarez; Miguel Torres-Rodríguez

    2016-01-01

    We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce–Co/Al2O3 membrane, which are employed as catalysts for the catalytic wet oxidation (CWO) reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation ...

  14. Influence of minor additions to Fe-Mn-Al alloys in an oxidizing environment - Role of a cerium oxide modified surface on silicon containing alloys

    OpenAIRE

    Buscail, H.; Sotto, P.; Larpin, J.

    1993-01-01

    Various silicon containing Fe-Mn-Al alloys were studied to estimate the influence of the silicon content on their oxidation behaviour. Silicon has a beneficial effect. Diffusion properties seem to be modified in the alumina scale grown at the scale substrate interface. Then, both scale growth and adherence are strongly affected. One possibility for modifying scale growth properties without changing the strength of the base alloy involves surface additions. The oxidation behaviour of a CeO2 su...

  15. Hydrated cerium(3) vanadates

    International Nuclear Information System (INIS)

    It has been ascertained by the methods of chemical, thermal and X-ray phase analyses, IR spectroscopy that in the system LiVO3-Ce(NO3)3-HNO3-LiOH-H2O in equilibrium conditions the following compounds are precipitated: cerium dodecavanadate Ce2(V12O31)3·3nH2O, where 11.0 5O13)2·nH2O, where 6.5 2V10O28·19H2O; vanadates Ce(VO3)3·4H2O and CeVO4·H2O. Cerium orthovanadate is crystallized in tetragonal crystal system with zircon structure and crystal lattice parameters as follows: a=7.3726(14) and c=6.4939(23) A

  16. Ultrathin, epitaxial cerium dioxide on silicon

    International Nuclear Information System (INIS)

    It is shown that ultrathin, highly ordered, continuous films of cerium dioxide may be prepared on silicon following substrate prepassivation using an atomic layer of chlorine. The as-deposited, few-nanometer-thin Ce2O3 film may very effectively be converted at room temperature to almost fully oxidized CeO2 by simple exposure to air, as demonstrated by hard X-ray photoemission spectroscopy and X-ray diffraction. This post-oxidation process essentially results in a negligible loss in film crystallinity and interface abruptness

  17. Ultrathin, epitaxial cerium dioxide on silicon

    OpenAIRE

    Flege, Jan Ingo; Kaemena, Björn; Höcker, Jan; Bertram, Florian; Wollschläger, Joachim; Schmidt, Thomas; Falta, Jens

    2014-01-01

    It is shown that ultrathin, highly ordered, continuous films of cerium dioxide may be prepared on silicon following substrate prepassivation using an atomic layer of chlorine. The as-deposited, few-nanometer-thin Ce2O3 film may very effectively be converted at room temperature to almost fully oxidized CeO2 by simple exposure to air, as demonstrated by hard X-ray photoemission spectroscopy and X-ray diffraction. This post-oxidation process essentially results in a negligible loss in film cryst...

  18. The iron and cerium oxide influence on the electric conductivity and the corrosion resistance of anodized aluminium; A influencia do ferro e do oxido de cerio sobre a condutividade eletrica e a resistencia a corrosao do aluminio anodizado

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Kellie Provazi de

    2006-07-01

    The influence of different treatments on the aluminum system covered with aluminum oxide is investigated. The aluminum anodization in sulphuric media and in mixed sulphuric and phosphoric media was used to alter the corrosion resistance, thickness, coverage degree and microhardness of the anodic oxide. Iron electrodeposition inside the anodic oxide was used to change its electric conductivity and corrosion resistance. Direct and pulsed current were used for iron electrodeposition and the Fe(SO{sub 4}){sub 2}(NH{sub 4}){sub 2}.6H{sub 2}O electrolyte composition was changed with the addition of boric and ascorbic acids. To the sealing treatment the CeCl{sub 3} composition was varied. The energy dispersive x-ray (EDS), the x-ray fluorescence spectroscopy (FRX) and the morphologic analysis by scanning electronic microscopy (SEM) allowed to verify that, the pulsed current increase the iron content inside the anodic layer and that the use of the additives inhibits the iron oxidation. The chronopotentiometric curves obtained during iron electrodeposition indicated that the boric and ascorbic acids mixture increased the electrodeposition process efficiency. The electrochemical impedance spectroscopy (EIE), the Vickers (Hv) microhardness measurements and morphologic analysis evidenced that the sealing treatment improves the corrosion resistance of the anodic film modified with iron. The electrical impedance (EI) technique allowed to prove the electric conductivity increase of the anodized aluminum with iron electrodeposited even after the cerium low concentration treatment. Iron nanowires were prepared by using the anodic oxide pores as template. (author)

  19. Study of preparation method and oxidization/reduction effect on the performance of nickel-cerium oxide catalysts for aqueous-phase reforming of ethanol

    Science.gov (United States)

    Roy, B.; Leclerc, C. A.

    2015-12-01

    The effect of preparation method and oxidation state of the active metal on the catalytic activity of Ni-Ce-O catalysts was studied for aqueous phase reforming of ethanol. A sol-gel (SG) route and a solution combustion synthesis (SCS) method were used for the preparation of 10 wt% Ni loaded catalysts. The catalytic activity of three groups of catalysts; reduced at 425 °C (HR, metallic Ni), reduced at 1000 °C (FR, metallic Ni), and not reduced (NR, as NiO) were tested at different operating conditions. The difference in the metal particle sizes, governed by the preparation method, affects the catalytic efficiency most, not the reduced or oxidized state of Ni. The SG samples were superior for ethanol conversion and selectivity for H2 and CO2 compared to the SCS samples. The X-ray photoelectron spectroscopy (XPS) analysis of the samples demonstrated that the relative ratio of Ce2O3 to CeO2 increased inside the reactor. While Ni doping increases oxygen mobility in the Ce-O lattice, Ce3+ converts Ni2+ to metallic Ni inside the reactor. This can explain why the reduction stage for Ni-Ce-O system in APR is irrelevant. Higher oxygen mobility through the support helps oxidation of CO to CO2 leading to improved catalytic performance.

  20. Adsorbate-modified growth of ultrathin rare-earth oxide films on silicon and complementary studies of cerium oxide on ruthenium

    International Nuclear Information System (INIS)

    Rare-earth oxides (REOx) are extensively investigated due to their extraordinary physical and chemical properties, which essentially arise from the unfilled 4f electron shell, in order to reveal the nature of these exceptional properties and ultimately to utilize them for multiple technological applications. To maintain the exponential increase in integration density in CMOS technology, which is also known as Moore s law, there is a strong desire for ultrathin, well-ordered, epitaxial REOx layers with a precisely engineered interface, which is essential for reliable, ultrahigh-performance devices. So far this has been considerably impeded by RE-promoted silicon oxidation, leading to amorphous silicon oxide and RE silicon formation. By using complementary synchrotron radiation methods such as X-ray standing waves (XSW), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), structural and spectroscopic information are inferred simultaneously from ultrathin ceria and lanthana films grown on chlorine, silver and gallium passivated silicon(111). In general, it is revealed that the chemical and structural composition of the interface and the crystallinity of ultrathin REOx layers on silicon can be precisely controlled by adsorbate-mediated growth. This might represent a crucial step towards a perfectly engineered interface, eventually allowing for the integration of REOx as high-k gate oxides in microelectronics. In catalysis inverse model catalysts are studied with the aim of getting an in-depth understanding of the basic principles of catalysis. These model systems are employed to study, e. g., the nature of active sites and the reaction pathways in complex catalytic converters. However, a lot remains unknown about the chemical activity and selectivity as a function of the growth mechanism, structure and morphology of these model systems. The powerful spectroscopic photoemission and low-energy electron microscope, which is able to reveal the surface

  1. Elaboration and characterization of thin solid films containing cerium

    Science.gov (United States)

    Hamdi, S.; Guerfi, S.; Siab, R.

    2009-11-01

    Cerium oxide films are widely studied as a promising alternative to Cr(VI) based pre-treatments for the corrosion protection of different metals and alloys. Cathodic electrodeposition of Cerium containing thin films was realised on TA6V substrates from a Ce(NO3)3, 6H2O and mixed water-ethyl alcohol solutions at 0.01 M. Experimental conditions to obtain homogeneous and crack free thin films were determined. The deposited cerium quantity appears proportional to the quantity of electricity used, as indicated by the Faraday law. Subsequent thermal treatment lead to a CeO2 coating, expected to provide an increase of TA6V oxidation resistance at high temperatures. The deposits were characterized by differential scanning calorimetry (DSC), optical and scanning electron microscopies.

  2. An environmentally compliant cerium-based conversion coating for aluminum protection

    Science.gov (United States)

    Lin, Xuan

    Chromate conversion coatings have been extensively used in the aircraft industry for the corrosion protection of aluminum alloys. Unfortunately, hexavalent chromium, which is a primary component in the chromating process, is a confirmed carcinogen. Because of rising remediation and disposal costs caused by increasingly strict regulations, the replacement of the traditional chromate conversion process is becoming a top priority in the metal finishing industry. This research focused on the electrodeposition of cerium-based coatings on 7075-T6 aluminum alloy in an electrolyte containing a cerium salt, an oxidizing agent and an organic solvent. The cerium-rich deposits were characterized by phase composition, oxidation state, coating thickness, surface morphology, deposition mechanism and polarization behavior. Chemical and electrochemical tests were utilized to compare the corrosion resistance between cerium-based coatings and chromate conversion coatings. To characterize and simulate the deposition process, a variety of approaches were utilized to study the oxidation states of cerium in various soluble and precipitated forms as a function of hydrogen peroxide and electrolyte pH. The pH ranges where the oxidation and reduction reactions dominate were determined. Further studies were performed to optimize the corrosion performance of cerium-based coatings and to understand the effects of electrolyte constituents and deposition parameters. The optimum levels for these variables were identified. A patent disclosure on the cerium-based coating process was made to the University of Missouri-Rolla and has now been officially filed with the U.S. Patent Office.

  3. Coulometric microdetermination of organic compounds with manganese(III) and cerium(IV)

    International Nuclear Information System (INIS)

    The oxidation of compounds such as hydroquinon, p-aminophenol, paracetamol and phenacetin was performed using cerium(IV) and manganese(III) coulometrically electrogenerated. Quantitative results obtained are excellent even at the microscale level. (author)

  4. The PL "violet shift" of cerium dioxide on silicon

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    CeO2 thin film was fabricated by dual ion beam epitaxial technique. The phenomenon of PL violet shift at room temperature was observed, and the distance of shift was about 65 nm. After the analysis of crystal structure and valence in the compound were carried out by XRD and XPS technique, it was concluded that the PL shift was related with valence of cerium ion in the oxides. When the valence of cerium ion varied from tetravalence to trivalence, the PL peak position would move from blue region to violet region and the phenomenon of "violet shift" was observed.

  5. Rapid formation of a superhydrophobic surface on a magnesium alloy coated with a cerium oxide film by a simple immersion process at room temperature and its chemical stability.

    Science.gov (United States)

    Ishizaki, Takahiro; Saito, Naobumi

    2010-06-15

    We have developed a facile, simple, time-saving method of creating a superhydrophobic surface on a magnesium alloy by a simple immersion process at room temperature. First, a crystalline CeO(2) film was vertically formed on the magnesium alloy by immersion in a cerium nitrate aqueous solution for 20 min. The density of the crystals vertically with respect to the magnesium alloy increased with increasing immersion time. Next, the film were covered with fluoroalkylsilane (FAS: CF(3)(CF(2))(7)CH(2)CH(2)Si(OCH(3))(3)) molecules within 30 min by immersion in a toluene solution containing FAS and tetrakis(trimethylsiloxy)titanium (TTST: (CH(3))(3)SiO)(4)Ti). TTST was used as a catalyst to promote the hydrolysis and/or polymerization of FAS molecules. The FAS-coated CeO(2) film had a static contact angle of more than 150 degrees, that is, a superhydrophobic property. The shortest processing time for the fabrication of the superhydrophobic surface was 40 min. The contact angle hysteresis decreased with an increase in the immersion time in the cerium nitrate aqueous solution. The chemical stability of the superhydrophobic surface on magnesium alloy AZ31 was investigated. The average static water contact angles of the superhydrophobic surfaces after immersion in the solutions at pH 4, 7, and 10 for 24 h were found to be 139.7 +/- 2, 140.0 +/- 2, and 145.7 +/- 2 degrees, respectively. In addition, the chemical stability of the superhydrophobic surface in the solutions at pH ranging from 1 to 14 was also examined. The superhydrophobic surfaces had static contact angles of more than 142 degrees in the solutions at pH ranging from 1 to 14, showing that our superhydrophobic surface had a high chemical stability. Moreover, the corrosion resistance of the superhydrophobic surface on the magnesium alloy was investigated using electrochemical measurements. PMID:20377219

  6. Cerium as a Surrogate in the Plutonium Immobilized Form

    International Nuclear Information System (INIS)

    The Department of Energy (DOE) plans to immobilize a portion of the excess weapons useable plutonium in a ceramic form for final geologic disposal. The proposed immobilization form is a titanate based ceramic consisting primarily of a pyrochlore phase with lesser amounts of brannerite, rutile, zirconolite, vitreous phases and/or other minor phases depending on the impurities present in the feed. The ceramic formulation is cold-pressed and then densified via a reactive sintering process. Cerium has been used as a surrogate for plutonium to facilitate formulation development and process testing. The use of cerium vs. plutonium results in differences in behavior during sintering of the ceramic form. The phase development progression and final phase assemblage is different when cerium is substituted for the actinides in the form. However, the physical behavior of cerium oxide powder and the formation of a pyrochlore-rich ceramic of similar density to the actinide-bearing material make cerium an adequate surrogate for formulation and process development studies

  7. Potential for recovery of cerium contained in automotive catalytic converters

    Science.gov (United States)

    Bleiwas, Donald I.

    2013-01-01

    Catalytic converters (CATCONs) are required by Federal law to be installed in nearly all gasoline- and diesel-fueled onroad vehicles used in the United States. About 85 percent of the light-duty vehicles and trucks manufactured worldwide are equipped with CATCONs. Portions of the CATCONs (called monoliths) are recycled for their platinum-group metal (PGM) content and for the value of the stainless steel they contain. The cerium contained in the monoliths, however, is disposed of along with the slag produced from the recycling process. Although there is some smelter capacity in the United States to treat the monoliths in order to recover the PGMs, a great percentage of monoliths is exported to Europe and South Africa for recycling, and a lesser amount is exported to Japan. There is presently no commercial-scale capacity in place domestically to recover cerium from the monoliths. Recycling of cerium or cerium compounds from the monoliths could help ensure against possible global supply shortages by increasing the amount that is available in the supply chain as well as the number and geographic distribution of the suppliers. It could also reduce the amount of material that goes into landfills. Also, the additional supply could lower the price of the commodity. This report analyzes how much cerium oxide is contained in CATCONs and how much could be recovered from used CATCONs.

  8. X-ray absorption study of cerium in the passive film on aluminum

    International Nuclear Information System (INIS)

    The corrosion-resistance of aluminum-based alloys and metal-matrix composites can be increased by treatment with cerium compounds. Immersion in a 1000 ppm solution of Ce Cl3 for periods of several days has been shown to increase the pitting potential and reduce the corrosion rate. Such treatment is being considered as an alternative to the use of chromate conversion coatings. The protective action of cerium is considered to be due to the formation of a film containing cerium oxide/hydroxide with cerium in the oxidation states 3 and 4. This occurs by precipitation of cerium compounds onto cathodic sites due to the increase of pH associated with oxygen reduction. Cerium compounds are considerably less soluble than aluminum compounds at high pH. It is proposed that the cerium oxide/hydroxide creates a barrier to the reduction of oxygen stifling cathodic reaction with a corresponding reduction in corrosion rate and open circuit potential. Glancing angle x-ray techniques are well-suited to studying the composition and structure of surface layers on materials. X-rays incident at very small angles (of the order of milliradians) below the critical angle do not penetrate beyond the surface layers of the material. With the extremely high brightness beams of x-rays provided by synchrotron sources the authors detect and characterize the chemical state of elements present in low concentrations in the surface of materials

  9. Cerium doped red mud catalytic ozonation for bezafibrate degradation in wastewater: Efficiency, intermediates, and toxicity.

    Science.gov (United States)

    Xu, Bingbing; Qi, Fei; Sun, Dezhi; Chen, Zhonglin; Robert, Didier

    2016-03-01

    In this study, the performance of bezafibrate (BZF) degradation and detoxification in the aqueous phase using cerium-modified red mud (RM) catalysts prepared using different cerium sources and synthesis methods were evaluated. Experimental results showed that the surface cerium modification was responsible for the development of the catalytic activity of RM and this was influenced by the cerium source and the synthesis method. Catalyst prepared from cerium (IV) by precipitation was found to show the best catalytic activity in BZF degradation and detoxification. Reactive oxygen species including peroxides, hydroxyl radicals, and super oxide ions were identified in all reactions and we proposed the corresponding catalytic reaction mechanism for each catalyst that prepared from different cerium source and method. This was supported by the intermediates profiles that were generated upon BZF degradation. The surface and the structural properties of cerium-modified RM were characterized in detail by several analytical methods. Two interesting findings were made: (1) the surface texture (specific surface area and mesoporous volume) influenced the catalytic reaction pathway; and (2) Ce(III) species and oxygen vacancies were generated on the surface of the catalyst after cerium modification. This plays an important role in the development of the catalytic activity. PMID:26706928

  10. The study on preparation of high dispersion and pure cerium dioxide for producing automotive exhaust catalysts

    International Nuclear Information System (INIS)

    The multi-stage counter-current solvent extraction process using TBP as the solvent has been carried out for purifying cerium and the ammonium carbonate precipitation method has been used to produce the cerium oxide of high dispersion and pure. The flow sheet of extraction system includes 3 extraction stages with O/A = 0.7,2 stripping stages and 4 scrubbing stages with O/A = 5. The condition for ammonium carbonate precipitation, drying and calcination have been investigated and a procedure that seem to be practically suitable to prepare cerium dioxide powder with great specific surface area for producing automotive exhaust catalyst has been proposed. (LMT)

  11. Purification of cerium, neodymium and gadolinium for low background experiments

    Directory of Open Access Journals (Sweden)

    Boiko R.S.

    2014-01-01

    Full Text Available Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search, 136Ce (2β+ candidate with one of the highest Q2β. The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

  12. Purification of cerium, neodymium and gadolinium for low background experiments

    Science.gov (United States)

    Boiko, R. S.; Barabash, A. S.; Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F. A.; Incicchitti, A.; Laubenstein, M.; Mokina, V. M.; Nisi, S.; Poda, D. V.; Polischuk, O. G.; Tretyak, V. I.

    2014-01-01

    Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search), 136Ce (2β+ candidate with one of the highest Q2β). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low-background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides) was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

  13. Titrimetric and Spectrophotometric Assay of Ganciclovir in Pharmaceuticals Using Cerium(IV) Sulphate as the Oxidimetric Agent

    OpenAIRE

    Pavagada J. Ramesh; Kanakapura Basavaiah; Cijo M. Xavier; Prashanth, Kudige N.; Raghu, Madihalli S.; Kanakapura B. Vinay

    2012-01-01

    Titrimetric and spectrophotometric assay of ganciclovir (GNC) is described using cerium(IV) sulphate as the oxidimetric reagent. The methods are based on the oxidation of GNC with a measured excess of cerium(IV) sulphate in acid medium followed by determination of the unreacted oxidant by two different reaction schemes. In titrimetry, the unreacted oxidant was determined by back titration with ferrous ammonium sulphate (FAS) in sulphuric acid medium, and spectrophotometry involves the reactio...

  14. Preparation of cerium halide solvate complexes

    Science.gov (United States)

    Vasudevan, Kalyan V; Smith, Nickolaus A; Gordon, John C; McKigney, Edward A; Muenchaussen, Ross E

    2013-08-06

    Crystals of a solvated cerium(III) halide solvate complex resulted from a process of forming a paste of a cerium(III) halide in an ionic liquid, adding a solvent to the paste, removing any undissolved solid, and then cooling the liquid phase. Diffusing a solvent vapor into the liquid phase also resulted in crystals of a solvated cerium(III) halide complex.

  15. High-permitivity cerium oxide prepared by molecular beam deposition as gate dielectric and passivation layer and applied to AlGaN/GaN power high electron mobility transistor devices

    Science.gov (United States)

    Chiu, Yu Sheng; Liao, Jen Ting; Lin, Yueh Chin; Chien Liu, Shin; Lin, Tai Ming; Iwai, Hiroshi; Kakushima, Kuniyuki; Chang, Edward Yi

    2016-05-01

    High-κ cerium oxide (CeO2) was applied to AlGaN/GaN high-electron-mobility transistors (HEMTs) as a gate insulator and a passivation layer by molecular beam deposition (MBD) for high-power applications. From capacitance–voltage (C–V) measurement results, the dielectric constant of the CeO2 film was 25.2. The C–V curves showed clear accumulation and depletion behaviors with a small hysteresis (20 mV). Moreover, the interface trap density (D it) was calculated to be 5.5 × 1011 eV‑1 cm‑2 at 150 °C. A CeO2 MOS-HEMT was fabricated and demonstrated a low subthreshold swing (SS) of 87 mV/decade, a high ON/OFF drain current ratio (I ON/I OFF) of 1.14 × 109, and a low gate leakage current density (J leakage) of 2.85 × 10‑9 A cm‑2 with an improved dynamic ON-resistance (R ON), which is about one order of magnitude lower than that of a conventional HEMT.

  16. Silica-based cerium (III) chloride nanoparticles prevent the fructose-induced glycation of α-crystallin and H₂O₂-induced oxidative stress in human lens epithelial cells.

    Science.gov (United States)

    Yang, Jin; Cai, Lei; Zhang, Sen; Zhu, Xiangjia; Zhou, Peng; Lu, Yi

    2014-03-01

    This study aimed to investigate whether silica-cerium (III) chloride (CeCl3) nanoparticles could inhibit the formation of advanced glycation end-products (AGEs) and reduce oxidative stress. Silica-CeCl3 nanoparticles were synthesised by adsorption and embedment with micro-silica materials, forming uniform nanoparticles with a diameter of approximately 130 nm. Chaperone activity assays and AGEs formation assays, and intracellular reactive assays were adopted in this study to evaluate CeCl3 nanoparticles effect. UV-visible spectrometry showed that silica-CeCl3 nanoparticles at low concentrations rapidly formed tentatively stable conjugations with α-crystallin, greatly enhancing the chaperone activity of α-crystallin. Moreover, silica-CeCl3 nanoparticles markedly inhibited the fructose-induced glycation of α-crystallin, showing an advantage over the control drugs aminoguanidine and carnosine. Silica-CeCl3 nanoparticles also reduced intracellular reactive oxygen species production and restored glutathione levels in H2O2-treated human lens epithelial cells. These findings suggest that silica-CeCl3 may be used as a novel agent for the prevention of cataractogenesis. PMID:23828754

  17. Extraction of tetravalent berkelium and cerium by aliquate-336-S-NO3 quaternary ammonium salt

    International Nuclear Information System (INIS)

    Extraction of tetravalent berkelium and cerium by aliquate-336-S-NO3 quaternary ammonium salt from nitric acid solutions is investigated. The effect of concentrations of nitric acid and extracting agent, nature of an oxidant (potassium bromate, potassium bichromate, mixture of AgNO3 and (NH4)2S2O8) and solvent on the distribution coefficient of berkelium(4) and cerium(4) is studied. It is established that solutions of aliquate-336-S-NO3 in carbon tetrachloride and dichloroethane extract quantitatively tetravalent berkelium from 10-12 M nitric acid solutions and cerium - from 1-10 M nitric acid solutions containing potassium bichromate as an oxidant. It is shown that the value of distribution coefficient for berkelium and cerium depends on the nature of an oxidant and extracting agent concentration. It is established that in the case of extraction by quaternary ammonium salt with one berkelium(4) mole four aliquate-336-SNO3 moles are associated and 1.5-1.6 mole of extracting agent are associated with one cerium(4) mole. It permits to make a conclusion that stoichiometry of extraction reactions by quaternary ammonium salt is not the same for tetravalent berkelium and cerium. It is shown that trivalent transplutonium and rare earth elements are not practically extracted by aliquate-336-S-NO3 from nitric acid solutions

  18. The studies of nanoparticles formed in silicate glasses doped by cerium and titanium oxides by means of small angle neutron scattering

    International Nuclear Information System (INIS)

    The structure aspect of Ti-Ce-O nanoparticles, which is forming in silicate glasses doped by TiO2 and CeO2 oxides have been studied by means of a small angle neutron scattering. It was found, the complex oxide nanoparticles forms in these glasses in sizes range 30-38 nm and its average sizes depends on initial oxides concentration ratio. The correlation between nanoparticles structure features and silica glasses optical properties are discussed.

  19. Recovery of Cerium Dioxide from Spent Glass-Polishing Slurry and Its Utilization as a Reactive Sorbent for Fast Degradation of Toxic Organophosphates

    OpenAIRE

    Pavel Janoš; Pavel Kuráň; Jakub Ederer; Martin Šťastný; Luboš Vrtoch; Martin Pšenička; Jiří Henych; Karel Mazanec; Miroslav Skoumal

    2015-01-01

    The recovery of cerium (and possibly other rare earth elements) from the spent glass-polishing slurries is rather difficult because of a high resistance of polishing-grade cerium oxide toward common digestion agents. It was shown that cerium may be extracted from the spent polishing slurries by leaching with strong mineral acids in the presence of reducing agents; the solution may be used directly for the preparation of a ceria-based reactive sorbent. A mixture of concentrated nitric acid and...

  20. Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents

    Directory of Open Access Journals (Sweden)

    Mirella Gutiérrez-Arzaluz

    2016-05-01

    Full Text Available We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce–Co/Al2O3 membrane, which are employed as catalysts for the catalytic wet oxidation (CWO reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce–Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns.

  1. Catalysts with Cerium in a Membrane Reactor for the Removal of Formaldehyde Pollutant from Water Effluents.

    Science.gov (United States)

    Gutiérrez-Arzaluz, Mirella; Noreña-Franco, Luis; Ángel-Cuevas, Saúl; Mugica-Álvarez, Violeta; Torres-Rodríguez, Miguel

    2016-01-01

    We report the synthesis of cerium oxide, cobalt oxide, mixed cerium, and cobalt oxides and a Ce-Co/Al₂O₃ membrane, which are employed as catalysts for the catalytic wet oxidation (CWO) reaction process and the removal of formaldehyde from industrial effluents. Formaldehyde is present in numerous waste streams from the chemical industry in a concentration low enough to make its recovery not economically justified but high enough to create an environmental hazard. Common biological degradation methods do not work for formaldehyde, a highly toxic but refractory, low biodegradability substance. The CWO reaction is a recent, promising alternative that also permits much lower temperature and pressure conditions than other oxidation processes, resulting in economic benefits. The CWO reaction employing Ce- and Co-containing catalysts was carried out inside a slurry batch reactor and a membrane reactor. Experimental results are reported. Next, a mixed Ce-Co oxide film was supported on an γ-alumina membrane used in a catalytic membrane reactor to compare formaldehyde removal between both types of systems. Catalytic materials with cerium and with a relatively large amount of cerium favored the transformation of formaldehyde. Cerium was present as cerianite in the catalytic materials, as indicated by X-ray diffraction patterns. PMID:27231888

  2. Cerium, manganese and cerium/manganese ceramic monolithic catalysts. Study of VOCs and PM removal

    Institute of Scientific and Technical Information of China (English)

    COLMAN-LERNER Esteban; PELUSO Miguel Andrs; SAMBETH Jorge; THOMAS Horacio

    2016-01-01

    Ceramic supported cerium, manganese and cerium-manganese catalysts were prepared by direct impregnation of aqueous precursor, and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller method (BET), temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) acidity measurements and electrical conductivity. The catalytic activity was evaluated for volatile organic compounds (VOC) (ethanol, methyl ethyl ketone and toluene) oxidation. Additionally, catalysts were tested in particulate matter (PM) combustion. The characterization results indicated that Ce was in the form of Ce4+ and Ce3+, and Mn existed in the form of Mn4+and Mn3+on the surface of the Mn/AC sample and in the form of Mn4+ in the Ce/Mn/AC monolith. VOC oxidation results revealed that the Ce/Mn/AC sample showed an excellent performance compared with ceramic supported CeO2 (Ce/AC) and MnOx (Mn/AC) samples. The PM combustion was also higher on Ce/Mn/AC monoliths. The enhanced catalytic activity was mainly attributed to the Ce and Mn interaction which enhanced the acidity, conductiv-ity and the reducibility of the oxides.

  3. Valence instabilities in cerium intermetallics

    International Nuclear Information System (INIS)

    The primary purpose of this investigation was to study the magnetic behaviour of cerium in intermetallic compounds, that show an IV behaviour, e.g. CeSn3. In the progress of the investigations, it became of interest to study the effect of changes in the lattice of the IV compound by substituting La or Y for Ce, thus constituting the Cesub(1-x)Lasub(x)Sn3 and Cesub(1-x)Ysub(x)Sn3 quasibinary systems. A second purpose was to examine the possibility of introducing instabilities in the valency of a trivalent intermetallic cerium compound: CeIn3, also by La and Y-substitutions in the lattice. Measurements on the resulting Cesub(1-x)Lasub(x)In3 and Cesub(1-x)Ysub(x)In3 quasibinaries are described. A third purpose was to study the (gradual) transition from a trivalent cerium compound into an IV cerium compound. This was done by examining the magnetic properties of the CeInsub(x)Snsub(3-x) and CePbsub(x)Snsub(3-x) systems. Finally a new possibility was investigated: that of the occurrence of IV behaviour in CeSi2, CeSi, and in CeGa2. (Auth.)

  4. Reactions between cerium(IV) and methyl-6-x-derivatives of aniline in perchloric acid solutions

    International Nuclear Information System (INIS)

    The oxidation of 2,6-dimethyl-, 2-isopropyl-6-methyl, 2-chloro-6-methyl-and 2-methyl-6-nitro aniline with cerium(IV) in perchloric acid solutions has been examined. It has been found that the concentration of hydrogen ions and the basicity of nitrogen atom in the amine group decide about the resultant intermediate products. Some of these products can be practically prepared using cerium(IV) as an oxidizing agent. (author). 16 refs, 1 tab

  5. Cerium as a surrogate in the plutonium immobilization waste form

    Science.gov (United States)

    Marra, James Christopher

    In the aftermath of the Cold War, approximately 50 tonnes (MT) of weapons useable plutonium (Pu) has been identified as excess. The U.S. Department of Energy (DOE) has decided that at least a portion of this material will be immobilized in a titanate-based ceramic for final disposal in a geologic repository. The baseline formulation was designed to produce a ceramic consisting primarily of a highly substituted pyrochlore with minor amounts of brannerite and hafnia-substituted rutile. Since development studies with actual actinide materials is difficult, surrogates have been used to facilitate testing. Cerium has routinely been used as an actinide surrogate in actinide chemistry and processing studies. Although cerium appeared as an adequate physical surrogate for powder handling and general processing studies, cerium was found to act significantly different from a chemical perspective in the Pu ceramic form. The reduction of cerium at elevated temperatures caused different reaction paths toward densification of the respective forms resulting in different phase assemblages and microstructural features. Single-phase fabrication studies and cerium oxidation state analyses were performed to further quantify these behavioral differences. These studies indicated that the major phases in the final phase assemblages contained point defects likely leading to their stability. Additionally, thermochemical arguments predicted that the predominant pyrochlore phase in the ceramic was metastable. The apparent metastabilty associated with primary phase in the Pu ceramic form indicated that additional studies must be performed to evaluate the thermodynamic properties of these compounds. Moreover, the metastability of this predominant phase must be considered in assessment of long-term behavior (e.g. radiation stability) of this ceramic.

  6. Oxidation of alginate and pectate biopolymers by cerium(IV) in perchloric and sulfuric acid solutions: A comparative kinetic and mechanistic study.

    Science.gov (United States)

    Fawzy, Ahmed

    2016-03-15

    The kinetics of oxidation of alginate (Alg) and pectate (Pec) carbohydrate biopolymers was studied by spectrophotometry in aqueous perchloric and sulfuric acid solutions at fixed ionic strengths and temperature. In both acids, the reactions showed a first order dependence on [Ce(IV)], whereas the orders with respect to biopolymer concentrations are less than unity. In perchloric acid, the reactions exhibited less than unit orders with respect to [H(+)] whereas those proceeded in sulfuric acid showed negative fractional-first order dependences on [H(+)]. The effect of ionic strength and dielectric constant was studied. Probable mechanistic schemes for oxidation reactions were proposed. In both acids, the final oxidation products were characterized as mono-keto derivatives of both biopolymers. The activation parameters with respect to the slow step of the mechanisms were computed and discussed. The rate laws were derived and the reaction constants involved in the different steps of the mechanisms were calculated. PMID:26794772

  7. Analysis of single and binary phases in cerium doped sodium bismuth titanate -inorganic materials Na0.5Bi(0.5-x)CexTiO3

    International Nuclear Information System (INIS)

    The pure and cerium doped sodium bismuth titanate (NBT) inorganic powders were synthesized by solid-state reaction method. The presence of rhombohedral phase was observed in cerium doped NBT compounds. When x= 0.05 of cerium doped NBT is heat treated at 1200 degree centigrade, the compound forms single perovskite phase. The samples of x = 0.10 and 0.15 were heat treated up to 1350 degree centigrade, the binary phases with cerium and bismuth oxides were observed. The X-ray diffraction, Fourier transform infrared spectroscopy, reflectance spectra, differential thermal analysis and thermogravimetric analysis were used to analyze the various properties of samples. Moreover, the effects of cerium doping and calcining temperature on NBT samples were investigated. In this work, we present our recent results on the synthesis and characterization of cerium doped sodium bismuth titanate materials. (Author)

  8. Radiative lifetimes of neutral cerium

    International Nuclear Information System (INIS)

    Radiative lifetimes, accurate to ±5%, have been measured for 153 levels of neutral cerium using time-resolved laser-induced fluorescence (TRLIF) on a slow beam of cerium atoms. Of the 153 levels studied, 150 are even parity and 3 are odd parity. The levels range in energy from 16 869 to 28 557 cm-1. This set of Ce I lifetimes is much more extensive than others published to date, and will provide the absolute calibration for a very large set of measured Ce I transition probabilities. Accurate transition probabilities for lines in the visible and ultraviolet are needed both in astrophysics, for the determination of elemental abundances, and by the lighting community, for research and development of metal halide high-intensity discharge lamps.

  9. Radiative lifetimes of neutral cerium

    Energy Technology Data Exchange (ETDEWEB)

    Den Hartog, E A; Buettner, K P; Lawler, J E [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)], E-mail: eadenhar@wisc.edu, E-mail: Kevin.Buettner@usma.edu, E-mail: jelawler@wisc.edu

    2009-04-28

    Radiative lifetimes, accurate to {+-}5%, have been measured for 153 levels of neutral cerium using time-resolved laser-induced fluorescence (TRLIF) on a slow beam of cerium atoms. Of the 153 levels studied, 150 are even parity and 3 are odd parity. The levels range in energy from 16 869 to 28 557 cm{sup -1}. This set of Ce I lifetimes is much more extensive than others published to date, and will provide the absolute calibration for a very large set of measured Ce I transition probabilities. Accurate transition probabilities for lines in the visible and ultraviolet are needed both in astrophysics, for the determination of elemental abundances, and by the lighting community, for research and development of metal halide high-intensity discharge lamps.

  10. Catalytic conversion of carbon dioxide into dimethyl carbonate using reduced copper-cerium oxide catalysts as low as 353 K and 1.3 MPa and the reaction mechanism

    Directory of Open Access Journals (Sweden)

    Seiki eWada

    2013-06-01

    Full Text Available Synthesis of dimethyl carbonate (DMC from CO2 and methanol under milder reaction conditions was performed using reduced cerium oxide catalysts and reduced copper-promoted Ce oxide catalysts. Although the conversion of methanol was low (0.005–0.11% for 2 h of reaction, DMC was synthesized as low as 353 K and at total pressure of as low as 1.3 MPa using reduced Cu–CeO2 catalyst (0.5 wt% of Cu. The apparent activation energy was 120 kJ mol–1 and the DMC synthesis rates were proportional to the partial pressure of CO2. An optimum amount of Cu addition to CeO2 was 0.1 wt% for DMC synthesis under the conditions at 393 K and total pressure of 1.3 MPa for 2 h (conversion of methanol: 0.15% due to the compromise of two effects of Cu: the activation of H2 during reduction prior to the kinetic tests and the block (cover of the surface active site. The reduction effects in H2 were monitored through the reduction of Ce4+ sites to Ce3+ based on the shoulder peak intensity at 5727 eV in the Ce L3-edge X-ray absorption near-edge structure (XANES. The Ce3+ content was 10% for reduced CeO2 catalyst whereas it increased to 15% for reduced Cu–CeO2 catalyst (0.5wt% of Cu. Moreover, the content of reduced Ce3+ sites (10% associated with the surface O vacancy (defect sites decreased to 5% under CO2 at 290 K for reduced Cu–CeO2 catalyst (0.1wt% of Cu. The adsorption step of CO2 on the defect sites might be the key step in DMC synthesis and thus the DMC synthesis rate dependence on the partial pressure of CO2 was proportional. Subsequent H atom subtraction steps from methanol at the neighboring surface Lewis base sites should combine two methoxy species to the adsorbed CO2 to form DMC, water, and restore the surface O vacancy.

  11. Catalytic conversion of carbon dioxide into dimethyl carbonate using reduced copper-cerium oxide catalysts as low as 353 K and 1.3 MPa and the reaction mechanism

    Science.gov (United States)

    Wada, Seiki; Oka, Kazuki; Watanabe, Kentaro; Izumi, Yasuo

    2013-06-01

    Synthesis of dimethyl carbonate (DMC) from CO2 and methanol under milder reaction conditions was performed using reduced cerium oxide catalysts and reduced copper-promoted Ce oxide catalysts. Although the conversion of methanol was low (0.005-0.11%) for 2 h of reaction, DMC was synthesized as low as 353 K and at total pressure of as low as 1.3 MPa using reduced Cu-CeO2 catalyst (0.5 wt% of Cu). The apparent activation energy was 120 kJ mol-1 and the DMC synthesis rates were proportional to the partial pressure of CO2. An optimum amount of Cu addition to CeO2 was 0.1 wt% for DMC synthesis under the conditions at 393 K and total pressure of 1.3 MPa for 2 h (conversion of methanol: 0.15%) due to the compromise of two effects of Cu: the activation of H2 during reduction prior to the kinetic tests and the block (cover) of the surface active site. The reduction effects in H2 were monitored through the reduction of Ce4+ sites to Ce3+ based on the shoulder peak intensity at 5727 eV in the Ce L3-edge X-ray absorption near-edge structure (XANES). The Ce3+ content was 10% for reduced CeO2 catalyst whereas it increased to 15% for reduced Cu-CeO2 catalyst (0.5wt% of Cu). Moreover, the content of reduced Ce3+ sites (10%) associated with the surface O vacancy (defect sites) decreased to 5% under CO2 at 290 K for reduced Cu-CeO2 catalyst (0.1wt% of Cu). The adsorption step of CO2 on the defect sites might be the key step in DMC synthesis and thus the DMC synthesis rate dependence on the partial pressure of CO2 was proportional. Subsequent H atom subtraction steps from methanol at the neighboring surface Lewis base sites should combine two methoxy species to the adsorbed CO2 to form DMC, water, and restore the surface O vacancy.

  12. Adsorption of Fluoride Ion by Inorganic Cerium Based Adsorbent

    Institute of Scientific and Technical Information of China (English)

    Jiao Zhongzhi(焦中志); Chen Zhonglin; Yang Min; Zhang Yu; Li Guibai

    2004-01-01

    Excess of fluoride in drinking water is harmful to human health, the concentration of F- ions must be maintained in the range of 0.5 to 1.5 mg/L. An inorganic cerium based adsorbent (CTA) is developed on the basis of research of adsorption of fluoride on cerium oxide hydrate. Some adsorption of fluoride by CTA adsorbent experiments were carried out, and results showed that CTA adsorbent has a quick adsorption speed and a large adsorption capacity. Adsorption follows Freundlich isotherm, and low pH value helps fluoride removal. Some physical-chemical characteristics of CTA adsorbent were experimented, fluoride removal mechanism was explored, and results showed that hydroxyl group of CTA adsorbent played an important role in the fluoride removal.

  13. Monomers, Dimers, and Helices: Complexities of Cerium and Plutonium Phenanthrolinecarboxylates.

    Science.gov (United States)

    Cary, Samantha K; Ferrier, Maryline G; Baumbach, Ryan E; Silver, Mark A; Lezama Pacheco, Juan; Kozimor, Stosh A; La Pierre, Henry S; Stein, Benjamin W; Arico, Alexandra A; Gray, Danielle L; Albrecht-Schmitt, Thomas E

    2016-05-01

    The reaction of Ce(III) or Pu(III) with 1,10-phenanthroline-2,9-dicarboxylic acid (PDAH2) results in the formation of new f-element coordination complexes. In the case of cerium, Ce(PDA)(H2O)2Cl·H2O (1) or [Ce(PDAH)(PDA)]2[Ce(PDAH)(PDA)] (2) was isolated depending on the Ce/ligand ratio in the reaction. The structure of 2 is composed of two distinct substructures that are constructed from the same monomer. This monomer is composed of a Ce(III) cation bound by one PDA(2-) dianionic ligand and one PDAH(-) monoanionic ligand, both of which are tetradentate. Bridging by the carboxylate moieties leads to either [Ce(PDAH)(PDA)]2 dimers or [Ce(PDAH)(PDA)]1∞ helical chains. For plutonium, Pu(PDA)2 (3) was the only product isolated regardless of the Pu/ligand ratio employed in the reaction. During the reaction of plutonium with PDAH2, Pu(III) is oxidized to Pu(IV), generating 3. This assignment is consistent with structural metrics and the optical absorption spectrum. Ambiguity in the assignment of the oxidation state of cerium in 1 and 2 from UV-vis-near-IR spectra invoked the use of Ce L3,2-edge X-ray absorption near-edge spectroscopy, magnetic susceptibility, and heat capacity measurements. These experiments support the assignment of Ce(III) in both compounds. The bond distances and coordination numbers are also consistent with these assignments. 3 contains 8-coordinate Pu(IV), whereas the cerium centers in 1 and 2 are 9- and/or 10-coordinate, which correlates with the increased size of Ce(III) versus Pu(IV). Taken together, these data provide an example of a system where the differences in the redox behavior between these f elements creates more complex chemistry with cerium than with plutonium. PMID:27070401

  14. Oxidative mobilization of cerium and uranium and enhanced release of "immobile" high field strength elements from igneous rocks in the presence of the biogenic siderophore desferrioxamine B

    Science.gov (United States)

    Kraemer, Dennis; Kopf, Sebastian; Bau, Michael

    2015-09-01

    Polyvalent trace elements such as the high field strength elements (HFSE) are commonly considered rather immobile during low-temperature water-rock interaction. Hence, they have become diagnostic tools that are widely applied in geochemical studies. We present results of batch leaching experiments focused on the mobilization of certain HFSE (Y, Zr, Hf, Th, U and rare earth elements) from mafic, intermediate and felsic igneous rocks in the presence and absence, respectively, of the siderophore desferrioxamine B (DFOB). Our data show that DFOB strongly enhances the mobility of these trace elements during low-temperature water-rock interaction. The presence of DFOB produces two distinct features in the Rare Earths and Yttrium (REY) patterns of leaching solutions, regardless of the mineralogical and chemical composition or the texture of the rock type studied. Bulk rock-normalized REY patterns of leaching solutions with DFOB show (i) a very distinct positive Ce anomaly and (ii) depletion of La and other light REY relative to the middle REY, with a concave downward pattern between La and Sm. These features are not observed in experiments with hydrochloric acid, acetic acid or deionized water. In DFOB-bearing leaching solutions Ce and U are decoupled from and selectively enriched relative to light REY and Th, respectively, due to oxidation to Ce(IV) and U(VI). Oxidation of Ce3+ and U4+ is promoted by the significantly higher stability of the Ce(IV) and U(VI) DFOB complexes as compared to the Ce(III) and U(IV) DFOB complexes. This is similar to the relationship between the Ce(IV)- and Ce(III)-pentacarbonate complexes that cause positive Ce anomalies in alkaline lakes. However, while formation of Ce(IV) carbonate complexes is confined to alkaline environments, Ce(IV) DFOB complexes may produce positive Ce anomalies even in mildly acidic and near-neutral natural waters. Siderophore-promoted dissolution processes also significantly enhance mobility of other 'immobile' HFSE

  15. Cerium and niobium doped SrCoO3-δ as a potential cathode for intermediate temperature solid oxide fuel cells

    Science.gov (United States)

    Huang, Shouguo; Feng, Shuangjiu; Lu, Qiliang; Li, Yide; Wang, Hong; Wang, Chunchang

    2014-04-01

    Sr0.9Ce0.1Co0.9Nb0.1O3-δ (SCCN) has been synthesized using solid state reaction, and investigated as a new cathode material for intermediate temperature solid oxide fuel cells (ITSOFCs). SCCN material exhibits sufficiently high electronic conductivity and excellent chemical compatibility with SDC electrolyte. Highly charged Ce4+ and Nb5+ successfully stabilize the perovskite structure to avoid order-disorder phase transition. The electrical conductivity reaches a high value of 516 S cm-1 at 300 °C in air. The area specific resistances of the SCCN-50 wt.% Ce0.8Sm0.2O1.9 (SDC) cathode are as low as 0.027, 0.049, and 0.094 Ω cm2 at 700, 650, and 600 °C, respectively, with the corresponding peak power densities of 1074, 905, and 589 mW cm-2. A relatively low thermal expansion coefficient of SCCN-SDC is 14.3 × 10-6 K-1 in air. All these results imply that SCCN holds tremendous promise as a cathode material for ITSOFCs.

  16. Electro-deposition of cerium thin film compound, elaboration and characterisation

    International Nuclear Information System (INIS)

    Cerium oxide films are widely studied as a promising alternative to the toxic hexavalent Chromium Cr(VI) based pre-treatments for the corrosion protection of different metals and alloys. Cathodic electro-deposition of Cerium compound thin films was realised on Ti alloy (TA6V) substrates from a Ce(NO3)3, 6H2O in water-ethyl alcohol solutions at 0.01 M. Experimental conditions to obtain homogeneous and crack free thin films were determined. The deposited cerium quantity, as expected, is proportional to the used electric charge, following the Faraday law. Subsequent thermal treatment led to a CeO2 coating, which is expected to increase the TA6V oxidation resistance at high temperatures. The deposits were characterized by Differential Scanning Calorimetry (DSC), optical and scanning electron microscopies.(author)

  17. Catalytic spectrophotometric determination of cerium by ion exchange separation coupled to a flow injection system

    International Nuclear Information System (INIS)

    A flow injection method is described intended for the determination of cerium based on its catalytic effect on the oxidation of gallocyanine by peroxydisulfate in acidic media. The proposed flow injection manifold incorporates a ion exchange separation system in the carrier stream. The decolorisation of gallocyanine due to its oxidation was used to monitor the reaction by spectrophotometry at 524 nm. The variables which affected the reaction rate were fully investigated. By this method cerium(4) can be determined in the range of 0.30-10.0 μg with a limit of detection of 0.25 μg. The relative standard deviation for ten replicate determinations of 1.0 μg of cerium(4) was 1.8 %

  18. Enhancing cerium and plutonium solubility by reduction in borosilicate glass

    Science.gov (United States)

    Cachia, J.-N.; Deschanels, X.; Den Auwer, C.; Pinet, O.; Phalippou, J.; Hennig, C.; Scheinost, A.

    2006-06-01

    High-level radioactive wastes produced by spent fuel reprocessing containing fission and activation products as well as actinides are incorporated in a borosilicate glass. To ensure optimum radionuclide containment, the resulting glass must be as homogeneous as possible. Microscopic heterogeneity can arise from various processes including the excess loading of an element above its solubility limit. The current actinide loading limit is 0.4 wt%. Work is in progress to assess the actinide solubility in these glasses, especially for plutonium. Initially the actinides were simulated by lanthanides and hafnium. The results show that trivalent elements (La, Gd) exhibit greater solubility than tetravalent elements (Pu, Hf). Cerium is an interesting element because its oxidation state varies from IV to III depending on the process conditions, such as the temperature and redox potential of the melt. In order to quantify the solubility increase, cerium-doped glass samples were melted under reducing conditions by adding a reducing agent. The solubility observed at 1473 K increased significantly from 0.95 to 13.00 wt%. Several reducing compounds have been tested. This paper deals with this study and the application to reduce Pu(IV) to Pu(III). The reduction state was characterized by X-ray absorption spectroscopy (XANES) for plutonium and by chemical analysis for cerium. The material homogeneity was verified by optical and scanning electron microscopy. Preliminary findings concerning the reduction of Pu-doped glasses fabricated in hot cells are also discussed.

  19. Remarkable changes in the photoluminescent properties of Y2Ce2O7:Eu(3+) red phosphors through modification of the cerium oxidation states and oxygen vacancy ordering.

    Science.gov (United States)

    Raj, Athira K V; Prabhakar Rao, P; Sreena, T S; Sameera, S; James, Vineetha; Renju, U A

    2014-11-21

    A new series of red phosphors based on Eu(3+)-doped yttrium cerate [Y1.9Ce2O7:0.1Eu(3+), Y2Ce1.9O7:0.1Eu(3+) and Y2Ce2-xO7:xEu(3+) (x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50)] was prepared via a conventional solid-state method. The influence of the substitution of Eu(3+) at the aliovalent site on the photoluminescent properties was determined by powder X-ray diffraction, FT Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy-dispersive spectroscopy, UV-visible absorption spectroscopy, photoluminescence spectroscopy and lifetime measurements. The substitution of Eu(3+) at the Ce(4+) site induces a structural transition from a defect fluorite to a C-type structure, which increases the oxygen vacancy ordering and the distortion of the Eu(3+) environment, and decreases the formation of Ce(3+) states. In contrast, phosphors with isovalent substitution at the Y(3+) site exhibit the biphasic nature of defect fluorite and a C-type structure, thereby increasing the number of Ce(3+) oxidation states. These modifications resulted in remarkable changes in the photoluminescent properties of Y2Ce1.9O7:0.1Eu(3+) red phosphors, with emission intensities 3.8 times greater than those of the Ce0.9O2:0.1Eu(3+) and Y1.9Ce2O7:0.1Eu(3+). The photoluminescent properties of Y2Ce2-xO7:xEu(3+) were studied at different Eu(3+) concentrations under excitation with blue light. These phosphors emit intense red light due to the (5)D0-(7)F2 transition under excitation at 466 nm and no concentration quenching is observed with up to 50 mol% Eu(3+). They show increased lifetimes in the range 0.62-0.72 ms at Eu(3+) concentrations. The cation ordering linked to the oxygen vacancy ordering led to the uniform distribution of Eu(3+) ions in the lattice, thus allowing higher doping concentrations without quenching and consequently increasing the lifetime of the (5)D0 states. Our results demonstrate that significant improvements in

  20. The effects of cerium doping on the size, morphology, and optical properties of α-hematite nanoparticles for ultraviolet filtration

    International Nuclear Information System (INIS)

    Highlights: • Possible application of cerium-doped α-hematite as ultraviolet filter. • Nanoparticles obtained through co-precipitation technique using various cerium doping levels followed by annealing. • Comprehensive materials characterisation utilizing XRD, DSC/TGA, STEM, UV–vis spectroscopy. • Increasing cerium content reduces particle sizing and alters morphology. • Solubility of cerium in hematite seen between 5 and 10% doping, 10% cerium doping greatly enhances attenuation in ultraviolet region and increases optical bandgap. - Abstract: Metal oxide nanoparticles have potential use in energy storage, electrode materials, as catalysts and in the emerging field of nanomedicine. Being able to accurately tailor the desirable properties of these nanoceramic materials, such as particle size, morphology and optical bandgap (Eg) is integral in the feasibility of their use. In this study we investigate the altering of both the structure and physical properties through the doping of hematite (α-Fe2O3) nanocrystals with cerium at a range of concentrations, synthesised using a one-pot co-precipitation method. This extremely simple synthesis followed by thermal treatment results in stable Fe2−xCexOy nanoceramics resulting from the burning of any unreacted precursors and transformation of goethite-cerium doped nanoparticle intermediate. The inclusion of Ce into the crystal lattice of these α-Fe2O3 nanoparticles causes a significantly large reduction in mean crystalline size and alteration in particle morphology with increasing cerium content. Finally we report an increase optical semiconductor bandgap, along with a substantial increase in the ultraviolet attenuation found for a 10% Ce-doping concentration which shows the potential application of cerium-doped hematite nanocrystals to be used as a pigmented ultraviolet filter for cosmetic products

  1. XPS study of cerium conversion coating on the anodized 2024 aluminum alloy

    International Nuclear Information System (INIS)

    Cerium-rich conversion coating was deposited on anodized aluminum alloy 2024 in a solution containing Ce(NO3)3. X-ray photoelectron spectroscopy (XPS) was used as the analysis method. The composition of the Ce conversion coating deposited on the anodized 2024 alloy was investigated using this method. It was revealed that the coating predominately consisted of three-valent state cerium compound. Some of the CeIII was oxidized to CeIV in the outer layer coating

  2. Changes in Physiological and Agronomical Parameters of Barley (Hordeum vulgare) Exposed to Cerium and Titanium Dioxide Nanoparticles

    OpenAIRE

    Luca Marchiol; Alessandro Mattiello; Filip Pošćić; Guido Fellet; Costanza Zavalloni; Elvio Carlino; Rita Musetti

    2016-01-01

    The aims of our experiment were to evaluate the uptake and translocation of cerium and titanium oxide nanoparticles and to verify their effects on the growth cycle of barley (Hordeum vulgare L.). Barley plants were grown to physiological maturity in soil enriched with either 0, 500 or 1000 mg·kg−1 cerium oxide nanoparticles (nCeO2) or titanium oxide nanoparticles (nTiO2) and their combination. The growth cycle of nCeO2 and nTiO2 treated plants was about 10 days longer than the controls. In nC...

  3. The kinetics of bromate-cerium(III) and -iron(II) reactions

    International Nuclear Information System (INIS)

    The bromate-cerium(III) and -iron(II) reactions in acidic media were examined with special reference to their induction periods and reaction rates. In the bromate-cerium(III)reaction, the induction period is followed by a burst of cerium (IV) formation and then a gradual formation of cerium(IV). In the bromate-iron(II) reaction, a slow decrease occurs only in acidic media, even without bromate, so it may differ from the decrease in the tris(1, 10-phenanthroline)iron(II) concentration based on the oxidation by bromate. Itwas interpreted as the dissociation from ( Fe(phen)3 ) 2+ to ( Fe(phen)2 ) 2+ and phen. This is the induction period for iron(III) formation, which follows as the burst. The induction period and the rates of cerium(IV) or iron(III) formation can be interpreted on the basis of the mechanism for the Belousov oscillatory and the present redox reactions proposed by Noyes and his co-workers. (author)

  4. Ionic flotation of cerium, praseodymium and neodymium

    International Nuclear Information System (INIS)

    The possibility of practically complete flotation extraction of cerium, praseodymium and neodymium ions collected with the help of potassium abietate is shown. It is established that the most complete flotation extraction of cerium, praseodymium and neodymium ions takes place from solutions having 6-8 pH value in the presence of 1.5-2.5 multiple collector surplus. Solution temperature increase from 20 to 80 deg influences positively the flotation process

  5. A study of quantitative chemical state analysis on cerium surface by using auger electron spectroscopy and factor analysis

    International Nuclear Information System (INIS)

    A reaction with oxygen during oxygen exposure to Cerium metal surface under ultra high vacuum condition and depth profiling on formed Cerium oxide layer were investigated in term of chemical state analysis by Auger electron spectroscopy (AES) and by factor analysis. Principal component analysis (PCA) on Ce NON Auger spectra suggested that three physically meaningful components existed from the analyzed data in both cases. After the PCA, three spectra were extracted from the data and these showed significant peak shape changes in each spectrum which were corresponding to different chemical states. In addition, the profiles constructed by factor analysis showed the chemical state changes on the Cerium metal surface during oxidation or chemical depth distributions in the oxide layer. (author)

  6. Luminescence properties and decay kinetics of nano ZnO powder doped with cerium ions

    Energy Technology Data Exchange (ETDEWEB)

    Panda, Nihar Ranjan, E-mail: nihar@iitbbs.ac.in [Indian Institute of Technology Bhubaneswar, Bhubaneswar 751013, Orissa (India); Acharya, B.S., E-mail: bsacharya1950@gmail.com [Department of Physics, C.V. Raman College of Engineering, Bhubaneswar 752054, Orissa (India); Singh, Th. Basanta [Luminescence Dating Laboratory, Manipur University, Imphal 795003 (India); Gartia, R.K. [Department of Physics, Manipur University, Imphal 795003 (India)

    2013-04-15

    ZnO nanopowders doped with cerium ions (1.2 and 1.5 at. wt.%) were synthesized through soft solution route using ultrasound. Sonication has been found to be an effective way for doping rare earth ions like cerium into ZnO. This was confirmed from energy dispersive analysis of X-rays (EDAX) measurement. Further, optical absorption and photoluminescence (PL) measurements corroborate this finding. X-ray diffraction (XRD) studies show the increase of crystallite size and unit cell volume with doping of cerium ions. Formation of fibrous structure of ZnO:Ce was observed from the transmission electron microscopy (TEM) measurements. Although the structural measurements indicate Ce{sup 4+} ion occupying substitutional site in ZnO, PL and absorption studies confirmed the presence of Ce{sup 3+} ion in the powder. The coexistence of Ce{sup 3+} and Ce{sup 4+} ions has been explained on the basis of conversion of Ce{sup 3+} to Ce{sup 4+} in the oxidizing environment. Thermoluminescence (TL) and photo-stimulated decay of luminescence (PSDL) decay studies give an idea of various trapping levels present in the band gap of ZnO. These traps release electrons during optical stimulation to give bimolecular kinetics in nano ZnO:Ce powders. -- Highlights: ► Sonication: an effective way of incorporation of cerium ions into ZnO. ► Site dependent characteristic emission of cerium. ► Energy transfer from host lattice to cerium ions. ► Mono and bimolecular kinetics of ZnO:Ce.

  7. Adsorbate-modified growth of ultrathin rare-earth oxide films on silicon and complementary studies of cerium oxide on ruthenium; Adsorbat-modifiziertes Wachstum ultraduenner Seltenerdoxid-Filme auf Silizium und komplementaere Studien von Ceroxid auf Ruthenium

    Energy Technology Data Exchange (ETDEWEB)

    Kaemena, Bjoern

    2013-11-27

    Rare-earth oxides (REOx) are extensively investigated due to their extraordinary physical and chemical properties, which essentially arise from the unfilled 4f electron shell, in order to reveal the nature of these exceptional properties and ultimately to utilize them for multiple technological applications. To maintain the exponential increase in integration density in CMOS technology, which is also known as Moore s law, there is a strong desire for ultrathin, well-ordered, epitaxial REOx layers with a precisely engineered interface, which is essential for reliable, ultrahigh-performance devices. So far this has been considerably impeded by RE-promoted silicon oxidation, leading to amorphous silicon oxide and RE silicon formation. By using complementary synchrotron radiation methods such as X-ray standing waves (XSW), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), structural and spectroscopic information are inferred simultaneously from ultrathin ceria and lanthana films grown on chlorine, silver and gallium passivated silicon(111). In general, it is revealed that the chemical and structural composition of the interface and the crystallinity of ultrathin REOx layers on silicon can be precisely controlled by adsorbate-mediated growth. This might represent a crucial step towards a perfectly engineered interface, eventually allowing for the integration of REOx as high-k gate oxides in microelectronics. In catalysis inverse model catalysts are studied with the aim of getting an in-depth understanding of the basic principles of catalysis. These model systems are employed to study, e. g., the nature of active sites and the reaction pathways in complex catalytic converters. However, a lot remains unknown about the chemical activity and selectivity as a function of the growth mechanism, structure and morphology of these model systems. The powerful spectroscopic photoemission and low-energy electron microscope, which is able to reveal the surface

  8. Production of CeO2 Nanoparticles by Method of Laser Ablation of Bulk Metallic Cerium Targets in Liquid

    Science.gov (United States)

    Svetlichnyi, V. A.; Lapin, I. N.

    2016-03-01

    The method of pulsed laser ablation in liquid was used to synthesize dispersions of cerium oxide nanoparticles when subjecting a metallic cerium target in water and alcohol to basic frequency radiation of the nanosecond Nd:YAG laser (1064 nm, 7 ns, 20 Hz). Researchers have studied the effect of laser radiation parameters, duration of impact, and optical scheme of experiment on the ablation process. The average rate of nanoparticle production was 50 mg/h in water and 25 mg/h in alcohol. Researchers have studied the size characteristics and crystalline structure of the nanoparticles produced. The particles have bimodal size distribution with 6 nm and 25 nm maximums. The average crystallite size is 17-19 nm. The crystalline structure of nanoparticles, namely cubic cerium oxide (fluorite structure), space group Fm-3m, is confirmed by the X-ray diffraction data, as well as optical absorption spectra and Raman spectroscopy.

  9. Properties of Cerium Containing Lead Free Solder

    Science.gov (United States)

    Xie, Huxiao

    With increasing concerns of the intrinsic toxicity of lead (Pb) in electronics, a series of tin (Sn) based alloys involving silver (Ag) and copper (Cu) have been proposed as replacements for Pb-Sn solder and widely accepted by industry. However, they have a higher melting point and often exhibit poorer damage tolerance than Pb-Sn alloys. Recently, a new class of alloys with trace amount of rare-earth (RE) elements has been discovered and investigated. In previous work from Prof. Chawla's group, it has been shown that cerium (Ce)-based Pb-free solder are less prone to oxidation and Sn whiskering, and exhibit desirable attributes of microstructural refinement and enhanced ductility relative to lanthanum (La)-based Sn-3.9Ag-0.7Cu (SAC) alloy. Although the formation of RESn3 was believed to be directly responsible for the enhanced ductility in RE-containing SAC solder by allowing microscopic voids to nucleate throughout the solder volume, this cavitation-based mechanism needs to be validated experimentally and numerically. Additionally, since the previous study has exhibited the realistic feasibility of Ce-based SAC lead-free solder alloy as a replacement to conventional SAC alloys, in this study, the proposed objective focuses on the in in-depth understanding of mechanism of enhanced ductility in Ce-based SAC alloy and possible issues associated with integration of this new class of solder into electronic industry, including: (a) study of long-term thermal and mechanical stability on industrial metallization, (b) examine the role of solder volume and wetting behavior of the new solder, relative to Sn-3.9Ag-0.7Cu alloys, (c) conduct experiments of new solder alloys in the form of mechanical shock and electromigration. The research of this new class alloys will be conducted in industrially relevant conditions, and the results would serve as the first step toward integration of these new, next generation solders into the industry.

  10. Cerium Oxyhydroxide Clusters: Formation, Structure and Reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Frederic Aubriet; Jean-Jacques Gaumet; Wibe A de Jong; Groenewold, Gary S (058000); Gianotto, Anita K (057404); McIlwain, Michael E (051783); Michael J. Van Stipdonk; Christopher M. Leavitt

    2009-06-01

    Cerium oxyhydroxide cluster anions were produced by irradiating ceric oxide particles using 355 nm laser pulses that were synchronized with pulses of nitrogen gas admitted to the irradiation chamber. The gas pulse stabilized the nascent clusters that are largely anhydrous [CexOy] ions and neutrals. These initially-formed species react with water, principally forming closed-shell (c-s) oxohydroxy species that are described by the general formula [CexOy(OH)z]-. In general, the extent of hydroxylation varies from a value of 3 OH per Ce atom when x = 1 to a value slightly greater than 1 for x > 8. The Ce3 and Ce6 species deviate significantly from this trend: the x = 3 cluster accommodates more hydroxyl moieties compared to neighboring congeners at x = 2 and x = 4. Conversely, the x = 6 cluster is significantly less hydroxylated. Density functional theory (DFT) modeling of the cluster structures show that the hydrated clusters are hydrolyzed, and contain one-to-multiple hydroxide moieties, but not datively bound water. DFT also predicts an energetic preference for formation of highly symmetric structures as the size of the clusters increases. The calculated structures indicate that the ability of the Ce3 oxyhydroxide to accommodate more extensive hydroxylation is due to a more open, hexagonal structure in which the Ce atoms can participate in multiple hydrolysis reactions. Conversely the Ce6 oxyhydroxide has an octahedral structure that is not conducive to hydrolysis. In addition to the c-s clusters, open-shell (o-s) oxyhydroxides and superoxides are also formed, and they become more prominent as the size of the clusters increases, suggesting that the larger ceria clusters have an increased ability to stabilize a non-bonding electron. The overall intensity of the clusters tends to monotonically decrease as the cluster size increases, however this trend is interrupted at Ce13, which is significantly more stable compared to neighboring congeners, suggesting formation of

  11. Cerium Oxyhydroxide Clusters: Formation, Structure and Reactivity

    Energy Technology Data Exchange (ETDEWEB)

    Aubriet, F.; Gaumet, Jean-Jacques; De Jong, Wibe A.; Groenewold, G. S.; Gianotto, Anita K.; McIIwain, Michael E.; Van Stipdonk, Michael J.; Leavitt, Christopher M.

    2009-05-11

    Cerium oxyhydroxide cluster anions were produced by irradiating ceric oxide particles using 355 nm laser pulses that were synchronized with pulses of nitrogen gas admitted to the irradiation chamber. The gas pulse stabilized the nascent clusters that are largely anhydrous [CexOy] ions and neutrals. These initially-formed species react with water, principally forming closed-shell (c-s) oxohydroxy species that are described by the general formula [CexOy(OH)z]-. In general, the extent of hydroxylation varies from a value of 3 OH per Ce atom when x = 1 to a value slightly greater than 1 for x > 8. The Ce3 and Ce6 species deviate significantly from this trend: the x = 3 cluster accommodates more hydroxyl moieties compared to neighboring congeners at x = 2 and x = 4. Conversely, the x = 6 cluster is significantly less hydroxylated. Density functional theory (DFT) modeling of the cluster structures show that the hydrated clusters are hydrolyzed, and contain one-to-multiple hydroxide moieties, but not datively bound water. DFT also predicts an energetic preference for formation of highly symmetric structures as the size of the clusters increases. The calculated structures indicate that the ability of the Ce3 oxyhydroxide to accommodate more extensive hydroxylation is due to a more open, hexagonal structure in which the Ce atoms can participate in multiple hydrolysis reactions. Conversely the Ce6 oxyhydroxide has an octahedral structure that is not conducive to hydrolysis. In addition to the c-s clusters, open-shell (o-s) oxyhydroxides and superoxides are also formed, and they become more prominent as the size of the clusters increases, suggesting that the larger ceria clusters have an increased ability to stabilize a non-bonding electron. The overall intensity of the clusters tends to monotonically decrease as the cluster size increases, however this trend is interrupted at Ce13, which is significantly more stable compared to neighboring congeners, suggesting formation of

  12. Evolution of the local environment of cerium and neodymium during simplified SON68 glass alteration

    Energy Technology Data Exchange (ETDEWEB)

    Jollivet, Patrick [Commissariat a l' Energie Atomique (CEA), Rhone Valley Research Center, BP 17171, 30207 Bagnols-sur-Ceze (France)]. E-mail: patrick.jollivet@cea.fr; Lopez, Christophe [Commissariat a l' Energie Atomique (CEA), Rhone Valley Research Center, BP 17171, 30207 Bagnols-sur-Ceze (France); Auwer, Christophe Den [Commissariat a l' Energie Atomique (CEA), Rhone Valley Research Center, BP 17171, 30207 Bagnols-sur-Ceze (France); Simoni, Eric [Institut de Physique Nucleaire, Batiment 100, 91406 Orsay cedex (France)

    2005-11-15

    The evolution of the sites occupied by cerium and neodymium (coordination numbers and Ce, Nd-O distances) during alteration of simplified SON68 glass specimens was determined by L{sub III}-edge XAS. Cerium and neodymium are situated in a silicate environment in the glass, surrounded by eight oxygen atoms at an average distance of 2.44 and 2.48 A, respectively. These two rare earth elements exhibit different leaching behavior, however. The main environment of cerium becomes a silicate (d {sub Ce-O} = 2.19 A) with a second oxide or more probably oxyhydroxide site (d {sub Ce-O} = 2.32 A). The cerium coordination number increases by 1 to 3 compared with the glass, depending on the leaching conditions. Neodymium is found mainly in a hydroxycarbonate environment (d {sub Nd-O} = 2.46 A); the second site is a silicate (d {sub Nd-O} = 2.54 A). The neodymium coordination number increases by 1 compared with the glass. When glass containing neodymium is doped with phosphorus, Nd is situated in a phosphate environment; this change is also reflected in the coordination number and Nd-O distance (seven oxygen atoms at 2.42 A). During glass leaching, neodymium is present at two different sites, phosphate (d {sub Nd-O} = 2.52 A) and hydroxycarbonate (d {sub Nd-O} = 2.40 A)

  13. EXAFS and XANES analysis of plutonium and cerium edges from titanate ceramics for fissile materials disposal

    International Nuclear Information System (INIS)

    We report x-ray absorption near edge structure (XANES) and extended x-ray absorption fine structure (EXAFS) spectra from the plutonium LIII edge and XANES from the cerium LII edge in prototype titanate ceramic hosts. The titanate ceramics studied are based upon the hafnium-pyrochlore and zirconolite mineral structures and will serve as an immobilization host for surplus fissile materials, containing as much as 10 weight % fissile plutonium and 20 weight % (natural or depleted) uranium. Three ceramic formulations were studied: one employed cerium as a ''surrogate'' element, replacing both plutonium and uranium in the ceramic matrix, another formulation contained plutonium in a ''baseline'' ceramic formulation, and a third contained plutonium in a formulation representing a high-impurity plutonium stream. The cerium XANES from the surrogate ceramic clearly indicates a mixed III-IV oxidation state for the cerium. In contrast, XANES analysis of the two plutonium-bearing ceramics shows that the plutonium is present almost entirely as Pu(IV) and occupies the calcium site in the zirconolite and pyrochlore phases. The plutonium EXAFS real-space structure shows a strong second-shell peak, clearly distinct from that of PuO2, with remarkably little difference in the plutonium crystal chemistry indicated between the baseline and high-impurity formulations

  14. Study of the discharge ionization of cerium at a solid-paste graphite electrode

    International Nuclear Information System (INIS)

    The discharge ionization of cerium(3) at a solid-paste graphite electrode was studied by stripping voltametry. The optimal conditions for the concentration and following determination of cerium in 1 x 10-4 - 1 x 10-6 M cerium(3) solutions were found. The conditional constant of cerium(4) reduction to cerium(3) was also calculated

  15. Effect of Rare Earth Element Cerium on Mechanical Properties and Morphology of TiN Coating Prepared by Arc Ion Plating

    Institute of Scientific and Technical Information of China (English)

    黄拿灿; 胡社军; 谢光荣; 曾鹏; 汝强

    2003-01-01

    TiN coatings were deposited on polished substrates of W18Cr4V high speed steel by means of vacuum arc ion plating. The effect of cerium on adhesion between TiN coating and substrate was studied. The microstructures and composition of TiN coatings were also investigated by means of scanning electron microscope (SEM), Auger electron spectroscopy (AES), and X-ray diffraction (XRD) technique. It was found that cerium is an effective modifying agent and the addition of suitable amount of cerium to TiN coatings can produce relatively excellent properties such as micro-hardness, wear resistance, oxidation resistance and porosity. The experimental results show that the added cerium in TiN coatings makes a contribution to form the preferred direction along with a (111) or (222) close packed face, which may be one of the reasons that improves some properties mentioned above.

  16. New layered functionalized cerium(IV) phenylphosphonates

    Czech Academy of Sciences Publication Activity Database

    Melánová, Klára; Beneš, L.; Svoboda, Jan; Zima, Vítězslav; Vlček, Milan

    Lille: European Materials Research Society, 2014. Q.PI-20. [E- MRS 2014 Spring Meeting. 26.05.2014-30.05.2014, Lille] R&D Projects: GA ČR(CZ) GA14-13368S Institutional support: RVO:61389013 Keywords : cerium * layered phosphonates * thermogravimetry Subject RIV: CA - Inorganic Chemistry

  17. Electron transfer behavior and water photodecomposition ability of calcined material from a cerium-S-phenylene-O-holmium-O-phenylene-S hybrid copolymer.

    Science.gov (United States)

    Matsui, Hideo; Otsuki, Keigo; Yamada, Hiroyoshi; Kawahara, Tetsuro; Yoshihara, Masakuni

    2006-05-15

    Calcination of a cerium-S-phenylene-O-holmium-O-phenylene-S hybrid copolymer under a vacuum gave cerium oxide-carbon cluster-holmium oxide composite material. The material calcined at 600 degrees C loaded with Pt particles could decompose water to H2 and O2 with a H2/O2 ratio of 2 under visible light irradiation. ESR spectral examinations of the calcined materials revealed the possibility of a two-step electron transfer in the process of CeO2 --> carbon cluster --> Ho2O3 --> Pt with an oxidation site at CeO2 particles and a reduction site at Pt particles. PMID:16313919

  18. Catalytic activity of cerium-doped Ru/Al2O3 during ozonation of dimethyl phthalate

    Institute of Scientific and Technical Information of China (English)

    Yunrui ZHOU; Wanpeng ZHU; Xun CHEN

    2008-01-01

    In this paper, factors influencing the mineraliza-tion of dimethyl phthalate (DMP) during catalytic ozona-tion with a cerium-doped Ru/Al2O3 catalyst were studied. The catalytic contribution was calculated through the results of a companrison experiment. It showed that doping cerium significantly enhanced catalytic activity. The total organic carbon (TOC) removal over the doped catalyst at 100 rain reached 75.1%, 61.3% using Ru/Al2O3 catalyst and only 14.0% using ozone alone. Catalytic activity reached the maximum when 0.2% of ruthenium and 1.0% of cerium'were simultaneously loaded onto Al2O3 support. Results of experiments on oxidation by ozone alone, adsorption of the catalyst, Ce ion's and heterogeneous catalytic ozonation confirmed that the contribution of het-erogeneous catalytic ozonation was about 50%, which showed the obvious effect of Ru-Ce/Al2O3 on catalytic activity.

  19. Management of decontamination solution arising from Cerium redox process

    International Nuclear Information System (INIS)

    This paper describes the recovery of Pu from decontamination stream generated from Cerium Redox Process meant for decontamination of contaminated metallic wastes. Extraction of Pu is carried out using PUREX solvent after reducing it to tetravalent state which is subsequently stripped using hydroxylamine nitrate and nitric acid mixture. Raffinate from this step containing Ce3+, 241Am and corrosion products is subjected to ozonisation wherein Ce3+ is oxidized to Ce4+. Quantitative extraction of Ce is achieved by PUREX solvent in second cycle which is stripped using a mixture of NaNO2 and HNO3. Raffinate from this step contains 241Am and corrosion product which is removed by solvent extraction using TEHDGA. The final alpha lean waste can be managed by cementation. (author)

  20. Thermodynamic studies in the system cerium-gadolinium-oxygen

    International Nuclear Information System (INIS)

    Two independent measuring methods have been applied to studying the phase relations of the system cerium-gadolinium. The calorimetric measurements have been done in a high-temperature calorimeter with cerium dioxide doped with 10 mole % of Gd2O3. Further thermodynamic quantities have been obtained by the electrochemical method and e.m.f. measurements, yielding additional information on disorders in doped cerium dioxide. (orig./BBR)

  1. Thermal decomposition study of uranyl nitrate and cerium hydroxide in a spray dryer

    International Nuclear Information System (INIS)

    A study, in a spray dryer system based on drying and thermal decomposition of uranyl nitrate solutions aiming the production of uranium trioxide adequate for the use in posterior steps of reduction and hydro fluorination in nuclear fuel cycle; and cerium hydroxide suspensions for the production of cerium oxide with high surface area is presented. Thus, the project and construction of a countercurrent spray dryer was elaborated for capacity of 10 Kg U O3/h and 3,5 k Ce O2/h. The methodology used in these experiments consisted in the analysis of several parameters (concentration and flow rate of the feed, atomization pressure and inlet temperature of the dryer) over the physical and chemical properties of the products. Using the obtained results, with the help of a mathematical model, it was developed the project of a continuous pilot unity for the production of uranium trioxide or cerium oxide, with capacity of 20 Kg U O3/h or 10 Kg Ce O2/h, respectively. (author)

  2. Cerium-based coating for enhancing the corrosion resistance of bio-degradable Mg implants

    International Nuclear Information System (INIS)

    Recently there has been interest in employing degradable metallic implants for internal fixation in bone fracture healing. The major purpose of using degradable implants is to avoid a second surgery for implant removal when bone healing has completed. However, the corrosion rate of Mg in vivo is too high. Thus increasing the corrosion resistance of Mg is the key problem to address in the development of degradable Mg implants. One possible route is by way of surface treatment, which would lower the corrosion rate at the initial phase of bone healing, the period during which the implant provides mechanical support for the broken bone. In the present study cerium oxide coating was prepared on pure Mg by cathodic deposition in cerium nitrate solution followed by hydrothermal treatment. The coated samples were characterized by SEM, EDS and XRD. The corrosion resistance in Hanks' solution (a simulated body fluid) was studied using polarization method and electrochemical impedance spectroscopy (EIS). The corrosion resistance of cerium oxide coated Mg in Hanks' solution at 37 deg. C and pH 7.4 was higher than that of bare Mg by about two orders of magnitude.

  3. Cerium and jojoba in engines?; Cerium et jojoba dans les moteurs?

    Energy Technology Data Exchange (ETDEWEB)

    Massy-Delhotel, E.

    1996-10-01

    The Belgium company CreaTel proposes a new system, called Forac, which can lead to a 10% reduction of fuel consumption in thermal engines together with a quasi-complete reduction of CO, HC, NOx pollutants and CO{sub 2} particulates emission. The system comprises a steam production device and an admission pipe with a cerium alloy whorl inside. The steam produced is mixed with the admission air and tears cerium particles from the inside of the admission pipe to the combustion chamber. The cerium particles act as a catalyst which favours the complete combustion of the fuel. The same company proposes also lubricant additives made from liquid jojoba wax which allow the reduction of pollutant emissions, fuel consumption and noise emissions of diesel engines. (J.S.)

  4. Recovery of Cerium Dioxide from Spent Glass-Polishing Slurry and Its Utilization as a Reactive Sorbent for Fast Degradation of Toxic Organophosphates

    Directory of Open Access Journals (Sweden)

    Pavel Janoš

    2015-01-01

    Full Text Available The recovery of cerium (and possibly other rare earth elements from the spent glass-polishing slurries is rather difficult because of a high resistance of polishing-grade cerium oxide toward common digestion agents. It was shown that cerium may be extracted from the spent polishing slurries by leaching with strong mineral acids in the presence of reducing agents; the solution may be used directly for the preparation of a ceria-based reactive sorbent. A mixture of concentrated nitric acid and hydrogen peroxide was effective in the digestion of partially dewatered glass-polishing slurry. After the removal of undissolved particles, cerous carbonate was precipitated by gaseous NH3 and CO2. Cerium oxide was prepared by a thermal decomposition of the carbonate precursor in an open crucible and tested as reactive sorbent for the degradation of highly toxic organophosphate compounds. The samples annealed at the optimal temperature of approximately 400°C exhibited a good degradation efficiency toward the organophosphate pesticide fenchlorphos and the nerve agents soman and VX. The extraction/precipitation procedure recovers approximately 70% of cerium oxide from the spent polishing slurry. The presence of minor amounts of lanthanum does not disturb the degradation efficiency.

  5. Cobalt, titanium or cerium oxide protective coatings for the nickel cathode of the molten carbonate fuel cells; Revetements protecteurs a base d'oxyde de cobalt, de titane ou de cerium pour la cathode de nickel des piles a combustible a carbonates fondus

    Energy Technology Data Exchange (ETDEWEB)

    Mendoza Blanco, L.

    2003-10-15

    The aim of this work is to combine the MCFC cathode Li{sub x}Ni{sub 1-x}O properties to those of the protective coatings of LiCoO{sub 2}, Li{sub 2}TiO{sub 3} or of CeO{sub 2}, less soluble in the molten carbonates. In the cases of LiCoO{sub 2}, have been carried out by controlled potential coulometry in aqueous solution, a deposition of Co{sub 3}O{sub 4} on dense Ni. The cobalt oxide reacts rapidly in the Li{sub 2}CO{sub 3}-Na{sub 2}CO{sub 3} medium at 650 C to give LiCoO{sub 2}, a spinel cubic phase revealed by Raman spectroscopy. (O.M.)

  6. Analysis of single and binary phases in cerium doped sodium bismuth titanate -inorganic materials Na{sub 0}.5Bi{sub (}0.5-x)Ce{sub x}TiO{sub 3}; Estudio de fases simples y binarias en BNT puro y dopado con cerio Na{sub 0},5Bi{sub (}0,5-x)Ce{sub x}TiO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Supriya, S.; Dos Santos-Garcia, A. J.; Frutos, J. de; Fernandez-Martinez, F.

    2015-07-01

    The pure and cerium doped sodium bismuth titanate (NBT) inorganic powders were synthesized by solid-state reaction method. The presence of rhombohedral phase was observed in cerium doped NBT compounds. When x= 0.05 of cerium doped NBT is heat treated at 1200 degree centigrade, the compound forms single perovskite phase. The samples of x = 0.10 and 0.15 were heat treated up to 1350 degree centigrade, the binary phases with cerium and bismuth oxides were observed. The X-ray diffraction, Fourier transform infrared spectroscopy, reflectance spectra, differential thermal analysis and thermogravimetric analysis were used to analyze the various properties of samples. Moreover, the effects of cerium doping and calcining temperature on NBT samples were investigated. In this work, we present our recent results on the synthesis and characterization of cerium doped sodium bismuth titanate materials. (Author)

  7. Radiation induced color centers in cerium-doped and cerium-free multicomponent silicate glasses

    Institute of Scientific and Technical Information of China (English)

    傅鑫杰; 宋力昕; 李家成

    2014-01-01

    The effect of doped cerium on the radiation-resistance behavior of silicate glass was investigated in our work. The ultra-violet-visible absorption spectra and electron paramagnetic resonance (EPR) spectra were obtained after the cerium-rich and ce-rium-free multicomponent silicate glasses (K509 and K9) were irradiated by gamma rays with a dose range from 10 to 1000 kGy. The results showed that E’ center, oxygen deficient center (ODC) and non-bridging oxygen hole center (HC1 and HC2) were induced in K9 and K509 glasses after radiation. The concentrations of all color centers presented an exponential growth with the increase of the gamma dose. Moreover, the concentration of HC1 and HC2 in cerium-doped K509 glass was much lower than that in cerium-free K9 glass at the same dose of radiation, which could be attributed to the following mechanism:Ce3+ions capturing holes then forming Ce3++centers inhibited the formation of hole trapped color centers (HC1 and HC2) and Ce4+ions capturing electrons to form Ce3+centers suppressed the formation of electron trapped color centers like E’ center.

  8. The role of hydrogen peroxide in the deposition of cerium-based conversion coatings

    International Nuclear Information System (INIS)

    Cerium-based conversion coatings are progressing as an effective alternative to hazardous chromate-based systems used in the treatment of metal surfaces. However, there is still considerable debate over the mechanism by which these coatings are formed. Here, titrations of cerium-based conversion coating solutions were carried out in order to model the reactions that occur at the metal-solution interface during coating, with a particular emphasis on investigating the role of hydrogen peroxide (H2O2). The titration curves obtained support the proposed formation of Ce(III) peroxo complexes such as Ce(H2O2)3+ as an initial step, followed by deprotonation, oxidation and precipitation to form peroxo-containing Ce(IV) species such as Ce(IV)(O2)(OH)2. The precipitates resulting from titrations were characterised by Raman spectroscopy, X-ray diffraction and thermogravimetric analysis, confirming the presence of peroxo bonds, and nano-sized CeO2 crystallites that decreased in size with increasing H2O2 concentration. Characterisation of cerium conversion coatings on aluminium alloy surfaces confirmed the presence of peroxo species in the coatings, thereby supporting the titration model

  9. Cerium Biomagnification in a Terrestrial Food Chain: Influence of Particle Size and Growth Stage.

    Science.gov (United States)

    Majumdar, Sanghamitra; Trujillo-Reyes, Jesica; Hernandez-Viezcas, Jose A; White, Jason C; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge L

    2016-07-01

    Mass-flow modeling of engineered nanomaterials (ENMs) indicates that a major fraction of released particles partition into soils and sediments. This has aggravated the risk of contaminating agricultural fields, potentially threatening associated food webs. To assess possible ENM trophic transfer, cerium accumulation from cerium oxide nanoparticles (nano-CeO2) and their bulk equivalent (bulk-CeO2) was investigated in producers and consumers from a terrestrial food chain. Kidney bean plants (Phaseolus vulgaris var. red hawk) grown in soil contaminated with 1000-2000 mg/kg nano-CeO2 or 1000 mg/kg bulk-CeO2 were presented to Mexican bean beetles (Epilachna varivestis), which were then consumed by spined soldier bugs (Podisus maculiventris). Cerium accumulation in plant and insects was independent of particle size. After 36 days of exposure to 1000 mg/kg nano- and bulk-CeO2, roots accumulated 26 and 19 μg/g Ce, respectively, and translocated 1.02 and 1.3 μg/g Ce, respectively, to shoots. The beetle larvae feeding on nano-CeO2 exposed leaves accumulated low levels of Ce since ∼98% of Ce was excreted in contrast to bulk-CeO2. However, in nano-CeO2 exposed adults, Ce in tissues was higher than Ce excreted. Additionally, Ce content in tissues was biomagnified by a factor of 5.3 from the plants to adult beetles and further to bugs. PMID:26690677

  10. Effect of Cerium(IV)-Surfactant Reaction in Foam Decontamination

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Han Beom; Jung, Chong-Hun; Yoon, In-Ho; Kim, Chorong; Choi, Wang-Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    Using foams allows the decommissioning of complex shaped facilities. The decontamination foam comprises at least one surfactant to generate the foam and one or more chemical reactants to achieve the dissolution of the contaminants at the solid surface. In order to improve the efficiency of decontamination foam, the present study attempts to find the optimum condition of chemical reagents to the foaming solution. The corrosion rate of radioactive nuclides contaminated stainless steel metal is very important factor for the foam decontamination process. The goal of this study is to develop the decontamination process for contaminated stainless steel in medium of nitric acid. Stainless steel needs a strong oxidizing agent such as Ce(IV) ion and the effects of cerium(IV). Surfactant interaction involved in foam decontamination and finally the improvement brought by formulation science. The formulation of foams loaded with strong oxidizing reagents such as Ce(IV) is an important factor. The enhanced decontamination properties of nitric acid with Ce(IV) additive on stainless steel is well known in liquid mediums. stainless steel metal is an important aspect in the foam decontamination process.

  11. Effect of Cerium(IV)-Surfactant Reaction in Foam Decontamination

    International Nuclear Information System (INIS)

    Using foams allows the decommissioning of complex shaped facilities. The decontamination foam comprises at least one surfactant to generate the foam and one or more chemical reactants to achieve the dissolution of the contaminants at the solid surface. In order to improve the efficiency of decontamination foam, the present study attempts to find the optimum condition of chemical reagents to the foaming solution. The corrosion rate of radioactive nuclides contaminated stainless steel metal is very important factor for the foam decontamination process. The goal of this study is to develop the decontamination process for contaminated stainless steel in medium of nitric acid. Stainless steel needs a strong oxidizing agent such as Ce(IV) ion and the effects of cerium(IV). Surfactant interaction involved in foam decontamination and finally the improvement brought by formulation science. The formulation of foams loaded with strong oxidizing reagents such as Ce(IV) is an important factor. The enhanced decontamination properties of nitric acid with Ce(IV) additive on stainless steel is well known in liquid mediums. stainless steel metal is an important aspect in the foam decontamination process

  12. Cerium regulates expression of alternative methanol dehydrogenases in Methylosinus trichosporium OB3b.

    Science.gov (United States)

    Farhan Ul Haque, Muhammad; Kalidass, Bhagyalakshmi; Bandow, Nathan; Turpin, Erick A; DiSpirito, Alan A; Semrau, Jeremy D

    2015-11-01

    Methanotrophs have multiple methane monooxygenases that are well known to be regulated by copper, i.e., a "copper switch." At low copper/biomass ratios the soluble methane monooxygenase (sMMO) is expressed while expression and activity of the particulate methane monooxygenase (pMMO) increases with increasing availability of copper. In many methanotrophs there are also multiple methanol dehydrogenases (MeDHs), one based on Mxa and another based on Xox. Mxa-MeDH is known to have calcium in its active site, while Xox-MeDHs have been shown to have rare earth elements in their active site. We show here that the expression levels of Mxa-MeDH and Xox-MeDH in Methylosinus trichosporium OB3b significantly decreased and increased, respectively, when grown in the presence of cerium but the absence of copper compared to the absence of both metals. Expression of sMMO and pMMO was not affected. In the presence of copper, the effect of cerium on gene expression was less significant, i.e., expression of Mxa-MeDH in the presence of copper and cerium was slightly lower than in the presence of copper alone, but Xox-MeDH was again found to increase significantly. As expected, the addition of copper caused sMMO and pMMO expression levels to significantly decrease and increase, respectively, but the simultaneous addition of cerium had no discernible effect on MMO expression. As a result, it appears Mxa-MeDH can be uncoupled from methane oxidation by sMMO in M. trichosporium OB3b but not from pMMO. PMID:26296730

  13. Radiative lifetimes of singly ionized cerium

    International Nuclear Information System (INIS)

    Radiative lifetimes accurate to ±5% have been measured for 74 levels in Ce II using time-resolved laser-induced fluorescence on a slow beam of cerium ions. The 17 odd-parity and 57 even-parity levels studied here lie in the energy range 24 000-36 000 cm-1. This new set of lifetimes in Ce II is substantially more extensive than previously published sets, to which a detailed comparison is made. The present lifetime results will provide the absolute calibration for a very large set of measured transition probabilities for Ce II. These are needed for research in astrophysics and lighting

  14. Radiative lifetimes of singly ionized cerium

    Energy Technology Data Exchange (ETDEWEB)

    Hartog, E A Den; Lawler, J E [Department of Physics, University of Wisconsin, Madison, WI 53706 (United States)], E-mail: eadenhar@wisc.edu, E-mail: jelawler@wisc.edu

    2008-02-28

    Radiative lifetimes accurate to {+-}5% have been measured for 74 levels in Ce II using time-resolved laser-induced fluorescence on a slow beam of cerium ions. The 17 odd-parity and 57 even-parity levels studied here lie in the energy range 24 000-36 000 cm{sup -1}. This new set of lifetimes in Ce II is substantially more extensive than previously published sets, to which a detailed comparison is made. The present lifetime results will provide the absolute calibration for a very large set of measured transition probabilities for Ce II. These are needed for research in astrophysics and lighting.

  15. Crystal structure of cerium(4) - dicesium trisulfate

    International Nuclear Information System (INIS)

    Cerium(4) - dicesium trisulfate is investigated by the X-ray diffraction method. Parameters of a monoclinic cell equal: a = 9.772(2), b = 16.797(2), c = 14.812(1)A, β 96.40(1), sp.gr. P21. The structure is formed by interchanging of anion [Ce4(SO4)128-]∞ and cation (Cs+) layers arranged parallel (101). Atoms Ce and Cs are arranged according to the law of a cubic close packing. Coordination polyhedron Ce1 and Ce2 is the two-hat trigonal prism, nine vertices Ce3 and Ce4 are one-hat antiprism

  16. Lanthanum, cerium, praseodymium, and neodymium metals and their interaction with oxygen studied by photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Clean films of La, Ce, Pr, and Nd, prepared by in situ evaporation have been investigated by photoelectron spectroscopy. Different light sources He I (hv = 21.2 eV), He II (hv = 40.8 eV) and Mg Kα (hv = 1253.6 eV) have been used for the electron excitation in order to characterize the metals. Measurements have been performed after exposing the clean metals to various amounts of oxygen. From the vanishing of the emission from the sd conduction band upon exposure the conclusion is drawn that an oxide layer thicker than the probing depth (20 A) is formed on all four metals and that the oxide (at room temperature) has the form: Me2O3, Me=La, Ce, Pr, Nd. The tetravalent cerium oxide is obtained when the film is heated to about 6000C during oxygen exposure. The interaction with oxygen is also characterized by recording the oxygen 1s level and some metal core levels (Me 3d, 4d and 4p). The results from the pure metals and from the metal oxides give further experimental evidence for a 4f level binding energy of 1.9 eV in γ-cerium. (Auth.)

  17. Low soluble cerium compounds in salt melts

    International Nuclear Information System (INIS)

    The behaviour of cerium tungstate NaCe(WO4)2 and cerium phosphate Na3Ce2(PO4)3 in high-temperature salt melts has been investigated. The solubility in the NaCe(WO4)2-NaWO4-NaCl(1) and Na3Ce2(PO4)3-Na2WO4-NaCl(2) systems at 700-800 deg C has been studied. It is shown, that with the increase of the Na2WO4 part in systems (1), (2) the solubility increases in the following way: for NaCe(WO4)2 from 1.3x10-3 m in NaCl melt to 4.9x10-3 m in NaWO4 melt, for Na3Ce2(PO4)3 from 0.4x10-3 m in NaCl melt to 5.7x10-3 m in NaWO4 melt. With an increase in the Na2WO4 part in system (2) the formation of a new phase - NaCe(WO4)2 is observed. The melting enthalpy of NaCe(WO4)2 is 19+-3 kJ/mol

  18. Effect of cerium on ignition point of AZ91D magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    Zhao Hongjin; Zhang Yinghui; Kang Yonglin

    2008-01-01

    The surface and interior temperature-time curves of blocky cerium modified AZ91D magnesium alloy were measured during a non-protective heating and melting process. Two inflection points with rapid increase in temperature were found on both curves, which corresponded to the formation of "auliflower" oxide on the surface and the occurrence of flame during melting. These two temperatures are therefore defined as oxidation point and ignition point, respectively.The interior temperature-time curve is similar to that measured on the surface except for a comparable time delay. The oxidation and ignition temperatures increase with Ce content, an average increase of 33℃ and 61℃ was found when Ce addition was about 1.0 wt %. However, the increasing rate of the oxidation and ignition temperature decreases with increasing Ce content. An addition of 0.6wt% Ce is recommended for ignition-resistant AZ91 magnesium alloy.

  19. Effect of Cerium on Oxidation Resistance and Microstructure of Hot Dip Aluminum Coating on HP40Nb Steel%Ce对热浸镀铝HP40Nb钢氧化行为及组织的影响研究

    Institute of Scientific and Technical Information of China (English)

    钱庆生; 李海; 王芝秀; 史志欣; 王秀丽

    2012-01-01

    通过SEM,EDS和XRD研究了Ce对HP40Nb热浸镀铝层组织结构和高温抗氧化性能的影响.结果表明,热浸镀过程中添加质量分数1%Ce促进了镀层外层中Fe2Al5和Fe4Al3Ce相的生成,抑制了内层Fe2Al5相长大;在1 000 ℃/4 h扩散处理过程中,Ce促进了γ向α相的转变以及α相中Ni3Al相的析出,并在渗层内层中生成富Ce相;800C/360 h氧化后,Ce促使渗层外层生成少量Fe2Al5和Cr3Si相,并使渗层外层组织均匀致密;1000℃/360 h氧化后,Ce促使α相长大导致渗层中生成大量的σ相.800℃氧化实验发现1%Ce使渗层组织致密,提高了渗层高温抗氧化性;1 000℃氧化实验发现1%Ce促进了渗层中σ相的生成,阻碍了Al原子的内扩散,保证了氧化过程中渗层表面生成α - Al2O3所需铝含量.%The effect of rare earth Ce on the microstrueture of HDA. coating on HP40Nb steel have been studied by means of SEM,EDS and XRD. The oxidation resistance of the coating was also studied at 800 ℃ and 1000t for 360 h respectively. The results show that the specimen after hot dipped All % Ce can promote the formation of Fe2 Al5 and Fe4 Al3Ce phase at the outer layer,while inhibit the growth of Fe2Al5 at the inner layer;In the diffusion processing at 1 000 ℃ for 4 h,rare earth Ce promoted the transformation from the a phase to γ phase and the precipitation of Ni3 Al in the phase of a,meanwhile produced the Ce-rich phase in the inner diffusion layer; After the cyclic oxidation test at 800 ℃ for 360 h,the outer diffusion layer generated little Fe2 Al5 and Cr3 Si phase and became homogeneously and densely promoted by the rare earth Ce; After the cyclic oxidation test at 1 000 ℃ for 360 h, the rare earth Ce promoted the growth of a phase and produced considerable σ phase at the diffusion layer. In the cyclic oxidation progress at 800 ℃ for 360h,the rare earth Ce can improve the high-temperature oxidation resistance because of the dense diffusion layer;In the

  20. Bordoni relaxation and magnetic transformation in cerium and cerium-lanthanum alloys

    International Nuclear Information System (INIS)

    The internal friction in pure cerium and cerium-base alloys with 2.5 and 12 weight percent of lanthanum added at temperature ranging from 4.2 deg up to 77 deg K is described. Amplitude-independent internal friction has been measured with an inverse torsion pendulum with a specimen oscillation frequency of 1-30 hz in vacuum not less than 1.10-5 torr. A temperature of the specimen has been determined with a capacitance-type sensor and a gas gauge. A curve showing the dependence of internal friction upon a temperature of pure cerium has two distinct peaks; the first at 12.5 deg K, the second at 45 deg K. The 12.5 deg K peak is accounted for by a transition of antiferromagnetic β-Ce into a paramagnetic state. The 45 deg K peak is a Bordoni maximum. The paper describes an influence of additions, specimen oscillation frequency variations, deformation and annealing upon the peak behaviour. Added lanthanum reduces not only a peak temperature but a height as well. Studies of the 45 deg K peak have shown that its temperature location depends upon the specimen oscillation frequency. As the frequency increases the peak tends to a range of high temperatures which confirms its relaxation nature

  1. Electron inelastic mean free paths in cerium dioxide

    Science.gov (United States)

    Krawczyk, M.; Holdynski, M.; Lisowski, W.; Sobczak, J. W.; Jablonski, A.

    2015-06-01

    Electron transport properties in CeO2 powder samples were studied by elastic-peak electron spectroscopy (EPES). Prior to EPES measurements, the CeO2 sample surface was pre-sputtered by 0.5 keV Ar ion etching. As a result, an altered layer with thickness of 1.3 nm was created. X-ray photoelectron spectroscopy (XPS) analysis revealed two chemical states of cerium Ce4+ (68%) and Ce3+ (32%) at the surface region of CeO2 sample after such treatment. The inelastic mean free path (IMFP), characterizing electron transport, was evaluated as a function of energy within the 0.5-2 keV range. Experimental IMFPs were corrected for surface excitations and approximated by the simple function λ = kEp, where λ was the IMFP, E denoted the energy (in eV), and k = 0.207 and p = 0.6343 were the fitted parameters. The IMFPs measured here were compared with IMFPs resulting from the TPP-2M predictive equation for the measured composition of oxide surface. The measured IMFPs were found to be from 3.1% to 20.3% smaller than the IMFPs obtained from the predictive formula in the energy range of 0.5-2 keV. The EPES IMFP value at 500 eV was related to the altered layer of sputtered CeO2 samples.

  2. Yttrium and lanthanum recovery from low cerium carbonate, yttrium carbonate and yttrium concentrate

    International Nuclear Information System (INIS)

    In this work, separation, enrichment and purification of lanthanum and yttrium were performed using as raw material a commercial low cerium rare earth concentrate named LCC (low cerium carbonate), an yttrium concentrate named 'yttrium carbonate', and a third concentrated known as 'yttrium earths oxide. The first two were industrially produced by the late NUCLEMON - NUCLEBRAS de Monazita e Associados Ltda, using Brazilian monazite. The 'yttrium earths oxide' come from a process for preparation of lanthanum during the course of the experimental work for the present thesis. The following techniques were used: fractional precipitation with urea; fractional leaching of the LCC using ammonium carbonate; precipitation of rare earth peroxycarbonates starting from the rare earth complex carbonates. Once prepared the enriched rare earth fractions the same were refined using the ion exchange chromatography with strong cationic resin without the use of retention ion and elution using the ammonium salt of ethylenediaminetetraacetic acid. With the association of the above mentioned techniques were obtained pure oxides of yttrium (>97,7%), lanthanum (99,9%), gadolinium (96,6%) and samarium (99,9%). The process here developed has technical and economic viability for the installation of a large scale unity. (author)

  3. Preparing Process of Cerium Acetate and Rare Earth Acetate

    Institute of Scientific and Technical Information of China (English)

    Qiao Jun; Ma Ying; Xu Yanhui; Zhang Jun; Chang Shu; Hao Xianku

    2004-01-01

    Preparing process was presented and the influences of concentration of acetic acid, reaction temperature, the ratio of cerium carbonate and acetic acid, heat preservation time to the yield of cerium acetate were discussed.The crystalline cerium acetate and rare earth acetate such as ( La, Ce, Pr, Nd) (Ac) 3, ( Ce, Pr, Nd) (Ac) 3, ( Pr, Nd, Er,Y) (Ac) 3 and yttrium acetate were prepared under this condition.The shape, structure and composition of the crystals were determined by the methods of SEM, TG-DTA, X-ray diffraction and chemical analysis.The optimum prepared conditions of cerium acetate were described.This prepared process has characteristics such as simple process route, low cost, high yield, good quality, no pollution to environment, etc.

  4. Adsorption of Some Hazardous Radionuclides on Cerium(IV) Antimonate

    International Nuclear Information System (INIS)

    Cerium(IV) antimonate had been prepared by the dropwise addition of 0.6 M antimony pentachloride and 0.6 M cerium ammonium nitrate solutions by a molar radio of Ce/Sb 0.75. Exchange isotherms for H+/Co2+ , H+/Cs+, H+/Zn2+ , H+/Sr2+ and H+/Eu3+ have been determined at 25, 40 and 60 degree. Besides it was proved that europium is physically adsorbed while zinc, strontium, cobalt and cesium are chemically adsorbed. Moreover, the heat of adsorption of zinc, strontium, cobalt and cesium on cerium(IV) antimonate had been calculated and indicated that cerium(IV) antimonate is of endothermic behaviour towards these ions. Also the distribution coefficients of these ions were determined and it was found that the selectivity in the order: Eu3+ >Sr2+ > Cs+>Na+

  5. A contribution to the radiologic findings in cerium pneumoconiosis

    International Nuclear Information System (INIS)

    Report on a 69 year old man, who had been employed as photographer in the printing industry and who had been exposed to Cerium for 40 years. The chest X-ray which was performed 9 years after the end of the exposure displayes striate densities of the lungs, which must be considered as a late stage of Cerium-pneumoconiosis. The changes which were found fulfill the code 't 1/0 RO, RM, RU, LO, LM, LU, p 0/1 RO, RM, LO, LM, em, tbu' according to the 'ILO U/C 1971 classification of pneumoconiosis'. The diagnosis could be substantiated by measureing Cerium in the lung parenchyma qualitatively and quantitatively using neutrone activating analysis. The radiolgic findings of the Cerium pneumoconiosis are discussed. (orig.)

  6. Cerium intermetallics CeTX. Review III

    International Nuclear Information System (INIS)

    The structure-property relationships of CeTX intermetallics with structures other than the ZrNiAl and TiNiSi type are systematically reviewed. These CeTX phases form with electron-poor and electron-rich transition metals (T) and X = Mg, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, and Bi. The review focusses on the crystal chemistry, the chemical bonding peculiarities, and the magnetic and transport properties. Furthermore 119Sn Moessbauer spectroscopic data, high-pressure studies, hydrogenation reactions and the formation of solid solutions are reviewed. This paper is the third of a series of four reviews on equiatomic intermetallic cerium compound [Part I: R. Poettgen, B. Chevalier, Z. Naturforsch. 2015, 70b, 289; Part II: R. Poettgen, B. Chevalier, Z. Naturforsch. 2015, 70b, 695].

  7. Cerium fluoride crystals for calorimetry at LHC

    International Nuclear Information System (INIS)

    High-resolution homogeneous calorimetry is fully justified for part of the physics program at the Large Hadron Collider (LHC). The main design features of proposed CeF3 crystals for calorimetry for LHC are discussed. The severe constraints LHC imposes on detectors make the use of 'classical' crystals impossible. Therefore, a large R and D effort has been undertaken by the 'Crystal Clear' collaboration in order to find new, dense, fast and radiation hard crystals. A good candidate, cerium fluoride, has been identified and studied. It is interesting at this stage to review the specifications of scintillators for LHC and to see how well available data on CeF3 luminescence, decay time, light yield, optical transmission and resistance to radiation meet them. Milestones to reach before starting a large scale crystal production in view of the eventual construction of a calorimeter, are also discussed. (author) 15 refs., 15 figs., 1 tab

  8. Further results on cerium fluoride crystals

    International Nuclear Information System (INIS)

    A systematic investigation of the properties of cerium fluoride monocrystals has been performed by the 'Crystal Clear' collaboration in view of a possible use of such crystals for the construction of high precision electromagnetic calorimeters for the future generation of high luminosity accelerators. A large sample of different crystals grown by several producers has been studied. The spectroscopic characteristics, the transmission, luminescence and excitation spectra and the decay time curves are analysed. The light yield of the different crystals is measured with photomultipliers and Si photodiodes and compared to reference standards like BGO and NaI(Tl). The radiation damage behaviour is then presented for γ and neutron irradiations, at different doses and dose rates, including thermal and optical bleaching. (orig.)

  9. Further results on cerium fluoride crystals

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, S.; Auffray, E.; Aziz, T.; Baccaro, S.; Banerjee, S.; Bareyre, P.; Barone, L.E.; Borgia, B.; Boutet, D.; Burq, J.P.; Chemarin, M.; Chipaux, R.; Dafinei, I.; D' Atanasio, P.; De Notaristefani, F.; Dezillie, B.; Dujardin, C.; Dutta, S.; Faure, J.L.; Fay, J.; Ferrere, D.; Francescangeli, O.; Fuchs, B.A.; Ganguli, S.N.; Gillespie, G.; Goyot, M.; Gupta, S.K.; Gurtu, A.; Heck, J.; Herve, A.; Hillemanns, H.; Holdener, F.; Ille, B.; Joensson, L.; Kierstead, J.; Krenz, W.; Kway, W.; Le Goff, J.M.; Lebeau, M.; Lebrun, P.; Lecoq, P.; Lemoigne, Y.; Loomis, G.; Lubelsmeyer, K.; Madjar, N.; Majni, G.; El Mamouni, H.; Mangla, S.; Mares, J.A.; Martin, J.P.; Mattioli, M.; Mauger, G.J.; Mazumdar, K.; Mengucci, P.; Merlo, J.P.; Moine, B.; Nikl, N.; Pansart, J.P.; Pedrini, C.; Poinsignon, J.; Polak, K.; Raghavan, R.; Rebourgeard, P.; Rinaldi, D.; Rosa, J.; Rosowsky, A.; Sahuc, P.; Samsonov, V.; Sarkar, S.; Schegelski, V.; Schmitz, D.; Schneegans, M.; Seliverstov, D.; Stoll, S.; Sudhakar, K.; Sven; Crystal Clear Collaboration

    1993-08-15

    A systematic investigation of the properties of cerium fluoride monocrystals has been performed by the 'Crystal Clear' collaboration in view of a possible use of such crystals for the construction of high precision electromagnetic calorimeters for the future generation of high luminosity accelerators. A large sample of different crystals grown by several producers has been studied. The spectroscopic characteristics, the transmission, luminescence and excitation spectra and the decay time curves are analysed. The light yield of the different crystals is measured with photomultipliers and Si photodiodes and compared to reference standards like BGO and NaI(Tl). The radiation damage behaviour is then presented for [gamma] and neutron irradiations, at different doses and dose rates, including thermal and optical bleaching. (orig.)

  10. Mechanical and Thermophysical Properties of Cerium Monopnictides

    Science.gov (United States)

    Bhalla, Vyoma; Singh, Devraj; Jain, S. K.

    2016-03-01

    The ultrasonic attenuation due to phonon-phonon interaction, thermoelastic relaxation and dislocation damping mechanisms has been investigated in cerium monopnictides CeX (X: N, P, As, Sb and Bi) for longitudinal and shear waves along {linearity parameters, Zener anisotropy, ultrasonic velocity, ultrasonic Grüneisen parameter, thermal relaxation time, acoustic coupling constants and ultrasonic attenuation. The fracture/toughness ratio is less than 1.75, which shows that the chosen materials are brittle in nature as found for other monopnictides. The drag coefficient acting on the motion of screw and edge dislocations due to shear and compressional phonon viscosities of the lattice have also been evaluated for both the longitudinal and shear waves. The thermoelastic loss and dislocation damping loss are negligible in comparison to loss due to Akhieser damping (phonon-phonon interaction). The obtained results for CeX are in qualitative agreement with other semi-metallic monopnictides.

  11. Cerium intermetallics CeTX. Review III

    Energy Technology Data Exchange (ETDEWEB)

    Poettgen, Rainer; Janka, Oliver [Muenster Univ. (Germany). Inst. fuer Anorganische und Analytische Chemie; Chevalier, Bernard [Bordeaux Univ., Pessac (France). Inst. de Chimie de la Matiere Condensee de Bordeaux

    2016-05-01

    The structure-property relationships of CeTX intermetallics with structures other than the ZrNiAl and TiNiSi type are systematically reviewed. These CeTX phases form with electron-poor and electron-rich transition metals (T) and X = Mg, Zn, Cd, Hg, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, and Bi. The review focusses on the crystal chemistry, the chemical bonding peculiarities, and the magnetic and transport properties. Furthermore {sup 119}Sn Moessbauer spectroscopic data, high-pressure studies, hydrogenation reactions and the formation of solid solutions are reviewed. This paper is the third of a series of four reviews on equiatomic intermetallic cerium compound [Part I: R. Poettgen, B. Chevalier, Z. Naturforsch. 2015, 70b, 289; Part II: R. Poettgen, B. Chevalier, Z. Naturforsch. 2015, 70b, 695].

  12. Decomposition processes and structural transformations of cerium propionate into nanocrystalline ceria at different oxygen partial pressures

    International Nuclear Information System (INIS)

    The structural transformations that occur when thermal treatments turn cerium propionate into nanocrystalline ceria have been analysed with thermoanalytical techniques (TG, DTA and MS) and with structural and magnetic characterization (HRTEM, SQUID and XRD) of the final and intermediate products. Attention has been paid to what occurs during the decomposition of propionate and how the process is affected by the furnace atmosphere (oxidizing or inert). In an oxidizing atmosphere, the decomposition of cerium propionate is triggered by the oxidation of Ce3+ to Ce4+. This reaction entails the loss of large unoxidized propionate fragments of the propionate ligands. As decomposition proceeds, the carbonaceous residue makes the oxygen transport inside the material more difficult and decomposition becomes diffusion limited. At this point, extensive oxidation of the residue begins until it is completely removed. Crystallization of CeO2 occurs simultaneously with decomposition. In these conditions, crystalline nanoparticles (diameter of 3–5 nm) can be obtained at a temperature as low as 300 °C. In an inert atmosphere, decomposition occurs in three steps. During the first step, one of the three propionate ligands is lost, with little oxidation of Ce3+, and is substituted by a hydroxyl group. The second step entails the loss of the remaining ligands with a substantial oxidation of Ce3+ to Ce4+. After this step, the intermediate product is, proposed as, a mixture of amorphous Ce(OH)3 and Ce(OH)4. Finally, the third step leads to conversion of the Ce hydroxide into crystalline CeO2. In an inert atmosphere, the process is less reproducible than in air and a carbonaceous residue remains in the product.

  13. New insights on the thermal decomposition of lanthanide(III) and actinide(III) oxalates: from neodymium and cerium to plutonium

    OpenAIRE

    De Almeida, Lucie; Grandjean, Stéphane; Vigier, Nicolas; Patisson, Fabrice

    2012-01-01

    Lanthanides are often used as surrogates to study the properties of actinide compounds. Their behaviour is considered to be quite similar as they both possess f valence electrons and are close in size and chemical properties. This study examines the potential of using two lanthanides (neodymium and cerium) as surrogates for plutonium during the thermal decomposition of isomorphic oxalate compounds, in the trivalent oxidation state, into oxides. Thus, the thermal decomposition of neodymium, ce...

  14. Panthenol-stabilized cerium dioxide nanoparticles for cosmeceutic formulations against ROS-induced and UV-induced damage.

    Science.gov (United States)

    Zholobak, N M; Shcherbakov, A B; Bogorad-Kobelska, A S; Ivanova, O S; Baranchikov, A Ye; Spivak, N Ya; Ivanov, V K

    2014-01-01

    A method of panthenol-stabilized cerium dioxide nanoparticles synthesis was developed and their effect on the survival rate of human epidermoid cancer cells HEp-2 and diploid epithelial swine testicular cell line (ST-cells) under oxidative stress conditions induced by hydrogen peroxide introduction and UV irradiation was studied. The results obtained indicate that the use of panthenol as a stabilizer supposedly provides a substantial increase in the efficiency of protection. The degree of protection is determined by panthenol-to-ceria molar ratio. The combination of panthenol and nano-ceria protects biological objects under study from reactive oxygen species (ROS) and UV-irradiation more effectively than individual panthenol or ceria. The protective action of panthenol-stabilized cerium dioxide nanoparticles depends strongly on their composition and the means of their application. PMID:24300997

  15. 铝基二氧化铅-碳化钨-氧化铈复合电极的电化学性能%Electrochemical performance of aluminum-based lead dioxide-tungsten carbide-cerium(Ⅳ) oxide composite electrode

    Institute of Scientific and Technical Information of China (English)

    王淑雪; 廖登辉

    2013-01-01

    A PbO2-WC-CeO2 composite electrode was prepared on aluminum substrate by composite electrodeposition. The process flow mainly includes degreasing, alkaline etching, pickling, zinc immersing for two times, flash nickel plating, lead plating, anodic oxidation, and composite electroplating. The corrosion resistance, energy-saving ability, and catalytic activity of the novel PbO2-WC-CeO2 composite electrode and traditional Pb-Ag(0.75) alloy electrode were compared by measuring and analyzing the Tafel curves, oxygen evolution curves, cell voltage, exchange current density, and accelerated corrosion test results in electrolytic zinc solution consisting of ZnSO4-7H2O 250-300 g/L, Na2SO4 250 g/L, and H3BO3 15-20 g/L. It is confirmed on a laboratory level that the corrosion resistance, energy saving performance, and catalytic activity of the novel Al-based PbO2-WC-CeO2 composite electrode are greatly improved as compared with the traditional Pb-Ag(0.75) alloy electrode.%采用复合电沉积法制备了铝基PbO2-WC-CeO2复合电极材料,其工艺流程主要包括除油、酸浸、碱浸、两次浸锌、闪镀镍、镀铅、阳极氧化和复合电镀.通过测定和分析电极在电解锌溶液(ZnSO4·7H2O 250~300 g/L,Na2SO4 250 g/L,H3BO3 15~20 g/L)中的Tafel曲线、析氧曲线、槽电压、交换电流密度和强效腐蚀试验等比较了新型PbO2-WC-CeO2复合电极与传统Pb-Ag(0.75)合金电极的耐腐蚀性能、节能性能和催化活性.从实验室水平证明了相对于传统Pb-Ag(0.75)合金电极,新型铝基PbO2-WC-CeO2电极在耐腐蚀性、节能和催化活性方面均有很大改善.

  16. Catalytic wet peroxidation of pyridine bearing wastewater by cerium supported SBA-15

    Energy Technology Data Exchange (ETDEWEB)

    Subbaramaiah, V. [Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee 247667 Uttarakhand (India); Srivastava, Vimal Chandra, E-mail: vimalcsr@yahoo.co.in [Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee 247667 Uttarakhand (India); Mall, Indra Deo [Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee 247667 Uttarakhand (India)

    2013-03-15

    Highlights: ► Cerium supported SBA-15 (Ce/SBA-15) synthesized by two-step synthesis. ► Characterization of Ce/SBA-15 by FTIR, XRD and BET surface area. ► Catalytic peroxidation of pyridine by Ce/SBA-15. ► Optimization of parameters like catalyst dose, H{sub 2}O{sub 2} dose, initial concentration and temperature. ► Catalyst reusability and leaching study performed. -- Abstract: Cerium supported SBA-15 (Ce/SBA-15) was synthesized by two-step synthesis method in acidic medium. It was further characterized by various characterization techniques such as X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy and N{sub 2} adsorption–desorption pore size distribution analysis. The Ce/SBA-15 showed highly ordered meso-structure with pore diameter ≈ 70–100 A and pore volume ≈ 0.025 cm{sup 3}/g. Ce/SBA-15 was further evaluated as a catalyst for the oxidation of highly toxic and non-biodegradable material, pyridine, by catalytic wet-peroxidation method. The effects of various operating parameters such as catalyst dose (0.5–6 g/l), stoichiometric ratio of H{sub 2}O{sub 2}/pyridine (1–6), initial pyridine concentration (50–800 mg/l) and temperature (313–358 K) have been evaluated and optimized. Ce/SBA-15 showed stable performance during reuse for six cycles with negligible cerium leaching. Kinetic and thermodynamic parameters and operation cost have also been determined.

  17. Inhibition of pH fronts in corrosion cells due to the formation of cerium hydroxide

    NARCIS (Netherlands)

    Soestbergen, M. van; Erich, S.J.F.; Huinink, H.P.; Adan, O.C.G.

    2013-01-01

    The effect of cerium-based corrosion inhibitors on the pH front between the alkaline cathode and acidic anode in corrosion cells has been studied. The cerium component of these inhibitors can affect the pH front since it precipitates in an alkaline environment as cerium hydroxide, which is important

  18. Electrodeposited cerium film as chromate replacement for tinplate

    International Nuclear Information System (INIS)

    The cerium film was prepared on tinplate by electrodeposition method. Sulfide-stain resistance of the Ce-passivated, unpassivated and Cr-passivated tinplates was evaluated using a cysteine tarnish test. Corrosion behavior of these tinplates in contact with 3.5% NaCl solution and 0.1 M citric-citrate buffer solution was investigated using Tafel measurement and electrochemical impedance spectroscopy measurement, respectively. The adhesion of epoxyphenolic lacquer to the Ce-passivated tinplate was checked using a cross hatch cutter. The morphology, composition and thickness of the cerium film were studied by atomic force microscopy, X-ray photoelectron spectroscopy and X-ray fluorescence spectrometry. According to the results, the Ce-passivated tinplate shows the best sulfide-stain resistance and the best corrosion protection property compared with the unpassivated and Cr-passivated tinplates. The adhesion of epoxyphenolic lacquer to the Ce-passivated tinplate is good. The cerium film is composed of the closely packed particles of about 50-200 nm in diameter. The film mainly consists of cerium and oxygen, which mainly exist as CeO2, Ce2O3 and their hydrates such as Ce(OH)4, Ce(OH)3. The total cerium amount of the film is about 0.110 g/m2

  19. Characterization of cerium fluoride nanocomposite scintillators

    Energy Technology Data Exchange (ETDEWEB)

    Stange, Sy [Los Alamos National Laboratory; Esch, Ernst I [Los Alamos National Laboratory; Brown, Leif O [Los Alamos National Laboratory; Couture, Aaron J [Los Alamos National Laboratory; Mckigney, Edward A [Los Alamos National Laboratory; Muenchausen, Ross E [Los Alamos National Laboratory; Del Sesto, Rico E [Los Alamos National Laboratory; Gilbertson, Robert D [Los Alamos National Laboratory; Mccleskey, T Mark [Los Alamos National Laboratory; Reifarth, Rene [Los Alamos National Laboratory

    2009-01-01

    Measurement of the neutron capture cross-sections of a number of short-lived isotopes would advance both pure and applied scientific research. These cross-sections are needed for calculation of criticality and waste production estimates for the Advanced Fuel Cycle Initiative, for analysis of data from nuclear weapons tests, and to improve understanding of nucleosynthesis. However, measurement of these cross-sections would require a detector with a faster signal decay time than those used in existing neutron capture experiments. Crystals of faster detector materials are not available in sufficient sizes and quantities to supply these large-scale experiments. Instead, we propose to use nanocomposite detectors, consisting of nanoscale particles of a scintillating material dispersed in a matrix material. We have successfully fabricated cerium fluoride (CeF{sub 3}) nanoparticles and dispersed them in a liquid matrix. We have characterized this scintillator and have measured its response to neutron capture. Results of the optical, structural, and radiation characterization will be presented.

  20. Characterization of cerium fluoride nanocomposite scintillators

    International Nuclear Information System (INIS)

    Measurement of the neutron capture cross-sections of a number of short-lived isotopes would advance both pure and applied scientific research. These cross-sections are needed for calculation of criticality and waste production estimates for the Advanced Fuel Cycle Initiative, for analysis of data from nuclear weapons tests, and to improve understanding of nucleosynthesis. However, measurement of these cross-sections would require a detector with a faster signal decay time than those used in existing neutron capture experiments. Crystals of faster detector materials are not available in sufficient sizes and quantities to supply these large-scale experiments. Instead, we propose to use nanocomposite detectors, consisting of nanoscale particles of a scintillating material dispersed in a matrix material. We have successfully fabricated cerium fluoride (CeF3) nanoparticles and dispersed them in a liquid matrix. We have characterized this scintillator and have measured its response to neutron capture. Results of the optical, structural, and radiation characterization will be presented.

  1. Stabilized zirconia with cerium and neodymium addition

    International Nuclear Information System (INIS)

    Zr0,9 Ce0,05 Nd0,05 O1,975 system was synthesized with the use of the Pechini method. The polymeric resin was calcined at 350 deg C/3 h and analysed by FTIR that show bands relative to organic. Radicals esther type. The TGA curve indicated the polymeric decomposition occurring from 30 deg C to 740 deg C. DTA analysis show a exothermic peak in 100 deg C due to loss of water of material. From 500 deg C to 800 deg C was observed a intense peak due to polymer decomposition and the zirconia crystallization. The calcined powder from 350 deg C/3 h e 30 min to 900 deg/3 h were analysed by XRD that show the crystalline phase formation with the increase of temperature. The X-ray diffraction pattern show the presence of two phases, such as tetragonal and cubic of zirconia demonstrating that neodymium and cerium additions led to zirconia stabilization. (author)

  2. Cerium Dioxide Thin Films Using Spin Coating

    Directory of Open Access Journals (Sweden)

    D. Channei

    2013-01-01

    Full Text Available Cerium dioxide (CeO2 thin films with varying Ce concentrations (0.1 to 0.9 M, metal basis were deposited on soda-lime-silica glass substrates using spin coating. It was found that all films exhibited the cubic fluorite structure after annealing at 500°C for 5 h. The laser Raman microspectroscopy and GAXRD analyses revealed that increasing concentrations of Ce resulted in an increase in the degree of crystallinity. FIB and FESEM images confirmed the laser Raman and GAXRD analyses results owing to the predicted increase in film thickness with increasing Ce concentration. However, porosity and shrinkage (drying cracking of the films also increased significantly with increasing Ce concentrations. UV-VIS spectrophotometry data showed that the transmission of the films decreased with increasing Ce concentrations due to the increasing crack formation. Furthermore, a red shift was observed with increasing Ce concentrations, which resulted in a decrease in the optical indirect band gap.

  3. Cerium luminescence in borate glass and effect of aluminium on blue green emission of cerium ions

    International Nuclear Information System (INIS)

    CeO2 doped lead borate (CE) and lead alumino borate (CEA) glasses are prepared by melt quench method at high temperature. The main luminescence band of 5d–4f transition of Ce3+ ions with maxima at around 489 nm of Ce3+ ions in these glasses has been observed, along with red shift and larger stokes shift, which shows that the covalency of the rare earth to oxygen bond increases with the increase in CeO2 content at the expense of Al2O3. Shifting of UV absorption edge towards longer wavelength and a decrease in band gap with increase in CeO2 concentration in both the glass systems has been observed. Moreover densification and stabilization of glass network has been observed which is due to conversion of BO3 units to more compact and stable BO4 units. This covalency effect and the formation of BO4 groups with addition of CeO2 and incorporation of Al2O3 content are responsible for clear effect on luminescence of the present glass system. Moreover the optical basicity values were theoretically determined along with density and molar volume. -- Highlights: • Aluminium incorporation assists in dispersing the clusters of cerium ions and thus enhancing luminescence response. • Decrease of optical band gap energy with an increase of cerium concentration shows the semiconducting behavior. • Larger stokes shift shows that the covalency of rare earth to oxygen bond increases with increase in CeO2

  4. Preparation and electrochemical study of cerium-silica sol-gel thin films

    International Nuclear Information System (INIS)

    Design and development of suitable multilayered systems for delaying corrosion advance in metals requires that both the alteration mechanisms of the metal and the behaviour and properties of the protective coatings be known. Coatings prepared by the sol-gel method provide a good approach as protective layers on metallic surfaces. This kind of coatings can be prepared from pure chemical reagents at room temperature and atmospheric pressure, with compositions in a very wide range of environmentally non-aggressive precursors. Sol-gel coatings based on siloxane bonded units were prepared starting from an organic-inorganic hybrid system. The precursors were γ-methacryloxypropyltrimethoxysilane (MAP) and tetramethoxysilane (TMOS). Cerium nitrate hexahydrate in three different concentrations was added. Cerium salts may perform a similar protective effect to that carried out by the well-known lead oxides and chromium salts, even though in this case a negative environmental impact is not expected. Application of coatings upon pure zinc substrates and common glass slides were performed by spinning. Coated samples were heat treated at 40 deg. C for 6 days. Optical measurements (UV-Vis absorption and diffuse reflectance spectroscopies) pointed out that the coatings were colourless and transparent, reducing the diffuse reflectance of the metallic surface up to ∼60%. Optical and scanning electron microscopies (SEM) allowed observation of the texture and microstructure of the coated samples, both before and after the corrosion tests were carried out. Likewise, the remaining sols were kept to gelify at 60 deg. C for 4 days and then powdered to obtain suitable samples for analysing them by other characterisation techniques (Fourier transformed infrared, FTIR and differential thermal analysis, DTA). Electrochemical measurements were performed by impedance spectroscopy. This technique was used to clarify the anticorrosive protection role of cerium ions incorporated into the hybrid

  5. Cerium uptake by zeolite A synthesized from natural clinoptilolite tuffs

    International Nuclear Information System (INIS)

    Natural clinoptilolite tuffs from the Semnan region in Iran was used for the synthesis of zeolite A. The tuffs and synthesized zeolites were characterized by XRD and XRF. The sorption behavior of the synthesized zeolite toward cerium was studied. Using the Lagergren's equation, the absorption constant was calculated. The measured distribution coefficient values (Kd) indicated that cerium uptake is higher in lower initial concentrations, higher temperature and higher pH values. Thermodynamic parameters of the exchange were calculated through construction of ion-exchange isotherms at three temperatures of 298, 323 and 343 K. The dynamic absorption of cerium was also studied by passing the solution through a column in the presence and absence of sodium ions. (author)

  6. Direct fabrication of cerium oxide hollow nanofibers by electrospinning

    Institute of Scientific and Technical Information of China (English)

    CUI Qizheng; DONG Xiangting; WANG Jinxian; LI Mei

    2008-01-01

    Electrospinning technique was used to fabricate PVP/Ce(NO3)3 composite mierofibers. Different morphological CeO2 nanofibers were obtained by calcination of the PVP/Ce(NO3)3 composite microfibers and were characterized by scanning electron microscopy (SEM),Transmission electron microscopy (TEM), X-ray diffraction (XRD), thermal gravimetric and differential thermal analysis (TG-DTA), and (FHR). SEM micrographs indicated that the surface of the composite fibers was smooth and became coarse with the increase of calcination temperatures. The diameters of CeO2 hollow nanofibers (300 nm at 600 ℃ and 600 nm at 800 ℃) were smaller than those of PVP/Ce(NO3)3 composite fibers (1-2 μm). CeO2 hollow nanofibers were obtained at 600 ℃ and CeO2 hollow and porous nanofibers formed by nanoparti-ties were obtained at 800 ℃. The length of the CeO2 hollow nanofibers was greater than 50 μm. XRD analysis revealed that the composite microfibers were amorphous in structure and CeO2 nanofibers were cubic in structure with space groupO5H-FM3m when calcination tem-peratures were 600-800 ℃. TG-DTA and FTIR revealed that the formation of CeO2 nanofibers was largely influenced by the calcination temperatures. Possible formation mechanism of CeO2 hollow nanofibers was proposed.

  7. Polypyrrole and polyaniline prepared with cerium(IV) sulfate oxidant

    Czech Academy of Sciences Publication Activity Database

    Omastová, M.; Mosnáčková, K.; Trchová, Miroslava; Konyushenko, Elena; Stejskal, Jaroslav; Fedorko, P.; Prokeš, J.

    2010-01-01

    Roč. 160, 7-8 (2010), s. 701-707. ISSN 0379-6779 R&D Projects: GA AV ČR IAA400500905; GA ČR GA203/08/0686 Institutional research plan: CEZ:AV0Z40500505 Keywords : polypyrrole * polypyrrole base * polyaniline Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.871, year: 2010

  8. Heteroepitaxy of Cerium Oxide Thin Films on Cu(111

    Directory of Open Access Journals (Sweden)

    Josef Mysliveček

    2015-09-01

    Full Text Available An important part of fundamental research in catalysis is based on theoretical and modeling foundations which are closely connected with studies of single-crystalline catalyst surfaces. These so-called model catalysts are often prepared in the form of epitaxial thin films, and characterized using advanced material characterization techniques. This concept provides the fundamental understanding and the knowledge base needed to tailor the design of new heterogeneous catalysts with improved catalytic properties. The present contribution is devoted to development of a model catalyst system of CeO2 (ceria on the Cu(111 substrate. We propose ways to experimentally characterize and control important parameters of the model catalyst—the coverage of the ceria layer, the influence of the Cu substrate, and the density of surface defects on ceria, particularly the density of step edges and the density and the ordering of the oxygen vacancies. The large spectrum of controlled parameters makes ceria on Cu(111 an interesting alternative to a more common model system ceria on Ru(0001 that has served numerous catalysis studies, mainly as a support for metal clusters.

  9. Impact of cerium oxide nanoparticles on cilantro ( Coriandrum sativum)

    Science.gov (United States)

    Morales, Maria Isabel

    Studies have shown that plants exposed to ENPs suffer different types of stress. Other studies have revealed that plants can take up and accumulate CeO2 NPs without modification. Thus, these NPs could enter the food chain through edible plants, posing a threat for human health. Cilantro (Coriandrum sativum) is a worldwide culinary and medicinal plant consumed either as a fresh herb or a spice. In this research, cilantro plants were germinated and cultivated for 30 days in organic soil treated with CeO2 NPs at concentrations varying from 0 to 500 mg kg -1. Subsequently, plant organs were analyzed by using spectroscopic techniques and biochemical assays. Results indicate that at 125 mg kg -1, the CeO2 NPs significantly increased the root size compared with the other treatments. The ICP-OES results showed that plants exposed to 500 mg kg-1 had significantly (p ≤ 0.05) more Ce in shoots and roots compared to the other treatments. Results from the biochemical assays showed that at 125 mg kg-1, catalese activity significantly increased in shoots and ascorbate peroxidase in roots (p ≤ 0.05). In addition, the FTIR analyses revealed that at 125 mg kg-1, the CeO2 NPs changed the chemical environment of the carbohydrates within the cilantro shoots, for which changes in the area of the stretching frequencies were observed. Moreover, analyses of antioxidant compounds showed a significant ( p ≤ 0.05) reduction on total phenolic content in shoots of cilantro plants treated with 500 mg CeO2 NPs kg-1 . This suggests that the CeO2 NPs have the potential to diminish the ability of cilantro plants to scavenge reactive oxygen species. The multi-elemental analysis showed that plants treated with CeO2 at the 500 mg kg-1 treatment had a significant ( p ≤ 0.05) reduction in shoots' sulfur, silicon, and zinc accumulation. The results of this research indicate that the CeO2 NPs at 500 mg CeO2 kg-1 concentration cause a reduction in the antioxidant ability and nutritional properties of cilantro plants.

  10. Rheology of stabilized cerium-gadolinium oxide (CGO) colloidal system

    DEFF Research Database (Denmark)

    Marani, Debora; Hjelm, Johan; Wandel, Marie

    performed to study the inorganic loading impact on the suspension rheology. To identify a realistic load limit, the parameter h was proposed. It defines the highest volume fraction to meet the processing requirements. A simple method for its determination was also proposed. The maximum solid volume...

  11. Influence of stoichiometry on electrochromic cerium-titanium oxide compounds

    International Nuclear Information System (INIS)

    CeO2-TiO2 finds use as passive counter-electrode in electrochromic devices. Thin films were produced by de-sputtering in a wide range of compositions. Influence of total pressure and oxygen partial pressure on the optical constants of TiO2 was investigated. Slightly substoichiometric Ti02 films exhibit a red-shift of the bandgap. The Ti02 content in the compound essentially determines the degree of cathodical coloring upon Li+ intercalation [1]. However, pure TiO2 films with comparable visible transmittance in the clear state behave differently during electrochemical cycling depending on oxygen stoichiometry. Films that are deposited at higher total pressure are more oxygen rich and require initial formatting until current voltage cycles become stable. CeO2-Ti02 films of intermediate compositions have the relatively highest charge capacity. Comparison with atomic force microscopy indicates a correlation of small grain size with high charge capacity

  12. Aqueous medium induced optical transitions in cerium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Inerbaev, Talgat M.; Karakoti, Ajay S.; Kuchibhatla, S. V. N. T.; Kumar, Amit; Masunov, Artem E.; Seal, Sudipta

    2015-03-07

    Experimental and theoretical investigations were performed to investigate the effect of water on optical properties of nanoceria as a function of Ce3+ concentration. Theoretical studies based on density functional plane-wave calculations reveal that the indirect optical transitions in bare ceria nanoparticles are red-shifted with an increase in the concentration of Ce3+. However, ceria nanoparticles model with adsorbed water molecules show a blue shift in the indirect optical spectra under identical conditions. Direct optical transitions are almost independent of Ce3+ concentration but show a pronounced blue shift in the aqueous environment relative to the bare nanoparticles. The theoretical study is consistent with our experimental observation in difference of shift behaviour in bare and aqueous suspended ceria nanoparticles. This change from red- to blue-shift in indirect optical transitions is associated with the polarization effect of water molecules on f-electron states.

  13. Rheological analysis of stabilized cerium-gadolinium oxide (CGO) dispersions

    DEFF Research Database (Denmark)

    Marani, Debora; Hjelm, Johan; Wandel, Marie

    2014-01-01

    The objective of the present work is to generate general rheological criteria to investigate high solid loading dispersions suitable for the shaping of homogeneous ceramic bodies. Systematic analysis of the rheological properties of moderately low specific surface area (SSA) Ce0.9Gd0.1O3-δ (CGO10...

  14. Activity and stability enhancement of copper-alumina catalysts using cerium and zinc promoters for the selective production of hydrogen via steam reforming of methanol

    Science.gov (United States)

    Patel, Sanjay; Pant, K. K.

    The catalytic activity and hydrogen selectivity of cerium and zinc promoted copper-alumina catalysts have been investigated for the selective production of hydrogen via steam reforming of methanol (SRM). The SRM was carried out in a fixed bed tubular reactor at atmospheric pressure over a temperature range 200-300 °C. The major reaction products were hydrogen and carbon dioxide with traces of carbon monoxide. Catalysts of varying compositions were prepared by the wet impregnation method and characterized by atomic absorption spectroscopy (AAS), BET surface area, pore volume, pore size, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and thermogravimetry analysis (TGA). Results revealed that the methanol conversion, hydrogen selectivity and carbon monoxide formation varied with the type of promoter and content of copper in the catalyst. Cerium promoted Cu-Zn-Ce-Al-oxide catalysts improved the activity and hydrogen selectivity greatly and also kept the CO formation very low. Using cerium the SRM could be carried out at lower temperature with high methanol conversion, results in suppression of methanol decomposition and reverse water gas shift reactions eventually end-up with the low carbon monoxide and hydrogen rich product stream. Cerium also stabilizes the copper-alumina catalysts effectively that was confirmed by deactivation studies in which cerium promoted Cu-Zn-Ce-Al-oxide catalysts gave the consistent performance for a long run-time compared to catalysts containing only zinc promoter. The optimum operating conditions for SRM have been investigated by detailed study of effects of reaction temperature, contact time and steam to methanol molar ratio on methanol conversion, hydrogen selectivity and CO formation. Reaction pathway has been proposed for the SRM based on results obtained.

  15. Photo-assisted reduction in nanostructured cerium-based coatings

    International Nuclear Information System (INIS)

    Nanostructured cerium-based coatings on AZ31 Mg alloy substrates exposed to sunlight under ambient conditions had an ∼30% increase in Ce(III) species compared to unexposed coatings as measured by X-ray photoelectron spectroscopy. A decrease in film cracks and shift in bandgap from 2.5 eV to 2.7 eV were also measured. Visible changes in color, from yellow to translucent, with exposure were also observed and suggest that cerium-based coatings are reduced by light exposure in humid environments

  16. Membrane assisted liquid-liquid extraction of cerium

    International Nuclear Information System (INIS)

    Membrane assisted liquid-liquid extraction of cerium was investigated, with emphasis placed on the study of the reaction chemistry and the kinetics of non-dispersive solvent extraction and stripping with microporous membranes. A bulk liquid membrane process was developed for the purification of cerium(IV) from sulfate solutions containing other rare earth elements. The cerium process was studied in both a flat sheet contained liquid membrane configuration and with hollow fibre contactors. Di-2-ethylhexyl phosphoric acid (DEHPA) was identified as a suitable extractant for cerium(IV) from sulfuric acid solution, with due consideration of factors such as extraction ability, resistance to degradation, solvent selectivity and potential for sulfate transfer into a strip solution. A detailed study of the extraction of cerium(IV) with DEHPA defined the extraction reaction chemistry. The Ce/DEHPA/sulfate system was also investigated with a flat sheet bulk liquid membrane configuration, using both sulfuric and hydrochloric acid as receiver solutions. These tests identified that hydrophobic membranes provide better mass transfer for extraction and hydrophilic membranes are better for stripping. The presence of an impurity, mono 2-ethylhexyl phosphoric acid (MEHPA), was found to have a dramatic accelerating effect on the rate of the chemical extraction reaction. This was attributed to its higher interfacial activity and population compared to DEHPA, and the fact that MEHPA was also found to be an active carrier for cerium(IV). The mass transfer rate of membrane assisted extraction and stripping of cerium, using hydrophobic and hydrophilic microporous membranes, respectively, was investigated using a modified Lewis-type cell. It was quantitatively demonstrated that the extraction process was mainly controlled by membrane diffusion and the stripping process was controlled by the chemical reaction rate, with membrane diffusion becoming important at low distribution coefficients

  17. Electrical, thermal and infrared studies of cerium(III) orthovanadate

    International Nuclear Information System (INIS)

    Cerium(III) orthovandate with a small deviation from stoichiometric composition is a p-type semiconductor between 30 and 800 degC. The electrical conduction in cerium(III) orthovanadate is due to thermally activated hopping of holes on equivalent Ce3+ -Ce4+ lattice sites. The DTA result of CeVO4 indicated a possible phase transition at about 70 degC. The IR spectrum of the sample showed bands at 865 and 810 cm-1, typical of VO4 group of orthovanadates. (author). 10 refs., 3 figs

  18. Stepwise hydrochloric acid extraction of monazite hydroxides for the recovery of cerium lean rare earths, cerium, uranium and thorium

    International Nuclear Information System (INIS)

    Monazite sand is normally processed by the caustic soda route to produce mixed rare earth chloride, thorium hydroxide and trisodium phosphate. Bulk of the mixed rare earth chloride is used for the preparation of FC catalysts. Recently some of the catalyst producers have shown preference to cerium depleted (lanthanum enriched) rare earth chloride rather than the natural rare earth chloride obtained from monazite. Therefore, a process for producing cerium depleted rare earth chloride, cerium, thorium and uranium from rare earth + thorium hydroxide obtained by treating monazite, based on stepwise hydrochloric acid extraction, was developed in the authors laboratory. The process involves drying of the mixed rare earth-thorium hydroxide cake obtained by monazite-caustic soda process followed by stepwise extraction of the dried cake with hydrochloric acid under specified conditions

  19. Pure cerium dioxide preparation for use as spectrochemical standard and analysed by inductively coupled plasma mass spectrometry (SF ICP-MS)

    International Nuclear Information System (INIS)

    For several years, IPEN/CNEN-SP has been working in the separation of the Rare Earth (RE) elements. A simple and economic procedure for the purification of technical grade cerium concentrate is described. The highly pure cerium dioxide is designed to be used as spectrochemical standard. It is obtained by association of the fractional precipitation technique, in the system RECl3/NH4OH/ Air/H2O2, to enrich the cerium up to 90% and then it is upgraded by ion exchange technique to 99.99% CeO2. The quality control warranty was accomplished by inductively coupled mass spectrometry (ICP-MS) and neutron activation analysis. The collected values for the accompanying Rare Earth elements in a CeO2 sample are the following (ppm): La(36), Pr(19), Nd(161), Sm(11), Eu(5.3), Gd(113), Tb(89), Dy(2), Ho(0.05), Er(1), Tm(<0.05), Yb(11), Lu(19) and Y(2.1), respectively. The purity of this cerium oxide is comparable to the international spectrographic standards. (author)

  20. Nanoparticulate cerium dioxide and cerium dioxide-titanium dioxide composite thin films on glass by aerosol assisted chemical vapour deposition

    International Nuclear Information System (INIS)

    Two series of composite thin films were deposited on glass by aerosol assisted chemical vapour deposition (AACVD)-nanoparticulate cerium dioxide and nanoparticulate cerium dioxide embedded in a titanium dioxide matrix. The films were analysed by a range of techniques including UV-visible absorption spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive analysis by X-rays. The AACVD prepared films showed the functional properties of photocatalysis and super-hydrophilicity. The CeO2 nanoparticle thin films displaying photocatalysis and photo-induced hydrophilicity almost comparable to that of anatase titania.

  1. Electrorheological Effects of Cerium-Doped TiO2

    Institute of Scientific and Technical Information of China (English)

    尹剑波; 赵晓鹏

    2001-01-01

    It is found that the doping of cerium ion into anatase TiO2 can improve the electrorheological (ER) effects of TiO2 and broaden the operational temperature range. Especially, the substitution of 7-11 mol% of the cerium dopant for Ti can obtain a relatively high shear stress, t-7.4kPa (at 4kV/mm), which is ten times larger than that of pure TiO2 ER fluid. Also, the typical Ce-doped TiO2 ER fluid shows the highest shear stress at 80℃, but 40℃ for pure TiO2 ER fluid. The dielectric loss and dielectric constant at a low frequency of TiO2 is improved by the doping of cerium, and the temperature dependence of the dielectric properties shows an obvious differnce between pure and doped TiO2 ER fluids. These can well explain the ER behaviour of doped TiO2. Furthermore, the change of rheological and dielectric properties is discussed on the basis of the lattice distortion and defects in TiO2 arising from the doping of cerium.

  2. Enhanced K-edge angiography utilizing cerium-target diode

    International Nuclear Information System (INIS)

    The cerium-target x-ray tube is useful in order to perform cone-beam K-edge angiography because Kα rays from the cerium target are absorbed effectively by iodine-based contrast mediums. The x-ray generator consists of a main controller, an x-ray tube unit with a high-voltage circuit and an insulation transformer, and a personal computer. The tube is a glass-enclosed diode with a cerium target and a 0.5-mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively, and the focal-spot sizes were approximately 1 x 1 mm. Sharp cerium Kα lines were left using a barium sulfate filter, and the x-ray intensity was 16.8 μGy/s at 1.0 m from the source with a tube voltage of 60 kV and a current of 0.40 mA. Angiography was performed with an x-ray film (Fuji IX 100) using iodine-based microspheres 15 μm in diameter. In angiography of non-living animals, we observed fine blood vessels of 100 μm or less with high contrasts. (author)

  3. Electrodeposition of cerium from aqueous cerous chloride solutions

    International Nuclear Information System (INIS)

    Cerium was plated as a grey, metallic, adherent deposit from aqueous cerous chloride baths containing certain organic addition agents. The cathodic current efficiency was determined for each case. Chemical analysis indicates that the purity of the metal is better than 99.0 per cent. (author). 7 refs

  4. 40 CFR 721.8657 - Cerium, hydroxy oleate propionate complexes.

    Science.gov (United States)

    2010-07-01

    ... complexes. 721.8657 Section 721.8657 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.8657 Cerium, hydroxy oleate propionate complexes. (a) Chemical substance..., hydroxy oleate propionate complexes (PMN P-99-0026) is subject to reporting under this section for...

  5. Thermoluminescence studies in cerium doped NaCl crystals

    International Nuclear Information System (INIS)

    Cerium is known to enter substitutionally in trivalent state when doped in alkali halides. Cerium doped NaCl crystals exhibit greatly enhanced thermoluminescence output upon X-irradiation at RT, the intensity of emission being about 10 times that in undoped crystals for similar dosage of irradiation. The cerium doped crystals give upon X-irradiation a very intense glow peak at 145degC with shoulders at 120degC and 210degC. Upon partially bleaching the crystal with F-light, the peak at 120degC becomes prominent probably due to faster bleaching of the glow at 145degC. From further optical bleaching studies, it is concluded that the glow peak at around 120degC is due to cerium centres in the irradiated crystal and the 145degC peak due to F centres. This F centre emission occurs at lower temperature, compared to that in the undoped crystals where it occurs at around 180degC. The spectral emission in the Ce doped crystals is in the blue-green region as compared to the emission in the blue region in undoped crystals. The trap depth and other parameters of the 120degC glow peak are estimated by the total curve fitting method. (author)

  6. Competition between magnetic order and Kondo effect in cerium compounds

    International Nuclear Information System (INIS)

    We present a mean-field analysis of the competition between magnetic order and Kondo effect in a Kondo-lattice model usually employed to discuss properties of certain cerium compounds. A phase diagram is obtained showing an antiferromagnetic phase and a Kondo-compensated regime, in agreement with the Doniach diagram. A general discussion of the mean-field approach is also presented

  7. Characterization of the alumina film with cerium doped on the iron-aluminide diffusion coating

    Energy Technology Data Exchange (ETDEWEB)

    Zhan, Q., E-mail: zhanqin1983@163.com; Yang, H.G.; Zhao, W.W.; Yuan, X.M.; Hu, Y.

    2013-11-15

    An iron-aluminide layer with a thin alumina film on the top as a composite tritium permeation barrier (TPB) coating was characterized under different oxidation conditions. The TPB coating was prepared initially on a China Low Activation Ferritic-Martensitic (CLAM) steel by a pack cementation aluminizing process and then an alumina film was formed on the surface of this iron-aluminide diffusion layer by an oxidizing process. To modify the properties of the FeAl/Al{sub 2}O{sub 3} composite TPB coatings, the rare earth element (cerium) was introduced as a dopant while oxidizing. Characterization showed that a continuous oxide scale with a thickness of about 300–400 nm was formed on the FeAl diffusion layer. The film was mainly composed of Al{sub 2}O{sub 3} doped with a little CeO{sub 2}. In addition, the concentration of α-Al{sub 2}O{sub 3} increased with elevated temperature while oxidizing. The phase transformation behavior of alumina scale on the surface of an iron-aluminide layer was studied in this paper.

  8. Preparation, Characterization and Antibacterial Property of Cerium Substituted Hydroxyapatite Nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Lin Yingguang; Yang Zhuoru; Cheng Jiang

    2007-01-01

    Nanoparticles of hydroxyapatite (HAP) and cerium substituted hydroxyapatite (CeHAP) with the atomic ratio of Ce/[Ca+Ce] (xCe) from 0 to 0.2 were prepared by sol-gel-supercritical fluid drying (SCFD) method. The nanoparticles were characterized by TEM, XRD, and FT-IR, and the effects of cerium on crystal structure, crystallinity, and particle shape were discussed. With the tests of bacterial inhibition zone and antibacterial ratio, the antibacterial property of HAP and CeHAP nanoparticles on Escherichia coli, Staphylococcus aureus, Lactobacillus were researched. Results showed that the nanoparticles of HAP and CeHAP could be made by sol-gel-SCFD, cerium could partially substitute for calcium and enter the structure of HAP. After substitution, the crystallinity, the IR wavenumbers of bonds in CeHAP decreased gradually with increase of cerium substitution, and the morphology of the nanoparticles changed from the short rod-shaped HAP to the needle-shaped CeHAP. The nanoparticles of HAP and CeHAP with xCe below 0.08 had antibacterial property only forcibly contacting with the test bacteria at the test concentration of 0.1 g·ml-1, however, the CeHAP nanoparticles had antibacterial ability at that concentration no matter statically or dynamically contacting with the test bacteria when xCe was above 0.08, and the antibacterial ability gets better with the increase of xCe, indicating that the antibacterial property was improved after calcium was partially substituted by cerium. The improved antibacterial effects of CeHAP nanoparticle on Lactobacillus showed its potential ability to anticaries.

  9. Study of corrosion inhibition of coupled Al2Cu–Al and Al3Fe–Al by cerium cinnamate using scanning vibrating electrode technique and scanning ion-selective electrode technique

    International Nuclear Information System (INIS)

    Highlights: • The corrosion inhibition of coupled Al2Cu–Al and Al3Fe–Al by cerium cinnamate was studied. • SVET and SIET were used to study the distribution of current densities and pH. • The corrosion inhibition mechanisms were analyzed. - Abstract: The galvanic corrosion of the coupled Al2Cu and Al as well as Al3Fe and Al in 0.005 M NaCl in and without the presence of cerium cinnamate was studied. Scanning vibrating electrode technique and scanning ion-selective electrode technique were used to measure the distribution of current densities and pH. The results indicate that cerium cinnamate played inhibiting effect on the coupling corrosion of Al2Cu–Al and Al3Fe–Al. For Al2Cu–Al, the inhibition was mainly influenced by the production of cerium oxide/hydroxide on Al2Cu surface. However, for Al3Fe–Al, the inhibition was mainly influenced by the adsorbed cerium cinnamate on the Al3Fe surface

  10. Perovskite catalysts for oxidative coupling

    Science.gov (United States)

    Campbell, Kenneth D.

    1991-01-01

    Perovskites of the structure A.sub.2 B.sub.2 C.sub.3 O.sub.10 are useful as catalysts for the oxidative coupling of lower alkane to heavier hydrocarbons. A is alkali metal; B is lanthanide or lanthanum, cerium, neodymium, samarium, praseodymium, gadolinium or dysprosium; and C is titanium.

  11. Ruthenium carbonyl catalyst supported on ceric oxide for preparation of olefins from synthesis gas

    Science.gov (United States)

    Pierantozzi, Ronald

    1985-01-01

    A catalyst comprising a ruthenium carbonyl compound deposited on a cerium oxide-containing support material provides for the selective synthesis of low molecular weight olefinic hydrocarbons from mixtures of hydrogen and carbon monoxide.

  12. Steric and electronic effects of 1,3-disubstituted cyclopentadienyl ligands on metallocene derivatives of Cerium, Titanium, Manganese, and Iron

    Energy Technology Data Exchange (ETDEWEB)

    Sofield, C.D.

    2000-05-19

    Sterically demanding 1,3-disubstituted cyclopentadienyl ligands were used to modify the physical properties of the corresponding metallocenes. Sterically demanding ligands provided kinetic stabilization for trivalent cerium compounds. Tris(di-t-butylcyclopentadienyl)cerium was prepared and anion competition between halides and cyclopentadienyl groups which had complicated synthesis of the tris(cyclopentadienyl)compound was qualitatively examined. Bis(di-t-butylcyclopentadienyl)cerium methyl was prepared and its rate of decomposition, by ligand redistribution, to tris(di-t-butylcyclopentadienyl)cerium was shown to be slower than the corresponding rate for less sterically demanding ligands. Asymmetrically substituted ligands provided a symmetry label for examination of chemical exchange processes. Tris[trimethylsilyl(t-butyl)cyclopentadienyl]cerium was prepared and the rate of interconversion between the C1 and C3 isomers was examined. The enthalpy difference between the two distereomers is 7.0 kJ/mol. The sterically demanding cyclopentadienyl ligands ansa-di-t-butylcyclopentadiene (Me2Si[(Me3C)2C5H3]2), ansa-bis(trimethylsilyl)cyclopentadiene (Me2Si[(Me3Si)2C5H3]2) and tetra-t-butylfulvalene and metallocene derivatives of the ligands were prepared and their structures were examined by single crystal X-ray crystallography. The effect that substituents on the cyclopentadienyl ring have on the pi-electron system of the ligand was examined through interaction between ligand and metal orbitals. A series of 1,3-disubstituted manganocenes was prepared and their electronic states were determined by solid-state magnetic susceptibility, electron paramagnetic resonance, X-ray crystallography, and variable temperature UV-vis spectroscopy. Spin-equilibria in [(Me3C)2C5H3]2Mn and [(Me3C)(Me3Si)C5H3]2Mn were examined and indicate an enthalpy difference of 15 kJ/mol between the high-spin and low-spin forms. Cyclopentadienyl groups resistant to intramolecular oxidative addition

  13. Determination of silver and cerium in the liver and the kidney from a severely burned infant treated with silver sulfadiazine and cerium nitrate

    International Nuclear Information System (INIS)

    Silver and cerium in the liver and the kidney from severely burned infant were analyzed by neutron activation method. The patient was treated topically with cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for 3 months. Then, the treatment with these drugs was stopped because o f abdominal distention. The patient died 1 month after the cessation of the treatment with these drugs. The tissue specimens, blank liver sample and reference standards were irradiated with TRIGA MARK II Reactor of Rikkyo University. About 1 month after the irradiation, the activities were measured with a Ge(Li) detector coupled to a 4096 channel pulse height analyzer. A large amount of silver was detected both in the liver and in the kidney and a trace of cerium only in the liver. A considerable amount of silver was detected in the liver and its quantity was about 1600 times more than that of normal livers reported by Hamilton, Minski and Cleary (1972 -- 73). Neither silver nor cerium were detected in the blank liver. These results suggest that prolonged topical chemotherapy of cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for the extensive burn injuries causes considerable absorption of silver and cerium into the liver and the kidney. (author)

  14. [Determination of silver and cerium in the liver and the kidney from a severely burned infant treated with silver sulfadiazine and cerium nitrate].

    Science.gov (United States)

    Hirakawa, K

    1983-02-01

    Silver and cerium in the liver and the kidney from severely burned infant were analyzed by neutron activation method. The patient was treated topically with cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for 3 months. Then, the treatment with these drugs was stopped because of abdominal distention. The patient died 1 month after the cessation of the treatment with these drugs. The tissue specimens, blank liver sample and reference standards were irradiated with TRIGA MARK II Reactor of Rikkyo University. About 1 month after the irradiation, the activities were measured with a Ge(Li) detector coupled to a 4096 channel pulse height analyzer. A large amount of silver was detected both in the liver and in the kidney and a trace of cerium only in the liver. A considerable amount of silver was detected in the liver and its quantity was about 1600 times more than that of normal livers reported by Hamilton, Minski and Cleary (1972-73). Neither silver nor cerium were detected in the blank liver. These results suggest that prolonged topical chemotherapy of cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for the extensive burn injuries causes considerable absorption of silver and cerium into the liver and the kidney. PMID:6867381

  15. Determination of silver and cerium in the liver and the kidney from a severely burned infant treated with silver sulfadiazine and cerium nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Hirakawa, Keiko (Nippon Medical School, Tokyo)

    1983-02-01

    Silver and cerium in the liver and the kidney from severely burned infant were analyzed by neutron activation method. The patient was treated topically with cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for 3 months. Then, the treatment with these drugs was stopped because of abdominal distention. The patient died 1 month after the cessation of the treatment with these drugs. The tissue specimens, blank liver sample and reference standards were irradiated with TRIGA MARK II Reactor of Rikkyo University. About 1 month after the irradiation, the activities were measured with a Ge(Li) detector coupled to a 4096 channel pulse height analyzer. A large amount of silver was detected both in the liver and in the kidney and a trace of cerium only in the liver. A considerable amount of silver was detected in the liver and its quantity was about 1600 times more than that of normal livers reported by Hamilton, Minski and Cleary (1972 -- 73). Neither silver nor cerium were detected in the blank liver. These results suggest that prolonged topical chemotherapy of cerium nitrate/silver sulfadiazine cream and cerium nitrate solution for the extensive burn injuries causes considerable absorption of silver and cerium into the liver and the kidney.

  16. Oxide catalysts for oxidation of xylene

    OpenAIRE

    Kusman Dossumov; Dina Churina; E. Tulibaev

    2013-01-01

    Polioxide granulated catalysts based on transition and rare earth metals for oxidative conversion of xylene by oxygen have been investigated. It was defined the effect of the composition and concentration of the active phase of oxide catalysts: Cu-Mn-Ln; Cu-Mn-Ce and Cu-Mn-Nd on the o-xylene oxidation. It was found that the Cu-Mn-Ce catalyst has the highest activity at the concentrations of metals: copper – 3.0%; manganese – 3.0%; cerium – 1.0%.

  17. Effect of cerium modification on microstructure and properties of hypereutectic high chromium cast iron

    Energy Technology Data Exchange (ETDEWEB)

    Zhi, Xiaohui, E-mail: mkmkzxh@hotmail.com [School of Mechanical Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, Hebei Province (China); Liu, Jinzhi [School of Mechanical Engineering, Shijiazhuang Tiedao University, Shijiazhuang 050043, Hebei Province (China); Xing, Jiandong; Ma, Shengqiang [State Key Laboratory Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi' an Jiaotong University, Xi' an 710049, Shaanxi Province (China)

    2014-05-01

    The effect of cerium modification on the microstructure and properties of hypereutectic high chromium cast iron primarily containing 4.0 wt% C and 20.0 wt% Cr was studied by means of optical microscopy, transmission electron microscope, scanning electron microscope, and energy dispersive X-ray spectrometry. The primary M{sub 7}C{sub 3} carbides were refined obviously when cerium was added in the melt. Ce{sub 2}S{sub 3} was found in the primary M{sub 7}C{sub 3} carbides and acted as the heterogeneous substrate of M{sub 7}C{sub 3} carbides. The impact toughness of the specimen modified with 0.5 wt% cerium increased by 50% compared with the specimen without cerium modification. The hardness of the alloy modified with cerium increased slightly compared with the specimen without cerium modification.

  18. Critical indices for reversible gamma-alpha phase transformation in metallic cerium

    Science.gov (United States)

    Soldatova, E. D.; Tkachenko, T. B.

    1980-08-01

    Critical indices for cerium have been determined within the framework of the pseudobinary solution theory along the phase equilibrium curve, the critical isotherm, and the critical isobar. The results obtained verify the validity of relationships proposed by Rushbrook (1963), Griffiths (1965), and Coopersmith (1968). It is concluded that reversible gamma-alpha transformation in metallic cerium is a critical-type transformation, and cerium has a critical point on the phase diagram similar to the critical point of the liquid-vapor system.

  19. Study of cerium diffusion in undoped lithium-6 enriched glass with Rutherford backscattering spectrometry

    Science.gov (United States)

    Zhang, Xiaodong; Moore, Michael E.; Lee, Kyung-Min; Lukosi, Eric D.; Hayward, Jason P.

    2016-07-01

    Undoped lithium-6 enriched glasses coated with pure cerium (99.9%) with a gold protection layer on top were heated at three different temperatures (500, 550, and 600 °C) for varied durations (1, 2, and 4 h). Diffusion profiles of cerium in such glasses were obtained with the conventional Rutherford backscattering technique. Through fitting the diffusion profiles with the thin-film solution of Fick's second law, diffusion coefficients of cerium with different annealing temperatures and durations were solved. Then, the activation energy of cerium for the diffusion process in the studied glasses was found to be 114 kJ/mol with the Arrhenius equation.

  20. Doping of KDP single crystals with cerium: Growth and optical properties

    International Nuclear Information System (INIS)

    The features of doping of KDP crystals with cerium ions and organocerium complexes with alizarin complexon and arsenazo III have been investigated. It is established that 'direct' doping by introducing cerium salts into the initial solution cannot be implemented. The effect of organometallic complexes of cerium on the crystal growth has been studied. Organocerium complexes predominantly enter the prismatic or pyramidal growth sectors. It is shown that the complex arsenazo III + Ce blocks the growth of the prismatic sector. Cerium-doped KDP crystals exhibit a photoluminescence band peaking at the wavelength λmax= 350 nm.

  1. Formation of adduct of cerium (4) thenoyltrifluoroacetonate

    International Nuclear Information System (INIS)

    Adduct formation of thenoyltrifluoroacetonate of Ce(4) [Ce(TTFA)4] with seven nitrogen- and oxygen-containing donor additional ligands is studied using the methods of IR-spectroscopy, derivatography, X-ray phase analysis. The presence of formation of Ce(TTFA)4 adducts with phosphorus-containing additional ligands tributyl phosphate (TBP), trioctylphosphine oxide (TOPO), triphenylphosphine oxide (TPPO); α, α'-dipyridyl (Dipy) and o-phenanthroline (Phen) is established. The adduct Ce(TTFA)4 stable to reduction is formed with Dipy, and in the case of Phen, TBP, TOPO, TPPO in the process of adduct formation the reduction of Ce(4) to Ce(3) takes place

  2. Synthesis and theoretical investigations of the solid solution CeRu(1-x)Ni(x)Al (x = 0.1-0.95) showing cerium valence fluctuations.

    Science.gov (United States)

    Niehaus, Oliver; Rodewald, Ute Ch; Abdala, Paula M; St Touzani, Rachid; Fokwa, Boniface P T; Janka, Oliver

    2014-03-01

    Members of the solid solution series of CeRu(1-x)Ni(x)Al can be obtained directly by arc melting of the elements. The presented compounds with 0.1 ≤ x ≤ 0.85 crystallize in the orthorhombic space group Pnma (No. 62) in the LaNiAl structure type, while for 0.9 ≤ x ≤ 1, the hexagonal ZrNiAl-type structure is found. The orthorhombic members exhibit an anomaly in the trend of the lattice parameters as well as an interesting behavior of the magnetic susceptibility, suggesting that the cerium cations exhibit no local moment. Besides the mixed-valent nature of the cerium cations, valence fluctuations along with a change in the cerium oxidation state depending on the nickel content have been found. The oxidation state has been determined from the magnetic data and additionally by XANES. Density functional theory calculations have identified the shortest Ce-Ru interaction as decisive for the stability of the orthorhombic solid solution. PMID:24528235

  3. Fabrication of mesoporous cerium dioxide films by cathodic electrodeposition.

    Science.gov (United States)

    Kim, Young-Soo; Lee, Jin-Kyu; Ahn, Jae-Hoon; Park, Eun-Kyung; Kim, Gil-Pyo; Baeck, Sung-Hyeon

    2007-11-01

    Mesoporous cerium dioxide (Ceria, CeO2) thin films have been successfully electrodeposited onto ITO-coated glass substrates from an aqueous solution of cerium nitrate using CTAB (Cetyltrimethylammonium Bromide) as a templating agent. The synthesized films underwent detailed characterizations. The crystallinity of synthesized CeO2 film was confirmed by XRD analysis and HR-TEM analysis, and surface morphology was investigated by SEM analysis. The presence of mesoporosity in fabricated films was confirmed by TEM and small angle X-ray analysis. As-synthesized film was observed from XRD analysis and HR-TEM image to have well-crystallized structure of cubic phase CeO2. Transmission electron microscopy and small angle X-ray analysis revealed the presence of uniform mesoporosity with a well-ordered lamellar phase in the CeO2 films electrodeposited with CTAB templating. PMID:18047150

  4. Development of a zinc-cerium redox flow battery

    OpenAIRE

    Leung, P. K.

    2011-01-01

    Redox flow batteries (RFBs) can be used to store energy on the large and medium scale (kW – MW), particularly in applications such as load levelling of electrical power supplies, power quality control application and facilitating renewable energy deployment. In this thesis, the development of a divided and undivided zinc-cerium redox flow battery from its fundamental chemistry in aqueous methanesulfonic acid has been described. This comprehensive investigation has focused on th...

  5. Purification of cerium, neodymium and gadolinium for low background experiments

    OpenAIRE

    Boiko R.S.; Barabash A.S.; Belli P.; Bernabei R.; Cappella F.; Cerulli R.; Danevich F.A.; Incicchitti A.; Laubenstein M.; Mokina V.M.; Nisi S.; Poda D.V.; Polischuk O.G.; Tretyak V.I.

    2014-01-01

    Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150Nd and 160Gd (promising for 0ν2β search), 136Ce (2β+ candidate with one of the highest Q2β). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2β experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical an...

  6. Properties of ceramics based on cerium dioxide with crystalline filaments

    International Nuclear Information System (INIS)

    Problems of the increase of thermal resistance of ceramics on the basis of cerium dioxide with the interduction of filamentous crystals (FC) of CeO2 and MgO have been considered. It is established that FC of MgO and CeO2 are dissolved in the matrix, foAming fine oblong pores, promoting relaxation of thermal strains and preventing crack propagation, which increases the material thermal resistance

  7. Far infrared properties of PbTe doped with cerium

    Energy Technology Data Exchange (ETDEWEB)

    Nikolic, P.M. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia)]. E-mail: nikolic@sanu.ac.yu; Koenig, W. [Max Planck Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 7000 Stuttgart 80 (Germany); Vujatovic, S.S. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Blagojevic, V. [Faculty of Electronic Engineering, University of Belgrade, Bulevar Kralja Aleksandra 73, 11000 Belgrade (Serbia); Lukovic, D. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Savic, S. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Radulovic, K. [Institute of Technical Sciences SASA, Knez Mihailova 35/IV, 11000 Belgrade (Serbia); Urosevic, D. [Mathematical Institute SASA, Knez Mihailova 35/I, 11000 Belgrade (Serbia); Nikolic, M.V. [Center for Multidisciplinary Studies of the University of Belgrade, Kneza Viseslava 1, Belgrade (Serbia)

    2007-05-16

    Single crystal samples of lead telluride doped with cerium were made using the Bridgman method. Far infrared reflectivity spectra in the temperature range from 10 to 300 K are presented. The experimental data were numerically analyzed using a fitting procedure based on the plasmon-phonon interaction model and optical parameters were determined. Two additional local modes were observed at about 138 and 337 cm{sup -1}. The origin of these local vibrational impurity modes was discussed.

  8. Jet formation in cerium metal to examine material strength

    International Nuclear Information System (INIS)

    Examining the evolution of material properties at extreme conditions advances our understanding of numerous high-pressure phenomena from natural events like meteorite impacts to general solid mechanics and fluid flow behavior. Recent advances in synchrotron diagnostics coupled with dynamic compression platforms have introduced new possibilities for examining in-situ, spatially resolved material response with nanosecond time resolution. In this work, we examined jet formation from a Richtmyer-Meshkov instability in cerium initially shocked into a transient, high-pressure phase, and then released to a low-pressure, higher-temperature state. Cerium's rich phase diagram allows us to study the yield stress following a shock induced solid-solid phase transition. X-ray imaging was used to obtain images of jet formation and evolution with 2–3 μm spatial resolution. From these images, an analytic method was used to estimate the post-shock yield stress, and these results were compared to continuum calculations that incorporated an experimentally validated equation-of-state (EOS) for cerium coupled with a deviatoric strength model. Reasonable agreement was observed between the calculations and the data illustrating the sensitivity of jet formation on the yield stress values. The data and analysis shown here provide insight into material strength during dynamic loading which is expected to aid in the development of strength aware multi-phase EOS required to predict the response of matter at extreme conditions

  9. Dissolution of cerium from cerium-based conversion coatings on Al 7075-T6 in 0.1 M NaCl solutions

    International Nuclear Information System (INIS)

    Highlights: ► Dissolution of cerium from cerium-based conversion coatings (CeCCs) on Al 7075-T6. ► Immersion of CeCCs in 0.1 M NaCl showed dissolution only possible at pH ⩽ 2. ► Corrosion protection of CeCCs is not provided by dissolution of cerium species. ► CeCCs corrosion protection mechanism differ from chromate-based conversion coatings. - Abstract: Cerium-based conversion coatings (CeCCs) were immersed in 0.1 M NaCl for ∼500 h over a range of pH (2.0–5.7) to investigate the dissolution of cerium species. Dissolution was detected by UV–vis spectroscopy only in the pH 2 solution. Similar cerium concentrations were detected from the dissolution of as-deposited and phosphate post-treated CeCCs. Solubility diagrams for Ce(OH)3, Ce(OH)4, CeO2, and CePO4 showed that only Ce(OH)3 was soluble in acidic conditions. Although pKsp(CePO4) ≈ pKsp(Ce(OH)3), the dissolution of the post-treated CeCCs was slightly higher than the as-deposited CeCCs. Thus, corrosion protection of CeCCs is not provided solely by dissolution of cerium species.

  10. Study of the chemical environment of cerium in low silica calcium aluminosilicate glasses by extended X-ray absorption fine structure (EXAFS)

    International Nuclear Information System (INIS)

    Full text. Currently, great attention has been given to rare earth doped optical glasses. These elements by having the 4f shell partially filled exhibit a wealth of sharp fluorescent transitions representing almost every region of the visible and near-infrared portions of the electromagnetic spectrum, being of interest in photonics, when embedded in the glass matrix. In addition cerium oxide possess high hardness and stability to high temperatures, and it has been used in industry in different ways such as catalysts, fuel and solar cells, ultraviolet radiation filters, oxygen sensors and in the polishing of materials. In this context, cerium doped low silica calcium aluminosilicate (LSCA) glasses are considered good candidates for solid state laser active medium due to their good mechanical, optical and thermal properties. Recently it was shown that LSCA glasses doped with cerium oxide is a source of emitting white light, which is of technological applications interest. However it is known that increasing the dopant concentration in the glass matrix, an interaction of rare earth ions takes place leading to a closer proximity between the rare earth ions, and thus a reduction in their quantum efficiency. In this work, the local structure of Cerium in LSCA glasses was characterized by Extended X-Ray Absorption Fine Structure Spectroscopy (EXAFS). The EXAFS and XANES measurements were performed in the Ce LIII-edge at the XAS beam line of LNLS facility (Campinas, Brazil) at room temperature. Structural parameters, coordination numbers (N), interatomic distance (R) and degree of disorder (σ2) were obtained from least squares fitting

  11. The developments and challenges of cerium half-cell in zinc–cerium redox flow battery for energy storage

    International Nuclear Information System (INIS)

    Zinc–cerium redox flow batteries (ZCBs) are emerging as a very promising new technology with the potential to store a large amount of energy economically and efficiently, thanking to its highest thermodynamic open-circuit cell voltage among all the currently studied aqueous redox flow batteries. However, there are numerous scientific and technical challenges that must be overcome if this alluring promise is to turn into reality, from designing the battery structure, to optimizing the electrolyte compositions and elucidating the complex chemical reactions that occur during charge and discharge. This review article is the first summary of the most significant developments and challenges of cerium half-cell and the current understanding of their chemistry. We are certain that this review will be of great interest to audience over a broad range, especially in fields of energy storage, electrochemistry, and chemical engineering

  12. Electrochemical behavior of carbon paper on cerium methanesulfonate electrolytes for zinc-cerium flow battery

    International Nuclear Information System (INIS)

    The voltammetric behavior of the Ce(III)/(IV) half-cell reaction in various electrolytes containing 0.6 M Ce was investigated on both pristine and metal-modified carbon paper (CP) electrodes at three different temperatures (25, 40 and 55 °C) in order to find the most favorable electrochemical conditions. The pristine CP displayed robust electrochemical performance for up to 200 repetitive CV cycles while the Pt loaded electrode’s performance was stable for only 70 cycles, even though the latter exhibited a more reversible behavior, moving from a quasi-reversible to a reversible system (Dox. = 4.0 × 10−6 cm2 s−1 and Dred. = 2.5 × 10−6 cm2 s−1). The In and La metal modified electrodes did not show any improvement with regard to the kinetics or reversibility of the reaction. The addition of 1 M H2SO4 to the base electrolyte enhanced the cerium reduction reaction by a factor of 3, (−7.2 × 10−3 A cm−2). The highest exchange current densities (jo) were achieved at 40 °C for the CP-Pt (1 × 10−3 A cm−2) attributable to the presence of the catalytic Pt. Elevated temperatures (40 and 55 °C) improved D and ΔEp. while also the mass transport parameters a) dynamic viscosity (∼1.5 mPa·s) and b) electrolytic conductivity (∼265 mS cm−1) of the Ce(III)/(IV) half-cell reaction. Overall, pristine CP and to a lesser extent CP-Pt demonstrated good stability with prolonged cycling and kinetics comparable with the ones of Pt and Pt based electrodes

  13. Potential of a Hydrometallurgical Recycling Process for Catalysts to Cover the Demand for Critical Metals, Like PGMs and Cerium

    Science.gov (United States)

    Steinlechner, Stefan; Antrekowitsch, Jürgen

    2015-02-01

    The metals from the platinum group are used in many different industries, for example dental, jewelry, and chemicals. Nevertheless, the most important use is based on their catalytic properties. Approximately 50% of platinum and palladium are used as automotive and industrial catalysts. In case of rhodium, an even higher percentage (around 80-90%) is used as an alloying element in the active layer of different catalysts. The high required amount of 300-900 kg of treated ore to obtain approximately 1 g of PGM is responsible for the high prices. On average, the contents in the ore of Pt and Pd are 5-10 times higher than Rh and Ru and around 50 times higher than Ir and Os. Additionally, the regional limitation of ore bodies leads to a strong dependence on mainly South Africa and Russia as PGM suppliers. Based on the strong discrepancy in supply and demand of PGM's around the world, recycling of catalysts is mandatory and meaningful from the ecological and economical point of view. Based on the high prices of PGM, the industry is forced to improve the efficiency of catalysts, which is done by improving the wash coat technology. By using rare-earth elements, like cerium oxide, the surface can be increased and the ability to supply oxygen is secured. As a side effect, cerium as an additional critical element is introduced into the recycling circuit of catalytic converters, forming a further valuable component and forming a major challenge for common pyrometallurgical converter recycling. Therefore, this article introduces a hydrometallurgical process, developed together with Railly&Hill Inc., for PGM as well as cerium recovery from catalytic converters.

  14. Modified cermet fuel electrodes for solid oxide electrochemical cells

    Science.gov (United States)

    Ruka, Roswell J.; Spengler, Charles J.

    1991-01-01

    An exterior porous electrode (10), bonded to a solid oxygen ion conducting electrolyte (13) which is in contact with an interior electrode (14), contains coarse metal particles (12) of nickel and/or cobalt, having diameters from 3 micrometers to 35 micrometers, where the coarse particles are coated with a separate, porous, multiphase layer (17) containing fine metal particles of nickel and/or cobalt (18), having diameters from 0.05 micrometers to 1.75 micrometers and conductive oxide (19) selected from cerium oxide, doped cerium oxide, strontium titanate, doped strontium titanate and mixtures thereof.

  15. Electrodeposition of cerium from fused mixture of CeCl sub(3)+NaCl-KCl

    International Nuclear Information System (INIS)

    Metallic cerium has been prepared by fused salt electrolysis of 30% CeCl sub(3)+ NaCl-KCl (equimolar) mixture, in the temperature ranged 650-850 sup(0)C, in argon atmosphere. The metal nodules were collected from solidified salts bath. Analysis of these nodules has been done and a 97,3% metallic cerium was obtained. (author)

  16. Formation of the cerium orthovanadate CeVO4 : DFT+U study

    Science.gov (United States)

    da Silva, Juarez L. F.; Ganduglia-Pirovano, M. Verónica; Sauer, Joachim

    2007-09-01

    We report density functional theory calculations of the structural, electronic, and thermodynamic properties of cerium orthovanadate ( CeVO4 ) employing the local density approximation (LDA), generalized gradient approximation (GGA-PBE), LDA+U , and GGA-PBE+U functionals. The LDA+U , GGA-PBE+U , LDA, and GGA-PBE equilibrium volumes deviate by -2.4% , +3.6% , -7.4% , and -0.8% , respectively, from experimental results. DFT+U (DFT) predicts an antiferromagnetic (ferromagnetic) insulating (metallic) ground state, which is in agreement with experimental observations. DFT+U yields Ce and V ions in the III+ and V+ oxidation state, respectively. CeVO4 can be obtained by the reaction between Ce2O3 and V2O5 [ (1)/(2)Ce2O3(s)+(1)/(2)V2O5(s)→CeVO4(s) ] under an inert atmosphere, which is described as exoenergetic (∣ΔH0∣=1.6-1.8eV) by all functionals. The reaction (1)/(2)Ce2O3(s)+(1)/(2)V2O5(s)→CeO2(s)+VO2(s) is exoenergetic with ∣ΔH0∣=0.75 , 0.25, 1.70, and 1.24eV for LDA+U , GGA-PBE+U , LDA, and GGA-PBE, respectively. Hence, VV+ is more easily reduced to VIV+ than CeIV+ to CeIII+ , but the difference is small as obtained with DFT+U , PBE+U , in particular. The variation of this reaction energy is due to the different performance of the various approaches for the description of the change in oxidation state of cerium, IV+ to III+ [J. L. F. Da Silva , Phys. Rev. B 75, 045121 (2007)]. The small difference between the VV and CeIV reducibilities may have consequences for the use of CeO2 as support of V2O5 catalysts in selective oxidation.

  17. Separation chemistry and clean technique of cerium(IV):A review

    Institute of Scientific and Technical Information of China (English)

    邹丹; 陈继; 李德谦

    2014-01-01

    The separation method of changeable valence RE element of cerium (Ce) was reviewed in this paper. Solvent extraction is the most effective and efficient method to separate Ce(IV) from RE(III), usually accompanied with fluorine (F) and phosphor (P) from bastnaesite and monazite etc. By roast or wet-air oxidation, Ce(III) of bastnaesite and monazite was oxidized into Ce(IV), and Cyanex923 and [A336][P507] have been investigated to co-extract and recover Ce(IV), F and P from H2SO4 leaching liquor, leading to favorable conditions for the subsequent separation of Th(IV) and RE(III). The interaction of Ce(IV) and F and/or P enhances the roasting, leaching and extraction of Ce(IV) due to increasing of the stability of Ce(IV), and the formation of CeF3 and CePO4 after reductive stripping will benefit the utilization of F and P. For dealing with RE ores of high-content Ce, the clean process of oxidation roasting and Ce(IV)-F separation for Sichuan bastnaesite highlights the advantages of Ce(IV) based clean technique, which firstly demonstrates the comprehensive utilization of Ce(IV), Th(IV), F and RE(III) and prevention of environmental pollution from foun-tainhead. A preliminary flowsheet of two-step oxidation and extraction of Ce(IV) for Bayan Obo mixed ores was further proposed to process the oxidation and extraction of Ce(IV) in presence of both F and P, indicating the possibility of similar effects with clean process of Sichuan bastnaesite. Ce(IV) separation chemistry and clean technique will open up new realms for light RE resources utilization, meeting“Emission Standards of Pollutants from Rare Earths Industry”promulgated by China’s Ministry of Environment Protection (MOP) in 2011.

  18. Piezoelectric and dielectric properties of cerium-modified Aurivillius type K0.5La0.5Bi4Ti4O15 ceramics

    International Nuclear Information System (INIS)

    The Aurivillius type potassium lanthanum bismuth titanate (K0.5La0.5Bi4Ti4O15, KLBT) polycrystalline ceramics with 0.0-1.0 wt.% CeO2 were synthesized using conventional solid-state processing. X-ray diffraction analysis revealed that the cerium-modified KLBT ceramics have a pure four-layer Aurivillius type structure. The effects of cerium oxide on the piezoelectric, ferroelectric and dielectric properties on the KLBT ceramics were investigated. By the cerium modification, the piezoelectric activities of KLBT ceramics were significantly improved and the dielectric loss decreased. The piezoelectric coefficient d33 for the 0.50 wt.% CeO2-modified KLBT was found to be 28 pC N-1, the highest value among the modified KLBT-based piezoceramics. The reason for piezoelectric activities enhancement with Ce modification was given. The dielectric spectroscopy presented that the Curie temperature for all the KLBT ceramics is higher than 400 deg. C

  19. Interactions of NO{sub 2} with activated carbons modified with cerium, lanthanum and sodium chlorides

    Energy Technology Data Exchange (ETDEWEB)

    Kante, Karifala; Deliyanni, Eleni [Department of Chemistry, City College of New York, Graduate School of the City University of New York, 138 St. Convent Avenue, New York, NY 10031 (United States); Bandosz, Teresa J., E-mail: tbandosz@ccny.cuny.edu [Department of Chemistry, City College of New York, Graduate School of the City University of New York, 138 St. Convent Avenue, New York, NY 10031 (United States)

    2009-06-15

    Highly porous wood-based activated carbon was impregnated with cerium, lanthanum and sodium chlorides using incipient impregnation method. On the samples prepared adsorption of NO{sub 2} was carried out from moist (70% humidity) air either with or without the prehumidification. The materials were characterized using adsorption of nitrogen, thermal analysis, FTIR, and potentiometric titration. The results indicated that for all materials a significant amount of NO{sub 2} was reduced to NO and released from the system. In the case of virgin carbons, the NO{sub 2} interacting with the surface along with nitric and nitrous acids formed there in the presence of water significantly increased the acidity of the carbons by the formation of oxygen-containing groups and organic nitrates. On the other hand, when chlorides were present the capacity to interact with nitrogen dioxide increased since the inorganic phase, depending on the nature of metal, bound NO{sub 2} in the forms of nitrates (Ce, La, Na), got oxidized/oxidized carbon surface (for Ce) or contributed to the formation of nitrosyl chloride (for Na).

  20. Effect of ultrasound treatment on the morpho-structural and luminescent characteristics of cerium doped yttrium silicate phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Muresan, L.E., E-mail: laura_muresan2003@yahoo.com [“Raluca Ripan” Institute for Research in Chemistry, Babeş Bolyai University, Fântânele 30, 400294 Cluj-Napoca (Romania); Cadis, A.I.; Perhaita, I. [“Raluca Ripan” Institute for Research in Chemistry, Babeş Bolyai University, Fântânele 30, 400294 Cluj-Napoca (Romania); Silipas, D.T. [National Institute for R& D of Isotopic and Molecular Technologies, Donath 67-103, 400293 Cluj-Napoca (Romania); Tudoran, L. Barbu [Electronic Microscopy Centre, Babeş Bolyai University, Clinicilor 37, 400006 Cluj-Napoca (Romania)

    2015-08-15

    Highlights: • Y{sub 2}SiO{sub 5}:Ce is prepared by gel combustion in ultrasound conditions (US). • Morpho-structural characteristics are revealed based on FTIR, SEM, XRD, BET. • Incorporation of Ce{sup 3+} in X1/X2 type centers depends on preparative conditions. • US treatment increases the luminescent performances up to 151%. - Abstract: Cerium activated yttrium silicate (Y{sub 2}SiO{sub 5}:Ce) phosphors were prepared by gel-combustion, using yttrium–cerium nitrate as oxidizer, aspartic acid as fuel and TEOS as source of silicon. Two modalities for samples preparation were approached namely: the classical gel-combustion and sonication gel-combustion. The ultrasound treatment during the gelling stage has a positive effect on the structural and luminescent characteristics of the final product. Therefore, a well crystallized single X2–Y{sub 2}SiO{sub 5} phase phosphor was obtained at 1200 °C. Based on FT-IR and XRD investigations, conversion of X1 to X2–Y{sub 2}SiO{sub 5} phases is observed as the firing temperature is varied (1100 °C, 1200 °C, 1300 °C 1400 °C). The ultrasound treatment leads to smaller particle size and enhances the luminescent performances up to 151% in comparison with samples prepared by classical way.

  1. The recrystallization and texture of magnesium-zinc-cerium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mackenzie, L.W.F. [Novelis Global Technology Centre, 945 Princess Street, Kingston, Ontario, K7L 5L9 (Canada); Department of Mining and Materials Engineering, McGill University, 3610 University, Montreal, Quebec, H3A 2B2 (Canada)], E-mail: luke.mackenzie@novelis.com; Pekguleryuz, M.O. [Department of Mining and Materials Engineering, McGill University, 3610 University, Montreal, Quebec, H3A 2B2 (Canada)

    2008-09-15

    Optical microscopy, electron backscatter diffraction and X-ray diffraction are employed to characterize the microstructures and textures of as-rolled and annealed Mg-1Zn and Mg-1Zn-xCe. Mg-1Zn exhibited 'basal' textures: the basal poles aligned with the sheet normal direction. With the addition of cerium, the texture was basal when recrystallization was limited; during recrystallization, the basal texture component weakened, to be replaced by a component with basal poles rotated {approx}45 deg. towards the transverse direction. Deformation, recrystallization and texture are discussed.

  2. The recrystallization and texture of magnesium-zinc-cerium alloys

    International Nuclear Information System (INIS)

    Optical microscopy, electron backscatter diffraction and X-ray diffraction are employed to characterize the microstructures and textures of as-rolled and annealed Mg-1Zn and Mg-1Zn-xCe. Mg-1Zn exhibited 'basal' textures: the basal poles aligned with the sheet normal direction. With the addition of cerium, the texture was basal when recrystallization was limited; during recrystallization, the basal texture component weakened, to be replaced by a component with basal poles rotated ∼45 deg. towards the transverse direction. Deformation, recrystallization and texture are discussed

  3. Catalyst for reduction of nitrogen oxides

    Science.gov (United States)

    Ott, Kevin C.

    2010-04-06

    A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

  4. Effects of cerium and manganese on corrosion of Fe–Cr and Fe–Cr–Ni alloys in Ar–20CO2 gas at 818 °C

    International Nuclear Information System (INIS)

    Highlights: •CO2 gas is more corrosive than dry air for Fe–Cr and Fe–Cr–Ni alloys at 818 °C. •Chromia scale grows faster in CO2 than in air. •Cerium has no significant effect on reducing oxidation rate of the alloys in CO2. •Manganese significantly improves oxidation resistance of Fe–20Cr and Fe–20Cr–20Ni alloys in CO2. -- Abstract: Model alloys Fe–9Cr, Fe–20Cr and Fe–20Cr–20Ni (wt.%) with Ce (0.05%, 0.1%) or Mn (1%, 2%) were exposed to Ar–20CO2 gas at 818 °C. Scales on Fe–9Cr alloys consisted of FeO and FeCr2O4, Fe–20Cr–(Ce) alloys formed only Cr2O3, and Fe–20Cr–(Mn) alloys formed Cr2O3 and MnCr2O4. All Fe–20Cr–20Ni alloys formed Fe3O4, FeCr2O4 and FeNi3. Cerium additions had little effects, but additions of 2% Mn significantly improved oxidation resistance of Fe–20Cr and Fe–20Cr–20Ni alloys. Most alloys also carburized. All alloys developed protective chromium-rich oxide scales in air. Different behavior in the two gases is attributed to faster Cr2O3 scaling rates induced by CO2

  5. Hydrothermal synthesis of cerium titanate nanorods and its application in visible light photocatalysis

    International Nuclear Information System (INIS)

    Highlights: • Cerium titanate nanorods have been synthesized by a simple hydrothermal process. • The size of the cerium titanate nanorods can be controlled by growth conditions. • Cerium titanate nanorods exhibit good photocatalytic activities for methyl blue. - Abstract: Cerium titanate nanorods have been prepared via a hydrothermal process using sodium dodecyl sulfate (SDS) as the surfactant. The cerium titanate nanorods have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and ultraviolet–visible (UV–vis) diffuse reflectance spectrum. XRD shows that the nanorods are composed of CeTi21O38 phase. Electron microscopy observations indicate that the nanorods have good single crystalline nature. The diameter and length of the nanorods are about 50–200 nm and 1–2 μm, respectively. Cerium titanate nanorods have a band gap of 2.65 eV. The photocatalytic activities of the nanorods have been investigated by degrading methylene blue (MB) under visible light irradiation. MB solution with the concentration of 10 mg L−1 can be degraded totally with the irradiation time increasing to 240 min. Cerium titanate nanorods exhibit great potential in photocatalytic degradation of MB under visible light irradiation

  6. The solubility of cerium in La2Ti2O7 by DFT + U calculations

    International Nuclear Information System (INIS)

    To investigate the solubility of cerium in La2Ti2O7, the density functional theory plus Hubbard U correction (DFT + U) approach is employed. The geometrical structure, solution energy and electronic structure of La2−yCeyTi2O7 (0 ≤ y ≤ 2) have been analyzed. The results reveal that the La2Ti2O7–Ce2Ti2O7 solid solution exits over the entire range of cerium content. The calculated increase in the O48f positional parameter, x, with increasing cerium content, may indicate the increased radiation resistance. The results of the density of states distribution and the Bader charge for each ion in La2Ti2O7–Ce2Ti2O7 solid solution suggest that cerium exhibits a reduced charge state in the solid solution. - Highlights: • La2Ti2O7–Ce2Ti2O7 solid solution exits over the entire range of cerium content from 0 to 2. • Cerium incorporation in La2Ti2O7 may lead to increased radiation resistance of La2−yCeyTi2O7 (0 ≤ y ≤ 2) . • Cerium in the solid solution of La2−yCeyTi2O7 (0 ≤ y ≤ 2) exhibits a reduced charge state

  7. Novel in situ coordinated cerium salt/acrylonitrile-butadiene rubber composite

    International Nuclear Information System (INIS)

    A novel rubber composite of acrylonitrile-butadiene rubber (NBR) filled with cerium salt particles was vulcanized via in situ coordination for the first time. The resulting materials exhibit good mechanical properties. Curing characteristics analysis, differential scanning calorimetry, X-ray photoelectron spectroscopy, tensile testing, and an equilibrium swelling method were used for the characterization of the composite. The results in this paper indicate that the composite is a kind of elastomer based on the in situ coordination crosslinking interactions between the nitrile groups (–CN) of NBR and cerium ions. The mechanical properties of vulcanized cerium salt/ NBR rubber are altered when changing the sorts of cerium salt. Moreover, these materials show good irradiation resistance because of the introduction of the cerium salt. -- Highlights: ► Cerium salts were firstly used to vulcanize the acrylonitrile-butadiene rubber. ► Cerium salts act as not only crosslink agents but also reinforcing fillers in the matrix. ► These materials show good irradiation resistance and mechanical properties at same time.

  8. Mesoscopic structure of cerium waste loaded hydrated cement by SANS

    International Nuclear Information System (INIS)

    Cementation is one of the most commonly used methods for conditioning radioactive wastes. It provides a cost-effective solution for encapsulation of low and intermediate level radioactive wastes into suitable solid form for long term safety storage. Cerium is used for decontamination of alpha contaminated metallic waste and after this decontamination process, secondary wastes with corrosion products are created, which must be managed properly and cemented for near surface disposal. In the present work, modification of mesoscopic structure in hydrated cement due to addition of simulated cerium waste at different concentrations has been investigated by small-angle neutron scattering (SANS). Structural modifications, in mesoscopic length scale, have been observed. The scattering profiles for three kinds of cement blocks (virgin, 10 g/l and 20 g/l of corrosion product (C.P.) with 4 mm thickness) are shown. Data have been analyzed in the light of polydisperse spherical particles model assuming a log-normal distribution. Widely separated bimodal particle size distributions best represent the present data. Further, it has been observed that the scattering profile obeys power-law (Q-n) behaviour in two domains of Q, which reflects the self-similar/self-affined morphology of the inhomogeneities. Estimated parameters from SANS data are tabulated. A comparison is shown mentioning the value of scattering radius of gyration, exponent values (η) and average particle size for each kind of hydrated cement sample. (author)

  9. Sorption removal of arsenic by cerium-exchanged zeolite P

    International Nuclear Information System (INIS)

    Modification of zeolite P was performed by exchanged of its sodium with cerium(III). The resulting cerium-exchanged zeolite P, (CeZP) did not change in its crystallinity compared to original zeolite. The CeZP was subsequently used to sorb As(V) from aqueous solution. Maximum sorption of As(V) by CeZP occurred at pH range 3-10. In addition, the sorption capacity increased with increasing initial As(V) concentrations. The sorption follows Langmuir model with maximum sorption capacity of 8.72 mg g-1 at 25 deg. C and increased to 23.42 mg g-1 at 90 deg. C, indicating an endothermic process. The arsenic sorption by CeZP was not affected by the present of nitrate, chloride, sulphate, carbonate and bromide but was reduced significantly in the presence of phosphate. This study shows that the as prepared CeZP was found effective for the removal of arsenic from wastewater sample of wood treatment industry

  10. New sunscreen materials based on amorphous cerium and titanium phosphate

    International Nuclear Information System (INIS)

    Cerium-titanium pyrophosphates Ce1-xTi xP2O7 (with x = 0, 0.50, and 1.0), which are novel phosphate materials developed as UV-shielding agents for use in cosmetics, were characterized by X-ray diffraction, X-ray fluorescent analysis, UV-vis reflectance, and Raman spectroscopy. Since the optical reflectance shifted to lower wavelengths by the crystallization of the phosphates and the stabilization of the amorphous state of the cerium-titanium pyrophosphates was carried out by doping niobium (Nb). Raman spectroscopic study of the phosphate showed that P-O-P bending and stretching modes decreased with the loading of Nb, accompanying with the formation of Nb-O stretching mode. Therefore, the increase in the amount of the non-bridging oxygen in the amorphous phosphate should be the reason for the inhibition of the crystallization. This stabilization is a significant improvement, which enables to apply these amorphous phosphates not only to cosmetics and paints, but also plastics and films

  11. Cerium compounds in the fashion of the light actinides

    International Nuclear Information System (INIS)

    Researchers familiar with the light actinides easily recognize in cerium compounds a microcosm of the rich variety of properties seen in the light actinides. The parallelism seen between comparable cerium and actinide compounds strongly suggests that the same physical models are applicable. The most significant is the relative size of the f-orbital. Localization is generally tighter in Ce compounds than uranium compounds, making Ce roughly analogous to Np through Am. A way to see the actinide parallelism is to compare Hill plots. Compounds in the different regions of the plots (representing different physics) are isostructural compounds with the same companion (B) elements. The most common materials exhibiting a direct f-f interaction are the cubic Laves compounds. Accordingly, we have determined the band structures of CeRu2, CeRh2, CeIr2, CeOs2, and CeNi2. Compounds illustrative of the interaction of f-orbitals with ligand orbitals are the Cu3Au structured materials. Materials calculated in this class are CeRh3, CePd3, and CeSn3 - the materials of much interest as mixed valent. Although the focus is on the Ce compounds, calculations performed on uranium isomorphs are used to highlight the interesting physics

  12. Spectrophotometric determination of Cerium from Monazite Bangka using Tiron reagent

    International Nuclear Information System (INIS)

    To anticipate the analysis of individual rare earth element from monazite processing which have done at PTPBGN division and samples from other division of P2BGN, and to develop the Ce analysis method by spectrophotometric using tiron reagent. The purpose of the experiment is to find out the method and the condition of Ce analysis with high accuracy and applicable. The variable observation were cerium-tiron spectrum, pH, ligand concentration, buffer concentration, linearity, anion influence, limit detection, impurities of elements and complex stability. The complex of cerium-tiron produce the maximum absorption at 497.5 nm and stable until 8 hours. The optimum conditions of this method was : tiron concentration is 0.25 %, pH 8.5 with buffer solution sodium acetate is 0.3 M. Detection limit is 1.00 ppm and area of linearity between 1 - 100 ppm, and PO4, Fe, U and Ti was influence to this method. The content of Ce from 2 samples of monazite Bangka which determine by this method was 18%

  13. The van Hemmen-Kondo model for disordered cerium systems

    International Nuclear Information System (INIS)

    The interplay between disorder and strong correlations has been observed experimentally in disordered cerium alloys such as Ce(Ni, Cu) or Ce(Pd, Rh). In the case of Ce(Ni, Cu) alloys with a Cu concentration x between 0.6 and 0.3, the first studies have shown a smooth transition with decreasing temperature from a spin glass phase to ferromagnetism; for x smaller than 0.2, a Kondo phase has been observed. The situation is more complicated now due to the recent observation of magnetic clusters. The competition between the Kondo effect, the spin glass (SG) and the ferromagnetic (FE) ordering has been extensively studied theoretically. The Kondo effect is described by the usual mean-field approximation; we have treated the SG behavior successively by the Sherrington-Kirkpatrick model, then by the Mattis model and finally by the van Hemmen model, which takes both a ferromagnetic part and a site-disorder random part for the intersite exchange interaction. We present here the results obtained by the van Hemmen-Kondo model: for a large Kondo exchange JK, a Kondo phase is obtained while, for smaller JK, the succession of an SG phase, a mixed SG-FE one and finally an FE one has been obtained with decreasing temperature. This model improves the theoretical description of disordered Kondo systems by providing a simpler approach for further calculations of magnetic clusters and can, therefore, account for recent experimental data on disordered cerium systems.

  14. New sunscreen materials based on amorphous cerium and titanium phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Masui, Toshiyuki [Department of Applied Chemistry, Faculty of Engineering and Handai Frontier Research Center, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Hirai, Hidekazu [Department of Applied Chemistry, Faculty of Engineering and Handai Frontier Research Center, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan); Imanaka, Nobuhito [Department of Applied Chemistry, Faculty of Engineering and Handai Frontier Research Center, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)]. E-mail: imanaka@chem.eng.osaka-u.ac.jp; Adachi, Gin-ya [Juri Institute for Environmental Science and Chemistry, College of Analytical Chemistry, 2-1-8 Temma, Kita-ku, Osaka 530-0043 (Japan)

    2006-02-09

    Cerium-titanium pyrophosphates Ce{sub 1-x}Ti {sub x}P{sub 2}O{sub 7} (with x = 0, 0.50, and 1.0), which are novel phosphate materials developed as UV-shielding agents for use in cosmetics, were characterized by X-ray diffraction, X-ray fluorescent analysis, UV-vis reflectance, and Raman spectroscopy. Since the optical reflectance shifted to lower wavelengths by the crystallization of the phosphates and the stabilization of the amorphous state of the cerium-titanium pyrophosphates was carried out by doping niobium (Nb). Raman spectroscopic study of the phosphate showed that P-O-P bending and stretching modes decreased with the loading of Nb, accompanying with the formation of Nb-O stretching mode. Therefore, the increase in the amount of the non-bridging oxygen in the amorphous phosphate should be the reason for the inhibition of the crystallization. This stabilization is a significant improvement, which enables to apply these amorphous phosphates not only to cosmetics and paints, but also plastics and films.

  15. Kinetic aspects of the behavior of a continuous electrolyzer dedicated to actinides and lanthanides oxidation applied to their separation

    International Nuclear Information System (INIS)

    As part of SESAME developments, a continuous electrochemical reactor has been tested for the in-line oxidation of various species as americium, ruthenium or cerium. The cerium(III) case has been chosen as a model to develop a predictive kinetic modeling of the reactor performances for oxidations. The optimal effect of an oxidation mediator may be described and the importance of some parameters was pointed out like the residence time, the anode material and the concentrations ratio between the substrate to oxidize and the mediator. This modeling will be extrapolated to the optimal electrolyzer design for the americium oxidation in the presence of lacunary heteropolyanions. (authors)

  16. Stabilized tin-oxide-based oxidation/reduction catalysts

    Science.gov (United States)

    Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony Neal (Inventor); Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor)

    2008-01-01

    The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.

  17. [Ion chromatography of L-ascorbic acid, sulfite and thiosulfate using their postcolumn reactions with cerium (IV) and fluorescence detection of cerium (III)].

    Science.gov (United States)

    Chen, Q; Hu, K; Miura, Y

    1999-09-01

    An ion chromatographic method was used to separate the species of L-ascorbic acid, sulfite and thiosulfate in their mixtures. This method is based on the separation of each anion in their mixtures by using a separation column, and then on the fluorimetric measurement of cerium (III) formed by a postcolumn reaction of cerium (IV) with the species of L-ascorbic acid, sulfite and thiosulfate in the effluent. The optimal conditions for separating and determining the above three species have been established. By using a 3 mmol/L carbonate eluent, the species of L-ascorbic acid, sulfite and thiosulfate could be eluted at the proper retention times of 1.7, 2.6 and 5.0 min, respectively, and these three anions could be separated completely. The effects of the concentrations of cerium (IV) and sulfuric acid in the postcolumn reaction solution on the chromatographic peak-height were tested in order to obtain the optimal peak-height. It was found that the peak-height at first increases rapidly with an increase in the concentration of cerium (IV) and sulfuric acid respectively up to a certain concertation, then increases slowly. These critical concentrations of cerium (IV) and sulfuric acid also depend on the amount of the analyte injected. Meanwhile the baseline signals of the sepectra increase with an increase in the concentration of cerium (IV). Some concentrations above the critical concentration of sulfuric acid could be selected as the optimal concentration of sulfuric acid, but the concentration of cerium (IV) should be optimized by establishing a compromise between the higher peak-height and the lower baseline signal. The detection limit of this method was found to be 1 mumol/L for thiosulfate when an amount of 100 microL analyte was injected. PMID:12552889

  18. Structural, topographical and electrical properties of cerium doped strontium barium niobate (Ce:SBN60) ceramics

    Science.gov (United States)

    Raj, S. Gokul; Mathivanan, V.; Kumar, G. Ramesh; Yathavan, S.; Mohan, R.

    2016-05-01

    Tungsten bronze type cerium doped strontium barium niobate (Ce:SBN - Sr0.6B0.4Nb2O6) ceramics were synthesized by solid state process. Cerium was used as dopant to improve its electrical properties. Influence of Ce+ ions on the photoluminescence properties was investigated in detail. The grain size topographical behavior of SBN powders and their associated abnormal grain growth (AGG) were completely analyzed through SEM studies. Finally dielectric, measurement discusses about the broad phase transition observed due to cerium dopant The results were discussed in detail.

  19. Effect of Cerium on Mechanical Properties and Morphology of ZZn4-1 Alloy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Effect of the addition of cerium in appropriate amount on the mechanical properties and morphology of ZZn4-1 alloy was investigated. In the case of samples collected from metal mould, the results show that the addition of cerium in appropriate amount can increase tensile strength and HB hardness, and can refine the microstructure of ZZn4-1 alloy considerably. In the case of samples collected from pressure die-casting, the addition of cerium in appropriate amount can refine the primary η-phase and the eutectic structure of pressure die-casting and improve mechanical and processing properties of the alloy.

  20. Ion exchange reactions in amorphous and crystalline aluminium silicates from solution of cerium salts

    International Nuclear Information System (INIS)

    Reactions of ion-exchange of Na+ by Ce3+ and NH4+ on the zeolite containing catalyst, amorphous silica alumina and zeolite Y have been studied. The cerium cations are shown to be exchanged by the Na+ cations with more selectivity than the anmonia cations. In the case of the zeolite containing catalyst and amorphous silica alumina the region of the staggered ion-exchange from the mixture of the solutions of cerium and ammonium sulphates was been detected. This is explained by the formation fo cerium complexes with the sulphate ions

  1. Reinforcement of natural rubber latex with silica modified by cerium oxide:preparation and properties

    Institute of Scientific and Technical Information of China (English)

    张福全; 廖禄生; 王永周; 汪月琼; 黄红海; 李普旺; 彭政; 曾日中

    2016-01-01

    Variable masses of nano cerium oxide (CeO2) were added into nano silica (SiO2) to prepare the well-dispersed SiO2-CeO2 suspension (SiO2-CeO2), cetyltrimethyl ammonium bromide (CTAB) was used to adjust the compatibility of SiO2-CeO2 with rubber matrix, then SiO2-CeO2 modified by CTAB and curing formulas were mixed with fresh natural rubber (NR) latex to prepare NR/SiO2-CeO2 nanocomposites that contained 0–10 parts of CeO2 by a new emulsion compounding method. The morphologies, cure characteristics, mechanical properties and thermal-oxidative stability of NR/SiO2-CeO2 nanocomposites were investigated. The re-sults revealed that the presence of CeO2 in NR/SiO2-CeO2nanocomposites was favorable for enhancing the interaction between NR matrix and fillers, helped to get smaller SiO2-CeO2 particles with narrower particle size distribution, further improved the crosslink densities and mechanical properties of NR/SiO2-CeO2 nanocomposites vulcanizates. Meanwhile, the addition of CeO2 increased the active energy at least 4.66%, obviously improved the thermal-oxidative aging-inhibiting properties of NR/SiO2-CeO2 nanocomposites. Additionally, nanocomposites containing CeO2 promotedTg shift to high temperature direction, causing the nanocomposites featured higher tanδ at 0 ºC and lower tanδ at 60 ºC and exhibited comparable wet grip and lower rolling resistance when NR/SiO2-CeO2nano-composites were used in tire tread compound.

  2. Stability constants and rate constants of intramolecular redox decomposition of cerium(IV) complexes with some polyatomic alcohols

    International Nuclear Information System (INIS)

    The complex formation and redox decomposition of several hydroxo complexes that form in the Ce4+ - SO42- - R(OH)m systems, where R(OH)m (m = 3, 5, 6) is glycerol, xylitol, and sorbitol, respectively, were studied spectrophotometrically, pH metrically, and kinetically at the ionic strength I = 2 with the pH of the sulfate background in the range of 1.7-3.4 and temperatures of 20.0-23.0 deg C. The stability constants of the [CeOHHxL]3-x (L = R(OH)m) complexes, the ligand speciation, and the rate constants of the intramolecular redox decomposition of the complexes were determined in the sulfate background. The apparent stabilization of the +4 oxidation state of cerium in the specified complexes is demonstrated

  3. Novel cerium doped glass-reinforced hydroxyapatite with antibacterial and osteoconductive properties for bone tissue regeneration.

    Science.gov (United States)

    Morais, D S; Fernandes, S; Gomes, P S; Fernandes, M H; Sampaio, P; Ferraz, M P; Santos, J D; Lopes, M A; Sooraj Hussain, N

    2015-09-01

    The aim of this work was to develop a bioactive bone substitute with an effective antibacterial ability based on a cerium (Ce) doped glass-reinforced hydroxyapatite (GR-HA) composite. Developed composites were physicochemically characterized, using x-ray diffraction (XRD) analysis, SEM, energy dispersive x-ray spectroscopy (EDS), and flexural bending strength (FBS) tests. X-ray photoelectron spectroscopy (XPS) analysis was performed to analyze the oxidation state of Ce in the prepared doped glass. The antimicrobial activity of the composites was evaluated against Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa; whether the cytocompatibility profile was assayed with human osteoblastic-like cells (Mg-63 cell line). The results revealed that the Ce inclusion in the GR-HA matrix induced the antimicrobial ability of the composite. In addition, Ce-doped materials reported an adequate biological behavior following seeding of osteoblastic populations, by inducing cell adhesion and proliferation. Developed materials were also found to enhance the expression of osteoblastic-related genes. Overall, the developed GR-HA_Ce composite is a prospective candidate to be used within the clinical scenario with a successful performance due to the effective antibacterial properties and capability of enhancing the osteoblastic cell response. PMID:26391473

  4. Effects of cerium and vanadium on the activity and selectivity of MnOx-TiO2 catalyst for low-temperature NH3-SCR

    Institute of Scientific and Technical Information of China (English)

    WU Xiaodong; SI Zhichun; LI Guo; WENG Duan; MA Ziran

    2011-01-01

    MnOx-TiO2, CeO2-MnOx-TiO2 and V2O5-MnOx-TiO2 catalysts for low-temperature NH3-SCR were prepared by sol-gel method.The results showed that both cerium and vanadium prevented the transformation of anatase TiO2 to the rutile phase. The addition of vanadium oxide induced the segregation of crystalline Mn2O3, which contributed little to low-temperature SCR and ammonia oxidation, from the MnOx-TiO2 solid solutions. However, the selectivity of the V-containing catalyst was almost 100% due to the decreased ammonia consumption and enhanced adsorption capacity of ammonia on Brφnsted acid sites at relatively high temperatures. The electron-donating effect of cerium reduced the Mn4+/Mn3+ ratio to some extent, resulting in a decreased activity for ammonia oxidation. This, in combination with the enhanced ammonia adsorption capacity by Cen+ as additional Lewis acid sites, endowed the Ce-doped catalyst a higher N2 selectivity than MnOx-TiO2 despite the slightly elevated light-off temperature for NO conversion.

  5. Immobilization of simulated radioactive soil waste containing cerium by self-propagating high-temperature synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Xianhe, E-mail: maoxianhe@hotmail.com; Qin, Zhigui; Yuan, Xiaoning; Wang, Chunming; Cai, Xinan; Zhao, Weixia; Zhao, Kang; Yang, Ping; Fan, Xiaoling

    2013-11-15

    A simulated radioactive soil waste containing cerium as an imitator element has been immobilized by a thermite self-propagating high-temperature synthesis (SHS) process. The compositions, structures, and element leaching rates of products with different cerium contents have been characterized. To investigate the influence of iron on the chemical stability of the immobilized products, leaching tests of samples with different iron contents with different leaching solutions were carried out. The results showed that the imitator element cerium mainly forms the crystalline phases CeAl{sub 11}O{sub 18} and Ce{sub 2}SiO{sub 5}. The leaching rate of cerium over a period of 28 days was 10{sup −5}–10{sup −6} g/(m{sup 2} day). Iron in the reactants, the reaction products, and the environment has no significant effect on the chemical stability of the immobilized SHS products.

  6. Immobilization of simulated radioactive soil waste containing cerium by self-propagating high-temperature synthesis

    Science.gov (United States)

    Mao, Xianhe; Qin, Zhigui; Yuan, Xiaoning; Wang, Chunming; Cai, Xinan; Zhao, Weixia; Zhao, Kang; Yang, Ping; Fan, Xiaoling

    2013-11-01

    A simulated radioactive soil waste containing cerium as an imitator element has been immobilized by a thermite self-propagating high-temperature synthesis (SHS) process. The compositions, structures, and element leaching rates of products with different cerium contents have been characterized. To investigate the influence of iron on the chemical stability of the immobilized products, leaching tests of samples with different iron contents with different leaching solutions were carried out. The results showed that the imitator element cerium mainly forms the crystalline phases CeAl11O18 and Ce2SiO5. The leaching rate of cerium over a period of 28 days was 10-5-10-6 g/(m2 day). Iron in the reactants, the reaction products, and the environment has no significant effect on the chemical stability of the immobilized SHS products.

  7. Electroreduction of cerium ions on silver electrode in halide melts at 973 K

    International Nuclear Information System (INIS)

    The mechanism of electroreduction of cerium ions in equimolar KCl-NaCl melt is explored at 973 K. The effect of the anionic composition of the melt on the electroreduction of cerium ions is studied. It is shown that the electrodeposition of cerium metal from halide melts on a silver electrode is the primary electrochemical process that occurs at potentials more positive than those corresponding to the supporting-electrolyte decomposition. The electroreduction of chloride complexes of cerium on a silver electrode in the melt in both steady- and non-steady-state polarization modes at rates below V≤0.5 V/s is controlled by the diffusion delivery; at higher polarization rates, the charge-transfer stage predominates

  8. Electrochemical separation of uranium and cerium in molten LiCl-KCl

    International Nuclear Information System (INIS)

    The electrochemical separation of uranium from cerium in LiCl–KCl eutectic and the electrochemical behavior of Ce(III) were studied. According to the cyclic voltammogram of Ce(III) and the former result of U(III), electrodeposition potential was determined at -1.65 V (vs Ag/AgCl). The uranium metal was successfully deposited and separated from cerium. The morphology of deposit and cross section of electrode were investigated by SEM, firstly uranium deposit alloys with stainless steel and forms a thin transition layer, and secondly the uranium metal layer grows from the transition layer. The separation factors of uranium/cerium on different recovery ratios were determined through a series of steps. It was found that the content of cerium in the deposit and separation factors declined with increasing the initial concentration of U3+ in molten salts; the separation factors remained stable at around 20 in different uranium recovery ratios. (author)

  9. Synergistic extraction of uranium (VI), thorium (IV) and cerium (III) by thenoyltri-fluoroacetone and phenanthroline

    International Nuclear Information System (INIS)

    The synergistic extraction of uranium(VI), thorium(IV) and cerium(III) with thenoyltrifluoroacetone (HTTA) and phenanthroline (phen) is studied. The extraction equilibrium constants are calculated and the mechanism of the synergistic extraction has been discussed

  10. The low gas flow rate foam separation of cerium(III) from dilute aqueous solutions

    International Nuclear Information System (INIS)

    Two low gas flow rate foam separation techniques, ion and precipitate flotation, have been investigated for the separation of trivalent cerium from solutions with initial cerium concentrations ranging from 1 x 10-8 to 1 x 10-4M in the pH range of 1.8 to 12 using the anionic collector sodium lauryl sulphate and the cationic surfactant cetyl trymethyl ammonium bromide. In addition to the type of collector, the pH and the cerium ion concentration, and other factors which can affect flotation results, viz. the time period of bubbling, the rate of gas flow, the ageing of both the cerium and the collector ions, the ionic strength, and the concentration of the collector ions have been investigated and optimum conditions have been established. Under optimum conditions removals as high a 98.5% can be achieved. (author)

  11. Cerium-based conversion coatings to improve the corrosion resistance of aluminium alloy 6061-T6

    International Nuclear Information System (INIS)

    Highlights: • Cerium-based conversion coatings. • Cerium salt sources assisted with hydrogen peroxide. • Protective properties of the conversion coating. - Abstract: Cerium-based conversion coatings were deposited on aluminium alloy 6061-T6 by immersion in two cerium salt sources (chloride- and nitrate-based) assisted with hydrogen peroxide (H2O2). The morphology and composition of the coatings were analysed using scanning electron microscopy and energy dispersive X-ray spectroscopy. Electrochemical measurements to assess corrosion behaviour were performed using free corrosion potential, polarisation and electrochemical impedance spectroscopy with a 3% NaCl solution. The influence of H2O2 on the generation of the coating was studied by cyclic voltammetry tests. The protective properties of the coating generated are heavily dependent upon the chelating effect, chaotropic anion, the pH and H2O2 content

  12. Synergistic inhibition of carbon steel corrosion in seawater by cerium chloride and sodium gluconate

    International Nuclear Information System (INIS)

    Highlights: • Significant synergistic effect was determined for cerium and gluconate. • The mixture showed significant corrosion inhibition of carbon steel in seawater. • Predominant anodic inhibition mechanism was observed. • The presence of cerium ions incorporated in the protective layer was confirmed. - Abstract: In this research the effect of cerium (III) chloride heptahydrate (CC) and sodium gluconate (SG) on the corrosion inhibition of carbon steel C45 (1531) in natural seawater has been evaluated using electrochemical methods and scanning electron microscopy (SEM). The results show that substantial corrosion inhibition (94.98%) using CC and SG can be obtained in synergistic manner. Surface analysis confirmed the presence of cerium ions incorporated in the protective layer of carbon steel specimen. SG acts predominantly as anodic inhibitor whereas CC acts as a mixed type inhibitor. Using both inhibitors predominant mechanism of anodic inhibition is observed

  13. Characterization of heavy oxide inorganic scintillator crystals for direct detection of fast neutrons based on inelastic scattering

    OpenAIRE

    Rusiecki, Philip R.

    2015-01-01

    Approved for public release; distribution is unlimited Heavy oxide inorganic scintillators may prove viable in the detection of fast neutrons based on the mechanism of inelastic neutron scattering. A candidate set of crystals incorporating constituents of heavy atomic mass, namely bismuth germinate (BGO), zinc tungstate (ZWO), cadmium tungstate (CWO), lead tungstate (PWO), lutetium-gadolinium orthosilicate activated with cerium (LGSO:Ce) and lutetium-aluminum garnet with cerium (LuAG:Ce), ...

  14. Inhibition of pH fronts in corrosion cells due to the formation of cerium hydroxide

    International Nuclear Information System (INIS)

    The effect of cerium-based corrosion inhibitors on the pH front between the alkaline cathode and acidic anode in corrosion cells has been studied. The cerium component of these inhibitors can affect the pH front since it precipitates in an alkaline environment as cerium hydroxide, which is important since the corrosion inhibition mechanism of the cerium component is a result of its deposition as a highly electrical resistive (passivation) layer on the cathode. It is studied whether the cerium can reach the cathode when fed into the corrosion cell from an external source after the onset of corrosion. To this end a simulation model was set up that includes the Poisson–Nernst–Planck theory to describe ion transport and the Frumkin–Butler–Volmer equation to describe charge transfer at the electrodes. In this model both the self-dissociation of water and the formation of cerium hydroxide are taken into account. To support our findings experimentally a corrosion cell consisting of an aluminum and copper electrode was used, in which the pH fronts were visualized using a pH-indicator. Two types of inhibitors were used; namely, highly soluble CeCl3 and sparsely soluble cerium dibutylphosphate, Ce(dbp)3. The results show that CeCl3 can reduce the size of the alkaline region and reach the cathode to form a passivation layer, whereas the solubility in case of Ce(dbp)3 is too low to supply sufficient amounts of trivalent cerium cations to penetrate the alkaline region. This behavior can be explained by the simulation results, which reveal a threshold for the corrosion inhibitor solubility below which no passivation of the cathode occurs

  15. Construction of heterocyclic structures by trivalent cerium salts promoted bond forming reactions.

    Science.gov (United States)

    Properzi, Roberta; Marcantoni, Enrico

    2014-02-01

    Cerium(III) salts have recently gained increasing attention in the synthetic community, owing to the powerful features that are reviewed in detail in this tutorial. This review reports significant examples of cerium(III) promoted synthesis of heterocyclic structures, initially dealing with the synthesis of five- and six-membered ring nitrogen containing heterocycles, then describing the preparation of their oxygenated analogues and finally discussing the achievement of seven-membered rings and mixed heterocyclic motifs. PMID:24217370

  16. Energy-dispersive X-ray fluorescence analysis of cerium in ferrosilicon

    International Nuclear Information System (INIS)

    The cerium was determined in ferrosilicon samples by energy-dispersive X-ray fluorescence techniques (XRF) techniques, with a secondary target of gadolinium. The methods employed were: comparison and linear regression with reference materials with cerium concentration between 0.4 and 1.0%. The samples were prepared in the form of pellets and the analytical results are reported as an average of five determinations with a confidence limits at 95% probability. (Author)

  17. A chemical cleaning process with Cerium (IV)-sulfuric acid

    International Nuclear Information System (INIS)

    A chemical cleaning process with a high decontamination factor (DF) is requested for decommissioning. Usually, the process should be qualified with the features, such as the feasibility of treating large or complicated form waste, the minimization of secondary waste. Therefore, a powerful technique of redox decontamination process with Ce+4/Ce+3 has been studied at INER. First, the redox of cerium ion with electrolytic method was developed. Two kinds of home-made electrolyzer were used. One is with an ion-exchange membrane, and the other one is with a ceramic separator. Second, factors influencing the decontamination efficiency, such as the concentration of Ce+4, regeneration current density, temperature, acidity of solution were all studied experimentally, and the optimum conditions were specified too. Third, the liquid waste recycling and treatment were developed with electrodialysis and ion-exchange absorption methods. Finally, the hot test was proceeded with the contaminated metals from DCR of nuclear facility. (author)

  18. Extraction behavior of cerium by tetraoctyldiglycolamide from nitric acid solutions

    International Nuclear Information System (INIS)

    The diamide N,N,N',N'-tetraoctyldiglycolamide (TODGA) was synthesized and characterized. The prepared TODGA was applied for extraction of Ce(III) from nitric acid solutions. The equilibrium studies included the dependencies of cerium distribution ratio on nitric acid, TODGA, nitrate ion, hydrogen ion and cerous ion concentrations. Analysis of the results indicates that the main extracted species is Ce(TODGA)2(NO3)3HNO3. The capacity of Ce loading is approximately 45 mmol/L for 0.1 M solution of TODGA in n-hexane. Finally, the thermodynamic parameters were calculated: K (25 deg C) = 3.8 x 103, ΔH = -36.7 ± 1.0 kJ/mol, ΔS = -54.6 ± 3.0 J/K mol, and ΔG = -20.4 ± 0.1 kJ/mol. (author)

  19. Deposition and investigation of lanthanum cerium hexaboride thin films

    Science.gov (United States)

    Kuzanyan, A. S.; Harutyunyan, S. R.; Vardanyan, V. O.; Badalyan, G. R.; Petrosyan, V. A.; Kuzanyan, V. S.; Petrosyan, S. I.; Karapetyan, V. E.; Wood, K. S.; Wu, H.-D.; Gulian, A. M.

    2006-09-01

    Thin films of lanthanum-cerium hexaboride, the promising thermoelectric material for low-temperature applications, are deposited on various substrates by the electron-beam evaporation, pulsed laser deposition and magnetron sputtering. The influence of the deposition conditions on the films X-ray characteristics, composition, microstructure and physical properties, such as the resistivity and Seebeck coefficient, is studied. The preferred (100) orientation of all films is obtained from XRD traces. In the range of 780-800 °C deposition temperature the highest intensity of diffractions peaks and the highest degree of the preferred orientation are observed. The temperature dependence of the resistivity and the Seebeck coefficient of films are investigated in the temperature range of 4-300 K. The features appropriate to Kondo effect in the dependences ρ( T) and S( T) are detected at temperatures below 20 K. Interplay between the value of the Seebeck coefficient, metallic parameters and Kondo scattering of investigated films is discussed.

  20. Modification mechanism of cerium on the Al-18Si alloy

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effect of the rare earth cerium (Ce) on the hypereutectic Al-Si alloy under different casting states have been studied by optical microscope and quantitative image analysis. It is found that the size and the quantity of primary silicon in castings decrease with the increase of added Ce in the melt. Meanwhile primary silicon changes from branched shape to fine facetted shape. Although the modification on eutectic silicon in castings also improves with the increase of added Ce in the melt, the effect of modification on eutectic silicon away from primary silicon is more obvious than that on eutectic silicon close to primary silicon. The modification mechanism was analyzed in detail by means of scanning electron microscope equipped with energy dispersive analysis of X-ray and thermodynamics analysis, which included the analysis on the change in standard Gibbs energy of reaction and reaction equilibrium.